The Standard Electrical Dictionary A Popular Dictionary of Words and Terms Used in the Practice of Electrical Engineering (part 4 of 4)

The Standard Electrical Dictionary A Popular Dictionary of Words and Terms Used in the Practice of Electrical Engineering (part 4 of 4)

Telegraph Pole Brackets. Arms for carrying insulators, which arms are attached to telegraph poles or other support. They vary in style; sometimes they are straight bars of wood gained into and bolted or spiked in place; sometimes they are of iron.

Telegraph, Printing. Various telegraphs have been invented for printing in the ordinary alphabet the messages at the receiving end of the line.

Representative instruments of this class are used for transmitting different market and stock reports to business offices from the exchanges. The type faces are carried on the periphery of a printing wheel, which is rotated like the hand of a dial telegraph, and against whose face a paper riband is pressed whenever the proper letter comes opposite to it. As each letter is printed the paper moves forward the space of one letter. Spacing between words is also provided for. In the recent instruments two lines of letters are printed on the paper one above the other.

In England, and on the continent of Europe, printing instruments have received considerable use for ordinary telegraphic work. Hughes' type printer and Wheatstone's ABC telegraph meet with extensive use there for ordinary transmission.

Telegraph, Quadruplex. Duplex telegraphy is the sending of two messages in opposite directions simultaneously through the same wire. Duplex telegraphy is the sending of two messages simultaneously in the same direction. The two combined constitute quadruplex telegraphy. [SIC]

The system was suggested by Stark of Vienna and Bosscha of Leyden in 1855; the successful problem was solved by Edison in 1874.

The principle is based on the two orders of difference in electric currents; they may vary in strength or in direction. Thus we may have one instrument which works with change of strength of current only, the other with change of direction only. The two can be worked together if the direction of the current can be altered without alteration of strength, and if strength can be altered without alteration of direction. Double current and single current working are so combined that one relay works by one system of currents and another relay by the other system. A current is constantly maintained through the line. The relay operated by change in direction is a simple polarized relay which works by change of direction of current. The relay operated by change in strength is the ordinary unpolarized relay.

516 STANDARD ELECTRICAL DICTIONARY.

For the following description and the cuts illustrating it we are indebted to Preece and Sivewright. The cut shows the arrangement of the apparatus and connections for terminal offices.

"Sufficient table room is provided to seat four clerks. The apparatus is arranged for the two senders to sit together in the centre, the messages to be forwarded being placed between them. The section on the left of the switch Q is known as the 'A' side, that on the right as the 'B' side of the apparatus.

K1 the reversing key, reverses the direction of the current. K2 is a simple key, known as the increment key; it is used simply to increase the strength of the current.

Fig. 320. QUADRUPLEX TELEGRAPH CONNECTIONS.

The way in which the keys K1 and K2 combine their action is shown by Fig. 321. E1 and E2 are the line batteries, the one having two and one-third (2-1/3) the number of cells of the other, so that if E1 be the electro-motive force of the smaller, that of the whole combined battery will be 3.3 E1. The negative pole of E1 is connected to z and z1 of K1 and the positive pole of E2 to a of K2 through a resistance coil s. A wire, called the 'tap' wire, connects the positive pole of E1 and the negative pole of E2 to b of K2. This wire has in it a resistance coil r2. The springs c and c1 of Kl are connected to the lever L of K2. Now, when both keys are at rest, the negative pole of E1 is to line through z, and the positive pole of E1 to earth through b of K2 and c of K1; the positive pole of E2 being insulated at a of K2.

517 STANDARD ELECTRICAL DICTIONARY.

There is thus a weak negative current flowing to line. When K1 alone is worked, the current of E1 is reversed. When K2 is worked alone, c of K1 is transferred from b to a, and the strength of the negative current going to line is increased through the increase of the electro-motive force from E1 to 3.3 E1 for the whole battery is brought into play. When K1 and K2 are depressed together, then the negative pole of E1 goes to earth through Z1; and the positive pole of E2 to line through a of K2 and c1 of K1 and a positive current, due to the whole electro-motive force 3.3 E1 goes to line. Hence the effect of working K1 is simply to reverse the current, whatever its strength, while that of K2 is to strengthen it, whatever its direction.

The resistance coil s, of 100° resistance, is called a spark coil, because it prevents the high electro-motive force of the whole battery from damaging the points of contact by sparking or forming an arc across when signals are sent; and the resistance r2 is made approximately equal to the combined resistance of E2 and the spark coil, so that the total resistance of the circuit may not be altered by the working of the apparatus.

Fig. 321. QUADRUPLEX TELEGRAPH.

A1 and B1 (Fig. 320) are the relays which are used to respond to the changes in the currents sent by the keys K1 and K2 at the distant station.

A, is a simple polarized relay wound differentially, each wire having a resistance of 200 [omega], and so connected up as to respond to the working of the reversing key K1 of the distant station. It acts independently of the strength of the current, and is therefore not affected by the working of the increment key K2. It is connected up so as to complete the local circuit of the sounder S1 and the local battery l1 and forms the receiving portion of the 'A' side.

B, is a non-polarized relay also wound differentially, each coil having a resistance of 200 [omega]. It responds only to an increase in the strength of the current, and therefore only to the working of the increment key K2 of the distant station.

[Transcriber's note: In current usage upper case omega indicates ohms and lower case omega denotes angular frequency, 2*PI*f.]

518 STANDARD ELECTRICAL DICTIONARY.

The relay spring is so adjusted that the armatures are not actuated by the weak current sent from E by the key K1.

In its normal position this relay completes the circuit of the local battery through the sounder S. This sounder S, called the uprighting sounder, acts as a relay to a second sounder, S2, called the reading sounder, which is worked by another local battery, l2. Of course, normally, the armature of S is held down and that of S2 is up, but when the tongue t moves, as it does when the increment key K2 is depressed so as to send the whole current to line, then the current from l is interrupted, and the circuit of l2 is completed by the rising of the armature of S, causing the reading sounder S2 to work. This is the 'B' side.

R is a rheostat for balancing the resistance of the line, as used in duplex working.

C is a condenser used for compensating the static charge of the line. It is provided with an adjustable retardation coil, R1, to prolong the effect of the compensating current from the condenser.

G is a differential galvanometer, used for testing, and for facilitating adjustment and balancing.

Q is a switch for putting the line to earth, either for balancing, or for any other purpose. There is on the earth wire leading from Q a resistance coil, r1, equalling approximately the resistance of the whole battery, 3.3 E1, and the resistance s.

The connections shown in Fig. 321, are for an 'up' office. At a 'down' office it is necessary to reverse the wires on the two lower terminals of the galvanometer and the two battery wires on the reversing key K1.

The keys K1 and K2 are, for repeaters, replaced by transmitters.

The adjustment of this apparatus requires great care and great accuracy. Its good working depends essentially on technical skill that can only be acquired by patience and perseverance.

Faults in working generally arise from careless adjustments, dirty contacts, loose connections, battery failures, and the ordinary line interruptions, but there are no troubles that are beyond the reach of ordinary skill, and it can be safely said that, within moderate distances, wherever and whenever duplex working is practicable, then quadruplex working is so too."

The above is a typical quadruplex bridge system. There is also a differential system, the full description of which, in addition to what has been given, is outside of the scope of this work.

519 STANDARD ELECTRICAL DICTIONARY.

Telegraph Repeater. An extension of the relay system, adopted for long lines. A repeating station comprises in general terms duplicate repeating apparatus. One set is connected for messages in one direction, the other for messages in the opposite direction. The general operation of a repeating set is as follows. The signals as received actuate a relay which by its local circuit actuates a key, which in ordinary practise would be the sounder, but in the repeater its lever opens and closes a circuit comprising a battery and a further section of the line.

Repeaters are placed at intervals along the line. Each repeater repeats the signals received for the next section of line with a new battery. It represents an operator who would receive and repeat the message, except that it works automatically.

The Indo-European line from London to Teheran, 3,800 miles long, is worked directly without any hand retransmission, it being carried out by five repeaters. This gives an average of over 500 miles for each repeater. [Transcriber's note: … 650 miles for each repeater.]

Repeaters introduce retardation, and each repeater involves a reduction in the rate of working. Yet in many cases they increase the speed of a line greatly, as its speed is about equal to that of its worst section, which may be far greater than that of the whole line in one.

Synonym--Translater.

Telegraph Signal. In the telegraph alphabet, a dot, or dash; the signal or effect produced by one closing of the circuit. A dash is equal in length to three dots. The space between signals is equal to one dot; the space between letters to three dots; and the space between words to six dots.

Telegraph, Single Needle. A telegraph system in which the code is transmitted by the movements of a needle shaped index which oscillates to right and left, the left hand deflection corresponding to dots, the right hand deflection to dashes. The instruments for sending and receiving are combined into one. The needles are virtually the indexes of vertical galvanometers. In one form by a tapper key (see Tapper), in another form by a key worked by a drop-handle (the drop handle instrument), currents of opposite directions are sent down the line. These pass through both instruments, affecting both needles and causing them to swing to right or left, as the operator moves his key.

As galvanometer needle or actuating needle a soft iron needle is employed, which is polarized by the proximity of two permanent magnets. This avoids danger of reversal of polarity from lightning, a trouble incident to the old system.

520 STANDARD ELECTRICAL DICTIONARY.

The cut, Fig. 322, shows a single needle telegraph instrument of the tapper form. The action of the tapper can be understood from the next cut.

Fig. 322. SINGLE NEEDLE TELEGRAPH INSTRUMENT, DOUBLE TAPPER FORM.

Fig. 323. DOUBLE TAPPER KEY FOR SINGLE NEEDLE TELEGRAPH.

C and Z are two strips of metal to which the positive and negative poles of the battery are respectively connected. E and L are two metallic springs; E is connected to earth, L is connected to the line; at rest both press against Z. If L is depressed so as to touch C, the current from the battery goes to the line by the key L, goes through the coils of the distant instrument and deflects the needle to one side, and then goes to the earth. If the key E is depressed, L retaining its normal position, the direction of the current is reversed, for the other pole of the battery is connected to the earth and the reverse current going through the coils of the distant instrument deflects the galvanometer needle to the other side.

In the drop-handle type an analogous form of commutator worked by a single handle produces the same effects.

521 STANDARD ELECTRICAL DICTIONARY.

Telegraph, Wheatstone, A. B. C. A magneto-electric telegraph of the dial system. An alternating current magneto-generator is turned by hand and by depressing keys its current is admitted to or cut off from the line and receiver's instrument. The message is received by a dial instrument working by the escapement motion described under Telegraph, Dial.

Telegraph, Writing. A telegraph in which the message is received in written characters. The transmitter includes a stylus which is held in the hand and whose point bears against the upper end of a vertical rod. The rod is susceptible of oscillation in all directions, having at its base a spring support equivalent to a universal joint.

The stylus is moved about in the shape of letters. As it does this it throws a series of resistances in and out of the circuit.

At the receiving end of the line the instrument for recording the message includes two electro-magnets with their cores at right angles to each other and their faces near together at the point of the angle. An armature is supported between the faces and through it a vertical rod carried by a spring at its bottom rises. These magnets receive current proportional to the resistances cut in and out by the motions of the other rod at the transmitting end of the line. These resistances are arranged in two series at right angles to each other, one for each magnet. Thus the movements of the transmitting stylus and rod are repeated by the end of the rod in the receiving instrument. A species of pen is carried at the end of the rod of the receiving instrument, which marks the letters upon a riband of paper which is fed beneath it.

Telemanometer. Electric. A pressure gauge with electric attachment for indicating or recording its indications at a distance.

It is applicable to steam boilers, so as to give the steam pressure in any desired place.

Telemeter, Electric. An apparatus for electrically indicating or recording at a distance the indications of any instrument such as a pressure gauge, barometer or thermometer, or for similar work. The telemanometer applied to a boiler comes into this class of instrument.

Telephotography. The transmission of pictures by the electric current, the requisite changes in the current being effected by the action of light upon selenium. The picture is projected by a magic lantern. Its projection is traversed by a selenium resistance through which the current passes. This is moved systematically over its entire area, thus constituting the transmitter, and synchronously with the motion of the selenium a contact point at the other end of the line moves systematically over a sheet of chemically prepared paper. The paper, which may be saturated with a solution of potassium ferrocyanide and ammonium nitrate, is stained by the passage of the current, and by the variation in intensity of staining, which variation is due to variations in the current, produced by the effects of the light upon the selenium, the picture is reproduced.

522 STANDARD ELECTRICAL DICTIONARY.

Telepherage. An electric transportation system, hitherto only used for the carrying of ore, freight, etc. Its characteristic feature is that the electric conductors, suspended from poles, supply the way on which carriages provided with electric motors run. The motors take their current directly from the conductors.

There are two conducting lines, running parallel with each other, supported at the opposite ends of transverse brackets on a row of supporting poles. At each pole the lines cross over so that right line alternates with left, between consecutive pairs of poles.

The cars are suspended from pulleys running on one or the other of the conductors. A train of such cars are connected and the current is taken in near one end and leaves near the other end of the train. These current connections are so distant, their distance being regulated by the length of the train, that they are, for all but an instant at the time of passing each of the poles, in connection with segments of the line which are of opposite potential. To carry out this principle the distance between contacts is equal to the distance between poles. Owing to the crossing over of the lines the contacts are in connection as described and thereby the actuating current is caused to go through the motors.

Cars running in one direction go on the electric conductors on the one side, those running in the other direction go on the other conductor.

A great many refinements have been introduced, but the system has been very little used.

Telephone. An instrument for the transmission of articulate speech by the electric current. The current is defined as of the undulatory type. (See Current, Undulatory.)

The cut shows what may be termed the fundamental telephone circuit. A line wire is shown terminating in ground plates and with a telephone in circuit at each end. The latter consists of a magnet N S with a coil of insulated wire H surrounding one end. Facing the pole of the magnet is a soft iron diaphragm D, held in a frame or mouthpiece T. Any change of current in the line affects the magnetism of the magnet, causing it to attract the diaphragm more or less. The magnet and diaphragm really constitute a little electric motor, the diaphragm vibrating back and forth through an exceedingly short range, for changes in the magnetic attraction.

The principle of the reversibility of the dynamo applies here. If the magnet is subjected to no change in magnetism, and if the diaphragm is moved or vibrated in front of its poles, currents will be induced in the wire bobbin which surrounds its end. If two such magnets with bobbins and diaphragms are arranged as shown, vibrations imparted to one diaphragm will send currents through the line which, affecting the magnetism of the distant magnet, will cause its diaphragm to vibrate in exact accordance with the motions of the first or motor diaphragm. In the combination one telephone represents a dynamo, the other a motor.

If the vibrations of the diaphragm are imparted by the voice, the voice with all its modulations will be reproduced by the telephone at the distant end of the line.

523 STANDARD ELECTRICAL DICTIONARY.

Fig. 324. DIAGRAM OF BELL TELEPHONES AND LINE WITH EARTH CONNECTIONS.

Fig. 325. SECTION OF BELL TELEPHONE.

The above gives the essential features of the Bell telephone. In practice the telephone is used only as the receiver. As transmitter a microphone is employed. To give the current a battery, generally of the open circuit type, is used, and the current in the line is an induced or secondary one.

The microphone which is talked to, and which is the seat of the current variations which reproduce original sound, is termed the transmitter, the telephone in which the sounds are produced at the distant end of the line is termed the receiver.

Fig. 325 shows the construction of the Bell telephone in universal use in this country as the receiver. M is a bar magnet, in a case L L. B B is a bobbin or coil of insulated wire surrounding one end of the magnet. D is the diaphragm of soft iron plate (ferrotype metal), and E is the mouthpiece. The terminals of the coil B B connect with the binding screws C C. The wire in the coil is No. 36, A. W. G., and is wound to a resistance of about 80 ohms.

524 STANDARD ELECTRICAL DICTIONARY.

As typical transmitter the Blake instrument may be cited. It is a carbon microphone. It is shown in section in the cut; a is the mouthpiece and e is a diaphragm of iron plate, although other substances could be used; f is a steel spring, with a platinum contact piece at its end. One end bears against the diaphragm, the other against a carbon block k. The latter is carried by a brass block p, and pressure is maintained between these contacts by the spring g and weight of the piece c, which by gravity tends to press all together. The current passes by way of the spring f, carbon button k and spring g through the circuit indicated.

A battery is in circuit with these parts. If a telephone is also in circuit, and the transmitter is spoken against, the diaphragm vibrating affects the resistance of the carbon-platinum contact, without even breaking the contact, and the telephone reproduces the sound. The heavy piece of metal C acts by its inertia to prevent breaking of the contact. The position of this piece c, which is carried by the brass plate m, is adjusted by the screw n.

Fig. 326. SECTION OF BLAKE TRANSMITTER.

In practice the transmitter and battery are usually on a local circuit, which includes the primary of an induction coil. The line and distant receiving telephone are in circuit with the secondary of the induction coil, without any battery.

Telephone, Bi-. A pair of telephones carried at the ends of a curved bar or spring so that they fit the head of a person using them. One telephone is held against each ear without the use of the hands.

525 STANDARD ELECTRICAL DICTIONARY.

Telephone, Capillary. A telephone utilizing electro-capillarity for the production of telephonic effects. The following describes the invention of Antoine Breguet.

The point of a glass tube, drawn out at its lower end to a capillary opening dips vertically into a vessel. This vessel is partly filled with mercury, over which is a layer of dilute sulphuric acid. The end of the immersed tube dips into the acid, but does not reach the mercury. One line contact is with mercury in the tube, the other with the mercury in the vessel. The arrangement of tube and vessel is duplicated, giving one set for each end of the line. On introducing a battery in the circuit the level of the mercury is affected by electro-capillarity. The tubes are closed by plates or diaphragms at their tops, so as to enclose a column of air. It is evident that the pressure of this air will depend upon the level of the mercury in the tube, and this depends on the electro-motive force. On speaking against the diaphragm the sound waves affect the air pressure, and consequently the level, enough to cause potential differences which reproduce the sound in the other instrument.

Fig. 327. BREGURT'S CAPILLARY TELEPHONE.

Telephone, Carbon. A telephone transmitter based on the use of carbon as a material whose resistance is varied by the degree of pressure brought to bear upon it. Undoubtedly the surface contact between the carbon and the other conducting material has much to do with the action. Many carbon telephones have been invented. Under Telephone the Blake transmitter is described, which is a carbon telephone transmitter. The Edison carbon transmitter is shown in section in the cut. E is the mouth piece and D the diaphragm. I is a carbon disc with adjusting screw V. A platinum plate B B, with ivory button b, is attached to the upper surface of the carbon disc. C C is an insulating ring. The wire connections shown bring the disc into circuit. It is connected like a Blake transmitter. It is now but little used.

Fig. 328. SECTION OF EDISON CARBON TRANSMITTER.

526 STANDARD ELECTRICAL DICTIONARY.

Telephone, Chemical. A telephone utilizing chemical or electrolytic action in transmitting or receiving. The electro-motograph is an example of a chemical receiver. (See Electro-motograph.)

Telephone, Electrostatic. A telephone utilizing electrostatic disturbances for reproduction of the voice. In the cut D and C are highly charged electrophori. The diaphragms A and B when spoken to affect the potential of the electrophorus so as to produce current variations which will reproduce the sound. Dolbear and others have invented other forms of transmitters based on electrostatic action. Receivers have also been constructed. A simple condenser may be made to reproduce sound by being connected with a powerful telephone current.

Fig. 329. DIAGRAM OF EDISON'S ELECTROSTATIC TELEPHONE.

Telephone Induction Coil. The induction coil used in telephone circuits for inducing current on the main line. It is simply a small coil wound with two separate circuits of insulated wire. In the Edison telephone the primary coil, in circuit with the transmitter, is of No. 18 to 24 wire and of 3 to 4 ohms resistance. The secondary in circuit with the line and receiving instrument is of No. 36 wire and of 250 ohms resistance. The Bell telephone induction coil has its primary of No. 18 to 24 wire wound to a resistance of 1/2 ohm, and its secondary of No. 36 wire, and of 80 ohms resistance.

527 STANDARD ELECTRICAL DICTIONARY.

Telephone, Reaction. A form of telephone containing two coils of insulated wire, one of which is mounted on the disc, and the other on the magnet pole in the usual way. These coils react upon each other so as to strengthen the effect.

Telephone, Thermo-electric. A telephone transmitter including a thermo-electric battery, placed in circuit with the line. A plate of vulcanite faces it. When the sound waves strike the vulcanite they move it backward and forward. These movements, owing to the elasticity of the vulcanite, produce minute changes of temperature in it, which affecting the thermo-electric pile produce in the circuit currents, which passing through a Bell telephone cause it to speak. This type of instrument has never been adopted in practice.

Telephote. An apparatus for transmitting pictures electrically, the properties of selenium being utilized for the purpose.

Synonym--Pherope.

Teleseme. An annunciator, displaying on a dial the object wanted by the person using it. It is employed to transmit messages from rooms in a hotel to the office, or for similar functions.

Tele-thermometer. A thermometer with electric attachment for indicating or recording its indications at a distance.

Tempering, Electric. A process of tempering metals by electrically produced heat. The article is made part of an electric circuit. The current passing through it heats it, thereby tempering it. For wire the process can be made continuous. The wire is fed from one roll to another, and if required one roll may be immersed in a liquid bath or the wire between the rolls may be led therein. The current is brought to one roll and goes through the wire to the other. As it does this the wire is constantly fed from one roll to another. The bath may be used as described to cool it after the heating. The amount of heating may be regulated by the rate of motion of the wire.

528 STANDARD ELECTRICAL DICTIONARY.

Ten, Powers of. This adjunct to calculations has become almost indispensable in working with units of the C. G. S. system. It consists in using some power of 10 as a multiplier which may be called the factor. The number multiplied may be called the characteristic. The following are the general principles.

The power of 10 is shown by an exponent which indicates the number of ciphers in the multiplier. Thus 10^2 indicates 100; 10^3 indicates 1,000 and so on.

The exponent, if positive, denotes an integral number, as shown in the preceding paragraph. The exponent, if negative, denotes the reciprocal of the indicated power of 10. Thus 10^-2 indicates 1/100; 10^-3 indicates 1/1000 and so on.

The compound numbers based on these are reduced by multiplication or division to simple expressions. Thus: 3.14 X 10^7 = 3.14 X 10,000,000 = 31,400,000. 3.14 X 10^-7 = 3.14/10,000,000 or 314/1000000000. Regard must be paid to the decimal point as is done here.

To add two or more expressions in this notation if the exponents of the factors are alike in all respects, add the characteristics and preserve the same factor. Thus:

(51X 10^6) + (54 X 10^6) = 105 X 10^6. (9.1 X 10^-9) + (8.7 X 10^-9) = 17.8 X 10^-9.

To subtract one such expression from another, subtract the characteristics and preserve the same factor. Thus:

(54 X 10^6) - (51 X 10^6) = 3 X 10^6.

If the factors have different exponents of the same sign the factor or factors of larger exponent must be reduced to the smaller exponent, by factoring. The characteristic of the expression thus treated is multiplied by the odd factor. This gives a new expression whose characteristic is added to the other, and the factor of smaller exponent is preserved for both,

Thus: (5 X 10^7) + (5 X10^9) = (5 X 10^7) + (5 X 100 X 10^7) = 505 X 10^7.

The same applies to subtraction. Thus: (5 X 10^9) - (5 X 10^7) = (5 X 100 X 10^7) - (5 X 10^7) = 495 X 10^7.

If the factors differ in sign, it is generally best to leave the addition or subtraction to be simply expressed. However, by following the above rule, it can be done. Thus:

Add 5 X 10^-2 and 5 X 10^3. 5 X 10^3 = 5 X 10^5 X 10^-2 (5 X 10^5 X 10^-2) + (5 X 10^-2) = 500005 X 10^-2

This may be reduced to a fraction 500000/100 = 5000.05.

To multiply add the exponents of the factors, for the new factor, and multiply the characteristics for a new characteristic. The exponents must be added algebraically; that is, if of different signs the numerically smaller one is subtracted from the other one, and its sign is given the new exponent.

Thus; (25 X 10^6) X (9 X 10^8) = 225 X 10^14. (29 X 10^ -8) X (11 X 10^7) = 319 X 10^-1 (9 X 10^8) X (98 X 10^2) = 882 X 10^1

529 STANDARD ELECTRICAL DICTIONARY.

To divide, subtract (algebraically) the exponent of the divisor from that of the dividend for the exponent of the new factor, and divide the characteristics one by the other for the new characteristic. Algebraic subtraction is effected by changing the sign of the subtrahend, subtracting the numerically smaller number from the larger, and giving the result the sign of the larger number. (Thus to subtract 7 from 5 proceed thus; 5 - 7 = -2.)

Thus; (25 X 10^6) / (5 X 10^8) = 5 X 10^-2 (28 X 10^-8) / (5 X 10^3) = 5.6 X 10^-11

[Transcriber's note: I have replaced ordinary exponential notation by the more compact and simpler "programming" representation. The last two example would be: 25E6 / 5E8 = 5E-2 28E-8 / 5E3 = 5.6E-11 ]

Tension. Electro-motive force or potential difference in a current system is often thus termed. It is to be distinguished from intensity or current strength, which word it too greatly resembles.

Tension, Electric. (a) The condition an electrified body is brought into by electrification, when each molecule repels its neighbor. The condition is described as one of self-repulsion.

(b) The voltage or potential difference of a circuit is also thus termed.

Terminal. The end of any open electric circuit, or of any electric apparatus; as the terminals of a circuit, dynamo, or battery.

Terminal Pole. In telegraph line construction the last pole of a series; one beyond which the line is not carried. Such pole, as the pull of the wires is all in one direction, requires special staying or support. The regular line poles are free from this strain, as the wire pulls in both directions.

Tetanus, Acoustic. A term in electro-therapeutics. An effect produced on a nerve by very rapidly alternating induced currents. The currents are produced by an induction coil with a vibrator giving a musical note. This is a species of gauge of proper frequency of alternations.

Theatrophone. An apparatus worked by automatic paying machinery by which a telephone connection is made with a theatre or opera by the deposition of a coin in a slot.

Therm. A unit of heat. It has been proposed by the British Association and amounts to a redefinition of the smaller calorie. It is the amount of heat required to raise the temperature of one gram of water one degree centigrade, starting at the temperature of maximum density of water.

530 STANDARD ELECTRICAL DICTIONARY.

Thermaesthesiometer. An electro-therapeutic instrument for testing the sensitiveness of the surface of the body to changes of temperature. Vessels of mercury are provided with thermometers to indicate their temperature. One vessel is surrounded by an electric conductor wound in a number of turns. The temperature is raised by passing a current through this. By successive applications of the vessels to the same spot upon the skin the power of differentiating temperatures is determined.

Thermo Call. (a) An electric alarm or call bell operated by thermo-electric currents. It may serve as a fire alarm or heat indicator, always bearing in mind the fact that differential heat is the requisite in a thermo-electric couple.

(b) See Thermo-electric Call.

Thermo-chemical Battery. A voltaic battery in which the electro-motive force is generated by chemical action induced by heat.

The chemical used generally is sodium nitrate or potassium nitrate. The positive plate is carbon. On heating the battery the nitrate attacks the carbon, burning it and produces potential difference. For negative plate some metal unattacked by the nitrate may be employed.

Fig. 330. POUILLET'S THERMO-ELECTRIC BATTERY.

Thermo-electric Battery or Pile. A number of thermo-electric couples q. v., connected generally in series.

In Nobili's pile the metals are bismuth and antimony; paper bands covered with varnish are used to insulate where required. In Becquerel's pile copper sulphide (artificial) and German silver, (90 copper, 10 nickel) are the two elements. The artificial copper sulphide is made into slabs 4 inches long, 3/4 inch wide, and 1/2 inch thick (about). Water is used to keep one set of junctions cool, and gas flames to heat the other set. In Fig. 331, c, d represent the binding screws. The couples are mounted on a vertical standard, with adjusting socket and screw B, so that its lower end can be immersed in cold water, or raised therefrom as desired.

531 STANDARD ELECTRICAL DICTIONARY.

FIG. 331. BECQUEREL'S THERMO-ELECTRIC BATTERIES.

Fig. 332 shows one couple of the battery. S is artificial antimony sulphide; M is German silver; m is a protecting plate of German silver to save the sulphide from wasting in the flame.

Fig. 332. ELEMENTS OF BECQUEREL'S THERMOELECTRIC BATTERIES.

Clamond's pile has been used in practical work. The negative element is an alloy of antimony, 2 parts, zinc, 1 part. The positive element is tin plate. Mica in some parts, and a paste of soluble glass and asbestus in other parts are used as insulators. They are built up so as to form a cylinder within which the fire is maintained. The air is relied on to keep the outer junctions cool. The temperature does not exceed 200° C. (392° F.)

Sixty such elements have an electro-motive force of 300 volts and an internal resistance of 1.5 ohms. Such a battery requires the consumption of three cubic feet of gas per hour. (See Currents, Thermo-electric. )

532 STANDARD ELECTRICAL DICTIONARY.

Thermo-electric Call. A thermostat arranged to ring a bell or to give some indication when the temperature rises or falls beyond certain points. It may be a compound bar of brass and steel fixed at one end and free for the rest of its length. Its end comes between two adjustable contacts. As the temperature rises it bends one way (away from the brass side) and, if hot enough, touching a contact gives one signal. If the temperature falls it curves the other way, and if cold enough touches the other contact, giving another signal. (See Thermostat, Electric.)

Thermo-electric Couple. If two dissimilar conductors form adjacent parts of a closed circuit, and their junction is at a different temperature than that of the rest of the circuit, a current will result. Such pair of conductors are called a thermo-electric couple. They may be joined in series so as to produce considerable electro-motive force. (See Thermo-electricity and other titles in thermo-electricity.)

The efficiency of a thermo-electric couple according to the second law of thermo-dynamics is necessarily low--not over 10 per cent.

Thermo-electric Diagram. A diagram indicating the change in potential difference for a fixed difference of temperature between different metals at different temperatures. It is laid out with rectangular co-ordinates. On one axis temperatures are laid off, generally on the axis of abscissas. On the other axis potential differences are marked. Different lines are then drawn, one for each metal, which show the potential difference, say for one degree centigrade difference of temperature between their junctions, produced at the different temperatures marked on the axis of abscissas.

Fig. 333· THERMO-ELECTRIC DIAGRAM, GIVING POTENTIAL DIFFERENCE IN C. G. S. UNITS.

Thus taking copper and iron we find at the temperature 0° C. (32° F.) a difference of one degree C. (1.8° F.) in their junctions will produce a potential difference of 15.98 micro volts, while at 274.5° C. (526.1° F.) the lines cross, and zero difference of potential is indicated. Taking the lead line on the same diagram it crosses the iron line a little above 350° C. (662° F.), indicating that if one junction is heated slightly above and the other is heated slightly below this temperature no potential difference will be produced. Lead and copper lines, on the other hand, diverge more and more as the temperature rises.

533 STANDARD ELECTRICAL DICTIONARY.

Thermo-electric Inversion. The thermo-electric relations of two conductors vary at different temperatures. Sometimes at a definite point they have no electro-motive force and after passing this point the positive plate becomes a negative one and vice versa. This is inversion, or reversal. (See Thermo-electric Diagram.)

Synonym-- Thermo-electric Reversal.

Thermo-electricity. Electric energy, electro-motive force or electrification produced from heat energy by direct conversion. It is generally produced in a circuit composed of two electric conductors of unlike material, which circuit must possess at least two junctions of the unlike substances. By heating one of these to a higher temperature than that of the other, or by maintaining one junction at a different temperature from that of the other a potential difference is created accompanied by an electric current.

In many cases differential application of heat to an identical material will develop potential difference. This effect, the converse of the Thomson effect, is not used to produce currents, as in a closed circuit the potential differences due to differential heating would neutralize each other.

Thermo-electric Junction. A junction between two dissimilar conductors, which when heated or cooled so as to establish a differential temperature, as referred to the temperature of the other junction, produces potential difference and an electric current.

Thermo-electric Pile, Differential. A thermo-electric pile arranged to have opposite faces subjected to different sources of heat to determine the identity or difference of temperature of the two sources of heat. It corresponds in use to a differential air thermometer.

Thermo-electric Power. The coefficient which, multiplying the difference of temperature of the ends of a thermo-electric couple, gives the potential difference, expressed in micro-volts. It has always to be assigned to a mean or average temperature of the junctions, because the potential difference due to a fixed difference of temperature between two metals varies with the average temperature of the two junctions. (See Thermo-electric Diagram.)

For bismuth and antimony at 19.5° C. (67.1° F.) it is 103 microvolts per degree Centigrade (1.8° F.). This means that if one junction is heated to 19° C. and the other to 20° C. (66.2° F. and 68.0° F.) a potential difference of 103 micro-volts will be produced.

The potential difference is approximately proportional to the difference of temperature of the two junctions if such difference is small. Hence for large differences of potential the thermo-electric power coefficient does not apply.

As a differential function it is thus deduced by Sir William Thomson, for expressing the E. M. F. in a thermo-electric circuit: If a circuit is formed of two metals with the junctions at indefinitely near temperatures, t and t + dt, and dE is the E. M. F. of the circuit, then the differential coefficient dE/dt is called the thermo-electric power of the two metals for the temperature t.

534 STANDARD ELECTRICAL DICTIONARY.

Thermo-electric Series. The arrangement of possible thermoelectric elements, q. v., in a table in the order of their relative polarity. Bismuth and antimony form a couple in which when their junction is heated the bismuth acts as the positive or negatively charged element and antimony as the negative or positively charged. Between these two extremes according to Seebeck the series runs as follows:

Antimony, Silver, Copper, Arsenic, Gold, Platinum, Iron, Molybdenum, Palladium, Steel, Tin, Cobalt, Cadmium, Lead, Nickel, Tungsten, Mercury, Bismuth. Zinc, Manganese,

A differential temperature of 1° C. (1.8° F.) in a bismuth-antimony couple maintains a potential difference of 103 micro-volts.

Matthiessen gives a different series; it is arranged in two columns; the first column has positive coefficients annexed the second has negative. On subtracting the greater one from the lesser, which, if the two elements are in different columns, of course amounts to adding after changing the negative sign, the relative potential difference due to the combination is obtained. + - Bismuth 25 Gas Coke 0.1 Cobalt 9 Zinc 0.2 Potassium 5.5 Cadmium 0.3 Nickel 5 Strontium 2.0 Sodium 3. Arsenic 3.8 Lead 1.03 Iron 5.2 Tin 1 Red Phosphorous 9.6 Copper 1 Antimony 9.8 Silver 1 Tellurium 179.9 Platinum 0.7 Selenium 290

Thus the relative E. M. F. of a bismuth-nickel couple, as both are in the + column, would be 25 - 5 = 20; that of a cobalt-iron couple, one being in the + column the other in the - column, would be 9 + 5.2 = 14.2. Alloys are not always intermediate to their constituents, and small amounts of impurities affect the results largely. This may account for the discrepancies of different observers. Other compounds could be introduced into the series.

Artificial silver sulphide has been used by Becquerel in a thermo-electric battery.

535 STANDARD ELECTRICAL DICTIONARY.

Thermo-electric Thermometer. A species of differential thermometer. It consists of two thermo-electric junctions connected in opposition with a galvanometer in the circuit. Any inequality of temperature in the two ends or junctions produces a current shown by the galvanometer. It may be used to determine the temperature of a distant place, one of the junctions being located there and the other being under control of the operator. If the latter junction is heated until no current is produced its temperature is evidently equal to that of the distant couple or junction. The heating may be done with hot water or mercury, or other melted metal. The temperature of the water, or other substance, gives the temperature of the distant place.

Thermolysis. Decomposition by heat; dissociation. All compound bodies are decomposable by heat if it is intense enough. Hence at very elevated temperatures there can be no combustion.

Synonym--Dissociation.

Thermometer. An instrument for indicating the intensity of heat. Three scales of degrees of heat are used in practise, the Fahrenheit, Réamur, and Centigrade, each of which is described under its own title. (See Zero, Thermometric-Zero, Absolute.) The ordinary thermometer depends on the expansion of mercury; in some cases alcohol is used. Besides these the compound bar principle as used in the thermostat (see Thermostat, Electric) is employed.

Thermometer, Electric. (a) A thermometer whose indications are due to the change of resistance in conductors with change of temperature. Two exactly similar resistance coils maybe electrically balanced against each other. On exposing one to a source of heat, its resistance will change and it will disturb the balance. The balance is restored by heating the other coil in a vessel of water when the temperature of the water gives the temperature of both coils. The coils are enclosed in water-tight metallic cases.

Synonym--Electric Resistance Thermometer.

(b) A differential thermometer may be made by connecting with a pair of conductors, two thermo-electric couples in opposition to each other, and including a galvanometer in series. On heating the junction of one couple more than that of the other a current at once goes through the galvanometer.

(c) (See Thermometer, Kinnersley's.)

Synonym--Thermo-electrometer.

536 STANDARD ELECTRICAL DICTIONARY.

Fig. 334. KINNERSLEY'S THERMOMETER.

Thermometer, Kinnersley's. A thermo-electrometer. A large glass tube is mounted on a standard and communicates with a small tube parallel to it. Water is poured in so as to rise in the small tube. Two wires terminating in bulbs enter the large tube by its top and bottom. The upper wire can be adjusted by moving up and down through a stuffing box. On discharging a Leyden jar through the space between the knobs on the two wires the water for a moment rises in the small tube. There is little or no accuracy in the instrument. It is allied to the electric mortar (see Mortar, Electric) as a demonstrative apparatus.

Synonyms--Electric Thermometer--Thermo-electrometer.

Thermo-multiplier. A thermo-electric battery including a number of couples. The term is generally applied to a small battery with its similar junctions facing in one direction and used for repeating Melloni's experiments on radiant energy, or so-called radiant heat.

537 STANDARD ELECTRICAL DICTIONARY.

Thermophone. An apparatus for reproducing sounds telephonically by the agency of heat; a receiving telephone actuated by heat. Thus a wire may be attached to the centre of a diaphragm and kept in tension therefrom, and the transmitting telephone current may be caused to pass through it. The wire changes in temperature and consequently in length with the pulses of current going through it and vibrates the diaphragm, reproducing the sound. It is to be distinguished from the thermo-electric telephone which involves the action of potential difference produced by thermo-electric action.

Thermostat, Electric. A thermostat or apparatus, similar to a thermometer in some cases, for closing an electric circuit when heated. It is used in connection with automatic fire alarms to give warning of fire. For this use a temperature of 52° C. (125° F.) is an approved one for setting one at, to complete the circuit. It is also applied to regulation of temperature, as in incubators.

(a) One kind of thermostat consists of a compound bar wound into a spiral and fastened at one end, to which a terminal of a circuit is connected. The bar may be made of two strips of brass and iron riveted together, and wound into a spiral. When such a bar is submitted to changes of temperature it bends in different directions, because brass expands and contracts more under changes of temperature than does iron. A contact point, to which the other terminal is connected, is arranged to make contact with the spiral at any desired degree of temperature, thus closing an electric circuit and ringing a bell, opening or closing a damper, or doing anything else to notify an attendant or to directly change the temperature.

If the brass forms the outside of the spiral, increase of temperature makes the bending of the spiral bring the coils still closer. If the brass forms the inside, increase of temperature makes the spiral tend to become less close. As shown in the cut, the brass should lie along the inside of the spiral.

Sometimes a straight compound bar is used, one of whose ends is fastened and the other is free. As the temperature changes such a bar curves more or less, its free end moving to and fro. Two contact screws are provided, one on each side of its free end. If the temperature falls it makes contact with one of these; if the temperature rises, it makes contact with the other. Thus it may close one of two circuits, one for a fall and the other for a rise in temperature.

It is well to introduce a third bar between the brass and iron ones, made of some material of intermediate coefficient of expansion.

(b) Another kind of thermostat comprises a vessel of air or other gas, which, expanding by heat, actuates a piston or other device and closes an electric circuit. Synonym--Electro-pneumatic Thermostat.

(c) Another form utilizes the expansion of mercury. The mercury is made part of an open electric circuit. As it expands it comes in contact with the other terminal of the circuit, thus completing it, when the current gives an alarm or does as is provided for in the apparatus employed.

Thermostats may be worked on either open or closed circuits; normally the circuit may be open as described and may close on rise of temperature, or it may be normally closed and open as the temperature rises.

Fig. 335. ELECTRIC THERMOSTAT.

538 STANDARD ELECTRICAL DICTIONARY.

Thomson Effect. In an unequally heated conductor the differential heating is either increased as in iron, or diminished as in copper by a current. In lead the phenomenon does not occur. It is termed the Thomson effect. It is intimately related to the Peltier effect.

In a thermo-electric couple a heated junction is the source of electro-motive force, if heated more than other parts of the circuit. The current in a copper-iron junction flows from the copper to the iron across the heated junction. A hot section of an iron conductor next to a cold section of the same is a source of thermoelectricity, in the sense that the hot section is negative to the colder. A current passing from the hot to the cold iron travels against rising potentials, and cools the iron in the cooler parts. As it passes to the hotter parts it travels against falling potentials and hence heats the iron in these parts. In this way a current intensifies differential heating in an iron conductor.

In copper the reverse obtains. In it the thermo-electric relations of hot and cold copper are the reverse of those of iron, and a current tends to bring all parts of a differentially heated copper conductor to an identical temperature.

As a current travels in iron from hot to cold it absorbs heat; in copper traveling from cold to hot it absorbs heat.

The convection of heat by a current of electricity in unequally heated iron is negative, for it is opposed to that convection of heat which would be brought about by the flow of water through an unequally heated tube. In copper, on the other hand, the electric convection of heat is positive. (Daniell.)

The above effects of the electric current upon an unequally heated conductor are termed the Thomson effects. In iron, at low red heat, they are reversed and are probably again reversed at higher temperatures.

539 STANDARD ELECTRICAL DICTIONARY.

Three Wire System. A system of distribution of electric current for multiple arc or constant potential service. It is the invention of Thomas A. Edison.

It includes three main wires which start from the central station or generating plant, and ramify with corresponding reduction in size, everywhere through the district or building to be lighted. As ordinarily carried out when dynamos are used, the dynamos are arranged in groups of two. One lateral lead starts from the negative binding post of one dynamo. The positive terminal of this dynamo connects to the negative of the other. Between the two dynamos the central or neutral lead is connected. The other lateral lead starts from the positive binding post of the second dynamo.

The lamps or other appliances are calculated for the potential difference of a single dynamo. They are arranged between the neutral wire and the laterals, giving as even a disposition as possible to the two laterals.

Fig. 336. DIAGRAM OF THREE WIRE SYSTEM SHOWING NEUTRAL WIRE.

If evenly arranged and all burning or using current, no current goes through the neutral wire. If all the lamps situated on one lateral are on open circuit all the current goes through the neutral wire. In other cases the neutral wire receives the excess of current only.

The advantages of the system are that it uses smaller wire than the two wire system for lamps of the same voltage. If lamps of double the voltage were used the two wire system would be most economical.

540 STANDARD ELECTRICAL DICTIONARY.

Four wire and five wire systems have been more or less used, based on identical considerations, and involving in each case the coupling of three or of four dynamos respectively, or else employing a dynamo with special armature connections to give the requisite three-fold or four-fold division of total potential. In the five wire system the total voltage is four times that of a single lamp, the lamps are arranged four in series across the leads and the central wire is the only one that can be considered a neutral wire. When lamps are burning entirely from three side-leads they constitute a sort of three wire system by themselves, and their central wire may for the time be a neutral wire.

In some of the three wire mains, especially in the larger sizes, the neutral wire is made of much smaller section than that of a lateral conductor, because in extensive districts it is practically impossible that the current should be concentrated in the neutral wire.

Throw. In a galvanometer the instantaneous deflection of the needle when the contact or closing of the circuit is instantaneous, or when the discharge is completed before the needle begins to move. The throw of the needle is the datum sought when the ballistic galvanometer is used.

Synonym--Elongation.

Throw-back Indicator. A drop annunciator, whose shutter or drop is electrically replaced.

Thrust-bearings. Bearings to support the end-thrust or push of a shaft. In disc armatures where the field-magnets attract the armatures in the direction of their axis of rotation, thrust-bearings have to be provided. In ordinary cylinder or drum armatures end-thrust is not applied, as a little end motion to and fro is considered advantageous as causing more even wear of the commutator surface.

Thunder. The violent report which, as we hear it, succeeds the lightning flash in stormy weather. It is really produced simultaneously with the lightning and is supposed to arise from disturbance of the air by the discharge. The rolling noise has been attributed to successive reflections between clouds and earth, and to series of discharges reaching the ear from different distances and through air of varying density. The subject is obscure. By timing the interval from lightning flash to the report of the thunder an approximate estimate of the distance of the seat of discharge can be made. The first sound of the thunder should be timed. An almost concurrence of thunder and lightning indicates immediate proximity of the discharge.

[Transcriber's note: The speed of sound at sea level is about 5 seconds per mile.]

Ticker. A colloquial name for a stock or market report automatic printing telegraph, which prints its quotations and messages on a long tape.

541 STANDARD ELECTRICAL DICTIONARY.

Time Constant. (a) When current is first turned into a circuit of considerable self-induction it is resisted rather by the inductance than by the resistance. It is governed by the ratio of resistance and self-induction and this factor represents the time which it takes for the current to reach a definite fraction of its final strength. This fraction is (2.7183 - 1)/2.7183 or 0.63. 2.7183 is the base of the Napierian system of logarithms. Thus if in any circuit we divide the inductance in henries by the resistance in ohms, the ratio gives the time-constant of the circuit, or it expresses the time which it will take for the current to reach 0.63 of its final value.

(b) In a static condenser the time required for the charge to fall to 1/2.7183th part of its original value.

Time Cut-outs. Cut-outs which automatically cut storage batteries out of the charging circuit when they are sufficiently charged.

Time-fall. In a secondary battery the decrease with use of electromotive force maintained by a primary or secondary battery. As the battery becomes spent its voltage falls. The conditions of the fall are represented by its discharging curve. (See Curve, Discharging.)

Time-reaction. A term in electro-therapeutics; the period of time occupied in the passage of the effects of an electric current from nerve to muscle.

Time-rise. In a secondary battery the increase of electromotive force produced during the charging process. Its rate and conditions are graphically shown in the charging curve. (See Curve, Charging.)

Tin. A metal; one of the elements; symbol, Sn; atomic weight, 117.8; equivalent, 58.9 and 29.5; valency, 2 and 4; specific gravity, 7.3. It is a conductor of electricity.

Relative resistance, compressed, (Silver = 1) 8.784 Specific resistance at 0° C. (32° F.), 13.21 microhms. Resistance of a wire at 0° C. (32° F.), (a) 1 foot long, weighing 1 grain, 1.380 ohms. (b) 1 foot long, 1/1000 inch thick, 79.47 " (c) 1 meter long, weighing 1 gram, .9632 " (d) 1 meter long, 1 millimeter thick, .1682 " Resistance of a 1 inch cube at 0° C. (32° F.), 5.202 microhms. Percentage of variation in resistance per degree C. (1.8° F.), at about 20° C. (68° F.), .0365 Electro-chemical equivalent (hydrogen = .0105), .619 mgs. .310 "

542 STANDARD ELECTRICAL DICTIONARY.

Tinnitus, Telephone. A nervous affection of the ear, of the order of professional cramp; it is attributed to too much use of the telephone.

Tin Sounders. A recent addition to the single needle telegraph. (See Telegraph, Single Needle.) It consists of small tin plates, cut and bent, and so fitted in pairs to the instrument, that the needle as deflected strikes one or the other on its right and left hand movements. The sounders can be made to give sufficiently distinctive sounds to make sound-reading, q. v., possible. Commercial tin plate, which is really tinned iron, seems to give the best results.

Fig. 337. TIN SOUNDERS.

Tissandier's Solution. A solution for bichromate batteries. It is composed as follows: Water, 100 parts by weight potassium bichromate, 16 parts 66° sulphuric acid, 37 parts.

Tongue of Polarized Relay. The German silver extension of the vibrating or oscillating member of a polarized relay, corresponding to the armature of an ordinary relay.

Tongue of Polarized Relay, Bias of. In a Siemens' polarized relay the pole pieces are adjustable so that they may be brought nearer to or withdrawn from the tongue. One of the poles is adjusted so as to be nearer the tongue. This one-sided adjustment is the bias. Its effect is that when the relay is unexcited this pole attracts the armature so that it normally is drawn towards it. This ensures the normal contact of the tongue either with the contact point, or with the insulated stop piece or adjustment screw. Without bias the armature remains in contact with or drawn towards whichever pole it was last attracted to. In its usual use a bias is given it.

Top, Magnetic. A toy illustrating magnetic attraction. It consists of a disc or body of lead or other material, through which a magnetized steel spindle pointed at its lower end is thrust. A number of short pieces of iron wire are used with it. It is spun like an ordinary top upon the point of the spindle and one of the pieces of iron wire is laid by the side of its point. As it turns the magnetic adherence causes the piece of wire to be carried along in one direction by the rotation of the spindle, until the end is reached, when it goes over to the other side of the spindle and travels back again.

By using bent pieces of wire of various shapes the most curious effects are produced. Circles and S shaped pieces give good effects. To increase the mysterious effect covered iron wire (bonnet wire) may be employed.

Fig. 338. MAGNETIC TOP.

543 STANDARD ELECTRICAL DICTIONARY.

Torpedo, Electric. (a) A fish, the Raia Torpedo, which possesses the power of giving electric shocks. (See Ray, Electric.)

(b) An instrument of war; a torpedo whose operations include electrical discharge or other electric function or factor of operation.

Torpedo, Sims-Edison. A torpedo driven by an electric motor, and also steered by electricity. Its motions are all controlled from the shore. The torpedo proper is carried some distance below the surface of the water by a vessel immediately above it, from which it is suspended by two rigid bars. In the torpedo is a cable reel on which the conducting cable is disposed. An electric motor and controlling gear are also contained within the torpedo. In its front the explosive is placed. It is driven by a screw propeller actuated by the electric motor. As it moves it pays out cable so that it has no cable to draw after it through the water, the cable lying stationary in the water behind it. This avoids frictional resistance to its motion. The maintenance of the torpedo at a proper depth is one of the advantages of the system.

544 STANDARD ELECTRICAL DICTIONARY.

Torque. A force tending to produce torsion around an axis. An example is the pulling or turning moment of an armature of an electric motor upon its shaft. It is often expressed as pounds of pull excited at the end of a lever arm one foot long.

The expression is due to Prof. James Thompson, then of the University of Glasgow.

"Just as the Newtonian definition of force is that which produces or tends to produce motion (along a line), so torque may be defined as that which produces or tends to produce torsion (around an axis). It is better to use a term which treats this action as a single definite entity than to use terms like 'couple' and 'moment,' which suggest more complex ideas." (S. P. Thompson.)

A force, acting with radius r gives a torque equal to f X r ; f and r may be expressed in any units. S. P. Thompson gives the following equivalents :

To reduce dyne-centimeters to gram centimeters, divide by 981 dyne-centimeters to meter-kilograms divide by 981E5 dyne-centimeter, to pound-feet divide by 13.56E6 pound-feet to meter-kilograms divide by 7.23

In each of these compound units the first unit is the force and the second unit is the radius or lever arm of the torque.

Synonyms--Turning Moment--Moment of Couple--Axial Couple--Angular Force--Axial Force.

Torsion Balance, Coulomb's. Originally an apparatus in which electrostatic attraction or repulsion is measured against the torsion of a filament, often of silk-worm cocoon fibre. It consists in one form of a cylindrical glass vessel in which a light shellac needle is suspended horizontally by a fibre. This needle carries at one end a gilded disc or sphere and is suspended by a fine wire, or filament. A proof plane, q. v., is excited by touching it to the body under trial; it is then inserted in the case. The disc on the needle is first attracted and then repelled. The position finally taken by the needle is noted. The force of torsion thus produced is determined by twisting the filament by the torsion head on the top of the apparatus so as to move the needle a certain distance towards the proof plane. The more the torsion-head has to be turned to carry the needle through a specified arc the greater is the torsion effected or the greater is the repulsion exerted, The torsional force of a wire is proportional to the angle of torsion; this gives the basis for the measurement.

With magnetic needle it is used to measure magnetic repulsion and attraction. The best material for the filament is quartz, but the instrument is not very much used.

Torsion Galvanometer. A galvanometer in which the torsion required to bring the index back to zero, when the current tends to displace it, is made the measure of the current strength or of the electro-motive force. It involves the use of a torsion head, q. v., or its equivalent.

545 STANDARD ELECTRICAL DICTIONARY.

Torsion Head. The handle and disc from whose undersurface the filament depends to which the needle or magnet is attached. It is turned to measure the torsional effect, the edge of the disc being marked or graduated so as to give the angle of deflection required to overcome the effect of the torque of the needle.

Torsion Suspension. Suspension by one or more wires, fibres, or ribands, involving the restitutive force of torsion. Thus fibre suspension, q. v., is a variety of torsion suspension.

Often a single riband of steel stretched horizontally and secured at both ends is used, the suspended object, e. g., a balance beam, being attached at its own centre to the centre of the stretched riband. Quite sensitive balances are constructed on this principle. It is peculiarly available where an electric current is to be transmitted, as absolute contact is secured, as in William Thomson's ampere balances.

Touch. A term applied to methods of magnetization, as "single touch," "double touch," or "separate touch," indicating how the poles of the inducing magnet or magnets are applied to the bar to be magnetized. Under the titles of Magnetization the different methods are described.

Tourmaline. A mineral; a subsilicate; characterized by the presence of boric trioxide, which replaces aluminum oxide. It is notable for possessing pyro-electric properties. (See Pyro-electricity.)

Tower, Electric. The tower used in the tower system, q. v., of arc light illumination.

Tower System. In electric lighting the system of lighting extended areas by powerful arc lamps placed on high towers, generally of iron or steel frame-work. The lights are thus maintained at a high elevation, giving greater uniformity of illumination than if they were lower, but at the expense of considerable light which is lost. Sometimes wooden masts are employed instead of towers.

The principle involved is that the intensity of light at any place given by a source of illumination varies with the square of its distance from the place in question. Hence in using strong arc lights it is an object to have the distances of all parts of the area illuminated at as nearly uniform distances from the light as possible. An approximation to uniformity is secured by placing the lamps at a very high elevation.

546 STANDARD ELECTRICAL DICTIONARY.

Transformer. In alternate current lighting the induction coil by which the primary current with high initial electro-motive force is caused to produce a secondary current with low initial electromotive force.

A typical transformer consists of a core of thin iron sheets. The primary is of comparatively thin wire and often of ten or more times as many turns as the secondary. The latter is of thicker wire. Where the ratio of 10 to 1 as regards number of turns in the primary and secondary obtains, the initial E. M. F. of the secondary is one-tenth that of the primary circuit.

The cores are laminated, as described, to avoid the formation of Foucault currents.

The counter-electro-motive force of the transformer when the secondary circuit is open, prevents any but the slightest current from passing through the primary. In proportion as the secondary is closed and its resistance diminished, as by lighting more lamps in parallel, the counter-electro-motive force of the transformer falls and more current passes through the primary.

Fig. 339. FERRANTI'S TRANSFORMER.

The economy of the apparatus is in the fact that counter-electromotive force reduces current through a conductor without absorbing any energy. A resistance coil cuts down a current, but absorbs energy equal to the current multiplied by the potential difference between the terminals of the coil. This electric energy is converted into heat energy and is wasted. But the counter-electromotive force of a transformer is exerted to reduce current without production of heat and with little waste of energy. This is one of the advantages of the alternating current system of distribution of electric energy.

The object of a transformer being to secure safety to the person or to life by the separation of the high potential primary or street circuit, and the low potential house circuit, any contact of the two circuits in the converter is a source of danger. Special care should be taken to ensure absence of leakage, as it is termed. Mica or other insulation is sometimes employed to prevent the wires from coming in contact by piercing or sparking with the core and with each other.

547 STANDARD ELECTRICAL DICTIONARY.

Transformer, Commuting. A type of continuous current transformer, resembling a dynamo with armature and field both stationary, but with revolving commutator, by which the magnetic polarity of a double wound armature is made to rotate. This secures the desired action, of a change or lowering of potential.

Transformer, Continuous Alternating. An apparatus for transforming a continuous into an alternating current or the reverse. The combination of a continuous current dynamo with an alternating current one is sometimes employed. It is a form of motor dynamo.

Another type is a regular dynamo with ordinary commutator and with, in addition thereto, two, three or four contact rings, connecting to as many symmetrically disposed points in the winding of the armature. This will give out or receive alternating currents of two, three or four phases according to the number of collecting rings. One winding serves for both alternating and continuous currents.

Transformer, Continuous Current. A machine of the dynamo type for changing the potential of a circuit. In one form two armatures are mounted on one shaft in a single field or in separate fields; one is a motor armature driven by the original current; the other generates the new current. This is a motor dynamo. In 1874 Gramme constructed a machine with ring armature with two windings, of coarse and fine wire respectively, and with independent commutators. Such dynamo could transform currents up or down.

Continuous current transformers have attained an efficiency of 83 per cent. at full load, and of 75 per cent. at half load. Owing to the balancing of the self-inductions of the two windings these machines do not spark. As the driven and driving parts are contained in one rotating part their friction is very slight.

Transformer, Core. A transformer wound upon an enclosed core, such as the hedgehog transformer (see Transformer, Hedgehog), or common induction coil.

548 STANDARD ELECTRICAL DICTIONARY.

Transformer, Hedgehog. An induction coil transformer whose iron core is composed of a bundle of iron wires, which after the wire windings are in place have their ends spread out to reduce to some extent the reluctance of the circuit, which at the best is high, as the air acts as the return circuit.

This transformer has a low degree of hysteresis; and its efficiency for very small loads or for no load is superior to that of the closed magnetic circuit transformer.

Fig. 340. SWINBURNE'S HEDGEHOG TRANSFORMER.

Transformer, Multiple. A transformer connected in parallel with others between the two leads of the primary circuit. The term refers to the connection only and not to any peculiarity of the transformer itself.

Transformer, Oil. A transformer with oil insulation. The advantage of this insulation is that if pierced it at once closes, so that no permanent injury ensues. It is a self-healing form of insulation.

Transformer, Series. Transformers connected in series upon the primary circuits. The term, like "multiple transformers," only applies to the connection, not to the transformer. Series transformers are but little used.

Transformer, Shell. A transformer with its iron core entirely outside of and enclosing the primary and secondary winding. It may be made by the use of outer iron wire windings as core.

Transformer, Welding. The transformer used for electric welding. (See Welding, Electric.) It is a transformer with very long primary and exceedingly short and thick secondary. It is used with the alternating current in the primary, and produces in the secondary circuit which includes the bars to be welded a very low potential difference.

Owing to the very low resistance of the secondary circuit this low electro-motive force produces a very strong current, which develops the requisite heat. The same type of transformer is used for brazing and similar purposes.

549 STANDARD ELECTRICAL DICTIONARY.

Transmitter. In general electric phraseology, any instrument which produces signals to be transmitted through a line or circuit is a transmitter. Thus the Morse key in telegraphy or the Blake transmitter in telephony are examples of such.

Transmitter, Carbon. A form of microphone used as a telephone transmitter. (See Carbon Telephone.)

Transposing. A method of laying metallic circuits for telephoning. The wires at short intervals are crossed so that alternate sections lie on opposite sides of each other. It is done to avoid induction.

Transverse Electro-motive Force. Electro-motive force in a substance in which electric displacement is taking place, produced by a magnetic field. It is sometimes assigned as the cause of the Hall effect, q. v.

Trimmer, Brush. A shears for cutting off evenly and squarely the ends of copper dynamo brushes. The brushes when uneven from wear are removed from the brush holders, and their ends are sheared off in the trimmer.

Trolley. A grooved metallic pulley or set of pulleys which runs along an active wire of a circuit, a lead from which trolley goes to earth or connects with another wire, so that the trolley takes current generally for operating a street car motor placed upon the circuit leading from it; a rolling contact with an electric lead.

Trolleys are principally used on electric railroads, and are now universally of the sub-wire system, being at the end of a pole which is inclined backward and forced upward by springs, so as to press the trolley against the bottom of the wire. Thus the trolley does not increase the sagging of the wire, but tends to push it up a little in its passage.

Trolley, Double. A trolley with two rollers or grooved wheels, placed side by side, and running on two parallel leads of wire. It is adapted to systems employing through metallic trolley lines with the motors in multiple arc, connecting or across the two leads.

Trolley Section. An unbroken or continuous section of trolley wire.

Trouvé's Solution. An acid exciting and depolarizing solution for a zinc-carbon battery. Its formula is as follows: Water, 80 parts; pulverized potassium bichromate, 12 parts; concentrated sulphuric acid, 36 parts; all parts by weight. The pulverized potassium bichromate is added to the water, and the acid is added slowly with constant stirring. As much as 25 parts potassium bichromate may be added to 100 parts of water. The heating produced by the acid and water dissolves nearly all the potassium salt. Use cold.

550 STANDARD ELECTRICAL DICTIONARY.

True Contact Force. A species of electro-motive force whose existence is supposed to be proved by the Peltier effect. The lowering in temperature of a contact of dissimilar metals is attributed to a force that helps the current on its way if in the direction of thermo-current proper to the junction and opposing it if in the reverse. The true contact force is taken to explain this phenomenon; thermo-electric force cannot, as there is no heat or cold applied to the junction.

Trumpet, Electric. An apparatus consisting of a vibrating tongue, kept in motion by electricity as in the buzzer, q. v., placed in the small end of a trumpet-shaped tube.

Trunking Switchboard. A telephone switchboard arranged in sections, which sections are connected by trunk lines, through which trunk lines the desired connections are made.

Trunk Lines. In telephone distribution systems, the lines connecting different stations, or different sections of a switch-board and used by anyone requiring such connections; one trunk line answers for a number of subscribers.

Tube, Electric. A tube of glass around which is pasted a series of tinfoil circles, diamonds, or little squares, or other form of interrupted conductor. The pieces generally are placed in the line of a spiral. When a static discharge of electricity takes place along the conductor a row of bright sparks is produced at the breaks in the conductor. These by reflection are multiplied apparently, and a beautiful effect of intersecting or crossing spirals of sparks is presented.

The experiment is in line with the luminous pane and lightning jar, and is used merely as a demonstration, or lecture experiment.

Synonym--Luminous Tube.

Tubular Braid. A braid woven of tissue or worsted, and tubular or hollow. Its object is to provide a covering which can be drawn over joints in covered wires. In making the joint the ends of the wires are necessarily bared, and a short piece of tubular braid is used for covering them. It is drawn by hand over the joint.

Turns. An expression applied to the convolutions of wire in a solenoid, electro-magnet, or other apparatus or construction of that kind. A turn indicates a complete encircling of the core or axis of the object. Thus a wire wound five times around a bar gives five turns.

While this is its primary meaning the term if compounded may refer to virtual turns. Thus an ampere-turn means one ampere passing through one turn. But ten ampere-turns may mean ten amperes passing through ten turns, five amperes passing through two turns, and so on. This use is analogous to a dimension of length in a compound word, as foot-pound.

[Transcriber's note: "But ten ampere-turns may mean ten amperes passing through ONE turn or one ampere through ten turns, and so on."]

There may be a number of kinds of turns qualified by descriptive adjectives, as series-turns, the turns of wire in a series circuit of a compound dynamo. In the same way there are shunt-turns. If series ampere-turns or shunt ampere-turns are meant the word ampere should be included.

551 STANDARD ELECTRICAL DICTIONARY.

Turns, Dead, of a Dynamo. The rotations of a dynamo armature while it is building itself up or exciting itself. The expression is a bad one, as it is likely to be confounded with the dead turns of armature wire.

Turns, Primary Ampere-. The ampere-turns in a primary circuit of an induction coil or transformer. In an electric welding transformer, or in the transformer used in the alternating current system, where efficiency is an important element, the ampere-turns in primary and secondary for an efficiency of 100 per cent. should be equal. In the case of an experimental induction coil other considerations outweigh that of mere efficiency. Insulation, including security from piercing, and the production of as long a spark as possible, are, in these cases, the controlling consideration.

[Transcriber's note: A 100 per cent efficient transformer is impossible, but over 99 per cent is common. At room temperature there is always some lost flux, eddy currents and resistive losses.]

Turns, Secondary Ampere-. The ampere-turns on the secondary circuit of an induction coil or transformer. These depend on the path provided for the current. If of negligible inductance, such as a number of incandescent lamps would provide, the ampere-turns should be equal to those of the primary coil. (See Turns, Primary Ampere.)

Typewriter, Electric. A typewriter in which the work of printing or of pressing the type faces against the paper, or printing ribbon, is done by electro-magnetic attraction. The keys close electric circuits, throwing the electro-magnetic action into play. This involves the use of electricity for what is ordinarily only a mechanical process. The strength of the impression, however, is independent of the touch of the operator. It has not come into very extensive use.

[Transcriber's note: IBM introduced widely used electric typewriters in 1935.]

Ultra-gaseous Matter. Gas so rarefied that its molecules do not collide or very rarely do so.

Experiments of very striking nature have been devised by Crookes and others to illustrate the peculiar phenomena that this matter presents. The general lines of this work are similar to the methods used in Geissler tube experiments, except that the vacua used are very much higher.

When the vacuum is increased so that but one-millionth of the original gas is left the radiant state is reached. The molecules in their kinetic movements beat back and forth in straight lines without colliding, or with very rare collisions. Their motions can be guided and rendered visible by electrification. A tube or small glass bulb with platinum electrodes sealed in it, is exhausted to the requisite degree and is hermetically sealed by melting the glass. The electrodes are connected to the terminals of an induction coil or other source of high tension electrification. The molecules which come in contact with a negatively electrified pole are repelled from it in directions normal to its surface. They produce different phosphorescent or luminous effects in their mutual collisions.

Thus if they are made to impinge upon glass, diamond or ruby, intense phosphorescence is produced. A piece of platinum subjected to molecular bombardment is brought to white heat. A movable body can be made to move under their effects. Two streams proceeding from one negative pole repel each other. The stream of molecules can be drawn out of their course by a magnet.

The experiments are all done on a small scale in tubes and bulbs, resembling to a certain extent Geissler tubes.

[Transcriber's note: These effects are caused by plasma--ionized gas and electrons.]

552 STANDARD ELECTRICAL DICTIONARY.

Unbuilding. The loss of its charge or excitation by a self-exciting dynamo. It is the reverse of building-up. The latter indicates the exciting of the field by the action of the machine itself; the former the spontaneous loss of charge on open circuit or from other cause.

Underground Conductor. An electric conductor insulated and placed under the surface of the earth, as distinguished from aerial conductors.

Underground Electric Subway. A subway for the enclosing of electric telegraph and other conductors under the surface, generally in the line of streets, to do away with telegraph poles and aerial lines of wire. Many systems have been devised. The general type includes tubes called ducts in sets, called conduits, bedded in concrete or otherwise protected. Every two or three hundred feet the sets lead into a cistern-like cavity called a manhole. The insulated wires or cables, generally sheathed with a lead alloy are introduced into the tubes through the man-holes. A rope is first fed through the tube. To do this short rods which screw together are generally employed. One by one they are introduced, and each end one is screwed to the series of rods already in the duct. When the end of the duct is reached the rope is fastened to the last rod, and the rods are then drawn through, unscrewed one by one and removed, the rope following them. By means of the rope a windlass or capstan may be applied to draw the cable into the duct. At least at every second man-hole the cables have to be spliced.

Each cable may contain a large number of conductors of small size for telephoning, or a smaller number for electric light and power. The tendency is now to separate the different classes of wires in important lines, placing the heavier wires on one side of the street and the telephone and telegraph wires on the other. This of course necessitates two separate conduits.

The advantage of underground distribution affects not only the appearance of streets in doing away with unsightly telegraph poles, but it also removes an element of danger at fires. Aerial wires interfere greatly with the handling of ladders at fires, and expose the firemen who attempt to cut them to danger to their lives from shock.

533 STANDARD ELECTRICAL DICTIONARY.

Unidirectional. adj. Having one direction as a "unidirectional current" or "unidirectional leak." The term is descriptive, and applicable to many cases.

Uniform. adj. Unvarying; as a uniform potential difference, uniform current or conductor of uniform resistance per unit of length. The term is descriptive, and its application and meaning are obvious.

Uniform Field of Force. A field of evenly distributed force; one in which the number of lines of force per unit of area of any equipotential surface is the same.

Unipolar. adj. Strictly speaking this term means having only one pole, and is applied to magnets, armatures and the like. In its use a solecism is involved, for there is no such condition possible as unipolar magnetism or distribution of magnetism. An example of its use is shown in unipolar magnets. (See Magnet, Unipolar.)

Unipolar Armature. An armature of a unipolar dynamo; an armature whose windings continuously cut the lines of force about the one pole, and hence whose polarity is unchanged in its rotation.

Unipolar Current Induction. Current induction produced by moving a conductor through a magnetic field of force so that it always cuts the lines in similar relation to itself. Thus it produces a constant current through its own circuit, if a closed one, and no commutator is required. As this case always in practice amounts to the cutting of lines of force in the neighborhood of a single pole the term unipolar is employed to designate the action.

The simplest representation of unipolar induction is the rotating of a conductor around the end of a bar magnet, its axis of rotation corresponding with the axis of the magnet.

Unipolar Dynamo. A dynamo in which one part of the conductor slides on or around the magnet, so as always to cut lines of force near the same pole of the magnet.

Unit. A directly or indirectly conventional and arbitrary quantity, in terms of which measurements of things with dimensions expressible in the chosen units are executed.

Thus for length the c. g. s. unit is the centimeter; the B. E. unit is the foot.

554 STANDARD ELECTRICAL DICTIONARY.

Unit, Absolute. A unit based on the three fundamental units of length, mass and time. These units are the centimeter, gram and second. Each one in itself may be termed a fundamental absolute unit. The system of such units is termed the centimeter-gram-second system.

Unit, Angle. A factor or datum in angular velocity, q. v. It is the angle subtended by a portion of the circumference equal in length to the radius of the circle. It is equal very nearly to 57.29578° or 57° 17' 44.8".

Unit, B. A. This term, while logically applicable to any of the British Association units, is often restricted to the ohm as formerly defined by the British Association, the B. A. Unit of Resistance, q. v.

Unit, Fundamental. The three units of length, mass and time, the centimeter, gram and second, are termed fundamental units. On them is based the absolute system of units, and on multiples of them the practical system of units.

Unit Jar. A Leyden jar which is used as a unit of measure of charge.

It consists of a Leyden jar about 4 inches long and 3/4 inch diameter, with about 6 square inches of its outer and the same of its inner surface coated with tinfoil. It is placed between a source of electricity and a larger jar or battery of jars which is to be charged. The inner coating connects with the machine; the outer coating with the jars to be charged. Short conductors terminating in knobs connect with inner and outer coatings, and the knobs are adjusted at any desired distance apart.

By the charging operation the large jar or battery of jars receives a charge by induction, and the charge of the small jar is at first equal to this quantity. After a while a spark passes from knob to knob, discharging the small jar. This indicates the reception by the large jars of the quantity of electricity represented by the charge of the small jar. The charging goes on, and for every spark approximately the same quantity of electricity is received by the larger jars.

The sparking distance m is directly proportional to the quantity of electricity, and inversely proportional to the area of coated surface, or is proportional to the potential difference of the two coats. This is only true for short sparking distance, hence for accuracy the knobs should be adjusted not too far from each other.

555 STANDARD ELECTRICAL DICTIONARY.

Unit of Supply. A commercial unit for the sale of electric energy, as defined provisionally by the English Board of Trade; 1,000 amperes flowing for one hour under an E. M. F. of 1 volt; 3,600,000 volt-coulombs, or 1,000 watt-hours, are its equivalent. It is equal to 1000/746 = 1.34 electric horse power.

Synonym--Board of Trade Unit.

[Transcriber's note: Now called a kilowatt-hour.]

Units, Circular. A system of units of cross-sectional area, designed especially for use in describing wire conductors. The cross-sectional area of such is universally a circle, and the areas of two wires of different sizes vary with the square of their radii or diameters. Hence if the area of a circle of known diameter is determined it may be used as a unit for the dimensions of other circles. Any other circle will have an area proportioned to the area of the unit circle, as the squares of the diameters are to each other.

In practise the commonest circular unit is the circular mil. This is the area of a circle one mil, 1/1000 inch, in diameter and is equal to .0000007854 square inch. A wire two mils in diameter has an area of four circular mils; one ten mils in diameter has an area of one hundred circular mils.

Thus if the resistance of a given length of wire 1 mil in diameter is stated, the corresponding resistance of the same length of wire of the same material, but of other diameter, is given by dividing the first wire's resistance by the square of the diameter in mils of the wire in question.

As it is a basic unit, most conveniently applied by multiplication, the smaller units are used; these are the circular mil, and circular millimeter.

Units, Derived. Units derived by compounding or other processes, from the three fundamental units. Such are the units of area, volume, energy and work, momentum and electric units generally. In some cases the dimensions of the derived unit may reduce to those of a simple unit as inductance reduces to length, but the unit, as deduced from the fundamental ones, is still a derived unit.

Units, Practical. A system of units employed in practical computation. The absolute units, especially in electricity, have been found too large or too small, and the attempt to make them more convenient has resulted in this system. It is based on exactly the same considerations as the absolute system of units, except that multiples of the original fundamental units of length, mass, and time have been taken as the base of the new system. These basic units are multiples of the fundamental units. They are the following: The unit of length is 1E9 centimeters; the unit of mass is 1E-11 gram; the unit of time remains 1 second.

While this has conduced to convenience in giving better sized units, micro- and mega-units and other multiples or fractions have to be used. The following are the principal practical electric units:

Electrostatic Electromagnetic C. G. S Units. C. G. S. Units. Intensity-Ampere equal to 3E9 1E-1 Quantity-Coulomb " 3E9 1E-1 Potential-Volt " (1/3)* E-2 1E8 Resistance-Ohm " (1/9)* E-11 1E9 Capacity-Farad " 9E11 1E-9

556 STANDARD ELECTRICAL DICTIONARY.

Universal Battery System. A term in telegraphy. If several equal and high resistance telegraphic circuits are connected in parallel with each other from terminal to terminal of a battery of comparatively low resistance each circuit will receive the same current, and of practically the same strength as if only one circuit was connected. This is termed the universal battery system. It is a practical corollary of Ohm's law. The battery being of very low resistance compared to the lines the joining of several lines in parallel practically diminishes the total resistance of the circuit in proportion to their own number. Thus suppose a battery of ten ohms resistance and ten volts E. M. F. is working a single line of one hundred ohms resistance. The total resistance of the circuit is then one hundred and ten ohms. The total current of the circuit, all of which is received by the one line is 10/110 = .09 ampere, or 90 milliamperes. Now suppose that a second line of identical resistance is connected to the battery in parallel with the first. This reduces the external resistance to fifty ohms, giving a total resistance of the circuit of sixty ohms. The total current of the circuit, all of which is received by the two lines in equal parts, is 10/60 = .166 amperes. But this is equally divided between two lines, so that each one receives .083 ampere or 83 milliamperes; practically the same current as that given by the same battery to the single line. It will be seen that high line resistance and low battery resistance, relatively speaking, are required for the system. For this reason the storage battery is particularly available. The rule is that the resistance of the battery shall be less than the combined resistance of all the circuits worked by it.

Unmarked End. The south-seeking pole of a magnet, so called because the other end, called the marked end, is usually marked with a scratch or notch by the maker, while the south pole is unmarked.

V. (a) Symbol for velocity.

(b) Symbol or abbreviation for volume.

(c) Symbol or abbreviation for volt.

557 STANDARD ELECTRICAL DICTIONARY.

V. A. Symbol or abbreviation for voltaic alternatives, q. v.

Vacuum. A space destitute of any substance. The great pervading substance is in general sense the atmosphere. It is the gaseous mixture which surrounds and envelopes the earth and its inhabitants. It consists of a simple mixture of oxygen, 1 part, nitrogen, 4 parts, with 4 to 6 volumes of carbonic acid gas in 10,000 volumes of air, or about one cubic inch to one cubic foot. It presses with a force of about 14.7 lbs. per square inch under the influence of the force of gravity. The term vacuum in practise refers to any space from which air has been removed. It may be produced chemically. Air may be displaced by carbonic acid gas and the latter may be absorbed by caustic alkali or other chemical. The air may be expelled and the space may be filled with steam which is condensed to produce the vacuum. Of course in all cases the space must be included in an hermetically sealed vessel, such as the bulb of an incandescent lamp. But the universal method of producing a vacuum is by air pumps. An absolute vacuum means the entire absence of gas or air, something almost impossible to produce. A high vacuum is sometimes understood to mean one in which the path of the molecules is equal in length to the diameter of the containing vessels, as in Crookes' Radiometer and other apparatus for illustrating the radiant condition of matter. The air left after exhaustion is termed residual air or residual atmosphere.

[Transcriber's note: Dry air is about .78 nitrogen, .21 oxygen, .01 argon, .00038 carbon dioxide, and trace amounts of other gases. Argon was suspected by Henry Cavendish in 1785. It was discovered in 1894 by Lord Rayleigh and Sir William Ramsay.]

Vacuum, Absolute. A space free of all material substance. It is doubtful whether an absolute vacuum has ever been produced.

Vacuum, High. An approximate vacuum, so nearly perfect that the molecules of the residual gas in their kinetic motions rarely collide, and beat back and forth between the walls of the containing vessel, or between any solid object contained in the vessel and the walls of the vessel. The gas in such a vacuum is in the radiant or ultra-gaseous state. (See Ultra-gaseous Matter.)

Vacuum, Low. A vacuum inferior to a high vacuum; a vacuum in which the molecules collide with each other and do not move directly from side to side of the containing vessel.

Vacuum, Partial. A space partially exhausted of air so as to contain less than an equal volume of the surrounding atmosphere. It really should come below a low vacuum, but is often treated as synonymous therewith.

Vacuum, Torricellian. The vacuum existing above the mercurial column in a barometer tube. The principle of this vacuum is applied in the Geissler and other air pumps. (See Pump, Geissler--Pump, Sprengel--Pump, Swinburne.)

558 STANDARD ELECTRICAL DICTIONARY.

Valency. The relative power of replacing hydrogen or combining therewith possessed by different elements; the number of atomic bonds belonging to any element. Thus oxygen has a twofold valency, is bivalent or is a dyad, and combines with two atoms of hydrogen because the latter has a unitary atomicity, is monovalent or is a monad.

Valve, Electrically Controlled. A valve which is moved by or whose movements are regulated by electricity.

In the block system of railroad signaling the semaphores are worked by weights and pneumatic cylinders and pistons. The valves for admitting or releasing the compressed air are operated by coil and plunger mechanism. There are many other instances of the control of valves by the electric current.

Vapor Globe. A protecting glass globe surrounding an incandescent lamp, when the lamp is to be used in an atmosphere of explosive vapor, as in mines or similar places; or when in a place where it is exposed to dripping water which would break the hot lamp bulb if it fell upon it.

Variable Period. The period of adjustment when a current is started through a conductor of some capacity. It is the period of duration of the variable state, q. v., in a conductor. As indicated in the next definition in a cable of high electrostatic capacity a variable period of nearly two minutes may exist. This indicates the retardation in signaling to be anticipated in cables and other lines of high capacity.

Variable State. When an electric circuit is closed the current starts through the conductor with its full strength from the point of closure, and advances with a species of wave front so that some time elapses before it attains its full strength in the most distant parts of the conductor, owing to its having to charge the conductor to its full capacity at the given potential. The state of the line while the current thus varies is called the variable state.

A long telegraph line when a message is being transmitted may be always in the variable state. The current at the receiving end may never attain its full strength.

In the case of such a conductor as the Atlantic cable, 108 seconds would be required for a current to attain 9/10 of its full strength at the distant end, and but 1/5 second to attain 1/100 of its final value. During the period of increase of current the variable state exists.

Variation of the Compass. The declination of the magnetic needle. (See Elements, Magnetic.) As the declination is subject to daily, annual and secular variations, it is unfortunate that this term is synonymous with declination. Thus the variation of the compass means its declination, while there is also the variation of the declination and of other elements. The term variation of the compass is more colloquial than the more definite expression "declination," or "magnetic declination."

559 STANDARD ELECTRICAL DICTIONARY.

Variometer. An apparatus used in determining the relative values of the horizontal component of the earth's magnetic field in different places.

Varley's Condenser. A static condenser whose conducting surfaces are platinum electrodes immersed in dilute sulphuric acid. When the potential difference is 1/50th that of a Daniell's cell, two square inches of platinum have a capacity equal to that of an air condenser whose plates have an area of 80,000,000 square inches, and separated 1/8th of an inch from each other. As the E. M. F. increases the capacity also increases.

Varley's Resistances. Variable resistances formed of discs of carbonized cloth, q. v., piled up, and pressed together more or less firmly to vary the resistance as desired.

Varnish. A glossy transparent coating of the nature of paint, applied as a protective, or ornamental coating to objects.

Varnish, Electric. Alcoholic or etherial varnishes are the best for electrical apparatus. They dry quickly and perfectly, and tend to form surfaces unfavorable to the hygroscopic collection of water. Sealing wax dissolved in alcohol, or shellac dissolved in the same solvent are used for electrical apparatus, although the first is rather a lacquer than a varnish. Etherial solution of gum-copal is used to agglomerate coils of wire. It is well to bake varnished objects to harden the coating.

Varnish, Red. A solution of sealing wax in 90 per cent. alcohol. It is best made thin and applied in several coats, each coat being allowed to dry perfectly before the next is applied. It is often seen on Leyden jars. It is a protector from surface leakage.

Vat. A vessel for chemical or other solutions. A depositing vat is one in which a plating solution is worked, for the deposition of electroplate upon articles immersed in the liquid, and electrolyzed by an electric current.

Velocity. The rate of motion of a body. It is usually expressed in distance traversed per second of time. The absolute unit is one centimeter per second or kine. The foot per second is very largely used also.

The dimensions of velocity are length (L) divided by time (T) or L/T.

Velocity, Angular. Velocity in a circle defined by the unit angle, or the angle which subtends a circular arc equal in length to itself. The radius of the circle traversed by the moving body does not enter into this definition, as the real velocity of the object is not stated. If its angular velocity and the radius of the path it travels are given its actual velocity can be deduced.

560 STANDARD ELECTRICAL DICTIONARY.

Velocity of Signaling. The speed of transmission of electric signals is affected by the nature of the line, as regards its static capacity, and by the delicacy of the receiving instruments, which may need a more or less strong current to be affected. Thus of an original current one per cent. may suffice to operate a sensitive instrument. This might give almost the velocity of light, while if the instrument would only respond to the full current nearly two minutes (see Variable State) might be required for the production of a signal.

Velocity Ratio. A term applied to the ratios existing between the electrostatic and electro-magnetic units. If we take as numerators the dimensions of the different qualities in the electrostatic system, and their dimensions in the electro-magnetic system as denominators, the fractions thus obtained reduce to expressions containing only velocity or V in some form. Thus if we divide the dimensions of the electrostatic quantity by the dimensions of electro-magnetic quantity the quotient is simply V or velocity. A like division for potential, electrostatic and electro-magnetic gives (1/V), and so on.

The value of the velocity ratio is very nearly 3E10 (sometimes given as 2.98E10) centimeters per second. This is almost exactly that of light (2.9992E10 centimeters per second.) This is one of the proofs of Clerk Maxwell's magnetic theory of light. (See Maxwell's Theory of Light.)

[Transcriber's note: The SI metre was defined in 1983 such that the speed of light in a vacuum is exactly 299,792,458 metres per second or about 186,282.397 miles per second.]

Ventilation of Armature. In a dynamo or motor ventilation of the armature is often provided for by apertures through it in order to prevent heating. This heating is caused by Foucault currents. By proper disposition of the interior of the armature with properly disposed vanes and orifices an action like that of a fan blower can be produced, which by creating a current of air cools the machine very efficiently.

Verticity, Poles of. Points upon the earth's surface where the horizontal component of magnetic force disappears, leaving only the vertical component active. The term is derived from the verticity of the dipping needle when over either of them.

561 STANDARD ELECTRICAL DICTIONARY.

Vibration Period. In electrical resonance the period of a vibration in an electrical resonator. The length of this period indicates the quality of the resonator in responding to electrical oscillations by sympathetic vibration. For conductors of small resistance the period is thus calculated. Let T be the period of one-half a full vibration; L the absolute coefficient of self-induction expressed in centimeters or in henries X 10-9; C the electrostatic capacity of the terminals, also expressed in the same unit; v the velocity of light in centimeters per second. Then we have the formula

T = PI * SquareRoot( L * C ) / v

[Transcriber's note: If the inductance is in henries and the capacitance in farads, frequency in hertz = 1/(2 * PI * squareRoot( L * C ) )]

Vibration, Sympathetic. A vibration in a cord or other body susceptible of elastic vibration produced by the vibrations of exactly the same period in a neighboring vibrating body. Thus if two tuning forks are tuned to precisely the same pitch, and are placed near each other, if one is sounded it will start the other into vibration by sympathy.

In electricity its application is found in electric resonance experiments. The resonator has a definite period of electric resonance, and is made to give a spark by the exciter of identical period. This is by what may be called electric sympathetic vibration, and is exactly analogous to the action of the tuning forks upon each other.

Vibrator, Electro-magnetic. The make and break mechanism used on induction coils, or other similar apparatus in which by alternate attractions by and releases from an electro-magnet an arm or spring is kept in motion. In most cases the work is done by a single magnet, whose armature is attracted to the magnet, when the latter is excited, but against the action of a spring which tends to pull it away from the magnet. In its motions a make and break action is produced, to give the requisite alternations of attraction and release. Two electro-magnets may be connected so as alternately to be excited and keep an arm carrying a mutual armature in vibration, or the same result may be attained by a polarized relay. The make and break is illustrated under Bell, Electric--Coil, Induction-- Anvil.

Villari's Critical Value. Magnetization induced or residual in a wire is diminished on stretching, provided that the magnetization corresponds to an inducing force above a certain critical value, known as above; this being (Sir Wm. Thomson) about 24 times the terrestrial intensity. Below that critical value tension increases the magnetization of a magnetized wire. The effects of transverse expansive stress are opposed to those of longitudinal stretching. (Daniell.)

Viole's Standard of Illuminating Power. A standard authorized by the International Congress of 1881. It is the light given by one square centimeter of platinum, melted, but just at the point of solidification. It is equal to 20 English standard candles almost exactly.

It has not been very widely accepted, the tendency among photometrists being to adhere to the old standards, carcel or candle. It is obvious that actual use of the Viole would be very inconvenient and would involve expensive apparatus, difficult to work with.

Synonym--Viole.

562 STANDARD ELECTRICAL DICTIONARY.

Vis Viva. The kinetic energy of a body in motion; "mechanical energy."

Vitreous Electricity. Positive electricity; the electricity produced on the surface of glass by rubbing it with silk and other substances. (See Electrostatic Series.)

The term "positive electricity" should be allowed to supplant it. It is the analogue and opposite of resinous electricity.

Vitriol, Blue. A colloquial or trade name for copper sulphate (Cu SO4).

Vitriol, Green. A colloquial or trade name for ferrous sulphate (Fe SO4).

Vitriol, White. A colloquial or trade name for zinc sulphate (Zn SO4).

Volt. The practical unit of electro-motive force or potential difference. It may be referred to various data.

An electro-motive force of one volt will cause a current of one ampere to flow through a resistance of one ohm.

A condenser of one farad capacity charged with one coulomb will have a rise of potential of one volt.

The cutting of 100,000,000 lines of force per second by a conductor induces one volt E. M. F.

A Daniell's battery gives an E. M. F. of 1.07 volts; about the most familiar approximate standard that can be cited.

It is equal to 1/300 absolute electrostatic unit.

It is equal to 1E8 absolute electro-magnetic units.

[Transcriber's note: The SI definition of a volt: The potential difference across a conductor when a current of one ampere dissipates one watt of power.]

Voltage. Potential difference or electro-motive force expressed in volts; as a voltage of 100 volts. Thus voltage may express the electro-motive force absorbed in a conductor, while electro-motive force is a term generally applied where it is produced, evolved or present in the object. The term voltage of a lamp expresses simply the volts required, but does not suggest the possession of electromotive force.

563 STANDARD ELECTRICAL DICTIONARY.

Voltage, Terminal. The voltage or potential difference at the terminals of an electric current generator, such as a dynamo, as distinguished from the total electro-motive force of the dynamo or generator.

In batteries the distinction is not generally made in practice; the total electro-motive force of the battery is made the basis of calculations.

Voltaic. adj. This adjective is used to qualify a great many things appertaining to or connected with current electricity. It is derived from Volta, the inventor of the voltaic battery, and now tends to displace the term "galvanic," formerly in general use.

Voltaic Alternatives. A term used in electro-therapeutics or medical electricity to indicate an alternating battery current.

Synonym--Alternative current.

Voltaic Effect. The potential difference developed by contact of different conductors. It is the basis of the contact theory, q. v., of electricity, although it may be accepted as the expression for a condition of things by those who reject the above theory. This potential difference is slight when the conductors are separated, but it is calculated that it would be enormous could the metals be so quickly separated as to hold each its own charge.

Thus if a copper and a zinc plate are assumed to be in contact, really 1/20000000 centimeter or 1/50000000 inch apart, they may be treated as a pair of condenser plates. Being so near, their density of charge, which is a strongly bound charge, is enormous. If it were possible to separate them without permitting any discharge, their potential would rise by the separation, on the principle of Epinus' condenser, q. v., to such an extent that they would spark through twenty feet of air. (See Volta's Fundamental Experiment.)

Voltaic Electricity. Electricity of low potential difference and large current intensity; electricity such as produced by a voltaic battery; current or dynamic electricity as opposed to static electricity.

Voltameter. In general an apparatus for determining the quantity of electricity passing through a conductor by measuring the electrolytic action it can perform.

Voltameter, Copper. An apparatus which may be of similar construction with the silver voltameter (see Voltameter, Silver), but in which a copper anode and a solution of copper sulphate are substituted for the silver anode and silver nitrate solution. One coulomb corresponds to .329 milligram or .005084 grain of copper deposited. It is not accepted as of as high a standard as the silver voltameter.

The electrodes should be placed half an inch from each other. Two square plate electrodes may conveniently be used, and not less than two square inches on each plate should be the area per ampere of current.

564 STANDARD ELECTRICAL DICTIONARY.

Voltameter, Differential, Siemens'. A volume or gas voltameter with duplicate eudiometers and pairs of electrodes. It is used for determining the resistance of the platinum conductor used in his pyrometer. A current divides between the two voltameters; in one branch of the circuit the platinum conductor is placed, in the other a known resistance. The current strength varying inversely with the resistance, the resistances of the two conductors are inversely proportional to the gas evolved.

Voltameter, Gas. A voltameter whose indications are based on the electrolysis of water, made an electrolyte by the addition of sulphuric acid. The gases evolved are measured. It may take several forms.

In one form it is an apparatus consisting of a single eudiometer or graduated glass tube with upper end closed and its lower end or mouth open, collecting the mixture of hydrogen and oxygen.

In the form shown in the cut three tubes are connected, the side tubes representing eudiometers. For each side tube there is a platinum electrode. In this apparatus the oxygen and hydrogen are connected in opposite tubes. A is an open tube filled with dilute sulphuric acid. By opening the cocks on B and C they can both be completely filled with acid. As shown in the cut, this operation is not yet completed. The hydrogen alone may in this case be measured.

The mixed gas voltameter has only one eudiometer.

The exact equivalents are only approximately known. The volume of mixed gases per coulomb is given as .1738 cubic centimeters (Ayrton); .172 cubic centimeters (Hospitalier); and other values by other authorities. The hydrogen is equal to 1/3 of the mixed gases almost exactly.

Synonyms--Volume Voltameter--Sulphuric Acid Voltameter.

The gas is measured at 0º (32º F.) and 76 centimeters, or 30 inches barometer.

Fig. 341. GAS VOLTAMETER.

565 STANDARD ELECTRICAL DICTIONARY.

If the gas is measured in cubic inches, the temperature in degrees F., and the barometric height in inches, the following formula may be used for reduction to standard pressure and temperature. It is the volume corresponding to one coulomb. ( .01058 * 30 * (491 + Fº - 32) ) / (h* 491)

For the metric measurements and degrees C. (.1738 * 76 * (273 + Cº)) / (h X 273)

Voltameter, Silver. An apparatus consisting of a platinum vessel containing a solution of silver nitrate into which solution a silver anode dips, whose end is wrapped in muslin to prevent the detachment of any particles. When a current is passed by connecting one terminal to the dish and the other to the rod, securing a proper direction of current, silver will be deposited on the dish and the same amount will be dissolved from the rod. The dish is weighed before and after the test. Its increase in weight gives the silver deposited.

FIG. 342. SILVER VOLTAMETER.

In the cut Ag is the silver anode, Pt is the platinum dish, r is the conducting rod, p is a wooden standard, Cu is a copper plate on which the dish rests and which also serves as a conductor and contact surface, b is a muslin cloth to place over the silver plate to prevent detached particles falling in the dish; s s' are the binding screws.

The weight of silver corresponding to a coulomb is given variously by different authorities. Ayrton and Daniell take 1.11815 milligrams or .017253 grain of metallic silver. Other determinations are as follows: 1.1183 milligrams (Kohlrausch). 1.124 " (Merscart).

The solution of silver nitrate should be from 15 to 30 per cent. of strength. The current should not exceed one ampere per six square inches; or in other words not more than about 3/1000 grain of silver should be deposited per second on a square inch area of the dish. The edge of the silver disc or anode should be about equidistant from the side and bottom of the dish. The latter notes are due to Lord Rayleigh.

566 STANDARD ELECTRICAL DICTIONARY.

Voltameter, Weight. A voltameter in which the amount of decomposition is determined by weighing the products, or one of the products of the electrolysis. The titles Voltameter, Copper, and Voltameter, Silver, may be cited.

Fig. 343. WEIGHT VOLTAMETERS.

In the cuts are shown examples of weight gas voltameters. These are tubes light enough to be weighed when charged. Each contains a decomposition cell T, with its platinum electrodes, and charged with dilute sulphuric acid, while t is calcium chloride or other drying agent to collect any water carried off as vapor or as spray by the escaping gases; c are corks placed in position when the weighing is being executed, so as to prevent the calcium chloride from absorbing moisture from the air.

In use the tubes are weighed. They are then connected to the circuit, after removal of the corks, and the decomposition proceeds. After a sufficient time they are removed, the corks put in place, and they are weighed again. The loss gives the water decomposed.

The water corresponding to one coulomb is .09326 milligram .001430 grain, Ayrton, .092 " Hospitalier, .0935 " Daniell.

567 STANDARD ELECTRICAL DICTIONARY.

Voltametric Law. The law on which voltameters are based. The amount of chemical decomposition produced by an electric current in a given electrolyte is proportional to the quantity of electricity passed through the solution.

Fig. 344. VOLTA'S FUNDAMENTAL EXPERIMENT.

Volta's Fundamental Experiment. The moistened finger is placed on the upper plate of a condensing or electrophorous electroscope. The other hand holds a plate of zinc z, soldered to a plate of copper c. The lower plate is touched with the copper. On removing the cover the gold leaves l diverge and with negative electricity. Hence zinc is supposed to be positively electrified when in contact with copper. The experiment is used to demonstrate the contact theory of electricity.

568 STANDARD ELECTRICAL DICTIONARY.

Volta's Law of Galvanic Action. The electro-motive force between any two metals in an electro-chemical series (see Electro-Chemical Series) is equal to the sum of the electro-motive forces between all the intervening metals.

Volta's Law of Thermo-electricity. In a compound circuit, consisting of a number of different metals, all points of which are at the same temperature, there is no current.

Volt, B. A. The volt based on the B. A. ohm. It is equal to .9889 legal volt.

Volt, Congress. The volt based upon the congress or legal ohm; the legal volt.

Volt-coulomb. The unit of electric work; the watt-second; it is equivalent to 1.0E7 ergs. .24068 gram degree C. (calorie) .737337 foot lbs., .00134 horse power seconds.

Volt Indicator. A form of easily read voltameter for use in electric light stations and for similar work.

Volt, Legal. The legal volt based upon the legal ohm. It is equal to 1.00112 B. A. volt.

Voltmeter. An instrument for determining the potential difference of any two points.

In many cases it is a calibrated galvanometer wound with a coil of high resistance. The object to be attained is that it shall receive only an insignificant portion of current and that such portion shall suffice to actuate it. If connected in parallel with any portion of a circuit, it should not noticeably diminish its resistance.

The divisions into which ammeters range themselves answer for voltmeters. In practice the same construction is adopted for both. The different definitions of ammeters in disclosing the general lines of these instruments are in general applicable to voltmeters, except that the wire winding of the coils must be of thin wire of great length. The definitions of ammeters may be consulted with the above understanding for voltmeters.

In the use made of voltmeters there is a distinction from ammeters. An ammeter is a current measurer and all the current measured must be passed through it. But while a voltmeter is in fact a current measurer, it is so graduated and so used that it gives in its readings the difference of potential existing between two places on a circuit, and while measuring the current passing through its own coils, it is by calibration made to give not the current intensity, but the electro-motive force producing such current.

In use it may be connected to two terminals of an open circuit, when as it only permits an inconsiderable current to pass, it indicates the potential difference existing between such points on open circuit. Or it may be connected to any two parts of a closed circuit. Owing to its high resistance, although it is in parallel with the intervening portion of the circuit, as it is often connected in practice, it is without any appreciable effect upon the current. It will then indicate the potential difference existing between the two points.

569 STANDARD ELECTRICAL DICTIONARY.

Voltmeter, Battery. A voltmeter for use in running batteries. In one form (Wirt's) it is constructed for a low range of voltage, reading up to two and a half volts and having exactly one ohm resistance, thus giving the battery some work to do.

Voltmeter, Cardew. A voltmeter in which the current passing through its conductor heats such conductor, causing it to expand. Its expansion is caused to move an index needle. By calibration the movements of the needle are made to correspond to the potential differences producing the actuating currents through it. The magnetic action of the current plays no part in its operation. It is the invention of Capt. Cardew, R. E.

The construction of the instrument in one of its most recent forms is shown in the cut. On each side of the drum-like case of the instrument are the binding screws. These connect with the blocks m and n. To these the fine wire conductor is connected and is carried down and up over the two pulleys seen at the lowest extremity, its centre being attached to c. From c a wire is carried to the drum p, shown on an enlarged scale on the left of the cut. A second wire from the same drum or pulley connects to the spring S. The winding of the two wires is shown in the separate figure of c, where it is seen that they are screwed fast to the periphery of the little drum, and are virtually continuations of each other. By the screw A the tension of the spring S is adjusted.

On the shaft of the little drum p is a pinion, which works into the teeth of the cog-wheel r. The shaft of r is extended through the dial of the instrument, and carries an index. The dial is marked off for volts; g g and h h are standards for carrying the pulleys.

570 STANDARD ELECTRICAL DICTIONARY.

The action of the instrument is as follows. The current passing through the wire heats it. This current by Ohm's law is proportional to the electro-motive force between the terminals. As it is heated it expands and as it cools contracts, definite expanding and contracting corresponding to definite potential differences. As the wire expands and contracts the block or pin c moves back and forth, thus turning the drum p and cogwheel r one way or permitting it to turn the other way under the pull of the spring S.

Fig. 345. CARDEW VOLTMETER.

In this construction for a given expansion of the wire the piece c only moves one half as much. The advantage of using a wire twice as long as would be required for the same degree of movement were the full expansion utilized is that a very thin wire can be employed. Such a wire heats and cools more readily, and hence the instrument reaches its reading more quickly or is more deadbeat, if we borrow a phraseology properly applicable only to instruments with oscillating indexes.

In the most recent instruments about thirteen feet of wire .0025 inch in diameter, and made of platinum-silver alloy is used.

571 STANDARD ELECTRICAL DICTIONARY.

If the potential difference to be measured lies between 30 and 120 volts the wire as described suffices. But to extend the range of the instrument a resistance in series is required. If such resistance is double that of the instrument wire, and remains double whether the latter is hot or cold the readings on the scale will correspond to exactly twice the number of volts. This is brought about in some instruments by the introduction in series of a duplicate wire, precisely similar to the other wire, and like it, carried around pulleys and kept stretched by a spring.

[Transcriber's note: If the series resistance is twice that of the voltmeter, the indicated voltage will be ONE THIRD of the total voltage.]

Thus whatever ratio of resistance exists between the two wires cold, it is always the same at any temperature, as they both increase in temperature at exactly the same rate. Tubes are provided to enclose the stretched wires and pulleys, which tubes are blackened.

The voltmeter is unaffected by magnetic fields, and, as its self-induction is very slight, it is much used for alternating currents. The tubes containing the wire may be three feet long.

Its disadvantages are thus summarized by Ayrton. It absorbs a good deal of energy; it cannot be constructed for small potential differences, as the wire cannot be made thicker, as it would make it more sluggish; there is vagueness in the readings near the zero point and sometimes inaccuracy in the upper part of the scale.

Volts, Lost. The volts at the terminals of a dynamo at full load fall short of their value on open circuit. The difference of the two values are termed lost volts.

Voltmeter, Electrostatic. A voltmeter based on the lines of the quadrant electrometer. It includes two sets of quadrants, each oppositely excited by one of the two parts, whose potential difference is to be determined. They attract each other against a controlling force as of gravity.

One form has the two sets poised on horizontal axes, bringing the parts so that the flat quadrants move in vertical planes.

In another form a number of quadrants are used in each set, the members of the two sets alternating with each other. One set is fixed, the others move and carry the index.

Vulcanite. Vulcanized india rubber which by high proportion of sulphur and proper vulcanization has been made hard. It is sometimes distinguished from ebonite as being comparatively light in color, often a dull red, while ebonite is black. For its electrical properties see Ebonite.

Both substances have their defects, in producing surface leakage. Washing with weak ammonia, or with dilute soda solution, followed by distilled water, is recommended for the surface, if there is any trouble with surface leakage. It may also be rubbed over with melted paraffine wax.

572 STANDARD ELECTRICAL DICTIONARY.

W. (a) A symbol or abbreviation for watt.

(b) A symbol or abbreviation for work.

(c) A symbol or abbreviation for weight.

Wall Bracket. A telegraph bracket to be attached to the external walls of buildings to which wires are attached as they come from the poles to reach converters, or for direct introduction into a building.

Wall Sockets. Sockets for incandescent lamps constructed to be attached to a wall.

Ward. Direction in a straight line; a term proposed by Prof. James Thompson. The words "backward" and "forward" indicate its scope.

Water. A compound whose molecule consists of two atoms of hydrogen and one atom of oxygen; formula, H2 O.

Its specific gravity is 1, it being the base of the system of specific gravities of solids and liquids.

If pure, it is almost a non-conductor of electricity. If any impurity is present it still presents an exceedingly high, almost immeasurable true resistance, but becomes by the presence of any impurity an electrolyte.

Water Equivalent. In a calorimeter of any kind the weight of water which would be raised as much as is the calorimeter with its contents by the addition of any given amount of heat received by the calorimeter.

Waterproof Lamp Globe. An outer globe for incandescent lamps, to protect them from water.

Watt. (a) The practical unit of electric activity, rate of work, or rate of energy. It is the rate of energy or of work represented by a current of one ampere urged by one volt electro-motive force; the volt-ampere.

It is the analogue in electricity of the horse power in mechanics; approximately, 746 watts represent one electric horse power.

Ohm's law, taken as C = E/R, gives as values for current, C and E/R, and for electro- motive force C R. In these formulas, C represents current strength, R represents resistance and E represents electro-motive force. Then a watt being the product of electro-motive force by current strength, we get the following values for rate of electric energy, of which the watt is the practical unit: (1) E2/R -- (2) C*E -- (3) C2 * R.

The equivalents of the watt vary a little according to different authorities. Ayrton gives the following equivalents: 44.25 foot pounds per minute--.7375 foot pounds per second--1/746 horse power. These values are practically accurate. Hospitalier gives .7377 foot pounds per second. Hering gives .737324 foot pounds per second, and 1000/745941 horse power.

573 STANDARD ELECTRICAL DICTIONARY.

It is equal to 1E7 ergs per second.

Synonym--Volt-ampere.

(c) It has been proposed to use the term as the unit of energy, instead of activity or rate of energy (Sir C. W. Siemens, British Association, 1882); this use has not been adopted and may be regarded as abandoned.

[Transcriber's note; Watt is a unit of POWER--energy per unit of time.]

Watt-hour. A unit of electric energy or work; one watt exerted or expended for one hour.

It is equivalent to : 866.448 gram-degrees C. (calories) 2654.4 foot lbs. 3600 watt-seconds or volt-coulombs. 60 watt-minutes.

Watt-minute. A unit of electric energy or work; one watt exerted or expended for one minute.

It is equivalent to 14.4408 gram-degrees C. (calories), 44.240 foot pounds, 60 watt seconds or volt-coulombs, 1/60 watt hour.

Watts, Apparent. The product in an alternating current dynamo of the virtual amperes by the virtual volts. To give the true watts this product must be multiplied by the cosine of the angle of lead or lag. (See Current, Wattless.)

[Transcriber's note: This is now called a volt-amp. The usual usage is KVA, or kilovolt-ampere.]

Watt-second. A unit of electric energy or work. One watt exerted or expended for one second.

It is equivalent to .24068 gram degree C. (calorie), .000955 lb. degree F., .737337 foot lbs., .0013406 horse power second (English), .0013592 horse power second (metric).

Synonym--Volt-coulomb.

Waves, Electro-magnetic. Ether waves caused by electromagnetic disturbances affecting the luminiferous ether. (See Discharge, Oscillatory--Maxwell's Theory of Light--Resonance. Electric.)

[Transcriber's note: The Michaelson-Morley experiment (1887) had already called ether into question, but quantum theory and photons are decades in the future.]

574 STANDARD ELECTRICAL DICTIONARY.

Weber. (a.) A name suggested by Clausius and Siemens to denote a magnet pole of unit strength. This use is abandoned.

(b.) It has been used to designate the unit of quantity--the coulomb. This use is abandoned.

(c.) It has been used to designate the unit of current strength the ampere. This use is abandoned.

[Transcriber's note: Definition (a) is now used. One weber of magnetic flux linked to a circuit of one turn produces an electromotive force of 1 volt if it is reduced to zero at a uniform rate in 1 second.]

Weber-meter. An ampere-meter or ammeter. The term is not used since the term "weber," indicating the ampere or coulomb, has been abandoned.

Welding, Electric. Welding metals by heat produced by electricity. The heat may be produced by a current passing through the point of junction (Elihu Thomson) or by the voltaic arc. (Benardos & Olzewski.)

Fig. 346. ELECTRIC WELDING INDUCTION COIL.

The current process is carried out by pressing together the objects to be united, while holding them in conducting clamps. A heavy current is turned on by way of the clamps and rapidly heats the metals at the junction, which is of course the point of highest resistance. As the metal softens, it is pressed together, one of the clamps being mounted with feed motion, flux is dropped on if necessary, and the metal pieces unite.

The most remarkable results are thus attained; almost all common metals can be welded, and different metals can be welded together. Tubes and other shapes can also be united. In many cases the weld is the strongest part.

575 STANDARD ELECTRICAL DICTIONARY.

The alternating current is employed. A special dynamo is sometimes used to produce it. This dynamo has two windings on the armature. One is of fine wire and is in series with the field magnets and excites them. The other is of copper bars, and connects with the welding apparatus, giving a current of high intensity but actuated by low potential.

Where the special dynamo is not used, an induction coil or transformer is used. The primary includes a large number of convolutions of relatively fine wire; the secondary may only be one turn of a large copper bar.

The cut shows in diagram an electric welding coil. P is the primary coil of a number of turns of wire; S S is the secondary, a single copper bar bent into an almost complete circle. It terminates in clamps D D for holding the bars to be welded. B C, B' C are the bars to be welded. They are pressed together by the screw J. The large coil I of iron wire surrounding the coils represents the iron core.

The real apparatus as at present constructed involves many modifications. The diagram only illustrates the principle of the apparatus.

In welding by the voltaic arc the place to be heated is made an electrode of an arc by connection with one terminal of an electric circuit. A carbon is connected to the other terminal. An arc is started by touching and withdrawal of the carbon. The heat may be used for welding, soldering, brazing, or even for perforating or dividing metal sheets.

Welding Transformer. The induction coil or transformer used in electric welding. For its general principles of construction, see Welding, Electric.

Wheatstone's Bridge. A system of connections applied to parallel circuits, including resistance coils for the purpose of measuring an unknown resistance. A single current is made to pass from A through two parallel connected branches, joining together again at C. A cross connection B D has a galvanometer or other current indicator in circuit. In any conductor through which a current is passing, the fall of potential at given points is proportional to the resistance between such points. Referring to the diagram a given fall of potential exists between A and C. The fall between A and B is to the fall between A and C as the resistance r between A and B is to the resistance r + r' between A and C. The same applies to the other branch, with the substitution of the resistances s and S' and the point D for r r' and B. Therefore, if this proportion holds, r : r' : : s : S'. No current will go through B D , and the galvanometer will be unaffected. Assume s' to be of unknown resistance, the above proportion will give it, if r, r' and s are known, or if the ratio of r to r' and the absolute value of s is known.

576 STANDARD ELECTRICAL DICTIONARY.

In use the resistances r, r', and s are made to vary as desired. To measure an unknown resistance it is introduced at S', and one of the other resistances is varied until the galvanometer is unaffected. Then the resistance of S' is determined by calculation as just explained. The artificial resistances may be resistance coils, q. v., or it is enough to have one unknown resistance at s. Then if the length of wire ABC is accurately known, the point B can be shifted along it until the balance is attained. The relative lengths A B, and B C, will then give the ratio r : r' needed for the calculation. This assumes the wire ABC to be of absolutely uniform resistance. This is the principle of the meter-bridge described below. The use of coils is the more common method and is carried out by special resistance boxes, with the connections arranged to carry out the exact principle as explained. The principle of construction and use of a resistance box of the Wheatstone bridge type, as shown in the cut, is described under Box Bridge, q. v.

FIG. 347. WHEATSTONE BRIDGE CONNECTIONS.

FIG. 348. TOP OF BOX BRIDGE.

577 STANDARD ELECTRICAL DICTIONARY.

The next cut shows the sliding form of bridge called the meter bridge, if the slide wire is a meter long or a half- or a quarter-meter bridge, etc., according to the length of this wire. It is described under Meter Bridge, q. v. Many refinements in construction and in proper proportion of resistances for given work apply to these constructions.

Synonyms--Electric Balance--Resistance Bridge--Wheatstone's Balance.

Fig. 349. METER BRIDGE.

Whirl, Electric. (a) A conductor carrying an electric current is surrounded by circular lines of force, which are sometimes termed an electric whirl.

(b) The Electric Flyer. (See Flyer, Electric.)

Wimshurst Electric Machine. An influence machine for producing high potential or static electricity.

Two circular discs of thin glass are mounted on perforated hubs or bosses of wood or ebonite. Each hub has a groove turned upon it to receive a cord. Each disc is shellacked. They are mounted on a horizontal steel spindle so as to face and to be within one-eighth of an inch of each other. On the outside of each disc sixteen or eighteen sectors of tinfoil or thin metal are cemented.

578 STANDARD ELECTRICAL DICTIONARY.

Two curved brass rods terminating in wire brushes curved into a semi-ellipse just graze the outer surfaces of the plates with their brushes. They lie in imaginary planes, passing through the axis of the spindle and at right angles from each other.

Four collecting combs are arranged horizontally on insulating supports to collect electricity from the horizontal diameters of the discs. These lie at an angle of about 45° with the other equalizing rods. Discharging rods connect with the collecting combs.

The principle of the machine is that one set of sector plates act as inductors for the other set. Its action is not perfectly understood.

It works well in damp weather, far surpassing other influence machines in this respect. On turning the handle a constant succession or stream of sparks is produced between the terminals of the discharging rods.

Windage. In a dynamo the real air gap between the armature windings and pole pieces is sometimes thus termed.

Wind, Electric. The rush of air particles from a point connected to a statically charged condenser.

Winding, Compound. A method of winding a generator or motor in which a shunt winding is used for the field magnets and in which also a second winding of the magnet is placed in series with the outer circuit. (See Winding, Series--Winding, Shunt.)

Fig. 350. CHARACTERISTIC CURVES OF SHUNT AND SERIES WINDING.

The object of compound winding is to make a self-regulating dynamo and this object is partly attained for a constant speed.

The characteristic curves of shunt and series winding are of opposite natures. The first increases in electro-motive force for resistance in the outer circuit, the latter decreases under the same conditions. If the windings are so proportioned that these conditions for each one of the two windings are equal and opposite, it is evident that the characteristic may be a straight line. This, however, it will only be at a single speed of rotation.

579 STANDARD ELECTRICAL DICTIONARY.

Winding, Disc. A winding which (S. P. Thompson) may be treated as a drum winding extended radially, the periphery corresponding to the back end of the drum. The magnet poles are generally placed so as to face the side or sides of the disc.

Winding, Lap. A method of winding disc and drum armatures. It consists in lapping back each lead of wire towards the preceding lead upon the commutator end of the armature. Thus taking the letter U as the diagrammatical representation of a turn of wire in connecting its ends to the commutator bars they are brought towards each other so as to connect with contiguous commutator bars. This carries out the principle of keeping the two members of the U moving in regions of opposite polarity of field, so that the currents induced in them shall have opposite directions, thus producing a total current in one sense through the bent wire.

Winding, Long Shunt. A system of compound winding for dynamos and motors. The field is wound in series and, in addition thereto, there is a shunt winding connected across from terminal to terminal of the machine, and which may be regarded either as a shunt to the outer circuit, or as a shunt to the series-field and armature winding. (See Winding, Short Shunt.)

Synonyms--Series and Long Shunt Winding.

Winding, Multiple. A winding of an electro-magnet, in which separate coils are wound on the core, so that one or any number may be used as desired in parallel or in series. For each coil a separate binding post should be provided.

Winding, Multipolar. Winding adapted for armatures of multi-polar dynamos or motors.

Winding, Series. A method of winding a generator or motor, in which one of the commutator-brush connections is connected to the field-magnet winding; the other end of the magnet winding connects with the outer circuit. The other armature-brush connects with the other terminal of the outer circuit.

Winding, Series and Separate Coil. A method of automatic regulation applied to alternating current dynamos.

Winding, Short Shunt. A method of compound winding for dynamos and motors. The field is wound in series, and in addition thereto there is a shunt winding connected from brush to brush only, thus paralleling the armature. (See Winding, Long Shunt.)

Synonyms--Series and Short Shunt Winding.

580 STANDARD ELECTRICAL DICTIONARY.

Winding, Shunt. A method of winding a generator or motor. Each commutator-brush has two connections. One set are the terminals of the outer circuit, the other set are the terminals of the field-magnet windings. In other words, the field-magnet windings are in shunt or in parallel with the outer circuit.

Winding, Shuttle. A method of dynamo or motor-armature winding. A single groove passes longitudinally around the core and in this the wire is continuously wound. The system is not now used. The old Siemens' H armature illustrates the principle.

Winding, Wave. A method of winding disc and drum armatures. It consists in advancing the commutator ends of the U shaped turns progressively, so that as many commutator bars intervene between any two consecutive commutator connections of the wire as there are leads of wire on the drum between consecutive leads of the wire. This is carried out with due regard to the principle that taking the letter U as the diagrammatical representation of a turn of wire, its two members must move through regions of the field of opposite polarity.

Wire Finder. A galvanometer or other instrument used for identifying the ends of a given wire in a cable containing several.

Work. When a force acts upon a body and the body moves in the direction of the force, the force does work. Hence, work is the action of a force through space against resistance.

It is generally expressed in compound units of length and weight, as foot-pounds, meaning a pound raised one foot.

Work, Electric, Unit of. The volt-coulomb, q. v., or watt-second, as it is often termed.

Working, Diode. In multiplex telegraphy the transmission of two messages, simultaneously, over one wire. (See Telegraphy, Multiple.)

Working, Contraplex. A variety of duplex telegraphy in which the messages are sent from opposite ends of the line, simultaneously, so as to be transmitted in opposite directions. (See Working, Diplex.)

Working, Diplex. In duplex telegraphy the sending of two independent messages from the same end of the line in the same direction.

581 STANDARD ELECTRICAL DICTIONARY.

Working, Double Curb. A method of working telegraph lines. When a signal is sent the line is charged. This has to be got rid of, and is an element of retardation. In double curb working it is disposed of by sending a momentary current first in the reverse, and then in the same, and finally in the reverse direction. This is found to reduce the charge to a very low point.

Working, Hexode. In multiplex telegraphy the transmission of six messages simultaneously over one wire. (See Telegraphy, Multiplex.)

Working, Pentode. In multiplex telegraphy the transmission of five messages simultaneously over one wire. (See Telegraphy, Multiplex.)

Working, Reverse Current. A method of telegraphy, in which the currents are reversed or alternated in direction.

Working, Single Curb. A simpler form of telegraph signaling than double curb working. It consists in sending a reverse current through the line for each signal by reversing the battery connection.

Working, Tetrode. In multiplex telegraphy the transmission of four messages simultaneously over the same line. (See Telegraphy, Multiplex.)

Working, Triode. In multiplex telegraphy the transmission of three messages simultaneously over the same wire. (See Telegraphy, Multiplex.)

Work, Unit of. The erg, q. v. It is the same as the unit of energy, of which work is the corelative, being equal and opposite to the energy expended in doing it. There are many other engineering units of work, as the foot-pound and foot-ton.

Yoke. In an electro-magnet, the piece of iron which connects the ends furthest from the poles of the two portions of the core on which the wire is wound.

Zamboni's Dry Pile. A voltaic pile or battery. It is made of discs of paper, silvered or tinned on one side and sprinkled on the other with binoxide of manganese. Sometimes as many as 2,000 of such couples are piled up in a glass tube and pressed together with two rods which form the terminals. They maintain a high potential difference, but having very high resistance and slight polarization capacity, give exceedingly small quantities.

Zero. (a) The origin of any scale of measurement.

(b) An infinitely small quantity or measurement.

582 STANDARD ELECTRICAL DICTIONARY.

Zero, Absolute. From several considerations it is believed that at a certain temperature the molecules of all bodies would touch each other, their kinetic motion would cease, and there would be no heat. This temperature is the absolute zero. It is put at -273° C. (-459° F.)

[Transcriber's note; The modern value is 0° Kelvin, -273.15° C, or -459.67° F. The lowest reported temperature observed is 1E-10° K.]

Zero, Potential. Conventionally, the potential of the earth. True zero potential could only exist in the surface of a body infinitely distant from other electrified bodies.

Zero, Thermometric. There are three thermometric zeros. In the Réaumur and centigrade scales, it is at the temperature of melting ice; in the Fahrenheit scale, it is 32° F. below that temperature, or corresponds to -17.78° C.

The third is the absolute zero. (See Zero, Absolute.)

Zinc. A metal; one of the elements; atomic weight, 65.1; specific gravity, 6.8 to 7.2.

microhms. Resistance at 0° C. (32° F.), per centimeter cube, 5.626 Resistance at 0° C. (32° F.), per inch cube, 2.215

Relative resistance (silver = 1), 3.741

ohms. Resistance of a wire, 1 foot long, weighing 1 grain, .5766 (a) 1 foot long, 1 millimeter diameter, 33.85 (b) 1 meter long, weighing 1 gram, .4023 (c) 1 meter long, 1 millimeter diameter, .07163

Zinc is principally used in electrical work as the positive plate in voltaic batteries.

Zincode. The terminal connecting with the zinc plate, or its equivalent in an electric circuit; the negative electrode; the kathode. A term now little used.

Zinc Sender. An apparatus used in telegraphy for sending a momentary reverse current into the line after each signal, thus counteracting retardation.

Zone, Peripolar. In medical electricity, the region surrounding the polar zone, q. v.

Zone, Polar. In medical electricity, the region surrounding the electrode applied to the human body.

583-624 INDEX.

Page A 7 Absolute 7 Absolute Calibration 97 Absolute Electric Potential 429 Absolute Electrometer 222 Absolute Galvanometer 266 Absolute Measurement 8 Absolute Potential 428 Absolute Temperature 8 Absolute Unit 554 Absolute Unit Resistance, Weber's 468 Absolute Vacuum 557 Absolute Zero 581 Abscissa 7 Abscissas, Axis of 54 Absorption, Electric 8 A. C. C. 8 Acceleration 8 Accumulator 8 Accumulator, Electrostatic 8 Accumulator, Water Dropping 9 Acetic Acid Battery 58 Acheson Effect 208 Acid, Carbonic 108 Acid, Chromic, Battery 61 Acid, Hydrochloric, Battery 66 Acid, Spent 491 Acid, Sulphuric 497 Acidometer 10 Acierage 494 Aclinic Line 10 Acoustic Telegraphy 10 Acoutemeter 10, 53 Action, Electrophoric 230 Action, Local 331 Action, Magne-crystallic 335 Action, Refreshing 454 Action, Secondary 477 Actinic Photometer 411 Actinic Rays. 11 Actinism 11 Actinometer, Electric 11 Active Electric Circuit, 123 Activity 11 Actual Horse Power 290 Adapter 11 A. D. C., 11 Adherence, Electro-magnetic 11 Adherence, Magnetic 338 Adjuster, Cord 152 Adjustment of Brushes 90 Admiralty Rules of Heating 12 AEolotropic 34 Aerial Cable 95 Aerial Conductor 12 Affinity 12 Affinity, Molecular 380 After Current,. 159 Agglomerate Leclanché Battery 66 Agir Motor 13 Agone 13 Agonic Line, 13 Air 13 Air Blast 13 Air Condenser 14 Air Field 252 Air Gaps 15 Air Line Wire 15 Air Pump, Heated 15 Air Pump, Mercurial 16 Air Pumps, Short Fall 16 Alarm, Burglar 16 Alarm, Electric 17 Alarm, Fire, Electric Automatic 257 Alarm, Fire and Heat 17 Alarm, Overflow 18 Alarm, Water Level 18 Alcohol, Electric Rectification of 18 Alignment, 18 Allotropy 18 Alloy 18 Alloy, Platinum 419 Alloy, Platinum-Silver 419 Alloys, Paillard 400 Alphabet, Telegraphic 19 Alternating 23 Alternating Current 159 Alternating Current Arc 23 Alternating Current Dynamo 193 Alternating Current Generator or Dynamo 24 Alternating Current Meter 373 Alternating Current System 23 Alternating Field 252 Alternative Current 563 Alternative Path 24 Alternatives, Voltaic 563 Alternator 24 Alternator, Constant Current 24 Alternator, Dead Point of an 177 Alternation 23 Alternation, Complete 23 Alternation, Cycle of 175 Alum Battery 58 Aluminum 24 Aluminum Battery 58 Amalgam 24 Amalgamation 25 Amber 25 American Twist Joint 309 Ammeter 26 Ammeter, Ayrton 26 Ammeter, Commutator 26 Ammeter, Cunynghame's 26 Ammeter, Eccentric Iron Disc 27 Ammeter, Electro-magnetic 27 Ammeter, Gravity 27 Ammeter, Magnetic Vane 27 Ammeter, Magnifying Spring 28 Ammeter, Permanent Magnet 28 Ammeter, Reducteur for 453 Ammeter, Solenoid 28 Ammeter, Spring 28 Ammeter, Steel Yard 28 Ammunition Hoist, Electric 29 Amperage 29 Ampere 29 Ampere- and Volt-meter Galvanometer 274 Ampere Arc 30 Ampere Balance 56 Ampere Currents 30 Ampere Feet 30 Ampere-hour 30 Amperes, Lost 30 Ampêre's Memoria Technica 30 Ampere Meters 26, 30 Ampere Meter, Balance 391 Ampere Meter, Neutral Wire 391 Ampere-minute 30 Ampere Ring 30 Ampere-second 30 Ampere's Theory of Magnetism 354 Ampere-turns 31 Ampere-turns, Primary 31 Ampere-turns, Secondary 31, 551 Ampere Windings 31 Ampérian Currents 165 Amplitude of Waves 31 Analogous Pole 31, 425 Analysis 31 Analysis, Electric 32 Analysis, Electrolytic 214 Analyzer, Electric 32 Anelectrics 32 Anelectrotonus 32 Angle of Declination 32, 177 Angle of the Polar Span 32 Angle of Inclination or Dip 33 Angle of Lag 33-318 Angle of Lead 33 Angle of Maximum Sensitiveness 479 Angle of Polar Span 423 Angle, Polar 423 Angle, Unit 554 Angular Currents 165 Angular Currents, Laws of 165 Angular Force 544 Angular Velocity 32, 559 Animal Electricity 33 Animal System, Electric Excitability of 247 Anion 33 Anisotropic 34 Annealing, Electric 34 Annular Electro-magnet 216 Annunciator 34 Annunciator Clock 35 Annunciator Clock, Electric 127 Annunciator Drop 35 Annunciator, Gravity Drop 35 Annunciator, Needle 35 Annunciator, Swinging or Pendulum 35 Anodal Diffusion 35 Anode 36 Anodic Closure Contraction 36 Anodic Duration Contraction 36 Anodic Opening Contraction 36 Anodic Reactions 36 Anomalous Magnet 335 Anti-induction Conductor 36, 145 Anti-magnetic Shield 37 Antilogous Pole, 425 Antimony 37 Anvil 37 A. O. C. 38 Aperiodic 38 Aperiodic Galvanometer 266 Apparent Coefficient of Magnetic Induction 346 Apparent Resistance 297, 462 Apparent Watts 573 Arago's Disc 88 Arc 39 Arc, Ampere 30 Arc, Compound. 39 Arc, Electric Blow-pipe 84 Arc, Metallic 39 Arc, Micrometer 39, 376 Arc, Multiple 387 Arc, Simple 39 Arc, Voltaic 39 Arc Box, Multiple 387 Arc Lamp 319 Arc Lamp, Differential 320 Arc Lamp, Double Carbon 191 Areometer 41 Areometer, Bead 41 Argyrometry 41 Arm 41 Armature 41 Armature, Bar 42 Armature, Bipolar 42 Armature Bore 42 Armature Chamber 42 Armature, Closed Coil 43 Armature Coil, or Coils 43 Armature Conductors, Lamination of 319 Armature Core 43 Armature, Cylinder 43 Armature, Cylindrical 45 Armature, Disc 43 Armature, Drum 45 Armature Factor 45 Armature, Flat Ring 45 Armature, Girder 49 Armature, H 49 Armature, Hinged 45 Armature, Hole 45 Armature, Intensity 45 Armature Interference 45 Armature, Load of 46 Armature, Multipolar 46 Armature, Neutral 46 Armature, Neutral Relay 46, 390 Armature, Non-polarized 46 Armature of Influence Machine 46 Armature of Leyden Jar or Static Condenser 46 Armature, Open Coil 46 Armature, Perforated 45 Armature, Pivoted 47 Armature Pockets 47 Armature, Polarized 47 Armature, Pole 47 Armature, Quantity 47 Armature, Radial 47 Armature Reactions 41 Armature, Revolving, Page's 47 Armature, Ring 48 Armature, Rolling 49 Armatures, Gyrostatic Action of 288 Armature, Shuttle 49 Armature, Siemens' Old 49 Armature, Spherical 49 Armature, Stranded Conductor 49 Armature, Unipolar 50, 553 Armature, Ventilation of 560 Armor of Cable 50 Arm, Rheostat 472 Arms, Proportionate 436 Arms, Ratio 437 Arms, Rocker 50-474 Arrester, Lightning 328 Arrester, Lightning, Counter-electro-motive Force 329 Arrester, Lightning, Plates 329 Arrester, Lightning, Vacuum. 329 Arrester Plate 417 Arrester, Spark 489 Arrival Curve 168 Articulate Speech 50 Artificial Carbon 106 Artificial Magnet 335 Ascending Lightning 330 Assymmetrical Resistance 462 Astatic 50 Astatic Circuit 12 Astatic Couple 157 Astatic Galvanometer 266 Astatic Needle 50 Astronomical Meridian, 372 Asymptote 51 Atmosphere 51 Atmosphere, Residual 51, 460 Atmospheric Electricity 51 Atom 52 Atomic Attraction 52 Atomic Current 160 Atomic Energy 238 Atomic Heat 52-285 Atomic Weight 53 Atomicity 52 Attracted Disc Electrometer 223 Attraction 53 Attraction, Atomic 52 Attraction, Magnetic 338 Attraction, Molar 380 Attraction, Molecular 380 Attraction and Repulsion, Electro-dynamic 211 Attraction and Repulsion, Electro-magnetic 217 Attraction and Repulsion, Electro-static 234 Attraction and Repulsion, Electro-static, Coulomb's Law of 155 Audiometer 53 Aura, Electrical 53 Aurora 53 Austral Pole 54 Autographic Telegraph 510 Automatic Circuit Breaker 121 Automatic Cut Out 175, 475 Automatic Drop 192 Automatic Electric Bell 78 Automatic Electric Fire Alarm 257 Automatic Switch 500 Automatic Telegraph 504 A. W. G., 54 Axial Couple 514 Axial Force 544 Axial Magnet 336 Axis, Electric 54 Axis, Magnetic 338 Axis of Abscissas 54 Axis of Ordinates 54, 397 Axis of X 54 Axis of Y 54, 397 Ayrton's Ammeter 26 Azimuth 54 Azimuth Circle 54 Azimuth Compass 141 Azimuth, Magnetic 338

B 55 B. A. 55 Back Electro-motive Force of Polarization 156 Back Induction 55 Back Shock or Stroke of Lightning 55 Back Stroke 55 Bagration Battery 59 Balance 55 Balance, Ampere 56 Balance Ampere Meter 391 Balance, Electric 577 Balance, Inductance 293 Balance, Plating 417 Balance, Slide 374 Balance, Thermic 85 Balance, Torsion, Coulomb's 544 Balance, Wheatstone's 577 Balata 56 Ballistic Galvanometer 567 Balloon Battery 59 B. and S. W. G. 56 Banked Battery 59 Bank of Lamps 323 B. A. Ohm 394 Barad 56 Bar, Armature 42 Bar, Bus 94 Bar Electro-magnet 217 Bar Magnet 336 Barometer 56 Bar, Omnibus 94 Bar Photometer 411 Bars, Commutator 56, 140 Bath 57 Bath, Bipolar Electric 57 Bath, Copper 152 Bath, Copper Stripping 152 Bath, Electric Head 284 Bath, Electric Shower 57 Bath, Gold 279 Bath, Gold Stripping 279 Bath, Multipolar Electric 57 Bath, Nickel 391 Bath, Plating 418 Baths, Electro-medical 222 Bath, Silver 484 Bath, Silver Stripping 484 Bath, Stripping 57 Bath, Unipolar Electric 57 Batten 57-58 Battery, Acetic Acid 58 Battery, Alum 58 Battery, Aluminum 58 Battery, Bagration 59 Battery, Balloon 59 Battery, Banked 59 Battery, Bichromate 59 Battery, Bunsen 59 Battery, Cadmium 60 Battery, Callan 60 Battery, Camacho's 60 Battery, Carré's 60 Battery, Cautery 61 Battery Cell, Element of a 237 Battery, Chloric Acid 61 Battery, Chloride of Lime 61 Battery, Chromic Acid 61 Battery, Closed Circuit 61 Battery, Column 61 Battery, d'Arsonval's 62 Battery, de la Rue .62 Battery, de la Rive's Floating 179 Battery, Dry 63 Battery, Elements of 63 Battery, Faradic 63 Battery, Ferric Chloride 63 Battery, Fuller's 63 Battery, Gas 63 Battery, Gas, Grove's 281 Battery Gauge 64 Battery, Gravity 64 Battery, Grenet 65 Battery, Grove's 65 Battery, Hydrochloric Acid 66 Battery, Lalande & Chaperon 69 Battery, Lalande-Edison 69 Battery, Lead Chloride 66 Battery, Lead Sulphate 66 Battery, Leclanché 66 Battery, Leclanché Agglomerate 66 Battery, Local 66, 831 Battery, Magnetic 338 Battery, Main 66 Battery, Marié Davy's 67 Battery, Maynooth's 67 Battery, Medical 67 Battery, Meidinger's 68 Battery, Mercury Bichromate 63 Battery Mud 68 Battery, Multiple Connected 68 Battery, Niaudet's 61 Battery, Nitric Acid 68 Battery of Dynamos 6S Battery of Leyden Jars, 68 Battery, Open Circuit 68 Battery or Pile, Thermo-electric 530 Battery, Oxide of Copper 68 Battery, Peroxide of Lead 69 Battery, Platinized Carbon 69 Battery, Plunge 69 Battery, Pneumatic 69 Battery, Primary 69, 434 Battery, Pulvermacher's Electro-medical 69 Battery, Sal Ammoniac 69 Battery, Salt, or Sea Salt 69 Battery, Sand 70 Battery, Secondary 70 Battery, Secondary, Planté's 72 Battery, Secondary, Real Efficiency of 205 Battery, Sir William Thomson's 72 Battery, Siemens and Halske's 72 Battery, Skrivanow 72 Battery, Smee's 73 Battery Solutions, Chromic Acid 73 119, 178, 192, 232, 318, 421, 542, 549 Battery, Spiral 73 Battery, Split 73 Battery, Sulphate of Mercury 67 Battery System, Universal 556 Battery, Thermo-chemical 530 Battery, Trough 73 Battery, Trouvé's Blotting Paper 73 Battery, Tyer's 74 Battery, Upward's 75 Battery, Varley's 76 Battery, Volta's 76 Battery, Voltaic or Galvanic 76 Battery Voltmeter 569 Battery, Water 77 Battery, Wollaston 78 B. A. Unit, 554 B. A. Unit of Resistance 78, 462 B. A. Volt 568 B. E. 78 Bead Areometer 41 Becquerel's Laws of Thermo-electricity 78 Beaumé Hydrometer 78 Bed-piece 78 Bell, Automatic Electric 78 Bell, Call 78, 98 Bell Call 79 Bell Call, Extension 248 Bell, Circular 79 Bell, Differentially Wound 79 Bell, Electric 79 Bell, Electro-mechanical 80 Bell, Indicating 80, 297 Bell, Magneto 80 Bell, Magneto Call 361 Bell, Night 392 Bell-shaped Magnet, 336 Bells, Relay 80, 457 Bell, Trembling 78 Bell, Vibrating. 78 Belts, Joints in 311 Bennett's Electroscope 233 Bias 80 Bias of Tongue of Polarized Relay 542 Bichromate Battery 59 Bichromate Mercury Battery 63 Bifilar Suspension 498 Bifilar Winding 81 Binary Compound 81 Binding 81 Binding Posts or Screws 81 Binnacle 81 Biology, Electro- 208 Bioscopy, Electric 82 Bipolar Armature 42 Bipolar Electric Bath 57 Bisected Coils 132 Bismuth 82 Bi-telephone 82, 524 Black, Platinum 419 Blasting, Electric 83 Bleaching, Electric 83 Block, Branch 87 Block, Cross-over 158 Block System 83 Block Wire 83 Blotting Paper Battery, Trouvé's 73 Blow-pipe 83 Blow-pipe, Electric Arc 84 Blue Magnetism 355 Bluestone 84 Blue Vitriol 562 Board, Cross-connecting 157 Board, Fuse 263 Board, Hanger 284 Board, Key 313 Board, Multiple Switch 387 Board of Trade Ohm 394 Board of Trade Unit 555 Board, Switch 500 Boat, Electric 84 Bobbins 84 Body Protector 84 Bohenberger's Electroscope 233 Boiler Feed, Electric 84 Boiling 84 Boll 85 Bolometer 85 Bombardment, Molecular 380 Bore, Armature 42 Boreal Pole 85 Bot 85 Bound Charge 115 Box Bridge 85 Box, Cable 95 Box, Cooling 151 Box, Distributing 190 Boxes, Flush 258 Box, Fishing 311 Box, Fuse 263 Boxing the Compass 86 Box, Junction 311 Box, Multiple Arc 387 Box, Resistance 462 Box, Resistance, Sliding 463 Box Sounding Relay 457 Box, Splice 492 Bracket, Saddle 475 Bracket, Wall 572 Braid, Tubular 550 Brake, Electro-magnetic 86 Brake, Magneto-electric 362 Brake, Prony 435 Branch 87 Branch Block 87 Branch Circuit 121 Branch Conductor 87 Branding, Electric 87 Brassing 87 Brazing, Electric 87 Break 88 Break, Circuit Loop 125 Break-down Switch 88 Breaker, Automatic Circuit 121 Breaker, Circuit 121 Breaker, Circuit, File 121 Breaker, Contact 121, 146 Break Induced Current 162 Breaking Weight 89 Break, Loop 332 Break Shock 482 Breath Figures, Electric 89 Breeze, Electric 89 Breeze, Static 493 Breguet Unit of Resistance 463 Bridge 89 Bridge, Box 89 Bridge, Inductance 293 Bridge, Induction 293 Bridge Key 313 Bridge, Magnetic 338 Bridge, Meter 373 Bridge, Resistance 577 Bridge, Reversible 472 Bridge, Slide 374 Bridge, Wheatstone . 575 Bridge, Wheatstone, Commercial 36 British Association Bridge 89 Britannia Joint 309 Broadside Method 89 Broken Circuit 125 Bronzing 89 Brush 90 Brush, Carbon 90 Brush, Collecting 90 Brush, Discharge 187 Brushes, Adjustment of 90 Brushes, Lead of 90 Brushes, Negative Lead of 324 Brushes, Scratch 476 Brush, Faradic 251 Brush Holders 91 Brush, Pilot 91 Brush, Rotating 91 Brush, Third 91 Brush Trimmer 549 Brush, Wire Gauge 92 Buckling 92 Bug 92 Bug Trap 92 Bunched Cable 95 Bunsen Battery 59 Bunsen Disc 92 Bunsen's Photometer 412 Buoy, Electric 93 Burglar Alarm 16 Burner, Electric Gas 93 Burning 94 Bus Bar 94 Bus Rod 94 Bus Wire 94 Butt Joint 310 Button, Call 98 Button, Press 94 Button, Push 93, 98 Buzzer 94 B. W. G. 94

C 95 C. C. 109 Cable 95 Cable, Aerial 95 Cable, Armature of 50 Cable, Armor of 50 Cable Box 95 Cable, Bunched 95 Cable, Capacity of 95 Cable Clip 97 Cable Core 96 Cable, Duplex 96 Cable, Flat 96 Cablegram 96 Cable Grip 96 Cable Hanger 96 Cable Hanger Tongs 97 Cable, Suspension Wire of 97 Cable Tank 97 Cadmium Battery 60 Calamine 97 Cal Electricity 208 Calibration 97 Calibration, Absolute 97 Calibration, Invariable 97 Calibration, Relative 98 Call Bell 78, 79, 98 Call Bell, Extension 248 Call Bell, Magneto 361 Call Button 98 Call, Thermo 530 Call, Thermo-electric 531 Callan Battery 60 Calling Drop 98 Calorie or Calory 98 Calorimeter 98 Calorimetric Photometer 412 Calory or Calorie 98 Cam, Listening 330 Camacho's Battery 60 Candle 99 Candle, Concentric 99 Candle, Debrun 99 Candle, Decimal 99 Candle, Electric 99 Candle-foot 259 Candle, German Standard 99 Candle Holder 99 Candle, Jablochkoff 100 Candle, Jamin 100 Candle, Meter 374 Candle Power 100 Candle Power, Nominal 101 Candle Power, Rated 101 Candle Power, Spherical 101 Candle, Standard 101 Candle, Wilde 101 Caoutchouc 101 Cap, Insulator 306 Capacity, Carrying 108 Capacity, Dielectric 102 Capacity, Electric or Electrostatic 102 Capacity, Instantaneous 102 Capacity, Magnetic Inductive 346, 349 Capillarity, Electro- 209 Capillary Electrometer 224 Capacity of a Telegraph Conductor 103 Capacity of Cable 95 Capacity of Polarization of a Voltaic Cell 103 Capacity, Polarization 424 Capacity, Residual 103 Capacity, Specific Inductive 103 Capacity, Storage 105, 495 Capacity, Unit of 105 Capillarity 105 Capillary Telephone 525 Carbon 106 Carbon, Artificial 106 Carbon Brush 90 Carbon, Concentric 107 Carbon, Cored 107 Carbon Dioxide 107 Carbon Holders 107 Carbonic Acid, 108 Carbonic Acid Gas 108 Carbonization 107 Carbonized Cloth 107 Carbon, Platinized, Battery 69 Carbon Resistance 463 Carbon, Retort 471 Carbons, Lamp, Flashing of Incandescent 257 Carbon, Telephone 525 Carbon Transmitter 549 Carbon, Volatilization of 108 Carburetted Hydrogen, Heavy 397 Carcel 108 Carcel Gas Jet 108 Carcel Lamp 108 Card, Compass 142 Cardew Voltmeter 569 Carré's Battery 60 Carrying Capacity 108 Cascade 108 Cascade, Charging and Discharging Leyden Jars in 108 Cascade, Gassiot's 275 Case-hardening, Electric 109 Cataphoresis 109 Catch, Safety 175 Cathode, etc. See Kathode 312 Caustry, Galvano 109 Cautery Battery 61 Cautery, Electric 109 Cautery, Galvano 109 Cautery, Galvano-electric 109 Cautery, Galvano-thermal 109 Cell, Battery, Element of a 237 Cell, Constant 109 Cell, Electrolytic 109 Cell, Porous 427 Cell, Selenium 478 Cell, Standard Voltaic 109 Cell, Standard Voltaic, Daniells' 109 Cell, Standard Voltaic, Latimer Clark's 110 Central Station 493 Central Station Distribution or Supply 112 Centre of Gravity 112 Centre of Gyration 112 Centre of Oscillation 112 Centre of Percussion 112 Centrifugal Force 112 Centrifugal Governor 113 C. G. S. 113 Chain, Molecular 380 Chamber, Armature 42 Chamber of Incandescent Lamp 113 Change, Chemical 116 Changer, Pole 425 Changing Over Switch 500 Changing Switch 500 Chaperon, Lalande &, Battery 69 Characteristic 169 Characteristic Curve 113, 168 Characteristic Curve, External 171 Characteristic Curve of Converter 169 Characteristic, Drooping 114 Characteristic, External 114 Characteristic, Internal 114 Characteristics of Sound 114 Charge 114 Charge and Discharge Key 313 Charge, Bound 115 Charge Current 160 Charge, Density of 115, 180 Charge, Dissipation of 115 Charge, Distribution of 115 Charge, Free 115 Charge, Negative 389 Charge, Residual 116 Charging Curve 170 Chatterton's Compound 116 Chemical Change 116 Chemical Electric Meter 375 Chemical, Electro-, Equivalents 244 Chemical Element 236 Chemical Energy 239 Chemical Equivalent 244 Chemical, Cautery Galvano 265 Chemical Recorder 117 Chemical Telephone 526 Chemical Equivalent, Thermo- 245 Chemistry 118 Chemistry, Electro- 209 Cheval, Force de 260 Chicle 56 Chimes, Electric 118 Chloric Acid Battery 61 Chloride, Ferric, Battery 63 Chloride, Lead, Battery 66 Chloride of Lime Battery 61 Chlorimeter 73 Choking Coil 132 Chronograph, Electric 118 Chromic Acid Battery 61 Chromic Acid Battery Solutions 73 Chromoscope 119 Chutaux's Solution 119 Cipher Code 130 Circle, Azimuth 54 Circle, Delezenne's 133 Circle, Galvanic or Voltaic 119 Circle, Magic 119 Circuit 120 Circuit, Astatic 120 Circuit, Branch 121 Circuit Breaker 121 Circuit Breaker, Automatic 121 Circuit Breaker, File 121 Circuit Breaker, Mercury 121 Circuit Breaker, Pendulum 121 Circuit Breaker, Tuning-fork 121 Circuit, Broken 125 Circuit Changing Switch 500 Circuit, Closed, Battery 61 Circuit, Derivative 123 Circuit, Derived 123 Circuit, Electrostatic 123 Circuit, Electric, Active 123 Circuit, External 123 Circuit, Grounded 123 Circuit, Incomplete 125 Circuit Indicator 298 Circuit Induction, Open 303 Circuit, Leg of 325 Circuit, Local 331 Circuit, Loop 125 Circuit, Loop Break 125 Circuit, Magnetic 340 Circuit, Magnetic Double 340 Circuit, Main 125 Circuit, Main Battery 125 Circuit, Metallic 125 Circuit, Negative Side of 125 Circuit, Open 125 Circuit, Positive Side of 125 Circuit, Recoil 125 Circuit, Return 125 Circuits, Forked 126 Circuit, Short 482 Circuit, Shunt 123, 126 Circuit, Simple 126 Circuits, Parallel 123, 126 Circuit, Voltaic 126 Circuit Working, Short 482 Circular Bell, 79 Circular Current, 160 Circular, Mil 379 Circular Units 126, 555 Circumflux 126 Clamp 126 Clark's Compound 126 Cleansing, Fire 257 Clearance Space, 489 Cleat, Crossing 127 Cleats 127 Cleavage, Electrification by 127 Clip, Cable 97 Clock, Annunciator 35 Clock, Controlled 127 Clock, Controlling 127 Clock, Electric Annunciator 127 Clock, Electrolytic 128 Clock, Master 127 Clock, Secondary 127 Clock, Self-winding, Electric 128 Clockwork Feed 128 Cloisons 128 Closed Circuit Battery 61 Closed Coil Armature 43 Closure 128 Closure Contraction, Kathodic 312 Cloth, Carbonized 107 Club-foot Electro-magnet 217 Clutch 128 Clutch, Electro-magnetic 128 Coatings of a Condenser, or Prime Conductor 129 Cockburn Fuse 263 Code, Cipher 130 Code, S. N. 486 Code, Telegraphic 130, 511 Coefficient 130 Coefficient, Apparent, of Magnetic Induction 346 Coefficient, Economic 130, 204, 205 Coefficient of Electrical Energy 205 Coefficient of Expansion 247 Coefficient of Induced Magnetization 359, 354 Coefficient of Magnetic Induction 346, 349 Coefficient of Mutual Induction 301 Coefficient of Self-induction 298 Coercitive Force 471 Coercive Force 471 Coercive or Coercitive Force 131 Coil and Plunger 131 Coil and Coil Plunger 131 Coil and Plunger, Differential 132 Coil, Armature 43 Coil, Choking 132 Coil, Earth 133 Coil, Electric 133 Coil, Exploring 350 Coil, Flat 133 Coil, Induction 133 Coil, Induction, Inverted 136 Coil, Induction, Telephone 137 Coil. Kicking 132 Coil, Magnet 336 Coil, Magnetizing 137 Coil, Reaction 132 Coil, Resistance 137 Coil, Resistance, Standard 464 Coil, Rhumkorff 138 Coil, Ribbon 138 Coils, Bisected 132 Coils, Compensating 138 Coils, Sectioned 138 Coils, Henry's 138 Coils, Idle 295 Coil, Single, Dynamo 202 Coil, Spark 489 Coil, Sucking 132 Collecting Brush 90 Collecting Ring 139 Collector 139 Colombin, 139 Colophony 460 Colors of Secondary Plates 478 Column Battery 61 Column, Electric 139 Comb 140 Combined Resistance 464 Comb Protector 437 Commercial Efficiency 204 Commercial Efficiency of Dynamo 195 Commercial Wheatstone Bridge 86 Common Reservoir 460 Communicator 140 Commutation, Diameter of 182 Commutator 140 Commutator Ammeter 26 Commutator Bars 140, 56 Commutator, Flats in 140 Commutator, High Bars of 289 Commutator, Neutral Line of 390 Commutator, Neutral Point of 390 Commutator of Current Generators and Motors 140 Commutators, Bars of 56 Commutator Segments 56 Commutator, Split Ring 141 Commuted Current 160 Commuter 140 Commuting Transformer 547 Compass 141 Compass, Azimuth 141 Compass, Boxing the 86 Compass Card, 142 Compass, Declination 142 Compass, Inclination 142 Compass, Mariners' 142 Compass, Points of the 143 Compass, Spirit 143 Compass, Surveyors 143 Compass, Variation of the 32, 558 Compensating Coils 138 Compensating Magnet 336 Compensating Poles 426 Compensating Resistance 144 Complementary Distribution 144 Complete Alternation 23 Component 144 Components of Earth's Magnetism 356 Composition of Forces 260 Compound Arc 39 Compound, Binary 81 Compound, Chatterton's 116 Compound, Clark's 126 Compound Dynamo 195 Compounding, Over- 399 Compound Magnet 336 Compound or Compound Wound Motor 382 Compound Winding 578 Concentration of Ores, Magnetic 340 Concentrator, Magnetic 340 Concentric Candle 99 Concentric Carbon 107 Condenser 144 Condenser, Coatings of a, or Prime Conductor 129 Condenser, Epinus' 242 Condenser, Plate 417 Condenser, Sliding 144 Condenser, Varley's 559 Condensing Electroscope 233 Conductance 144 Conductance, Magnetic 340 Conduction 144 Conduction, Electrolytic 215 Conductive Discharge 187 Conductivity 144 Conductivity, Magnetic 340 Conductivity, Specific 145 Conductivity, Unit of 145 Conductivity, Variable 145 Conductor 145 Conductor, Anti-induction 145 Conductor, Branch 87 Conductor, Capacity of a Telegraph 103 Conductor, Conical 145 Conductor, Imbricated 146 Conductor, Interpolar 307 Conductor, Leakage 325 Conductor, Prime 146, 434 Conductors, Equivalent 146 Conductors, Lamination of Armature 319 Conductors, Service 481 Conductor, Underground 552 Congress Ohm 395 Congress Volt 568 Conical Conductor 145 Conjugate 146 Connect 146 Connection, Cross 158 Connection, Relay 457 Connector 146 Consequent Points 422 Consequent Poles 146, 478 Conservation of Electricity 146 Conservation of Energy 239 Constant Current 160 Constant Current Alternator 24 Constant Current Regulation 454 Constant, Dielectric 183 Constant, Galvanometer 268 Constant Potential 429 Constant Potential Regulation 455 Constant, Time 54l Contact Breaker 121, 146 Contact, Electric 147 Contact Electricity 147 Contact Faults 147 Contact Key, Double 314 Contact Key, Sliding 316 Contact Lamp 320 Contact, Line of 330 Contact Point 147 Contact Potential Difference 147 Contact Ring 473 Contact Spring 148 Contact Series 147 Contact Theory 148 Continuity, Magnetic 340 Continuous Alternating Transformer 547 Continuous Current 161 Continuous Current Transformer 384, 547 Contraction, Anodic Closure 36 Contraction, Anodic Duration 36 Contraction, Anodic Opening 36 Contraction, Kathodic Closure 312 Contraction, Kathodic Duration 312 Contractures 148 Contraplex Working 580 Control, Electro-magnetic 218 Control, Gravity 281 Controlled Clock, 127 Controlling Clock 127 Controlling Field 148 Controlling Force 148 Controlling Magnet 185, 336 Control, Magnetic 341 Control, Spring 492 Convection, Electric 149 Convection, Electrolytic 149, 214 Convection of Heat, Electric 149 Convective Discharge 187 Conversion, Efficiency of 205 Converter 149 Cooling Box 151 Co-ordinates, Origin of 391 Co-ordinates, System of 150 Copper 151 Copper Bath 152 Copper Stripping Bath 152 Copper Voltameter 563 Cord Adjuster 152 Cord, Flexible 152 Cord, Pendant 405 Core 152 Core, Armature 43 Core, Cable 96 Cored Carbon 107 Core-discs 152 Core-discs, Perforated 154 Core-discs, Pierced 152 Core-discs, Toothed 154 Core, Laminated 154 Core, Magnet 336 Core Ratio 154 Core, Ribbon 154 Core, Ring 155 Cores, Krizik's 318 Core, Stranded 155 Core, Tangentially Laminated 155 Core Transformer 155 Core, Tubular 155 Corpusants 155 Corresponding Points 422 Coulomb 155 Coulomb's Law of Electrostatic Attraction and Repulsion 155 Coulomb's Law of Magnetic Attraction and Repulsion 338 Coulomb's Torsion Balance 544 Coulomb, Volt- 568 Counter, Electric 156 Counter Electro-motive Force 156, 228 Counter-electro-motive Force Lightning Arrester 329 Counter Inductive Effect 204 Couple 156 Couple, Astatic 157 Couple, Axial 544 Couple, Magnetic 341 Couple, Moment of 544 Couple, Thermo-electric 532 Couple, Voltaic or Galvanic 156 Coupling 259 Coupling of Dynamo 201 C. P. 157 Crater 157 Creep, Diffusion 184 Creeping 157 Creeping, Magnetic 341 Creeping of Magnetism 356 Crith 157 Critical Current 161 Critical Distance of Alternative Path 190 Critical Resistance 464 Critical Speed 157 Critical Value, Villari's 561 Crookes' Dark Space 489 Cross 157 Cross-connecting Board 157 Cross Connection 158 Cross Induction 298 Crossing Cleat 127 Crossing Wires 158 Cross-magnetizing Effect 158, 298 Cross-over Block 158 Cross, Peltier's 405 Cross Talk 158 Crucible, Electric 158 Crystallization, Electric 158 Cube, Faraday's 249 Culture. Electro- 209 Cunynghame's Ammeter 26 Cup, Mercury 371 Cup, Porous 159, 426 Current 159 Current, After 159 Current, Alternating 159 Current, Alternating System 23 Current, Alternative 563 Current Arc, Alternating 23 Current, Atomic 160 Current, Break Induced 162 Current, Charge 160 Current, Circular 160 Current, Commuted 160 Current, Constant 160 Current, Continuous 161 Current, Continuous, Transformer 384 Current, Critical 161 Current, Daniel 161 Current, U. S. or Siemens' Unit 161 Current, Demarcation 161 Current Density 161 Current, Derived 164 Current, Diacritical 161 Current, Diaphragm 161 Current, Direct 162 Current, Direct Induced 162 Current, Direction of 162 Current, Displacement 162 Current, Extra 162 Current, Faradic 162 Current, Field of Force of a 255 Current, Foucault 163 Current, Franklinic 163 Current Generator 277 Current, Induced 163 Current Induction 163 Current Induction, Unipolar 553 Current Intensity 163 Current, Inverse Induced 163 Current, Jacobi's Unit of 163 Current, Joint 163 Current, Linear 164 Current, Make and Break 164, 367 Current, Make Induced 163 Current Meter 164, 375 Current Meter, Alternating 373 Current, Negative 164 Current, Nerve and Muscle 164 Current, Opposed 164 Current, Partial 164 Current, Polarizing 164 Current, Positive 164 Current, Power of Periodic 433 Current, Pulsatory 164 Current, Rectified 164 Current, Rectilinear 165 Current, Redressed 165 Current Regulation, Constant 454 Current, Reverse Induced 163 Current Reverser 165 Currents, Ampere 30 Currents, Ampérian 165 Currents, Angular. 165 Currents, Angular, Laws of 165 Currents, Earth 166 Current, Secondary 166 Current, Secretion 166 Currents, Eddy 163 Currents, Eddy Displacement 162 Currents in Parallel Circuits, Independence of 297 Current, Sinuous 166 Current, Sheet 166 Current, Shuttle 483 Currents, Local 163 Currents, Local 331 Currents, Multiphase 166 Currents, Natural 166, 389 Currents, Nerve 390 Currents of Motion 167 Currents of Rest 167 Currents, Orders of 167 Currents, Parasitical 163 Currents, Polyphase 167 Currents, Rotatory 167 Currents, Thermo-electric 167 Current Streamlets 495 Current, Swelling 167 Current, Tailing 501 Current, Undulatory 167 Current, Unit 167 Current, Wattless 168 Curve, Arrival 168 Curve, Characteristic 113, 168 Curve, Characteristic, of Converter 169 Curve, Charging 170 Curve, Discharging 170 Curve, Elastic 206 Curve, Electro-motive Force 170 Curve, External Characteristic . 171 Curve, Harmonic 174, 485 Curve, Horse Power 171 Curve, Isochasmen 171 Curve, Life 171 Curve, Load 172 Curve, Magnetization 172 Curve of Distribution of Potential in Armature 172 Curve of Dynamo 173 Curve of Saturation of Magnetic Circuit 174 Curve of Sines 173, 485 Curve of Torque 174 Curve, Permeability Temperature 174 Curve, Sine 174, 485 Curve, Sinusoidal 174, 485 Curves, Magnetic 341 Cut In 174 Cut Out 174 Cut Out, Automatic 175, 475 Cut Out, Magnetic 175 Cut Out, Plug 175 Cut Out, Safety 175 Cut Out, Spring Jack 493 Cut Outs, Time 541 Cut Out, Wedge 175 Cutting of Lines of Force 175 Cycle of Alternation 175 Cycle of Magnetization 360 Cylinder, Armature 43 Cylinder, Electric Machine 333 Cylindrical Armature 45 Cystoscopy 175

Damper 176 Damping 176 Damping Magnet 336 Daniell's Standard Voltaic Cell 109 Dark Space, Faraday's 249 D'Arsonval's Battery 62 Dash-pot 176 Dead Beat 38, 176 Dead Beat Discharge 187 Dead Earth 176, 203 Dead Point of an Alternator 177 Dead Turns 177 Dead Turns of a Dynamo 551 Dead Wire 177 Death, Electrical 177 Debrun Candle 99 Decalescence 177 Decay of Magnetism 356 Deci 177 Decimal Candle 99 Declination, Angle of 32-177 Declination Compass 142 Declination, Magnetic 342 Declination Map 309 Declination of the Magnetic Needle 178 Decomposition 178 Decomposition, Electrolytic 178 Decrement 178 De-energize 178 Deflagration 178 Deflagrator, Hare's 73 Deflecting Field 178 Deflection 178 Deflection Method 178 Deflection of Magnet 337 Degeneration, Reaction of 179 Degradation of Energy 239 Deka 179 De la Rive's Floating Battery 179 De la Rue Battery 62 Delaurier's Solution 179 Delezenne's Circle 133 Demarcation Current 161 Demagnetization 179 Density, Current 161 Density, Electrical 115 Density, Electric Superficial 180 Density, Field 252 Density, Magnetic 342 Density of Charge 115, 180 Dental Mallet, Electric 180 Deposit, Electrolytic 180 Deposit, Nodular 392 Depolarization 180 Depolarizing Fluid 258 Derivation, Points of 180, 423 Derivative Circuit 123 Derived Circuit 123 Derived Current 164 Derived Units 555 Desk Push 180 Detector 180 Detector, Lineman's 180 Deviation of Discharge 188 Deviation, Quadrantal 180 Deviation, Semi-circular 181 Device, Safety 475 Dextrotorsal 181 Diacritical 181 Diacritical Current 161 Diagometer 181 Diagnosis, Electro- 181, 210 Diagram, Thermo-electric 532 Dial Telegraph 505 Diamagnetic 181 Diamagnetic Polarity 181, 423 Diamagnetism 182 Diameter of Commutation 182 Diapason, Electric 182 Diaphragm 182 Diaphragm Current 161 Dielectric, 182 Dielectric Capacity 102 Dielectric Constant 183 Dielectric, Energy of 183 Dielectric Polarization 183 Dielectric Resistance 183, 464 Dielectric Strain 183 Dielectric Strength 183 Dielectric Stress 496 Differential Arc Lamp 320 Differential Coil and Plunger 132 Differential Galvanometer 268 Differentially Wound Bell, 79 Differential Magnetometer 365 Differential Motor 382 Differential Relay 457 Differential Thermo-electric Pile 533 Differential Winding Working 183 Diffusion 184 Diffusion, Anodal . 35 Diffusion Creep 184 Digney Unit of Resistance 464 Dimensions and Theory of Dimensions 184 Dimmer 185 Diode Working 580 Dioxide, Carbon 107 Dioxide, Sulphur 497 Dip, Magnetic 342, 346 Dip of Magnetic Needle 185 Dipping 185 Dipping Needle 185 Direct Current 162 Direct Current Dynamo 197 Direct Induced Current, . 162 Direct Reading Galvanometer 269 Directing Magnet 185 Direction 185 Direction of Current 162 Direction, Positive 428 Directive Power 187 Disc, Arago's 38 Disc, Armature 43 Disc, Bunsen 92 Disc, Dynamo 197 Disc, Faraday's 249 Discharge and Charge Key 313 Discharge, Brush 187 Discharge, Conductive 187 Discharge, Convective 187 Discharge, Dead Beat 187 Discharge, Disruptive 187 Discharge, Duration of 188 Discharge, Glow 187 Discharge, Impulsive 188 Discharge Key, Kempe's 315 Discharge, Lateral 188 Discharge of Magnetism 356 Discharge, Oscillatory 188 Discharger 188 Discharger, Henley's Universal 189 Discharger, Universal 189 Discharger, Universal, Henley's 189 Discharge, Silent 187, 189, 206 Discharge, Spark 189 Discharge, Surging 188 Discharging Curve 170 Discharging Rod 189 Discharging Tongs 189 Disconnection 189 Discontinuity, Magnetic 342 Discovery, Oerstedt's 394 Disc Winding 579 Dispersion Photometer 412 Displacement Current 162 Displacement, Electric 188 Displacement, Oscillatory 398 Disruptive Discharge 187 Disruptive Tension 189 Dissimulated Electricity 189 Dissipation of Charge 115 Dissociation 189, 535 Distance, Critical, of Alternative Path 190 Distance, Explosive 190 Distance, Sparking 190 Distance, Striking 496 Distant Station 493 Distillation 190 Distortion of Field 252 Distributing Box 190 Distributing Switches 190 Distribution, Complementary 144 Distribution, Isolated 309 Distribution of Charge 115 Distribution of Electric Energy, Systems of 190 Distribution of Magnetism, Lamellar, 357 Distribution of Magnetism, Solenoidal 358 Distribution of Supply, Central Station 112 Door Opener, Electric 190 Dosage, Galvanic 190 Double Break Switch 500 Double Carbon Arc Lamp 191 Double Contact Key 314 Double Curb Working 581 Double Fluid Theory 191 Double Fluid Voltaic Cell 191 Double Magnetic Circuit 340 Double Needle Telegraph 506 Double Plug 191 Double Pole Switch 500 Double Tapper Key 314 Double Touch, Magnetization by 358 Double Trolley 549 Double Wedge 191 Doubler 191 D. P. 191 Drag 191 Drag of Field 254 Dreh-Strom 191 Drill, Electric 191 Drip Loop 192 Driving Horns 192 Dronier's Salt 192 Drooping Characteristic 114 Drop, Annunciator 35 Drop, Automatic 192 Drop, Calling 98 Drum Armature 45 Drum, Electric 193 Dry Battery 63 Dry Pile, Zamboni's 581 Dub's Laws 193 Duct 193 Duplex Bridge Telegraph 506 Duplex Cable 96 Duplex Differential Telegraph 507 Duplex Telegraph, 506 Duration Contraction, Kathodic 312 Duration of Electric Spark 490 Dyad 193 Dyeing, Electric 193 Dynamic Electricity 193 Dynamic, Electro- 211 Dynamic Induction, Magnetic 347 Dynamo, Alternating Current 193 Dynamo, Alternating Current Regulation of 195 Dynamos, Battery of 68 Dynamo, Commercial Efficiency of 195 Dynamo, Compound 195 Dynamo, Coupling of 201 Dynamo, Curve of 173 Dynamo, Dead Turns of a 551 Dynamo, Direct Current 197 Dynamo, Disc 197 Dynamo-electric Machine 197 Dynamo, Electroplating 198 Dynamo, Equalizing 198 Dynamo, Field and Armature Reaction of 450 Dynamo, Far Leading 198 Dynamo or Magneto-electric Generator, Flashing in a 257 Dynamo, Inductor 199 Dynamo, Interior Pole 199 Dynamo, Iron Clad 200 Dynamo, Ironwork Fault of a 308 Dynamo, Motor 200 Dynamo, Multipolar 200 Dynamo, Non-polar 200 Dynamo, Open Coil 200 Dynamo, Overtype 399 Dynamos, Regulation of 455 Dynamo, Ring 200 Dynamo, Self Exciting 201 Dynamo, Separate Circuit 201 Dynamo, Separately Excited 201, 479 Dynamo, Series 201 Dynamo, Shunt 202 Dynamo, Single Coil 202 Dynamo, Tuning Fork 202 Dynamo, Unipolar 202, 553 Dynamograph 199 Dynamometer 200 Dyne 203

Earth 203 Earth Coil 133 Earth Currents 166 Earth, Dead 176, 203 Earth, Magnetization by 359 Earth, Partial 203, 404 Earth Plate 203 Earth Return 203 Earth's Magnetism, Components of 356 Earth, Solid 203 Earth, Swinging 203 Earth, Total 203 Ebonite 203 Eccentric Iron Disc Ammeter 27 Economic Coefficient 130, 204, 205 Eddy Currents 163 Eddy Displacement Currents 162 Ediswan 204 Edison Effect 204 Edison-Lalande Battery 69 Eel, Electric 204 Effect, Acheson 208 Effect, Counter-inductive 204 Effect, Cross-magnetizing 158, 298 Effect, Edison 204 Effect, Faraday 249 Effect, Ferranti 251 Effect, Hall 284 Effect, Joule 311 Effect, Kerr 235, 312 Effect, Mordey 381 Effect, Page 401 Effect, Peltier 404 Effect, Photo-voltaic 415 Effect, Seebeck 478 Effect, Skin 486 Effect, Thomson 538 Effect, Voltaic 563 Efficiency 204 Efficiency, Commercial 204 Efficiency, Electrical 205 Efficiency, Gross 205 Efficiency, Intrinsic 205 Efficiency, Net 205 Efficiency of Conversion 205 Efficiency of Secondary Battery Quantity 205 Efficiency of Secondary Battery, Real 205 Efflorescence 206 Effluvium, Electric 206 Egg, Philosopher's 409 Elastic Curve 206 Elasticity, Electric 206 Electrepeter 206 Electric, Absolute, Potential 429 Electric Absorption 8 Electric Actinometer 11 Electric Alarm 17 Electrical Classification of Elements 237 Electrically Controlled Valve 558 Electric Ammunition Hoist 29 Electric Analysis 32 Electric Analyzer 32 Electric Annealing 34 Electric Annunciator Clock 127 Electric Arc Blow-pipe 84 Electric Aura 53 Electric Automatic Fire Extinguisher 257 Electric Axis 54 Electric Balance 577 Electric Bath, Bipolar 57 Electric Bath, Multipolar 57 Electric Bath, Unipolar 57 Electric Bell 79 Electric Bell, Automatic 78 Electric Bioscopy 82 Electric Blasting 83 Electric Bleaching 83 Electric Boat 84 Electric Boiler Feed 84 Electric Branding 87 Electric Brazing 87 Electric Breath Figures 89 Electric Breeze 89 Electric Buoy 93 Electric Candle 99 Electric Case Hardening 109 Electric Cautery 109 Electric Chimes 118 Electric Chronograph 118 Electric Circuit, Active 123 Electric Clock, Self-winding 128 Electric Coil 133 Electric Column 139 Electric Contact 147 Electric Convection 149 Electric Convection of Heat 149, 286 Electric Counter 156 Electric Crucible 158 Electric Crystallization 158 Electric Death 177 Electric Density 115 Electric Dental Mallet 180 Electric Diapason 182 Electric Displacement 189 Electric Door Opener 190 Electric Double Refraction 454 Electric Drill 191 Electric Drum 193 Electric Dyeing 193 Electric Eel 204 Electric Efficiency 205 Electric Effluvium 206 Electric Elasticity 206 Electric Endosmose 238 Electric Energy 239 Electric Energy, Coefficient of 205 Electric Energy, Systems of Distribution of 190 Electric Engraving 245 Electric Entropy 242 Electric Etching 245 Electric Evaporation 246 Electric Excitability of Animal Systems 247 Electric Exosmose 247 Electric Expansion 247 Electric Fire Alarm, Automatic 257 Electric Floor Matting 369 Electric Fluid 258 Electric Fly or Flyer 259 Electric Fog 259 Electric Furnace 263 Electric Fuse 264 Electric Gas Burners 93 Electric Headlight 285 Electric Head Bath 284 Electric Heat 285 Electric Heater 286 Electric Horse Power 290 Electric Image 296 Electric Incandescence 297 Electric Influence 305 Electric Insulation 305 Electricities, Separation of 479 Electricity 206 Electricity, Animal 33 Electricity, Atmospheric 51 Electricity, Cal 208 Electricity, Conservation of 146 Electricity, Contact 147 Electricity, Dissimulated 189 Electricity, Dynamic 193 Electricity, Frictional 262 Electricity, Latent 323 Electricity, Negative 389 Electricity, Plant 317 Electricity, Positive 428 Electricity, Specific Heat of 491 Electricity, Static 493 Electricity, Storage of 495 Electricity, Voltaic 563 Electricity, Vitreous 562 Electric Machine, Plate 417 Electric Machine, Wimshurst 577 Electric Mains 367 Electric Mass 368 Electric Matter 368 Electric Meter, Chemical 375 Electric Meter, Thermal 375 Electric Meter, Time 375 Electric Mortar 382 Electric Motor 382 Electric or Electrostatic Capacity 102 Electric Organ 397 Electric Oscillations 398 Electric Osmose 398 Electric Pen 405 Electric Pendulum 405 Electric Piano 415 Electric Picture 415 Electric Pistol 416 Electric Popgun 282 Electric Portrait 415 Electric Potential Difference 429 Electric Potential, Unit of 432 Electric Power 433 Electric Pressure 434 Electric Probe 435 Electric Prostration 437 Electric Protector 437 Electric Radiometer 447 Electric Ray 450 Electric Rectification of Alcohol 18 Electric Reduction of Ores 453 Electric Reduction of Phosphorous 410 Electric Register 454 Electric Residue 116, 460 Electricity, Resinous 461 Electric Resonance 468 Electric Resonator 470 Electric Rings 392 Electrics 208 Electric Saw 476 Electric Screen, 476 Electric Shadow 480 Electric Shock 482 Electric Shower Bath 57 Electric Soldering 487 Electric Spark, Duration of 490 Electric Sphygmophone 491 Electric Storms 495 Electric Striae 496 Electric Subway 496 Electric Subway, Underground 552 Electric Sunstroke 497 Electric Superficial Density 180 Electric Swaging 499 Electric Tele-barometer 504 Electric Telemanometer 521 Electric Telemeter 521 Electric Tempering 527 Electric Tension 529 Electric Thermometer 535 Electric Thermostat 537 Electric Torpedo 543 Electric Tower 545 Electric Transmission of Energy 240 Electric Trumpet 550 Electric Tube 550 Electric Typewriter 551 Electric Unit of Work 580 Electric Varnish 559 Electric Welding 574 Electric Whirl 577 Electric Wind 578 Electrification 208 Electrification by Cleavage 127 Electrification by Pressure 434 Electrified Body, Energy of an . 241 Electrization 208 Electro-biology 208 Electro-capillarity 209 Electro-chemical Equivalents 209, 244 Electro-chemical Series 209 Electro-chemistry 209 Electro-culture 209 Electrode 210 Electrode, Indifferent 210 Electrodes, Erb's Standard of 210 Electrodes, Non-polarizable 210 Electrodes, Shovel 483 Electrode, Therapeutic 210 Electro-diagnosis 181, 210 Electro-dynamic 211 Electro-dynamic Attraction and Repulsion, 211 Electro-dynamic Rotation of Liquids 474 Electro-dynamometer, Siemens' 212 Electro-gilding 277 Electro-kinetic 211 Electrolier 212 Electrolysis 212 Electrolysis, Laws of 213 Electrolyte 214 Electrolytic Analysis 214 Electrolytic Cell 109 Electrolytic Clock 128 Electrolytic Conduction 215 Electrolytic Convection 149, 214 Electrolytic Deposit 180 Electrolytic Iron 308 Electrolytic Resistance 464 Electro-magnet 215, 337 Electro-magnet, Annular 216 Electro-magnet, Bar 217 Electro-magnet, Club-foot 217 Electro-magnet, Hinged 217 Electro-magnet, Hughes' 291 Electro-magnetic Ammeter 27 Electro-magnetic and Magnetic Equipotential Surface 244 Electro-magnetic Attraction and Repulsion 217 Electro-magnetic Brake 86 Electro-magnetic Clutch 128 Electro-magnetic Control 218 Electro-magnetic Eye 248 Electro-magnetic Field of Force 218 Electro-magnetic Force 260 Electro-magnetic Gun 282 Electro-magnetic Induction 218, 299 Electro-magnetic Inertia 305 Electro-magnetic Induction, Mutual 302 Electro-magnetic Interrupter for Tuning Fork 307 Electro-magnetic Leakage 219 Electro-magnetic Lines of Force 219 Electro-magnetic Liquids, Rotation of 475 Electro-magnetic Meter 375 Electro-magnetic Quantity 445 Electro-magnetic Quantity, Practical Unit of 445 Electro-magnetic Shunt .483 Electro-magnetic Stress 219, 496 Electro-magnetic Theory of Light 219 Electro-magnetic Unit of Energy 220 Electro-magnetic Vibrator 561 Electro-magnetic Waves, 573 Electro-magnet, Ironclad 219 Electro-magnetism 220 Electro-magnet, Joule's 337 Electro-magnet, Long Range 220 Electro-magnet, One Coil 219 Electro-magnet, Plunger 220 Electro-magnet, Polarized 220 Electro-magnets, Interlocking 221 Electro-magnets, Multiple Wire Method of Working 388 Electro-magnet, Stopped Coil 221 Electro-magnets, Surgical 222 Electro-mechanical Bell 80 Electro-mechanical Equivalent 244 Electro-medical Baths 222 Electro-medical Battery, Pulvermacher's 69 Electro-metallurgy 222 Electrometer 222 Electrometer, Absolute 222 Electrometer. Attracted Disc 223 Electrometer, Capillary 224 Electrometer Gauge 226 Electrometer, Lane's 226 Electrometer, Quadrant 226 Electrometer, Thermo- 536 Electrometer, Weight 223 Electro-motive Force 227 Electro-motive Force, Counter- 228 Electro-motive Force Curve 170 Electro-motive Force, Impressed 297 Electro-motive Force, Motor 384 Electro-motive Force. Oscillatory 398 Electro-motive Force, Transverse 549 Electro-motive Force, Unit 228 Electro-motive Intensity 228 Electro-motive Potential Difference 429 Electro-motive Series 228 Electro-motograph 229 Electro-motor 229 Electro-muscular Excitation 229 Electro-negative 229 Electro-optics 229 Electrophoric Action 230 Electrophorus 230 Electro-physiology 231 Electroplating 231, 418 Electroplating Dynamo 198 Electro-pneumatic Signals 231 Electropoion Fluid 232 Electro-positive 232 Electro-puncture 232 Electro-receptive 232 Electroscope 232 Electroscope, Bennett's 233 Electroscope, Bohenberger's 233 Electroscope, Condensing 233 Electroscope, Gold Leaf 233 Electroscope, Pith Ball 234 Electrostatic Attraction and Repulsion 234 Electrostatic Attraction and Repulsion. Coulomb's Law of 155 Electrostatic Circuit 123 Electrostatic Equipotential Surface 244 Electrostatic Field of Force 254 Electrostatic Force 260 Electrostatic Induction 302 Electrostatic Induction, Coefficient of 234 Electrostatic Induction, Mutual 303 Electrostatic Lines of Force 234 Electrostatic Quantity 445 Electrostatic Refraction 235 Electrostatics 235 Electrostatic Series 235 Electrostatic Stress 236, 496 Electrostatic Telephone 526 Electrostatic Voltmeter 571 Electro-thermal Equivalent 245 Electro-therapeutics or Therapy 236 Electrotonic State 493 Electrotonus 236 Electrotype 236 Element, Chemical 236 Element, Galvanic 264 Element, Mathematical 237 Element, Negative 390 Element of a Battery Cell 237 Element, Positive 277 Elements, Electrical Classification of 237 Elements, Magnetic 342 Elements of Battery 63 Elements, Thermo-electric 237 Element, Voltaic 237 Elias' Method of Magnetization 360 Elongation 237, 540 Elongation, Magnetic 344 Embosser, Telegraph 237 E. M. D. P. 238 E. M. F. 238 Energy 238 Energy, Atomic 238 Energy, Chemical 239 Energy, Conservation of 239 Energy, Degradation of 239 Energy, Electric 239 Energy, Electrical, Coefficient of 205 Energy, Electric Transmission of 240 Energy, Electro-magnetic, Unit of 220 Energy, Kinetic 241 Energy, Mechanical 241 Energy Meter 375 Energy, Molar 241 Energy, Molecular 241 Energy of an Electrified Body 241 Energy of Dielectric 183 Energy of Position 211 Energy of Stress 241 Energy, Physical 241 Energy, Potential, or Static 241 Energy, Radiant 446 Energy, Thermal 242 End-on Method 238 End or Pole, Marked 368 Endosmose, Electric 238 End Play 238 End, Unmarked 556 English Absolute or Foot Second Unit of Resistance 465 Engraving, Electric 245 Entropy 242 Entropy, Electric 242 Epinus Condenser 242 E. P. S. 243 Equator, Magnetic 344 Equator of Magnet 337 Equipotential 244 Equipotential Surface 498 Equipotential Surface, Electrostatic 244 Equipotential Surface, Magnetic and Electro-magnetic 244 Equalizer 243 Equalizer, Feeder 251 Equalizing Dynamo 198 Equivalent, Chemical 116, 244 Equivalent Conductors 146 Equivalent, Electro-thermal 245 Equivalent, Joule's 311 Equivalent Resistance 465 Equivalents, Electro-chemical 209, 244 Equivalent, Thermo-chemical 245 Equivalent, Water 572 Equivolt 245 Erb's Standard of Electrodes 210 Erg 245 Erg-ten 245 Error, Heating 286 Escape 245 Essential Resistance 465, 466 Etching, Electric 245 Ethene 397 Ether 246 Eudiometer 246 Evaporation, Electric 246 Ewing's Theory of Magnetism 356 Exchange, Telephone 246 Excitation, Electro-muscular 229 Excitability, Faradic 246 Excitability, Galvanic 247 Excitability of Animal System, Electric 247 Exciter 247 Exosmose, Electric 247 Expansion, Coefficient of 247 Expansion, Electric 247 Experiment, Franklin's 261 Experiment, Hall's 284 Experiment, Kerr's 312 Experiment, Matteueci's 369 Experiments, Hertz's 470 Experiment, Volta's Fundamental 567 Experiment with Frog, Galvani's 262 Exploder 247 Explorer 247 Exploring Coil 350 Explosive Distance 190 Extension Bell Call 248 Extension, Polar 423 External Characteristic 114 External Characteristic Curve 171 External Circuit 123 External Resistance 465, 467 Extinguisher, Automatic Electric Fire 257 Extra Current 162 Extra-polar Region 454 Eye, Electro-magnetic 248 Eye, Selenium 478

Facsimile Telegraph 510 Factor, Armature 45 Fahrenheit Scale 248 Fall of Potential 430 False Poles, Magnetic 350 Farad 248 Faraday, Effect 249 Faraday's Cube 249 Faraday's Dark Space 249, 489 Faraday's Disc 249 Faraday's Net 250 Faraday's Ring 473 Faraday's Transformer 250 Faraday's Voltameter 250 Faradic 250 Faradic Battery 63 Faradic Brush 251 Faradic Current 162 Faradic Excitability 246 Faradization 251 Faradization, Galvano- 265 Far Leading Dynamo 198 Fault of a Dynamo, Ironwork 308 Faults 251 Faults, Contact 147 Feed Clockwork 128 Feeder 251 Feeder, Equalizer 251 Feeder, Main or Standard 251 Feeder, Negative 251 Feeder, Neutral 251 Feeder, Positive 251 Feeder, Switch 500 Feet, Ampere 30 Ferranti Effect 251 Ferric Chloride Battery 63 Ferro-magnetic 252 Fibre and Spring Suspension 252 Fibre Suspension 252 Field, Air 252 Field, Alternating 252 Field and Armature Reaction of Dynamo, 450 Field, Controlling 148 Field, Deflecting 178 Field Density 252 Field, Distortion of 252 Field, Drag of 254 Field, Intensity of a Magnetic 306 Field Magnet 337 Field of Force . 254 Field of Force, Electro-magnetic 218 Field of Force, Electrostatic 254 Field of Force, Magnetic 344 Field of Force of a Current 255 Field of Force, Uniform 553 Field, Pulsatory 256 Field, Rotating 256 Field, Stray 256, 495 Field, Uniform 256 Field, Uniform Magnetic 345 Field, Waste 256 Figure of Merit 256 Figures, Haldat's 284 Figures, Lichtenberg's 327 Figures, Magnetic 345 Filament 256 Filament, Magnetic 345 Filaments, Paper 402 File, Circuit Breaker 121 Finder, Position 427 Finder, Range 447 Finder, Wire 580 Fire Alarm, Electric Automatic 257 Fire and Heat Alarm 17 Fire Extinguisher, Electric Automatic 257 Fire Cleansing 257 Fire, St. Elmo's 494 Fishing Box 311 Flashing in a Dynamo or Magneto-Electric Generator 257 Flashing of Incandescent Lamp Carbons 257 Flashing Over 258 Flash, Side 484 Flat Cable 96 Flat Coil 133 Flat Ring Armature 45 Flats 258 Flats in Commutator 140 Flexible Cord 152 Floating Battery, De la Rive's 179 Floating Magnets, Meyer's 370 Floor Matting, Electric 369 Floor Push 258 Fluid, Depolarizing 258 Fluid, Electric 258 Fluid, Electropoion 232 Fluid, Insulator. 306 Fluid, North Magnetic 357 Fluids, Magnetic 345 Fluid, South Magnetic 356 Fluid Theory, Single 486 Fluorescence 258 Flush Boxes 258 Fluviograph 259 Flux, Magnetic 345 Fly or Flyer, Electric 259 Foci Magnetic 259 Fog, Electric 259 Following Horns 259 Foot-candle 259 Foot, Mil- 379 Foot-pound 259 Foot-step 259 Force 259 Force, Annular 544 Force, Axial 544 Force, Centrifugal 112 Force, Coercive or Coercitive 131-471 Force, Controlling 148 Force, Counter-electro-motive 156 Force de Cheval 260 Force, Electro-magnetic 260 Force, Electro-motive 227 Force, Electro-motive, Transverse 549 Force, Electrostatic 260 Force, Field of 254 Force, Field of, of a Current 255 Force, Field of, Electrostatic 254 Force, Kapp Line of 312 Force, Lines of 330 Force, Magnetic 346 Force, Magnetic Field of 344 Force, Magnetic Lines of 348 Force, Magneto-motive 365 Force, Motor Electro-motive 384 Force of Polarization, Back Electro-motive 156 Force, Oscillatory, Electro-motive 398 Force, Photo-electro-motive 410 Forces, Composition of 260 Forces, Parallelogram of 260 Forces, Resolution of 261 Force, True Contact 549 Force, Tubes of 261 Force, Unit of 261 Forked Circuits 126 Fork, Tuning, Dynamo 202 Forming 261 Formula of Merit 256 Foucault Current 163 Foundation Ring 261 Fourth State of Matter 261 Frame 261 Frame, Resistance 465 Franklinic Current 163 Franklin's Experiment 261 Franklin's Plate 262 Franklin's Theory 262-486 Free Charge 115 Free Magnetism 356 Frequency 262 Frequency, High 289 Frictional Electricity 262 Frictional Electric Machine 333 Frictional Heating 262 Friction Gear, Magnetic 276 Friction, Magnetic 295-346 Fringe 262 Frog, Galvani's Experiment with 262 Frog, Rheoscopic 262 Frying 263 Fulgurite 263 Fuller's Battery 63 Fulminating Pane 262 Fundamental Unit 554 Furnace, Electric 263 Fuse Block 175 Fuse Board 263 Fuse Box 263 Fuse, Cockburn 263 Fuse, Electric 264 Fuse Links 330 Fuse, Safety 175-475

Galvanic 264 Galvanic Action, Volta's Law of 568 Galvanic Dosage 190 Galvanic Element 264 Galvanic Excitability 247 Galvanic or Voltaic Battery 76 Galvanic or Voltaic Circle 119 Galvanic or Voltaic Couple 156 Galvanic Polarization 265 Galvani's Experiment with Frog 262 Galvanism 265 Galvanization 265 Galvanization, Labile 265 Galvanized Iron 265 Galvano-cautery 109 Galvano-cautery, Chemical 265 Galvano-electric Cautery 109 Galvano-faradization 265 Galvanometer 265 Galvanometer, Absolute 266 Galvanometer, Aperiodic 266 Galvanometer, Astatic 266 Galvanometer, Ballistic 267 Galvanometer Constant 268 Galvanometer, Differential 268 Galvanometer, Direct Reading 269 Galvanometer, Marine 269 Galvanometer, Mirror 271 Galvanometer, Potential 269 Galvanometer, Proportional 269 Galvanometer, Quantity 269 Galvanometer, Reflecting 270 Galvanometer, Shunt 271-483 Galvanometer, Sine 271 Galvanometer, Tangent 272 Galvanometer, Torsion 273-544 Galvanometer, Upright 274 Galvanometer, Vertical 274 Galvanometer, Volt and Ampere Meter 274 Galvano-plastics 275 Galvano-puncture 232-275 Galvanoscope 275 Galvano-thermal Cautery 100 Gap, Spark 490 Gas Battery 63 Gas Battery, Grove's 281 Gas Burner, Electric 93 Gas, Carbonic Acid 108 Gas, Electrolytic 275 Gases, Magnetism of 357 Gases, Mixed 275 Gas Jet, Carcel 108 Gas, Olefiant 397 Gassing 275 Gassiot s Cascade 275 Gastroscope 275 Gas Voltameter 564 Gauge, Battery 64 Gauge, Electrometer 226 Gauss 275 Gauss' Principle 276 Gauss, Tangent Positions of 276 Gauze Brush, Wire 92 Gear, Magnetic 346 Gear, Magnetic Friction 276 Geissler Pump 437 Geissler Tubes 276 Generating Plate 277 Generator, Current 277 Generator Inductor 199 Generator, Magneto-electric 362 Generator, Magneto-electric, Flashing in a Dynamo or 257 Generator, Motor 384 Generator, Pyromagnetic. 442 Generators and Motors, Commutator of Current 140 Generator, Secondary 277-477 Geographic Meridian 372 German Mile Unit of Resistance 466 German Silver 277 German Standard Candle 99 Gilding, Electro- 277 Gilding Metal 277 Gimbals 278 Girder Armature 49 Glass 278 Globe or Globular Lightning 330 Glow Discharge 187 Gold 278 Gold Bath 279 Gold Leaf Electroscope 233 Gold Stripping Bath 279 Governor, Centrifugal 113 Governor, Rate 449 Graduator 279 Gram 280 Gram-atom 280 Gram-molecule 280 Graphite 280 Gravitation 280 Gravity, Acceleration of 280 Gravity Ammeter 27 Gravity Battery 64 Gravity, Centre of 112 Gravity Control 281 Gravity Drop Annunciator 35 Grease Spot 92 Green Vitriol 562 Grenet Battery 65 Grid 281 Grid Plug 420 Grip, Cable 96 Gross Efficiency 205 Ground 281 Grounded Circuit 123 Ground Plate 417 Ground Wire 281 Grove's Battery 65 Grove's Gas Battery 281 Guard Ring 282 Guard Tube 282 Gun, Electro-magnetic 282 Gutta Percha 282 Gyration, Centre of 112 Gyrostatic Action of Armatures 283

H 283 H Armature 49 Haarlem Magnet 337 Hair, Removal of, by Electrolysis 283 Haldat's Figures 284 Hall Effect 284 Hall Effect, Real 284 Hall Effect, Spurious 284 Halleyan Lines 308 Hall's Experiment 284 Halske's and Siemens' Battery 72 Hand Hole 190 Hanger Board 284 Hanger, Cable 96 Hanger, Cable, Tongs 97 Harcourt's Pentane Standard 406 Hare's Deflagrator 73 Harmonic 23 Harmonic Curve 174, 485 Harmonic Motion, Simple 486 Harmonic Receiver 284, 451 Head Bath, Electric 284 Head-light, Electric 285 Head, Torsion 544 Heat 285 Heat and Fire Alarm 17 Heat, Atomic 52, 285 Heat, Electric 285 Heat, Electric, Convection of 149, 286 Heat, Irreversible. 286 Heat, Mechanical Equivalent of 286 Heat, Molecular 286 Heat, Specific 286 Heat, Specific, of Electricity 288 Heat Units 288 Heater, Electric 286 Heating, Admiralty Rules of 12 Heating Error 286 Heating, Frictional 262 Heating Magnet 286 Heavy Carburetted Hydrogen, 397 Hecto 288 Hedgehog Transformer 548 Heliograph 288 Helix 288 Henley's Universal Discharger 189 Henry 288 Henry's Coils 138 Hermetically Sealed 289 Hertz's Experiments 470 Heterostatic Method 280 Hexode Working 581 High Bars of Commutator 289 High Frequency 289 High Vacuum 557 Hinged Armature 45 Hinged Electro-magnet 217 Hissing 289 Hittorf's Resistance 466 Hittorf's Solution 289 Hoffer's Method of Magnetization 360 Hole Armature 45 Hole, Hand 190 Holders 289 Holder, Brush 91 Holder, Candle 99 Holders, Carbon 107 Holophote Lamp 321 Holtz's Influence Machine 334 Home Station 493 Hood 290 Horizontal Induction 302 Horns 290 Horns, Driving 132 Horns, Following 259 Horns, Leading 324 Horns, Trailing 259 Horse Power 290 Horse Power, Actual 290 Horse Power Curve 171 Horse Power, Electric 290 Horse Power Hour 290 Horse Power, Indicated 290 Horseshoe Magnet 337 Hour, Ampere- 30 Hour, Horse Power 290 H. P. 290 Hughes' Electro-magnet 291 Hughes' Induction Balance 291 Hughes' Sonometer 488 Hughes' Telegraph 511 Hughes' Theory of Magnetism 357 Hughes' Type Printer 511 Human Body, Resistance of 467 Hydrochloric Acid Battery 66 Hydro-electric 293 Hydro-electric Machine 293 Hydrogen 294 Hydrogen, Carburetted, Heavy 397 Hydrometer, Beaumé 78 Hygrometer 294 Hyperbolic Logarithms 389 Hysteresis 295 Hysteresis, Magnetic 294 Hysteresis, Static 295 Hysteresis, Viscous 295, 356

Idioelectrics 295 Idiostatic Method 295 Idle Coils 295 Idle Poles 296 Idle Wire 291 Igniter 296 I. H P. 296 Illuminating Power 296 Illuminating Power, Spherical 296 Illuminating Power, Standard of, Viole's 561 Illumination, Unit of 296 Image, Electric 296 Imbricated Conductor 146 Immersion, Simple 185 Impedance 297, 462 Impedance, Impulsive 297 Impedance, Oscillatory 297 Impressed Electro-motive Force 297 Impulse 297 Impulsive Discharge 188 Impulsive Impedance 297 In-and-out, Soaking 486 Incandescence, Electric 297 Incandescent Lamp 321 Incandescent Lamp Carbons, Flashing of 257 Incandescent Lamp, Chamber of 113 Incandescent Lamp, Life of 327 Incandescent Lamp, Three Filament 322 Inclination Compass 142 Inclination, Magnetic 346 Inclination Map 297 Inclination or Dip, Angle of 33 Incomplete Circuit 125 Increment Key 314 Independence of Currents in Parallel Circuits 297 India Rubber 102 Indicated Horse Power 290 Indicating Bell 80, 297 Indicator 298 Indicator, Circuit 298 Indicator, Throw-back 540 Indicator, Volt 568 Indifferent Electrode 210 Indifferent Point 421 Induced Current 163 Induced Magnetization, Coefficient of 354, 359 Inductance 298 Inductance Balance 293 Inductance Bridge 293 Induction, Anti-, Conductor 36 Induction, Back 55 Induction Balance, Hughes 291 Induction, Coefficient of Magnetic 349 Induction, Coefficient of Mutual 301 Induction, Coefficient of Self- 298 Induction Coil 133 Induction Coil, Inverted 136 Induction Coil, Telephone 137, 526 Induction, Cross 298 Induction Current 163 Induction, Electro-magnetic 218, 299 Induction, Electrostatic 302 Induction, Electrostatic, Coefficient of 234 Induction, Horizontal 302 Induction, Lateral 302 Induction, Lines of 330 Induction, Magnetic 302, 346 Induction, Magnetic, Apparent Coefficient of 346 Induction, Magnetic, Coefficient of 346 Induction, Magnetic Dynamic 347 Induction, Magnetic, Self- 352 Induction, Magnetic Static 347 Induction, Magnetic, Tube of 347 Induction, Mutual, Electro-magnetic 302 Induction, Mutual, Electrostatic 303 Induction, Open Circuit 303 Induction, Oscillatory 398 Induction Protector, Mutual 481 Induction, Self- 303 Induction Sheath 303 Induction. Unipolar 304 Induction, Unit of Self- 304 Induction, Vertical 304 Inductive Capacity, Magnetic 346, 349 Inductive Effect, Counter- 204 Inductive Resistance 466 Inductophone 304 Inductor 305 Inductor Dynamo 199 Inductor Generator 199 Inductor, Magneto- 363 Inductor, Pacinotti's 400 Inductorium 138 Inertia 305 Inertia, Electro-magnetic 305 Inertia, Magnetic 347 Infinity Plug 305, 420 Influence, Electric 305 Influence Machine 334 Influence Machine, Armature of 46 Influence Machine, Holtz 334 Influence, Magnetic 346 Installation 305 Instantaneous Capacity 102 Insulating Stool 305 Insulating Tape 305 Insulating Varnish 306 Insulation, Electric 305 Insulation, Magnetic 347 Insulation, Oil 396 Insulation Resistance 466 Insulator 306 Insulator Caps 306 Insulator, Fluid 306 Insulator, Line or Telegraph 306 Intensity 306 Intensity Armature 45 Intensity Current 163 Intensity, Electro-motive 228 Intensity, Magnetic 348 Intensity of a Magnetic Field 306 Intensity of Magnetization 360 Intensity, Poles of 426 Inter-air Space 489 Intercrossing 307 Interference, Armature 45 Interferric Space 489 Interior Pole Dynamo 191 Interlocking- Electro-magnets. 229 Intermediate Metals, Law of 323 Intermittent, 307 Internal Characteristic 114 Internal Resistance 466 lnterpolar Conductor 307 Interpolar Region 307 Interpolation 307 Interrupter, Electro-magnetic, for Tuning Fork 307 Intrinsic Efficiency 205 Invariable Calibration 97 Inverse Induced Current 163 Inverse Squares, Law of 323 Inversion, Thermo-electric 533 Ions 307 Iron 308 Ironclad Dynamo 200 Ironclad Electro-magnet, 219 Ironclad Magnet 356 Iron Disc Ammeter, Eccentric 27 Iron, Electrolytic 308 Iron, Galvanized 265 Ironwork Fault of a Dynamo 308 Irreversible Heat 286 Isochasmen Curve 171 Isochronism 308 Isoclinic Lines 308 Isoclinic Map 308 Isodynamic Lines 308 Isodynamic Map 308 Isoelectric Points 422 Isogonal Lines 308 Isogonic Map 309 Isolated Distribution 309 Isolated Plant 309 Isolated Supply 309 Isotropic 309 Isthmus Method of Magnetization 360 I. W. G., 309

J 309 Jablochkoff Candle 160 Jack. Spring- 492 Jacketed Magnet 356 Jacobi's Law 309 Jacobi's Method of Magnetization 360 Jacobi's Unit of Current 163 Jacobi's Unit of Resistance 466 Jamin Candle 100 Jar, Leyden 325 Jar, Lightning 330 Jar, Luminous 332 Jars, Leyden, Charging and Discharging 108 Jar, Unit 554 Jewelry 309 Joulad 311 Joule 311 Joule Effect 311 Joule's Electro-magnet 337 Joule's Equivalent, 311 Joint, American Twist 309 Joint, Britannia 309 Joint, Butt 310 Joint Current 160 Joint, Lap 310 Joint, Marriage 310 Joint, Resistance 464 Joints in Belts 311 Joint, Sleeve 310 Joint, Splayed 311 Junction Box 311 Junction, Thermo-electric 533

K. 311 Kaolin 311 Kapp. Line of Force 312 Kathelectrotonus 312 Kathode 312 Kathodic Closure Contraction 312 Kathodic Duration Contraction 312 K. C. C. 312 K. D. C. 312 Kempe's Discharge Key 315 Keeper 312 Kerr Effect 235, 312 Kerr's Experiment 312 Key 313 Key Board 313 Key, Bridge 313 Key, Double Contact 314 Key, Double Tapper 314 Key, Charge and Discharge 313 Key, Increment 314 Key, Kempe's Discharge 315 Key, Magneto-electric 315 Key, Make and Break 316 Key, Plug 316 Key, Reversing 316 Key, Sliding-contact 316 Key, Telegraph 316 Kicking Coil 132 Kilo 316 Kilodyne 316 Kilogram 317 Kilojoule 317 Kilometer 317 Kilowatt 317 Kine 317 Kinnersley's Thermometer 536 Kinetics, Electro- 211 Kinetic Energy 241 Kirchoff's Laws 317 Knife Break Switch 501 Knife Edge Suspension 317 Knife Edge Switch 501 Knife Switch 501 Knot 317 Kohlrausch's Law 317 Kookogey's Solution 318 Krizik's Cores 318

L 318 Lag, Angle of 33, 318 Lag, Electric 332 Lag, Magnetic 348 Lalande & Chaperon Battery 69 Lalande-Edison Battery 69 Lamellar Distribution of Magnetism 357 Laminated 318 Laminated Core 154 Laminated Core, Tangentially 155 Lamination 318 Lamination of Armature Conductors 319 Lamination of Magnet 361 Lamp, Arc 319 Lamp, Arc, Double Carbon 191 Lamp Carbons, Flashing of Incandescent 257 Lamp, Carcel 108 Lamp, Contact 320 Lamp, Differential Arc 320 Lamp Globe, Waterproof 572 Lamp, Holophote 321 Lamp-hour 321 Lamp, Incandescent 321 Lamp, Incandescent, Chamber of 113 Lamp, Incandescent, Three Filament 322 Lamp, Life of Incandescent 327 Lamp, Lighthouse 322 Lamp, Monophote 321 Lamp, Pilot 323 Lamp, Polyphote 323 Lamp, Semi-Incandescent 323 Lamp-socket 323 Lamps, Bank of 323 Lane's Electrometer 226 Langdon Davies' Rate Governor or Phonophone 450 Lenz's Law 325 Lap Joint 310 Lap Winding 570 Latent Electricity 323 Lateral Discharge 188 Lateral Induction 302 Latitude, Magnetic 348 Law, Jacobi's 309 Law, Kohlrausch's 317 Law, Lenz's 325 Law of Angular Currents 165 Law of Electrolysis 213 Law of Intermediate Metals 323 Law of Inverse Squares 323 Law of Magnetic Attraction and Repulsion. Coulomb's 338 Law of Successive Temperatures 324 Law, Magnus' 367 Law, Ohm's 396 Law, Pflüger's. 409 Law, Right Handed Screw 324 Law, Sine 486 Laws, Kirchoff's 317 Laws of Thermo-electricity, Becquerel's 78 Law, Tangent 502 Law, Voltametric 567 Lead 324 Lead, Angle of 33 Lead Chloride Battery 66 Lead of Brushes 90 Lead of Brushes, Negative 324 Lead, Peroxide of, Battery 69 Lead Sulphate Battery 66 Lead Tee 504 Leading Horns 324 Leading-in Wires 324 Leak 324 Leakage 324 Leakage Conductor 325 Leakage, Electro-magnetic 219 Leakage, Magnetic. 348 Leakage, Surface 498 Leclanché Agglomerate Battery 66 Leclanché Battery 66 Leg of Circuit 325 Legal Ohm 395 Legal Quadrant 444 Legal Volt 568 Length of Spark 490 Letter Boxes, Electric 325 Leyden Jar 325 Leyden Jar, Armature of 46 Leyden Jars, Battery of 68 Leyden Jars, Charging and Discharging 108 Leyden Jars, Sir William Thomson's 326 Lichtenberg's Figures 327 Life Curve 171 Life of Incandescent Lamp 327 Light, Electro-magnetic, Theory of 219 Light, Maxwell's Theory of 369 Lighthouse Lamp 322 Lightning 327 Lightning Arrester 328 Lightning Arrester, Counter-electro-motive Force 329 Lightning Arrester Plates 329 Lightning Arrester, Vacuum 329 Lightning, Ascending 330 Lightning, Globe or Globular 330 Lightning Jar 330 Lightning, Back Stroke or Shock of 55 Lime, Chloride of, Battery 61 Limit, Magnetic 348 Limit of Magnetization 361 Linear Current 164 Lineman's Detector 180 Line of Commutator, Neutral 300 Line of Contact 330 Line of Force, Kapp 312 Line of Magnet, Neutral 361 Line or Telegraph Insulator 306 Lines, Halleyan 308 Lines, Isoclinic 308 Lines, Isodynamic 308 Lines, Isogonal 308 Lines, Isogonic 308 Lines of Force 330 Lines of Force, Cutting of 175 Lines of Force, Electro-magnetic 219 Lines of Force, Electrostatic 234 Lines of Force, Magnetic 348 Lines of Induction 330 Lines of Slope 330 Lines or Points of Least Sparking 490 Lines, Trunk 550 Links, Fuse 330 Liquids, Electro-dynamic Rotation of 474 Liquids, Electro-magnetic Rotation of 475 Liquor, Spent 491 Listening Cam 330 Lithanode 331 Load 331 Load Curve 172 Load of Armature 46 Local Action 331 Local Battery 331 Local Circuit 331 Local Currents 163, 331 Localization 331 Locus 331 Lodestone 332 Logarithm 332 Logarithms, Hyperbolic 389 Logarithms, Napierian 389 Local Battery 66 Long Coil Magnet 361 Long Range Electro-magnet 220 Long Shunt and Series Winding 579 Long Shunt Winding 579 Loop 332 Loop Break 332 Loop, Circuit 125 Loop, Drip 192 Lost Amperes 30 Lost Volts 571 Low Vacuum 557 Luces 332 Luminous Jar 332 Luminous Pane 401 Luminous Tube 550 Lux 332

M 332 Machine, Cylinder Electric 333 Machine, Electric, Wimshurst 577 Machine, Frictional Electric 333 Machine, Holtz Influence 334 Machine, Hydro-electric 293 Machine, Influence 334 Machine, Nairne's Electrical 389 Machine, Plate Electrical 417 Machine, Rheostatic 472 Machine, Toeppler-Holtz 334 Machine, Wimshurst 335 Mack 335 Magic Circle 119 Magne-crystallic Action 335 Magnet 335 Magnet, Anomalous 335 Magnet, Artificial 335 Magnet, Axial 336 Magnet, Bar 336 Magnet, Bell Shaped 336 Magnet Coils, Sheath for 481 Magnet, Compensating 336 Magnet, Compound 336 Magnet, Controlling 185, 336 Magnet, Damping 336 Magnet, Deflection of 337 Magnet, Directing 185 Magnet, Electro- 215, 337 Magnet, Equator of 337 Magnet, Field 337 Magnet, Haarlem 337 Magnet, Heating 286 Magnet, Horseshoe 337 Magnet, Ironclad 356 Magnet, Joule's Electro- 337 Magnet-keeper 361 Magnet, Lamination of 361 Magnet, Long Coil 361 Magnet, Natural 361 Magnet, Neutral Line of 361 Magnet, Normal 361 Magnet Operation 365 Magnet, Permanent 365 Magnet Pole 365 Magnet, Portative Power of 366 Magnet, Projecting Power of a 435 Magnet, Relay 457 Magnet, Simple 366 Magnet, Solenoidal 366 Magnet, Sucking 366 Magnet, Unipolar 366 Magnet Coil 336 Magnet Core 336 Magnet Poles, Secondary 366 Magnet Pole, Unit 366 Magnetic Adherence 338 Magnetic and Electro-magnetic Equipotential Surface 244 Magnetic Attraction 338 Magnetic Attraction and Repulsion, Coulomb's Law of 338 Magnetic Axis 338 Magnetic Azimuth 338 Magnetic Battery 338 Magnetic Bridge 338 Magnetic Circuit 340 Magnetic Circuit, Curve of Saturation of 174 Magnetic Concentration of Ores 340 Magnetic Concentrator 340 Magnetic Continuity 340 Magnetic Conductance and Conductivity 340 Magnetic Control 341 Magnetic Couple 341 Magnetic Creeping 341 Magnetic Curves 341 Magnetic Cut Out 175 Magnetic Declination 342 Magnetic Density 342 Magnetic Dip 342, 346 Magnetic Discontinuity 342 Magnetic Double Circuit 340 Magnetic Eye, Electro- 248 Magnetic Elements 342 Magnetic Elongation 344 Magnetic Equator 344 Magnetic False Poles 350 Magnetic, Ferro- 252 Magnetic Field, Intensity of a 306 Magnetic Field of Force 344 Magnetic Field, Uniform 345 Magnetic Figures 345 Magnetic Filament 345 Magnetic Fluid, North 357 Magnetic Fluids 345 Magnetic Flux 345 Magnetic Force 346 Magnetic Friction 295, 346 Magnetic Friction Gear 276 Magnetic Fluid, South 356 Magnetic Foci 259 Magnetic Gear 346 Magnetic Hysteresis 294 Magnetic Inclination 346 Magnetic Induction 302 Magnetic Induction, Apparent Coefficient of 346 Magnetic Induction, Coefficient of 346-349 Magnetic Induction, Dynamic 347 Magnetic Induction, Static 347 Magnetic Induction, Tube of 347 Magnetic Inductive Capacity 349 Magnetic Inertia 347 Magnetic Influence 346 Magnetic Insulation 347 Magnetic Intensity 348 Magnetic Lag 348 Magnetic Latitude 348 Magnetic Leakage 348 'Magnetic Limit 348 Magnetic Lines of Force 348 Magnetic Mass 349 Magnetic Matter 349 Magnetic Memory 349 Magnetic Meridian 349 Magnetic Moment 349 Magnetic Needle 349 Magnetic Needle, Declination of the 178 Magnetic Needle, Dip of 185 Magnetic Needle, Oscillation of a 397 Magnetic Output 399 Magnetic Parallels 349 Magnetic Permeability 349 Magnetic Perturbations 350 Magnetic Poles 350 Magnetic Potential 350, 431 Magnetic Proof Piece 350 Magnetic Proof Plane 350 Magnetic Quantity 350 Magnetic Reluctance 351, 458 Magnetic Reluctivity 351 Magnetic Remanence 358 Magnetic Repulsion 338 Magnetic Resistance 458 Magnetic Retentivity 351 Magnetic Rotatory Polarization 351 Magnetic Saturation 251 Magnetic Screen 351 Magnetic Self-induction 352 Magnetic Separator 352 Magnetic Shell 352 Magnetic Shell, Strength of 352 Magnetic Shield 353 Magnetic Shunt 353 Magnetic Storms 353 Magnetic Strain 354 Magnetic Stress 354 Magnetic Susceptibility 254, 359 Magnetic Tick 354 Magnetic Top 542 Magnetic Twist 354 Magnetic Vane Ammeter 27 Magnetic Variations 354 Magnetism, Ampere's Theory of 354 Magnetism, Blue 355 Magnetism, Components of Earth's 356 Magnetism, Creeping of 356 Magnetism, Decay of 356 Magnetism, Discharge of 356 Magnetism, Electro 220 Magnetism, Ewing's Theory of 356 Magnetism, Free 356 Magnetism, Hughes' Theory of 357 Magnetism, Lamellar Distribution of 357 Magnetism of Gases 357 Magnetism, Red 357 Magnetism, Residual 358 Magnetism, Solenoidal Distribution of 358 Magnetism, Sub-permanent 358 Magnetism, Terrestrial 358 Magnetism, Weber's Theory of 358 Magnetization by the Earth 359 Magnetization by Double Touch 358 Magnetization by Separate Touch 359 Magnetization by Single Touch 359 Magnetization, Coefficient of Induced 359 Magnetization Curve 172 Magnetization, Cycle of 360 Magnetization, Elias' Method of 360 Magnetization, Hoffer's Method of 360 Magnetization, Intensity of 360 Magnetization, Isthmus Method of 360 Magnetization, Jacobi's Method 360 Magnetization, Limit of 361 Magnetization, Maximum 361 Magnetization, Specific 361 Magnetization, Surface 356 Magnetizing Coil 127 Magneto 361 Magneto Bell 80 Magneto Call Bell 361 Magneto-electric 361 Magneto-electric Brake 362 Magneto-electric Generator 362 Magneto-electric Generator, or Dynamo, Flashing in a 257 Magneto-electric Key 315 Magneto-electric Telegraph 512 Magnetograph 363 Magneto-inductor 363 Magnetometer 363 Magnetometer, Differential 365 Magnetometry 364 Magneto-motive Force 365 Magnetophone 367 Magnetoscope 365 Magnifying Spring Ammeter 28 Magnus' Law 367 Main Battery 66 Main Battery Circuit 125 Main Circuit 125 Main or Standard Feeder 251 Mains, Electric 367 Make 367 Make and Break Current 164, 367 Make and Break Key 316 Make-induced Current 163 Malapterurus 367 Map, Declination 309 Map, Inclination 297 Map, Isoclinic 308 Map, Isodynamic 308 Map, Isogonic 309 Marié Davy's Battery 67 Marine Galvanometer 269 Mariner's Compass 142 Marked End or Pole 368 Marriage Joint 310 Mass, Electric 368 Mass, Magnetic 349 Master Clock 127 Mathematical Element 237 Matteueci's Experiment 369 Matter, Electric 368 Matter, Fourth State of 261 Matter, Magnetic 349 Matter, Radiant 368 Matter, Ultra Gaseous 551 Matthiessen's Meter-gram Standard Resistance,. 466 Matthiessen's Unit of Resistance 466 Matting, Electric Floor 369 Maximum Magnetization 361 Maxwell's Theory of Light 369 Mayer's Floating Magnet 370 Maynooth's Battery 67 Measurement, Absolute 8 Measurements 370 Mechanical Equivalent of Heat 286 Mechanical Energy 241 Mechanical Equivalent, Electro- 244 Medical Battery 67 Medium, Polarization of the 424 Meg or Mega 370 Meidinger's Battery 68 Memoria Technica, Ampére's 30 Memory, Magnetic 349 Mercury 371 Mercury Bichromate, Battery 63 Mercury Circuit Breaker 121 Mercury Cups 371 Mercury, Sulphate of, Battery 67 Mercurial Air Pump 16 Meridian, Astronomical 372 Meridian, Geographic 372 Meridian, Magnetic. 349 Merit, Figure of 256 Merit, Formula of 256 Metal, Gilding 277 Metallic Arc 39 Metallic Circuit 125 Metallochromes 392 Metallurgy, Electro- 222 Metals, Law of Intermediate 323 Meter. Alternating Current 373 Meter, Ampere and Volt, Galvanometer . 274 Meter, Balance Ampere 391 Meter Bridge 373 Meter Bridge, Slide 486 Meter Candle 374 Meter, Chemical Electric 375 Meter, Current 375 Meter, Electro-magnetic 375 Meter, Energy 375 Meter Gram Standard Resistance, Matthiesen's 466 Meter-millimeter 375 Meter-millimeter Unit of Resistance 466 Meter, Neutral Wire Ampere. 391 Meter, Quantity 445 Meters. Ampere 39 Meter, Thermal-Electric 375 Meter, Time Electric 375 Meter, Watt 375 Method, Broadside 89 Method, Deflection 178 Method, End on 238 Method, Idiostatic 295 Method, Multiple Wire 388 Method, Null 393 Method of Magnetization, Elias' 360 Method of Magnetization, Isthmus 360 Method of Magnetization, Jacobi's 360 Methven Standard or Screen 376 Mho, 376 Mica 376 Mica, Moulded 376 Micro 376 Micrometer 376 Micrometer, Arc 39, 376 Micrometer, Spark 470 Micron 376 Microphone 376 Microphone Relay 377, 457 Microscope. Photo-electric 410 Microtasimeter 377 Mil 379 Mil, Circular 379 Mil-foot 379 Mil-foot Unit of Resistance 467 Milli 379 Milligram 379 Millimeter 379 Milli-oerstedt 380 Mil, Square 379 Minute, Ampere- 30 Mirror Galvanometer. 271 Mixed Gases 275 mm. 380 Molar 380 Molar Energy 241 Molecular Affinity 380 Molecular Attraction 380 Molecular Bombardment 380 Molecular Chain 380 Molecular Energy 241 Molecular Heat 286 Molecular Rigidity 380, 473 Molecular Shadow 480 Molecule 380 Moment 381 Moment, Magnetic 349 Moment of Couple 544 Moment, Turning 544 Monophote Lamp 321 Mordey Effect 381 Morse Receiver 381 Morse Recorder 451 Morse Telegraph 512 Mortar, Electric 382 Motion, Currents of 167 Motograph, Electro- 229 Motor. Compound or Compound Wound,. 382 Motor, Differential 382 Motor, Dynamo 200 Motor, Electric 382 Motor, Electro- 229 Motor, Electro-motive Force 384 Motor-generator 384 Motor, Multiphase 384 Motor, Overtype 399 Motor, Prime 385 Motor, Pulsating 386 Motor, Pyromagnetic 442 Motor, Reciprocating 385 Motor, Series 386 Motor, Shunt 386 Moulded Mica 376 Moulding 58 Movable Secondary 477 Mud, Battery 68 Multiphase Currents 166 Multiphase Motor 384 Multiple 386 Multiple Arc 387 Multiple Arc Box 387 Multiple Connected Battery 68 Multiple-series 387, 480 Multiple Switch 501 Multiple Switch Board 387 Multiple Transformer 548 Multiple Winding 579 Multiple Wire Method 388 Multiplex Harmonic Telegraph 510 Multiplex Telegraph 514 Multiplex Telegraphy 388 Multiplier, Schweigger's 476 Multiplying Power 347, 349 Multiplying Power of a Shunt 388 Multipolar Armature 46 Multipolar Dynamo 200 Multipolar Electric Bath 57 Multipolar Winding 579 Muscular Pile 388 Mutual Electro-magnetic Induction 302 Mutual Electrostatic Induction 303 Mutual Induction, Coefficient of 301 Mutual Induction Protector 481 Myria 388

Nairne's Electrical Machine 389 Napierian Logarithms 389 Nascent State 389 Natural Currents 166, 389 Natural Magnet 361 Needle 389 Needle Annunciator 35 Needle, Astatic 50 Needle, Dipping 185 Needle, Magnetic 349 Needle, Orientation of a Magnetic 397 Needle of Oscillation 389 Needle Telegraph, Single 519 Needle, Telegraphic 389 Negative Charge 389 Negative Current 164 Negative Electricity 389 Negative, Electro- 229 Negative Element 390 Negative Feeder 251 Negative Lead of Brushes 324 Negative Plate 417 Negative Pole 425 Negative Potential 432 Negative Side of Circuit 125 Nerve and Muscle Current 164 Nerve Currents 390 Net Efficiency 205 Net, Faraday's 250 Network 390 Neutral Armature 46 Neutral Feeder 251 Neutral Line of Commutator 390 Neutral Line of Magnet 361 Neutral Point 421 Neutral Point of Commutator 390 Neutral Point, Thermo-electric 390 Neutral Relay Armature 46, 390 Neutral Temperature 390 Neutral Wire 390 Neutral Wire Ampere Meter 391 N. H. P. 391 Niaudet's Battery 61 Nickel 391 Nickel Bath 391 Night Bell 392 Nitric Acid Battery 68 Nobili's Rings 392 Nodal Point 422 Nodular Deposit 392 Nominal Candle Power 101 Non-conductor 392 Non-essential Resistance 465-467 Non-inductive Resistance 467 Non-polar Dynamo 200 Non-polarizable Electrodes 210 Non-Polarized Armature 46 Normal Magnet 361 North Magnetic Fluid 357 North Pole 392 North Seeking Pole 393 Null Method 393 Null Point 422

Occlusion 393 Oerstedt 394 Oerstedt's Discovery 394 Oerstedt, Milli- 380 Ohm 394 Ohmage 394 Ohm, B. A. 394 Ohm, Board of Trade 394 Ohm, Congress 395 Ohmic Resistance 394, 467 Ohm, Legal 395 Ohmmeter 395 Ohm, Rayleigh 396 Ohm's Law 396 Ohm, True 396 Oil Insulation 396 Oil Transformer 548 Old Armature, Siemens' 49 Olefiant Gas 397 Omnibus Bar 94 Omnibus Rod 94 Omnibus Wire 94 One Coil Electro-magnet 219 Open 397 Open Circuit 125 Open Circuit Battery 68 Open Circuit Induction 303 Open Circuit Oscillation 397 Open Coil Armature 46 Open Coil Dynamo 200 Opening Shock 482 Operation, Magnet 365 Opposed Current 164 Optics, Electro- 229 Orders of Currents 167 Ordinate 397 Ordinates, Axis of 54, 397 Ores, Electric Reduction of 453 Ores, Magnetic Concentration of 340 Organ, Electric 397 Orientation of a Magnetic Needle 397 Origin of Co-ordinates 397 Oscillation, Centre of 112 Oscillation, Electric 398 Oscillation, Needle of 389 Oscillation, Open Circuit 397 Oscillatory 23 Oscillatory Discharge 188 Oscillatory Displacement 398 Oscillatory Electro-motive Force 398 Oscillatory Impedance 297 Oscillatory Induction 398 Osmose, Electric 398 Outlet 399 Output 399 Output, Magnetic 399 Output, Unit of 399 Over-compounding 399 Over, Flashing 258 Overflow Alarm 18 Over-house Telegraph 515 Overload 399 Overtype Dynamo or Motor 399 Oxide of Copper Battery 68 Ozone 399

Pacinotti's Inductor 400 Pacinotti's Ring 400 Pacinotti Teeth 400 Page Effect 401 Page's Revolving Armature 47 Paillard Alloys 400 Palladium 401 Pane, Fulminating 262 Pane, Luminous 401 Pantelegraphy 402, 510 Paper Filaments 402 Parabola 402 Parabolic Reflector 402 Paraffine 402 Paraffine Wax 402 Paragrêles 403 Parallax 403 Parallel 403 Parallel Circuits 123-126 Parallelogram of Forces 260 Parallels, Magnetic 349 Paramagnetic 403 Paramagnetism 404 Parasitical Currents 163 Parchmentizing 404 Partial Current 164 Partial Earth 203, 404 Partial Vacuum 557 Passive State 404 Path, Alternative 24 P. D. 404 Peltier's Cross 405 Peltier Effect 404 Pen, Electric 405 Pendant Cord 405 Pendulum Circuit Breaker 121 Pendulum, Electric 405 Pendulum or Swinging Annunciator 35 Pentane Standard, Harcourt's 406 Pentode Working 581 Percussion, Centre of 112 Perforated Armature 45 Perforated Core Discs 154 Perforator 407 Period 407 Period, Vibration 560 Periodic 23 Periodic Current, Power of 433 Periodicity 262, 408 Peripolar Zone 582 Permanency 408 Permanent Magnet 365 Permanent Magnet Ammeter 28 Permanent State 408 Permeability 346-349 Permeability-temperature Curve, 174 Permeameter 408 Permeance 408 Peroxide of Lead Battery 69 Perturbations, Magnetic 350 Pflüger's Law 409 Phantom Wires 409 Phase 409 Phase, Retardation of 471 Phenomenon, Porret's 427 Pherope 409, 527 Philosopher's Egg 409 Phonautograph, 409 Phone 409 Phonic Wheel 409 Phonograph 410 Phonophone or Rate Governor, Langdon Davies' 450 Phonozenograph 410 Phosphorescence 410 Phosphorous, Electrical Reduction of 410 Photo-electric Microscope 410 Photo-electricity 410 Photo-electro-motive Force 410 Photometer 411 Photometer, Actinic 411 Photometer, Bar 411 Photometer, Bunsen's 412 Photometer, Calorimetric 412 Photometer, Dispersion 412 Photometer, Shadow 414 Photometer, Translucent Disc 412 Photophore 415 Photo-voltaic Effect 415 Physical Energy 241 Physiology, Electro- 231 Piano, Electric 415 Pickle 415 Picture, Electric 415 Piece, Bed 78 Piece, Magnetic Proof 350 Piece, Pole 423 Pierced Core-discs, 152 Pile 415 Pile, Differential Thermo-electric 533 Pile, Muscular 388 Pile or Battery, Thermo-electric 530 Pilot Brush 91 Pilot Lamp 323 Pilot Transformer 415 Pilot Wires 415 Pistol, Electric 416 Pith 416 Pith Ball Electroscope 234 Pith-balls 416 Pivoted Armature 47 Pivot Suspension 416 Plane, Magnetic Proof 350 Plant 417 Plant Electricity 417 Plant, Isolated 309 Planté's Secondary Battery, 72 Plate, Arrester 417 Plate Condenser 417 Plate, Earth 203 Plate Electrical Machine 417 Plate, Franklin's 262 Plate, Generating 277 Plate, Ground 417 Plate, Negative 417 Plate, Positive 277, 417 Plating Balance 417 Plating Bath 418 Plating, Electro- 418 Platinized Carbon Battery 69 Platinoid 418 Platinum 419 Platinum Alloy 419 Platinum Black 419 Platinum Silver Alloy 419 Platinum Sponge 419 Play, End 238 Plow 420 Plücker Tubes 420 Plug 420 Plug Cut Out 175 Plug, Double 191 Plug, Grid 420 Plug, Infinity 305, 420 Plug Key 316 Plug Switch 420 Plumbago 421 Plunge Battery 69 Plunge 421 Plunger and Coil 131 Plunger and Coil, Differential 132 Plunger, Coil and 131 Plunger Electro-magnet 220 Pneumatic Battery 69 Pneumatic Signals, Electro- 231 P.O. 421 Pockets, Armature 47 Poggendorf's Solution 421 Point, Contact 147 Point, Indifferent 421 Point, Neutral 421 Point. Nodal 422 Point, Null 422 Point of Commutator, Neutral 390 Point Poles 422 Points, Consequent 422 Points, Corresponding 422 Points, Iso-electric 422 Points of Derivation 180, 423 Point, Thermo-electric Neutral 390 Polar Angle 423 Polar Extension 423 Polarity, Diamagnetic 181, 423 Polarity, Resultant 470 Polarization 423 Polarization, Back Electro-motive force of 156 Polarization Capacity 424 Polarization, Dielectric 183 Polarization, Galvanic 265 Polarization, Magnetic Rotary 351 Polarization of the Medium 424 Polarized Armature 47 Polarized Electro-magnet 220 Polarized Relay 458 Polarized Relay, Tongue of 542 Polarizing Current 164 Polar Region 424 Polar Span 424 Polar Span, Angle of 32, 423 Polar Tips 423 Polar Zone 582 Pole, Analogous 31, 425 Pole, Antilogous 425 Pole, Armature 47 Pole, Austral 54 Pole, Boreal 85 Pole Brackets, Telegraph 515 Pole Changer 425 Pole Changing Switch, 501 Pole Dynamo, Interior 199 Pole, Magnet 366 Pole, Negative 425 Pole, North 392 Pole, North-seeking 393 Pole or End, Marked 368 Pole Piece 423 Pole Pieces 425 Pole, Positive 425 Pole, Salient 426 Pole, Terminal 529 Pole Tips 290, 426 Pole, Traveling 426 Pole, Unit Magnet 366 Poles 425 Poles, Compensating 426 Poles, Consequent 146 Poles, Idle 296 Poles, Magnetic 350 Poles, Magnetic, False 350 Poles of Intensity 426 Poles of Verticity 426, 560 Poles, Point 422 Poles, Secondary 478 Poles, Secondary Magnet 366 Polyphase Currents 167 Polyphote Lamp 323 Popgun, Electric 282 Porous Cell 427 Porous Cup 159, 426 Porret's Phenomenon 427 Portative Power of Magnet 366 Portelectric Railroad 427 Portrait, Electric 415 Position, Energy of 241 Position Finder 427 Position, Sighted 484 Positive Current 164 Positive Direction 428 Positive Electricity 428 Positive Element 277 Positive Feeder 251 Positive Plate 277, 417 Positive Pole 425 Positive Potential 432 Positive Side of Circuit 125 Post Office 428 Posts, Binding, or Screws 81 Potential 428 Potential, Absolute 428 Potential, Constant 429 Potential Difference, Contact 147 Potential Difference, Electric 429 Potential Difference, Electro-motive 429 Potential, Electric Absolute 429 Potential, Fall of 430 Potential Galvanometer 269 Potential in Armature, Curve of Distribution of 172 Potential, Magnetic 350, 431 Potential, Negative 432 Potential or Static Energy 241 Potential, Positive 432 Potential Regulation, Constant 455 Potential, Unit of Electric 432 Potential, Zero 432, 582 Potentiometer 432 Poundal 433 Pound-foot 259 Power 438 Power, Candle 100 Power, Directive 187 Power, Electric 433 Power, Horse 290 Power, Illuminating 296 Power, Multiplying 349 Power of Magnet, Portative 366 Power of Periodic Current 433 Powers of Ten 527 Power, Stray 495 Power, Thermo-electric 533 Press Button 94 Pressel 434 Pressure 434 Pressure, Electric 434 Pressure, Electrification by 434 Primary 434 Primary Ampere-turns 31, 551 Primary Battery 69, 434 Prime 434 Prime Conductor 146, 434 Prime Conductor, Coatings of a 129 Prime Motor 385 Principle, Gauss' 276 Printing Telegraph 515 Probe, Electric 435 Projecting Power of a Magnet 435 Prony Brake 435 Proof Piece, Magnetic 350 Proof-plane 436 Proof Plane, Magnetic 350 Proof-sphere 436 Proportional Galvanometer 269 Proportionate Arms 436 Prostration, Electric 437 Protector, Body 84 Protector, Comb 437 Protector, Electric 437 Pull 437 Pulsatory Current 164 Pulsatory Field 256 Pulsating Motor 386 Pulvermacher's Electro-medical Battery 69 Pump, Geissler 437 Pump, Sprengel 439 Pump, Swinburne 440 Pumping 439 Puncture-electro 232 Puncture-galvano 232 Push Button 93. 98, 440 Push, Desk 180 Push, Floor 258 Pyro-electricity 441 Pyromagnetic Generator 442 Pyromagnetic Motor 441 Pyromagnetism 443 Pyrometer, Siemens' Electric 443

Q 443 Quad 288, 443 Quadrant 288, 443 Quadrantal Deviation 180 Quadrant, Legal 444 Quadrant, Standard 444 Quadrature 444 Quadruplex Telegraph 515 Qualitative 444 Quality of Sound 444 Quantitative 444 Quantity 444 Quantity Armature 47 Quantity, Electric 444 Quantity, Electro-magnetic 445 Quantity, Electro-magnetic, Practical Unit of 445 Quantity, Electrostatic 445 Quantity Galvanometer 269 Quantity, Magnetic 350 Quantity Meter 445 Quartz 445 Quicking 446

R 446 Racing of Motors 446 Radial Armature 47 Radian 446 Radiant Energy 446 Radiant Matter 368 Radiation 446 Radicals 446 Radiometer 447 Radiometer, Electric 447 Radio-micrometer 447 Radiophony 447 Railroad, Portelectric 427 Range Finder 447 Rate Governor 449 Rate Governor or Phonophone, Langdon Davies' 450 Rated Candle Power 101 Ratio Arms 437 Ratio, Core 154 Ratio, Shunt 483 Ratio, Velocity 560 Ray, Electric 450 Rayleigh Ohm 396 Reaction Coil 132 Reaction of a Dynamo Field and Armature 450 Reaction of Degeneration 179 Reactions, Anodic 36 Reactions, Armature 47 Reaction Telephone 527 Reaction Wheel 259 Reading Galvanometer, Direct 269 Reading, Sound 489 Reading Telescope 450 Real Efficiency of Secondary Battery 205 Real Hall Effect 284 Réaumur Scale 450 Recalescence 451 Receiver 451 Receiver, Harmonic 284, 451 Receiver, Morse 381 Receptive, Electro- 232 Recharge 115 Reciprocal 451 Reciprocating Motor 385 Recoil Circuit 125 Recorder, Chemical 117 Recorder, Morse 451 Recorder, Siphon 452 Record, Telephone 451 Rectification of Alcohol, Electric 18 Rectified Current 164 Rectilinear Current 165 Red Varnish 559 Red Magnetism 357 Redressed Current 165 Reduced Resistance 467 Reducteur for Ammeter 453 Reducteur for Voltmeter 453 Reduction of Ores, Electric 453 Reduction of Phosphorous, Electrical 410 Reflecting Galvanometer 270 Reflector, Parabolic 402 Refraction, Electric Double 454 Refraction, Electrostatic 235 Refreshing Action 454 Region, Extra-polar 454 Region, Intrapolar 307 Region, Polar 424 Register, Electric 454 Register, Telegraphic 454 Regulation, Constant Current 454 Regulation, Constant Potential 455 Regulation of Alternating Current Dynamo 195 Regulation of Dynamos 455 Reguline 456 Relative 456 Relative Calibration 98 Relay 456 Relay Bell 80 Relay Bells 457 Relay, Box Sounding 457 Relay Connection 457 Relay, Differential 457 Relay Magnet 457 Relay, Microphone 377, 457 Relay, Neutral, Armature 390 Relay, Polarized 457 Reluctance 458 Reluctance, Magnetic 351, 458 Reluctance, Unit of 438 Reluctivity 459 Reluctivity, Magnetic 351 Remanence 459 Remanence, Magnetic 358 Removal of Hair by Electrolysis 283 Renovate 115 Repeater 459 Repeater, Telegraph 518 Replenisher, Sir Wm. Thomson's 459 Repulsion, Magnetic 338 Repulsion and Attraction, Electrostatic 234 Repulsion and Attraction, Electro-magnetic 217 Reservoir, Common 460 Residual Atmosphere 460 Residual Capacity 103 Residual Charge 116 Residual Magnetism 358 Residue, Electric 116, 460 Resin 460 Resinous Electricity 461 Resistance 461 Resistance, Apparent 297, 462 Resistance, Assymmetrical 462 Resistance Box 462 Resistance, B. A. Unit of 462 Resistance Box, Sliding 463 Resistance, Breguet Unit of 463 Resistance Bridge 577 Resistance Coil 137 Resistance Coil, Standard 464 Resistance, Carbon 463 Resistance, Combined 464 Resistance, Compensating 144 Resistance, Critical 464 Resistance, Dielectric 183, 464 Resistance, Digney Unit of 464 Resistance, Electrolytic 464 Resistance, English Absolute or Foot-second Unit of 465 Resistance, Equivalent 465 Resistance, Essential 465 Resistance, External 465 Resistance Frame 465 Resistance, German Mile Unit of 466 Resistance, Hittorf's 466 Resistance, Inductive 466 Resistance, Insulation 466 Resistance, Internal 466 Resistance, Jacobi's Unit of 466 Resistance, Joint 464 Resistance, Magnetic 351, 458 Resistance, Matthiessen's Meter-gram Standard of 466 Resistance, Matthiessen's Unit of 466 Resistance, Meter-millimeter Unit of 466 Resistance, Mil-foot Unit of 467 Resistance, Non-essential 465, 467 Resistance, Non-inductive 467 Resistance of Human Body 467 Resistance, Ohmic 394, 467 Resistance, Reduced 467 Resistance, Siemens' Unit of 467 Resistance, Specific 467 Resistance. Specific Conduction 467 Resistance, Spurious 467 Resistance, Steadying 468 Resistance, Swiss Unit of 468 Resistance, Thomson's Unit of 468 Resistance to Sparking 490 Resistance, True 467 Resistance, Unit 468 Resistance, Unit of, B. A. 78 Resistance, Varley's 559 Resistance, Varley's Unit of 468 Resistance, Virtual 297 Resistance, Weber's Absolute Unit 468 Resolution of Forces 261 Resonator, Electric 468-470 Rest, Currents of 167 Resultant 470 Resultant Polarity 470 Retardation 470 Retardation of Phase 471 Retentivity 471 Retentivity, Magnetic 351 Retort Carbon 471 Return 471 Return Circuit 125 Return, Earth 203 Return Stroke 55 Reversal, Thermo-Electric 533 Reverse Current Working 581 Reverse-induced Current 163 Reverser, Current 165 Reversibility 471 Reversible Bridge 472 Reversing Key 316 Reversing Switch 501 Revivify 115 Revolving Armature, Page's 47 Rheochord 472 Rheometer 472 Rheomotor 472 Rheophore 472 Rheoscope 472 Rheoscopic Frog 262 Rheostat 472 Rheostat Arm 472 Rheostatic Machine 472 Rheostat, Wheatstone's 472 Rheotome 473 Rheotrope 473 Rhigolene 473 Rhumbs 473 Rhumkorff Coil 138, 473 Ribbon Coil 138 Ribbon Core 154 Right-handed Screw Law 324 Rigidity, Molecular 380, 473 Ring, Ampere 30 Ring Armature 48 Ring. Collecting 139 Ring Contact 473 Ring Core 155 Ring, Dynamo 200 Ring, Faraday's 473 Ring, Foundation 261 Ring, Guard 282 Ring, Pacinotti's 400 Rings, Electric 392 Rings, Nobili's 392 Ring, Split, Commutator 141 Roaring 474 Rocker 474 Rocker Arms 50, 474 Rod, Bus 94 Rod, Discharging 189 Rod, Omnibus 94 Roget's Spiral 474 Rolling Armature 49 Rosin 460 Rotary Polarization, Magnetic 351 Rotating Brush 91 Rotating Field 256 Rotation of Liquids, Electro-dynamic 474 Rotation of Liquids, Electro-magnetic 475 Rotatory Currents 167 Rubber 102, 475 Rubber, India 102

Saddle Bracket 475 Safety Catch 175 Safety Cut Out 175 Safety Device 475 Safety Fuse 175, 475 Safety Fuse, Plug, or Strip 475 Sal Ammoniac Battery 69 Salient Pole 426 Salt 475 Salt, Dronier's 192 Salt or Sea-salt Battery 69 Sand Battery 90 Saturated 476 Saturation, Magnetic 351 Saw, Electric 476 Scale, Fahrenheit 248 Scale, Réaumur 450 Scale, Tangent 502 Schweigger's Multiplier 476 Scratch Brushes 476 Screen, Electric 476 Screen, Magnetic 351 Screen, Methven 376 Screws or Posts, Binding 81 Sealed, Hermetically 289 Sea Salt or Salt Battery 69 Secohm 288 Second, Ampere- 30 Secondary Actions 477 Secondary Ampere-turns 31, 551 Secondary Battery 70 Secondary Battery, Efficiency of, Quantity 205 Secondary Battery, Planté's 72 Secondary Clock 127 Secondary Current 166 Secondary Generator 277, 477 Secondary Magnet Poles 366 Secondary, Movable 477 Secondary Plates, Colors of 478 Secondary Poles 478 Secretion Current 166 Section Trolley 549 Sectioned Coils 138 Seebeck Effect 478 Segments 56 Segments, Commutator 56 Selenium 478 Selenium Cell 478 Selenium Eye 478 Self-exciting Dynamo 201 Self-induction 303 Self-induction, Magnetic 352 Self-induction, Unit of 304 Self-repulsion 478 Self-winding Electric Clock 128 Semi-circular Deviation 181 Semi-conductors 478 Semi-incandescent Lamp 323 Sender, Zinc 582 Sensibility 479 Sensitiveness, Angle of Maximum 479 Separate Circuit Dynamo 201 Separate Touch 359, 479 Separate Touch, Magnetization by 359 Separately Excited Dynamo 201, 479 Separation of Electricities 479 Separator 479 Separator, Magnetic 352 Series 479 Series and Long Shunt Winding 579 Series and Separate Coil Winding 579 Series and Short Shunt Winding 580 Series, Contact 147 Series Dynamo 201 Series, Electro-chemical 209 Series, Electro motive 228 Series, Electrostatic 235 Series Motor 386 Series, Multiple- 387 Series-multiple 480 Series, Thermo-electric 534 Series Transformer 548 Series Winding 579 Service Conductors 480 Serving 480 Shackle 480 Shadow, Electric 480 Shadow, Molecular 480 Shadow Photometer 414 Sheath for Magnet Coils 481 Sheath for Transformers 481 Sheath, Induction 303 Sheet Current 166 Shell, Magnetic 352 Shell, Strength of Magnetic 352 Shellac 481 Shellac Varnish 481 Shield, Anti-magnetic 37 Shield, Magnetic 351, 353 Shielded 481 S. H. M. 482 Shock, Back, or Stroke of Lightning 55 Shock, Break 482 Shock, Electric 482 Shock, Opening 482 Shock, Static 482 Short Circuit 482 Short Circuit Working 482 Short Fall Air Pumps 16 Short Shunt Winding 579 Shovel Electrodes 483 Shower Bath, Electric 57 Shunt 483 Shunt Box 483 Shunt Circuit 123, 126 Shunt Dynamo 202 Shunt, Electro-magnetic 483 Shunt, Galvanometer 271, 483 Shunt, Magnetic 353 Shunt Motor 386 Shunt. Multiplying Power of a 388 Shunt Ratio 483 Shunt Winding 580 Shuttle Armature 49 Shuttle Current 483 Shuttle Winding 483, 580 Side Flash 484 Siemens and Halske's Battery 72 Siemens' Differential Voltameter 564 Siemens' Electro-dynamometer 212 Siemens' Old Armature 49 Siemens' Unit of Resistance 467 Sighted Position 484 Signaling, Velocity of 560 Signals, Electro-pneumatic 231 Signal, Telegraph 519 Silent Discharge 187, 189, 206 Silver 484 Silver Bath 484 Silver, German 277 Silver Stripping Bath 484 Silver Voltameter 565 Simple Arc 39 Simple Circuit 126 Simple Harmonic Motion 486 Simple Immersion 185 Simple Magnet 366 Simple Substitution 485 Sims-Edison Torpedo 543 Sine Curve 174, 485 Sine Galvanometer 271 Sine Law 486 Sines, Curve of 173, 485 Single Coil Dynamo 202 Single Curb Working 581 Single Fluid Theory 486 Single Fluid Voltaic Cell 486 Single Needle Telegraph 519 Single Touch, Magnetization by 359 Sinistrotorsal 486 Sinuous Current 166 Sinusoidal Curve 174, 485 Siphon Recorder 452 Sir William Thomson's Battery 72 Skin Effect 486 Skrivanow Battery 72 Sled 486 Sleeve, Joint 310 Slide, Balance 374 Slide Bridge 374 Slide Meter Bridge 486 Sliding Condenser 144 Sliding-contact Key 316 Sliding Resistance Box 463 Slope, Lines of 330 Smee's Battery 73 S. N. Code 486 Snap Switch 501 Soaking-in-and-out 486 Socket, Lamp 323 Socket, Wall 572 Soldering, Electric 487 Solenoid 487 Solenoid Ammeter 28 Solenoidal Distribution of Magnetism 358 Solenoidal Magnet 366 Solid Earth 203 Solutions, Battery, Chromic Acid 73 Solution, Chutaux's 119 Solution, Delaurier's 179 Solution, Hittorf's 289 Solution, Kookogey's 318 Solution, Poggendorf's 421 Solution, Striking 496 Solution, Tissandier's 542 Solution, Trouvé's 549 Sonometer, Hughes' 488 Sonorescence 488 Sound, Characteristics of 114 Sounder 488 Sounders, Tin 542 Sound, Quality of 444 Sound Reading 489 South Magnetic Fluid 356 Space, Clearance 489 Space, Crookes' Dark 489 Space, Dark, Faraday's 249, 489 Space, Faraday's Dark 249, 489 Space, Inter-air 489 Space, Interferric 489 Span, Polar 424 Span, Polar, Angle of the 32 Spark Arrester 489 Spark Coil 489 Spark Discharge 189 Spark, Duration of Electric 490 Spark Gap 490 Spark, Length of 490 Spark Micrometer 470 Spark Tube 491 Sparking 490 Sparking Distance 190 Sparking, Lines or Points of Least 490 Sparking, Resistance to 490 Specific Conduction Resistance 467 Specific Conductivity 145 Specific Heat 286 Specific Heat of Electricity 491 Specific Inductive Capacity 103 Specific Magnetization 361 Specific Resistance 467 Speech, Articulate 50 Speed, Critical 157 Spent Acid 491 Spent Liquor 491 Spherical Armature 49 Spherical Candle Power 101 Spherical Illuminating Power 296 Sphygmophone 491 Sphygmophone, Electric 491 Spiders 491 Spiral 492 Spiral Battery 73 Spiral, Roget's 474 Spiral Winding 492 Spirit Compass 143 Splayed Joint 311 Splice Box 492 Split Battery 73 Split Ring Commutator 141 Spluttering 492 Sponge, Platinum 419 Spot, Grease 92 Sprengel Pump 439 Spring Ammeter 28 Spring and Fibre Suspension 252 Spring-contact 148 Spring Control 492 Spring Jack Cut-out 493 Spurious Hall Effect 284 Spurious Resistance 467 Spurious Voltage 493 Square Mil 379 Square Wire 493 Squares, Law of Inverse 323 St. Elmo's Fire 494 Staggering 493 Standard Candle 101 Standard Candle, German 99 Standard, Harcourt's Pentane 406 Standard, Methven 376 Standard of Illuminating Power, Viole's 561 Standard or Main Feeder 251 Standard Quadrant 444 Standard Resistance Coil 464 Standard Voltaic Cell 109 Standard Voltaic Cell, Daniell's 109 Standard Voltaic Cell, Latimer Clark's. 110 State, Electrotonic 493 State, Nascent 389 State of Matter, Fourth 261 State, Passive 404 State, Permanent 408 Static Breeze 493 Static Condenser, Armature of 46 Static Electricity 493 Static Hysteresis 295 Static Induction, Magnetic 347 Static Shock 482 Station, Central 493 Station, Distant 493 Station, Home 493 Station, Transforming 494 Steadying Resistance 468 Steel 494 Steeling 494 Steel Yard Ammeter 28 Step-by-step Telegraph 506 Step-by-step Telegraphy 494 Step-down 494 Step, Foot- 259 Sticking 494 Stool, Insulating 305 Stopped Coil Electro-magnets 221 Stopping Off 495 Storage Battery 70 Storage Battery Changing Switch 501 Storage Battery, Planté's 72 Storage Capacity 105, 495 Storage of Electricity 495 Storms, Electric 495 Storms. Magnetic 353 Strain 495 Strain, Dielectric 183 Strain, Magnetic 354 Stranded Conductor Armature 49 Stranded Core 155 Stray Field 256, 495 Stray Power 495 Streamlets. Current 495 Strength, Dielectric 183 Strength of Magnetic Shell 352 Stress 495 Stress, Dielectric 496 Stress, Electro-magnetic 219, 496 Stress, Electrostatic 236, 496 Stress, Energy of 241 Stress, Magnetic 354 Striae, Electric 496 Striking Distance 496 Striking Solution 496 Stripping 496 Stripping Bath 57 Stripping Bath, Gold 279 Stripping Bath, Silver 484 Stroke, Back 55 Stroke or Shock of Lightning, Back 55 Stroke, Return 55 Sub-branch 496 Sub-main 496 Sub-permanent Magnetism 358 Substitution, Simple 485 Subway, Electric 496 Successive Temperatures, Law of 324 Sucking Coil 182 Sucking Magnet 366 Sulphate of Lead Battery 66 Sulphate of Mercury Battery 67 Sulphating 497 Sulphur Dioxide 497 Sulphuric Acid 497 Sulphuric Acid Voltameter 564 Sulphurous Acid Gas 497 Sunstroke, Electric 497 Superficial Density, Electric 180 Supersaturated, 497 Supply, Isolated 309 Surface 497 Surface Density 498 Surface, Equipotential 498 Surface Leakage 498 Surface Magnetization 356 Surgical Electro-magnet 222 Surging Discharge 188 Surveyors' Compass 143 Susceptibility, Magnetic 354, 359 Suspension 498 Suspension, Bifilar 498 Suspension, Fibre 252 Suspension, Knife Edge 317 Suspension, Pivot 416 Suspension, Spring and Fibre 252 Suspension, Torsion 545 Suspension Wire of Cable 97 Swaging. Electric 499 Swelling Current 167 S. W. G. 499 Swinburne Pump 440 Swinging Earth 203 Swinging or Pendulum Annunciator 35 Swiss Unit of Resistance 468 Switch 499 Switch, Automatic 500 Switch Board 500 Switch Board, Multiple 387 Switch Board, Trunking 550 Switch, Break-down 88 Switch, Changing 500 Switch, Changing Over 500 Switch, Circuit Changing 500 Switch, Double Break 500 Switch, Double Pole 500 Switch Feeder 500 Switch, Knife 501 Switch, Knife Break 501 Switch, Knife Edge 501 Switch, Multiple 501 Switch, Plug 420 Switch, Pole Changing 501 Switch, Reversing 501 Switch, Snap 501 Switch, Storage Battery Changing 501 Switch, Three Way 501 Switches, Distributing 190 Symmer's Theory 191 Sympathetic Vibration 501, 561 System, Block 83 System of Co-ordinates 150 System, Tower 545

T 501 Tailing Current 501 Tailings 501 Talk, Cross 158 Tamidine 502 Tangent Galvanometer 272 Tangent Law 502 Tangent Positions of, Gauss 276 Tangent Scale 502 Tangentially Laminated Core 155 Tank, Cable 97 Tape, Insulating 305 Tapper Key, Double 314 Teazer 504 Technica, Memoria, Ampére's 30 Tee, Lead 504 Teeth, Pacinotti 400 Tel-autograph 504 Tele-barometer, Electric 504 Telegraph, A. B. C. 504 Telegraph, Autographic 510 Telegraph, Automatic 504 Telegraph, Dial 505 Telegraph, Double Needle 506 Telegraph, Duplex 506 Telegraph, Duplex, Bridge 506 Telegraph, Duplex, Differential 507 Telegraph Embosser 237 Telegraph, Facsimile 510 Telegraph, Harmonic Multiplex 510 Telegraph. Hughes' 511 Telegraph Insulator 306 Telegraph Key 316 Telegraph, Magneto-electric 512 Telegraph, Morse 512 Telegraph, Multiplex 514 Telegraph, Single Needle 519 Telegraph, Overhouse 515 Telegraph Pole Brackets 515 Telegraph, Printing 515 Telegraph, Quadruplex 515 Telegraph Repeater 518 Telegraph Signal 519 Telegraph, Step-by-step 506 Telegraph, Wheatstone's, A. B. C. 521 Telegraph. Writing 521 Telegraphic Alphabet 19 Telegraphic Code 130, 511 Telegraphic Needle 389 Telegraphic Register 454 Telegraphy, Multiplex 388 Telegraphy, Step-by-step 494 Telemanometer, Electric 521 Telemeter, Electric 521 Telepherage 522 Telephone 522 Telephone, Bi- 524 Telephone, Capillary 525 Telephone, Carbon 525 Telephone, Chemical 526 Telephone, Electrostatic 526 Telephone Exchange 246 Telephone Induction Coil 137, 526 Telephone, Reaction 527 Telephone Record 451 Telephone, Thermo-electric 527 Telephone Tinnitus 542 Telephotography 521 Telephote 527 Telescope, Reading 450 Teleseme 527 Tele-thermometer 527 Terminal 529 Terminal Pole 529 Terminal Voltage 562 Temperature, Absolute 8 Temperature, Neutral 390 Temperatures, Laws of Successive 324 Tempering, Electric 527 Temporary Magnetism or Magnetization 357 Ten, Powers of 527 Tension 529 Tension, Disruptive 189 Tension, Electric 529 Terrestrial Magnetism 358 Tetanus, Acoustic 529 Tetrode Working 581 Theatrophone 529 Theory, Contact 148 Theory, Double Fluid 191 Theory, Franklin's 262 Theory of Dimensions 184 Theory of Light, Electro-magnetic 219 Theory of Light, Maxwell's 369 Theory of Magnetism, Ampére's 354 Theory of Magnetism, Ewing's 356 Theory of Magnetism, Hughes' 357 Theory of Magnetism, Weber's 358 Theory, Symmer's 191 Therapeutic Electrode 210 Therapeutics, Electro- 236 Therm 529 Thermaesthesiometer 530 Thermal Electric Meter 375 Thermal Equivalent, Electro- 245 Thermal Energy 242 Thermic Balance 85 Thermo Call 530 Thermo-chemical Battery 530 Thermo-chemical Equivalent 245 Thermo-electric Battery or Pile 530 Thermo-electric Call 531 Thermo-electric Couple 532 Thermo-electric Current 167 Thermo-electric Diagram 532 Thermo-electric Element 237 Thermo-electric Inversion 533 Thermo-electric Junction 533 Thermo-electric Neutral Point 390 Thermo-electric Pile, Differential 533 Thermo-electric Power 533 Thermo-electric Reversal 533 Thermo-electric Series 534 Thermo-electric Telephone 527 Thermo-electric Thermometer 535 Thermo-electricity 533 Thermo-electricity, Laws of, Becquerel's 78 Thermo-electricity, Volta's Law of 568 Thermo-electrometer 536 Thermolysis 535 Thermo-multiplier 536 Thermometer 535 Thermometer, Electric 535 Thermometer, Kinnersley's 536 Thermometer, Tele- 527 Thermometer, Thermo-electric 535 Thermophone 537 Thermostat, Electric 537 Third Brush 91 Thomson Effect 538 Thomson's Replenisher, Sir William 459 Thomson's Battery, Sir William 72 Thomson's Unit of Resistance 468 Three Filament Incandescent Lamp 322 Three Way Switch 501 Three Wire System 539 Throw 237, 540 Throw-back Indicator 540 Thrust Bearings 540 Thunder 540 Ticker 540 Tick, Magnetic 354 Timbre 444 Time Constant 541 Time Cut-outs 541 Time Electric Meter 375 Time-fall 541 Time-reaction 541 Time-rise 541 Tin 541 Tin Sounders 542 Tinnitus, Telephone 542 Tips, Polar 423 Tips, Pole 290, 426 Tissandier's Solution 542 Toeppler-Holtz Machine 334 Tongs, Cable Hanger 97 Tongs, Discharging 189 Tongue of Polarized Relay 542 Tongue of Polarized Relay, Bias of 542 Toothed Core-discs 154 Top, Magnetic 542 Torpedo, Electric 543 Torpedo, Sims-Edison 543 Torque 543 Torque, Curve of 174 Torricellian Vacuum 557 Torsion Balance, Coulomb's 544 Torsion Galvanometer 273, 544 Torsion Head 544 Torsion Suspension 545 Total Earth 203 Touch 545 Touch, Separate 479 Tourmaline 545 Tower, Electric 545 Tower System 545 Trailing Horns 259 Transformer 545 Transformer, Commuting 547 Transformer, Continuous Alternating 547 Transformer, Continuous Current 384, 547 Transformer, Core 547 Transformer, Faraday's 250 Transformer, Hedgehog 548 Transformer, Multiple 548 Transformer, Oil 548 Transformer, Pilot 415 Transformer, Series 548 Transformer. Sheath for 481 Transforming Station 494 Transformer, Welding 548, 575 Translator 519 Translucent Disc Photometer 412 Transmitter 548 Transmitter, Carbon 549 Transmission of Energy, Electric 240 Transposing 549 Transverse Electro-motive Force 549 Trap, Bug 92 Traveling Pole 426 Trembling Bell 78 Trolley 549 Trolley, Double 549 Trolley Section 549 Trough Battery 73 Trouvé's Blotting Paper Battery 73 Trouvé's Solution 549 True Contact Force 549 True Ohm 396 True Resistance 467 Trimmer, Brush 549 Trumpet, Electric 550 Trunk Lines 550 Trunking Switch Board 550 Tube, Electric 550 Tube, Guard 282 Tube, Luminous 550 Tube of Magnetic Induction 347 Tube, Spark 491 Tube, Stratification 495 Tubes, Geissler 276 Tubes of Force 261 Tubes, Plücker 420 Tubular Braid 550 Tubular Core 155 Tubular Magnet 356 Tuning Fork Circuit Breaker 121 Tuning Fork Dynamo 202 Tuning Fork, Interrupter for 307 Turning Moment 544 Turns 550 Turns, Ampere- 31 Turns, Dead, of a Dynamo 551 Turns, Primary Ampere- 551 Turns, Secondary Ampere- 551 Twist Joint, American 309 Twist, Magnetic 354 Tyer's Battery 74 Typewriter, Electric 551 Type Printer, Hughes' 511

Ultra-gaseous Matter 551 Unbuilding 552 Underground Conductor 552 Underground Electric Subway 552 Undulatory 23 Undulatory Current 167 Unidirectional 553 Uniform Field 256 Uniform Field of Force 553 Uniform Magnetic Field 345 Unipolar 553 Unipolar Armature 50, 553 Unipolar Current Induction 553 Unipolar Dynamo 202-553 Unipolar Electric Bath 57 Unipolar Induction 304 Unipolar Magnet 366 Unit 553 Unit, Absolute 554 Unit Angle 554 Unit. B. A. 554 Unit, B. A., of Resistance 462 Unit Current 167 Unit Electro-motive Force 228 Unit, Fundamental 554 Unit Jar 554 Unit Magnet Pole 366 Unit of Capacity 105 Unit of Conductivity 145 Unit of Electric Potential 432 Unit of Energy, Electro-magnetic 220 Unit of Force 261 Unit of Illumination 296 Unit of Output 399 Unit of Reluctance 458 Unit of Resistance, B. A. 78 Unit of Resistance, Breguet 463 Unit of Resistance, Digney 464 U nit of Resistance, English Absolute or Foot-second 465 Unit of Resistance, German Mile 466 Unit of Resistance, Jacobi's 466 Unit of Resistance, Meter-millimeter. 466 Unit of Resistance, Mil-foot 467 Unit of Resistance, Siemens' 467 Unit of Resistance, Swiss 468 Unit of Resistance, Thomson's 468 Unit of Resistance, Varley's 468 Unit of Self-induction 304 Unit of Supply 554 Unit of Work 581 Unit Resistance 468 Units, Circular 126, 555 Units, Derived 555 Units, Heat 288 Units, Practical 555 Universal Battery System 556 Universal Discharger 189 Unmarked End 556 Upright Galvanometer 274 Upward's Battery 75

V 556 V. A. 557 Vacuum 557 Vacuum, Absolute 557 Vacuum, High 557 Vacuum Lightning Arrester 329 Vacuum, Low 557 Vacuum, Partial 557 Vacuum, Torricellian 557 Valency 557 Valve, Electrically Controlled 558 Vapor Globe 558 Variable Conductivity 145 Variable Period 558 Variable State 558 Variation of the Compass 32, 558 Variations, Magnetic 354 Variometer 559 Varley's Battery 76 Varley's Condenser 559 Varley's Resistance 559 Varley's Unit of Resistance 468 Varnish 559 Varnish, Electric 559 Varnish, Insulating 306 Varnish, Red 559 Varnish, Shellac 481 Vat 559 Velocity 559 Velocity, Angular 32, 559 Velocity of Signaling 560 Velocity Ratio 560 Ventilation of Armature 560 Vertical Galvanometer 274 Vertical Induction 304 Verticity, Poles of 426, 560 Vibrating Bell 78 Vibration Period 560 Vibration, Sympathetic 501, 561 Vibrator, Electro-magnetic 561 Villari's Critical Value 561 Viole 562 Viole's Standard of Illuminating Power 561 Virtual Resistance 297 Viscous Hysteresis 295, 356 Vis Viva 562 Vitreous Electricity 562 Vitriol, Blue 562 Vitriol, Green 562 Vitriol, White 562 Volatilization of Carbon 108 Volt 562 Volt-ampere 573 Volt and Ampere Meter Galvanometer 274 Volt, B. A. 568 Volt, Congress 568 Volt, Coulomb 568, 573 Volt Indicator 568 Volt. Legal 568 Voltage 562 Voltage, Spurious 493 Voltage, Terminal 562 Voltaic 563 Voltaic Alternatives 563 Voltaic Arc 39 Voltaic Cell, Daniell's Standard 109 Voltaic Cell, Double Fluid 191 Voltaic Cell, Capacity of Polarization of a 103 Voltaic Cell, Single Fluid 486 Voltaic Cell, Standard 109 Voltaic Cell, Standard, Latimer Clark's 110 Voltaic Circuit 126 Voltaic Effect 563 Voltaic Electricity 563 Voltaic Element 237 Voltaic or Galvanic Battery 76 Voltaic or Galvanic Circle 119 Voltaic or Galvanic Couple 156 Voltameter 563 Voltameter, Copper 563 Voltameter, Differential, Siemens' 564 Voltameter, Faraday's 250 Voltameter, Gas 564 Voltameter, Silver 565 Voltameter, Sulphuric Acid 564 Voltameter, Volume 564 Voltameter, Weight 566 Voltametric Law 567 Volta's Battery 76 Volta's Fundamental Experiments 567 Volta's Law of Galvanic Action 568 Volta's Law of Thermo-electricity 568 Voltmeter 568 Voltmeter, Battery 569 Voltmeter, Cardew 569 Voltmeter, Electrostatic 571 Voltmeter, Reducteur for 453 Volts, Lost 571 Volume Voltameter 564 Vulcanite 571

W 572 Wall Bracket 572 Wall Socket 572 Ward 572 Waste Field 256 Water 572 Water Battery 77 Water Equivalent 572 Water Level Alarm 18 Waterproof Lamp Globe 572 Wattless Current 168 Watt 572 Watt-hour 573 Watt Meter 375 Watt-minute 573 Watt-second 573 Watts, Apparent 573 Wave Winding 580 Waves, Amplitude of 31 Waves. Electro-magnetic 573 Wax, Paraffine 402 Weber 574 Weber s Absolute Unit Resistance 468 Weber-meter 574 Weber's Theory of Magnetism 358 Wedge Cut-out 175 Wedge. Double 191 Weight, Atomic 53 Weight, Breaking 89 Weight Electrometer 223 Weight Voltameter 566 Welding, Electric 574 Welding Transformer 548, 575 Wheatstone's A. B. C. Telegraph 521 Wheatstone's Balance 577 Wheatstone's Bridge 575 Wheatstone's Bridge, Commercial 86 Wheatstone's Rheostat 472 Wheel, Phonic 409 Wheel, Reaction 259 Whirl, Electric 577 White Vitriol 562 Wilde Candle 101 Wimshurst Electric Machine 335, 577 Wimshurst Machine 335, 577 Wind, Electric 578 Windage 578 Windings, Ampere 31 Winding, Bifilar 81 Winding, Compound 578 Winding, Disc 579 Winding, Lap 579 Winding, Long Shunt 579 Winding, Long Shunt and Series 579 Winding, Multiple 579 Winding, Multipolar 579 Winding, Series 579 Winding, Series and Separate Coil 579 Winding, Series and Short Shunt 580 Winding, Short Shunt 579 Winding, Shunt 483, 580 Winding Shuttle 580 Winding, Wave 580 Winding Working, Differential 183 Wire, Block 83 Wire, Bus 94 Wire, Dead 177 Wire Finder 580 Wire Gauze Brush 92 Wire, Idle 296 Wire, Neutral 390 Wire, Omnibus 94 Wire, Square 493 Wire System, Three 539 Wires, Crossing 158 Wires, Leading-in 324 Wires, Phantom 409 Wires, Pilot 415 Wollaston Battery 78 Work 580 Work, Electric, Unit of 580 Work, Unit of 581 Working, Contraplex 580 Working, Diode 580 Working, Diplex 580 Working, Double Curb 581 Working, Hexode 581 Working, Pentode 581 Working, Reverse Current 581 Working, Single Curb 581 Working Tetrode 581 Writing Telegraph 521

X, Axis of 54

Y, Axis of 54, 397 Yoke 581

Zamboni's Dry Pile 581 Zero 581 Zero, Absolute 581 Zero Potential 432, 582 Zero, Thermometric 582 Zinc 582 Zinc Sender 582 Zincode 582 Zone, Peripolar 582 Zone, Polar 582

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