Farm implements and farm machinery

Front matter

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O w o '

°o y ^ *' O N o ^ O.V

Part I.— Mechanics

CHAPTER I.— Introduction. — Value of Farm Machinery— Importance of a Knowledge of Mechanical Principles 7-10

CHAPTER II.— General Principles of Mechanics.— Inertia, Experiments and Examples— Inertia of Moving Bodies, or Momentum— Fast Riding — The Tiger's Leap — Pile Engines —Fly-wheel — Estimating the Quantity of Momentum — Compound Motion — Various Examples — Centrifugal Force. 10-23

CHAPTER III.— Attraction.— Gravitation— Velocity of Falling Bodies — Resistance of the Air — Coin and Feather — Galileo's Famous Experiment — Cohesion— Soils — Strength of Materials — Capillary Attraction — The Earth a Desert without it— The Ascent of Sap — Centre of Gravity — Experiments — Upsetting Loads — Shouldering Bags — Rocking Bodies .... 23-^

CHAPTER IV.— Simple Machines, or Mechanical Powers.— Law of Virtual Velocities— The Lever— Many Examples of Levers — Estimating the Power of Levers — Three-horse WLiffle-tree — Compound Levers — Weighing Machines — Stump Pullers — A Wild Theory — Wheel and Axle — Examples— Band and Cog-work— The Pulley — Packer's Stone Lifter — The Inclined Plane— Crooked Roads — Power of Locomotives — Good and Bad Roads — The Wedge — The Screw — Knee-joint Power — Lever Washing Machines — Cheese Presses — Rolling Mills — Straw Cutters 43-74

CHAPTER V. — Application of Mechanical Principles in the Structure of Implements and Machines— Various Examples — Calculating the Strength of Parts 75-81

CHAPTER VI. — Friction.— How to ascertain its Amount- Friction on Roads — Resistance of Mud— The Results of the Dynamometer — Width of Wheels — Velocity — Size of Wheels on Roads — Friction Wheels — Lubricating Substances —Friction Necessary to Existence 81-93

CHAPTER VIl. — Principles of Draught. — Applied to Wagons —To Plows— Combined Draught of Animals— Whiffle-trees for Three Horses — Potter's do. — Wier's Single-tree — The Dynamometer — Self-registering do. — Waterman's do. — Dynamometer for Rotary Motion 93-108

CONTENTS, V

CHAPTER VIII —Application of Labor.— Power of Horses—

Of Men -Beet Way to Apply Strength 108-113

CHAPTER IX —Models of Machines.— Common Blunders- Works of Creation Free from Mistakes .113-115

CHAPTER X.— Construction and Use of Farm Implements AND Machines— Implements of Tillage. — Importance of Simplicity — Plows — Rude Specimens — Cast-iron and Steel do.— Character of a Good Plow — The Cutting Edge — Mould-board — Easy Running Plows — Crested Furrow Slices— Lapping and Flat Furrows — How to Plow Well- Fast and Slow Plowing — The Double Michigan — The Subsoil Plow— The Paring Plow— Gang Plow— Ditching Plow — Mole Plow — Coulters — Weed Hook and Chain — Pulverizers— Harrows— Geddes' Harrows— Scotch do.— Morgan Harrow— Norwegian do. — Shares' do. — Cultivators — Holbrook's—Alden's— Garrett's Horse-hoe — Two-horse Cultivators — Sulky do. — Comstock's Spader -Clod Crushers- Roller 115-153

CHAPTER XL— Sowing Machines.— Wlieat Drills— Bickford and Hoffman's do. — Seymour's Broadcast Sower- Com Planters— True's Potato Planter— Hand Drills 152-157

CHAPTER XIL— Machines for Haying and Harvesting.— Mowing and Reaping Machines — Cutter-bar — Combined Machines — Self Rakers — Johnson's do. — Marsh's and Kirby's do. — Dropper — Binders — Marsh's Harvester — Durability and Selection of Machines — flay Tedders— BuUard's do. — American do. — Horse Rakes— Revolving do. — Sulky Revolvers — Warner's do. — Spring Tooth Rakes — Hollingsworth's do. — Hay Sw^eep — Horse Forks — Cladding's do. — Palmer's, Myers', Beardsley's, Raymond's — Harpoon Forks — Hay Carriers — Hicks' do. — Building Stacks — Palmer's Hay Stacker— Raymond's Hay Stacker— Dederick's Hay Press— Beater do,— Hay Loaders 158-186

CHAPTER XIIL— Thrashing, Grinding, and Preparing Products. — Value of Thrashing Machines — Endless Chain Power— How to Measure Power of— Churning by Tread Power— Pitt's Elevator— Com Shellers— Burralls', Richards'— Root Washer — Root Slicers — Farm Mills, Allen's, Forsm an 's— Emery Cotton Gin 186 197

Part Ii.-machinery In Connection With Water

CHAPTER I.— Hydrostatics.— Upward Pressure— Measuring' Pressure— Calculating Strength of Tubes, etc.— Artesian Wells— Determining Pressure in Vessels— A Puzzle Explained—Hydrostatic Bellows— Press— Specific Gravities- Table of do.— Weight and Bulk of a Ton of Different Substances 198-210

YI CONTENTS.

CHAPTER II.— Hydraulics.— Velocity of Water— Discharge of Water through Pipes— Velocity in Ditches— Leveling Ditches— Archimedean Screw-pumps— For Cisterns-Non-freezing do.— For Deep Wells-Drive Pumps— Chain Pumps— Rotary do.— Suction and Forcing Pump— Turbine Water Wheels— The Water Ram— Water Engines for Gardens— Flash Wheel— Nature of Waves— Size of do.— Preventing Inroads by do.— Cisterns— To Determine Contents of 211-238

Part Iii.-machinery In Connection With Air

CHAPTER I.— Pressure of Air.— Weight of the Atmosphere- Hand Fastened by Air— Barometer— Measuring Heights- Syphon ^^245

CHAPTER II.— Motion of Air.— Winds — Wind-mills, how Used— Brown's do.— Causes of Wind— Chimney Currents- Construction of Chimneys— To Cure Smoky do.— Chimney Caps — Ventilation 245-259

Part IV. -heat

CHAPTER 1.— Conducting Power— Expansion, Great Force of— Experiments with— Steam Engine— do. for Farms— Steam Plows— Latent Heat— Green and Dry Wood 260-276

CHAPTER IV.— Radiation.— Several Examples in Domestic Economy— Dew and Frost— Frost in Valleys— Sites for Fruit Orchards » 276-280

PART v.— RECENT MACHINES

Improvement in Plows. — Hard or Chilled Iron Plows — Sulky Plows — Spring-tooth Harrow — Disc Harrow — Thomas Smoothing Harrow — Corn-Planters — Mowers and Reapers — Hay Loaders — Corn Huskers — Hay Presses — Wind-mills 281-289

Introduction

No farm can be well furnished without a large number of machines and implements. Scarcely any labor is performed without their assistance, from the simple operations of hoeing and spading, to the more complex work of turning the sod and driving the thrashing-machine. The more perfect this machinery, and the better fitted to its work, the greater Avill be the gain derived by the farmer from its use. It becomes, therefore, a matter of vital importance to be able to construct the best, or to select the best already constructed, and to apply the forces required for the use of such machines to the greatest possible advantage.

Nothinor shows the advancement of modern a<?riculture in a more striking light than the rapid improvement in farm implements. It has enabled the farmer within the last fifty years to effect several times the work with an equal force of horses and men. Plows turn up the soil deeper, more evenly and perfectly, and with greater ease of draught; hoes and spades have become lighter and more efficient ; grain, instead of being beaten out by the slow and laboiious work of the flail, is now showered in torrents from the thrashing-machine ; horse-rakes accomplish singly the work of many men using the old hand-rake ; horse-forks convey hay to the barn or stack with ease and rapidity ; twelve acres of ripe grain are neatly cut ill one day with a two-horse reaper; grain drills and planting machines, avoiding the tiresome drudgery of hand labor, distribute the seed for the future crop with evenness and precision.

The owner of a seventy-thousand-acre farm in Illinois carries on nearly all his work by labor-saving machinery. He drives posts by horse-power; breaks his ground with Comstock's rotary spader; mows, rakes, loads, unloads, and stacks his hay by horse-power ; cultivates his corn with two-horse, seated or sulky cultivators ; ditches low ground, sows and plants by machinery ; so that his laborers ride in the performance of their tasks without exhausting their strength with needless walking over extended fields.

The great value of improved farm machinery to the country at large has been lately proved by the introduction of the reaper. Careful estimate determined that the number of reaping machines introduced througliout the oountry up to the beginning of the great rebellion, performed an amount of labor while working in harvest nearly equal to a million of men wath hand implements. The reaper thus filled the void caused by the demand on workingmen for the army. An earlier occurrence of that

VALUE OF FARM MACHINEET. 9

war must therefore have resulted hi the sceneral ruin of the grain interest, and prevented the annual shipment of the millions during that gigantic contest, which so greatly surprised the commercial savans of Europe.

The implements and machines which every farmer must have who does his work well are numerous and often costly. A farm of one hundred acres requires the aid of nearly all the following; two or more good plows, a shovel-plow, a small plow, a subsoiler, a single and two-horse cultivator, a seed-planter, a grain-drill, a roller, a harrow, a fanning-mill, a straw-cutter, a root-slicor, a farm wngon with hay-rack, an ox-cart, a horse-cart, wheel-barrow, sled, shovels, spades, hoes, hay-forks and manureforks, hand-rakes and horse-rakes, scythes and graincradle, grain-shovel, maul and wedges, pick, axes, woodsaw, hay-knife, apple-ladders, and many other smaller conveniences. The capital for furnishing the farms in the Union has been computed to amount to more than five hun.dred millions of dollars, and as much more is estimated to be yearly paid for the labor of men and horses throughout the country at large. To increase the effective force of labor only one-fifth would, therefore, add annually one hundred millions in the aggregate to the profits of farming.

A knowledge of the science of mechanics is not so well understood among all classes of people as it should be. A loss often occurs from the want of a correct knowledge of mechanical principles. The strength of laborers is badly applied by the use of unsuitable tools, and that of teams is partly lost by being ill adjusted to the best line of draught. We may perhaps see but few instances of so great a blunder as the ignorant teamster committed who fastened his smaller horse to the shorter end of the whifile-tree, to balance the large horse at the longer end ; yet instances are not uncommon where operations are performed to almost as great a disadvantage, and which, to 1* a person well versed in the science of mechanics, would appear nearly as absurd.

It is well worth while to look at the achievements made through a knowledge of mecbaiiical principles. Compare the condition of barbarous and savage tribes with that of modern civilized nations. The former, scattered in comfortless hovels, subsist by precarious hunting, or on scanty crops raised on patches of ground by means of the rudest tools. The latter are blessed with smooth, cultivated fields, green meadows, and golden harvests. Commerce with its hum of business, extending through populous cities, and along a hundred far-stretching lines of rail-ways, scatters comforts and luxuries to millions of homes ; while ships for foreign commerce thread every channel and whiten every sea. The contrast exhibits the difference between ignorance on the one hand, and the successful application of scientific principles on the other. It is our present object to point out to the farmer the advantages which would result from a wide extension, through all classes, of this knowledge, that the opportunities may be continually increased for general improvement.

Chapter II. General Principles Of Mechanics

Having briefly pointed out some of the advantages to the farmer of understanding the principles of the machines he constantly uses, we now proceed to an examination of these principles. It will be most convenient to begin with the simpler truths of the science, proceeding, as we advance, to their application in the construction of machines.

INERTIA. — EXPERIMENTS AND EXAKPLES.

INERTIA.

An important quality of nil material bodies is inertia. This term expresses their passive state — that is, that no body (not having lite), when at rest, can move itself, nor, when in motion, can stop itself. A stone has not power to commence rolling of its own accord ; a carriage can not travel on tlie road without being drawn; a train of cars never commences gliding upon the rails without the power of the locomotive.

On the contrary, a body, when once set in motion, will continue in motion perpetually, unless stopped by something else. A cannon ball rolled ujDon the ground moves on until its force is gradually overcome by the resistance of the rough earth. If a polished metallic globe were driven swiftly on a level and polished metallic p^ane, it would Fig. 1. continue in motion a long time and

travel to a great distance ; but still the extremely minute roughness of the surfaces, with the resistance of the air, would continually diminish its speed until finally stopped. A wheel made to spin on its axis revolves until the fiiction at the axis and the impeding force of the air bring it to rest. But if the air is first removed, Fans revolving in a vacuum. \)j means of an air-pump, the motion will continue much longer. Under a glass receiver, thus exhausted, a tcp has been made to spin for hours, and a pendulum to vibrate for a day. The resistance of the air may be easily perceived by first striking the edge and then the broad side of a large piece of pasteboard against the air of a room. It is further shown by means of an interesting experiment with the air-pump. Two fan-wheels, made of sheet tin, one, «, striking the air with its edges, and the other, b, with its broad faces (fig.

1), are set in motion alike; h is soon brought to rest, while a continues revolving a long time. If now they are placed under the receiver of an air-pump, the nir exhausted, and motion given to them alike by the rack-work c?, they will both continue in motion during the same period.

There is no machinery made by man free from the checkins: influence of friction and the air: and for this reason, no artificial means have ever devised a perpetual motion by mechanical force. But we are not without a proof that motion will continue without ceasing when nothing operates against it. The revolutions of the planets in their orbits fiirnisli a sublime instance; where removed from all obstructions, these vast globes wheel nround in their immense orbits, through successive centuries, and with unerring regularity, preserving undiminished the mighty force given them when first launched into the regions of space.

To set any body in motion, a force is requisite, and the heavier the body, the gieater must be the force. A small stone is more easily thrown by the hand than a cannon ball ; speed is more readily given to a skiff than to a large

and heavy vessel ; but the same force which sets a body in motion is required to stop it. Thus a wheel or a grindstone, made to revolve rapidly, would need as great an effort of the arm to stop it suddenly as to give it -a - cr-' gu,]^]ei^ motion. An unusual exertion

Inertia Apparatus.

of the team is necessary in starting a loaded wagon; but when once on its way, it would require the same effort of the horses to stop it as to back it when at rest.

The force of inertia is finely exhibited by means of a little instrument called the inertia apparatus (fig. 2). A marble or small ball is placed on a card, c, resting on a concave stand. A spring snap is then made to stiike the

INERTIA. — EXPEEIMENTS AND E3 4MVI ER card, throwing it to a distance, but leaving the ball upon the hollow end of the stand. The same experiment may be easily performed by placing a very small apple or other solid on a card, the whole resting on a common sand-box, or even the hollow of the hand. A sudden snap with the finger will throw the card away, while the apple will drop into the cavity. The following experiment is still more striking : Procure a thread just strong enough to bear three pounds, and hang upon it a weight of two pounds and a half Another half pound Avould break it. Now tie another thread, strong enough to bear one pound, to the lower hook of the weight. If the lower thread be pulled gradually^ the upper thread will of course break ; but if it be pulled with a Je?'A*, the lower thread will break. If the jerk be very sudden, the lower string will break, even it be considerably stronger than the upper, the inertia of the weight requiring a great force to overcome it suddenly. The threads used in this experiment may be easily had of any desired strength by taking the finest sewing cotton, and doubling to any desired extent.

This experiment shows the reason why a horse, when he suddenly starts with a loaded wagon, is in danger of breaking the harness ; and why a heavier weight may be lifted with a windlass or pulley having a weak rope, if the strain is gradual and not sudden. For the same reason, glass vessels full of Avater are sometimes broken when hastily lifted by the handle. When a bullet is fired through a pane of glass, the inertia retains the surrounding glass in its place during the moment the ball is passing, and a round hole only is made; while a body moving more slowly, and pressing the glass for a longer space of time, fractures the whole pane.

INERTIA OF MOYING BODIES, OR MOMENTUM.

Momentum is the inertia of a moving body. When a force is applied to a heavy body, its motion is at first slow ; but the little momentum it thus acqtiires, added to the applied force, increases the velocity. This increase of velocity is of course attended with increased momentum, which again, added to the acting force, still further quickens the speed. For this reason, when a steam-boat leaves the pier, and its paddle-wheels commence tearing through the water, the motion, at first slow, is constantly accelerated until the increasing resistance of the water becomes equal to the strength of the engine and the momentum.* Were it not for the momentum of moving bodies (inertia existing), no speed ever could be given to any heavy body, as a carriage, boat, or train of cars.

The chief danger in fast riding, or fast traveling of any kind, is from the momentum given to the traveler. If a rail-way passenger should step from a car when in full motion, he would strike the earth with the same velocity as that of the train; or if the train at thirty miles an hour should be instantly stopped, the passengers would be pitched forward with a swiftness equal to thirty miies an hour. When a horse suddenly stops, the momentum of the rider tends to throw him over the horse's head. When a wagon strikes an obstruction, the driver falls forward. A case in court was once decided against the plaintiff", who claimed that the defendant had diiven ao-ainst his waofon with such force as to throw the plaintiff* to a great distance ; but the fact was shown that by such momentum he himself must have been driving furiously, and not the defendant, and he lost his suit.

* In ordinary practice, this is not strictly correct, 2iS friction v^xW make some difference. This influence will be more particularly considered on a subsequent page. Its omission here does not at all alter ihQ frincipU under consideration.

MOMENTUM. EXAMPLES.

Fig. 4.

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Sdl

W

An Eastern traveler once succeeded in saving his life by a ready knowledge of this principle. He was closely pursued by a tiger, and when near a precipice, watching his

opportunity, he threw his coat and hat on a bush, and jumped one side, when the animal, leaping swiftly on the concealed bush, was carried by momentum over the precipice.

As a large or heavy body possesses greater momentum than a small or light one, so any body moving with great speed possesses more than one moving slowly ; for instance, the momentum of a rifle ball is so great as to carry it through a thick plank, while, if thrown slowly, it would scarcely indent it.

This property of bodies is applied with great advantage to many practical purposes. The momentum of the hammer drives the nail into the w^ood ; for the mere pressure of its weight w^ould not do it, if it were a hundred times as heavy.

Wedges are driven by employing the same kind of power.

On a larger scale, the pile-engine operates in a similar manner. The ram or weight, h (fig. 4), is slowly lifted by means of a pulley and wheel-work, worked by the handles or cranks, b b, until the arms of the tongs which hold the ram are compressed in the cheeks, i i, when it suddenly falls with prodigious force on the pile or post to be driven. In this way long posts of great size are forced into the mud of swamps and

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Pile Engine.

IG

MECHANICS.

river bottoms, where other means would fail. When a steam-engine is used for lifting the ram, the work is more raj)idly performed.

An interesting example of the use and efiiciency of momentum is furnished by the water-ram^ a machine for raising water, described on a subsequent page.

The fcy-wheel^ a large and heavy wheel used to regulate the motion of machinery, derives its value from the j^ower of inertia, or momentum, which prevents the machine from stopping suddenly when it meets with any unusual obstruction. In the common thrashing-machine, it has been found that a heavy cylinder, by acting as a fly-wheel, rendeis the motion steadier, and less liable to become impeded by large sheaves of grain. An ignorance of this principle has sometimes proved a serious inconvenience. A farmer, having occasion to raise a large quantity of water, erected a horse-pump ; but at every stroke of the

pump the animal was suddenly thrown loosely forward, and again jerked backward, as the piston fell lightly and rose heavily. A fly- Avheel attached to the machinery would have prevented this unpleasant jerking, and have enabled the horse, in consequence, to accomplish more work. In the pile-driving engine, where a great weight is suddenly thrown loose from a height, the horses would be pitched forM'ard when sudderdy relieved of this load but for the regulation of a fly-wheel, the motion of which is not quickly changed, neither from fast to slow nor from slow to fast.

Where there is a rapid succession of forces required in practice, the fly-wheel is usually of gieat advantage. Hence its use in all revolving straw-cutters, whei-e the

Fig. 5.

Straw-cutter luithJly-ivhecL

IXERTIA. THE FLY-WHEEL.

knives make quickly-repeated strokes (fig. 5). More recently it has been a])plied to the dasher-clmrn (fig. 6), where the rapid upright strokes are so well known to be very fatiguing for the amount of force applied.

By thus regulating motion, the fly-wheel frequently enables an irregular force to accomplish work which otherwise it could not perform. Thus a man may exert a force equal to raising a hundred pounds, Fig. 6.

yet, when he turns a crank, there is one part of the revolution where he works to great disadvantage, and where his utmost force will not balance forty pounds. Hence, if the work is hea^ y, he may not be able to turn the crank, nor to do any work at all. If, however, a fly-wheel be applied, by gathering force at the most favorable part of the turning, it carries the crank through the other part.

An error is sometimes committed by sujiposing the fly-wheel actually creates power, for as much force is requiied to give it momentum as it afterward imparts to the machine ; it consequently only accumulates and regulates power.

On rough roads, the force of inertia causes a severe strain to a loaded wagon when it strikes a stone. The horses are chafed, the wagon and harness endangered, and the load jarred from its place. This inconvenience is avoided in part by placing the box upon springs, which, by yielding to the blow, gradually lessen the effects of the shock. For carts and slowly moving lumber-wagons springs are useful, but more so as the velocity and momentum increase. Even on so smooth a surface as a rail-road, it was found by experunents made some years ago, that when the machinery of a locomotive was placed

Chum with a fly-wheel, for equalizing the motion.

upon springs, it would endure the wear and tear of use four times as long as without them.

For this reason, a ton of stone, brick, or of sand, is harder for a team tlian a ton of wool or hay, which possesses considerable elasticity.

ESTIMATING THE QUANTITY OF MOMENTUM.

The quantity of momentum is estimated by the velocity and weight of the body taken together. Thus a ball of two pounds weight moves with twice the force of a onepound ball, the speed being equal ; a ten-pound ball with ten times the force, and so on. A body moving at the rate of two feet per second possesses twice the momentum of another of equal size with a velocity of only one foot per second. A musket ball, weighing one ounce, flying with fifty times the speed of a cannon ball, weighing fifty ounces, would strike any object with equal force ; or, if they should meet each other from opposite directions, the momentum of both w^ould be mutually destroyed, and they would drop to the earth.

Where the mass is very great, even if the motion is slow, the momentum is enormous. A large ship floating near a pier wall may approach it with so small a velocity as to be scarcely perceptible, and yet the force would be enough to crush a small boat. When great weight and speed are combined, as in a rail-way locomotive, the force is almost irresistible. This circumstance often insures the safety of the passengers ; for as nothing is capable of instantly overcoming so powerful a momentum, when accidents occur the speed is more gradually slackened, and the passengers are not pitched suddenly forward. A light wagon, rapidly driven, possessing but little comparative force, is more suddenly arrested, and the danger is greater.

When two bodies meet from opposite directions, each

COMPOUND MOTIOX. 19

sustains a shock equal to the united forces of both. Two men accidentally coming in contact, even if walking moderately, receive each a severe blow ; that is, if each were walking three miles an hour, the shock would be the ^same as if one at rest were struck by the other with a velocity of six miles an hour. This principle accounts for the destructive effects of two ships running foul of each other at sea, or of the collision of two opposite trains on a rail-road.

The preceding principles show that a sledge, maul, or axe will always strike more effective blows when made heavier, if not rendered unwieldy.

COMPOUND MOTION.

It often happens that two or more forces act on the same body at the same time. If they all act in the same direction, the effect will be equal to the sum of the forces talien together ; but if they act in opposite directions, the forces will tend to destroy each other. If two equal forces act in contrary dii^ections, they will be completely neutralized, and no motion will be ])roduced. Thus, as an example of these forces — a bird flying at the rate of forty miles an hour, loith a wind blowing forty miles an hour, will be driven onward by these two combined forces eighty miles an hour; but if it undertake to fly against such a wind, it will not advance at all, but remain stationary. A similar result will take place if a steam-boat, liaving a speed of ten miles an hour, should first run down a river Avith a current of equal volocity, and then upward against the current ; in the first case it would move twenty miles an hour, and in the latter it would not move at all.

Where forces act neither in the same nor in opposite directions, but obliquely, the result is found in the follow-

MECITAXICS.

If a ball, placed at the point a (fig. 7), be struck by two different forces at the same moment, in the

direction shown by the two arrows, and if one force be just sufficient to carry it from a to c, and the other to carry it from a to 5, then it will move intermediate between the two, in the direction of the diasfonal of the parallelogram a €?, and to a distance just equal to the length of this diagonal or crossdiameter.

When the forces act very nearly togetlier, the parallelogram of the forces will be very narrow aud quite long, with a long diagonal Fig. 8.

(fig. 8) ; but if they act on nearly opposite sides ^^' of the ball, they Avill

very nearly neutralize each other, and the diagonal or result will be very short, showing that the motion given to the ball will be very small (fig. 9).

These examples show the importance of having teams attached to a plow or to a wagon very nearly in a straight line with the draught, or else a part of the force will be Fig. 9. lost ; and also the impor-

tance, when several animals arc drawing together, of their working as nearly as possible in the same straight line. For, the more such forces deviate from a right line, the more they wdll tend to destroy or neutralize each other.

A familiar example of the result of two oblique forces is furnished when a boat is rowed across a river. If the river has no current, the boat will pass directly from bank to bank perpendicularly ; but if there is a current, its track will form a diagonal, and it will strike the opposite bank

CENTRIFUGAL FORCE.

lower down, according to the rapidity of the stream and the slowness of the boat.