ALBERT R. MANN LIBRARY New York State Colleges OF Agriculture and Home Economics Cornell University 3^- £ DATE DUE _:ip«« *T97fl *\ ZlSmm yf 9 .^^ff^^x -ifltlm '4Ml mLy ^S fSLUiSL ' * [^fl^BlW*^ AP R 28 1995 GAYLORD PRINTED IN U.5.A. ' Cornell University Library S 675.T45 1859 Farm implements, and the princi pies of t 3 1924 000 328 132 Cornell University Library The original of tliis bool< is in tine Cornell University Library. There are no known copyright restrictions in the United States on the use of the text. http://www.archive.org/details/cu31924000328132 FARM IMPLEMENTS, PRIJfCIPlBS OF THEIR CONSTRUCTION AND USE; ELEMENTARY AST) FAMILIAE, TREATISE ON MECHANICS, AND ON NATURAL PHILOSOPHY GENERALLY, AS APPLIED TO THE ORDINARY PRACTICES OF AGRICULTURE. WITH 200 ENGRAVED ILLUSTRATIONS. BY JOHN i. THOMAS. •* We should like to see this work printed, bound, and hung up in every work- shop, tool-room, and fanner's book-shelf in the country. It gives the reason and explains the action of mechanical powers, and the forces of nature generally, with illustrations so directly drawn from the farmer's daily routine, that it gives a direct meaning and value to every point, rarely found in text-books." — Dovming's Review qftke First Edition. A. 0. MOOEE & CO., AGEICULTHRAL BOOK PUBLISHERS, 140 FULTON STREET. 1859. s 676' 7 V 6 8 ^ u CORNEL UNiVERSfTY S^ LIBRARY -^ Entered, according to Act of Congress, in the year 1859, By a. 0. MOOEE & CO., In tbe Clerk's Office of the Southern District of New York, WyNKOOP,HAl.LENTJfi:CK A THOMAS, Printers^ 113 FAV-n Sircel, N. Y. PREFACE. Tms work, in its original form, was published in the Transactions of the New York State Agricultural So- ciety for 1850, under the title of " Agricultural Dy- namics," or the Science of Farm Forces. The present edition is prepared on the basis of the original essay, and is thoroughly revised and greatly enlarged, with the addition of more than double the former number of illustrations. It comprehends those branches of Natural Philoso- phy known as Mechanics, Hydrodynamics, Pneumat- ics, and Heat, in their more common application to the practices of modem improved farming ; and, so far as practicable, technical words and phrases have been avoided, and the whole rendered simple and intelUgi- ble to ordinary readers. The leading principles have been derived from the existing stock of knowledge ; but no treatise on these subjects, as specially applied to agriculture, having be- fore appeared, the various examples of the application of those principles to the structure and use of farm im- plements, and to the farmer's daily routine, are mostly original. For the purpose of adapting the work to schools, wherever it may be desirable, it is divided into sec- tions, each of sufRcient length for a single recitation. CONTENTS. PART I. MECHANICS. CHAPTER I. INTRODUCTION. Page Benefits of Mechanical Knowledge 13 CHAPTER II. GENERAL PRINCIPLES OF MECHANICS. SECTION I. General Properties of Matter 18 Divisibility ■ . . . 18 Impenetrability 20 Indestructibility , 20 Inertia 21 SECTION 11. Momentum, or Inertia of moving Bodies 24 The Fly-vfheel 27 Application of Fly-wheel in churning and cutting Straw 28 Estimating the Quantity of Momentum , 30 SECTION III. Compound Motion 31 Centrifugal Force 34 CHAPTER HI. ATTRACTION. SECTION I. Gravitation 35 Measuring Velocity of falling Bodies — Atwood's Machine 38 Vm CONTENTS. SECTION II. Page Cohesion 42 Strength of Materials 43 Capillary Attraction 47 Ascent of Sap 49 SECTION III. Centre of Gravity 50 Line of Direction ^2 CHAPTER IV. SIMPLE MACHINES, OE MECHANICAL POWF' SECTION I. Advantages of Machines 60 Law of Virtual Velocities 61 SECTION II. The Lever 63 SECTION III. Estimating the Power of Levers 67 Combination of Levers 70 Weighing Machine 71 Machines for extracting Stumps 72 SECTION IV. Wheel and Axle 75 Mole-plow 78 Band and Cog Wheels 79 Form of Teeth or Cogs SO SECTION V. The Pulley 83 SECTION VI. The Inclined Plane 86 Ascent in Roads 87 Form and Materials for Roads 90 Importance of good Roads 92 SECTION VII. The Wedge 93 The Screw 94 CONTENTS. IX CHAPTER V. APPLICATION OP MECHANICAU PRINCIPLES IN THE STEUCTHEE OF THE PARTS OF IMPLEMENTS AND MACHINES Page 96 CHAPTER VI. FRICTION. SECTION L Rolling Friction 103 Nature of Friction 104 Estimating the Amount of Friction 104 SECTION II. Results with the Dynamometer 107 Width of Wheels 109 Velocity as affecting Friction 110 Friction at the Axle Ill Friction Wheels 112 SECTION III. Lubricating Substances 113 Advantages of Friction 115 SECTION IV. Principles of Draught 117 Combined Draught of Animals 120 SECTION V. Construction and use of the Dynamometer 122 Self-recording Dynamometer 125 Dynamometer for Rotary Motion 126 CHAPTER VII. CONSTRUCTION AND USE OF FARM IMPLEMENTS AND MACHINES. SECTION I. Plows and Plowing 130 Trench and Subsoil Plowing 134 The double Mould-board Trench Plow 135 The Subsoil Plow 136 Fowler's Draining Plow 136 The Paring Plow— The Gang Plow 140 A2 X CONTENTS. SECTION U. F»ge Pulverizers 141 The Harrow 141 Cultivators 143 Clod-crushers 146 SECTION III. Sowing-machines 148 Horse Rakes 152 Mowing and Reaping Machines 156 SECTION IV. Knee-joint Power 159 Endless-chain Powers 164 SECTION V. Application of Labor 167 SECTION VI. Models of Machines 173 PART II. HYDRODYNAMICS. CHAPTER I. HYDROSTATICS. SECTION I. Upward Pressure 176 Measurement of Pressure at different Heights 178 Determining the Strength of Pipes 179 Springs and Artesian Wells 179 SECTION II. Detennining Pressure on Surfaces 180 Hydrostatic Bellows 183 Hydrostatic Press 184 SECTION III. Specific Gravities 187 CHAPTER n. HYDRAULICS. SECTION I. Velocity of falling Water 189 Discharge of Water through Orifices and Pipes . . 190 CONTENTS. Xi SECTION II. IS Leveling Instruments 194 Velocity of Water in Ditches 193 SECTION III. HYDKAULIC MACHINES. Archimedean Screw 196 Archimedean Root-washer 197 Pumps 198 Water-ram , 200 Water-engines 202 Flash-wheel 203 SECTION IV. WAVES. Nature of Waves 204 The Water not progressive 205 Breadth and Velocity of Waves 206 Preventing the Inroads of Waves 208 SECTION V. Contents of Cisterns 210 Rule for determining the Contents 211 Determining their Size 212 PAET III. PNEUMATICS. CHAPTER I. PHESSHBE OF AIR. Height and Weight of the Atmosphere 213 The Barometer 216 The Syphon 218 CHAPTER n. MOTION OP. AIK. SECTION I. Winds— Force of Wind 221 Wind-mills for Farms 223 Causes of Wind ■ ^'^'' Xll CONTENTS. SECTION II. Chimney Currents 227 Construction of Chimneys 228 Chimney-caps 229 VentUation 233 PART IV. HEAT. CHAPTER I. CONDUCTION OF HEAT. SECTION 1. Conducting Power of Bodies 235 Utility of this Principle 236 Conducting Power of Liquids 237 SECTION II. Expansion by Heat 238 The Steam-engine 241 Exception to Expansion by Heat 246 SECTION III. Latent Heat 248 Advantages of Latent Heat — Latent Heat of Steam 249 Green and dry Wood for Fuel 250 CHAPTER H. Radiation of Heat 253 Dew and Frost 255 Frost in Valleys — Remarkable Effects of Heat on Water 256 APPENDIX. Apparatus for Experiments 259 Tables of Specific Gravities 263 Weight of a cubic Foot of various Substances 264 Discharge of Water through Pipes 264 Velocity of Water in Pipes 265 Rule for the Discharge of Water 266 FARM IMPLEMENTS, PRINCIPLES OF THEIR CONSTRUCTION AND USE. PART I. MECHANICS. CHAPTER I. INTRODUCTION. No farm, even of moderate size, can be well fur- nished without a large number of machines and im- plements. 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. It becomes, therefore, a matter of vital importance to the farmer 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 best possible ad- vantage. A great loss occurs frequently from the want of a correct knowledge of mechanical principles. The strength of laborers is often badly applied by the use of unsuitable tools, and that of teams is partly lost by being ill adjusted for the best line of draught ; az, for 14 MECHANICS. example, by a bad attachment to the plow for foromg its wedge-Uke form most effectively through the sod. We may perhaps see but few instances of so great a blunder as the man committed who fastened his smaller horse to the shorter end of the whipple-tree, to balance the large horse at the longer end ; or of the other man, who, when riding on horseback to mDl, atop of his bag of grain, concluded to reheve the ani- mal by dismounting, shouldering the bag himself, and then remounting ; yet cases are not uncommon where other operations are performed to almost as great a disadvantage, and which, to a person well versed in the science of mechanics, would appear nearly as strange and absurd. The improvement of farm machines and tools with- in the last fifty yearS has probably enabled the farmer to effect twice as much work with the same 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 Ughter and more ejfficient ; grain, instead of being beaten out by the slow and la- borious work of the flail, is now showered in torrents from the thrashing-machine ; horse-rakes accomphsh singly the work of many men using the old hand-rake ; twelve to twenty acres of ripe grain are neatly cut in one day with a two-horse reaper ; wheat drills, avoid- ing the tiresome drudgery of sowing by hand, are ma- terially increasing the amount of the wheat crop ; while a few farmers are making a large yearly saving by the appUcation of horse-power to sawing wood, churning, driving washing-machines, and even to ditch- ing. A celebrated English farmer has lately accom- INTRODUCTION. 15 plished even more ; for, by means of a steam-engine of six-horse power, he drives a pair of mill-stones for grinding feed, thrashes and cleans grain, elevates and bags it, pumps water for cattle, cuts straw, turns the grindstone, and drives liquid manure through pipes for irrigating his fields ; and the waste steam cooks the food for his cattle and swine— all this work being performed in a first-rate manner. Now these improvements were mainly effected through the knowledge of mechanical principles, and many of them would doubtless have been sooner achieved and better perfected if these principles had been well understood by farmers ; for, constantly using the machines themselves, they could have perceived just what defects existed, and, by understanding the reasons of those defects, have bee» able to suggest the remedies in a better manner than the mere manufac- turer. Moreover, as the introduction of what is new and valuable depends greatly upon the call for them, farmers would have been prepared to decide with more confidence and certainty upon their real merits, and thus to increase and cheapen the supply of the best, and to reject the worthless. One great reason that farm implements are stiU so imperfect, is, that the farmers themselves do not fully understand what is needed, and how much may be yet accompUshed. They have not enough knowledge of the principles of mechanics to quaUfy them for judging of the merits of new machines ; and, being afraid of imposition, often reject what is really valuable, or else, being 'pleased with a fine appearance, are easily de- ceived with empty pretensions. 16 MECHANICS. 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 aU the following : two good plows, a small plow, a subsoUer, a single and two-horse culti- vator, a drill-barrow, a roller, a harrow, a fanning-mUl, a straw-cutter, a root-slicer, a farm wagon with hay- rack, an ox-cart, a horse-cart, wheel-barrow, sled, shov- els, spades, hoes, hay-forks and manure-forks, hand- rakes and revolving rakes, scythes and grain-cradles, grain-shovel, maul and wedges, pick, axes, wood-saw, turnip-hook, hay-knife, apple-ladders, and many other smaller conveniences. The capital for thus furnishing in the best manner all the farms in the Union has been computed to amount to five hundred 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 ; while on the other hand, if we look back fifty years to the imperfect implements then in use, we may at once perceive the vast amount saved by the improvements since made ; and when, especially, we notice the condition of bar- barous nations, and contrast that condition with our own — ^the former thinly scattered in comfortless hovels through far-stretching and gloomy forests, subsisting mainly by hunting and fishing, and often suffering from hunger and cold ; the latter blessed with smooth, cultivated fields, green meadows, and golden harvests, interspersed with comfortable farm-houses ; with the INTRODUCTION. 17 hum of business through populous cities, and along far-reaching lines of canals and rail-roads, and ships for foreign commerce, freighted with the productions of the soil, threading every channel and whitening every sea^— -when we observe this contrast, we can not fail to be struck with the convincing proof that " knowledge is power," and of the loss sustained on the one hand from its absence, and the advanfeges on the other of availing ourselves of its accumulated stores. 18 MECHANICS. CHAPTER II. GENERAL PRINCIPLES OF MECHANICS. SECTION I. GENERAL PROPERTIES OF MATTER. Having briefly pointed out some of the advantages to the farmer of understanding the principles of the maohiaes he constantly uses, we now proceed to an examination of these principles. It wUl be most con- venient to begin with the simpler truths of the science, proceeding, as we advance, to their application in the construction of machines. The term matter is apphed to whatever composes those substances which we perceive with our external senses ; and when we speak of a " body," we mean any thing composed of matter. Thus, wood, stone, water, and metal are matter ; while the mind and its quaUties are not matter. A stone, a block of wood, a bag of sand, and any other mass of matter, are termed bodies. DIVISIBILITY. Matter possesses several general properties, the ex- amination of which is both useful and interesting. One of these is its divisibility, or capability of being divided into small parts, and again divided, so far as we know, without any Umit. Many experiments show the great minuteness to which this division may be carried. For DIVISIBILITY. 19 example, a gold leaf may be hammered till jj^ of an inch in thickness, or one thousand times thinner than a leaf of this book. A silver wire may be coated with gold, and then drawn out so fine that the gold coating shall become a thousand times less than the gold leaf itself. So attenuated is one of the threads of a small spider's web, that half a pound would reach round the globe. It has been found that tripoli, a mineral used in the arts, is made up of shells of exceedingly minute animals, so small that a single cubic inch contains forty thousand millions, or fifty times as many individuals as there are human beings on the face of the earth. Hundreds of animalcules (or minute animals) have been seen with a microscope in a single drop of water, without in the least degree affecting its transparency. Some of these are so small that thousands could rest, without crowding, on the point of a pin; yet these have blood-vessels, muscles, and other parts, as well as larger animals. Still more minute appears to be the di- vision of those substances which are constantly throw- ing off odors or perfumes. A grain of musk will scent the air of a room for years, with particles inconceivably minute ; and a bed of flowers will fill the air with their odor, as hundreds of miles of the breeze successively pass over them, with an insensibly small portion of their own weight. But no division, however minute, ever destroys mat- ter ; every particle still retains its identity ; and the largest mountains, weighing millions of tons, are made up of these innumerable particles. 20 MECHANICS IMPENETRABILITY. Another property of matter is impenetrability, or the inahihty of two portions to occupy the same space at the same time. A- naU driven into wood only crowds the particles of wood asunder. Sugar will dissolve m water, but the particles of the sugar only pass ia between those of the water. "Wood becomes soaked with water by its entering the pores of the wood. These pores are seen by means of a powerful microscope, and are so small that one milhon have been computed to exist in a space not larger than a five-cent piece. INDESTRUCTIBILITY. Another property is indestructibility. Matter is separated and changed in form from one body to an- other, but never destroyed. "When wood is burned in the fire, it disappears ; but it is found that the smoke, vapor, and ashes weigh as much as before, although in a different form. The flashing of gunpowder appears to destroy it wholly ; but if aU the vapors and gases are retained within a vessel, they are found to weigh as much as the original sohd. Growing plants derive aU their weight from the soil and air ; they decay again, and form the manure for new plants ; but none of their particles are lost. They furnish food for ani- mals, or are manufactured into different substances, and, in all the changes they undergo, still retain their existence. INERTIA. 21 INERTIA. There is still another and very important quality of all material bodies, called inertia. This term express- es their passive state-i-that is, that no body (not hav- ing life)) when at rest, can move itself, nor, when in motion, can stop itself. A stone can not commence rolling of its own accord ; a carriage can not travel on the road without being drawn ; a train of cars can not commence 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, imless stopped by something else. A cannon ball rolled upon the ground continues rolling tUl its force is gradually overcome by the resistance of the rough earth. If a pohshdd metallic globe were driven swiftly on a level and pol- ished metaUio plane, it would continue in motion a long time and travel to a great distance ; but stUl the extremely minute roughness of the surfaces, with the resistance of the air, would continually diminish its speed untU finally stopped. A wheel made to spin on its axis continues till the friction at the axis and the impeding force of the air bring it to rest. But if the air is first removed by means of an air-pump, the mo- tion will continue much longer. Under a glass re- ceiver, thus exhausted, a top 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 fiirther shown by means of an interesting experiment 22 MECHANICS. Fans revolving in a vacuum. with the air-pump. Two fan-wheels, made of sheet Fig. 1. tui, one (a) striking the air with its edges, and the other (6) with its broad faces (Fig. 1), are set in motion ahke ; b 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 air exhausted, and motion given to them alike by the rack- work d, ■ they wlU both continue in motion during the same period. There is no machinery made by man ii'ee from the checking influence of friction and the air ; and for tliis reason, no artificial means have ever devised a perpet- ual motion by mechanical force. But we are not with- out a proof that motion will continue without ceasing when notliing operates against it. The revolutions of the planets in their orbits furnish a sublime instance ; where removed from all obstructions, these vast globes wheel round in their immense orbits, tlirough success- ive 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 greater must be the force. A small stone is more easUy thrown by the hand than a cannon ball ; speed is much more easily 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 require as great an effort of the arm to stop it INERTIA. 23 suddenly as to give it sudden motion. An unusual exertion of the team is required 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 p. 2 little instrument called the iner- tia apparatus {Fig. 2). A mar- ble or small ball is placed on a card (c) resting on a concave stand. A spriog snap is then u v^ made to strike the card, throwing Inertia Apparatus. ... i- i_ i t_ ^ • ji it to a distance, but leaving the ball upon the hollow end of the stand. The same ex- periment may be easily performed by placing a very small a~]^le or other sohd 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 stiU more striking: Procure Fig- 3. a thread just strong enough to bear three pounds, and hang upon it a weight of two pounds and a half. Another half pound would break it. Now tie an- other thread, strong enough to bear one pound, to the lower hook of the weight. If the lower thread be pulled grad- ually, the upper thread will of course break ; but if it be pulled with a jerk, the lower thread will break. If the jerk be very sudden, the lower string will break, even if it be considerably 24 MECHANICS. stronger than the upper, the inertia of the weight re- quiring a great force to overcome it suddenly. The threads used in this experiment may be easily had of any desired strength hy taking the finest sewing cot- ton, and doubling to any required 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 water are sometimes broken when hastily lifted by the handle. "When a bullet is fired through a pane of glass, the inertia re- tains the surrounding glass in its place during the mo- ment the ball is passing, and a round hole only is made ; whUe a body moving more slowly, and pressing the glass for a longer space of time, fractures the whole pane. •f ' SECTION II. MOMENTUM. The force which a moving body has to continue on- ward is called its momentum ; it is, in fact, the inertia of a moving body. When a force is first apphed to any heavy body, it moves slowly; but the little mo- mentum it thus acquires, added to the continued force, increases the velocity. This increase of velocity is of course attended with increased momentum, which again, added to the acting force, still farther quickens the speed. For this reason, when a steam-boat leaves the pier, and its paddle-wheels commence tearing MOMENTUM. 25 through the water, the motion, at first slow, is con- stantly accelerated till the increasing resistance of the water to the moving mass heoomes 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 trav- eler. If a rail-way passenger should step from a car when in fuU 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 swift- ness equal to thirty miles 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 driven against his wagon 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 furi- ously, and not the defendant, and he lost his suit. An African 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 * In ordinary practice, this is not strictly correct, as friction will make some difference. This influence ■will be more particularly considered on a subsequent page. Its omission here does not at all alter the principle under consideration. B 26 MECHANICS. on a bush, and jumped one side, when the animal, leaping swiftly on the concealed hush, was carried by momentum over the precipice. As a large or heavy body possesses greater moment- um than a small or light one, so any body moving with great speed possesses more than one moving slowly ; Fig. 4. for instance, the momentum of a ^HMI-h rifle baU 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 ap- plied with great advantage to many practical purposes. The momentum of the hammer drives the nail into the wood; for the mere pressure of its weight would 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-en- gine operates in a similar man- ner. The ram or weight, h (Fig. 4), is slowly Hfted by means of a pulley and wheel- work, worked Lby the handles or cranks, b b, un- ^ til the arms jDf the tongs which hold the ram are compressed in J the cheeks, i i, when it sudden- Piu Engine. \j faUg with prodigious force on the pile or post to be driven. In this way long posts of A THE PLY-WHEEL. 27 great size are forced into the mud of swamps and riv- er bottoms, where other means would fail. When a steam-engine is used for lifting the ram, the work is more rapidly performed. An interesting example of the use and efficiency of momentum is furnished by the water-ram, a machine for raising water, described on a subsequent page. THE FLY-WHEEL. 1h& fly-wheel, a large and heavy wheel used to reg- ulate the motion of machinery, derives its value from the power of inertia, or momentum, which prevents the machine from stopping suddenly when it meets with any unusual obstruction. In the common thrashiog- machine, it has been found that a heavy cylinder, by acting as a fly-wheel, renders 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 sud- denly thrown loosely forward, and again jerked back- ward, as the piston fell lightly and rose heavily. A fly-wheel attached to the machinery would have pre- vented this unpleasant jerking, and have enabled the horse, in consequence, to accomplish more work. In the pile-driving engine, where a great weight is sud- denly thrown loose from a height, the horses would be pitched forward when suddenly 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. 28 MECHANICS. Where there is a rapid succession of forces required in practice, the fly-wheel is usually of great advan- tage. Hence its use hi all revolving straw - cutters, where the knives make quickly-repeated strokes {Fig. 5). More recently it has been applied to the dasher -churn {Fig. 6), Fig. 6. Straw-cutter witlifly-wheel. where the rapid upright strokes are so well known to he very fa- tiguing 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, yet, when he turns a crank, there is one part chu^^^iZ^i^TM^iueijor equal- of the revolution where he i^^ng the motion. works to great disadvantage, and where his utmost force will not balance forty pounds. Hence, if the work is heavy, he may not be able to turn the crank, nor to do any work at aU. 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 supposing the fly-wheel actually creates power, for as much force is THE FLY-WHEEL. 29 required to give it momentum as it afterward imparts to the machine ; it consequently only accumulates and regulates power. A curious example of the effect of momentum is shown in the failure and success of two different modes of constructing wire fences with very slender wires for the boundaries of pastures. The unsuccessful mode consisted of tightly-stretched wires between solid posts not more than twelve to twenty feet apart. A side strain of only a few inches was enough to snap the wires ; consequently, a bullock plunging blindly against them could not be quickly enough checked in his mo- mentum, and such fences were therefore nearly useless without stronger wire. The successful mode was to stretch the wires well between strong and deeply-set posts some hundreds of feet apart, the intervening space being kept even by upright bars, but not posts. "When an animal accidentally struck this fence, the great length permitted it to yield sidewise far enough to ex- pend the momentum without rupture, when its elas- ticity at once' threw it back to its former place. 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 their advantages are considerable, but much greater as the velocity and momentum increase. I^ven on so smooth a surface as a rail-road, it was found, by experiments made some years ago, that when 30 MECHANICS. the machinery of a locomotive was placed 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 more severe for a team than a ton of wool or hay, which possesses considerable elasticity. ESTIMATING THE QUANTITY OF MOMENTUM. The quantity of momentum is estimated by the ve- locity and weight of the body taken together. Thus a ball of two pounds' weight moves with twice the force of a one-pound ball, the speed being equal ; a ten-pound ball with ten times the force, and so on. A body mov- ing at the rate of two feet per second possesses twice the mDmentum 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 would 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 float- ing near a pier wall may'approaoh 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 loco- motive, the force is almost irresistible. This circum- stance often insures the safety of the passengers ; for as nothing is capable of instantly overcoming so pow- erful a momentum, when accidents occur the speed is COMPOUND MOTION. 31 more gradually slackened, and the passengers are not pitched suddenly forward. A light wagon, T:apidly driven, possessing but little comparative force, is more suddenly arrested, and the danger is greater. "When two hodies meet from opposite directions, each sustains a shock equal to the united forces of hoth. Two men accidentally striking, even if walking mod- erately, receive each a severe blow ; that is, if each were walking three miles an hour, the shook 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 run- ning 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 ax will always strike more effective blows when made heavier, if not rendered unwieldy. SECTION III 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 taken together"; but if they act in opposite directions, the forces will tend to destroy each other. If two equal forces act in contrary directions, they will 6e completely neutraUzed, and no motion will be pro- duced. Thus, as an example of these forces— a bird flying at the rate of forty miles an hour, with a wind blowing forty miles an hour, will be driven onward by these two combined forces eighty miles an hour ; but ii2 MECHANICS. if it undertake to fly against such a wind, it will not advance at all, but remain stationary. A similar re- sult will take place if a steam-boat, having a speed of ten miles an hour, should first run down a river with a current of equal velocity, 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 Fig. 7. directions, but obliquely, the re- P J suit is found in the following ^^^/\ 7 manner : 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 b, then it will move inter- mediate between the two, in the direction of the diag- onal of the parallelogram a d, and to a distance just equal to the length of this diagonal or cross-diameter. When the forces act very nearly together, the paral- lelogram of the forces will be very narrow and quite Fig. 8. l°iigi with a long di- agonal (Fig-. 8); but .— """ if they act on nearly opposite sides of the ball, they will very nearly neutralize each other, and the Fig. 9. diagonal or result will be ^_______^>j^:fi____ very short, showing that ^ .1 " the motion given to the ball willbe very small (Fig-. 9.) These examples show the importance of having COMPOUND MOTION. 33 teams attached to a plow or to a wagon very nearly in a straight hne with the draught, or else a f)art of the force will be lost ; and also the importance, when several animals are drawing together, of their working as nearly as possible in the same straight line. Por, the more such forces deviate from a right line, the more they will 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 lower down, according to the rapidity of the stream and the slowness of the boat. Another instance is afforded when a ferry-boat is anchored, by means of a long rope, to a point some distance above {Fig. 10) ; the boat being turned Fig. 10. obhquely, will pass from one bank to the other by the force of the current. Here the water tends to carry the boat downward, while the force of the rope acts upward ; the boat passes between the two from bank to bank. The ascent of a kite is precisely similar, the wind and the string being counteracting forces. "When a vessel sails under a side-wind, the resistance of the keel against the water, and the force of the wind against the sail, act in diiTerent directions, and pro- duce a motion of the vessel between them. B2 34 ' MECHANICS. CENTRIFUGAL FORCE. All bodies, Vhen in motion, have a tendency to move forward in a straight line. A stone thrown into the air is gradually bent from this straight course into a curve by the attraction of the earth. When a ball is shot from a gun, the force being greater, it flies in a longer and straighter curve. A familiar example also occurs, while driving a wagon rapidly, in attempting to turn suddenly to the right or left ; the tendency of the load to move straight on will sometimes cause its overthrow. An observance of this principle would prevent the error which some commit by making sharp turns or angles in ditches and water-courses ; the onward tendency of the water drives it against the bank, checks its course, and wears away the earth. By giving the ditch a curve, the water is but slightly impeded, and a much larger quantity wiU escape through a channel of any given size. "When a grindstone is turned rapidly, the water upon its surface is thrown off" by this tendency to move in straight lines. In the same way, a weight fastened to a cord, whirled by the hand, will keep the cord stretch- ed during the revolution. The same principle causes a stone, when it leaves a shng, to fly off" in a hne. This tendency to fly off" from a revolving centre is called centrifugal force — ^the word centrifugal meaning fly. ing from the centre. Large grindstones, driven with great velocity by machinery, are sometimes split asun- der by centrifugal force. The most sublime examples of centrifugal force oc- cur in the motion of the earth and planets, which will be more fully explained on a future page. GRAVITATION. 35 CHAPTER III. ATTRACTION. SECTION I. GRAVITATION. The earth, as is well known, is a mass of matter in the form of a globe, the diameter being upward of 7900 mUes. From its enormous size and the small portion seen from one point, the surface appears flat, except where broken into mountains and valleys. The tendency which all bodies possess of faUing to- ward the earth is owing to the attractive force which this great mass of matter exerts upon them. This kind of attraction is called gravitation. The force with which a body is thus drawn is the weight of that body. When a stone is dropped from the hand, its velocity is at first slow, but continues to increase till it strikes the earth ; hence, the further it falls, the harder it will strike. This accelerated motion is precisely similar to that of a steam-boat when it first leaves the wharf; the force of gravity may be compared to the driving power of the engine, and the quickened velocity of the falhng stone to the increased headway of the boat. All bodies, whether large or small, fall equally fast, unless they are so light as to be borne up in part by the resistance of the air. In the first second of time they fall 16 feet ; in the next second, 3 times 16, or 48 feet ; in the third second, 5 times 16, or 80 feet, and so on. Or, if the whole distance fallen be taken togeth- 36 MECHANICS. er, they fall 16 feet in one second, 4 times 16 in two seconds, 9 times 16 in three seconds, and so forth. In other words, the whole distance is equal to the square of the time. This is plainly exhibited by the following table :* Seconds, from beginning to fall. 1 2 3 4 5 6 Whole height fallen in feet. 16 4X16 or 64. 9X16 or 144. 16X16 or 256. 25X1636X16 or 400. or 576. Space fallen in each sec- ond in feet 16 3X16 or 48. 5X16 or 80. 7X16 or 112. 9X16 11X16 or 144. or 176. A stone or other body will fall 1 foot in a fourth of a second, 3 feet the next fourth, 5 feet the third fourth, and 7 feet the last fourth ; which is the same as 4 feet in half a second, 9 feet in three fourths of a second, and 16 feet for the whole second. The depth of an empty well, or the height of a prec- ipice, may be nearly ascertained by observing the time required for the fall of a stone to the bottom. The time may be measured by a stop-watch, or, in its absence, a pendulum may be made by fastening a peb- ble to a cord, which will swing from the hand in reg- ular vibrations of an exact second each if the cord be 39 J inches long, or of half a second each if it be about 9 1 inches long. The velocity increases simply as the time — that is, the speed in falling is twice as great in two seconds as in one ; three times as great ia three seconds ; four times as great in four seconds, and so forth. A stone will fall four times as far in two as in one second, while * The distance, accurately stated, is sixteen feet and one inch for the first second, and hence the numbers in the table faU a very little Bhort of the distance actually faUen. GRAVITATION. 87 its velocity will be doubled ; nine times as far in three seconds, while its velocity will be tripled, &c. If a stone is thrown upward, its motion continues gradually to decrease, at the same rate as it increases in falling ; hence the same time is required to reach its highest point, as to fall from that point back to the earth. Therefore the velocity with which it is first projected upward is equal to the velocity which it at- tains at the moment of strilcing the ground. There is an exception, however, to this general rule. In a vac- uum it would be perfectly correct, but in ordinary prac- tice the resistance of the air tends to diminish the ve- locity while as cending, and still further to retard it while descending. For this reason, it will fall with less speed than it first arose. For heavy bodies and omall dis- tances, this exception would be imperceptible ; but with small bodies falling from great heights, the differ- ence will be considerable. The velocity of a stone after falling one second, or sixteen feet, is at the rate of thirty-two feet per second ; hence, if thrown upward at that rate, it will rise just sixteen feet high. After falling three seconds, the rate is ninety-six feet ; and hence, if projected upward at ninety-six feet per second, it will rise nine times sixteen feet, or one hundred and forty-four feet high. And so of other heights. Were it not for the resistance of the air, a feather would fall as swiftly as a leaden ball. This is conclu- sively shown by an interesting experiment. A tall glass jar [Fig. 11), open at the bottom, is covered with a brass cap, fitting it air-tight. Through this cap passes an air-tight wire, which, by turning, opens a small pair 38 MECHANICS. Fig. 11. I -xi- n of pincers. 'Within these are placed a feather and a half dollar, and the air is then thoroughly drawn from the receiver by means of an air-pump. The wire is turned, and the feather and coin both drop at once, and strike the bottom at the same moment. measuring the velocity. ^at- wood's machine. In consequence of the swiftness of falling bodies, it is not easy to meas- ure the exact distance through which they fall in a given time. There is an instrument, however, known as At- wood's Machine, which renders their motion much slower, at the same time reart«^I^/a«m^that the rate of increase in velocity is alike in a vacuum, precisely the same, and it Fig. 12. therefore admits of an exact measurement of ^^^ the descent. The principle of this machine /cJLj may be easily understood by Fig. 12, where n;JL^ two weights, hung on a fine silk cord run- ning over a wheel, exactly balance each oth- er. If now a small additional weight be placed on one of these, it will destroy the bal- ance, and the weight will begin to move downward. As this little weight has to impart mo- mentum to both the other larger weights, they will move as much slower than ordinary falling as the smaller weight is less than they. On this principle Atwood's Machine, represented by Fig: 13, is made. MKASURING THE VELOCITY. 39 Fig. 13. The two weights are first made to balance each other, when one of them is raised nearly to the wheel at c, and a small weight in the form of a short rod is placed across it. It immediately descends with ac- celerated or increasing velocity un- til it reaches the hole in the shelf a, through which the weight passes, but the rod is caught and retained. The motion is now no longer accel- erated, because the weights have become equal, and the descending one continues to fall uniformly at the same rate that it passed through the hole in the shelf, until it strikes the bottom. During this time its velocity may be accurately meas- ured by means of the clock and pen- dulum attached to the instrument. By sliding the shelf up or down, the velocity, after faUing through different spaces to reach the shelf, may be accurately determined. When the shelf is placed very near the top, so that but little ve- locity is acquired, the descending weight will move very slowly all the way down ; but when placed low- er, the weight continues downward more rapidly. It is necessary that the wheel turn with extreme ease, to effect which, friction-wheels, described hereafter, are usually employed. There are many instances showing the accelerated motion and increased force of falling bodies. When a Atwood's Machine far measuring the de- scent of bodies. 40 MECHANICS. large stone rolls down a mountain, it first moves slow- ly, but afterward bounds with rapidity, sweeping be- fore it all smaller obstacles. Hail-stones, although small, acquire such velocity as to break windows ; and but for the resistance of the air, they would be much more destructive. The blow of a sledge-hammer is more severe as it is lifted to a greater height. New- ton was first led to the examination of the laws of gravity by observing, when sitting under an apple-tree, that the fruit struck his hand with greatest severity when it fell from the top of the tree. It is not an unusual error to suppose that a large body wiU fall more rapidly than a small one. Some can scarcely believe that a fifty-six pound weight will not drop with a greater velocity than a small nail, not remembering that a proportionately greater force is re- quired to overcome the inertia and set the larger body in motion. This error existed for many centmies, from the time of Aristotle until Galileo first questioned its correctness. The celebrated experiment which estab- lished the truth on this subject, and led to the discov- ery of the laws of falling bodies just explained, and which formed an era in modern philosophy, was per- formed from the top of the leaning tower of Pisa. Galileo was a philosophical teacher, and, being a man who thought for himself, soon discovered, by reasoning, the errors that had been received without a doubt for more than twenty centuries. All the learning of the age and the wisdom of the universities were against him, and in favor of this time-honored error, the truth of which no one had ever thought of submitting to ex- periment. The hour of trial arrived, when he, an ob- MEASURING THE VELOCITY. 41' soure young man, stood nearly alone on one side, while the multitude, with all the power and confessed knowl- edge of the age, were on the other. The balls to be employed were carefully weighed and scrutinized to detect deception, and the parties were satisfied. The one ball was exactly twice the weight of the other. The followers of Aristotle main- tained that when the balls were dropped from the top of the tower, the heavy one would reach the ground in exactly half the time employed by the lighter ball. Galileo asserted that the weights of the balls would not affect their velocities, and that the times of descent would be equal. The balls were conveyed to the sum- mit of the lofty tower — the crowd assembled round the base — ^the signal was given — the balls were dropped at the same instant, and swiftly descending, at the same moment struck the earth. Again and again the ex- periment was repeated with uniform results. Galileo's triumph was complete^ — not a shadow of doubt remain- ed ; but, instead of receiving the congratulations of honest conviction, private interest, the loss of place, and the mortification of confessing false teaching, proved too strong for the candor of his adversaries. They clung to their former opinions with the tenacity of despair, and he was driven from Pisa.* * Mitchell's Lectures. 42 MECHANICS. SECTION 11 COHESION. The attraction of gravitation, as we have just seen, takes place between todies at a greater or less distance from each other. There is another kind of attraction, acting only when the parts of substances are in actual contact; this is called cohesion. It is this which holds the parts of a body together and prevents it from falling to pieces. It may be shown by taking two pieces of lead, and, after having made upon them two smoothly-shaven surfaces with a knife, pressing them Fig. 14. firmly together with a twisting motion {Fig. 14). jlgM' The asperities of the sur- Cohesive attracum m two lead balls. faceS are thuS pUShcd down, and the particles are brought into close contact, SO that cohesion immediately takes place between them, and some force will be required to draw them asunder.* Two pieces of melted wax adhere together in the same way. Melted pitch or other similar substance, smeared thinly over the polished surfaces of metal or glass, also causes cohesion to take place between them. Smooth iron plates, two inches in diameter, have been made to stick together so firmly with hot grease as to require, when cold, a weight of half a ton to draw them apart. Plates of brass of the same size, cemented by means - * That this Is not atmospheric pressure, like that which holds two panes of wet glass together, is shown by the fact that it requires nearly as great a force to separate them when they are placed under the exhausted receiver of an air-pump. Besides this, atmospheric pressure is much weaker than this force, with so small a surface. STRENGTH OF MATERIALS. 43 of pitch, required 1400 pounds. On this principle de- pends the efficacy of those suhstanoes which are used for cementing broken vessels. The most perfect artificial polish which can be given to hard metals is still so rough as to prevent the faces from coming into close contact ; hence they. must be either melted, or softened like iron when it is welded. The different degrees of cohesion which take place between the particles of various soils, to reunite them after they have been crumbled asunder, occasion the main difference between light and heavy soils. When a light soil becomes soaked with water, the particles adhere in a very slight degree ; and hence, when it be- comes dry again, it is easily worked mellow. But if it be of a clayey nature, too much moisture softens it like melted wax : the particles are thus brought into close contact, and strong adhesion takes place ; hence the hardness and difficulty of working such soils when again dried. This adhesion is lessened by applying sand, chip-dirt, straw, yard-manure, or by burning the earth, but more especially by thorough draining, which, preventing the clay from becoming so moist and soft, lessens the adhesion of its parts. Different substances are hard, soft, brittle, or elastic, according to the different degrees or modes of action in the attraction of cohesion. STRENGTH OF MATERIALS. It is a matter of great utility in the arts to determ- ine the different degrees of cohesion possessed by the different substances ; or, in other words, to ascertam their strength. This is done by forming them into 44 MECHANICS. rods of equal size, and applying weights to their lower extremities sufficient to break them, by drawing them asunder. The amount of weight shows their relative de- grees of strength. The following table gives the weights required to break the different substances, each being formed into a rod one quarter of an inch square : Woods. Ash, toughest 1000 lbs. Beech "718 " Box 1250 " Cedar 712 " Chestnut 656 " Elm 8S1 " Lo#ist 1280 " Maple ■ 656 " Oat, white 718 " Pine, white 550 " " pitch ■. 750 " Poplar 437 " Wahiut 487 " Metals. Steel, best 9370 lbs. " soft 7500 " Iron, wire 6440 " " best bar 4690 " " common bar 3750 " " inferior bar 1880 " " cast 1150 to 3100 " Copper, wire 3800 " cast 2030 " Brass 2800 " Platina wire 3300 " Silver, cast 2500 " Gold, cast 1250 " Tin 310 " Zinc, cast 160 " " sheet 1000 " Lead, cast 55 " " milled 207 " STRENGTH OP MATERIALS. 45 From these tatles we may ascertain the strength of chains, rods, &c., when made of different metals, and of timbers, bars, levers, swing-trees, and farm imple- ments, when made of woods. "Wood which will hear a very heavy weight for a minute or two will break with two thirds of the weight when left upon it for a long time. This explains the reason that store-house and barn timbers sometimes give way under heavy loads of grain, which ha«e appeared at first to stand with firmness. Although the preceding table gives the strength of wood drawn lengthwise, yet the comparative results are not greatly different when the force is apphed in a transverse or side direction, so as to break in the usual way. The following table shows the results of several ex- periments with pieces of wood one foot in length, one inch square, with the weight suspended from one end, bending them sidewise. White oak, seasoned, broke with 240 lbs. Chestnut, " " ITO " White pine, " " 135 " Yellow pine, " " 150 " Ash, " " 175 " Hickory, " « 270 " A rod of good iron is about ten times as strong as the best hemp rope of the same size. The best iron wire is nearly twenty times as strong as a hemp cord. Hence the enormous strength of the wire cables, sev- eral inches in diameter, which are employed for the support of suspension bridges. A rope one inch in diameter will bear about 5000 lbs., but in practice should not be subjected to more 46 MECHANICS. than half this strain, or about one ton. The strength increases or diminishes according to the size of the cross-section of the rope ; thus a cord half an iach in diameter will support one quarter as much as an inch, and a quarter-inch cord a sixteenth as much. A knowl- edge of the strength of ropes, as used by farmers in windlasses, pulleys, drawing loads, &c., would some- times prevent serious accidents by their breaking. The following table may therefora be useful : Diameter of rope or Pounds borne Breaking cord in inches. with safety. weigllt. One eighth 31 lbs. "IS lbs. One fourth 125 " 314 " One half 500 " 1250 " One 2000 " 6000 " One and a quarter 3000 " 7500 " One and a half 4500 " 12,500 " These results will vary about one fourth with the quality of common hemp. Manilla is about one half as strong as the best hemp. The latter stretches one fifth to one seventh before breaking. Wood is about seven to twenty times stronger when taken lengthwise with the fibres than when a side force is exerted, so as to split it. The sphtting of tim- ber or wood for fuel is, however, accomplished with a comparatively small power by the use of wedges, the force of heavy blows, and the leverage of the two parts. The attraction of cohesion is very weak in liquids ; it is sufficient, however, to give a round or spherical shape to very small portions or single drops, and to fur- nish a beautiful illustration, on a minute scale, of the same principle which gives a rounded form to the sur- face of the sea. In one case, cohesion, by drawing to- ward a common centre, forms the minute globule of CAPILLARY ATTRACTION. 47 dew upon the blade of grass ; in the other, gravitation, acting in like manner, but at vast distances, gives the mighty rotundity to the rolling waters of the ocean. CAPILLARY ATTRACTION. Capillary attraction is a species of cohesion ; it takes place only between soUds and liquids. It is this which holds the moisture on the surface of a wet body, and which prevents the water from running instantly out of a wet cloth or sponge. By touching the lower extremity of a lump of sugar to the surface of water in a vessel, capillary attraction will cause the water to rise among its granules and moisten the whole lump. It may be very distinctly shown by placing the end of a fine glass tube into water ; the water will rise in it above the level of the surrounding surface. If the bore of the tube be the twelfth of an inch in diameter (a, Fig. 15), it wDl rise a quarter of an inch; if but the Fig. 16. Capillary attraction in tubes. Capillary attraction between two panes of glass. twenty-fifth of an inch in bore, as b, it will rise half an inch ; but if only a fiftieth of an inch, the water will rise an inch. This ascent of the liquid is caused by the attraction of the inner surface of the tube, until the 48 MECHANICS. weight of the column becomes equal to the force of the attraction. Capillary attraction may be also exhibited by two small plates of glass, placed with their edges in water, in contact on one side, and a little open at the other side, as in Fig. 16, p. 47. As the faces of the plates approach each other, the water rises higher, forming the curve, a. Capillary attraction performs many important ofl&ces in nature. The moisture of the soil depends greatly upon its action. If the soil is composed of coarse sand or gravel, the interstices are large, and, like the larger glass tube, wiU not retain the rain which falls upon it. Such soils are, therefore, easily worked in wet weather, but become too dry in seasons of drought ; but when the texture is finer, and especially if a due proportion of clay be m.ixed with the sand, the interstices become exceedingly small, and retain a full sufficiency of moist- ure. If, however, there is too much clay, the soil is apt to become close and compact, and the water can not enter until it is broken up or pulverized. It is for tliis reason that sub-soil plowing becomes so eminently beneficial, by deepening the mellow portion, and thus affording, a larger reservoir, which acts like a sponge in holding the excess of falling rains, till wanted in the dry season. Por the same reason, a well-cultivated soil is found to preserve its moisture much better dur- ing the heat of summer than a hardened and neglect- ed surface. If capillary attraction should cease to exist, the earth would soon become a barren and uninhabitable waste. The moistm-e of rains could not be retained by the particles of the soil, but would immediately ASCENT OF SAP. 4& sink far down into the earth, leaving the surface at all times as dry and unproductive as a desert ; vegetation would cease ; brooks and rivers would lose the gradual supplies which the earth affords them through this in- fluence, and become dried up ; and all plants and all animals die for want of drink and nourishment. Thus the very existence of the whole human race evidently depends on a law, apparently insignificant to the un- thinking, but pointing the observing mind to a striking proof of the creative design which planned all the works of nature, and fitted them with the utmost ex- actness for the life and comfort of man. ASCENT OF SAP. The following interesting experiments serve to ex- plain the cause of the ascent of sap in plants and trees : Take a small bladder, or bag made of any similar Fig-^- substance, and fasten it tightly on a tube open at both ends {Fig. 17) ; then fill them with alcohol up to the point C, and im- merse the bladder into a vessel of water. The alcohol will immediately rise slowly in the tube, and if not more than two or three feet high, will run over the top. This is owing to the capillary attraction in the "X^^^ex- minute pores of the bladder, drawing the riSllTofsap. water within it faster than the same at- traction draws the alcohol outward. One liquid will thus intrude itself into"^nother with great force. A bladder filled with alcohol, with its neck tightly tied, will soon burst if plunged under water. If a bladder is filled with gum-water, and then immersed-as before, C 50 MECHANICS. the water will find its way within against a very heavy pressure. In this manner sap ascends through the minute tubes in the body of trees. The sap is thickened like gum- water when it reaches the leaves, and a fresh supply, therefore, enters through the pores in the spongelets of the roots by capillary attraction, and, rising through the stem, keeps up a constant supply for the wants of the growing tree. SECTIOM" III CENTRE OF GRAVITY. The centre of gravity is' that point in every hard substance or body, on every side of which the different parts exactly balance each other. If the body be a globe or round ball, the centre of gravity will be ex- actly at the centre of the globe ; if it be a rod of equal size, it will be at the middle of the rod. If a stone or any other substance rest on a point directly under the centre of gravity, it will remain balanced on this point ; but if the point be not under the centre of gravity, the stone wiU fall toward the heaviest side. Some curious experiments are performed by an in- genious management of the centre of gravity. A Fig. 18. light cylinder of cork or pasteboard contains a con- cealed piece of lead, g {Figure 18). The lead, being heavier than the rest, ■ will cause the cylinder to roll up an inclined plane, when placed as shown by the CENTRE OF GRAVITY. 51 Fig. 19. lower figure on the preceding en- graving, until it makes half a revo- lution and reaches the place of the upper figure, when it will remain stationary. If a curved body, as shown in Fig. 19, be loaded heav- ily at its ends, it will rest on the stand, and present a singular ap- pearance by not falling, the cen- tre of gravity lying between the Body singularly balanced iy tWO hcaVy pOrtlonS On the end of the stand. A light stick of some Fig. 20. length may be made to stand on the end of the finger, by sticking in two penknives, so as to bring the centre of grav- ity as low as the fiinger-end {Fig. 20). If any body, of whatever shape, be suspended by a hook or loop at its top, it wOl neces- sarily hang so that the centre of gravity shall be directly un- der the hook. In this way the centre in any substance, no Centre of gravity maintained hy two ji i • i -j, i penknives. matter how irregular its shape may be, is ascertained. Suppose, for instance, we have the irregular plate or board shown in the annexed figure {Fig. 21) : first hang it by the hook a, and the centre of gravity will be somewhere in the dotted line a b. Fig. 21. 52 MECHANICS. Then hang it by the hook c, and it wUl be somewhere in the line c d. Now the point e, where they cross each other, is the only point in both, consequently this is the centre sought. If the mass or body, instead of being flat like a board, be shapeless Uke a stone or lump of chalk, holes bored from different suspending points directly downward will aU cross each other exactly at the centre of gravity. LINE OF DIRECTION. An imaginary line from the centre of gravity perpen- dicularly downward to where the body rests is called the line of direction. Now in any sohd body whatever, whether it be a wall, a stack of grain, or a loaded wagon, the line of direction must fall within the base or part resting upon the ground, or it will immediately be thrown over by its own weight. A heavily and evenly loaded wagon on a level road wiU be perfectly safe, because the line of direction falls equally between the wheels, as shown in Fig. 22, by the dotted line, c being the centre . But if it pass a steep side-hUl road, throwing this line out- side the wheels, as in JFig. 23, it must be instantly overturned. If, however, instead of the high load represented in the figure, it be some very heavy material, as brick or sand, so as not to be higher than the square box, the centre will be much lower down, or at b, and thus, the line faUing within the wheels, the load wUl be safe from danger. Fig. 22. Fig. 23. Centre of gravity on level and inclined roads. LINE OF DIRECTION. 53 unless the upper wheel pass over a stone, or the lower wheel sink into a rut. The centre of gravity of a large load may be nearly ascertained by measuring with a rod ; and it may sometimes happen that by measuring the sideling slope of a road, all of which may be done in a few minutes, a teamster may save himself from a comfortless upsetting, and perhaps heavy loss. Again, a load may be temporarily placed so much toward one side, while passing a sideling road, as to throw the line of direction considerably more up hill than usual, and save the load, which may be adjusted again as soon as the dangerous point is passed. This principle also shows the reason why it is safer to place only light bundles of merchandise on the top of a stage-coach, while all heavier articles are to be down near the wheels ; and why a sleigh wiU be less likely to upset in a snow-drift, if all the passengers will sit or lie on the bottom. When it becomes necessary to build very large loads of hay, straw, wool, or other light sub- stances, the " reach," or the long connecting-bar of the wagon, must be made longer, so as to increase the length of the load ; for, by doubling the length, two tons may be piled upon the wagon with as much secu- rity from oversetting as one ton only on a short wagon. Where, however, a high load can not be avoided, great care must be taken to have it evenly placed. If, for instance, the load of hay represented by Figure 24 be skillfully Fig. 24. Fig. 25. Centre of gravity of an even and one-sided t load. built, the line of direc- 54 MECHANICS. tion will fall equally distant within each wheel ; but a sUght misplacement, as in Fig. 25, p. 53, will so alter this line as to render it dangerous to drive except on a very even road. Thus every one who drives a wagon should under- stand the laws of nature sufficiently to know how to arrange the load he carries. It is true that experience and good judgment alone will be sufficient in many cases ; but no person can fail to judge better, with the reasons clearly, accurately, distinctly before his eyes, than by loose conjecture and random guessing. Every farmer who erects a wall or building, every teamster who drives a heavy load, or even he who only carries a heavy weight upon his shoulder, may learn something useful by understanding the laws of gravity. It is familiar to every one, that a body resting upon a broad base is more difficult to overset than when the base is narrow. For instance, the square block {Fig. 26) is less easily tlirown over than the tall and narrow block of equal weight, because, in turning the square block over its lower edge, the centre of gravity must be lift- ed up considerably in the curve shown by the dotted line c ; but with a tall, narrow block, this curve being almost on a level, very little lifting is required. Hence the reason that a high load on a wagon is so much more easily over- turned than a low one. Of all forms, a pyramid stands the most firmly on its LINE OP DIRECTION. OD Fig. 27. base. The centre of gravity, c {Fig. 26), being so near the broad bottom, it must be elevated in a very- steep curve to throw the line of direction beyond the base. For this reason, a stone wall, or'the dam for a stream, will stand better when broad at bottom and tapering to a narrow top than if of equal thickness throughout. "When a globe or round ball is placed upon a smooth floor, it rests on a single point. If the floor be level, the line of direction will fall exactly at this resting-point {Fig. 27). To move the ball, the centre will move precisely on a level, without being raised at all. This is the reason that a ball, a cylinder, or a wheel is rolled forward so much more easily than any flat-sided or ir- regular body. In aU these cases, the line of direction, although constantly changing its place, still continues to fall on the very point on which the round body rests. But if the level floor is exchanged for a slope or in- Fie 28 clined plane {Fig. 28), the line of direction no longer falls at the touch- ing-point, but on the side from it downward ; the ball will therefore, , by its mere weight, commence roll- ing, and continue to do so tUl it reaches the bottom of the slope. Wheel-carriages owe their comparative ease of draught to the fact that the centre of gravity in the load is moved forward by the rolling of the wheels, on a level, or parallel vdth the surface of the road, just in the same way that the round ball rolls so easily. Each 56 MECHANICS. wheel supporting its part of the load at the hub, the same rule applies to each as to a ball or cyliader alone. Hence, on a level road, the line of direction falls pre- cisely where the wheels rest on the ground, but if the road ascend or descend, it falls elsewhere; this ex- plains the reason why it will run by its own weight down a slope. Whenever a stone or other obstruction occurs in a road, it becomes requisite to raise the centre by the force of the team and by means of oblique motion, so as to throw the wheel over it, as shown by Fig. 29. One of the reasons thus becomes very plain why a large wheel Fig. 30. will run with more ease on a rough road than a small- er one ; the larger one mounting any stone or obstruction without lifting the load so much out of a level or direct line, as shown by the dotted lines in the annexed figures {Figs. 29 and 30). Another reason is, the large wheel does Fig' 31- Fig- 32. not sink into the smaller cavities in the road. A self-supporting fruit- ladder {Figure 31) (the centre of gravity, when in use, being at or near ^the top) must have its A dangerims- legs more widely spread, Afirmly-sctfruU-laMeT. ly -set fruit- , -, . ■' * ladder. to be securc from fall- LINE OF DIRECTION. 57 ing, than if the centre were lower down. Hence such a position as in Fig. 32 would be unsafe. The support of the human body, in standing and walking, exhibits some interesting examples in rela- tion to this subject. A child can not learn to walk tiU he acquires skiU enough to keep his feet always in the Line of direction. When he faiLj to do this, he topples over toward the side that the line falls outside his feet. A man standing with his heels touching the wash- board of a room can not possibly stoop over without faUing, because, when he bends, the line of direction falls forward of his toes, the wall against which he stands preventing the movement of his body backward to preserve the balance. In walking, the centre rises and falls sUghtly at Fig 33. each step, as shown by the waved line in Fig. 33. If it were not for the bending of the knee-joints, this exer- cise would be much more laborious, as it would then become needful to throw the centre into an upward curve at every step. For this reason, a wood- en leg is more imperfect than the nat- ural one {Fig. 34). Hence the reason why walking on crutches is laborious and fatiguing, because at every onward step the body must be thrown upward in a curve, like a wagon mounting repeated obstructions. "When a load is carried on the shoulder, it should be so placed that the line of direction may pass directly through the shoulder or back down to the feet, Fig. 35, p. 58. An unskillful person will sometimes place C3 58 MECHANICS. Fig. 36. a bag of grain as shown in Fig. 36. The Une falUng outside liis feet, he is compelled to draw downward with great force on the other end of the bag. A man who carries a heavy pole on his shoulder should see that the centre is directly over his shoulder, otherwise he wLU be compelled to bear down upon the hghter end, and thus add in an equal degree to the weight upon his body. If an elliptical or oval body, Fig. 37, rest upon its side a, roU- iacr it in either direction elevates the centre, c, because it is nearest the side on which the body rests. If, when raised, it be suffered to fall, its momentum carries it be- yond the point of rest, and thus it Fig. 37. continues rooking untU the force is Fig. 38. spent. The course of the centre during these motions is shown by the curved dotted line, c. If it be placed upon end, as in Fig. 38, then any motion toward ei- ther side brings the centre of gravity nearer the touching-point, that is, causes it to descend, and the body consequently falls over on its side. This may be easUy illustrated with an egg, which wUl lie at rest vipon its side, but falls when set on either end. The rockers of chairs, cradles, and cribs are formed on the principle just explained. If so made that the LINE OP DIRECTION. 59 centre of gravity of the chair or cradle is nearer the middle of the rocker than to the ends, the rooking mo- tion will take place ; and when the distance from the centre of gravity to the ends of the rockers is but little Fig. 39. Fig^ 40. greater than the distance to the middle, c, as in Fig. 39, the mo- tion wiU be slow and gentle ; but if this difference be greater, as in Fig: 40, it wiU be rapid. "When the centre is high, the rockers must have less curvature than where it is low and near the floor. If the centre of gi-avity be nearer the ends than to the middle, the chair will immediately be overturned. This principle should be well understood in the construction of aU in- struments which move by rooking. 60 MECHANICS. CHAPTER IV. SIMPLE MACHINES, OR MECHANICAL POWERS. SECTIOSr I. ADVANTAGES OF MACHINES. The moving forces which are appUed to various use- ful purposes commonly require some change in veloc- ity, direction, or mode of acting before they accom- plish the desired end. For example, a running stream of water has a motion in one direction only ; by the use of machinery, we change this to an alternating mo- tion, as in the saw of the saw-miU, or to a rotatory or whirling motion, as in the stones of a grist-mill. The direct or straightforward power of a yoke of oxen is made, by the employment of the plow, to produce a side-motion to the sod as well as to turn it through half a circle. The thrashing-machine converts the slowly-acting pace of horses to the swift hum of the spiked cyUnder. Any instrument used for thus changing or modify- ing motion is called a machine, whether it be simple or complex in its structure. Thus even a crowbar, used in hfting stones from the earth, by diminishing the motion given by the hand and increasing its power, may be strictly termed a machine ; while a harrow, which neither alters the course nor changes the veloci- ty of the force applied, may with more propriety be re- garded as simply an implement or tool. In common THE LAW OF VIRTUAI, VELOCITIES. 61 language, however, these distinctions are not accurate- ly ohserved, and a machine is usually considered to be any instrument consisting of different moving parts. AU machines, however complex, may be resolved into two simple parts, or simple machines. These are, 1. The Lever ; 2. The Inclined Plane. The wheel and axle, and ike pulley, are modified ap- pUcations of the lever ; and the wedge and the screw of the inclined plane, as will be shown on the follow- ing pages. These six are usually termed the mechan- ical powers. As they really do not possess axiy power in themselves, ^ut only regulate power, the term " sim- ple machines" may be regarded as most correct. the law op virtual velocities. Before proceeding to the simple machines, it may be well to explain a very important truth, which should be considered as lying at the foundation of all mechanical philosophy, and which renders plain and simple many things which would otherwise seem strange or contra- dictory. This is, that the force required to hft any given body is always in proportion to the weight of that body, taken together with the height to be raised. For instance, it requires twice the force to raise two pounds as to raise one pound, three times the force to raise three pounds, and so forth. Also, twice as great a force is needed to elevate any weight two feet as one foot, or three times as great for three feet, and so on. Again, combining these together, four times as great a force is required to raise two pounds to a height of twcJ feet as to raise one pound only one foot ; eight times 62 MECHANICS. as great for four feet, and so on. This holds true, no matter by what kind of machinery it is accomplished. Now this may all seem very simple, but it serves to ex- plain many difficult questions in relation to the real power possessed by all machines. Take another example. Suppose that one wishes to raise a weight of 1000 pounds to a height of one foot. If his strength is only equal to 100 pounds, the weight would be ten times too heavy for him. He might, therefore, divide it into ten equal parts of 100 pounds each. Raising each part separately the required height of one foot, would be the same as raising one of them ten feet high. The weight is lessened ten times, but the distance is increased ten times. But there are some bodies, as, for example, blocks of stone or sticks of timber, which, can not well be divided into parts in actual practice. He therefore resorts to a machine or mechanical power, through which the same result is accomplished by raising the whole weight in one mass with his single strength ; but in this case as well as the other, the moving force which he applies rnust pass through ten times the space of the weight. "We arrive, therefore, at the general rule, that the distance moved by the weight is as much less than that moved by the power as the power is less than the weight. This rule is termed by some writers the " rule of virtual veloc- ities,^' virtual meaning not apparent or actual, but according to the real effect, because the increase in the velocity of the power makes up for increase in the size of weight. This rule will be better understood after considering its application to the different simple machines. THE LEVER. 63 SECTION II. THE LEVER. The simplest of all machines is the lever. It con- sists of a rod or bar, one end resting upon a prop ox ful- crum, F {Fig. 41), near virhich is the vyeight, W, moved Fig. 41 Lever of the second kind. by the hand at P. The stone may weigh 1000 pormds ; yet, if it is ten times as near the fulcrum as the man's hand is, a force of 100 pounds will lift it ; but it will be moved only a tenth part as high as the hand has been moved, as shown by the dotted lines. By placing the stone stiU nearer the fulcrum, still less will be the power required to raise it, but then the distance ele- vated would be also still less. By sufficiently increas- ing the disproportion between the two parts of the le- ver, the strength of a child merely might be made to move more than many horses could draw. These performances of the lever often excite aston- ishment at what appears to be out of the common course of things ; yet, when examined by the princi- ples of mechanics, instead of appearing matters of as- tonishment, they are found to be only the natural and necessary results of the laws of force. -In the case of the lever just described, it is often incorrectly supposed iJiat the power itself sustains the weight. But this ia 64 MECHANICS. not the case ; nearly the whole of it rests upon the ful- crum. We often see proofs of this error in common practice, where falcrums or props entirely insufficient to uphold the enormous weight to be raised are at- tempted to be used. If the weight, for instance, be ten times as near the fulcrum as to the power, then nine tenths of the weight rests upoii the fulcrum, and the remaining tenth only is sustained by the lifting power. The lever only allows the power to expend it- self through a longer distance, and thus, by concentra- ting itself at the weight, to elevate the latter through the shorter distance, according to the rule of virtual velocities already explained. The fulcrum may be placed between the weight and Fig. 42. the power, as in m^ Fig- 42, or the power may be Lever of the first und. ' ' placed between Fig. 43. the fulcrum and the weight, as in Fig. ^^ 43, the same princi- ple of virtual veloci- ties applying in all cases. Where the fulcrum is between the power and the weight, as in Fig. 42, it is called a lever of the first kind. Where the weight is between the fulcrum and the power, as in Fig. 41, it constitutes a lever of the second kind. Where the power is between the fulcrum and the weight, as in Fig. 43, it is termed a lever of the third kind. Laier of tke third kind. THE LEVER. 65 1. Many examples occur in practice of levers of the first kind. A crowbar, used to raise stones from the earth, is an instance of this sort ; so is a handspike of any kind used in the same way. A hammer for draw- ing a nail operates as a lever of the first kind, the heel being the fulcrum, the nail the weight, and the hand the power; the distance through which the handle passes being several times greater than that of the claws, the force exerted on the nail is increased in like proportion. A pair of scissors consists of two levers, the rivet being the fulcrum ; and in using them, as ev- ery one has observed, a gi-eater cutting force is exert- ed near the rivets than toward the points. This is ow- ing to the power being expended through a greater dis- tance near the points, according to the rule already explained. Pincers, nippers, and other similar instru- ments are also double levers of the first kind. A common steelyard is another example, the sfiding weight becoming gradually more efiective as it is moved further from the fulcrum or hook supporting the instru- ment. The brake or handle of a pump is a lever of tliis class, the pump-rod and piston being the weight. The common balance is still another, the two arms being exactly equal, so that one weight will always bal- ance the other, and on this its usefulness and accuracy entirely depends. The most sensitive balances have light beams with long arms, and the turning-point of hardened steel or agate, in the form of a thin wedge, on which the balance turns al- 66 MECHANICS. most without friction. Small balances have heen so skillfully constructed as to turn mth one thousandth part of a grain. 2. Levers of the second kind are less numerous, but not uncommon. A handspike used for rolling a log is an example. A wheel-barrow is a lever of the second kind, the fulcrum being the point where the wheel rests on the ground, and the weight the centre of gravity of the load. Hence, less exertion of strength is required in the arm when the load is placed near the wheel, except where the ground is soft or muddy, when it is found advantageous to place the load so that the arm shall sustain a considerable portion, to prevent the wheel sinking into the soil. A two- wheeled cart is a similar example ; and, for the same reason, when the ground is soft, the load should be placed forward to- ward the horse or oxen ; on the other hand, on a smooth and hard, or on a plank road, the load should be more nearly balanced. An observance of this rule would often save a great deal of needless waste of strength. A sack-barrow, used in barns and mills for convey- Fig. 45. ing heavy bags of grain from one part of the floor to another, is a le- ver nearly intermediate between the first and second kind, the weight usually resting very near- ly over the fulcrum or wheels. "When the bag of grain is thrown forward of the wheels, it becomes a lever of the first kind ; when back of the wheels, it is a lever ~sack-barrow. of the scoond kitid. As it is ESTIMATING THE POWER OP LEVERS. 67 used only on hard and smooth floors, and not, Hke the wheel-barrow, on soft earth, the more nearly the load is placed directly over the wheels, the more easily they will run. 3. In a lever of the third kind, the weight being farther from the fulcrum than the power, it is only used where great power is of secondary importance when compared with rapidity and dispatch. A hand- hoe is of this class, the left hand acting as the fulcrum, the right hand as the power, and the resistance over- come by the blade of the hoe as the weight. A hand- rake is similar, as well as a fork used for pitching hay. Tongs are double levers of this kind, as also the shears used in shearing sheep. The limbs of animals, gener- ally, are levers of the third kind. The joint of the bone is the fulcrum ; the strong muscle or tendon attached to the bone near the joint is the power ; and the weight of the limb, with whatever resistance it overcomes, is the weight. A great advantage results from this con- trivance, because a slight contraction of the muscle gives a swift motion to the limb, so important in walk- ing and running, and in the use of the arms. SECTIOH^ III. ESTIMATING THE POWER OF LEVERS. The power of any lever is easily calculated by meas- Fig. 46. uring the length of --■-'%i^' its two arms, that ~w is, the two parts in- to which it is divi- Lemr of the first kind. dcd by the Weight, 68 MECHANICS. fulcrum, and power. In a lever of the first kind, if the weight and power be equally distant from the ful- crum, they will move through equal distances, and nothing will he gained ; that is, a power of 100 pounds will hft a weight of 100 pounds only. If the power be pjg 47 twice as far as the weight, its force '''■"•--r:;., win be doubled: '^ "^'^'-ii--__. ^^ three times, it ^ ^y will be tripled ; Lever ofthe second kind. and SO forth. In a lever of the second kind, if the weight be equidistant between the fulcrum and power, the power wUl move through twice the distance of the weight, and the pow- er of the instrument wiU therefore be doubled ; if twice as far, it will be tripled, and so on, as shown in the an- nexed figures. The same mode of reasoning wUl ex- plain precisely to what extent the force is diminished in levers of the third kind. These rules will show in what manner a load borne on a pole is to be placed between two persons carrying it. If equidistant between them, each wUl sustain a like portion. If the load be twice as near to one as to the other, the shorter end wiU receive double the weight of the longer. For the same reason, when three horses are worked abreast, the two horses placed together should have only half the length of arm of the main whipple-tree as the single horse, Fig. 48. The farmer who has a team of two horses unlike in strength, may thus easUy kn9W how to adjust the arms of the whip- ple-tree so as to correspond with the strength of each. If, for instance, one of the horses possesses a strength ESTIMATING THE POWER OF I^EVERS. Fig. 48. 3. 69 as much greater than the other as four is to three, then the weaker horse should he attached to the arm of the whipple-tree made as much longer than the oth- er arm as four is to three. In all the preceding estimates, the influence of the weight of the lever has not heen taken into consider- ation. In a lever of the first kind, if the thickness of the two arms he so adjusted that it will remain bal- anced on the fulcrum, its weight will have no other effect than to increase the pressure on the fulcrum ; hut if it he of equal size throughout, its longer arm, being the heaviest, will add to its power. The amount thus added wiU be equal to the excess in the weight of this arm, applied so far along as the centre of grav- ity of this excess. If, for example, a piece of scantling twelve feet long, a b, Fig. 49, be used as a lever to hft the corner of a building, then the two portions, a c, c d, will mutually balance each other. If these be each a foot in length, the weight of ten feet will be left to bear down the lever. The oen- Fig. 49. 70 MECHANICS. tre of gravity of this portion will be at e, six feet fiom the fulcrum, and it will consequently exert a force un- der the building equal to six times its own weight. If the scantling weigh five pounds to the foot, or fifty pounds for the excess, this force will be equal to three hundred pounds. In the lever of the second kind, its weight operates against the moving power. If it be of equal size throughout, this will be equal to just one half the weight of the lever, the other half being supported by the fulcrum. "With the lever of the third kiad, the rule apphed to the first must be exactly reversed. COMBINATION OF LEVERS. A great power may be attained without the inoon- venienoe of resorting to a very long lever, by means of J,; 5D a combination of levers. ; : \ / In Fig. 50, the small & • \ ^ '^"""'jA^ weight P, acting as a moving power, exerts a three-fold force on the next lever ; this, in its turn, acts in the same degree on the third, which again increases the power three times. Consequently, the moving power, P, acts upon the weight, W, in a twenty-seven- fold degree, the former passing through a space twen- ty-seven times as great as the latter. A combination of levers Hke this is employed in self- regulating stoves. It is in this case, however, used to multiply instead of to diminish motion. The expan- sion of a metallic rod by heat the hundredth part of an inch acts on a set of iron levers, and the motion is in- WEIGHING MACHINE. 71 creased, ty the time it reaches the draught-valve, to about one hundred times. A more compact arrangement of compound levers is shown in Fig. 51, where the power, P, acts on the lever A, exerting a force on the lever B five times as great as the power. B acts on the lever C with a force increased three times, and this, again, on the weight, W, with a four-fold force. Multiplying 5, 3, and 4 to- gether, the product is 60 ; hence a force of one pound at P wiU support 60 pounds at W. By graduating (or clll| ' 160 1 ■ \«s 120 100 ao 60 40 JO The marTdngs of the Self-recording Dynamometer. and they may be accurately examined and read off at leisure, a and b representing the forces of two different plows, drawn through a single furrow across the field. The motion of the paper is effected by being placed on two rollers, one of which unwinds it from the other. 126 MECHANICS. This roller is made to turn by means of a wheel run- ning on the ground, which gives motion to the roller through an endless chain, working a cog-wheel by means of an endless screw. The cylindrical dynamom- eter, shown in Fig. 101, is used for this purnose, length- Fig. 101. wise upon which the two _j_if i^ "TillT|i||ir^!W_^ rollers are placed for hold- C^^iJlJIillll^^ ing the paper. "With this in- SSAs strument a permanent reg- \^^^ ister might he made of the Self-recording Dynamometer. force required for different plows, the accuracy of which none could dispute. DYNAMOMETER FOR ROTARY MOTION.- All these dynamometers apply only to simple, on- ward draught, as in plowing, drawing wagons, harrow- ing, &c. There is another, represented in Fig. 102, of very ingenious but complex construction, which shows the force required in working any rotary machine, such as thrashers, straw-cutters, and mills, and showing, at the same time, the velocity, and recording the number of revolutions made. The whole machine is supported by a cast-iron frame- work, on four small wheels with flanges, like the wheels of rail-cars, that it may be conveniently run up on a temporary rail- way to the thrashing or other ma- chine to be tried. The band- wheel, /, on the shaft, e, is connected with the machine under trial, and the force is supposed, in this instance, to be applied by hand to the handle, a, on the fly- wheel. When the fly-wheel is turned in the direction shown DYNAMOMETER FOR ROTARY MOTION. 127 by the arrow, it causes the two cog-wheels to revolve, Fig. 102. Dynamometer /or measuring the force and veJacity of thrashing-machines. and moves the band in the direction shown by the oth- er arrow. Now, whatever force is required to turn the wheel,/, connected with the machine under trial, tnust be overcome by a corresponduig force appUed to the handle, a, because the wheel-work is so adjusted that this handle moves with the same velocity as the band on the band- wheels. The wheel, /, being connected by the band to the wheel, d, which is on the same axis or shaft as the cog- wheel, I, the resistance of the machine under trial tends to keep the cog-wheel, I, from turning, until enough force is apphed to the handle, a, to set the cog-wheel, k, in motion. Now the greater the resistance, the greater will be the power needed at the handle. This 128 MECHANICS. power, therefore, is measured accurately in the follow- ing manner : The axle, g, of the cog-wheel, I, rests at its further end in an ohlong hole or mortise, that allows it liberty •to play, or rattle up and down within narrow hmits. This same axle, g, passes through a hole in the lever, i, so that when it rattles up and down, it carries this lever up and down with it. The other part of the lev- er turns on the shaft, h, of the other cog-wheel. Now when the man at the fiy-vsrheel applies his force to the handle, a, the resistance of the machine under trial causes the cog-wheel, I, to refuse to turn ; consequently, his force, instead of turning it, lifts it up in the mortise, and raises the lever with it. As he in- creases his force against the handle, let weights he himg on the lever, until, at the very moment that the wheel begins to revolve, the weights shall be just heavy enough to keep the lever down in the mortise. This weight, therefore, will measure the exact force need- ed to turn the yiachine : the greater the resistance of the machine, the greater must be the weight. There is another weight, J, used to balance the lever and cog-wheel, I, while the machine is at rest, or before the force is applied to it, so that the weight at m shall represent the force truly. The weight, m, is, of course, to be multiphed by the power it exerts on the lever, i, which should be graduated like the bar of a steelyard. There are a few other parts of this dynamometer not yet described. One is the cylinder, o, filled with oil, in which a perforated piston works, preventing the rapid vibration of the lever, i, as the force varies, pre- DYNAMOMETER FOR ROTARY MOTION. 129 cisely similar to the cylinder of oil described in Fig. 99. Another part is the pendulum, p, with the wheel, r, which measures the time. The use of this instrument has heen already attend- ed with some important results in detecting the great amount of friction existing ia some thrashing-machines of high reputation, which has been found to amount, in certain cases, to more than one half of the whole power applied. It is only by detecting so great a waste that we are enabled to take measures for its prevention. F2 130 MECHANICS. CHAPTER VII. CONSTRUCTION AND USE OF FARM IMPLEMENTS AND MA- CHINES. SECTION I. The application of mechanical principles in the structure of the simpler parts of implements and ma- chines has been treated of in a former part of this work. It remains to examine more particularly those machines chiefly important to the farmer, and to show the appUcation of these principles in their use and op- eration. PLOWS AND PLOWING. One great difference between good and bad plows is in the form of the mould-board. To understand the best form, it must be observed that the slice is first cut by the forward edge, and then one side is gradually raised until it is turned completely over, or bottom side up. To do this, the mould-board must combine the two properties of the wedge and the screw. The position of the furrow-slice, from the time it is first out tni completely inverted, may be represented by placing a leather strap flat upon a table, and then, while holding one end, turning over the other, so as to bring that also flat upon the table, as in Fig. 103. Now the mould-board should have just such a shape as will fit the fuxrow-slice while in the act of turning PLOWS AND PLOWING. 131 over, else it will wear unequally, become clogged with soil where the earth rubs slightly, and require greater strength in the team. By examining, it will be found that, although the strap {Fig. 103) twists hke a screw, Fig. 103. yet all parts will be straight if measured across at right angles, as shown by the dotted lines. Therefore, by applying this principle, the farmer can judge of one im- portant quality in selecting a plow. If, for example, he finds that a straight-edged stick will be 'flat upon Fis- iM- the face at right angles to the hne of motion, as shown by the dotted lines in Fig. 104, the mould-board will be so far right; but if the straight edge must be placed in other posi- tions, as ia Fig. 105, it is de- fective in form. A mould- board may be much modified, with.this principle preserved in every instance ; that is, it may be short, so as to raise the earth abruptly, or it may be long, so as to raise it gradually; it may be adapted to a deep furrow, lifting the furrow-slice to a considerable height, or to a shallow one, throwing it quickly over. These modifications are required for dif- ferent soils and for different purposes. When, for ex- ample, it is desired to break up the slice and pulverize a heavy soil, the twist must be short and abrupt ; when a sod in fight soil is to be inverted smoothly, the mould- board must be longer, and the twist more gradual In 132 MECHANICS. all mould-toards, care must be taken that the soil is not lifted so abruptly as to throw it forward, instead of simply turning it over. Another defect in some plows is too blunt or thick a Fig. 106. wedge formed by the share and mould- board. By the plow represented in Fig. 106, the earth must be thrown from the land-side into the furrow with a velocity about equal to the motion of the team; but by the one shown by Fig. 107, the team moves twice as fast as the earth is ' thrown by this longer wedge. C on- sequently, according to the rule of virtual velocities (ah-eady explained), as applied to the wedge, there is a great gain in power. Care must be taken, how- ever, not to make this wedge too long, else the friction of a greater length of sod may overbalance the advant- age. An attention to such principles as these has result- ed in an extraordinary improvement within the past thirty years. Plows are madp with one third the for- mer cost, that will do more than twice as much work with the same strength of team, and do it so much better, that larger crops may be reaped from the same land. These advantages are so great, that on all the arable land of the Union there must be a yearly sav- ing of ten millions of dollars in the work of teams, one million in the price of plows, and millions of bushels in the aggregate increase of crops by good tillage. In the two annexed figures we have a represeotation of an old and an improved plow. PLOWS AND PLOWING. 133 Fig, 108 is such a plow as is now used in some Fig. 108. parts of G-ermany. Fig. 109 is one of the best im- Fig. 109. proved cast plows. Nearly as great a difference ex- ists between the plows used here fifty years ago and at the present time. Some portion of this great im- provement may have been effected by persons not fa- miliar with science ; but if such persons were enabled to achieve so much, with the few truths which they had themselves laboriously discovered, how much more they might have accomplished if they had enjoyed the advantages of aU that strong-minded men have discov- ered during the course of ages, and which is collected together in the form of modern science. How much more, too, would be saved in time and tedious exper- iments, by applying the principles of science already 134 MECHANICS. discovered, than by ascertaining what we wish to know only by long-repeated trials. TRENCH AND SUBSOIL PLOWING. When the common two-horse plow alone is used by farmers, it pulverizes the soil only a few inches in depth, and its own weight, and the tread of the horses on the bottom of the furrow, gradually form a hard crust at that depth, through which the roots of plants and the moisture of rains do not easily penetrate. Hence the roots have only a few inches of good soil on the surface of the earth for their support and nourish- ment ; and when heavy rains fall, the shallow bed of mellow earth is soaked and injured by surplus water. Again, in time of drought, this shallow bed of moist- ure is soon evaporated, and the plants suiTer in conse- quence. But, on the other hand, when the soil is made deep, it absorbs, like a sponge, aU the rains that fall, and gradually gives off the moisture as it is wanted dur- ing hot and dry seasons. For this reason, deep soils are not so easily injured by excessive wetness, or by ex- treme drought, as shallow ones. In addition to this advantage, they allow a deeper range for the roots in search of nourishment. Soils are deepened by trench-plowing and by sub- soiling. By trench-plowing, the common plow with a mould-board is made to enter the earth to an unu- sual depth, and to throw up a portion of the subsoil, covering with it the top-soil which is thrown under. A subsoil plow, on the contrary, only loosens the sub- soil, but does not lift it to the surface. THE DOUBLE MOULD-BOARD TRENCH-PLOW. 135 When a mixture of the subsoil with the surface tends to render the whole richer, trench-plowing is best ; but when the subsoil is of a more sterile character, it should be only loosened with the subsoil plow, and more cau- tiously intermixed with the richer portion above. It often happens that the subsoil plow is very use- ful in loosening the soil for the purpose of allowing the trench-plow to run more freely through it. THE DOUBLE MOULD-BOARD TRENCH-PLOW. This plow, sometimes called the Michigan Double Plow, is represented in Fig. 110. It has two mould- Fig. 110, boards on one beam. The forward or small one pares off the surface or sod, and throws it into the previous furrow, usually to a depth of three to five inches. The larger one follows closely, lifting the under-soil upon the top, and in sward land completely burying the sod with the mellow earth from below. This is the best implement for trench-plowing yet introduced into prac- tice, and with double the ordinary amount of team, will cut to a depth of nine to twelve inches. 136 MECHANICS. THE SUBSOIL PLOW, represented in Fig. Ill , consists of a narrow, Lorizon- Fig. 111. Subsoil plow, tal, wedge-like share for loosening the earth, and con- nected with the beam by a strong plate of metal run- ning edgewise, so as to cause Httle resistance through the soU. This plow follows in the furrow after a com- mon plow, loosening but not lifting out the earth. The operation is shown in Fig. 112. The benefit of sub- Fig. 112. Svbsoil plowing in the furrow of a common plow. soihng wiU last three or four years ; but it is of great importance that land be weU underdrained, for if the earth becomes heavily soaked with water, it settles down into one compact mass, and the advantages of the operation are lost. FOWLER S DRAINING PLOW. The mole-plow, for forming a sraaU hoUow passage beneath the soil, by means of a sharp iron plug forced through it at the lower end of a thin coulter, has been 139 already described. A great improvement has teen made in this machine by the invention of the Draining plow, Fig. 113, opposite, which not only forms a hole through the suhsoU, hut fits into it at the same ope- ration earthen pipe or tubular tUe, forming at once a perfect and durable under-drain. The pieces of tile or pipe, which are about a foot long, are strung on a rope, as shown in the foreground of the engraving. This rope is attached to the back end of the iron plug, and is dravni forward through the earth as the plug ad- vances, thus fitting the hole with tile as fast as it is formed. The only trace left on the surface of the earth is a narrow slit made by the coulter, an invisible drain being formed beneath it. The frame- work to which the coulter and plug are attached is drawn forward by an iron rope (made of twisted wire) wound upon a windlass or capstan work- ed by horses. Drains forty rods long are completed at one operation. A short piece of ditch is first dug for the admission of the plug, and strings of pipe, each fifty feet long, are successively added, and when done the whole of the rope is withdrawn. When the surface of the ground is uneven, an in- genious contrivance preserves a straight and uniform slope to the drain. The coulter is worked up or down by the man who stands on the frame, by means of a wheel and screw, his eye being guided by a try-sight on the frame, and a cross-staff at the end of the field, set so as to give a proper slope. This machine, when tried in England, has been found to accomplish the work of draining with less than one half the ordinary expense. 140 MECHANICS. THE PARING PLOW consists merely of a flat blade, -wliicK runs beneath the surface, shaving off the roots, but not moving the soil (_Fig. 114). It is used in cutting turf for burning, . 114. Faring plow. and for destroying thistles and other deep-rooted weeds. "When made light for a single horse, it is sometimes used advantageously for cutting the grass and weeds between rows of corn. A two-horse paring plow has been lately constructed, in which the depth of cutting is accurately regulated by wheels placed on an axle like those of a cart. The cast-iron blade, which cuts about three feet wide, is raised or depressed by means of screws passing through the axle. Its chief utility is in destroying grass and weeds before the sowing of broadcast crops. THE GAMG PLOW consists of three or four small mould-boards placed side by side {Fig. 115), and is used for shallow plowing, or burying manure or seed on inverted sod, without dis- turbing the turf beneath. In those of the best con- struction, the depth is regulated by wheels, and the breadth of the furrows by turning the cross-beam more THE HARROW. 141 Gang plow. or less obliquely, by means of a fixed contrivance for this purpose. SECTION II. PULVEE.IZEK.S. Fig. 116. The fine pulverization of the soil, for the ready ex- tension of the fine roots of plants, and for the thorough intermixture of manure, is of great importance to the farmer. It is but partially accompKshed by the plow, which crumbles the soil only so far as may be done by the act of turniog it over. Hence additional imple- ments are needed for this purpose, among which are the harrow, the cultiva- tor, and the clod-crusher. THE HARROW The common form of the harrow is represented by Fig. 116, which con- sists of two parts hung Scotch or square harrow. 142 MECHANICS. Fig. lis. together by hinges, so as to bend and fit an iineven surface of land, and to be folded for carrying in a cart or wagon. The dottted lines show the track of each Fig. 117. tooth. The Geddes Harrow, rep- resented in Fig. 117, is supe- rior to the square harrow on ac- count of its drawing more stead- ily from a centre, and its wedge- form frame passing more freely past any unusual obstruction. To prevent the central part from being lifted by the draught, the draught- oeides Harrow. chain is fastened to the side-beams, as in Fig. 118. The teeth of harrows are often made too large and too few in number. Small and very numerous teeth pulverize the soil more finely and rapidly. They should be so placed that the corners, like wedges, and not the sides, may cut the soil in their onward progress ; and if the forward half of the teeth were made sharp and flat, similar to the coulter of a plow, they would not only run more easily, but cut and pul- verize clods more efficiently. This form of the teeth would admit of the use of cast-iron, which would be cheap and durable. The Norwegian Harrow, Fig. 119, is a new ma- chine for pulverizing the soil, which performs the work in a very perfect manner, by turning up instead of packing down the earth. Two rows of star-shaped tines play into each other, and produce a complete self- CULTIVATORS. Fig. 119. 143 Norwegian Harrow, kept from clogging hy two cylinders of teeth playing into each other, cleaning action, preventing clogging even in quite ad- hesive soils. CULTrVATORS. The cultivator is used for loosening and pulverizing the soil, and for cutting and destroying weeds. The usual form is represented in Fig. 120, where the wheel Fig. 120. Common Cultivator. in front regulates the depth of the teeth. The width is altered hy expanding or contracting the two outer beams. Various sorts of teeth are used, according to the na- ture of the work, and they are made of steel or qast- 144 MECHANICS, iron. The cast-iron teeth, represented in Fig. 120, are well adapted for cultivating the rows of Indian corn and other hoed crops, where the soU is already moderately mellow. For harder soOs, the teeth should be in the form of claws, as shown in Fig. 121, their Fig. 121. Claw-toothed cultivator for hard ground. sharp, wedge-form points penetrating and loosening the earth with comparative ease. A very efficient culti- vator is made by using both kinds of teeth in the same implement, placing the claws forward for breaking the hard earth, and the broader teeth behind for stirring it. Steel plates, with sharp or " duck-feet " edges screw- ed at the lower extremities of the teeth. Fig. 122, are Fig. 122. useful for paring, or cutting the roots of weeds ; and formed like the mould-board of a plow, they are some- times used for throwing the mellow earth toward the row, or, when reversed, from it. In all cases, the teeth should be so long and the frame-work high enough above ground to aUow room CLOD-CRrsHERS. 145 for the weeds to gather and ia'.i off, even when the teeth are deepest in ani the la'.id the foulest. Two-horse cultivators are /ery useful in pulverizing the surface of inverted sod, and fitting it for the recep- tion of seed. They run on wheels, and an apparatus is attached for lowering gr raising the frame-work and regulating the depth of the teeth. Garrett's Horse-hoe, an English invention, is a mod- ification of the cultivator, and is used for cultivating carrots and other root-crops in drills, cleaning eight or ten rows at once. It is furnished with sharp horizon- tal blades, which run beneath the surface, and shave off and destroy all the weeds within an inch of the rows of young plants. These rows, having been planted by means of a drilling-machine, are straight and per- fectly parallel, and the operator has only to watch one row and guide the blades for that row, the apparatus being so contrived that the blades for the other rows shall run at the same distance from them. Fig. 123 represents an end view of this implement. Fig. 133. GarretVs Horse-hoe — End view. G 146 MECHANICS. It exhibits the apparatus by which the length of the axle is altered to suit all kinds of planting ; by which each hoe is kept independent of the others, so as to suit the inequalities of the ground, and by which they can be set any width, from seven inches to thirty. It shows the oblique angle at which they run — this obliq- uity being easUy altered to any desired degree : this is effected by a movement of the upper handle represent- ed in the figure. By the lower handle the whole is accurately guided. It is said that two men, one to lead the horse, and the other to guide the implement, wiU dress ten acres of root-crops in a single day, and that it has proved eminently a labor-saving machine. CLOD-CRUSHERS. In clayey soUs, clods are often formed in abundance during the process of cultivation. These become very hard in dry weather, and prevent the proper extension of the fine roots of plants in search of nourishment, and also the intermixture of manure with the soil, without which it has been found that two thirds or even three fourths of the value of manure is lost to growing crops. different modes of pulverizing the clods have been adopted. The simplest is the " drag-roller^'' repre- sented in Fig. 124. It is made of a log or portion of Fig. 124. Clod-crusher. a hollow tree, into which a common two-horse wagon CLOD-CRUSHERS. 147 tongue has been fitted, by which it is dragged over the ground without rolling, grinding to powder, in its progress, every clod over which it passes. The greater the diameter of the log, the less will be the lia- bility of its clogging by gathering the clods before it. It may also be made of a half log with the round side downward. Fig. 125 represents a similar implement Fig. 125. One-horse Clod-crusher. for one horse, and is used for working between the rows of corn in cloddy ground. The use of these simple implements, by reducing rough fields to a condition as mellow as ashes, has in some instances been the means of doubhng the crop. It is necessary that the soil be dry when they are used, to prevent its packiijg together. CrosskiWs Clod-crusher is a more powerful and Fig. 126. CrosskiWs Clod-crusher. 148 MECHANICS. more costly implement {Fig. 126). It consists of about two dozen circular cast-iron disks, placed loosely upon an axle, so as to revolve separately. Their outer circumference is formed into teeth, which crush and grind up the clods *as they roll over the surface of the field. Every alternate disk has a larger hole for the axle, which causes it to rise and fall while turning over, and thus prevent the disks from clogging. It can be used only when the ground is dry. SECTION III. SOWING-MACHINES. SowiNG-MACHiNEs, for whcat and other grains, pos- sess great advantages over hand-sowing. All the seed being deposited by them at nearly a uniform depth, and completely covered with earth, it vegetates and grows evenly, and the plants are uniformly strong and vigorous. A less quantity of seed is required, and the crop is heavier. Small seeds, such as carrots and turnips, can be sown evenly and rapidly only by means of drills adapt- ed to these seeds, and hence drdling-niachines are in- dispensable in the cultivation of such root-crops. A great number of different drills have been made for sowing grain, the general principles of which can be only noticed in this treatise. The seed is delivered by means of a revolving cylinder, in the surface of which small regular cavities have been made, which constantly carry off and drop measured portions of the grain. The motion of this cylinder is increased or less- ened by means of wheel-work, according to the quan- Fig. 127, Grain-drilling Machine. SOWING-MACHINES. 151 tity of seed to be sown. As soon as the seed di-ops from the revolving cyhnder, it falls down either through a hollow coulter, or through a tube which opens just behind a coulter, into the bottom of the furrow, and is immediately buried by the earth falling back upon it after the coulter has passed. DriUs for sowing small seeds are usually furnished with a spindle having circular brushes, which press the bottom of the hopper, and force the seed through small holes made for its escape. For planting corn, beans, and other crops cultivated in drills and hills, the machines are so regulated as to drop either in hills or in uniform rows, and they do the work more evenly than when performed by hand. The coulters or tubes for depositing the seed should, in all machines of this kind, be made sharp and not rounded on the forward part, that the draught may be easier. A simple grain-drill is represented in operation by Fig. 127, tod one of more finished construction by Fig. 128, showing the cog-wheel gearing for regulat- ing the quantity of seed, and the chains for lifting up the discharging tubes from the ground when not in use. A very simple machine for sow- ing §pass, as well as other small seed, by hand, is shown in the an- nexed figure. It consists of a light trough, contain- Fig. 129. 152 MECHANICS. ing the seed, which is distributed through holes in the zinc bottom by the vibrations of a notched rod, and any desired quantity of seed accurately regulated. HORSE-RAKES. In all labor-saving contrivances, the greatest advant- age is gained where the work originally performed by the hand is light, or where much exertion of strength is not required. An example of this kind occurs in the use of hand-driUs for sowing small seeds, such as tur- nips and carrots. These, when planted by the unas- sisted hand, require but little power, but the operation is very slow. A hand-drUl enables the laborer to apply his whole strength profitably, with an increase in ef- fect of at least forty or fifty times. A similar advant- age is gained by the use of the horse-rake, where the full strength of a horse is made to accomplish the moderate labor of the hand-rake, and to perform an amount equal to at least ten men. With the simplest form of the horse-rake, sixteen acres of heavy hay have been collected by one horse in a day, and with the re- volving-rake, twenty to twenty -five acres. The simplest form of the horse-rake is represented in Fig. 130. It is made of a piece of strong scanthng three inches square, tapering shghtly toward the ends, for the purpse of combining strength with hghtness, and ia which are set horizontally about fifteen teeth, twenty-two inches long, and an inch by an inch and three fourths at the place of insertion, tapering on the under side, with a slight upward turn at the points, to prevent their running into the ground. The two outer teeth should be cut off to about one third their first HORSE-RAKES. Fig. 130. 153 Simple Horse-rake. length, and draught-ropes attached. If they are too short, the teeth will be hard to guide ; if too long, the rake is unloaded with difficulty. Handles serve to guide the teeth, to lift the rake from the ground in avoiding obstructions, and to empty the accumulated hay. In using this rake, the teeth, instead of moving on their points as in the common hand-rake, run flat upon the ground, passing under and collecting the hay. When full, the horse is stopped, the handles thrown for- ward, the rake emptied and lifted over the winrowthus formed. The winrows are made at right angles to the path of the rake, as each load is deposited opposite the last heap formed in previously crossing the meadow. A few hours' practice enables any one to use this rake without difficulty ; the only skill required is to keep the teeth under the hay and above the ground. "When smaU obstructions occur, the handles are depressed, and the points of the teeth rise and pass freely. Over large obstructions, the rake must be lifted. By shortening the teeth, it may be used on the roughest ground. In addition to raking, this implement may be em- G2 154 MECHANICS. ployed for sweeping the hay from the •winrow and drawing it to the stack. It is also useful for cleaning up the scattered hay from the meadow at the close of the work, for raking grain-stubhle, and for pulling and gathering peas. Its chief advantages over other horse-rakes are its simplicity, cheapness, and little liability to get out of order — adapting it to small farms — and its superior fitness for uneven surfaces. If made of the toughest wood, and with the proper taper in the main parts for hghtness and strength, according to the principles al- ready pointed out in a previous chapter, it is easily lifted, and its use not attended with severe labor. The Revolving Horse-rake, Fig. 131, is similar in Fig. 131. Revolving Korse-rdk< its mode of operation, possessing, however, the great advantage of unloading without hfting the rake or stop- ping the horse. It has a double row of teeth, pointing each way, which are brought alternately into use as the rake makes a semi-revolution at each forming win- row in its onward progress. They are kept flat upon the ground by the pressure of the square frame on their points beneath the handles ; but as soon as a load of hay has collected, the handles are slightly raised, throw- HORSE-RAKES. 155 ing this frame tackward off the points, and raising them enough for the forward row to catch the earth. The continued motion of the horse causes the teeth to rise and revolve, throwing the backward teeth fore- most over the winrow. In this way each set of teeth are alternately brought into operation. The cost of the revolving rake, well made, is ahout four times that of the simple horse-rake, hut on large meadows it possesses the superior advantages of expe- dition and ease in working. The Spring-tooth Horse-rake, Fig. 132, has been Fig. 132. Spring-tooth Horse-rake. much used, and has proved a valuable implement. The teeth are made of stiff, elastic wire, on the points of which the rake runs, and not on the flat sides, as in the two aheady described. They bend in passing an ob- struction, and spring back again to their place. This rake is unloaded by simply lifting the handles, which is easily done, the rake being light, and about one half the weight being sustained by the horse. It is pecu- 156 MECHANICS. liarly adapted to raking stubble, its upright teeth pre- venting the collection of portions of the soU with the straw. AH horse-rakes used on meadows are not only use- ful by the immediate saving of labor, but sometimes still more so by the expedition with which a crop of well-dried hay may he rescued from an approaching storm. MOWING AND REAPING MACHINES. The cutting part of all the best mowers and reapers ^'s- 133. made at the present day ^ p.<<^i^ll;;;sy frC^ consists of a serrated blade, as shown at a i ^ {\ f] (1 (1 ■ (^^"g-- 133), which pass- -=^— — ^^— =— ^= es through narrow slits in each of the fingers shown in b, forming, when thus united, the cutting apparatus, as exhibited in the an- nexed figure of Ketchuni's Mowing-machine {Fig. 134). When the machine is used, the motion of the Fig. 134. KetchurtVs Mowing-machine wheel on which the machine runs is multiplied by means of the cog-wheels, imparting quick vibrations MOWING AND REAPING MACHINES. 157 endwise to this blade, shearing off the grass smoothly as it advances through the meadow, like a large num- ber of scissors in exceedingly rapid motion. Fig. 135 Fig. 135. ^^^^^ Back view of Ketckum's Mower in operation. represents Ketchum's mower in operation as seen from behind, cutting an even swath five feet wide as fast as the horses advance. In the mowing-machine the cutting apparatus is narrow, causing the newly-cut grass to fall evenly be- hind it, covering the whole surface of the ground. The reaping-machine is similar in construction, with the addition of a platform for holding the grain as it falls, as shown in the figure of Hussetfs Reaper {Fig. 136). Pig. 136. Husseif'8 Reaping-machine. 158 MECHANICS. As the straw collects on this platform, it is raked off in successive hunches for binding by a man who rides on the machine for this purpose. Most reaping-machines are provided with a revolv- ing reel, which strikes backward against the standing grain, holds it there while the blade is cutting, and throws it backward on the platform. This reel is dis- tinctly shown in the representation [Fig. 137) oiMan- Fig. 137 Manny^s Mowing and Reaping Machine^ showing the reel distinctly. nifs Mowing and Reaping Machine, where the out- ting blade is placed midway between the forward and back wheels. Mowing machines require but one man for their management, who merely drives the horses that draw it. Reapers, as usually made, require another man be- sides the driver, to rake off the bunches of cut grain, which is severe labor. Various self-raking contriv- ances have been tried to obviate this labor, one of the most ingenious and best of which is Atkins^ Self-raker, represented by Fig. 138, and sometimes called the Automaton Raker. An ingenious piece of mechanism causes the rake to sweep the platform, and presses the fallen grain against another rake, when both of them, with the bundle of grain firmly inclosed, swing round behind, and then open wide, and drop-it on the ground ready for binding. It may be so regulated as to drop THE KNEE-JOINT POWER. Fig. 138. 159 Atkins^ Automaton Reaper in operation. the bunches more frequently where the crop is heavy, or more remotely where it is light. Fig. 139. SEOTIOIT IV. THE KNEE-JOINT POWER APPLIED TO MACHINES. The knee-joint or toggle-joint is usually regarded as a compound lever, and consists of two rods connected by a turning joint, as rep- resented in Fig. 139. The outer end of one of the levers is fixed to a solid beam, and the other connected with a movable block. When the joint a is forced in the direction indicated by the arrow, it pro- Knee- joint power, duccs a powerful prcssuro upoH the mov- able block, which increases as the lever approaches a straight line. This is easily understood by the rule of virtual velocities, for the force moves with a velocity many times greater than the power given to the block, and this relative difference increases as the joint is made straighter. This power is made use of in the lever printing-press, where the greatest force is given just as the pressure is completed. Another example occurs in the Lever 160 MECHANICS. Washing-machine (Fig. 140), which is worked by the alternating motion of the handle, A, pressing a swinging-hoard, perforated with holes, with great force Fig. 140. Lever Washing-maeJiine. against the clothes next to one side of the water- box. Like the printing-press, this machine exerts the greatest power just as the motion of the lever is completed, and at the time it is most needed. The same principle is exhibited in KendalVs Cheese-press {Fig. 141), where the lever and the wheel-and-axle are combined with the two knee-joints, one on each side of the press, drawing down a cro|s-beam upon the cheese with a greatly multiphed power. Emery^s Hay-press, for compressing hay into bales for distant conveyance, is another example {Fig. 142). The hay is thrown into a space in a strong box by opening the top doors, and when trodden down,' the doors are closed and secured by buttoning down the cross-bars. Horse- THE KNEE-JOINT POWER. Fig. 141. 161 Kendall's Cheese-press. Fig. 142. powe: Emery's Hay-fress. r is then applied to chains, which draw down the 162 MECHANICS. raised levers, operating on a knee-joint, and compress- ing the hay into a small and compact mass, the great- est force being given when most needed, at the termi- nation of the pressure. Side-doors are then thrown open, and the hay secured by bands and taken out. Two hundred and fifty pounds of hay may be thus re- duced to a space of sixteen cubic feet, or a little more than half a cubic yard, by a single horse ; and several tons may be pressed in a day. Dederick's improve- ment in this press consists in placing the levers at one end only, compressing the hay into the other end, and thus simplifying the machine. Double levers, press- ing equally against the upper and lower part of the shde or piston, keep it always upright and even, al- though the hay may be unequally compact. These double levers are connected and kept parallel by con- necting hinged bars. The power exerted by a rolling-mill, where bars of iron are flattened in their passage between two strong roUers, is precisely like that of the knee-joint. The only difference is, that the rollers, which may be con- sidered as a constant succession of levers coming into Fig. 143. play as they revolve, are both fixed, and consequently the bar has to yield between them {Figure 143). The greatest power is exerted just as the bar receives the last pressure from the rollers. The most Fnnc^.ie ^^^-nee-^oint in tke Powerful and rapidfy-working roibng-miii. straw-cuttcrs are those which draw the straw or hay between two rollers, one of THE KNEE-JOINT POWER. 163 which is furnished with knives set around it parallel with its axis, and cutting on the other, which is cover- ed with untanned ox-hide {Fig. 144). The only de- Fig. 144. Fig 146. feet in this naachine is its inability to cut shorter than one inch in length, which is not sufficient for corn- stalks and other coarse fodder. Dick''s Cheese-press {Fig. 145, on the following page) operates on a similar principle. Figure 146 shows the structure of its working part, the dotted lines indicating the position of the lever, which is in- serted into a roller or axle, and, by turning, drives the movable iron blocks asunder, and raises the cheese against the broad screw- head above, as shown in Fig. 145. In Fig. 146, the raised lever shows that the blocks are at first near to- gether, but are crowded asunder as the lever is press- ed downward. This cheese-press is made of cast-iron, 164 MECHANICS. Fig. 145. Dick^s cast-iron Cheese-press. and has great power ; to try it, weights were increased upon the lever, until the iron frame broke with a force equal to sixteen tons. ENDLESS-CHAIN POWERS. A convenient and compact machine for applying ani- mal power is by means of the endless chain, working in the position of an inclined plane, as represented in the annexed cut {Fig. 147), where the weight of a large dog is used for driving a churn-dasher. The platform on which the animal stands is formed of strips of light wood riveted to two India-rubber straps, and their constant downward motion turns the fly-wheel, to which a rod is attached for working the dasher. ENDLESS-CHAIN POWERS. Fig. 147. 165 Chum worked by dog-power. The same principle has been lately adopted with great success in the application of horse-power to driv- ing thrashing-machines, sawing wood, and to various other purposes. Instead of India-ruhher straps, strong cast-iron chains are used, which are made to run smoothly and with very little friction over a succession of small iron wheels, which support the weight of the horses on the moving platform (Fig: 148, on the fol- lowing page). The power of these machines, and the amount of friction in running them, may be easily ascertained by the rule, already given in a former part of this work, for determining the power of the inclined plane ; for the only difference between the endless-chain and a common inclined plane is, that in one the plane is fixed, and the body moves up its surface, and in the other the plane itself moves downward, and the weight or animal upon it remains stationary. The same prin- 166 MECHANICS. ciple applies in both cases. First, to ascertain the friction, let the platform be placed on ^ a level, with the horse s upon it ; then gradual- ? Iv raise the end until I theweight of the horse I wUl just give it mo- °„ tion. This wiU show § the precise amount of i;- the friction ; for if the I. end be elevated one I twentieth of its length, s then the friction is one i twentieth the weight I of the horse and plat- form. Secondly, to deter- mine the power, when the end is still further raised, measure the difference between the height thus given and the length of the platform. If, for instance, the height of the inclination is one eighth of its length, and the horse is found to weigh eight hundred pounds, then the power is one hundred pounds, or one eighth the weight of the horse. This rule will not, however, apply, when the draught of the horse is added to its weight ; for it usually hap- pens that the weight alone is not sufficient, without APPLICATION OF LABOR. 167 placing the platform in too steep a position for a horse to work comfortahly. He is therefore attached to a whipple-tree placed on the frame of the machine, so that in drawing he pushes the platform backward with his feet. In this case, the power can be only ascer- tained by the use of the dynamometer, already de- scribed. SECTION V. APPLICATION OP LABOR. Most of the moving powers applied by the farmer to accomplish labor are the exertions of animal strength. A principal object of the preceding pages is to point out how this sti-ength can be applied in the most econom- ical manner, and to aid in the substitution of cheap horse-power for more costly human labor. It wiU doubtless contribute to the end to exhibit the relative efficiency of each, as well as the results of strength differently applied. The amount of work which any machiae is capable of performing is denoted by comparing this amount with the power of a single horse ; hence the common expressions of twenty, or fifty, or a hundred horse- power engines. The strength of different horses varies greatly, but the expression, as commonly understood, indicates a force equivalent to raising or pressing with a force equal to 150 pounds 20 miles a day, at the rate of two and a half mUes an hour. This is the same as 33,000 pounds raised one foot in one minute. The re- sults of numerous experiments in different places give the actual power of the average of horses at somewhat 168 MECHANICS. less than this ; and there is no doubt that, for most of the farm-horses of this comitry, the result would be considerably less. The power of a strong English draught-horse has been ascertained to be about 143 pounds for 22 miles a day, at 2 J miles an hour. Many American horses are scarcely more than half as strong. The strength of a man, working at the best advantage, is estimated at one fifth that of a horse. As the speed of ahorse increases, his strength of draught diminishes very rapidly, till at last he can only move his own weight. This is owing to -^hree reasons : first, the load moves over a greater space in a given tune, and if, for instance, the speed be doubled, half the load only can be carried with the same quantity of power, according to the law of virtual velocities ; secondly, the horse has to carry the full weight of his body, whatever his speed may be, and the force expended for this purpose alone must, therefore, be doubled as the speed is doubled ; thirdly, a very quick and unaccustomed mo- tion of the muscles is in itself more fatiguing than the ordinary or natural velocity. The following table shows the amount of labor a horse of average strength is capable of performing in a day at different degrees of speed, on canals, rail-roads, and on turnpikes. The force of draught is estimated at about 83 pounds. This is considerably less than the horse-power used in estimating the force of machin- ery, but it is as much as an ordinary horse can exert without being improperly fatigued with continued ser- vice: APPLICATION OF LABOR. 169 Velocity per hour. Duration of the day's work. Hours. m Work accomplished/or one day, one mile. in tons, dravm Miles. 2i- On a canal. 520 On a rail-road. 115 On a turnpike. 14 3 8 243 92 12 3i 4 5A 153 102 82 72 10 9 5 h\ 52 57 7.2 6 3 30 48 6 7 H 19 4J 5.1 8 n 12.8 36 4.5 9 10 4 9 6.6 32 28,8 4 3.6 From the preceding table it will be seen that a horse, at a moderate walk, will do more than four times as much work on a canal as on a rail-road ; but the re- sistance of the water increases as the square of the ve- locity, and therefore when the speed reaches five miles an hour, the rail-road has the advantage of the canal. On the rail-road and turnpike the resistance is about the same, whether the speed be great or little, the chief loss with fast driving resulting from the increased difficulty with which the horse carries forward his own body, which weighs from 800 to 1200 pounds. The table also shows that when it becomes necessary to drive rapidly with a load, it should be continued but for a very short space of time ; for a horse becomes as much fatigued in an hour, when drawing hard at ten miles an hour, as in twelve hours at two and a half miles an hour ; because, when a boat is driven through the water, to double its velocity not only requires that twice the amount of water should be moved or dis- placed in a given time, but it must be moved with twice the velocity, thus requiring a four-fold force. The muscular formation of a horse is such that he H 170 MECHANICS. will exert a considerably greater force when working horizontally than up a steep inclined plane. On a level, a horse is as strong as five men, but up a steep hill he is less strong than three ; for three men, carry- ing each 100 pounds, will ascend faster than a horse with 300 pounds. Hence the obvious waste of power in placing horses on steeply-tacLined tread-wheels or aprons. The better mode is to allow them to exert their force more nearly horizontally, by being attached to a fixed portion of the machine. For the same rea- son, the common opinion is erroneous that a horse can draw with less fatigue on an undulating than on a level road, by the alternations of ascent and descent calling different muscles into play, and reheving each in turn ; for the same muscles are alike exerted on a level and on an ascent, only in the latter case the fatigue is much greater than the counterbalancing relief Any person may convince himself of the truth on this subject by first using a loaded wheel-barrow or hand-cart for one day on a level, and for the next up and down a hill ; bearing in mind, at the same time, that the human body is better fitted for climbing and descending than that of a horse. A draught-horse can draw 1600 pounds 23 miles in a day on a good common road, the weight of the car- riage included. On the best plank-road he will draw more than twice as much. A man of ordinary strength exerts a force of 30 poiinds for 10 hours a day, with a velocity of 2 J feet per second. He travels, without a load, on level ground, during 8J hours a day, at the rate of 3.7 miles an hour, or 31i mUes a day. He can carry 111 pounds 11 APPLICATION OP LABOR. 171 miles a day. He can carry in a wheel-lDarrow 150 pounds 10 miles a day. Well-constructed machines for saving human lahor by means of horse-labor, when encumbered with httle friction, will be found to do about five times as much work for each horse as where the same work is per- formed by an equal number of men. For example : an active man will saw twice each stick of a cord of wood in a day. Six horses, with a circular saw, driven by means of a good horse-power, will saw five times six, or thirty cords, working the same length of time. In this case the loss by friction is about equal to the ad- ditional force required for attendance on the machine. Again : a man wiR cut with a cradle two and a half acres of wheat in a day. A two-horse reaper should therefore out, at the same rate, ten times two and a half, Or twenty -five acres. This has not yet been ac- complished. We may hence infer that the machinery for reaping has been less perfected than for sawing wood. It should, however, be remembered, that great force is exerted, and for many hours in a day, in cut- ting wheat with a cradle, and therefore a little less than twenty-five acres a day may be regarded as the maximum attainment of good reaping-machines, when they shall become perfected. Applying the same mode of estimate, a horse-culti- vator will do the work of five men with hoes, and a two-horse plow the work of ten men with spades. A horse-rake accomplishes more than five men, because human force is not strongly exerted with the hand-rake. In using different tools, the degree of force or press- ure applied to them varies greatly with the mode in 172 MECHANICS. which the muscles are exerted. The following table gives the results of experiments with human strength, variously applied, for. a short period : Force of the hands Force of the tool on the tool. on the object. With a drawing-kpife 100 lbs. 100 lbs. " a large auger, both hands 100 " about 800 " a screw-driver, one hand 84 " 250 " a bench-vice handle 72 " about 1000 " a windlass, with one hand 60 " 180 to 700 " a hand-saw 36 " 36 " a brace-bit, revolving 16 " 150 to 700 Twisting with thumb and fingers, but- ton-screw, or small screw-driver .... 14 " 14 to 70 " The force given in the last column will, of course, vary with the degree of leverage applied ; for example, the arms of an auger, when of a given length, act with a greater increase of power with a small size than with a large one. This degree of power may he calcu- lated for an auger of any size, by considering the arms as a lever, the centre screw the fulcrum, and the cut- ting-blade as the weight to be moved. The same mode of estimate will apply to the vice-handle, the windlass, and the brace-bit. Every one is aware that a heavy weight, as a paU of water, is easily lifted when the arm is extended downward, but with extreme difficulty when thrown out horizontally. In the latter case, the pail acts with a powerful leverage on the elbow and shoulder-joint. For this reason, all kinds of hand-labor, with the arms pulling toward or pushing directly from the shoulders, are most easily performed, while a motion sidewise or at right angles to the arm is far less effective. Hence great strength is applied in rowing a boat or in tising MODELS OF MACHINES. 173 a drawing-knife, and but little strength in turning a brace-bit or working a dasher-churn. Hence, too, the reason that, in turning a grindstone, the pulling and thrusting part of the motion is more powerful than that through the other parts of the revolution. This also explains why two men, working at right angles to each other on a windlass, can raise seventy pounds more easily than one man can raise thirty pounds alone. This principle should be well understood in the construction or selection of all kinds of machines for hand labor. SECTIOH, VL MODELS OP MACHINES. Serious errors might often be avoided, and some- times gross impositions prevented, by understanding the difference between the working of a mere model, on a miniature scale, and the working of the full-sized machine. It is a common and mistaken opinion that a well-constructed model presents a perfect representa- tion of the strength and mode of operation of the ma- chine itself. When we enlarge the size of any thing, the strength of each part is increased according to the square of the diameter of that part ; that is, if the diameter is twice as great, then the strength will be four times as great ; if the diameter is increased three times, then the strength will be nine times, and so on. But the weight increases at a still greater rate than the strength, or according to the cube of the diameter. Thus, if the diameter be doubled (the shape being similar), the 174 MECHAMICS. weight will be eight times greater ; if it be tripled, the weight wiU be twenty-seven times greater. Hence, the larger any part or machine is made, the less able it becomes to support the still greater increasing weight. If a model is made one tenth the real si^e intended, then its different parts, when enlarged to full size, become one hmidred times stronger, but they are a thousand times heavier, and so are all the weights or parts it has to sustain. All its parts would move ten times faster, which, added to their thousand-fold weight, would increase their inertia and momentum ten thousand times greater. For this reason, a model wiU often work beautifully when made on a small scale ; but when enlarged, the parts become so much heavier, and their momentum so vastly greater, from the longer sweep of motion, as to fail entirely of suc- cess, or to become soon racked to pieces. This same principle is illustrated in every part of the works of creation. The large species of spiders spin thicker webs, in comparison with their own diam- eter, than those spun by the smaller ones. Enlarge a gnat until its whole weight be equal to that of the eagle, and, great as that enlargement would be, its wing will scarcely have attained the thickness of writ- ing-paper, and, instead of supporting the weight of the animal, would bend down from its own weight. The larger spiders rarely have legs so slender in form as the smaller ones ; the form of the Shetland pony is quite different from that of the large cart-horse; and the cart-horse has a slenderer form than the elephant. The common flea will leap two hundred times the length of its own body, and the remark has been some- MODELS OF MACHINES. 175 times made that a man equally agile, with his present size, would vault over the highest city-steeple, or across a river as wide as the Hudson at Albany. Now,- if the flea were increased in size to that of a man, it would become a hundred thousand tirnes stronger, but thirty million times heavier ; that is, its weight would be- come three hundred times greater than its correspond- ing strength. Hence we may infer that the enlarged flea would be no more agile than a man ; or that, if a man were proportionately reduced to the size of a flea, he could leap to as great a distance. All this serves to illustrate in a striking manner the distinction between models and machines. PART II. HYDRODYNAMICS.* HYDROSTATicst treats of the weight and pressure of liquids when not in motion ; Hydraulics,1: of hquids in motion, as, conducting water through pipes, raising it by pumps, &c. ; and Hydrodynamics includes both, by treating of the forces of the Hquids, whether at rest or in motion. CHAPTER I. HYDROSTATICS. SECTION I. ITPWARD PRESSURE. A REMARKABLE property of liquids is their pressure in all directions. If we place a solid body, as a stone, in a vessel, its weight will only press upon the bottom ; but if we pour in water, the water will not only press upon the bottom, but against the sides. For, bore a hole into the side, and the side pressure wiU drive out the water in a stream ; or, bore small holes into the sides and bottom of a tight wooden box, stopping them * From two Greek words, hudor, water, and dunamis, power, t From two Greek words, hudor, water, and states, standing, or at rest. t From two Greek words, hudor, water, and aulos, a pipe. UPWARD PRESSURE. 177 with plugs ; then press this box, empty, hottom down- ward, into water, allowing none to run in at the top. Now draw one of the side plugs, and the water will be immediately driven into the box by the pressure out- side. If a bottom plug be drawn, the water will im- mediately spout up into the box, showing the pressure upward against the bottom. Hence the pressure in all directions, upward, sideways, and downward, js proved. The upward pressure of liquids may be shown by pouring into one end of a tube, bent in the shape of the letter U, enough water to partly fiU it; the upward pressure wOl drive it up the other side till the two sides are level. On this principle depends the art of conveying water in pipes under ground, across valleys. The water will rise as high on the opposite side the valley as the spring which supplies it. The ancient Romans, who were unacquainted with the manufacture of strong cast-iron pipes, conveyed water on lofty aqueducts of costly ma- sonry, buUt level across the valleys. Even at the pres- ent day, it has been deemed safest to buUd level aque- ducts for conveying great bodies of water, as in very large pipes the pressure would be enormous, and might result in violent explosions. If the valleys are deep, the pipes must be correspond- ingly strong, because, the higher the head of water, the greater is the pressure. For the same reason, dams and large cisterns should be strongest at bottom. Res- ervoirs made in the form of large tubs require the lower hoops to be many times stronger or more numer- ous than the upper. H2 178 HYDRODYNAMICS. MEASUREMENT OF PRESSURE AT DIFFERENT HEIGHTS. The amount of pressure which any given height of water exerts upon a surface helow may be understood by the followiag simple calculation : If there be a tube one inch square (with a closed end), half a pound of water poured into it will fill it to a height of fourteen inches;* one pound will fill it twenty-eight inches ; two pounds, fifty-sis inches ; ten Fig. 149. pounds, twenty -three feet; twenty ■2His. 56 3JL pounds, forty-six feet, and so on. Now, as the side pressure is the same as the pressure downward for the same head of water, the sarhe column will, of course, exert an equal press- ure on a square inch of the side of the tube. Or, if the tube be bent, as shown in the annexed figure {Fig. 149), the pressure upward on the end of the tube, at a, will be the same for the various heights. Now, as the pressuTe of a column fifty feet high is about twenty-two pounds on a square inch, the pressure on the four sides is equal to eighty- eight pounds for one inch in length. Hence the reason that considerable strength is required in tubes which have much head of water, to prevent their being torn open by its force. * This is nearly correct, for a cubic foot (or 1728 cubic inches) of water weighs 62 lbs. Consequently, one pound will be 27.9 cubic inches, and will fill the tube nearly 28 inches high. ~ l^ns.A2.ta.. lit 28 ill. ■V^lb-liin. SPRINGS AND ARTESIAN WELLS. 179 DETERMINING THE STRENGTH OF PIPES. The question may now arise, and it is a very import- ant one, How thick must be a lead tube of this size to prevent danger of bursting with a head of fifty feet, or of any other height ? To answer it, let us turn to the table of the Strength of Materials in a former part of this work, where we find that a bar of cast lead one fourth of an inch square will bear a weight of fifty-five pounds. If the tube be only one sixteenth of an inch thick, one inch of one of its sides will possess an equal strength, that is, will bear fifty-five pounds only, and the tube would consequently burst with fifty feet head. If one tenth of an inch thick, the tube would just bear the pressure, and, to be safe, should be about twice as thick, or one fifth of an inch. Half this thickness would be sufficient for twenty-five feet of water, which would require to be doubled for one hundred feet. A round tube, one inch in diameter, having less surface to its sides, would be about one third stronger. A tube twice the diameter would need twice the thickness ; or if less in diameter, a proportionate decrease in thick- ness might take place. If, instead of cast lead, milled lead were used, the tube would be nearly four times as strong, according to the table of the strength of ma- terials already referred to. SPRINGS AND ARTESIAN WELLS Result from the upward pressure of water. Rocks are usually arranged in inclined layers {Fig. 150, p. 180), and when rain falls upon the surface, as at c d, it sinks down in the more porous parts between these layers, 180 HYDRODYNAMICS. Fig. 150. to c. If the layers happen to be broken in any place below, the water finds its way up through the crevices by the pressure of the head above, and forms springs. If there are no openings through the rocks, deep borings are sometimes made artificially, through which the wa- ter is driven up to the surface, as at a, forming what are termed Artesian Wells. The head of water which supplies them may be many miles distant, the place of discharge being on a lower level. It has sometimes been found necessary to bore more than a thousand feet downward before obtaining water which wiU flow out fi:eely at the surface of the earth. Fig. 151. SECTION II. DETEEMINING THE PE-ESSUEE ON GnTEN SUKFACES. The pressure of liquids upon any given surface is always exactly in proportion to the height, no matter what the shape of the vessel may be. If, for instance, the ves- sel a (Fig. 151), be one inch in diameter, and the vessel b be three inches in diameter, DETERMINING THE PRESSUEB ON GIVEN SURFACES. 181 the water being equally high in both, the pressure on the whole bottom of b will be nine times as great as on the bottom of a ; or any one inch of the bottom of b will receive as great a pressure as the bottom of a. Again, if the vessel c, broad at the top, be narrowed to only an inch in diameter at bottom, the pressure upon that inch will still be the same, most of the weight of its contents resting against the sides, d d. If the vessel, A (Ftg. 152), be filled with water to a ^.^ j^^ heightof fourteen inches, the press- ure will be half a pound on every square inch of the bottom, or upon every square inch of the sides four- teen inches below the surface. If the tube, C, be an inch square, the water will be driven into it with a force of half a pound, and wiU press with that force against the one-inch surface of the stop-cock, C. If the tube, B, be now filled to an equal height, the same force will be exert- ed against the other side. To prove this, let the stop- cock be opened, when the two columns of water will remain at an exact level. If enough water be now poured into the tube, B, to fill it to the top, it will immediately settle down on a level with the water in A, raising the whole surface in the latter. This result has seemed very strange to many, who can not conceive how a small column of water can be made to balance a' large one, and it has been therefore termed the Hydrostatic Paradox. But the difficulty entirely vanishes, and ceases to appear a paradox, when we remember that the water in the 182 HYDRODYNAMICS. larger vessel rises as much more slowly than it de- scends in the smaller, as the large one exceeds the smaller ; thus acting on the principle of virtual veloci- ties in precisely the same manner that a heavy weight on the short end of a lever is upheld by a small weight on the long end. The great mass of water is support- ed directly by the bottom of A, in the same way that nearly all the weight on the lever is supported by the fulcrum. A man who was seeking a solution to the absurd mechanical problem of perpetual motion, and Fig 153. who supposed that the large mass in A Just perceptible. 5 J25 \ ^'Stt breeze. 6 .180 i 7 'iao \ Gentle, pleasant wind. 222 PNEUMATICS. Miles-an Pressure in lbs. on t»„.,™;.,*;«« hour. a square foot. Description. > Pleasant, brisk wind. 20 2.000 J 10 .500 15 1.125 I ) 25 3.125? Verybnsk. 35 025} Strong, high wind. I5 llTi\ Very high. 50 12.500 Storm or tempest. 60 18.000 Great storm. 80 32.000 Hurricane. 100 50.000 Tornado, tearing up trees, and sweeping off buildings. These forces may be observed at a time when the au' is still, by a forward motion equal to that of the wind. Thus walking moderately gives the faint breeze against the face ; riding in a wagon at six miles an hour causes the sensation of a pleasant wind ; the deck of a steam- boat at fifteen miles produces a brisk blow ; while an open rail-car at forty miles an hour occasions a sweep of the air nearly resembling a tempest. ^ The preceding table will enable any one to calculate with considerable accuracy the amount of draught which a horse must constantly overcome in traveling with a covered carriage against the wind, adding, of course, the speed of the horse to that of the wind. For example, suppose a horse with a covered carriage is driven against what we term " a very brisk wind," blowing 24 miles an hour, and pressing 3 lbs. on the square foot. The carriage top offers a resisting surface four feet square, or with sixteen square feet. Three times sixteen, or 48 lbs., are consequently required to be overcome with every onward step of the horse. WIND-MILLS. 223 Now we have already seen, when treating of " appH- cation of labor," that a horse traveling three miles an hour for eight hours, will overcome only 83 lbs. with ordinary working, which is not double the resistance of the wmd. Hence we perceive that more than half the horse's strength is lost by driving agaiost such a current. At six miles an hour, all his strength, with- out over-driving, would be expended in overcoming the force of the wind, and the power required for mov- ing the carriage would be so much excessive labor. For simphfying the operation, the increased motion of the wind occasioned by driving against it has not been taken into account. Even with a small pressure, the loss in power is con- siderable for an entire day. "When, for example, the air is perfectly still, traveling six mUes an hour will cause a constant resistance of 3 lbs. on the carriage, or one fourteenth of the power exerted for a fuU day's work. The same speed against a " gentle wind" of six miles an hour, added, would increase the resistance four- fold, or equal to 12 lbs. ; more than one fourth of the horse's strength at six miles an hour through the day. WIND-MILLS. The power possessed by the sails of a wind-mill may be nearly ascertained in the same way, the area of the sails being known, and first deducting their av- erage velocity. The force of wind may be usefully applied by al- most every farmer, as it is a universal agent, possess- ing in this respect great advantages over water-power, of which very few farms enjoy the privilege. 224 PNEUMATICS. Wind may be applied to various purposes, suoli as sawing wood by the aid of a circular saw, turn- ing grindstones, and particularly in pumping water. One of the best contrivances for pump- ing is represented by Fig. 183, where A is the circular wind-mill, with a number of sails set obliquely to the di- rection of the wind, and alv«§ys kept facing it bymeansofthevane, B. The crank of the wind- mill, during its revo- lutions, works the pump-rod, I, and raises the water from the well beneath. In whatever direction the wind may blow, the pump will continue working. The pump-rod, to work steadily, must be immediately un- der the iron rod on which the vane turns. If the di- ameter of the wind-mill is four feet, it will set the pump in motion even with a light breeze, and with a brisk wind will perform the labor of a man. Such a machine will pump the water needed by a large herd of cattle, and it may be placed on the top of a barn, with a covering, to which may be given the architec- tural effect of a tower or cupola, as shown in Fig. 184, opposite. A more compact machine, but of more complex con- struction, is shown in Fig. 185, opposite, where the up- VVifnt-nnllfor pumping water on farms : A, wind-'miU ; B, vane ; I, pump-rod. WIND-MILLS. Fig. 184. TtT B X-^- Bam surmounted with wind-m ill /or pumping water j cutting straw, i^c. 225 Fig. 18.5. K2 226 PNEUMATICS. per circle moves around with the wheel and vane on the fixed lower circle, to which it is strongly secured so as to admit of turning freely. In other respects it is similar to the preceding. In all wind-mills, it is important that the sails should have the right degree of inchnation to the direction of the wind. If they were to remain motionless, the angle Would be different from that in practice. They should more nearly /ace the wind ; and as the ends of the sails sweep round through a greater distance and faster, they should present a flatter surface than the parts nearer the centre. The sails should, therefore, have a twist given them, so that the parts nearest the centre may form an angle of about 68 degrees with the wind, the middle about 72 degrees, and the tips about 83 degrees. In order to produce the greatest effect, it is necessa- ry to give the sails a proper velocity as compared with the velocity of the wind. If they were entirely un- loaded, the extremities would move faster than the wind, in consequence of its action on the other parts. The most useful effect is produced when the ends move about as fast as the wind, or about two thirds the ve- locity of the average surface. The most useful wind is one that moves at the rate of eight to twenty miles per hour, or with an average pressure of about one pound on a square foot. In large wind-mills, the sails must be lessened when the wind is stronger than this, to prevent the arms from being broken ; and if much stronger, it is unsafe to spread any, or to run them. CHIMNEY CURRKNTS, CAUSES OF WIND. 227 The motion of air in producing wind is explained by the action of heat, although there are many irregular currents whose cause is not u-e.ll uuderstood. The simplest illustration of the effect of heat in causing cur- rents is furnished by the land and sea breezes in warm latitudes. The rays of the sun during the day heat the surface of the land, and the air in contact with it also becoming heated, and thus rendered lighter, flows up- ward ; the air from the sea rushes in to fill the vacancy and causes the sea-breeze. During the night, the ra- diation of heat firom the land into the clear sky above •cools the surface to a lower temperature than that of the sea ; consequently the air in contact with the sea becomes heated the most, and rising, causes the wind from the land to flow in and supply the place. Trade- winds are caused in a similar way, but on a much larger scale, by the greater heat of the earth at the equator, which produces currents from colder latitudes. These currents assume a westerly tendency, in conse- quence of the -velocity of the earth being the greatest at the equator, and which, outstripping the momentum which the winds have acquired in other latitudes, tends to throw them behind, or in a westerly direction. SECTION II. CHIMNEY CURRENTS. Chimney Currents are produced by the heat of the fire rarefying the air, which rises and carries the smoke with it. The taller the chimney is, the longer will be 228: PNEUMATICS. the column of rarefied air tending upward, and, as a consequence, the stronger will be the draught. In kin- dhng a fire in a cold chimney, there is very httle cur- rent tUl this column becomes heated. The upward motion of heated currents is governed by laws similar to the downward motion of water in tubes, where the velocity is increased with the height of the head. But as air is more than eight hundred times hghter than water, slight causes will affect its currents, which would have no sensible influence on the motion of Uquids. For instance, a strong wind striking the top of a chim- ney may send the smoke downward into the room ; and a current can not be induced through a horizontal pipe without connecting with it an upright pipe of con- siderable height. Fig. 186. CONSTRUCTION OF CHIMNEYS. In constructing cliimneys to produce a strong draught, the throat immediately above the fire, which should have a breadth equal to that of the fire-place, should be contracted to a width of about four inches, so that the column of rising air above may draw the air up through the throat with increased velocity, as shown in Fig. 186. This arrangement also allows the fire to be built so as to throw the heat more fully out into the room. By leaving the shoulder at b square or flat, it will tend to arrest any reversed or downward current in a bet- ter manner than if built sloping, as shown by the dotted line at a, which would act CHIMNEY-CAPS. 229 /'^ a like a funnel, and throw the sn;ioke into the room. Fig. 187. The throat should be about as high as the ex- treme tip of the flame ; if much higher, the chimney will not draw so well, and if lower, too much of the heat will be lost. Fig. 187 shows a fire-place without a contracted throat, the current of which is comparatively feeble. Many chimneys draw badly by being made too large for the fire to heat sufficiently the column of air they contain. CHIMNEY-CAPS. When wind sweeps over the roof of a high part of the building, or over a hill, it often cidrmey. strikcs the top of chimneys below, and drives the smoke downward. This may be often prevented by placing a cap over the chim- ney, like that represented by Fig. 188, which is supported at its corners, the smoke passing out at the four sides just under the eaves of this cap. But it some- times happens that there is a confusion of currents and eddies at the top of the chim- ney, over which this cap has no influence. In this case, the cap represented by Fig. 189 furnishes a perfect remedy, and is, in- deed, perfect in its operation under any cir- cumstances whatever, for the chimney sur- mounted by it will always draw when there is wind from any quarter, with or without any fire. It has effected a perfect cure in some chimneys which before were exceedingly troublesome, and were Fig. 188. Fig. 189. 230 PNEUMATICS. Fig. 190. regarded as incurable. Fig. 190 is intended to show the mode of its operation, the wind, as shown by the arrows, being deflected for a considerable distance on the lee side, so as to form a vacancy at a, which the wind from the other end and from the chimney both rush in to supply. Being fixed on with- out turning in the chimney, it is both simpler and less noisy than any caps furnished with a vane. Emerson's Chimney-cap, lately invented, is differ- Fig. 191. ent in construction, but quite similar in principle to the preceding. It is shown by Fig. 191. A sheet-iron pipe is set in ^ the top of the chimney, furnished with the conical rim, and a plate or fender on the top which excludes the rain. Be- U ■ I tween the plate and rim is a space I quite simi- lar in form or section to that represented by Fig. 190. In exposed situations, chimneys are found to draw more uniformly by contracting the top about a third less than the rest of the flue. The current at the moment of escape is swifter than below, and less acted upon by any downward check from the i CHIMNEY-CAPS. 231 Fig. 193. wind, at the same time that the surface is smaller on which the wind can strDie the current, as shown in Fig. 192. A chim- ney of this character may be very easily made by contracting the tiers of brick, thus giving to it an ornamental appearance, as seen in Fig. 193.* * Where different fires communicate with the same chimney, sep- arate flues should be built for each fire, and kept separate in the same chimney-stack, carried up independently of each other. But even with this precaution, smoky rooms will not be avoided, unless the ter- mination of the chimney is of the right form, of which the following illustration is given in Allen's Rural Architecture : " Fifteen years ago we purchased and removed into a most substan- tial and well-built stone house, the chimneys of which were construct- ed with open fireplaces, and the flues carried up separately to the top, where they all met upoq the same level surface, as chimneys in past times usually were built, thus. Every fireplace ill the house (and some of them had stoves in) smoked intolfeably ; so much so, that when the wind was in some quarters, the fires had to be put out in every room but the kitchen, which, as good luck would have it, smoked less — although it did smoke there— than the others. Afl^er balancing the matter in our own mind some time whether we would pull down and rebuild the chimneys altogether, or attempt an alteration — as we had given but lit- tle thought to the subject of chimney draft, and to try an experiment was the cheapest — we set to work a bricklayer, who, under our direc- tion, simply built over each discharge of the several flues a separate Fig. 195. *°P °^ fifteen inches high, in this wise : the remedy was perfect. We have had no smoke in the house since, blow the wind as it may, on any and on all oc- casions. The chimneys can't smoke ; and the whole expense for four chimneys, with their twelve flues, was not twenty dollars ! The remedy was in giving each outlet a distinct current of air all around, and on every side of it." 232 PNEUMATICS. VENTILATION. Impure air may be breathed for a sbort time "with- out any serious detriment, but to live in it and respire it for years can not fail to produce permanent injury to the health. Duriag the heat of summer, open doors and windows will usually furnish plenty of fresh air, as long as this season lasts, which in the Northern States is not one half of the year. During the rest of the time rooms are heated with close stoves, and unless special care is taken to secure fresh air, pale or sickly inmates wUl be the most likely results. Even with a common open fire-place, which causes more circulation of the air in a room than stoves, the ventilation is very imperfect. The following figure {Fig. 196) represents the fresh air as passing in from Fig. 196. A badly-ventilated Room. an open window opposite the fire, producing a direct current from the window to the chimney, and leaving all the upper portion of the room filled with bad air, unaffected by the change. The cold air can not rise, nor the hot air descend. This difficulty may be easily VENTILATION. 233 removed by placing a register (which may be closed or opened at pleasure) at a, in the upper corner, so that the confined air may escape into the chimney. With- out this provision, it is nearly impossible to preserve the air in proper condition for breathing, for the upper part, being warmest and Ughtest, remains unchanged at the top. In rooms heated by stoves, registers for es- cape of the foul air are still more important, where the thermometer frequently indicates twenty degrees differ- ence in the heat above and at the floor, the lower stra- tum of air resting like a cold lake about the feet, while the head is heated unduly. When the draught of the chimney-fire is not strong, the smoke may, however, escape through the ventilat- ing register into the room. To avoid this difficulty, it is best to provide separate air-flues in the walls when the house is built, for effecting perfect ventilation. In rooms strongly heated by fires, the fresh air should be admitted near the ceiling, producing descending cur- rents, and effecting a complete circulation in the air of the room. But in sleeping apartments and in closets, not heated artificially, and where the descending cur- rents wiU not take place, the fresh air should be admit- ted through a register or small rolhng blind near the floor, and discharged near the ceiling into an air-flue. Fig- 197. The excessive warmth of garrets in mid-summer may be avoided by placing a ventilator at the highest part, and admit- ting air at windows or openings near the eaves {Fig. 197), thus Mode of Ventilating Garrets. Sweeping aU the hot air out by 234 PNEUMATICS. the current produced ; or, the oppressive heat of half- story bedrooms may be similarly avoided, by creating a current of air between the roof and the plastering {Fig. 198). Two modes may be adopted, as repre- sented on each side of the figure. Fig. 198. Mode of Ventilating half-story Bes^ rooms. PART IV. HEAT. CHAPTER I. CONDUCTION OF HEAT. SECTION I. CONDTJCTING POWER OF BODIES. "When any substance or body has become heated, it loses its heat in two different ways, by conduction and by radiation. When conducted, heat passes off slow- ly or gradually through bodies, as when a pin is held by the hand in a candle, the heat advancing from one end to the other till it burns the fingers ; or, when an iron poker is thrust into the fire, the heat gradually passes through it till the whole becomes hot. Iron and brass are, therefore, said to be good conductors of heat. The end of a pipe-stem may, however, be heated to redness, and a wooden rod may be set on fire, with- out even warming the other extremity, because the heat is very slowly conducted through them. Wood and burned clay are, therefore, poor conductors. The comparative conducting power of different sub- stances may be shown by placing short rods of each with one of their ends in a vessel of hot sand, the oth- ers to be tipped with wax. The different periods of time required to melt the wax indicate the relative 236 HEAT. conducting powers. It will speedily melt on the cop- per rod ; soon after, on the rod of iron ; glass will re- quire longer time ; stone or eathenware stiU longer ; while on a rod of wood it will scarcely melt at all. These rods should be laid horizontally, that the hot air rising from the sand may not affect the wax. The conducting powers may be judged of likewise, with considerable accuracy in cold weather, by merely plac- ing the hand upon the different substances. The best conductors will feel coldest, because they withdraw the heat most rapidly from the hand. Iron will feel colder than stone ; stone colder than brick ; wood stiU less so ; and feathers and down least of all, although the real temperature of aU may be precisely the same. UTILITY OF TlilS PRINCIPLE. A knowledge of this property is often very useful. For instance, it is found that hard and compact kinds of wood, as beach, maple, and ebony, conduct heat nearly twice as rapidly as light and porous sorts lilie pine and basswood. Hence doors and partitions made of light wood make a warmer house than those that are more heavy and compact. Pine or basswood would, in this respect, be better than oak or ash. Porous substances of all kinds are the poorest con- ductors ; saw-dust, for example, being much less so than the wood that produced it. For this reason, saw- dust has been used as a coating around the boilers of locomotives to keep in the heat, and for the walls of ice-houses to exclude it. Sand, filled in between the double walls of a dwelling, renders it much warmer in winter and cooler in summer than if sandstone were CONDUCTING POWER OF LIQUIDS. 237 made to fill the same space. Ashes, being more po- rous, are found to he still better. Tan, which is simi- lar to saw-dust, is well adapted to filling in the walls of stables and poultry-houses, where more than usual warmth in winter is required. Confined air is a very poor conductor of heat ; hence the advantage of double walls and double windows, provided there are no crev- ices for the escape of the confined air. This principle has been lately applied in the manufacture of hollow brick for building the walls of dwellings. The fight and porous nature of snow renders it emi- nently serviceable as a clothing to the earth in the depth of winter, preventing the escape of the heat firom below, and protecting the roots of plants from injury or destruction. Hence the very severity of the cold of the Northern regions, by producing an abundance of those beautiful feathery crystals which form snow, be- comes the means of protecting from its own effects the tender herbage buried beneath this ample shelter. CONDUCTING POWER OF LIQUIDS. Liquids are found to conduct heat very slowly, and they were for a long time considered perfect non-con- ductors. Some interesting experiments have been per- Fig. 199. formed in illustration of this property. A large glass jar may be filled with water (Fig. 199), in wliich may be fixed an air thermom- eter, which is always very quickly sensitive to small quantities of heat. A shallow cup of ether, floating just above the bulb, may be set on fire, and will continue to burn for some time before any effect can be seen upon 238 HEAT. the thermometer. The upper surface of a vessel of wa- ter has heen made to boil a long time, with a piece of umnelted ice at the bottom. Liquids are found, howev- er, to possess a conducting power in a very slight degree. "When a vessel of water is heated in the ordinary way over a fire, the heat is carried through it merely by the motion of its particles. The lower portion be- T.- „„„ comes warm and expands ; it immediate- Fig. 200. _ ^ ' ly rises to the surface, and colder portions sink down and take its place, to ascend in their turn. In this way, a constant cir- culation is kept up among the particles. These rising and descending currents are shown by the arrows in Fig. 200. This result may be easily shown by filling a flask with water into which a quantity of saw- dust from some green hard wood has been thrown, which is about as heavy as water. It will traverse the vessel in a manner precisely like that shown in the figure. These results show the importance of applying heat directly to the bottom of all vessels in which water is intended to be heated. A considerable loss of heat oft- en occurs when the flame is made to strike against the sides only of badly-arranged boilers. SECTION II. EXPANSION BY HEAT. An important effect of heat is the expansion of bod- ies. Among many ways to show it, an iron rod may be so fitted that it will just enter a hole made for the EXPANSION BY HEAT. 239 purpose in a piece of sheet-iron. If the rod be now heated in the fire, it expands and becomes larger, and can not be thrust into the hole. The expansion may be more visibly shown and accurately measured by means of an instrument called the Pyrometer {Fig. 201). The rod a b, secured to its place by a screw at Fig. SOI. a, presses against the lever c, and this against the lever, or index, d, both of which multiply the motion, and render the expansion very obvious to the eye when the rod is heated by the lamps. If the rod should expand one fiftieth of an inch, and each lever multipHes twen- ty times, then the index (or second lever) will move along the scale eight inches ; for 20 times 20 are 400, and 400 50ths of an inch are 8 inches. Many cases showing the expaBsion of heated bodies occur in ordinary practice. One is afforded by the manner in which the parts of carriage wheels are bound together. The tire is made a little smaller than the wooden part of the wheel ; it is then heated till, by 240 HEAT. expanding, it becomes large enough to be put on, when it is suddenly cooled with water, and by its powerful contraction binds every part of the wheel together with great force. Hogsheads are firmly hooped with iron bands in the same way, with more force than could be ever given by driving on with blows of the mallet. This principle was very ingeniously applied in draw- ing together two expanding brick walls of a large building in Paris, which threatened to burst and fall. Holes were drilled in the opposite walls, through which strong iron bars across the building projected, and cir- cular plates of iron were screwed on these projecting ends. The bars were then heated, which increased their length ; the plates were then screwed closely against the walls. On cooling, they contracted, and drew the walls nearer together. The process was re- peated on alternating bars, until the walls were re- stored to their perpendicular positions. All tools, where the wooden handles enter iron sock- ets, will hold more firmly if the metal is heated before inserting the wood. The metallic parts of pumps sometimes become very difficult, to unscrew, and a case has occurred where two strong men could not start the screws, until a by- stander suggested that the outer piece be heated, keep- ing the inner cool, when a force of less than ten pounds quickly separated them. In other cases, where the large iron nuts have been thoughtlessly screwed, while warmed with the hands, on the cold metaUic axles of wood-sawing machines in winter, they have contracted so that the force of two or three men has been insuffi- cient to turn them. THE STEAM-ENGINE. 241 The sudden expansion of bodies by heat sometimes causes accidents. Thick glass vessels, when unequally heated, expand unequally, and break. Heated plates of cast iron or cast kettles are very Uable to be frac- tured by suddenly pouring cold water upon them. The same effect has been usefully appUed in splitting the scattered rocks which encumber a farm, and which are too large to remove while entire. Fires are built upon them ; the upper surface expands, while the low- er remains cold, and large portions are successively separated in scales, and sometimes the whole rock is severed. The only care needed is to observe atten- tively and remove with an iron bar any parts which may have become loosened by the heat, and which would prevent the heat from passing to other portions. One man will thus attend to a large number of fires, and will split in pieces ten times as many rocks in a day as by drilling and blasting. Fig. 202. THE STEAM-ENGINE. The Steam-engine owes its power to the enormous expansion of water at the moment it is converted into steam, which is about 1600 times its bulk when in the form of water. The principle on which the steam-engine acts may be understood by a very simple instrument represented in Fig. 202. A glass tube with a small bulb is furnished with a solid air-tight piston, capable of working up and down. The water in the bulb, a, is heated with a spirit-lamp or sand-bath ; the rising L 242 HEAT. steam forces up the piston. Now immerse the bulb in cold water or snow, and the steam is condensed again into water, the tube is left vacant, and the pressure of the atmosphere forces down the piston. By thus al- ternately applying heat and cold, it is driven up and down like the piston of a steam-engine. The only dif- ference is, the steam-engine is furnished with appara- tus so that this application of heat and cold is perform- ed by the machine itself. The bulb represents the boiler, and the tube the cylinder ; but ia the steam- engine the boiler is separate, and connected by a pipe with the cylinder ; and instead of applying the cold water directly to the cylinder, it is thrown into an- other vessel called the condenser, connected with the cyhnder. "When Newcomen, who made the first rude regular- ly- working engine, began to use it for pumping water, he employed a boy to turn a stop-cook, coimected with the condenser, every time the piston made a stroke. The boy, however, soon grew tired of this incessant la- bor, and endeavored to find some contrivance for relief. This he effected by attaching a rod from the piston or working-beam to the cock, which was turned by the machine itself at every stroke. This was the origin of the first self-acting engine. The different parts of a common steam-engine may be understood from the following figures, one represent- ing the boiler, and the other the working machinery. The boiler, B {Fig. 203), contains water in the low- er part and steam in the upper ; F B is the fire ; v ois the feed-pipe ; v, a valve, closed by the lever, b c a, whenever the boiler is full enough, by means of the ris- THE STEAM-ENGINE. 243 ing of the float, S, and opened whenever the float sinks from low water. M, barometer gauge, to show the Fig. 203, Bffiler of Steam-engine. pressure of the steam ; w, weight on the lever, e 6, for holding down the safety-valve : this lever being grad- uated like a steelyard, the force of the steam may he accurately weighed. U is a valve opening downward, to prevent the hoiler being crushed by atmospheric pressure, by allowing the air to pass in whenever the steam happens to decline. Two tubes with stop-cocks, c and d, one just below the water-level and the other just above it, serve to show, by opening the cocks, whether the water is too high or too low. The working part of the engine is represented in the figure on the following page {Fig. 204). The steam enters by the pipe, s, from the boiler on the other side of the brick wall, as shown in Fig. 203. The steam 244 Low-pressure Steam-engine. « passes through what is called & four-way-cock, a, first into the lower, then into the upper end of the cylinder, C, as the piston, P, moves up and down ; this is regu- lated by the levers, y y. The piston-rod, E, is attach- ed to the working-beam, B F, turning on the centre, A. The rod, F R, turns the fly-wheel, H H, and drives the mill, steam-boat, or machinery to be put in motion. The condenser, j, shown directly under the cylinder, remains to be described. It is immersed in a cistern of cold water, and is connected by pipes to the upper and lower end of the cylinder. Through these pipes the steam passes out of the cylinder, first from one end and then from the other, and is condensed into water by a jet of cold water thrown into it by the injection- cock. When condensed, it is pumped out by the pump, 0, into the well or reservoir, W, and then again into THE STEAM-ENGINE. 245 the feed-pipe of the boiler. Warm water is thus con- stantly supplied to the boUer, and effects a great sav- ing of fuel. The supply of steam and the motion of the engine are regulated by the governor, G. When the motion is too fast, the two suspended balls, which revolve on a vertical or upright axis, and which hang loosely like pendulums, are thrown out from the axis, producing the movement of a rod which shuts the steam-valve. When the motion is too slow, the balls approach the axis and open the valve. In high-pressure engines the steam is not condensed, but escapes into the open air at every stroke of the pis- ton, which produces the loud, successive puffs of all engines of this Idnd. The steam-engine, in its most perfect form, is a striking example of human ingenuity, and its qualities are thus described by Dr. Arnott : " It regulates with perfect accmracy and uniformity the number of its strokes in a given time, and records them as a clock does the.beat^ of its pendulum. It regulates the quan- tity of steam ; the briskness of the lire ; the supply of water to the boiler ; the supply of coals to the fire. It opens and shuts its valves with absolute precision as to time and manner ; it oils its joints ; it takes out any air accidentally entering parts which should be vacu- ous ; and when any thing goes wrong which it can not of itself rectify, it warns its attendants by ringing a bell ; yet, with all these qualities, and even when ex- erting a force of six hundred horses, it is obedient to the hand of a child. Its aliment is coal, wood, and other combustibles. It consumes none while idle. It 246 HEAT. never tires, and wants no sleep. It is not subject to any malady when originally weU made, and only re- fuses to work when worn out with age. It is equally active in all climates, and will do work of any kind : it is a water-pumper, a miner, a sailor, a cotton-spin- ner, a weaver, a blacksmith, a miUer, a printer, and is indeed of all occupations ; and a smaU engine in the character of a steam pony may be seen dragging after it, on an iron rail- way, a hundred tons of merchandise or a thousand persons with the speed of the wind." Steam-engines have been much used on large farms in England for thrashing, grinding the feed of animals, cutting fodder, and for other purposes. They have been less used here, but may prove useful for large estab- lishments, where the teams for ordinary tillage are in- sufficient for stationary labor. More difficulty exists in their use for plowing, in con- sequence of the labor and expense of moving frequent- ly so heavy a machine, and the still greater difficulty of using a locomotive power like that on rail-roads on the soft surfaces of farms. EXCEPTION TO EXPANSION BY HEAT. A striking exception to the general law of expansion by heat occurs in the freezing of water.* During its change to a solid state, it increases in bulk about one twelfth, and this expansion is accompanied with a great force. The bottoms of barrels are burst out, and cast-iron kettles are spUt asunder, when water is suf- fered wholly to freeze in them. Lead pipes filled with * There are a very few other substances which expand on passing from a liquid to a solid state. EXCEPTION TO EXPANSION BY HEAT. 247 ice expand ; but if it is often repeated, they are crack- ed into fissures. A strong brass globe, the cavity of which was only one inch in diameter, was used by the Florentine academicians for the purpose of trying the expansive force of freezing water, by which it was ■ burst, although the force required was calculated to be equal to fourteen tons. Experiments were tried at Quebec, in one t)f which an iron plug, nearly three pounds in weight, was thrown from a bomb-shell to the distance of 415 feet ; and in another, the shell was burst by the freezing of the water which it con- tained. This expansion has a most important influence in the pulverization of soils. The water which exists through aU. their minute portions, by conversion to frost, crowds the particles asunder, and when thawing takes place, the whole mass is more completely mel- lowed than could possibly be effected by the most per- fect instrument. This mellowing is, however, of only short duration, if the ground has not been well drain- ed to prevent its becoming again packed hard by soak- ing with water. But this is not the most important result from the expansion of water. Much of the existing order of na- ture and of civilized life depends upon this property ; without it the great mass of our lakes and rivers would become converted into solid ice ; for, as soon as the surface became covered, it would sink to the bottom, beyond the reach of the summer's sun, and successive portions being thus added, the great body of all large rivers and lakes would become permanently frozen. But instead of this disastrous consequence, the ice, by 248 HEAT. resting upon the surface, forms an effectual screen from the cold "winds to the water below. SECTION III. LATENT HEAT. If a vessel of snow, which has been cooled down to several degrees below freezing by exposure to the se- vere cold of winter, be placed over a steady fire with a thermometer in the snow, the mercury will rise by the increasing heat of the snow until it reaches the freez- ing point. At this moment it will stop rising, and the snow will begin to melt ; and although the heat is all the time passing rapidly into the snow, the thermom- eter will remain perfectly stationary till it is all con- verted to water. The heat that goes to melt the snow does not make it any hotter ; in other words, it becomes latent (the Latin word for hidden), so as neither to af- fect the sensation of the hand or to raise the thermom- eter. Now it has been found that the time required to melt the snow is sufficient to heat the same quantity of water, placed over the same fire, up to 172 degrees, or 140 degrees above fi-eezing; that is, 140 degrees have become latent, or hidden, in melting the snow. This same amount of heat may be given out again by placing the vessel of water out of doors to freeze. A thermometer will show that the water is growing colder by the escape of the heat, till freezing commen- ces. After this it still continues to pass off, but the water becomes no cold^ till all is frozen, as it was only the latent heat of the water that was escaping. A simple and familiar experiment exhibits the same LATENT HEAT OF STEAM. 249 principle. Place a frozen apple, which thaws a little below freezing, in a vessel of ice-cold water. The la- tent heat of the water immediately passes into the apple and thaws it, and in an hour or two it will he found hke a fresh apple and entirely free from frost; hut the latent heat having escaped from the water next the apple, a thick crust of ice is found to en- case it. The amount of latent heat may be shown in still another way. Mix a pound of snow at 32 degrees, or at freezing, with a pound of water at 172 degrees. All will be melted, but the two pounds of water thus formed wiU be as cold as the snow, showing that for melting it the 140 degrees in the hot water were all made latent. ADVANTAGES OF LATENT HEAT. If no heat became latent by the conversion of ice and snow to water, no time would, of course, be required for the process, and thawing would be instantaneous. On the approach of warm weather, or at the very mo- ment that the temperature of the air rose above freez- ing, snow and ice would all dissolve to water, and ter- rific floods and inundations would be the immediate consequence. LATENT HEAT OF STEAM. A still larger amount of latent heat is required for the conversion of water into steam ; for, again place the vessel of water with its thermometer on the fire, it will rise, as the heat of the water increases, to 212 degrees, and then commence boiling. During all this L2 250 HEAT. time it will now remain stationaiy at 213, tUl the wa- ter is all boUed away. This is found to require nearly five times the period needed to heat from freezing to "hoiling ; that is, nearly one thousand degrees of heat are made latent by the conversion of water into steam. When the steam is condensed agaia to water, this heat is given out. Hence the use made of steam con- veyed in pipes for heating buildings, and for boiUng large vats or tubs of water, by setting free this large amount of latent heat which the fire has imparted to it. GREEN AND DRY WOOD FOR FUEL. A great loss is often sustained in burning green wood for fuel, from an ignorance of the vast amount of latent heat consumed to drive off the water the wood contains. When perfectly green, it loses about one third of its weight by thorough seasoning, which is equal to about 25 cubic feet in every compact cord, or 156 imperial gallons. Now aU this water must be evaporated before the wood is burned. The heat thus made latent and lost, being five times as great as to hea,t the water to boiling, is equal to enough for boiling 780 imperial gallons in burning up every cord of green wood. The farmer, therefore, w^ho burns 25 green cords ia a winter, loses heat enough to boil more than fifteen thousand gallons of water, which would be saved if his wood had been previously well seasoned under shelter. The loss in using green fuel is, however, sometimes overrated. It has been found by experiment that one pound of the best seasoned wood is sufficient to heat GEEEN AND DRY WOOD FOR FUEL. 251 27 lbs. of water from the fireezing to the hoihng point.* This will be equal to heating and evaporating four pounds of water by every pound of wood. The 25 cubic feet of water, therefore, in every cord of green wood, weighing about 1500 pounds, would require near- ly 400 pounds of wood for its evaporation, or about one seventh or one eighth of a cord. Hence we may infer that seven cords of dry wood are about equal to eight cords of green. This imperfect estimate will apply only to the best hard wood, and will vary exceedingly with the different sorts of fuel ; the more porous the wood becomes, the greater will be the necessity for thorough seasoning. Superficial observation often leads to very erroneous conclusions. Seasoned wood will sometimes burn with great rapidity, and, producing an intense heat for a short time, wiU favor an over-estimate of its superior- ity. Green wood, on the other hand, kindles with dif- ficulty, and burns slowly and for a long time ; hence, where the draught of the chimney can not be control- led, it may be the most economical, because a less pro- portion of heat may be swept upward than by the more * The following results show the heating power of several combust- ibles : 1 lb. of wood (seasoned, but still holding 30 per cent, of water) raised from 32° to 212° 27 lbs. water. 1 lb. of alcohol 68 " " 1 lb. of charcoal 78 " " 1 lb. of oil or wax 90 " " 1 lb. of hydrogen 216 " " It should be remembered that by ordinary modes of heating water, a very large proportion of the heat is wasted by passing up the chim- ney and into surrounding bodies, and the air. 252 HEAT. violent draught produced from dry materials. Where the draught can be perfectly regulated, however, seas- oned wood should he always used, both for convenience and comfort, and for economy. Where wood is to he drawn to a distance, the pre- ceding estimate shows that the conveyance of more than half a ton of water is avoided in every cord by seasoning. RADIATION OF HEAT. 253 CHAPTER II. RADIATION OF HEAT. The passage of heat through conductmg bodies has been aheady explaiiie4. There is another way in which it is transmitted, termed radiation, in which it is thrown off instantaneously in straight lines from hot bodies, in the same way that light is thrown off from a candle. A familiar instance is furnished by the common or open fire-place, before which the face may be roasted with the radiated heat, while the back is chilled with cold. A screen held in the hand will intercept this radiated heat, showing that it flies in right lines like the rays of light. Eadiated heat is reflected by a polished metallic surface, in the same way that hght is reflected by a looking-glass. A plate of bright tin held near the fire will not for a long time become hot, the heat being reflected from it without entering and heating it. But if it be blackened with smoke, it will no longer reflect, but absorb the heat, and consequently will speedily become hot. This experiment may be easily tried by placing a new tin cup containing water over a char- coal fire, which yields no smoke. The heat will be reflected into the fire by the tin, and the water wiU scarcely become warm. But if a few pine shavings be thrown on this fire to smoke the surface of the tin, it will then absorb the heat rapidly, and soon begin to boil. This explains the reason that bread bakes more 254 HEAT. slowly in a new tin dish, and that a polished andiron before a fire is long in becoming hot. A concave burning-mirror, which throws the rays of heat to a focus or point, may be made of sheet-tin, by beating it out concave so as to fit a regularly curved gauge. If a foot in diameter, and carefully made, it will condense the rays of heat so powerfully at the fo- cus, when held several feet from the fire, as to set fire to a pine stick or to flash gunpowder {Fig. 205). Fig. 205. The reflection of radiated heat may be beautiful- ly exhibited by using two such concave tin mirrors. Place them on a long table several feet apart, and as- certain the focus of each by means of the light of a candle. Then place in the focus of one a red-hot iron ball, or a small chafing-dish of burning charcoal. In the focus of the other place the wick of a candle with a small shaving of phosphorus in it. The heat wid be reflected, as shown by the dotted lines [Fig. 206), Fig. 206. DEW AND FROST. 255 and, setting fire to the phosphorus, ■will light the candle. If a thermometer be placed in the focus of one mir- ror while the hot iron ball is in the other focus, it will rise rapidly ; but if a lump of ice be substituted for the ball, the thermometer will immediately sink, and will continue to do so until several degrees lower than the surrounding air; because the thermometer radi- ates more heat to the mirrors, and then to the ice, than the ice returns. DEW AND FROST. All bodies are constantly radiating some heat, and if an equal amount is not returned by others, they grow colder, like the thermometer before the lump of ice. Hence the reason that on clear, frosty nights, ob- jects at the surface of the earth become colder than the air that surrounds them. The heat is radiated into the clear space above without being returned; plants, stones, and the soil thus become cooled down below freezing, and, coming in contact with the moist- ure of the air, it condenses on them and forms dew, or freezes into white frost. Clouds return or prevent the passage of the heat that is radiated, which is the rea- son there are no night-frosts in cloudy weather. A very thin covering, by intercepting the radiated heat, wUl often prevent serious injury to tender plants. Even a sheet of thin muslin, stretched on pegs over garden vegetables, has afforded sufficient protection, when those aroimd were destroyed. 256 HEAT. FROST IN VALLEYS. On hills, where the wind blows freely, it tends to restore to plants the heat lost by radiation, which is the reason that hills are not so liable to sharp frosts as still valleys. When the air is cooled it becomes heav- ier, and, rolling down the sides of valleys, forms a lake of cold air at the bottom ; this adds to the liabihty of frosts in low places. The coldness is frequently still further increased by the dark and porous nature of the soil in low places radiating heat faster to the clear sky than the more compact upland soU. A knowledge of these properties teaches us the im- portance of selecting elevated places for fruit-trees, and all crops hable to be cut off by frost ; and it also explains the reason that the muck or peat of drained swamps is more subject to frosts than other land on the same lev- el. Therefore, corn and other tender crops upon such porous soils must be of the earliest ripening kinds, so as to escape the frosts of spring by late planting, and those of autumn by early maturity. REMARKABLE EFFECTS OF HEAT ON WATER. The effects of heat and cold on water are of a very interestuig character. Without its expansion in freez- ing, the soil would not be pulverized by the frost of winter, but would be found hard, compact, and diffi- cult to cultivate in spring ; without its expansion into steam, the cities which are now springing up, and the continents that are becoming peopled, through the in- fluence of rail- ways, steam-ships, and steam manufac- tures, would mostly remain unbroken forests ; without REMARKABLE EFFECTS OF HEAT ON WATER. 257 the crystallization of water, the beautiful protection of plants by a mantle of snow, in northern regions, would give place to frozen sterility; without the conversion of heat to a latent state in melting, the deepest snows would disappear in a moment from the earth, and cause disastrous floods ; without its conversion to a la- tent state in steam, the largest vessel of boUing water would instantly flash into vapor. All these facts show that an extraordinary wisdom and forethought planned these laws at the creation ; and even what aopears at first glance as an almost accidental exception in the contraction of bodies by cold, and which causes ice to float upon water, preventing the entire masses of riv- ers and lakes from becoming permanently frozen, fur- nishes one out of an innumerable array of proofs of creative design in fitting the earth for the comfort and sustenance of its inhabitants. APPENDIX. APPARATUS FOR EXPERIMENTS. Vos the assistance of lecturers, teachers, and home students, the fol- lowing list is given of cheap and simple apparatus and materials for performing most of the experiments described in this work. These experiments, although simple, exhibit principles of much practical im- portance. A few articles of a more costly character are given in a second list. 1. Inertia apparatus, p. 23. The concave post or stand is sufficient, the snapping being done by the finger, although a spiing-snap performs the experiment more perfectly. 2. Weight with two hooks and fine thread, p. 23. 3. The inertia of falling bodies may be simply shown, and the pile- engine illustrated, by placing a large wooden peg or rod upright in a box of sand, and then dropping a weight upon its head at different heights, which will drive the rod into the sand more or leaa, according to the distance passed through by the falling weight. 4. A straw-cutter, so made that the fly-wheel can be easily taken off, will ahow in a very striking manner the efficacy of this regulator of force. 5. Two lead musket balls will exhibit the experiment in cohesion, p. 42. Balls or lead weights with hooks may be separated by sus- pending weights to show the amount of force required to draw them asunder. Metallic buttons or plates an inch in diameter, with hooks, will show the great strength needed to separate them when coated with grease, p. 42. 6. Capillary tubes of different sizes, two straight small panes of glass, and a vessel of water, highly colored with cochineal or other dye, to exhibit capillary attraction. 7. Glass tube, piece of bladder, and alcohol, for experiment described on p. 49. 8. The cylinder for rolling up the inclined plane, represented by 260 APPENDIX. Fig. 18, p. 50, may be very easily made by using a round pasteboard box a few inches in diameter, and securing a piece of lead inside by loops made with a needle and thread. The object shown by Fig. 19 may be cut in one piece out of a pine shingle, the centre rod being lengthwise with the grain ; the two extremities are shaved small, and wound with thick sheet-lead, and the whole then colored or painted a dark hue, to render the lead inconspicuous. The experiment with the penknives, p. 51, is very simple, care being taken to insert them low enough in the stick. 9. Irregular pieces of board, variously perforated with holes, and furnished with loops to hang on a pin, may be used to determine the centre of gravity, according to the principle explained by Fig. 21, p. 51. 10. Portions of plank and blocks of wood, with the centre of gravity determined as in the last experiment, may have a plumb-line (which may be a thread and small perforated coin) attached to this centre, and then be placed on differently inclined surfaces, to show their upsetting just as this line of direction falls without the base. Toy-wagons, bought at the toy-shops, may be variously loaded and used in experi- ments of this sort. 11. Experiments with the lever of the first kind may be easily per- formed by the use of a flat wooden bar, two or three feet in length, marked into inches, and placed on a small three-cornered block as a fulcrum. Weights, such as are used for scales, may be variously placed upon the lever. Levers of the second and third kind, which are lifted instead of borne down, may have a cord attached to the point where the power is to be applied, running up over a pulley or wheel, with a weight suspended to the other end. 12. An axle, furnished with wooden wheels with grooved edges, of different sizes, may be used to exhibit the principle of the wheel and axle, in connection with scale-weights that are furnished with hooks. The power of combined cog-wheels may be shown by a combination like that represented on p. 76, using weights for both cords. 13. Interesting experiments with the inclined plane, at different de- grees of slope, by a contrivance similar to that represented by Fig. 87, p. 104, with the addition of a small wheel at the upper side for a cord to pass over. This cord is fastened at one end to a light toy-wagon, running up and down the plane, and at the other to a weight suspend- ed perpendicularly just beyond the upper edge of the plane. The wagon is variously loaded with weights to counterpoise the suspended weight at different degrees of inclination. APPENDIX. 261 14. A lecturer may quickly demonstrate before a class the small in- crease in the length of a road, in consequence of a considerable curve to one side of a straight line (as shown by Fig. 70), by using a cord for measuring, the diagram being marked on a board or the wall. 15. A round stick of wood, and a long, wedge-shaped slip of paper, easily show the principle of Fig. 75, p. 94. 16. A cog-wheel with endless screw and winch. Fig. Tt, p. 95, ex- hibits distinctly the great power of the screw in this combination. 17. Pine sticks, two feet long, and one fourth to one half inch through, of different shapes and sizes, supported at each end, and with weights hung at the middle till they break, may be made to illustrate the principles described on p. 100, 102. 18. Some of the principles of draught may be shown, and especially those in relation to the different angles of inclination for hard and soft roads, by using a common spring-balance as a dynamometer, attached to a hand-wagon, and also to a sliding block of wood. 19. Bent glass tubes, with arms of different sizes to indicate the up- ward pressure of liquids, may be procured cheaply at glass-works. The experiment described by Fig. 154, p. 183, may be rendered easy and interesting by purchasing a large and perfectly-working syringe, and attaching to its nose, by means of sealing wax, a slender glass tube two or three feet long. Fill the syringe with water, leaving the tube empty ; then, with the tube upright, drive the water up through it with the piston of the syringe, and the increased weight felt on the piston as the column of water rises will be very evident. 20. A hydrostatic bellows a foot in diameter, made by any good mechanic, will answer the purpose well, and exhibit an important principle. 21. Specific gravities may be shown before a class by a common balance and a fine cotton or silk thread. 22. A tin pail, with a hole half an inch or an inch in diameter at the bottom, will show the contracted stream which pours from it, p. 191. A short tin tube, with a slight flange at the upper' end (quickly made by any tin-worker), fitted into this hole, will increase the discharge, as shown by Figs. 159, 160, and the difference in time for emptying the vessel may be measured by a stop-watch. 23. Archimedes' screw is readily made by winding a lead pipe round a wooden cylinder. 24. A glass syphon, filled with cochineal water, shows distinctly the theory of waves, by blowing with the mouth into one end. 262 APPENDIX. 25. Any vessel, filled with sand which has been heated over a fire, with rods of different substances, nearly of an equal size and length, and thrust with one end into the hot sand, in an inclined or nearly horizontal position, will exhibit the various conducting powers of these rods by melting pieces of wax or tallow placed on the ends most re- mote from the sand. 36. The expansion by heat may be demonstrated by fitting an iron rod to a hole in sheet iron ; on heating the bar, it can not be made to enter. Or, if a hot iron ring be slipped on a tapering cold iron rod, it will contract on cooling so that the force of a man can not withdraw the rod, 27. The rising and descending currents in a vessel of heating water are easily rendered visible by throwing into a glass vessel, or flask, over a lamp, particles of sawdust from any hard green wood, whose specific gravity is about the same as that of water. 28. Instrument figured on p. 241, for showing the principle of the steam-engine. 29. Experiments in latent heat may be easily exhibited with the as- sistance of a common thermometer. 30. Tin mirrors for showing radiation, p. 254. Second List, containing a few of the more costly pieces of appara- tus for experiments as described in this treatise. 1. A good compound or solar microscope will exhibit the minute animalcules described under the head o{ Divisibility. The larger of these animalcules may be seen in old strong vinegar, and the smaller in a drop of water taken from a vessel in which a portion of raw po- tato has been soaked a few hours in a warm place. The same instru- ment wiU show the pores of wood mentioned under the head Impene- trability. 2. Atwood's machine, p. 39. 3. A good dynamometer for field experiments is of great value and importance. 4. An air-pump, with the several pieces of apparatus connected with it, shows, in an interesting and striking manner, several important principles. APPKNDIX. 263 HYDROSTATICS AND HYDRAULICS. TABLE OF SPECIFIC GRAVITIES. Metals. Gold, pure 19.36 " standard 17.16 Mercury 13.58 Lead 11.35 Silver 10.50 Copper 8.82 Iron 7.78 " cast 7.20 Steel 7.82 Brass, common 7.82 Tin 7.29 Zinc 6.86 Stones and Earths. Brick 1.90 Chalk 2.25 to 2.66 Clay 1.93 Coal, anthracite, about. . .1.53 Coal, bituminous 1.27 Charcoal 44 Earth, loose, about 1 .50 Flint 2.58 Granite, about 2.65 Gypsum 1.87 to 2.17 Limestone 2.38 to 3.17 Lime, quick 80 Marble 2.56 to 2.69 Peat 60 to 1.32 Salt, common 2.13 Sand 1.80 Slate 2.67 Woods — dry. Green wood often loses one third of its weight by seasoning, and sometimes more. The same kind varies in compactness with soil, growth, exposure, and age of the trees. Apple 68 to .79 Ash, white 72 to .84 Beech 72 to .85 Box 91 to 1.32 Cherry 71 Cork 24 Ehn 58 to .67 Hickory 84 to 1.00 Maple 65 to .75 Pine, white 47 to .56 Pine, yellow 55 to .66 Oak, English 93 to 1.17 " white 85 " live 94 to 1.12 Poplar, Lombardy .40 Pear 66 Plum 78 Sassafras 48 Walnut 67 Willow 58 364 APPENDIX. MisceUaneous. Beeswax 96 Butter 94 Honey 1.45 Lard 94 MUk 1.03 Oil, linseed 94 Oil, whale 92 " turpentine 87 Sea water 1.02 Sugar 1.60 Tallow 93 Vinegar 1.01 to 1.08 Weights of a Cubic Foot of various Substances, from which the Bulk of a Load of one Ton may he easily calculated. Cast Iron 450 pounds. Water 62 " White pine, seasoned, about 30 " White oak, " " 52 " Loose earth, about 95 " Common soil, compact, about 124 " Clay, about 135 " Clay with stones, about 160 " Brick, about 125 " Bulk of a Ton of different Substances. 23 cubic feet of sand, 18 cubic feet of earth, or 17 cubic feet of clay, make a ton. 18 cubic feet of gravel or earth before digging, make 27 cubic feet when dug ; or the bulk is increased as three to two. There- fore, in filling a drain two feet deep above the tile or stones, the earth should be heaped up a foot above the surface, to settle even with it, when the earth is shoveled loosely in. DISCHARGE OF WATER THROUGH PIPES'. Table showing the amount of water discharged per minute through an orifice one inch in diameter ; also through a tube one inch in di- ameter and two inches long, according to experiment. To ascertain the amount in gallons, divide the cubic inches by 231, APPENDIX. 265 Height of head of Water. Amount discharged " "fice. 1 Par: 2 3 4 5 6 7 8 9 10 H 12 13 14 15 through Ori foot* 2,722 cub, 3,846 4,710 5,436 6,075 6,654 ..'. 7,183 7,672 8,135 8,574 8,990 9,384 9,764 10,130 10,472 Amount disclmrged through Tube. 3,539 cub. in. 5,002 6,126 7,070 7,900 8,654 " 9,340 " 9,975 10,579 11,151 11,693 12,205 12,699 13,177 13,620 VELOCITY OF WATEE IN PIPES. The following table shows the height of a head of water required to overcome the friction m horizontal pipes 100 feet long, and to produce a certain velocity, according to Smeaton : Bore of Pipes. & Inches in. in. 1 4.5 Ifoot. 16.7 n/eet. in. 85.1 a/eet. ft. in. 4 9.7 Sfeet. ft. in. 10 1.0 ifeet. ft. in. 17 10.0 Sfeet. ft. in. 28 0.2 4" 3.0 11.1. 23.3 3 2.5 6 8.6 11 10.6 18 8.1 1 2.2 8.4 17.5 2 4.9 5 0.5 8 11.0 14 0.0 li 1.8 6.7 14.0 1 11.1 4 0.4 7 1.6 11 2.5 1^ 1.5 5.6 11.7 1 7.2 3 4.3 5 11.3 9 4.1 i.r 1.3 4.8 10.0 1 4.5 2 10.6 5 1.1 8 0.1 o 1.1 4.2 8.7 1 2.4 2 6.2 4 5.5 7 0.0 •2-i- 1.0 3.7 7.8 1 0.8 2 9.9 3 11.6 6 2.7 2} 0.9 3.3 7.0 11.5 2 0.2 3 6.8 5 7.2 3 0.7 2.8 5.0 9.6 1 8.3 2 11.7 4 8.0 3: 0.6 2.4 5.0 8.2 1 5.3 2 6.6 4 0.0 4 0.0 2.1 4.4 7.2 1 3,1 2 2.7 3 6.0 Look for the velocity of the water per second in the pipe, in the up- per line ; and in the column beneath it, and opposite the given diam- * A Paris foot Is ahout 12 4-5 U. S. inches, and 15 Paris feet are about 16 U. S. feet. M 266 APPENDIX, eter of the pipe, is the height of the column or head required to obtab the reqviired velocity. To find the quantity of water discharged each minute, multiply the velocity by 12, which will give the inches per second ; then multiply this product by 60, which will give the inches per minute ; then, to change these cylindrical inches into cubic inches, multiply by 4 and divide by 5.* Divide the cubic inches by 231, and the result will be gallons. By comparing this table with the next preceding, we shall perceive that the water flows from three to four times as fast through the tube two inches long, as through a tube one hundred feet long, the diameter of the tube and the head of water being the same. RULE FOR THE DISCHARGE OF WATER. The following general formula, or rule applicable to different cases, has been furnished by a practical engineer. It may be useful in ascer- taining the quantity required to fill the driving pipe of a water-ram, and for various other purposes occasionally occurring in practice. Let A represent the fountain or reservoir from which water is to be conveyed to the trough B through the pipe L. Let N be the height of the surface of the water in the reservoir, above the place of dis- charge, and let D be the diameter of the tube in the smallest part. It is required to find the quantity Q which will be discharged in a second rftime. The length and height being given in feet, and the diameter of the tube in inches, the formula, when the quantity is required ia gallons, is as follows : Q = 0.608 v^(D55). * This gives the cuMo inches very nearly ; but, to be more accurate, multiply by the decimal .7854, wMcli represents the diSerence between the area of a square and of a circle. APPENDIX. 267 In order to make the above formula more intelligible : Let L = 80 rods or 1320 feet. ■" H = 50 feet. " D = 3 inches. " Q = gallons. 50 \ Then Q = 0.608^(32 X j^j = 0.67 ; or, the same may be thus expressed in words. Divide the height (50) by the length (1320) ; multiply the quotient by the fifth power of the diameter (fifth power of 2 = 33) ; extract the square root of the product, which, being multiplied by 0.608, will give (0.67) the number of gallons the tube will discharge in one second ; which in this case is 40 gallons in one minute. All the Books on this Catalogue sent b-g Mad, to any part of the Union, free of postage, upon receipt of Price. OATALOGUE OF BOOKS ON AGRICULTURE AND HORTICULTURE, PUBLISHED BY j^. o. :m:oor-e sc co., (Late 0. M. Saxton S{ Co.,) Ko. 140 FTJIiTON STREET, NEW YOEK.. SUITABLE FOR SCHOOL, TOWN, AGRICULTURAL, & PRIVATE LIBRARIES. AHEBIGAir FABKEB'S ENC7CL0FEDIA, $4 00 As A Book op Reference fok the Farmer or G-ardenek, this Work -is superior to any other. It contains Reliable Information for the Cultivation of every variety of Field and Garden Crops, the use of all kinds of Manures, descriptions and figures of American insects ; and is, indeed, au Agricultural Library in itself, con- taining twdae hwndred pagex, octavo, and is illustrated by numerous engravings of Grasses, Grains, Animals, Implements, Insects, &c., &c. By Gouvbrnbur Embrsos of PBiraSYLVANIA. AKEEICAW WEEDS AND TJSBFUI PLANTS, 1 80 An Illusteated Edition of Agricultural BoTANr ; An Enu- meration and Description of Weeds and Useful Plants which merit the notice or require the attention of American Agriculturists. By Wm. DASuNGToif, M. D. Re- vised, with Additions, by George Tourbbr, Prof, of Mat. Med. and Botany in the New York College of Pharmacy. Illustrated with nearly 300 Figures, drawn expressly for this work. ALLEN'S (B. L.) AHEBICAN FARM BOOK, ..... 1 00 Or a Compend of American Aqbicultuke ; being a Practical Treatise on Soils, Manures, Draining, Irrigation, Grasses, Grain, Roots, Fruits, Cotton, Tobacco, Sugar Cane, Rice, and every Staple Product of the United States ; with the best methods of Planting, Cultivating and Preparation for Market* Ulustrated-with more than 100 engravings. ALLEN'S (B. L.) DISEASES OF DOMESTIC ANtSIALS, • - 7S Being a History and Description of the Horse, Mule, Cattle, Sheep, Swine, Poultry and Farm Dogs, with Directions for their Management, Breeding, Crossing, Rearing, Feeding, and Preparation for a Profitable Market ; also, their Diseases and Remedies, togjther with full Directibns for the Management of the Dairy, and the comparative Economy and Advantages of Working Animals, — ^the Horse, Mule, Oxen, &c. ALLEN'S (L. F.) BUBAL ABCHITECTTTBE, 1 26 Being a Complete Description op Farm Houses, Cottages and Out Buildings, comprising Wood Houses, Workshops, Tool Houses, Carriage and Wagon Houses, Stables, Smoke and Ash Houses, Ice Houses, Apiaries or Bee Houses, Poultry Houses, Rabbitry, Dovecote, Piggery, Barns and Sheds for Cattle, &c., &c. ; together with Lawns, Pleasure Grounds and Parks ; the Flower, Fruit and Vegetable Garden ; also, the best method of conducting water into Cattle Yards and Houses. Beautifully illustrated. ALLEN (J. FISK) ON THE CTJLTTJBE OF THE GBAPE, - - 1 00 A Practical Treatise on the Culture and Treatment of the Grape Vine, embracing its History, with Directions for its Treatment in the United States of America, in the Open Air and under Glass Structures, with and without Artificial Heat. Books published hy A. O. Moore & Co. AMEiaCAN ARCHITECT, 00 Comprising Original Designs of Cheap Country and Village Residences, witli Details, Specifications, Plans and Directions, and an Estimate of the Cost of eacli Design, By John W. Krrcfl, Architect- First and Sucond Series^ 4to, bound in 1vol. AMERICAN FLORIST'S GXTEDE, - - - 75 Comprising the American Rose Culturist, and Every Lady her own Flower Gardener. BARRY'S FRUIT GARDEN, - - * 1 25 A Treatise, Intended to Explain and Illustrate the Physi- ology of Fruit Trees, the Theory and Practice of all Operations connected with the Propagation, Transplanting, Pruning and Training of Orchard and Garden Trees, as Standards, Dvrarfs, Pyramids, Espalier, &c. The Laying out and Arranging different kinds of Orchards and Gardens, the selection of suitable varieties for diflTereut purposed and localities, Gathering and Preaerving Fruits, Treatment (rf Diseases, Destruction of Insects, Description and Uses of Implements, &c. Illustrated with upwards of 15<7 Figures. By P. Barry, of the Mount Hope Nurseries, Rochester, N. Y. BEMENTS (C. K.) RABBIT FAJfCIEB, - bO A Treatise on the Breeding, Rearing, Feeding and General Management of Rabbits, with Remarks upon their Diseases and Remedies, to which are added Full Directions for the Construction of Hutches, Rabbitries, &c., together with Recipes for Cooking and Dressing for the Table. Beautifully illustrated, BLAKES (REV. JOHN L.) FARMER A^: HOME, - - - - 1 2S A Family Text Book for the Country ; being a Cyclopedia of Agricultural Implements and Productions, and of the more important topics in Domestic Economy, Science and Literature, adapted to Rural Life. By Rev. John L. Blake, D. D. BOUSSmGATTLT'S (J. B.) RTJRAIi ECONOMY, 1 25 Or, Chemistry Applied to Agriculture ; presenting Distinctly and in a Simple Manner the Principles of Farm Management, the Preservation and Use of Manures, the Nutrition and Food of Animals^ and the General Economy of Agriculture. The work is the fruit of a long life (rf study and experiment, and its perusal will aid tba farmer greatly in obtaining a practical and scientific knowledge of his profession. BROWNE'S AMERICAN BIRD FANCIER, - 25 The Breeding, Rearing, Feeding, Management and Peculi- arities of Cage and House Birds. Illustrated with engravings. BROWNE'S AMERICAN POTTLTRT YARD, 1 00 Comprising the Origin, History and Description op the Different Breeds of Domestic Poultry, with Complete Directions for their Breeding, Crossing, Rearing, Fattening and Preparation for Market ; including specific directions for Caponizing Fowls, and for the Treatment of the Principal Diseases to whifch they are subject, drawn from authentic sources and personal observation* Illustrated with numerous engravings. BROWNE'S (D. JAY) FIELD BOOK OF MANURES, - - - - 1 25 Or, American Muck Book ; Treating of the Nature, Properties, Sources, History and Operations of all the Principal Fertilizers and Manures in Common Use, with specific directions for their Preservation and Application to the Soil and to Crops ; drawn from authentic sources, actual experience and personal observation, as combined with the Leading Principles of Practical and Scientific Agriculture. BRIDGEMAN'S (THOS.) YOTJNG GARDENER'S ASSISTANT, - - 1 60 In Three Parts j Containing Catalogues of Garden and Flower Seed, with Practical Directions under each head for the Cultivation of Cu nary Vege- tables, Flowers, Fruit Trees, the Grape Vine, &c. ; to which is added a Calendar to each part^howing the work necessary to be done in the various departments each month of the year. One volume octavo. BRIDGEMAN'S KITCHEN GARDENER'S INSTRUCTOR, M Cloth, 50 " " •' ** Cloth, 60 Books published by A. 0. Moore & Co. t BBIDGEMAW'S FLOEIST'S GUIDE, % Cloth, 60 " " " Cloth, 60 BEIDGEMAN'S FRUIT CULTIVATOR'S MAITUAL, - - K Cloth, 60 " *' '* " - . Cloth, 60 BRECK'S BOOK OF FLOWERS, 1 00 In which are Dbscribed all the Various Hardy Herbaceous Perennials, Annuals, Shrubs, Plants and Evergreen Trees, with Directions for their Cultivation. BUIST'S (ROBERT) AMERICAH FLOWER GARDEIT DIRECTORY, 1 25 Containing Practical Directions for the Culture op Plants, in the Flower Garden, Hothouse, Greenhouse, Rooms or Parlor Windows, for every month in the Year ; with a Description of the Plants most desirable in each, the nature of the Soil and situation best adapted to their Growth, the Proper Season for Trans- planting, &;c. : with Instructions for erecting a Hothouse, Greenfaonee, and Laying out a Flower Garden ; the whole adapted to either Large or Small Gardens, with Instruc- tions for Preparing the Soil, Propagating, Planting, Pruning, Training and Fruiting the Grape Vine. BUIST'S (ROBERT) FAMILY KITCHEK GARDENER, . - - 76 Containing Plain and Accurate Descriptions of all the Different Species and Varieties of Culinary Vegetables, with their Botanical, English, French and German names, alphabetically arranged, with the Best Mode of Cultivat- ing them in the Garden or under Glass ; also Descriptions and Character of the most Select Fruits, theu- Management, Propagation, &c. By Robert Buist, author of the *'American Flower Garden Directory," &c. OKIKESE SUGAR CANE AND SUGAR-MAKING, .... 25 Its History, Culture and Adaptation to the Soil, Climate, and Economy of the United States, with an Account of Various Processes of Manu- facturing Sugar. Drawn from authentic sources, by Chables F. Siassbdey, A. M., late Commissioner at the Exhibition of all Nations at London. CHORLTON'S GRAPE-GROWER'S GUIDE, 60 Intended Especially for the American Climate. Being a Practical Treatise on the Cultivation of the Grape Vine ia each department of Hot- house, Cold Grapery, Retarding House and Out-door Culture. With Plans for the coh- Btructiou of the Requisite Buildmgs, and giving the best methods for Heaiing the same. Every department being fully illustrated. By Wiluah Chorltok. eOBBETrS AMERICAN GARDENER, 60 A Treatise on the Situation, Soil and Lating-out of Gardens, find the Jfaking and ilauaging of Hotbeds and Greenhouses, and on the Propagation and Cultivation of the several sorts of Vegetables, Herbs, Fruits and Flowers. COTTAGE AND FARM BEE-KEEPER, 60 A Practical Work, by a Country Curate. COLE'S AMERICAN FRUIT BOOK, 60 Containing Directions for Raising, Propagating and Manag- ing Fruit Trees, Shrubs and Plants ; with a Description of the Best Varieties of Fruit, inoluiling New and Valuable Kinds. -^ COLE'S AMERICAN VETERINARIAN, 60 Containing Diseases op Domestic Animals, their Causes, Symp- toms and Remedies ; with Rules for Restoring and Preserving Health by good manage- ment ; also for Training and Breeding. SADD'S AMERICAN CATTLE DOCTOR, ------- 1 00 Containing the Necessary Information for Preserving the Health and Caring the Diseases of Oxen, Cows, Sheep and Swine, with a Groat Variety of Original Recipes and Valuable Information in reference to Farm and Dairy Manage- ment, whereby every Man can be his own Cattle Doctor. The principles taught in this work are, that all Medication shall be subservient to Nature — that all Medicines must be sanative in their operation, and administered with a view of aiding the vital powers, instead of depressing, as heretofore, with the lancet or by poison. By G. H. Dadd, M. D., Veterinary practitioner. 4 Books published by A. O. Mooee & Co. DADD'S MODERN HORSE DOCTOR, 1 00 An American Book for American Farmers ; Containing Practi- eal Observations on th.e Causes, Nature and Troatment of Disease and Ijanjeness of Horses, embracing the Most Recent and Approved Methods, according to an enlightened system of Veterinary PracticCj for the Preservation and Restoration of Health, With iUustrations. DADD'S ANATOMY AND PHYSIOLO&Y OF THE HORSE, Plain, - 3 00 " " ~" *' *' Colored Plates, 4 00 With Anatomical and QuESTioNAi Illustrations; Containing, also, a Series of Examinations on Equine Anatomy and Philosophy, with Instructions in reference to Dissection and the mode of malting Anatomical Preparations ; to which is added a Glossary of Veterinary Technicalities, Toxicological Chart, and Dictionary of Veterinary Science. DANA'S MTJGK MANUAL, FOR THE USE OF FARMERS, - - 1 00 A Treatise on the Physical and Chemical Properties of Soils and Chemistry of Manures ; including, also, the subject of Composts, Artificial Manures and Irrigation. A new edition,, with a Chapter on Bones and Superphosphates. DANA'S PRIZE ESSAY ON MANURES, 26 Submitted to the Trustees op the Massachusetts Society for Promoting Agriculture, for their Premium. By Samiiel H. Dana. D(HttESTIC AND ORNAMENTAL POULTRY, Plain Plates, . . . 1 00 " " " Colored Plates, - - 2 00 A Treatise on the History and Management of Ornamental and Domestic Poultry. By Rev. Edmcnp Saul Dixos, A. M.,with large additions by J. J. Kerr, M. D. Illustrated with sixty -five Original Portraits, engraved expressly for this wofk. Fourth edition, revised. DOWNING'S (A. J.) LANDSCAPE GARDENING, 3 50 Bevised, Enlarged and Newly Illustrated, by Henry Win- throp Sargent. This Great Work, which has accomplished so much in elevating the American Taste for Rural Improvements, is now rendered doubly interesting and valuable by the experience of all the Prominent Cultivators of Ornamental Trees in the United States, and by the descriptions of American Places, Private Residences, Central Park, New York, Llewellyn Park, New Jersey, and a full account of the Newer Decidu- ous and Evergreen Trees and Shrubs. The illustrations of this edition consist of seoen swperb sted pUUe engravings, by Smilub, Hinshelwood, DinHns and others ; besides one hundred engravings on vjood cund stone, of the best American Residences and Parks, with Portraits of many New or Remarkable Trees and Shrubs. DOWNING'S (A. J.) RURAL ESSAYS, 3 00 On Horticulture, Landscape Gardening, Rural Arohiteoturb, Trees, Agriculture, Fruit, with his Letters from England. Edited, with a Memoir of the Author, by George Wm. Curtis, and a Letter to hisFriends, by Frederika Bremer^ and an elegant Steel Portrait of the Author. EASTWOOD (B.) ON THE CULTIVATION OF THE CKANBERBY, 50 With a DEacRiPTiox of the Best Varieties. By B. Eastwoob, *' Septimus," of the New York Tribune. Illustrated. ELLIOTT'S WESTERN FRUIT BOOK, - , - . , - 1 25 A N"ew Edition op this Work, Thoroughly Bevised. Em- bracing all the New and Valiiablo Fruits, with the Latest Improvements in their Cultiva- tion, up to January, 1S53. especially ailaptod to the wants of Western Fruit Growers ■ fall of excellent illustrations. Uv F. R. Eijjott, Pomologist, late of Cleveland Ohio now' of St. Louis. ~ ' EVERY LADY HER OWN FLOWER GARDENER, - - . 50 Addressed to the Industrious and Economical only ; containing' simple and practical Directions for Cultivating Plants and Flowers ; also, HiiTts for tha Management of Flowers in Rooms, with brief Botanical Descriptions of Plants and Flowers. Xlie lyl^olo in plain and sin\ple language. By I/icl*a .Jornsox, Mooks 2jub!i3/ied by \. O. MooiiE & Co. 5 TABM DRAINAGE, 1 00 The Principles, Pkocesses and Effects op Draining Land, with Stoaesj Wood, Draiu-plows, Open Ditches, and. especially with Tiles; including Tables of Rainfall, Evaporation. Filtrati:on, Excavation, capacity of Pipes, cost and num- ber to ths acre. With more than 100 illustrations. By the Hon. Henry F, li'RENcn, of New Hampshire. IXSSENDEN'S (T. G.) AMERICAN KITCHEN GARDENER, - - 50 Containing Directions for the Cultivation op Vegetables and Garden Fruits. Cloth. FESSENDEN'S COMPLETE FARMER AND AMERICAN GARDENER, 1 25 RuRAii Economist and New American Gardener ; Containing a Compendious Epitome of the most Important Branches of Agriculture and Rural Economy ; with Practical Directions on the Cultivation of Fruits and Vegetables, includ- ing Landscape and Ornamental Gardening. By Tuomj>s G. Fisssenden. 2 vols, in 1. FIELD'S PEAR CULTURE, - 1 00 The Pear Garden ; or, a Treatise on the Propagation and Cultivation of the Pear Tree, with Instructions for its Management from the Seedling to the Bearing Tree. By 'Eaoius W. Field. FISH CULTURE, 100 A Treatise on the Artificial Propagation of Fish, and the Construction of Ponds, with the Description and Habits of such kinds of Fish as are most suitable for Pisciculture. By Theodatus G^ruck, M. D., Vice-President of the Cleveland Academy of Nat. Science. FLINT ON GRASSES, - - - - 1 25 A Practical Treatise on Grasses and Forage Plants ; Com- prising their Natural History, Comparative Nutritive Value, Methods of Cultivation, Cut- ting, Curing and the Management of Grass Lands. By Charues L. Flint, A. M., Secre- tary of the Mass. State ]3oard of Agriculture. GUENON ON MILCH COWS, 60 A Treatise on Milch Cows, whereby the Quality and Quantity of Milk vrhich any Cow will give may bo accurately determined by observing Natural Marks or External Indications alone ; the length of time she will continue to give Milk, &c., &c. By M. FRAwcia Guenon, of Libourne, France. Translated by Nicholas P. Trist, Efeq. ; with Introduction, Remarks and Observations on the Cow and the Dairy, by John S. SKnraEa.. Illustrated with numerous Engravings. Neatly done up in paper covers, 37 cts. HERBERT'S HINTS TO HORSE-KEEPERS, 1 25 Complete Manual for Horsemen ; Embracing : How TO Breed a House. How to Physio a Horse. How TO But a Horse. (Allopathy and Homoeopatht. How TO Break a Hobsb. How to Groom a Horse. How to Use a Horse. How to Drive a Horse. How to Feed a Horse. How to Ride a Horse. And Chp,pter8 on Mules and Ponies. By the late Henry Wiluam Herbert (Frank Forrester) ■ mth additions, including Rarey's Method of Horse TAMiNa, and Baucher's System op Horsemanship ; also, giving directions for the Selection and Care of Carriages and Harness of every description, from the City " Turn Out" to the Farmer's " Gear," and a- Biography of the eccototric Author. lUusirated throughotU. HOOPER'S DOa AND GUN, - - - - 50 A Few Loose Chapters on Shooting, among wliicli will be found soms Anecdotes and Incidents ; also Instructions for Dog Breaking, and interest- ing letters from Sportsmen. By A Bad Shot. HYDE'S CHINESE STTGAR CANE, 25 Containing its Histort, Mode of Culture, Manufacture op the Sugar, &c. ; with Reports of its success in different parts of the United States. 6 Booha published by A. O. Moore & Co. JOHKSTON'S (JAMES F. W.) AGRICTJLTUEAL CHEMISTRY, - 1 25 Lectures on the Application of Chemistry and Geology to Agriculture. New Edition, with an Appendix, containing the Author's Experiments in Practical Agriculture. JOHNSTON'S (J. F. W.) ELEMiafTS OF AGRICTTLTTJRAI CHEM- ISTRY AND GEOLOGY, 1 00 With a Complete Analytical and Alphabetical Indes, and an American Preface. By Hon. SnroN Brown, Editor of the " New England Farmer." JOHNSTON'S (J. F. W.) CATECHISM OF AGRICTTLTURAL CHEM- ISTRY AND GEOLOGY, 25 By James F. W. Johnston, Honorary Member of the Royal Agricultural Society of England, and author of "Lectures on Agricultural Chemistry and Geology." With an Introduction by Joh:^ Pttkin Norton, M. A., late Professor of Scientific Agriculture in Yale College. With Notes and Additions by the Author, pre- pared expressly for this edition, and an Appendix compiled by the Superintendent of Education in Nova Scotia. Adapted to the use of Schools. LANGSTROTH (REV. L. L.) ON THE HIVE AND HONEY BEE, - 1 25 A Practical Treatise on the Hive and Honey Bee, Third edition, enlarged and iUtislrated with numerous engravings. This Work is, without a doubt, the best work on the Bee published in any language, whether we" consider its scientific accuracy, the practical instructions it contains, or the beauty and completeness of its illustrations. LEUCHARS' HOW TO BTTILD AND VENTHiATE HOTHOUSES, - 1 25 A Practical Treatise on the Construction, Heating and Ventilation of Hothouses, including Conservatories, Greenhouses, Graperies and other kinds of Horticultural Structures ; with Practical Directions for their Management, in regard to Light, Heat and Air. Illustrated with numerous engravings. By P. B. Lbuchars, Garden Architect. UEBIG'S (JUSTUS) FAMILIAR LECTURES ON CHEMISTRY, - 60 And its relation to Commerce, Physiology, and Agriculture. Edited by John Gardener, M. D., ' LINSLEY'S MORGAN HORSES, 1 00 A Premium Essay on the Origin, History, anb Characteristics of this remarkable American Breed of Horses J tracing the Pedigree from the original Justin Morgan, through the most noted of hiB progeny, down to the present time. With numerous portraits. To which are added Hints for Breeding, Breaking and Gene- ral Use and Management of Horses, with practical Directions for Traming them for Exhibition at Agricultural Fairs. By D. C. Ijnsley, Editor of the American Stock Journal. MOORE'S RURAL HAND BOOKS, 1 25 First Series, containing Treatises on — TnE Horse, The Pests of the Farm, The Hog, Domesho Fowia, and Tmc HoNET Bee, The Cow. Second Series, containing — _ . . 1 25 EVIHT IiADT HER OWN FLOWEB GARDENER, ESSAT ON MANURES, Etjmenis op Agriculture, American KrrcHBN Gardener, Bird FancieRj American Kose Culturist. Third Series, containing — - - - , 1 25 Mjles on THE Horse's Foot, Yine-Dresser's Maitual, Tbe Rabbit Fancier, Bee-Keeper's Chart, Weeks on Bees, Chemistry Made Easy. Fourth Series, containing — - . . 1 25 Pebrsoz on the Vine, Hooper's Dog and Gun, LiEBiG'a Famujar Letters, Shuxful Housewiff, BROWNB'a Memoirs op Indi *n Corn. Books 2n{hlished by A. O. Moore & Co. 7 HDTEE'S- BEE-KEEPER'S MANUAL, 1 00 Being a Practical Treatise on the History and Domestic Economy of tho Honey Bee, embracing a Full Illustration of the whole subject, with the Jlost Approved Methods of Managing this Insect, through every branch of its Culture ; the result of many years' experience. Illustrated with many engravings By T. B. Miner. HUES OK THE HORSE'S FOOT AIH) HOW TO KEEP IT SOUKB, 50 With Cuts, Illustrating the Anatomy op the Foot, and contain- ing valuable Hints on Shoeing and Stable Management, in Health and m Disease. By Wm. Miles. HUBTJRN ON THE COW AND DAIRY HUSBANBRT, - - - 25 By M. M. MiLBURN, and revised by H. D. Richardson and Ambrose Stevens. With illustrations. MTTNN'S (B.) PRACTICAL LAND DRAINER, 60 Being a Treatise on Draining Land, in which the Most Ap- proved Systems of Drainage are Explained, and their Differences and Comparative Merits Discussed ■ vith faU Directions for tho Cutting and Making of Drains, with Remarks upuu the various materials of which thoy may be constructed. With many illustrations. By B. Mukn, Landscape Gardener. NASH'S (J. A.) PROGRESSIVE FARMER, 60 A Scientific Treatise on Agricultural Chemistry, the Ge- ology of Agriculture, on Plants and Animals, Manures and Soils, applied to Practical Agriculture ; with a Catechism of Scientific and Practical Agriculture. By J. A. N.A8H. NEILL'S PRACTICAL FRUIT, FLOWER AND KITCHEN GARDEN- ER'S COMPANION, 1 00 With a Calendar. By Patrick Neill, Secretary of the Royal Caledonian Horticultural Society. Adapted to the United States from the fourth edition, revised and improved by the Author, Edited by G. Embhsow, M. D., Editor of " The American Farmer's Encyclopedia." With Notes and Additions by R. G. Pjuedes, author of " Manual of the Strawberry Culture." With illustrations. NORTON'S (JOHN P.) ELEMENTS OF SCIENTIFIC AGRICULTURE, 60 Or, the Connection between Science and th-e Art op Practical Farming, Prize Essay of the New York State Agricultural Society. By John P. Nor- ton, M. A., Professor of Scientific Agriculture in" Yale College. Adapted to the use of Schools, OLCOTT'S SORGHO AlO) IMPHEE, THE CHINESE AND AFRICAN SUGAR CANES, 1 00 A Complete Treatise upon their Origin and Varieties, Culture and Uses, tbeir value as a Forage Crop, and Directions for making Sugar, Molasses, Alcohol, Sparkling and Still Wines, Beer, Cider, Vinegar, Paper, Starch and Dye Stuffs. Fully illustrated with Drawings of Approved Machinery ; with an Appendix by Leonard Wbay, of Cafli-aria, and a Description of his Patented Process of Crystallizing the Juice of the Imphee ; with the Latest American Experiments. By Henry S. Olcott. PARDEE (R. G.) ON STRAWBERRY CULTURE, 60 A Complete Manual for the Cultivation of the Strawberry j with a Description of the Best Varieties. Also notices of the Raspberry, Blackberry, Currant, Gooseberry and Grape ; with Directions for their Cultivation, and the Selection of the Best Varieties. " Every process here recommended has been proved, the plans of others tried, and the result is here given." With a Valuable Appendix, containing the observations and experience of some of the most successful cultivators of these fruits in our country. PEDDERS' (JAMES) FARMERS' LAND MEASURER, - - - - 60 Or Pocket Companion ; Showing at one view the Contents of any Piece of Land, from Dimensioa'S taken in Yards. Wi^th a Set of Useful Agricultural 8- Hooks ^nihlisJied hy A. O. Mooee & Co. FKRSOZ' CnLTUEE OF THE VINE, - - 2S A New Pkogess pok the Odltukb op the Vine, by Persoz, Pro- fessor of the Faculty of Sciances of Strasbourg ; Directing Professor of the School of Phar- macy of the same city. Translated by J- O'O. Barclay, Surgeon U. S. N. PHEIPS' BEE KEEPER'S CHABT, 25 Being a Bkibp Pkactical Treatise on the Instinct, Habits and Management of the Honey Boe, in all its various branches, the result of many years' practical experience, whereby the author has been enabled to divest the subject of much that has been considered mysterious and difficult to overcome, and render it more sure, profitable and interesting to every one, than it has heretofore been. By E, ■W. Pheus. Q.XmiBY'S MYSTERIES OF BEE-KEEPING EXPLAINED, - - 1 00 Being a Complete Analysis op the Whole Subject, Consisting of the Natural History of Bees ; Directions for obtaining" the Greatest Amount of Pui-e Surplus Honey with the least possible expense ; Remedies for Losses Given, and the Scienceof Luck fully illustrated ; the result of more than twenty years' experience in extensive Apiaries. By M. Quinby. RANDALL'S (H. S.) SHEEP HITSBANDRT, - - - - ' - - 1 25 With an Account op the Different Breeds, and general direc- tions in regard to Summer and Winter Management, Breeding and the Treatment of Diseases, with Portraits and other engravings. By Hesky S. Rakdall. BEEMELIN'S (CHAS.) VINE DRESSER'S MANUAL, ... 50 An Illustrated Treatise on Vineyards and Wine-Making, containing full Instructions as to Location and Soil, Preparation of Ground, Selection and Propagation of Vines, the Treatment of Young Vineyards, Trimming and Training the Vines, Manures and the Making of Wine. RICHARDSON ON HOGS, 25 Theik Origin, Varieties and Management, with a View to Profit and Treatment under Disease ; also, plain Directions relative to the Most Approved Modes of Preserving their Flesh. By H. D. Richardso.v, author of " The Hive and the Honey Boo," &c., &c. With Illustrations. RICHARDSON ON THE HIVE AND THE HONEY BEE, ... 25 With Plain Directions for Obtaining a Considerable Annual Income from this branch of Kural Economy ; also, an Account of the Diseases of Bees and their Remedies, and Remarks as to their Enemies, and the best mode of protecting the Hives from their attacks. By H. D. Bichaedso.v. With illustrations. RICHARDSON ON DOMESTIC FOWLS, 25 Their Natural History, Breeding, Bearing, and General Management. By H. D. Eictiardsoh. With illustrations. RICHARDSON ON THE HORSE, 25 Their Origin and Varieties ; with Plain Directions as to the Breeding, Rearing and General Management, with Instructions as to the Treatmo:it of Disease. Handsomely illustrated. By H. D. Ric[iARDSo>f. RICHARDSON ON THE PESTS OF THE FARM, .... 25 With Instructions for their Extirpation ; being a Manual of Plain Directions for the Certiiiu Destruction of every description of Vermin. With numerous illustrations on Wood. RICHARDSON ON DOGS ; THEIR ORIGIN AND VARIETIES, - 60 Directions as to their General Management. With numerous Original Anecdotes. Also, Complete Instructions as to Treatment under Disease. By H. D. RicnARDSox. Illustrated with numerous wood engravings. This is not only a cheap, but one of the best worlis ever published on the Dog. SCHENCK'S GARDENER'S TEXT BOOK, 60 Containing Directions for the Formation and Management of thn Kitchen Garden, the Culture and r.^io of Vegetables, Fruits and Medicinal Horh«. Boohs published by A. O. Moobe & Co. 9 SHEPHERD'S OWN BOOK, 2 00 With an AcconNi op the Different Breeds, Diseases and Man- agement of Sheep, and General Directions in regard to Summer and Winter Management, Breeding and tlie Treatment of Diseases ; with illustrative engravings by Yooatt & Randall ; embracing Skinner's Notes on the Breed and Management of Sheep in the United States, and on the Culture of Fine Wool. STEWABT'S STABLE BOOK, 1 00 A Treatise on the Management op Horses, in Relation to stabling, Grooming, Feeding, Watering and Working, Construction of Stables, Ventila- tion, Appendages of Stables, Management of the Feet, and of Diseased and Defective Horses. By JoHX Stewart, veterinary Surgeon. With Notes and Additions, -adapting it to American Food and Climate. By A. B. Allen, Editor of the American Agriculturist. STRAY LEAVES FROM THE BOOK OF NATURE, - - - - 1 00 By M. Sohele De Yere, of the University op Virginia. Contexts : I. Only a Pebble. n. Nature lv Motion. ni. The Ocean and rra Lite. IV. A Chat about Plants. V. Younger Years op a Plant, VI. Later Years of a Plant. yn. Plant Mummies. vm. Unknown Tongues. IX. A Trip to the Moon. STEPHENS' (HENRY) BOOK OF THE FARM, 4 00 A Complete Gdide to the Pakmbk, Steward, Plowman, Cattle- man,Shepherd, Field Worker and Dairy Maid. By Henry Stephens. With Four Hun- dred and Fifty illustrations ; to which are added Explanatory Not£S, Remarks, &c., by J. S. Skinner. Really one of the best books a farmer can possess. SKULFUL HOUSEWIFE, 50 Or Complete Guide to Domestic Cookery, Taste, Comfort, and Economy, embracing 659 Recipes pertaining to Household Duties, the Care of Health, Gardening, Birds, Education of Children, &c.,&c. By Mrs. L. G. Abell. SKINNER'S ELEMENTS OF AGRICULTURE, 25 -Adapted to the Use of American Farmers. By F. G. Skinner. SMITH'S (C. H. J.) LANDSCAPE GARDENING, PARKS AND PLEASURE GROXTNDS, 1 25 With Peaotical Notes on Country Residences, Villas, Public Parks and Gardens. By Charles H. J. SsirrH, Landscape Gardener and Garden Archi tect. With Notes and Additions by Lewis F. Allen, author of " Rural Architecture." THAER'S (ALBERT D.) AGRICULTURE, 2 00 The Principles of Agriculture, by Albert D. Thaer ; Trans- lated by WlLUAM Shaw and Cuthbeet W. Johnson, Esq., F. R. S. With a Memoir of the Author. 1 vol. 8vo. This work is regarded, by those who are competent to judge, as one of the most valuable works that has ever appeared on the subject of Agriculture. At the same time that it is eminently practical, it is philosophical, and, even to the general reader, re- markably entertaining. THOMAS' (J. J.) FARM IMPLEMENTS, 100 And the Pkinciplbs of their Construction and Use ; an Ele raentary and familiar Treatise on Mechanics and Natural Philosophy, as applied to the ordinary practices of Agriculture. With 200 illustrations. THOMPSON (R. D.) ON THE FOOD OF ANIMALS, - - - 75 Experimental Researches on the Food of Animals and the Fattening of Cattle : with Remarks on the Food of Man . Based upon Experiments under- taken by order of the British Government, by RonivRT Dl-ndas Thompson. M. D., Lecturer on Practical Chemistry, University of Glasgow. 10 Books published by A. O. Moore & Co." THE ROSE UULTUKIST, 50 Beinq a Pkactical Treatise on the Peopagation, Cultivation, and Management of the Rose in all seasons ; with a List of Choice and Approved Varie- ties, adapted to tho Climate of the United States ; to which is added full directions for the Treatment of the Dahlia. Illustrated by engravings. TOPHAM'S CHEMISTET MADE EAST, 25 For the Use of Farmers. By J. Topham, TUENER'S COTTON PLAITTER'S MANUAL, 1 00 Being a Compilation of Facts from the Best Authorities on the Culture of Cotton, its Natural History, Chemical Analysis, Trade and Consumption, and embracing a History of Cotton and the Cotton Gin. By J. A. Turner. WAEDER'S (J. A.) HEDGES AND EVERGREENS, - - - - 1 00 A Complete Manual for the Cultivation, Pruning and Man- agement of all Plants suitable for American Hedging, especially the Madura or Osage OraDge. Fully illustrated with engravings of plants, implements and processes. To which is added a Treatise on EoergreenSj their different Varieties, their propagation, transplanting and Culture in the United States. TARING'S ELEMENTS OF AGRICTTLTTTRE, 75 A Book for Young Farmers, with Questions foe the use of Schools. WEEKS (JOHN M.) ON BEES-A MANTTAL, 60 Or, an Easy Method of Managing Bees in the most profit- able manner to their Owner ; with Infallible Rules to Prevent their Destruction by the Moth. With an Appendix, by Wooster A. Flanders. ■WHITE'S ("W. N.) GARDENING FOR THE SOTTTH, - - - - .1 25 Or, the Kitchen and Fruit G-arden, with the Best Methods for their Cultivation ; together with Hints upon Landscape and Flower Gardening ■ con- taining Modes of Culture and Descriptions of the Species and Varieties of the Culinary Vegetables, Fruit Trees and Fruits, and a Select List of Ornamental Trees and Plants, Adapted to tho States of the Union South of Penusylvania, with Gardening Calendar.s for the same. By War. N. White, of Athens, Georgia. YOTJATT AND MARTIN ON CATTLE, 1 25 Being a Treatise on their Breeds, Management, and Diseases, comprising a Full History of the Various Races ; their Origin, Breeding and Merits ; their capacity for Beef and Milk. By W. Youatt and W. C. L. Martin. The whole form- ing a Complete Guide for the Farmer, the Amateur and the Veterinary Surgeon, with 100 illustrations. Edited by Ambrose Ste\'ENS. YOTTATT ON THE HORSE, 1 25 TOUATT ON THE STRUCTURE AND DISEASES OF THE HoRSE, With their Remedies ; also, rractical Rules for Buyers, Breeders, Smiths, &c. Edited by W. C. Spooner, M.R.C.V.S. With an Account of tho Breeds in the United States, by Henry S. Raxdaix. YOTTATT ON SHEEP, 75 Their Breed, Management and Diseases, with Xllustrative En- gravings ; to which arc added Remarks on the Breeds and Management of Sheep in the United States, and on tho Culture of Fine Wool in Silesia. By Wii. Youaxt. YOTTATT AND MARTIN ON THE HOG, 75 A Treatise ox the Breeds, Management, and Medical Tebat- raent of Swine, with Directions for Salting Pork and Curing Bacon and Hams. By Wm. YouATr, V. S.,and W. C. L. MARTiy. Edited by Ambeose Stbvens. Illustrated with engravings drawn from life. Books published by A. 0. Mooke & Co. 11 Moore's Hand Books of Rural and Domestic Economy. ALL AEBANQED AND ADAPTED TO THE USE OF AMERICAN PAEMEES. Pice 35 Cents Each. HOGS, Their Oeiqin, Varieties and Management, with a View to Pro- fit and Treatment under Disease ; also. Plain Directions relative to tlio Most Approved Modes of Preserving their Flesh. By H. D. Richaedson. With illustrations TBjB hive Mm TH£ HOKET BEE, With Plain Directions fob Obtaining a Considerable Annual Income from this branch of Rural Economy ; also, an Account of the Diseases of Beea and their Remedies, and Remarks as to their Enemies, and the best mode of protecting the Hives from their attacks. By H. D. RicaABDSON. With illustrations. DOMESTIC FOWlS, Their Natural History, Breeding, Rearing and General Management. By H. D. Richardson. With illustrations. the hobse, Their Origin and Varieties ; with Plain Dieeotigns as to the Breedmg, Rearing and General Management ; with instructions as to the Treatment of Disease Handsomely illustrated. By H. D. Richabdson. THE BOSE, The American Rose Cultueist ; being a Practical Treatise on the Propagation, Cultivation and Management in all Seasons, &c. ; with fall directions for the treatment of the Dahlia. THE FESTS OF THE EABK, With Insteuctions for their Extirpation ; being a Manual of Plain Directions for the Certain Destruction of every description of Vermin. With numerous illustrations on wood. AN ESSAY ON MAiroaES, Submitted to the Trustees op the Massachusetts Society for Promoting Agriculture, for their Premium. By Samuel H. Dana. THE AMEKICAN BIBD FANCIEB, Considered with Reference to the Breeding, Rearing, Peed- ing, Management and Peculiarities of Cage and. House Birds. Illustrated with Engrav- ings . By D. Jay Browne. CHEmSIRY lUASE EAST, For the Use op Farmers. By J. Tofham. ELEUENTS OF AGmOULTTIBE, Translated prom the French, and Adapted to the use of American Farmers. By F. G. Skinner. THE HOBSE'S FOOT, AND HOW TO KEEP IT SOTJND, With Cuts, illustrating the Anatomy of the Foot, and containing valuable Hints on Shoeing and Stable Management, both in Health and Disease. By Wst. Miles. * THE SKILLFUl HOUSEWIFE, Or, Complete Guide to Domestic Cookery, Taste, Comport and Economy, embracing 659 Recipes pertaining to Household Duties, the Care of Health, Gardening, Birds, Education of Children, &c. , &c. By Mrs. L. G. Abell. THE tJSSSSaHS HIXCHEN GABDENEB, Containing Directions for the Cultivation op Vegetables and Garden Fruits. By T. G. Fessbnden. 12 JBoohs jmblished by A. O. Moobe & Co» CHINESE SUGAR CAlfE AND SUGAR-MAKING, Its History, Culture and Adaptation to the Soil, Climate and Economy of the United States, with an Account of Various Processes of Manufactur- ing Sugar. Drawn from authentic sourcos by Qlarlss Fi Stansbueyj A. M., late Com- missioner at the Exhibition of all Nations at London. PERSOZ' CULTURE OF THE VINE, A New Process for the Culture of the Vine, by Persoz, Pro- fessor of the Faculty of Sciences of Strasbourg ; Directing Professor of tlie School of Pharmacy of the same city. Translated by J. O'C. B^RCLAy, Surgeon^ U. S. N. THE BEE-KEEPEE'S CHART, Being a Brief, Practical Treatise on The Instinct, Habits and Management of the Honey Bee, in all its various braucbes, the result of many years' practical experience, whereby the author has been enabled to divest the subject of much that has been considered mysterious and difficult to overcome, and render it more sure, profitable and interesting to every one, than it has heretofore been. By E. W. Phelps. £VERY LADY HER OWN GARDENER, Addressed to the Industrious and Economical only; containing Simple and Practical Directions for Cultivating Plants and Flowers ; also, Hints for the Management of Flowers in Rooms, with Brief Botauical Descriptions of Plants and Flowers. The whole in Plain and simple language. By Louisa Johxson. THE COW; DAIRY HUSBANDRY AND CATTLE BREEDING, By M. M. Milburn, and Be vised by H. D. Richabdson and Amurosb Steve-vs. With illustrations. WILSON ON THE CULTURE OF ELAX, Its Treatment, Agricultural and Technical ; delivered before the Now York State Agricultural Society, at the Annual Fair at Saratoga, in September last, by JoHx "WiiaoN, late President of the Royal Agricifltural College -at Cirencester England. WEEKS ON BEES ; A MANUAL, Or, an Easy Method of Managing Bees in the most profitable manner to their owner, with Infallible Rules to Prevent their Destruction by the Moth ; with an Appendix by AVooster A. Flaitoehs. REEMELIN'S (CHAS.) VINE DRESSERS' MANUAL, Containing full Instructions as to Location and Soil ; Prepara-, tion of Ground ; Selection and Propagation of Vines ; The Treatment of a Young Vine- yard ; Trimming and Ti-aining the Vines ; Manures and the Making of Wine. Every department illustrated. HYDE'S CHINESE SUGAR CANE, Containing its History, Mode of Culture, Manufacture of the Sugar, &c. ; with Reports of its success in different parts of the United States. BEMENT'S (C. M.) RABBIT FANCIER, A Treatise on the Breeding, Bearing, Feeding, and General Management of Rabbits, with Remarks upon their Diseases and Remedies; to which are added Fnll Directions for the Construction of Hutches, Rabbitries, &c. , together with Recipes for cooking and dressing for the table. RICHARDSON ON DOGS; THEIR ORIGIN AND VARlETrES, Directions as to their General Management. With numerous Original Anecdotes ; also, Conjplete Instructions as to Treatment under Disease. By H D. RicnARDSO-v. Illustrated with numerous wood engravings. This is not only a cheap, but one of the best wortos ever published on the Dog. LIEBIG'S (JUSTUS) FAMILIAR LETTERS ON CHEMISTRY, And its Belation to Commerce, Thysiology, and Agriculture: Edited b}"" Jon.v (Jardbxek, M. D. THE DOG AND GUN, A Few Loose Chapters on Shooting, among which will be found some Anecdotes and Incidents ; also, Instructions for Dog Breaking, and interesiiDg let' tors from Sportsmen. By A R.iD Shot. :f 'SHHHHRH