American telegraphy and encyclopedia of the telegraph; systems, apparatus, operation

Front matter

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Preface

Somewhat less than twenty-five years ago the simple Morse system of telegraphy was the only one in general use in America. One or two printing telegraph systems were in operation, and attempts were being made to utilize, satisfactorily, chemical automatic telegraph systems. At that time, although the duplex system ot telegraphy was in limited use, it had not been perfected, and in some quarters it was looked upon as a " scientific toy," *' very beautiful in its way but quite useless in a practical point of view."

Since then the duplex and quadruplex systems, and the Wheatstone automatic telegraph system, have been extensively introduced into the commercial telegraph service of this country. Since then, also, multiplex, phonoplex, burglar alarm, police signal and other analogous systems of telegraphy have been invented and placed in successful operation. Many important improvements in printing telegraphy, submarine telegraj^hy, fire alarm telegraphy, etc., have, in recent years, also been introduced, and in numerous other ways the art of electrical telegraphy has been advanced.

While a number of the systems and improvements referred to have, at different times, and at more or less length, been described in electrical books and periodicals, the writer is not aware that even a majority of them has been fully described in any one book, and thus a knowledge of them placed within easy reach of the ordinary student of telegraphy. " 'v • .,

Believing that such a book would be of value, the attempt has been made, in the present work, to supply a comprehensive account of the systems of telegraphy now in use in America, and as such an account naturally includes sources of electromotive force employed, line construction, line and apparatus testing, etc., those subjects have also been dwelt upon at some length.

As far as possible each subject has been treated from a practical standpoint, and the book, as a whole, has been written in a manner intended to be clear to novices in electrical matters, more especially those who are directly engaged in the practical working of electrical systems of telegraphy. To that end, where it has seemed essential to a proper understanding of a subject, full, and, it is hoped, accurate, explanations of laws and facts of electricity and m:igiietism involved in the operation of systems and methods described, have been given. In short, the object, however impervi PREFACE.

fectly carried out, has been to provide in this work a complete practical hand-book of telegraphy.

With but few exceptions the systems herein described are in actual operation. The exceptions relate to peculiar types of systems, a description of which was considered desirable for reference. In nearly every case the diagrams employed have been designed expressly for this book.

The author thankfully acknowledges his obligations to numerous friends for valuable practical information concerning a number of the systems herein described, and through their courtesy in that respect many details of certain systems are now given for the first time.

Preface To Fifth Edition

Advantage has been taken of tlie opportunity offered by the publication of the present new and much enlarged edition to add somcAvhat to the title of this work. This change has been suggested many times by friendly critics, it having been observed that the original title appeared to convey the idea, to those unfamiliar with its scope, that the work was confined to a treatment of Morse telegraphy, and perhaps some of its allied branches, whereas, in fact, the book is encyclopedical, treating not only of all that virtually appertains to telegraphy proper, but also of fire-alarm, police, burglar- alarm, and printing telegraphy; railroad block-sigualing; manufacture of telegraph wire ; electrical testing, etc. , etc.

It was originally iutended to limit this work to descriptions of systems in actual operation in this country, but in order that the book may now, as far as practicable, conform to its amplified title, descriptions of a number of telegraph systems, repeaters, etc., used in other countries have been added, together with descriptions of telegraph systems of recent application in this country and abroad, such as wireless telegraphy, etc. In many other ways, also, as by the sections on inductance, impedance, Gray's harmonic telegraph, the telautograph, etc., the author has endeavored to enhance the usefulness of the work as a book for students and as a work of reference, to which endeavor he has been in a measure prompted by the increasing use of the work by students generally, and as a text-book of Telegraph Engineering in colleges and other institutions of learning.

It may be noted that since the first edition of this work was printed over 90 pages of new matter (comprising about 60,000 words of text) and 60 illustrations have been added, mainly in the present edition. For synopsis of new matter see Supplemental Index, last page.

The author takes this occasion to express his appreciation of many kindly words which have reached him commendatory of this work, and would add that communications concerning subjects treated of herein are cordially invited.

18,8 Arlington Avenue, W. M., Jr.

Jersey City, N. J.

Contents

Page Introductory. , , , . . . * , ' • . , i , . xii

Chapter I

ELECTRICITY. I

Theories, Electrical Terms, Etc.

Chapter II. Primary Batteries. 9

Polarization.— The Gravity or Callaud Cell —The Care of,— The Use of Oil on. — Hydrometer.— The Leclanche Cell. — The Fuller Cell. — Chloride of Silver Cell. — The Edison-Lalande Cell. — The Burnley Dry Cell. — The Gassxer. — Arrangement of Cells in BATrERiES.-=»Cells in Series. — Cells in Multiple. — Cells in Opposition, Etc., Etc.

Chapter III. The Dynamo Machine In Telegraphy. 27

Introduction of in Telegraphy. — Joint Resistance of Circuits. — Distribution of Current In Divided Circuits, — The Dynamo-Electric Machine.— Theory of.— Methods of Arranging Dynamos in Telegraphy.— Western Union Arrangement, — Dynamo Reversing Switches. — Postal Arrangement, — Arrangement for Locals.— The Motor Dynamo.— The Storage Battery, Etc., Etc,

Chapter IV

Theory. — Operation of, — Closed Circuit Method. — Open Circuit Method. — Telegraph Codes, — Steno Telegraphy. Etc., Etc.— Practical Notes for Beginners.

Chapter V. Morse Telegraph Apparatus. 58

Keys.— Bunnell.— Steiner. — Victor,— Legless,— Self-Closing- - Relays,— Main Line — Pocket.— Pony— Box. — Sounders. — Local. — Bunnell — Western Electric — Victor. — Main Line Sounders, — Winding of Etc. — The Morse Register. — Ink Recording Morse Register.— Automatic Paper Winder. — Automatic Telegraph Sender. — Telegraph Transmitters — La Dow Transmitter. — Typewriter in Telegraphy. — Bunnell Sounder Resonator. — Switch Boards, — Main Office, — Single Spring Jack Boards. — Way Office Switch Board. — Way Office Cut Out.— Lightning Arresters, Etc.

Chapter VI

THE CONDENSER,— STATIC CHARGE,— DISTRIBUTION OF, ETC.— INDUCTION, MUTUAL,

SELF, ETC.— THE RHEOSTAT, 90

Adjustable Condenser. — Standard Condenser — Wheatstone Condenser. — Condensers Arranged in Multiple. — In Series —Electrification.— Static Charge,— Mutual Induction Between Parallel Wires, Etc.-^ Inductance, Capacity, Reactance, Impedance, Loaded Conductors, Rheostat.

Chapter VII. Galvanometers

Theory.— The Tangent Galvanometer.-^ Parallelogram of Forces. — Western Union Tangent Galvanometer.^ Astatic Galvanomet'ers.— Detector Galvanometek.— Tuomson Reflecting Galvanometer.— Shunts,— Directing Magnet.— D'Aksonvall Galvanometer.— Table of Tangents'.

CONTENTS.

Chapter VIII. Electrical Testing. 122

The Wheats tone Bridge.— Theory.— Post Office Pattern.— Siemens Pattern.— Measuring Resistances.— By Wheatstone Bridge Method— By Substitution Method. —Capacity Tes is.— Measurements Electromotive P'ORCE.— Internal Resistance of Batteries. — Locating Faults o\ Telegraph Wires. — Locating Crosses. — A Wheatstone Bridge Method. — 'Locating Faults by Varley Loop Test. — By Capacity Test, — Measuring Insulation Resistance of Wires and Cables.— Direct Deflection Method. — Measuring Partial Insulation Resistance of Telegraph Wires. —Testing Insulators, Etc.

Chapter X. Automatic Telegraph Repeaters. 153

Button Repeaters.— Woods. — Aittomatic Repeaters.— The Maver-Gardanier.— The Neilson. — Multiple. — The Milliken.— The Horton.— The Weiny.— The Atkinson..— The Ghegan.— Open Circuit.— Double Current.

Chapter XI. Duplex Telegraphy. 169

Differential Method. — Bridge Method. — The Stearns Duplex. — Continuity Preserving Transmitter, — Spark Coil. — Static Compensating Condensers. — Balancing Stearns Duplex. — The Polar Duplex. — Operation of.— Pole-Changer. — Polarized Relay. — Theory of Polar Duplex. — Balancing the Polar Duplex. -Terminal Connections, Etc.

Chapter XII

Theory of.— Operation of.— Edison Quadruplex. —Moment of No-Magnetism in Neutral Relay.— Smith Condenser Arrangement. — Ratio of Current Strength, Transmitter Closed and Open. — Action of Condenser as. Static Compensator,— Terminal Connections VV. U. Quadruplex. — W. U. Neutral Relay, Winding of.— Combination Rheostat —Repeating Sounder, Etc. — Dynamo Quadruplex Key Systems. — W. U. or Field Dynamo Key System, Theory of. — Terminal Connections W. U. Quadruplex.— Postal Telegraph Company Quadruplex. — Quotation Company^ Quadruplex. — General Remarks.— Nomenclature. — Balancing The Quadruplex. — Causes and Symptoms of Faults on Duplex and Quadruplex Circuits and Methods of Detecting Them.— The Roberson.— The British P. O. Quadruplex.

Chapter XIII. Duplex And Quadruplex Repeaters. 241

Extended Locals. — Quadruplex-Shcrt Wire Automatic Repeaters.— The Downer. — Gardanier— Emergency Repeaters. — Multiple Quad-Short Wire Repeaters. — Quad-Single Wire Automatic Repeaters, — The Edward's. — Waterbury. —Arrangement for Converting Short \Vire into Main Line Wire. — Hints ON THE Management of Quadruplex-Single Wire Repeaters, Etc. Etc.

Chapter XIV. Branch Office Signaling Devices. 256

Tne Buzzer or Interrupter. — New York Branch Office Call Wire. — Chicago Branch Office Signal. Arrangement. — The Hurd Branch Office Call.

Chapter XV. Loop Switches. 261

Loop Switch Connections. — Postal Loop Switch.— Davis Loop Switch.

CHAPTER XV].

COMBINATION DUPLEX SYSTEMS, ETC. s6a

The Edison-Smith Duplex. — The Sieurs Duplex.

CONTENTS. ' ^^

Chapter XVII. Submarine Telegraphy. 267

Mirror Receiver.— The Thomson Siphon Recorder.— Tlie Cuttriss Magnetic Siphon Recorder.— Earth Currents. —Use of Condenser in Connection Therewith.— Simplex Working.— Duplex Working.— Stearns Artificial Cable.— Muirhead i^rtificial Cable.— Steakns Cable Duplex.— Muirhead Cable Duplex.— Balancing Cable Duplex.— Rate of Signaling.— Brown and Allen Relay.— The Jacobs Duplex.— Under Water TELECRArHY.— Brown Cable Relay Repeater.

Chapter XVIII

Rapid Automatic Telegraphy.— Single Current.— Double Current Methods.— Chemical Automatic Telegraph Systems.— Theory.— Chemical Solutions Employed.— Effects, Etc.— Anderson Chemical Automatic System.— Page and Line Chemical Recorder.— The WnEATsroNE Automatic System.— Perforator. — Transmitter, — Theory of, Etc. — Wheatstone Receiver. — Wheatstone Duplex. — Terminal Connections, Etc. — Wheatstone Automatic Repeaters. — Condenser. — Repeater Relay. — Winding of. — Dial Rheostat. — *'Extra Current" Neutralizer.— Balancing and Adjusting Wheatstone Apparatus, Etc. — Automatic Fac-Simile Telegraphy.— Methods.— Electro-magnetic— Chemical. — Thb Denison Fac-Simile System.— Stevens Perforator.— Delany Rapid Automatic— Electrograph.-Pollak-Virag Automatic.

Chapter XXII

THE TELEPHONE.— SIMULTANEOUS TELEGRAPHY AND TELEPHONY.— VARLEY-ATH- EARN DIPLEX-DUPLEX.— THE EDISON PHONOPLEX.

The Telephone.— Theory of.— Simultaneous Telegraphy and Telephony.— Van Rysselberghe System, — Varley-Athearn Duplex- Diplex.— Superposed Currents.— The Edison Phonoplex. — The Phone,— Magnetic Coil, Etc.— Gray's Harmonic Telegraph.

Chapter XXIII. Time Telegraph Service. 356

Time Telegraph Signals. — Electrically Synchronized Clocks. — Barkaud and Lund Regulator. — Hamblet Synchronizing Apparatus. f >

Chapter XXIV. Heliography.— Military Telegraph Signaling. 361

Heliography. — MacGregor's Heliograph.— Operation of, Etc. — Military Telegraph Signaling. — Field Equipment. -Flag and Flash Signaling. — United States Station and Field Kits, Code, Et,-.

Chapter XXV. The American District Telegraph Messenger Service. 367

Call Boxes.— Central Office, Box Circuits.— Return Signal Call Boxes.— The Van Size.— District Service Magnet Bell.— Double-Pen Register. — Self-Starting Register. — Multiple Call Boxes. — Field and Firman. — District Service Switches. — The Lockwood Battery, — District Service Time Slips. — Faults on District Circuits.

Chapter XXVI. Automatic Burglar Alarm Telegraphy. 3s1

The Holmes Burglar Alarm System.— Operation of, Etc.- The Wilder Duplex Aupomatic Burglar Alarm. — Operation of, Etc.— Combination Call and Burglar Alarm Box. — The Double Balanced Relay.

X CONTENTS.

Chapter XXVII. Printing Telegraphy. 390

Theorv " Step by Step " Svstems.— News Tickers. -" Gold and Stock " Ticker System. —Theory and Operation ©f. Transmitter Key Boar..— Shifting Ue\nce.— Scott Two Wire Tickek.— Phelps Stock Prin'ier. — Operation of.— Pap r Fee-'.— Shifting Device —Key Board.— Type-Wheel.— Unison.— The " Umyersal " OR Edisox Tickek System.— Operation of.— •' Universal " Transmitter.— New York Quotation Company Ticker System — Operation. — •' Locker" Circuit — Healy Clutch Device. — Shifting Apparatus.— Ticker.— Paper Feed.— The Phelps "Motor" Priniing Telegraph System.— Printer — Motor Governor. — Transm'tting Apparatus. — Receiving Apparatus,— Synchronizing Device.— L'nison Device-Adjustment, Etc.— The Es.ick Page and Line Printek.— Theory.— Paper Carriage.— Printing Apparatus.— The Buckingham, Barclay, Murray, Hughes. Rowland. Baudot Systems.

CFIAPTER XXVIII.

FIRE ALARM TELEGRAPHY. 437

.Hwple Fire Alarm Telegraph Circuit.— The Gamewell Fire Alarm Telegraph System.— Automatic Non- Interfering Repeater. — Theory of, Etc. — Gardiner Non-Interfering Street Box, with Auxiliary Fire Alarm Attachments. — Indicator. — Operation of. — The Gaynor Fire Alarm Telegraph System. — Of)eration of. — Manual Repeater, Etc.- -Jersey City or Spkicher Fire Alarm Telegraph System.— Operation of. — Tower Bell Circuit Connections. — Tower Bell Electro-Mechanical Striking Apparatus. — Thk Gamewell Auxiliary Fire Alarm Telegraph System. — Operation of. — "Cross" Relav. — "Disturbance" Relay. Etc.— Automatic f lite Ai.akm TsuiGitAPiii.— The Bulen System.— Operation of —Thermo— stdts,Etc

CHAPTER XXIX. POLICE SIGNAL TELEGRAPH SYSTEMS. 47i

The Gamewell Police Signal Telegraph System.— Central Office, Street Box Electrical Connections.— Operation of, Etc.— Stable Electrical Connections.— Automatic Transmitter, or Multiple Break- Wheel.— Street Boxes. -The Chicago Police Patrol Telegraph System.— Operation — Patrol Box. — The Pearce and Jones Police Patrol Telegraph System. — Signal Box. — Stover Special Alarm Device. — The Municipal Police Signal Telegraph. — Street Boxes. — Time Stamp. — Answer Back Signal, Etc— Police Patrol Boxes.

Chapter XXX. Railway Electric Block Signaling Systems, Etc, 494

THE Union Switch and Signal Electro-Pneumatic Block System.— Operation of. Etc.— The Union Switch and Signal •' Clock'" System.— The Hall Railway Signal System. — Operation of, Etc.— Hall's Electric Signal for Crossings. — Overlapping Block Signal System.— The Sykes System OF Block Signaling.- The Stewart-Hall Train Order Signal.— Train Signals.— The Hart Train Signal.— ^Iolor Operated Semaphores— Miller Cab Signal.

Chapter XXXI. Overland Telegraph Wire. 509

The Manufacture of Iron and Copper Wire.— Wire Drawing.— Galvanizing Iron Wire.— Mechanical Tests of Telegraph W ire. — Wire Gauges. — American Standard Wire Gauge. — Micrometer, or Pocket Gauge — Tests for Breaking Strain. — For Ductihty.— Wire Testing for Resisiance and Conductivity. — Effects of Impurities On. — Corrections for Temperature. — Table of Co-Efficients for. — Weight Per Mile Ohm. — Iron and Steel Line Wire, Terms, Etc.

Chapter XXXII

UNDERGROUND CONDUITS.— UNDERGROUND. AND RIVER AND HARBOR TELEGRAPH

CABLES, ETC. 524

Underground Conduits. — ''Drawing In and Out." — •• Solid."— Rodding.— Underground Telegraph Carles. —Cable Jointing. — Measuring Insulation — Resistance of Joints. — River and Harbor Cables. — Cable Testing.— Remarks Concerning. — Elecrification. — Locating Faults in Cables Electro-me- CHANiCALLY. — Poiut to Point Method. — Locating Faults in Short Under-Water Cables. — L'nder-Runnine Method, Etc.

CONTENTS. yj

Chapter XXXIII. Construction And Maintenance Of Telegraph Lines. 524

Line Construction.— Erection of —Tools, Etc.— Guying.— Pole Lightning Arresters-— Brackets.— Cross- Arms.- Pins.— Fetter Drive Screw.— Insulators.— Wirk Stringing.— Wire Barrow.— Come Alongs.— Ty ing- Wire to Insulators.— Joints on Aerial Wires.—" Sleeve " Joints.— Pliers,— Anti-Hum Device.— Hou-e- ToP Fixtures. — After Construction. — Maintenance of Lines — TreeTrimming.— Etc. — Line Repair ing, Etc. — Trouble Hunting. — Af rial Cables. — Methods of Suspending. — Aerial Cable Hanger. — Chin- NOCK Cable Winder. — Operation of, Etc.

Chapter XXXIV. Specifications-estimates— Miscellaneous— Tables. 553

Sp2cifications for Apparatus. — Battery Material. — Hard Drawn Copper wire. — Iron Wire. — Aerial or Undt-r ground Cable. — Short, River or Harbor Cable. — Emergency Cable. — Form of Contract Specification (■ ' Manufacturing and Laying of Underground Cable —Miscellaneous. — Binding Screws.— Message ' ■ Prices of Telegraph Apparatus, Material, Etc- — Effects of High Temperatures on Vulcanized India Ruhi Insulation — Tables. — Difference Between Principal Wire Gauges in Decimal Parts of an Inch, — Numb<= Diameter, Weight, Length and Resistance of Commercial Copper Wire,— Wages of Operators.

I N T FiO 13 TLJ CTT O I^^i',

HE word " telegraph '■ strictly defined means " to write afar off." In the modern practice of telegraphy, however, the term has a wider meaning and it is now used to signify any means whereby intelligence is conveyed to a distance by signs or sounds.

From remotest times methods of communicating intelligence to a distance have been employed for purposes of war, defence and extraordinary intercourse.

A brief review of some of the earlier methods may be of interest at the openino- of a work of this nature, especially as such a review may be found to show that principles involved in the operation of very primitive methods of telegraphing have been applied in more or less modified forms in some of the modern electrical telegraph systems.

The ancient Greeks employed among other methods of telegraphing one which was, perhaps, the simplest of all the ancient methods. This method required the erection of tow«'S on hill-tops and other elevations, suitable distances apart. In each tower a vessel capable of holding a given quantity of water was placed. Down the side of the vessels the letters of the alphabet were arranged. Each vessel was supplied with means for permitting the water to flow out of the vessel at a given rate. When ready for signaling the vessels were filled with water. The station desiring to signal the other, raised a torch, at night. This was responded to by a similar signal from a distant tower. At another signal the attendants in each tower withdrew the stops and permitted the water to flow out of the vessels, and when the Avater had fallen to a point opposite a desired letter the torch was again raised; the attendant in the receiving tower noted the letter; each attendant refilled the vessel and the operation was repeated until the message was completed.

Towards the latter part of the eighteenth century the semaphore system of telegraphy was introduced; the term semaphore signifying " A Sign I bear.''

In semaphore systems of telegraphy one or more movable arms or levers supported on suitable posts are employed. By the manipulation of these levers messages may be transmitted with moderate rapidity. This method of telegraphing was very widely adopted, and, for many years, utilized, throughout Europe, especially in France and Russia, and is, in a modified form, in use to day on every i-ailroad in the world.

Xiv AMERICAN TELEGRAPHY.

In this country a semaphore system was for many years in successful operation "between Sandy Hook and New York, before, and for a short time after, the introduction of the electric telegraph, or, as it was termed, the magneto telegraph.

The semaphore company had stations on this line at Sandy Hook; the Highlands, N. J.; at Staten Island and in the cupola of the Custom House, New York City. This line was intended chiefly for reporting the arrivals of vessels at Sandy Hook.

For some time after the establishment of the magneto telegraph between New York and Sandy Hook the S"emaphore system held its own, for, while in foggy and hazy weather both systems were useless, since passing ships could not be discerned, in wet weather, without fog, the semaphore system was often the first to convey marine intelligence to the city, owing to the poor insulation of the electric telegraph wires. The semaphore company, however, ultimately found it to its interest to unite with the electric telegraph company.

Another system of telegraphy, somewhat akin to the semaphore, and known as Washington's telegraph, was at one time employed in this country. It was presumably so called because of the fact that it was one among many similar telegraph systems used during the war of Independence in this country.

The apparatus used in the Washington telegraph system was easy of construction^ and, it must be admitted, somewhat crude. It consisted of a portable mast, on the top of which was placed a tub, or barrel; also, on one side of the post, a movable flag was placed, and on the other side, near the top, a basket, which was suspended from a bracket or nail. By interchanging the position of the flag the barrel and the basket, and by moving the flag up and down, various signals could be sent, — about 60 different signals in all.

Although up to 1852 certain visual systems of telegraphy such as the semaphore, were in extensive use, electricity had been utilized, experimentally, long prior to that date, as a means of communicating intelligence to a distance.

For example, Lesage, of Geneva, had constructed a telegraph system consisting of 24 line wires, one for each letter of the alaphabet. At each terminal of each wire pith balls were suitably suspended, and, taking advantage of the well-known repellant effect that follows the electrification of such light substances, Lesage had succeeded, by the use of frictional electricity applied to the wires, in transmitting intelligible signals over them.

In 181 5 an "alphabetical " telegraph was invented by Francis Ronalds. In this arrangement, clockwork, operating a revolving dial, was used at each end of a wire. The dials rotated in unison. A notch was cut in each dial. Behind each dial the letters of the alphabet were placed in a circle, so that as the dial revolved one letter at a time was seen through the notch. Pith balls were electrically connected with the wire at each end. At a certain signal the clockwork was started, and as the

INTRODUCTORY. XV

notch came opposite a desired letter the circuit was so operated that the pith balls were actuated. The letter at that time seen through the opening in the dial was noted aud in that way messages were transmitted.

In 1839 a telegraph system was devised by de Heer in which a physiological effect of the electric current was employed. In this system ten wires were utilized between the sending and receiving stations. At the receiving station the operator placed his fingers and thumbs on the ten terminals of the line wires. Thus the passage of a current through one or more of the wires was felt in the fingers touching those wires, and signals were indicated by a pre-arranged manner of transmitting currents through the wires. For example, a simultaneous " shock " in the thumb of the right hand and forefinger of the left hand might signify the letter A, etc.

In 1774 Yolta discovered that electricity could be generated by chemical means, and, availing of the "voltaic" current from a battery, efforts were made, more or less successfully, between 1806 and 1830, to utilize, in the transmission of telegraphic signals, its property for decomposing metallic salts, by causing electric currents originated at one terminal of a wire to decompose a chemical solution at the other terminal; these efforts were the pioneers of others more successful in later years.

In 1820 the discovery was made by Oersted that a magnetic needle would be deflected from its normal position when held parallel to a wire conveying an electric current, and, further, that the deflection was to the right or left according to the direction of the current. Taking advantage of these discoveries various needle telegraph systems came into existence and were at one time extensively employed in Europe^ and are still in limited use there.

The needle systems were operated on the principle just referred to; namely: that a current flowing in a wire would deflect a magnetic needle. A magnetic needle was pivoted in the centre of a coil or coils of wire, and a pointer, attached to the needle, swung in front of a dial. Deflections to the right or left signified certain letters. These deflections were produced by sending over the wire pulsations of one polarity, or alternations of both, as required by the letter to be transmitted.

In 1824, Sturgeon, of England, discovered that when a current of electricity is caused to flow in an insulated wire surrounding a bar of well annealed iron, the latter becomes a magnet, and that when the current ceases to flow the iron at once loses its magnetism.

Availing of these electro-magnetic laws, Morse, in 1837, invented the telegraph system which bears his name, and which system, in one form or another, is, to-day, in almost general use.

The apparatus first used by Morse in his experiments bore but slight resemblance to the instruments now employed in Morse telegrapliy. For instaiu^e, the modern Morse relay weighs about 3 J pounds. The first telegraph relay or electro-magnet con-

XVI AMERICAN TELEGRAPHY.

etructed for Morse weighed over 300 lbs; and it was tliought that the height of improvement was reached when a relay was made that weighed only 70 lbs. By degrees, however, the laws of electro-magnetism became more clearly understood, and, finally, the instruments reached their present shape and size.

Much of the subsequent work of telegraph engineers up to the present time has related to the improvement of apparatus and the development of means for increasing the capacity of the existing wires either by the use of "automatic " telegraph systems or by the aid of " multiplex" systems of telegraphy.

It is not, however, only as an agent in the transmission of commercial or social telegrams that electricity is now employed in telegraphy. It also performs an indispensable part in the operation of Fire, Police, and other analogous telegraph systems, many of which will be found described iu the unabridged American Telegraphy.

Chapter I. Electricity

THEORIES ELECTRICAL TERMS ; ETC.

As with but few exceptions tlie systems of telegraphy rlescrlbecT in this book are electrical a reference to some of the theories of electricity may properly be made here. As, however, an extended review of the various theories of electricity (and magnetism) would be outside the scope of this work, such reference will be limited to what may be termed '* working theories," and to those throngli which several of the common terms at present in use have been introduced.

Reference will also be made here to some of the more important laws of electricity involved in the operation of the systems to be described ; reference to other electrical and also to certain magnetic laws and actions will be made elsewhere as may seem appropriate.

It may be ])remised that nothing is, at present, definitely known of electricity, except through its manifestations as a force, which manifestations are, it is assumed, the results of some mode of motion or disturbance of, or around the molecules of the substances in Avhich tlie manifestations are exhibited. The same may be said, generally, of magnetism, Avith this, additionally, that magnetism is always either an accompaniment of, or a result of, electrical action.

It is well known that electricity may be manifested in many ways; for example, by rubbing a glass rod with dry silk, or by rubbing a stick of wax with dry flannel, Avhen those substances become " electrifled ' ' and capable of attracting small, adjacent bodies. It is known, also, that when thus electrified, if the glass and the wax be lightly suspended they will attract each other, while, if two pieces of wax or two pieces of glass be thus electrified and similarly suspended it is found that they repel each other.

Since /^;r^ may be defined " as any cause whicli moves a body that is at rest or stops it when in motion," or which retards or increases the velocity of a body in motion, the foregoing may serve as simple instances of electricity as a force.

Franklin considered that electricity was an imponderable "fluid," pervading everything, and Avhich, in its normal condition, Avas uniformly distributed in all substances. He assumed that the electrical results obtained by rubbing glass were due to the production of an excess of the electric fluid in that substance, and that those obtained by rubbing the wax were due to a diminution of the fluid. The electricity manifested in the glass, when rubbed by silk, he called "positive; '' that in the* wax, when rubbed bv wool, he termed " negative."

The FrankUn theory was for many years entertauied, but the idea of electricity as a "fluid " is now o:enerallv abandoned.

For practical purposes it may be assumed, that all substances possess an electric state wliich is normally zero or neutral, and that, while in that condition, no electrical phenomena are ':ipparent; but if that normal electrical condition of ths substance be disturbed, electrical manifestations result.

This assumption may be iliustrated by analogy. For example, air, it is known, at any given portion of the earth's surface, is under a certain pressure, reckoned in somany pounds per square inch at sea level. Normally, so far as any given section of the earth's surface is concerned, if the air be left undisturbed, there is no visible evidence of its existence. If, however, by any means, as by the heating of the air particles at some one point of the earth's surface, the normal pressure is disturbed, a "'current" of air, that is, wind^ is the result, and the observed effects of wind are, obviously, manifestations of air in motion. Further, when, by suitable means, an excess of air is drivea into an air chamber, the compressed air within the chamber acquires a tendency to escape therefrom by any available outlet, and, if such an outlet be provided, a perceptible current of air will flow until equilibrium is established, that is, until the pressure within the chamber is equal to that without. If, on the contrary, a A'acuum be created in the chamber the reverse will be the case; the tendency will be for the air without to^ enter the chamber, until, as before, equilibrium, or zero pressure, is established. In either case, it will be observed, the direction of the current is from the point of higher to the point of lower pressure.

In the case of Rii " electrified '' body, that is, one in which the normal, electrical condition may be supposed to have been disturbed, it may be assumed that the molecules of the substance resist or oppose the changed electrical condition, and, furtheiv that, when thus displaced, the tendency of the molecules is to return to the normal condition of zero or neutrality; as, for example, an archer's bow resists bending. and> upon being bent, tends to restore itself to its normal condition.

If the electrified body be surrounded by an " insulating" medium, analogous, for instance, to the w^alls of an air chamber, a 23re!5c5ure is presumably exerted on that medium, which pressure will be relieved when the electrified body is, so to speak, given an opportunity to resume its normal condition of electrical equilibrium, as will be the case when a so called conductor of electricity is provided, for, example, an iron or copper wiie.