ilili: li ! iiiiiiiliiili hi III UCSB LIBRARY THE MODERN MECHANIC: SCIENTIFIC GUIDE AND CALCULATOR COMPRISING RULES AND TABLES IN THE VARIOUS DEPARTMENTS OF MECHANICAL SKILL AND LABOR BY WILLIAM GRIER, CIVIL ENGINEER. How have we obtained this great superiority over th?se poor savages? Becans* Science has been at work, for many centuries, to diminish th amount of our mental labor, by teaching us the easiest mode of calculation. RESULTS or MACHINERY BOSTON: HIGGINS, BRADLEY AND DAYTON, 20 WASHINGTON STREET. CONTENTS. Air pump 222 Air vessel 228 Animal strength 273 Arithmetic 17 Artificers' work 108 Barometer 218 Beam, working to form 157 Bramah's press 180 Catenary 99 Collision 118 Conic sections 92 Contraction, marks of 39 Cotton spinning 290 Cube root, extraction of 35 Cycloid 98 Drawing instruments 80 Drawing, mechanical 86 Eccentric 259 Ellipse 9497 Floating bodies 1 82 Ply wheel 260 Forces, central 146 Forces, parallelogram of. 119 Forcing pump 227 Fractions, decimal 22 Fractions, vulgar 17 Friction 275 Geometry 57 Governor .' 1-18 ( J ravity, centre of 134 Gravity, specific 182 Gyration, centre of. 142 Heat 238 Heights, measurement of 219 Horses power 2o t Hyd/odjh arnica 195 Hydrostatics , 1 75 Hyperbola 9(597 Inclined plane, the 132 Joists 163 Journals 162 Lever, the 121 Lifting pump 226 Machines 278 Materials, strength of 148 Materials, weight of 1 88 Measures and weights 51 Mechanics 115 Mensuration 100 Mill-weight's table 212 Motion, accelerated 117 Motion, uniform 116 Numbers, compound 26 Oscillation, centre of 137 Parabola 94 97 Parallel motion 261 Pendulum 137 Percussion, centre of 141 Pipes, contents of. 224 Pneumatics 216 Position 48 Powers, mechanical 121 Powers and roots 33 Progressions 44 Proportion, compound 43 Proportion, simple 41 Pulley, the 130 Pumps 22 1 Railways 266 Rotation 142 Screw, the 133 Sector, the 83 Shafts 159 sliding rule 36 S juare ro'>t. extr.u-tt'jii of. ... 33 Steam . . 243 CONTENTS. 1 Pg* Steam engine 248 Steam vessels 269 Suction pump 223 Syphon, the 220 Thermometer 238 Timber, measurement of 107 Water, motion of 195 Water, pressure of 1 75 Water wheels v 204 Wedge, the 133 Weights and measures 51 Weight of materials 188 Wheels 165 Wheel and axle 124 Wind 229 Windmill, horizontal 230 Windmill, vertical . . '. 233 TAB L ES. Alcohol, vapour of 247 Capacities for heat 241 Circular segments 1 03 Cohesion 150 Crushing 151 Drawing paper 56 Elasticity and strength of tim- ber 149 Gauge points 264 Gravities, specific 183 Heat, effects of 240 Iron plate 189 Iron rod 191 Iron, Swedisjj, weight of. .... 188 Iron, wrougk-t, weight of. .... 1 88 Lateral strength 151 Level, difference of. 209 Machines, power of 289 Metals, weight of. 189 190 Mechanical effect 288 Millwright's 212 Pipe, cast iron 191 Pipes, content of. 226 Pitch of wheels 168 Platonic bodies 1 05 Polygons 101 Proportions 47 Shaft journals 1 62 Specific heat 242 Steam, elasticity of. 245 246 Steam vessels 270 Traction, force of 269 Water, discharge of. . 199200 202203 Weight of materials 193 Weights and measures 51 Wheels 173 I Wheels, teeth of 175 Wind, force of 230 1 Windmill sails 234 INTRODUCTION. IT is our intention, in these introductory panes, to make a tew observations on the nature of scientific knowledge, which may be useful to the younj reader in enabling him to understand 'more clearly the subjects contained in the volume, and in guarding him against the adoption of false theory, or the wasting of his time in inquiries which can terminate in no useful result. Such intro- ductory observations are rendered the more necessary, as a correct knowledge of the subjects to which they relate, is the only sure foundation on which there can be raised a solid superstructure of science. It is a general opinion that scientific knowledge is entirely dif- ferent from all other kinds of knowledge ; or that it requires for its cultivation a constitution of mind only to be met with here and there in the great family of mankind ; and what is said of the poet is also thought of the philosopher th-.it lie is burn, not made. All men are certainly not equally endowed with capacities for the acquisition of scientific knowledge, but there are few men indeed who are totally unprivileged. The man who would relinquish scientific pursuits merely because he had no hope of reaching the eminence of a Newton, a Watt, or a Davy, is no better than him, who, in despair of ever obtaining a share of wealth equal to that of the rich inheritor of the land, would cease to make any honest exertion to raise himself from a state of the most squalid wretchedness. We would not be understood by this to bring the acquisition of knowledge into invidious comparison with the acquisition of wealth the one is in every case a godlike employ- ment, but the other is often the concomitant of vice. The young mechanic should be made well aware that the knowledge of the man of science differs from the knowledge of 1* 5 6 INTRODUCTION. ordinary men, not so much in kind as in degree ; and the know- ledge which guides the little boy in the erection of his summer- house, constitutes a part of that knowledge which guides the best architect in the erection of the most splendid edifice. The boy raises his paper kite in the air, with no other end in view save his own amusement he has learned to do so by seeing other boys do the same, and by trials he linds that the kite will fly better in a moderate wind than in a perfect culm, and that the weight at the tail may be too heavy or too light, and he regulates his actions accordingly : so f;\r he is a little philosopher. /Y man raises a kite knowing all that the boy know, but he raises it with a view of determining the state of the atmosphere so far as electricity is concerned, for which purpose, instead of employing the hempen cord, which was sulFicient for the purpose of the boy, ne employs a metallic wire, which he knows by experience will conduct the electricity from the clouds to the earth, and thus effects his design. In this respect the knowledge of the man is more extensive than that of the boy, but, this additional knowledge has been obtained exactly in the same way as the knowledge of the boy, that is to say, by experience. Kven the Indian, unlearned as he seems to be, is in some respects a philosopher. He sees daily that the paddle of his canoe is to appearance broken when he puts it into the water; but it is only to appearance, for by re- peated trials, he finds that the paddle is as whole when in the water as when out oi it. He kno\vs also, by repeated trials, that the fish, while it shoots along through the clear flood, does not appear to be where it really is ; for though the most unerring of marksmen, yet if he throws his dart directly at the point where the fish appears, he will certainly miss it. In vain will he try to strike the fish on the same principles as he strikes the bird flying in the air; but he finds, that when he directs his dart to a line which is nearer to him than that in which the fish seems to move, he will strike the fish. The Indian remembers the circumstance of his paddle, and other circumstances of a like kind, and concludes that, when bodies are viewed through water, they do not seem to be in the place in which they really are. When he knows and acts upon this principle, he is a man of science so far as this is concerned The man of science, indeed, as we commonly understand that appellation, knows much more than this : he knows that many other substances have a like effect in changing the apparent INTRODUCTION. 7 position of objects wnen seen through them nat one r* x>u> a greater and another a less change, and by rer rated trmls 1e as ,er- rains the actual amount of their changes by measurement, and can subject them to the most rigid calculation ; all of which knowledge is obtained in the same way as that of the Indian, but is more extensive. An examination of facts is the foundation of all true science ; but science does not consist in a mere examination of facts. They must be compared with each other, and the general circum- stance of their agreement carefully marked. When we have compared several facts together, and find that there is one general circumstance in which they agree, this one circumstance becomes, as it were, a chain by which they are all linked together. This general circumstance of agreement, when expressed in language, is what is called a law. For instance, it is a law that all bodies, when left to fall freely, will tend to the earth ; and this law has been framed by us, because in all cases which we have examined this has been the case ; and the term gravity, by which this law is designated, is nothing else than a name invented to express a ( circumstance in which we have found innumerable facts to agree. It was known for a very long time truflwater would not rise in a sucking pump to a height of more than thirty-two feet, and this was said to take place because nature abhorred a vacuum. The reason given was afterwards found to be false, yet the knowledge of the fact was exceedingly useful in the construction of pumps for lifting water. About the middle of the seventeenth century, Toricelli, the pupil of Galileo, made experiments on the subject, and found that fluids would rise in tubes or in sucking pumps higher in proportion as they were lighter; and collecting all the facts together, he concluded that the fluids were forced up by the pressure of the atmosphere, and thus laid down one of the most hnportant laws of physical science. A collection of such laws which refers to some particular class of objects, when properly arranged, becomes what is called a theory. Thus we see that a theory, properly so called, is founded on an examination of par- ticular facts, and of course cannot refer to any other but those facts which have been examined ; or, if it is attempted so to do, it is no longer a theory, but an hypothesis or supposition. Hypotheses although they ought not to be relied upon, are never* theless useful, as in our endeavours to discover whether they t* 8 INTRODUCTION. true or false, we may at last ascertain the class of facts to which they belong, and thus arrive at the true theory. In the examination of facts, it is to be observed, that we must depend on the information derived through the medium of the five senses, that is, the senses of seeing hearing touching tasting and smelling; for it is only by bodies affecting these organ* fhat the properties of matter become known to us ; and all that the mind does is to compare and classify the information thus derived. It is a common error to suppose that many of our greatest inventions and discoveries were made by accident. Many wonderful anecdotes are told in support of this assertion ; but the very circumstance of their exciting our wonder is sufficient to show that they are out of the common course of our experience, and that, therefore, before they are received, they ought to undergo a careful examination. A multitude of facts might be adduced to prove that knowledge is more regularly progressive than is commonly imagined. Far be it from us to detract from the merits of those great men who have, from time to time, benefited mankind by their important discoveries ; but from a survey of the history of science, wfr*are led to the conviction, that where- ever a new path has been struck out in the great field of truth, that path has been previously prepared by former inquirers. Had Kepler not discovered the three fundamental laws of the planetary motions, it is highly probable that the Principia of Newton never would have issued from the pen of that illustrious man ; and had it not been for the brilliant discoveries of Dr. Black on the subject of heat, it is probable that Watt never would have made his improvements on the steam engine, that invaluable distributer of power. It is not unlikely, however, from the state of know- ledge in the days of Newton, that, independent of the exertions of his mighty mind, the knowledge contained in the Principia would soon after have been given to the world by some one or more individuals and the like may be said of the inventions of James Watt. The great lesson which we would wish the young mechanic to .earn from these observations is that great discoveries are nevei made without preparation that previous knowledge is necessary to turn what are called accidental occurrences to good account. And when he is told that the law of gravitation was suggested INTRODUCTION. 9 to Newton by the falling of an apple from a tree in his garden or that the invention of the cotton jenny was suggested to liar greave hy the circumstance of a common spinning-wheel conti- nuing in its ordinary motion while in a state of falling to the ground let him be well assured, that, had the minds of Newton and Hargreave not been previously stored with knowledge, these discoveries never would have been made by them. Apples and spinning wheels bad fallen a thousand and a thousand times, but the knowledge necessary to turn these circumstances -to good account was first concentrated in the minds of these two illus- trious benefactors of mankind. In Smith's 'Wen kh uf Nations it is related that the ingenious apparatus for opening and shutting the valves of the steam engine was introduced by the accident of an idle boy having fastened a brick as a counterweight to the bandies which opened and shut tin. valves, and thus allowed him time to leave the machine and go to play. This simple trick of an idle boy, it is said, gave rise to the apparatus which superseded the constant attendance of a person while the engine was at work. This, however romantic, is not the fact the invention originated in necessity, no doubt, but it was begun and perfected by a thorough mechanic, Mr. H Brighton, about the year 1717. While we are on this subject we cannot pass over another very common prejudice, which we conceive has a very hurtful tendency on the progress of the young mechanic. We allude to the pride that some men take in boasting that all their knowledge is ori- ginal ; or that they are self-taught. This is, in other words, stating, that no assistance has been taken either from teachers or books ; and goes only to prove, that the knowledge of the indivi- dual so circumstanced must be very limited indeed. The unas- sisted exertions of one man must be very feeble, when compared with the collected exertions of the many who have gone before him in the career of discovery. That man must know little of geometry who has not availed himself of the use of Euclid's Elements, or some work of a similar nature; and the Elements of Euclid would have been meager and confined, had he not availed himself of the discoveries of his contemporaries and pre- decessors. A like remark may be made on the cultivation of every department of knowledge ; and to those whom we are new 10 INTRODUCTION. addressing we say learn from others all that you possibly can, and when you have done so, try to correct and improve what you have obtained. We know of no dishonourable means of acquiring knowledge, and therefore wherever we meet it we are disposed to respect it, even though it should not contain one particle of originality, if such be possible ; for it is not easy to conceive how any man should be in possession of useful knowledge, and not make some, new application of it ; and a new application of an old principle is certainly one constituent of originality. "With a knowledge of what others have done, that workman will bo less likely to waste his time in enterprises which may ruin him by their failure, or in speculations which are unsupported by the principles of science. In the museum of the mechanics' class of the university founded hv the venerable Anderson of Glasgow, there is preserved the model of a machine to procure a perpetual motion. For the con- trivance and execution of this beautiful specimen of workmanship, we are, we believe, indebted to an ingenious clock-maker of Dun- dee, who has proven himself a master in the use of his tools. But had he been acquainted with the first principles of mechanics, or with the nature and failure of the various attempts which had been made before his time for the same purpose, he would have seen the utter folly of his enterprise, and would have spent the seven years which he occupied in the construction of this truly beautiful model in some more useful employment. These seven years might have been devoted to the construction of timepieces which would have been of infinite service to the commerce and navigation of his country in guiding the lonely mariner when far away on the billow in determining the exact distance and direction of the part for which he is bound whereas, the model of his perpetual motion is preserved in the museum as a lasting monument of this clock-maker's ignorance, perseverance, and handicraft. It is another common error to suppose that genius alone can make a man a great mechanic, a great chemist, or a great any thing. Some one makes the remark, that every man is more than half humanity; and we do believe that the differences of the degrees of knowledge of different men arise more from their difference of application than from original differences of capa* INTRODUCTION. 11 city. Let, therefore, the young workman earnestly try lo learn and we do assure him that he will make advances which will he proportional to his application. This book has been written with the view of assisting the young workman in obtaining a knowledge of the calculations connected with machinery. The first part is devoted to such parts of arithmetic as workmen generally require, and in which they are most commonly deficient. Nor is this deficiency to be wondered at, since the school books in our language contain, generally speaking, no explanation of the nature of the rules which they give, and are, moreover, embarrassed with so many divisions and subdivisions, that the mind of the scholar is per- fectly perplexed, nor can it lay hold of the great leading principles which pervade the whole system. As this is the great instrument used throughout the book, we have endeavoured to make its use and management easily understood. The examples which we have given are indeed few and simple ; but, if carefully consi- dered, they will be found sufficient to establish the principle. The mere habit of calculation cannot be said to constitute a knowledge of arithmetic ; it is easily obtained, but is of no avail without the principles. This is well illustrated by an occurrence of but recent date. To construct a set of mathematical tables requires, not only a knowledge of principles, but also immense calculation. M. De Pronney was desired by the government of France to construct a very large set of such tables ; a task which would require the labour of a mathematician for many years. But Pronney fell upon an expedient which was every way worthy of a man of science. A change in the fashions of the Parisians had thrown about five hundered wig-makers idle, and Pronney contrived at once to give employment to these barbers, and at the same time to serve the purposes of science. He digested the principles of the calculation of these tables into short and simple rules, and printed forms of them, which he gave into the hands of these workmen, who, in a few months, produced a set of tables, the most correct and extensive that ever has been made. The peruke-makers may, so far as the construction of the tables was concerned, be regarded as mere machines, under the guidance of M. de Pronney. The same principle has been of late years car- ried to a far greater extent by our countryman, Professor Babbage, who has invented a machine by which logarithms and astrono- 12 INTRODUCTION. mica) tables may be calculated and printed with the ttos lunerring certainty, thus obviating the necessity of employing either calcu lators or compositors. Let not these statements induce you, however, to neglect the practice of calculation ; on the contrary, improve yourself in it wherever you can, but be also careful to learn the principle. In that part devoted to geometry, we have given such informa- tion without demonstration as was necessary to the right under- standing of the rest of the book ; and the like may be said of the conic sections, mensuration, and useful curves. Thus far the book may be said to be a compend of certain branches of the mathematics. It is hoped that the reader, to whom such studies are new, will not be contented lo stop here ; but will be induced to investigate these subjects in theory ; and for such as may be desirous of entering on such a course of study, where there is nothing to be met with but unsophisticated truths connected together by a chain of the most beautiful relations, we intend to offer a few words of well-meant advice as to the order and means of prosecuting such studies.* In the first place, let the Elements of Euclid be studied so far as the end of the first book, in the course of which it should be borne in mind, that there is nothing really difficult to be met with. The greatest difficulty is, we believe, this, that, to a proposition which is so simple as to be almost self-evident, there is often * In a very creditable work, recently published, " Stuart's History oi the Steam Engine, " it is stated that mathematics is not necessary to make a great mechanic, and Watt is cited as an instance. The instance chosen is most unfortunate for the author's assertion. Watt was de- scended from a family of mathematicians, and inherited in the highest degree the genius of his ancestors. One instance will sufficiently prove this. With a desire to determine what relation the boiling point bore to the pressure of the atmosphere on the surface of the water, he made several experiments with apothecaries' phials, and having found the rela- tion between the pressure and temperature of ebullition, under different circumstances, he laid the temperatures down as abscissae, and the pres- sures as orrtinates, and thus found a curve whose equation gave that weF. known formula, the equation of the boiling point. No man but a mathe* matician of high attainments would have thought of such a method of proceeding. To this we may add, that mechanics is a branch of mathe matics ; tor, as Sir Isaac Newton has defined it, " mechanics is the geo- metry of motion." INTRODUCTION. 13 attached a long demonstration, which is apt to lead the reader to suppose that there is really something mysterious in it, which he does not understand. This proceeds from the fact, that itoften requires a greater deal of circumlocution to show the connection of simple propositions with first principles, compared with propo- sitions which are more complex ; but we have no hesitation in saying, that if the steps of the propositions are carefully consi- dered, one by one, they will be easily understood, and will lead at last to perfect conviction ; for, as Lord Brougham has well observed, " Mathematical language is not only the simplest and most easily understood of any, but the shortest also ;" and Euclid has transmitted to posterity a specimen of the purest mathemati- cal language. Of Euclid's Elements, there are various editions. Those of Simpson and Playfair are generally used in this country, and are deservedly popular. That of Dr. Thomson is a very valuable work, and very correct. But we beg to recommend to the workman the edition of Mr. Robert Wallace, of Glasgow, both for its execution and cheapness. The demonstrations are clear and short ; many new propositions are added, and the con- nection of theory with practice is never omitted where it can be introduced. When the first book of Euclid has been read, the study of al- gebra should be commenced, on which subject there are few good treatises to be found. That which we think best is the treatise of Euler, a book which has come from the hand of a master, and is therefore characterized by great simplicity. Another good book is the treatise of Saunderson. Let either of these works, or others if they cannot be had, be read carefully so far as to equations of the second degree. If any one part of this depart- ment can be said to be difficult, it is that of powers and roots, which is a subject of the greatest importance; and should, on that account, receive the most careful attention; and, if the trea- tise of Euler be used, we have no hesitation in saying, that little difficulty will be experienced. Jt may be necessary to observe, that attention should be paid all along to the intimate connection of arithmetic and algebra, which will tend to the better under- standing of them both. Having advanced thus far, Euclid must again be returned to ; and, after revising the first book, re.d on to the sixth inclusive. Occasional revision of the algebra is recommended, and an advancement as far as equations of the 2 14 INTRODUCTION. third degree ; after which Euclid may be read to the termination. The study of trigonometry may then be introduced; on which subpect we have various works of various merits. The treatise prefixed to Brown's Logarithmic Tables may be employed ; and when it is understood, and the management of the logarithmic tables acquired, the works of Gregory, Lardner, or Thomson may be consulted ; the last is the most simple. After the study of trigonometry, Simpson's conic sections may be read with advan- tage. Perhaps it may be a kind of relief at this stage, to see some- thing of the application of mathematics to mechanics, and, for this purpose, the work of Keil on Physics, or the article Mecha- nics, Hutton's Mathematics, Tegg's edition. The neat little treatise of Mr. Hay of Edinburgh will answer the same purpose exceedingly well. But for the purpose of obtaining a good know- ledge of theoretical mechanics, a more extensive knowledge of mathematics than we have hitherto supposed becomes absolutely necessary. A knowledge of the method of fluxions and fluents, or the differential and integral calculus, which bear a strong ana- logy to each other, and which have been employed for similar purposes. The simplest work on fluxions, and we believe the best, is the treatise of Simpson ; and this may be followed by a perusal of Thomson's differential and integral calculus. With this preparation the student may now go on to read the first vo- lume of Gregory's Mechanics, a book in which, we believe, he will find ample satisfaction. The second volume of this excellent work is almost entirely popular, and can cause no difficulty what- ever. Another work, well worthy of a perusal, is that of Sir John Leslie : we allude to his Natural Philosophy ; a book which, though neither strictly mathematical, nor strictly popular, yet contains much valuable information communicated in both ways. Indeed all the works of this great man, although much has been said against them as to the floridness of their style, will, never- theless, be found to amply repay the trouble of a perusal. THE MODERN MECHANIC. ARITHMETIC. VULGAR FRACTIONS. 1. IN many cases of division after the quotient is ob- tained? there is a remainder, which is placed at the end of the quotient, above a small line with the divisor under it : thus 88 divided by 12 gives the quotient 7 and remainder 4, which is written 12) 88 (7 T 4 2- Now, this T \' s ca M e( l a frac- tion ; and it is written in this way to show that 4 ought to be divided by 12 ; and in all cases where we meet with num- bers written in this form, we conclude that the number above the line is to be divided by that under the line. This should be well borne in mind, as it is of the greatest use in obtaining a clear notion of fractions. 2. A fraction is said to express any number of the equal parts into which one whole is divided. It consists of two num- bers one placed above and the other below a small line. The upper number is called the Numerator, because it numerates how many parts the fraction expresses ; and the under number is called the Denominator, because it ex- presses or denominates of what kind these parts are ; or, in other words, the denominator shows into how many parts one inch, foot, yard, mile one whole any thing is sup- posed to be divided ; and the numerator shows how many of these parts are taken : as ^ f a foot. The denominator shows that the foot is here divided into 12 equal parts (inches ;) and the numerator 4, shows that four of these parts are taken (4 inches.) 2* 17 18 AKITHMETIC 3. If the numerator had been equal to the denominator, as ^4, then the value of the fraction would have been one whole (foot;) and the numerator, being divided by the denominator, gives 1 as a quotient. In the fraction }| of a foot, the numerator is greater than the denominator, and the value of the fraction is greater than one : for the foot being divided into twelve equal parts, (inches,) and fourteen such parts (inches) being expressed by this fraction, its value is more than one foot ; and the numerator being divided by the denominator, gives \^ . Again, /^ of a foot is just six inches, or one-half foot ; and had the foot been divided into two equal parts, one of these parts would have been equal to T 6 5 , or 5 is equal to T *v. From this we may conclude, that when the numerator is equal to, less, or greater than the denominator, the value of the fraction is equal to, less, or greater than one whole. It is, then, not the numbers which express the numerator and denominator of a fraction, but the relation they bear to each other, that determines the real value of a fraction. , f , f , -,"2, are ah equal, although expressed by different numbers, the deno- minators of all the fractions being respectively doubles of their numerators. 4. From what has been said, it will easily be seen* that, if we multiply or divide both terms of any fraction by the same number, a new fraction will be found, equal to the first ; thus, ; multiply both terms by 2, we get T 8 ff , or divide them by 2, f , and these again by 2, . All who know any thing of a common foot-rule will understand this, at sight. 5. The first use which we shall make of the principle last stated, is to bring two or more fractions to the same deno- minator, and that without altering their real values. For example, take f and | of a foot. Multiply both terms of the first fraction f by the denominator of the second, 4 : we get j%. Next multiply both terms of the second fraction by the denominator of the first fraction, that is, | by 3 : the result is -j\. Now it will^be seen (from No. 4) that these two fractions, T 8 ^ and 7 9 ^, are equal to the two f and |, with this additional advantage, however, that they have the same denominator, 12 : the great use of which will be seen here after. A like process is employed in the case of three or more fractions : thus, , |, , multiply the terms of the first fraction by 4 and 5, the denominators of the second VULGAK FHACTIONS. 18 and third, we get |- ; next multiply the second | by 3 and 5, the denominators of the first and third, we next get - ; lastly) multiply the third by the denominators of the first and second, 3 and 4, we get |. It will be useful to look over what we have done. In obtaining the numerators of the new fractions, we have multiplied each numerator in the former fractions by all the denominators except its own ; and so also for the denominators. But 3 multiplied by 4, and 4 multiplied by 3, are the same thing, viz. 12 : so, like- wise, 3 multiplied by 4 multiplied by 5 is 60, and will be 60 in whatever order we take them 3 by 4 by 5, or 4 by 3 by 5, or 5 by 3 by 4 ; when, therefore, we have obtained one deno- minator, it is sufficient. Hence the usual rule to reduce fractions to a common denominator : Multiply each nume- rator by all the denominators except its own for new nume- rators, and all th denominators together for the common denominator. 6. We are now prepared to add two or more fractions together. It is very easy to see how we may add f and | of an inch, and that their sum is ; but it is not quite so evident how we are to add f and | of a foot. If we had them, however, of one denomination, the difficulty would vanish. By No. 5, bring them to a common denominator they stand thus : T \ and -^, or 8 and 9 inches ; add the numerators, and under their sum place the denominator, }|- ; divide the numerator by the denominator, (No 1,) the quo- tient is 1 T V, or one foot five inches. The reason of bring- ing them to a common denominator is, that we cannot add unlike quantities together : and we do not add the denomi- nators, their ojply use being to show of what kind the quan- tities are. The rule, then, is bring the fractions to a common denominator, add the numerators together, and under their sum place the common denominator. 7. In subtraction we bring the fractions to a common dei ominator, and taking the lesser from the greater of the two numerators, place under their difference the common denominator. The reirson of this may be easily inferred from (No. 6) | subtracted from 5, when brought to a com- mon denominator, T 6 g from T 8 j the 1 difference is T 2 ? , equal to i, by No. 4. 8. To take one number as often as there are units in another, is to multiply the one number by the other. To multiply 4 by 2, is to take the number four two times, an 20 ARITHMETIC. there are two units in 2 ; and to multiply 4 by |, is to take four one-half times, or the half of four, as there is only half a unit in the fraction 5. This may be thought so simple, that it need not be stated ; but, let it be observed, that it explains a fact in the multiplication of fractions, which many excellent practical arithmeticians do not understand ; viz. how that, when we multiply by a fraction, the product is less than the number multiplied. If the fraction 5 is to be multiplied by ?, (let the fractions both refer to an inch,) this is taking 5 (inch) ? times, or taking the one-fourth part of one-half inch, which is one-eighth. The product 5 is obtained by this simple process : multiply the numerators together for a new numerator, and the denominators to- gether for a new denominator ; the new fraction will be the product. That this is true in general may be shown by taking other fractions, thus: of f, *he product by the rule is ^, which may be simplified by dividing the nume- rator and denominator by the same number, on the principle of No. 4 ; if 4 be the divisor, the result is -, which is the same as %. Now, that % is the real product of | by f , may be shown thus : divide a line AB into six equal parts ; take two of c these parts, and join them by A r CD. Divide CD into four parts, and it will be seen that the two parts of this line CD are just equal to one division on the line AB ; or f of CD is equal to of AB ; so that,,! f f ls ! ^' ne ru l e > then, is general. 9. Division is the reverse of multiplication; hence, to divide in fractions, invert the divisor, and proceed as in multiplication. Thus, to divide by |, insert the divisor 4, it becomes ^, which, multiplied by 5 gives 5 multiplied by }, equal to f ; and by dividing, to make the fraction less, we obtain f, which, by No. 1, is just 2 or twice. This is he quotient ; and it is easily seen, if these fractions relate to a foot, that there are 2 quarters or twice of a foot, in one-half foot, or 5. 10. We have now endeavoured* to explain the nature of the fundamental rules of vulgar fractions, as simply as pos- sible ; but instances often occur, where it is necessary to prepare for these operations ; first, where whole numbers are concerned ; and secondly, where the fractions are large, and, consequently, not so easily managed. 11. As to the first, where whole numbers are concerned. VULGAR FRACTIONS. 21 t is to be observed, that when unit, or 1, is used, either to multiply or divide a number, it does not change the value of that number. Thus, 6 multiplied by 1 is 6, and 6 divided by 1 is 6. According to the principle shown in No. 1, we may write the number 6 in this way, f , without altering its real value with this advantage, that we have it now in the form of a fraction. We shall illustrate this by a few examples, and show that numbers, whether whole or frac- tional, are in this department of arithmetic managed by the same rules. Add 8 to |, here we write them and I, which, brought to a common denominator, are, 3 T 2 , I their sum is 3 ? s ; then by No. 1, divide the numerator by the denominator, we get 8|, the number we set out from. 7 j, which is read seven and a third, may on the same principle be put in the form of a common fraction : for it is 7 wholes added to 5 part of a whole, and may be thus written, | and 5, equal to a - and whose sum is \ 2 ; divide the 22 by the 3, the result is 7j, the first number. This very simple principle is often used, and is embraced in the following rule multiply the whole number by the denominator of the fraction, add the nume- rator, and under the sum place the denominator. 12. When the fractions are very large, it becomes neces- sary to bring them to a simple form, not only that we may more easily see their value, but that they may be more readily operated upon. Thus, j\ is not so simple nor so easily managed as T T j, and the one fraction is just equal in value to the other; for, by No. 4, the numerator and deno- minator of 7 6 2 being both divided by 6, gives T 'j. Also, .ji^Pg., when 100 is used as a divisor, gives ? V- Whenever we can find a number which will divide both terms of the fraction without remainders, we ought to employ it, and thus make the fraction simpler in form, though of exactly the same value. The divisor thus used to simplify fractions, is usually called the common measure, and may frequently : found at sight, although sometimes there is no such number at all. Thus, in ~ , it is seen at once that 2 is the common measure ; but in the fraction | no such common measure can be found : consequently, the fraction cannot be made more simple. Sometimes, also, two or more numbers will divide the fraction ; thus, f may be divided by 4 or by 2 the greatest is preferred, because it brings the fraction to the lowest terms at once. When this cannot be obtained at 22 ARITHMETIC. sight, the following rule may be employed : Divide the greater term by the less ; if these leave any remainder, divide the last term by it ; and thus go on dividing the last divisor by the last remainder, and that divisor which leaves no remainder is the greatest common measure. This rule may be applied to the following example : 1 470 By the above rule. 2205 1470 ) 2205 ( 1 1470 ~735) 1470 (2 1470 735 is the common measure ; therefore, 735 ) ( f , the simple form of the fraction DECIMAL FRACTIONS. 13. LET us examine the number 3333, (three thousand, three hundred, thirty and three.) The same figure is used, but for every place it is removed towards the left, its value is increased ten times ; and consequently, if we begin at the left hand side, and go on towards the right, we see that every figure has a value ten times less than the same figure placed one place nearer the left, each number expressing tenth parts of the number next it to the left. Hundreds are just tenth parts of thousands ; tens are tenth parts of hun- dreds ; and units are tenth parts of tens, &c. Now. the same 3333, with a point placed before any of its figures, would still have the same property of each figure towards the right, having a tenth part of the value it would have had in the next place towards the left : that is to say, the point has no effect in altering the relative value of the figures ; but it has this effect, that the figure which stands at its right hand would signify units : thus, 33-33, where we have the same figures as before, with a point placed betwixt the middle two, and from what has been said, we conclude that DECIMAL FRACTIONS. 23 the 3 to the left of the point is units. From this it follows that the next 3 on the right of the point is tenth parts of unity, and the 3 following that again tenth parts of a tenth part of unity, or hundredth parts. Had it been written thus : 3.333, the last three to the right of the point would have been a tenth less again, &c ; so that all the figures that follow the point to the right are less than units, conse- quently, they are fractional ; and from their decreasing by tenths each place, they are called Decimal fractions from the Latin word decem, ten. Thus, then, T \ may be written '3. 14. It is to be observed here, that the use of the cipher (0) is in decimals quite similar to what it is in whole r. ambers, where its only use is to remove some figure from the units' place, and therefore alter its value tenfold. Thus, in the number 40, the cipher of itself signifies nothing, but serves to remove the 4 to the tens' place. Had it been 04 here the cipher is of no use, because there is no figure to remove beyond it from the units' place. The same is true of any number of units. Now, we have seen that '3 is just T 3 ^ and, from what has been said, it will follow, that .03 is three hundredth parts, or T 7 , as the cipher in '03 removes the '3 a place farther from the units' place towards the right, and (No. 13) makes it ten times less in value than it would have been had it been one place nearer the left ; or, it is now tenth parts of a tenth part. For the same reason '003 is the same as -j-^^. 15. The number 33 is read thirty and three, and '33 is read three tenths and three hundredths, or sometimes thirty-three hundreds. Now, T 3 , added to jfa give (No. 6) fVisV which, simplified, is T 3 ^, (No. 4.) If we wished to write jjjVo in the other form, it is done simply thus : point in tenth's place, in hundredth's place, and 3 in thousandth's place ; that is, -003. Take, now, - t \ and T |^ ; adding, then, by No. 6, we get-j^, ^, simplified ~ s , which, written with the point, is simply *46. We may now see, that any number placed after the decimal point is a fraction ; which may be expressed by a numerator which is that number, and a de- nominator consisting of 1, with as many ciphers annexed as there are figures in the numerator : thus, '3034 is the same thing as T VVoV 16. These simple statements being understood, all that follows will be easy. The principle being kept in mind, that the numbers to the one side of the point have the same 24 ARITHMETIC. relation to one another as those on the other, e\ery figure on the one side of the point as well as on the other, being ten times greater than it would have been in the next place to the right, and ten times less than in that to the left. 17. To add decimal fractions, we proceed just as.in whole numbers, placing units under units, and consequently points under points, and carrying to each new column to the left, by 1 for every ten in the column already added. As ^ may be written T S 7 or *5 ; 7 may, therefore, be written 7'5 ; 4^ may be written 4-5. Now, add 7*5 and 4-5 by the rule we have given, and we will obtain a' 7"5 result which must be correct, as may be 4-5 proved by principles laid down in the former 12'0 chapter. Here we have kept the points under each other, and put a point in the answer just under the others, and the sum is 12, with no decimal fraction. Take 7 J and bring it to the form of a common vulgar fraction, by the principle, No. 1 1 , and it will be y ; do so likewise with 4 and we get | ; they have a common denominator, and add them by No. 6, we have 2 ^ 4 , now, this fraction, by No. 4, is equal to l ^, or 12, the same as before. Take now 135*7, and 1-23, and -764, and 9-102, and 8-003, and -035; to find their sum. Here we place, as before, all the points under each other, and proceed as in addition of whole numbers, carry- ing by tens and pointing the sum in the line under the other points : 135-7 1-23 764 9-102 8-003 035 154-834 18. Subtraction is managed in like manner as in common numbers, the same attention being paid to the points. Thus, subtract 33-785 from 1967 : 32 ; they are placed thus, and subtracted as 1967*320 in whole numbers, the point in the 33-785 answer being placed in a line with the 1933-535 others. It is to be observed, that there are more decimal places in the under number than 'n th" DECIMAL FRACTIONS. 25 upper, and the deficiency may be supplied by adding ciphers to the upper line, which, as there is no significant figure beyond, does not alter the value of the number. 19. Multiplication of decimal fractions is performed as in whole numbers, paying no attention to*the points until the product is obtained, when we point off as many places from the right hand side of the product, as there are decimal places in both the multiplicand and the number which mul- tiplies, or multiplier. Thus, multiply 36-42 by 4-7. Here -174 are pointed 36-42 off as decimals, as there are two deci- 4*7 mal places in the multiplicand and one 25494 in the multiplier in all three. That 14568 this rule is correct, may be inferred 17 1-174 from the results of a former example in No. 8. Here we multiplied 4 by , and found the pro- duct to be 2 : now, is equal to T * T , which may be written 5 ; then let us multiply 4 by -5, as directed above, and we will find th same result, 2 ; where, by principle of No. 14, the cipher being pointed off, there remains 2 a whole 2-0 number. 20. Division may be properly defined, the finding of one number (the quotient), such, that when multiplied by another (the divisor), will give a product equal to a third (the dividend). The dividend may thus be viewed as the product of the quotient and divisor ; hence, the quotient and divisor should, together, contain as many decimal places as the dividend. This being observed, the rule will be easily followed : Divide as in whole numbers, and when the quo- tient is obtained, point off from the right as many places for decimals as those of the divisor want of those in the dividend. Divide 22-578 by 48-6, the quotient 4-6f|.| is obtained by 48-6)22'578(4-6f f.f common division, and pointed thus, because the divisor wants only one decimal place to have as many as the dividend. In many cases, when the quo- tient is obtained, there will not be as many figures as make up the number of decimal places required ; here we must place one or more ciphers betwixt the point and the quo- tient figures, so as to make up the number required. Thus, divide 1-0384 by 236, the quotient is 44 only two places, whereas there should be four decimals in the quotient ; 8 26 AUITHMETIC. because there are four in the dividend and none in tha divisor. We, therefore, place the quotient thus, -0044 , and to prove that this is the true quotient, we have only to multiply it by the divisor, and the product being the same as the dividend, the operation must be correct. 21. From the great facility with which decimal fractions may be managed, it is very desirable that we could bring vulgar fractions to the same form, in order that they might more easily be wrought with. Now, this may be done on the principles already laid down : take the fraction --, and, on the principle of No. 4, multiply both terms by 1000, it then becomes J , which is equal to I ; divide (No. 4) both numerator and denominator by 8 ; then 8) --$ ( T Wo which last fraction is expressed in the decimal notation thus, (on the principle of No. 15,) '125, which, from the way it has been derived, must be equal to G. This may, however, be found more immediately thus : add as many ciphers to the numerator as you find necessary, and divide by the denomi- nator thus, 8)1000(-125. If we have only to add one cipher before we get a quotient figure, we put a point in the quotient ; but if more, then we put as many ciphers in the quotient after the point. Thus, -j ; 25)100('04, and TJ is just T ^, or -04. 22. In many cases the quotient would go on without end; but it is to be observed, that it is not necessary to continue any operation in decimals, at least in mechanical calcula- tions, beyond three or four places, as ten thousandth parts are seldom necessary to be considered in practice. For similar reasons, it is unnecessary to give rules for repeating and circulating decimals : i. e. decimal numbers, when the same figures recur in some order thus, '3333, or, 142142, &c., carry them to four places, and it is all that is neces- sary. Other applications of these principles will be found in the next chapter, on compound numbers. COMPOUND NUMBERS. 23. IN mechanical calculations, we are often concerned with weights and measures, and it is necessary to know how to operate with the numbers which express these. The rule COMPOUND NUMBKRS. 27 given in books of arithmetic are generally very long, and, therefore, not very easily understood ; yet the steps of the operation are simple. We shall therefore show the mode of procedure, in some very easy examples, and the reader will find no difficulty in applying the principles he may thus im- bibe to cases more complex.- 24. If we have to add 9 yards 2 feet 6 J' ds - feet "* inches, to 2 yards 1 foot 3 inches, 8 yards feet 1 1 inches, long measure. Then we ^ must in this, as in all other cases of com- pound addition, arrange them in order, -20 1 8 the greater towards the left hand, and the lesser towards the right ; and there must be a column for every denomina- tion of weight or measure, in which column the respective quantities must stand, so that feet will stand under feet, inch- es under inches, pounds under pounds, and ounces under ounces, &c. Add now the column toward the right, which in this example amounts to 20 inches, or 1 foot 8 inches, we therefore put down the 8 inches under the column of inches, and add the 1 foot to the column of feet, which comes to 4 feet ; that is, 1 yard and 1 foot. The 1 foot is put down un- der the column of feet, and the 1 yard is added, or carried, as it is usually called, to the column of yards, whose sum is 20. If we have to add 2 tons tons cwt quar lbs> oz< 2 cwt. 1 quar. 17 Ibs. 10 3 2 1 17 10 oz. avoirdupois, to 12 tons 12 10 2 2 10 cwt. 2 Ibs. 2 oz., 2 cwt. 02 1 18 3 1 quar. 18 Ibs. 3 oz., and Q Q Q 911 9 Ibs. 1 1 oz. ; then, from -^ ^ 3 ^ ^ what was remarked above, they will be put down as in the margin. Then the sum of the right hand column is 26 oz., which is 1 Ib. 10 oz., we put down the 10 in the column of oz., and carry the 1 Ib. to the column of Ibs. which is next ; and this when added comes to 47 Ibs., that is, 1 quar. and 19 Ibs. ; the 19 is put in the column of Ibs. and the 1 is carried to that of quars., which comes to 3, which not amounting to 1 cwt. we put down the 3 in the column of quars. and carry nothing to the column of cwts., which, when added, amounts to 14, this we put down, and, as it does not amount to 20 cwt. or 1 ton, we carry nothing to the column of tons ; and when this co- lumn is added, its sum is 14. 25. In Subtraction the same principle of arrangement is to 28 ARITHMETIC. be observed, and the lesser quantity is to be put under the greater. If we have to subtract 1 ton 13 cwt. 2 quars. 17 Ibs 12 oz., from 9 tons 8 cwt. tons cwt quars lbs oz 1 quar. 4 lbs 7 oz. avoirdu- 98147 pois, they are arranged as j 13 2 17 12 in the margin- We begin ~ j^ % 14 TT to subtract at the lowest denomination, viz. oz. 12 oz. from 7 oz. we cannot, bu we add a Ib. or 16 oz. to the 7, which is supposed to be borrowed from the column of lbs. which stands next it, towards the left ; now 16 added to 7 makes 23, and 12 from 23 leaves 11, which is put down .in the column of oz. Now we must pay back to the column of lbs. the pound or 16oz. which we borrowed, therefore, it is 18 from 4. Here we have to borrow from the column of quars., and 1 quar. being 28 lbs. we borrow 28, then 28 and 4 are 32, there- fore 18 from 32 leaves T4, which is put down, and the 1 quar. paid back to the column of quars.; 3 from 1, we cannot, and must borrow 1 cwt. or 4 quars., therefore 3 from 5 and 2 remains, which is put down. Add 1 to 13 for the 1 cwt. that was borrowed, then 14 from 8, we cannot, but borrow 20 from the next column, then 14 from 28 and 14 remains. Pay back to the column of tons the 1 ton, or 20 cwt. which we borrowed, then 2 from 9 and 7 remains, which is put down. The same principle holds in other examples, the only va riation being that the numbers to be borrowed from the next higher column, will depend upon the relative values of these columns, which may be known by examining a table of the particular weight or measure to which the example may refer. 26. In Multiplication, which is only a short way of perform- ing addition in particular cases ; the principles are nearly similar : thus, to multiply 3 tons 2 cwt. 2 quars. 6 lbs. 10 oz. by 3; they are arranged tons cwt quars lbs> oz as in margin. 1 hen the first 3 2 2 6 10 product is 30 oz. or 1 Ib. 3 which is carried to the co- Q ^ r^r rr* lumn of lbs., and 14 oz., which is put down in the column of oz. The product of the lbs. is 18, and the one Ib. carried is 19, which no amounting to 28 lbs. or 1 quar., nothing is to be carried to the column of quars. The product of the quars. is 6, which is 1 cwt. to be carried and 2 quars. to be put down. COMPOUND NUMBERS. 29 The product of cwts. is 6, and the one carried from the former column makes 7, nothing being carried ; the co- lumn of tons is 9. By examining the following examples, and referring to the tables of weights and measures, the general application may be easily inferred. See Appendix to Arithmetic. Degrees, min. seconds. yds. feet. inch. 8th parts, 23 14 17 17 2 9 6 6 ' 5^ 139 ^5 42 89 _2 _0 _6 Carry by "60 60 ~3 12 ~8 27. It may not be out of place here to notice, Duodeci- mal, or what is commonly called Cross Multiplication ; which is very useful to artificers in general, in measuring timber, &c. The foot is divided into 12 inches, each inch into 12 parts, and each part again into 12 seconds ; these last, however, are so small, that they are generally neglected in calculation. If we wish to find the surface of a plank, whose breadth is 1 foot 7 inches, and length 8 feet 5 8 5 inches, we place the one under the other, \ 7 feet under feet, inches under inches, &c., Q ^ as in the margin. Multiply the inches . , ~ , . and feet in the upper line, by the feet in the under line, placing the product ^ of the inches, under the inches, and that of the feet, under the feet. Then multiply the inches and feet, of the upper line, by the inches in the under line, placing the product one place further towards the right, and carry by twelves where necessary ; as in this example, 7 times 5 is 35, that is, two twelves and 11 over; the 11 is put down, and the 2 added to the product of the next column, 7 times 8 is 56, and the 2 carried makes 58, that is four twelves and 10 over ; the 10 is put down, and the 4 carried to the next column. These are now added, observing again to carry by twelves. feet. inch. feet. inch, parts. 47 35 4 6 8 4 12 3 4 36 8 164 38 424 6 8 10 1 6 11 9 6 434 3 11 3* 30 ARITHMETIC. The feet in the example are square feet, but the inches are not square, as might be thought at first sight, but 12th parts of a square foot ; and also the numbers standing in the third place, are 12th parts of these 12 parts of a foot, and so on. 28. Before we consider the Division of compound num- bers, it will be necessary to attend a little to the nature of reduction. This is usually thought by beginners to be very- perplexing, but a little attention to the principle, will ob- viate all this apparent difficulty. In every lineal foot there are 12 inches, and therefore there will be 12 times as many inches, in any number of feet, as there are feet; thus, in 8 feet there are 8 times 12, that is, 96 inches. In every Ib. avoirdupois there are 16 ounces, therefore in 18 Ibs. there are 18 times 16, that is, 288 ounces. So that we multiply the higher denomina- tion, by that number of the lower which makes one of the higher, and the product is the number of the lower contained in the number of the higher, which we multiply. In the pre- vious examples, feet and pounds are the higher denomina- tions, and inches and ounces are the lower. From these remarks it will be easy to see, how we proceed in rinding the number of parts of an inch contained in 3 yards 2 feet 7 inches, and J- parts, long measure. Bring the yards to feet, 3 multiplied by 3 are 9, to which we add the 2 feet, which make 11. This brought to inches, is 11 mul- tiplied by 12, or 132, to which we add the 7 inches, making 139. This brought to parts gives 139, multiplied by 8, that is, 1112, to which we add the 5 eighth parts, making 1117 the answer. The examples subjoined are managed in a like manner; the multipliers varying with the kind of weight or mta- eure. cwt. quar. Ibs. acres. roods. poles. 27 1 22 22 3 24 4 mult. 4 mult. 108 quars. 88 roods 1 add 3 add 109 quars. 91 roods 28 mult. 40 mult. 3052 Ibs. 3640 poles 22 add 24 add 3074 Ibs. 3664 poles. COMPOUND NUMBERS. 31 The work is reversed, when we wish to ascertain how many of a higher denomination are contained in any num- ber of a lower. Thus, in 1440 inches, long measure, there will be one foot for every 12 inches, we therefore divide 1440 by 12, and the quotient will be the number of feet, that is, 120 feet. Then there is no remainder, but if there had, it would have been of the same kind with the dividend, that is, inches. In the same way lind how many tons, cwts. quars. and Ibs., are contained in 12345678 oz. oz. in 1 lb. 16 ) 12345678 ounces. Ibs. in 1 quar. 28 ~)771604 Ibs. 14 oz. quars. in cwt. 4 )27557 quars. 8 Ibs. cwt. in 1 ton 20 )6889 cwt. 1 quar. 344 tons 9 cwt. The answer therefore is 344 tons 9 cwt. 1 quar. 8 lb. 14 oz. which may be proved by reducing the work to ouncef by the method given above. 29. It is frequently of great use, to express compound numbers fractionally ; thus, so many feet and inches as the fraction of a yard. What fraction of a yard is 2 feet 8 inches ? Now, from what has been said on vulgar fractions, it will be easily seen that one yard is here the unit, or de- nominator of the fraction, which must of course be brought to inches. Now there are 36 inches in one yard, which must be the denominator of the fraction, and the numera- tor will be the quantity taken ; that is, 2 feet 8 inches re- duced to inches, or 32 inches. The fraction therefore is ff, or simplilied , which, turned into a decimal, is 0*8888, one yard being 1. So likewise, what fraction of a cwt. is 2 qrs. 14 Ibs. 3 oz.? This last reduced to ounces is 1123, which is the numerator of the fraction, and the denomina- tor is 1 cwt. reduced to oz., or 1792 oz. ; the fraction is therefore jif ?, which is expressed decimally 0-6264. We think that these examples will be sufficient to show the mode of procedure, and it remains for us to consider the reverse of this; to estimate the value of such fractions in terms of the weight or measure to which they refer. 3C. It will be easily seen, that one-half of a foot is twelve times greater than one-half of an inch, or that any given part of a foot, is a twelve times greater part of an inch ; thus, 5 of a foot is y of an inch ; so that to bring any fraction of 32 ARITHMETIC. a foot to the fraction of an inch, we have only to multiply the numerator by 12. So likewise $ of a pound avoirdupois, is */, of an ounce, and ^ of a yard is -^ of a foot, or 3 -j of an .'nch; and if we divide the numerator by the denominator, we get in the last example ^ of a yard, equivalent to 7y inches. What is the value of 5 of 1 cwt. ? By applying the fore- going principle it will be found that 5 of 1 cwt. is A of a quar., or a 28 times greater part of 1 lb., that is l ^- 2 ; that is 37 5 Ibs. also | of 1 lb. is 16 times 5 of an ounce, or y, equal to 5| ounces. 31. It will generally be found best to express these deci- mally, thus, the last example will be i of a cwt. or 0.333 of a cwt., or 1.333 of a quar., or 37.666 of a pound. Thus it appears that any fraction of a cwt. is 4 times greater than a like fraction of a quarter, and any fraction of a quarter is 28 times greater than a similar fraction of a pound ; hence, to reduce a fraction of a higher to its value in a lower denomination, we multiply the numerator of the frac- tion, by that number which expresses how many of the lower are contained in one of the higher, while the denominator remains unaltered. On the other hand, to bring a fraction from a lower to a higher denomination, the numerator re- mains the same ; but we multiply the denominator by that number which expresses how many of the lower is contained in one of the higher. Thus i of an inch is J ff of a foot, or -j-^g- of a yard ; or expressed in decimals 0.3333 of an inch, or 0.0277 of a foot, or 0.00924 of a yard. 32. On a like principle the value of a decimal expressing weight or measure, may be determined, simply by multiply- ing the decimal by that number of the next lower denomi nation, which is contained in one of the higher, and cutting off the proper number of decimals in the product, thus : 37689 of a cwt. 4 1.50756 quarters. 28 14.21168 pounds. 3.38688 Here it will be observed, that the integers or whole num POWERS AND ROOTS. 33 bers cut off are not multiplied, and the value of .37689 of a cwt. is 1 quar. 14 Ibs. 3.386 oz. We will conclude this chapter on compound numbers, with some remarks on Division. The same arrangement ia to be observed here as in addition ; the greater quantity be- ing towards the left of the lesser. Let it be required to divide 13 yards 2 feet 8 inches by 4. We say 4 in 13, 3 times and 1 over, that is one yard, which must be reduced to feet, the next lower denomination; that is 3 feet, and the 2 feet are five feet now 4 in 5, 1 and 1 over, which last being a foot, must be reduced to inches ; it is therefore 12 inches, and the 8 make 20 ; then 4 in 20, times ; the answer therefore is 3 yards, 1 foot, 5 inches. yards. feet. inch. yards. feet. inch. 3) 16 2 9(5 1 11 15 ~T 3 mult. 3 2 add T 3 2 12 mult 24 9 add 3) 33 33 POWERS AND ROOTS. 32. THE square of any number is the product of that number multiplied by itself: thus, the square of 2 is 4, the square of 4 is 16, the square of 5 is 25, 3. The rule for tin; measurement of the surface of timber, given in our remarks on the sliding ruic, may be expressed thus, length xbreadtk s area; and the rule for simple pro- portion, to be given in the next chapter, may also be writtea thus : Second term X third term, =iourth term. first tenu, 54. It is obvious that this is merely a kind of short hand which might he carried still farther ; for instance, in the last example we rnijrla make F stand for the first term, S for the second, T for the third, and for the last, aad the rule woul'i then bo 55. We again insist that the young reader will read this chapter carei'uiiy over. PROPORTION. 56. When four numbers following eaoh other are such that the first is as many times greater or less than the second, as the third is greater or less than the fourth, they are said to be in proportion; thus, 2, 4, 3, 6, usually written thus, 2 : 4 : : 3 : 6 ; the taark : being put for the words, is to, and : : for, as, so that this would he read, "2 is to 4 as 8 is to 6. Here the first is half the second, and the third is half the fowtVi, and they are therefore in proportion; bu< they may be arranged otherwise ant! yet he in proportion, thus, 4 : 2 : : 6 : *. where the first is twice as large as the second, and the third is twice as lane as tfce fourth. In ali cnses the two middle terms are called the means, and the two oster terms are called fhe extremes. The product of "the two means is equal to that of the two extremes, thus i the last example, 2x6 = 1-2, and 4x3 = 12. Now, if w wanted ttae last terra, to wit, 3, it couid easily he &ead by 42 means of this property of numbers in proportion. If we h;*4 only three terms given, ns 4 : 2 : 6, to find the fourth in proportion, which is the last extreme, and 4 is the nrst extreme. Now, we must lind $uh a number, that, when multiplied by 4, the product will be equal to the product of the means ; 2x6=12, to find such a number we have only, by the definition of division, to divide the product of the two means, viz. 12 by the first extreme 4, and the quotient 3 will be the answer. So universally 6:9:: 12: where the last term will be found, as before, by multiply ing- the two means 12x9=108, and dividing the product 108 by the first extreme 6, the quotient will be the last extreme 18, hence 6:9:: 12,: 18. The rute may be expressed simply thus: let F stand for the first term, S the second, T the third, and the last, then we have = , and this r rule holds true whether the numbers be whole or fractional ; and here it may be observed, that it will in most, if not i all cases, be best to turn all vulgar fractions, when they occur, into deciaials ; thus, 2 : 3 : : 6-1 : or f : V : : V : 2* = - 31 = y = 3-666 ^ 2-5 : 3-666 : : S'25 : >i 5 O.^ "1 "1 2 43 )| = U = 3-666 I % = 6-25 J Here the mode of determining- the fourth term is the same in all; the two means being x, and their product --, by the first term. This is usually called the rule of three, and is of the utmost utility in practical arithmetic. We shall now show how it is to be applied. If we pay 40 pence for 2 feet of wood, how much will we pay for 6 feet at the same rate ? Here it is clear we will pay in proportion to the quantity of wood ; for as many times as we have 2 feet, \ve will pay so many times 40 pence ; that is, the price will be in proportion to the quantity of wood. So that we may say,, as the one quantity of wood is to another quantity, so will be the price of the first quantity to the price of the second. Hence the terms in the question; will stand arranged thus : 2 : 6 :: 40 : 120, which term 120 is the price oi' 6 feet, and is found by the rule given above t 57. In every question in simple proportion, there wiB always be thsee terras, one of *vbtth io tlve same kind COMI'Ut Mi) I'KOI'OUTION. 4J with the answer sought, whether it be money, measure, time, force, or any thing, which term in the question we put in the third place ; :i< in the h^t question the answer w:is to be money, and therefore the money in the question, 40 pence, was placed as the third term. When this is done, we next consider whether the answer will be greater or less than the third term, and place the greater or less of the other two terms next it in the second place, and the other one first, as the answer may require ; after which, employ the rule given above to find the answer. 58. As, for ex'ample, 40 men will'do a piece of work in 15 days, in how many days will 20 men do the same? Here the answer must be days ; consequently, 15 goes in the third term, and 20 men will take more time than 40 to do it, therefore we must put the greatest in the second place, and the least in the first ; and it therefore stands thus : 20 : 40 : : 15 : the answer 30, which is found by the rule. 40X15 ^30. COMPOUND PROPORTION. 51 COMPOUND PROPORTION depends entirely on the sam principles as simple proportion. For instance, if 2 feet of fir cost 40 pence, what will G feet of mahogany cost, 3 feet of mahogany being equal in value to 9 of fir. Here we may find the price of the 6 feet of mahogany as if they were fir, and it comes out, by the last article, 120 pence, but 3 is to 9 as the price of fir is to that of mahogany ; therefore we put the 120, the price of 6 feet of fir, in the third term, and state the proportion, 3:9:: 120 : 360, the price of 6 feet of mahogany. The same would have been more easily found by stating it thus : 6 : 54 : : 40 : 360. Ans. where the proportion/ are stated under each other, and multiplied together, which produces 3x2 = 6 and 6x9 = 54, two terms of a new proportion, in the simple rule, where 4( is the third term ; and this is only the particular example of a general rule, where we may have as many 44 ARITHMETIC. proportions as we please reduced to the form of a simple question in the rule of three. As, therefore, that quantity which is of the same kind with the required answer is put in the third term, the rest will be found to go in pairs ; two expressing relation of price, two relation of quality, two relation of time, which must be put in proper order in the first and second terms, as directed for simple propor- tion. When this is done, all the first terms of these several proportions are to be multiplied together for a new first erm, all the second terms together for a new second term, which being placed with the third, in the form of simple proportion, and operated upon as there directed, will give the answer. Forty boys are set to dig a trench in summer ; 14 spade- fuls can be dug in summer for 12 in winter; 6 men can do as much as 13 boys ; and 16 men can do it in 104 days in winter : how long will the boys take ? Here the answer is to be, how many days? We have in the question 104 days ; the third term, relative of difficulty, 14 spadefuls and 12 spadefuls ; of strength, 6 men to 13 boys ; relation of numbers, 16 to 40 ; which will be stated thus : Relation of number, 40 : 16") makes the timeless. Relation of difficulty, 14 : 12 y :: 104 makes the time less. Relation of strength, 6:13J makes the time greater Product, 3360 : 2496 : : 104 : 77 T V F days, Ans. ARITHMETICAL AND GEOMETRICAL PROPORTIONS AND PROGRESSIONS. 60. THE subject of this chapter is often referred to in elementary books on mechanical science ; and for this rea- son, we shall draw the attention of the reader, for a little while, to the subject. 61. When we inquire as to the difference of two num- bers, we inquire for their arithmetical ratio ; but when we inquire as to the quotient of two numbers, we inquire for their geometrical ratio. Thus, 12 3 = 9 and 12 -j- 3 = 4 ; here 9 is the arithmetical ratio of 12 and 3, and 4 is the geometrical ratio of the same numbers. From this it will be seen, that ratio and relation are terms which have the same signification. PROPORTIONS AND PROGRESSIONS. 45 62. When four numbers follow each other, and are such that the difference of the first two is the same as, or equal lo, the difference of the last two, these numbers are said to be in arithmetical proportion; thus the numbers 12, 7, 9, 4, form an arithmetical proportion, because the difference of 12 and 7 is the same as the difference of 9 and 4, both being 5. The numbers in an arithmetical proportion may be varied in their position, but still the result will be an arith- metical proportion ; for instance, 12, 7, 9, 4, may h.e written 12, 9, 7, 4, or 9, 12, 4, 7 : but the most remarkable pro- perty of arithmetical proportion is this, that the sum of the first and last terms is always equal to the sum of the second and third ; thus, 12 + 4 = lt> and 9 + 7 = 16; and from this it evidently follows, that to find the fourth term, we add the second and third terms together," and from their sum subtract the first; the remainder is the fourth term. 63. An arithmetical progression is a series of numbers such, that, in taking any three numbers in succession, the difference of the first and second is the same as the differ- ence of the second and third ; thus, 1, 2, 3, 4, 5, 6, 7, 8, or 14, 12, 10, 8, 6, 4, 2, where the difference of the succeeding numbers in the first is 1, and in the second 2. As the num- bers in the first increase from the beginning, it is called an increasing arithmetical series, or progression, and as they decrease, from the beginning, in the second example, it is called a decreasing arithmetical progression, or series. 64. Let us place any one of these progressions above itself, in this manner : 2 14 4 12 6 8 8 10 6 12 4 14 2 16 16 16 16 16 16 16 writing the same progression as increasing and decreasing 1 the respective terms of the one being directly under the re spective terms of the other in columns, as above, the lowest line of the three being the sums of the several columns, which are all seen to be 16. Now, it will be obvious, that the first column consists of the first and last terms of the series, 2, 4, 6, A H APPENDIX TO GEOMETRY. INSTRUMENTS. 28. To facilitate the construction of geometrical figures we add a short description of a few useful instruments which do not belong to the common pocket-case. 29. Let there be a flat ruler, AB, from R one to two feet in length, for which the comnjon Gunter's scale may be substi- tuted ; and, secondly, a triangular piece of wood, , 6, c, flat, and about the same thickness as the ruler : the sides ab and V of which are equal to one another, and form a right angle at b. For the convenience of sliding, there is usually a hole in the middle of the triangle, as may be seen in the figure. 30. By me#ns of these simple instruments many very useful geometrical problems may be performed. Thus, to draw a line through a given point parallel to a given line. INSTRUMENTS. 51 Lay the triangle on the* paper so that one of its sides will coincide with the given line to which the parallel is to be drawn ; then, keeping the triangle steady, lay the ruler on the paper, with its edge applied to either of the other sides of the triangle ; then; keeping the ruler firm, move the tri- angle along its edge, up or down, to the given point ; the side of the triangle which was placed on the given line will always keep parallel to itself, and hence a parallel may be drawn through the given point. 31. To erect a perpendicular on a given line, and from any given point in that line, we have only to apply the ruler to the given line, and place the triangle so, that its right angle shall touch the given point in the line, and one of the sides about the right angle, placed to the edge of the ruler the other side will give the perpendicular required. 32. If the given point be either above or below the line, the process is equally easy. Place one of the sides of the triangle about the right angle on the given line, and the ruler on the side opposite the right angle, then slide the tri- angle on the edge of the ruler till the given point from which the perpendicular is to be drawn is on the other side, then this side will give the perpendicular. 33. Other problems may be performed with these instru- ments, the method of doing which it will be easy for the reader to contrive for himself. 34. When arcs of circles of great diameter are to be drawn, the use of a compass may be substituted by .a very simple contrivance. Draw the chord of the arc to be de- scribed, and place a pin at each ex- tremity, A and B, then place two rulers jointed at C, and forming an angle, ACB = the supplement of half the given number of degrees ; that is to say, the number of degrees which the arc whose chord given is to contain, is to be halved, and this half being sub- tracted from 180 degrees, will give the degrees whicli form the angle at which the rulers are placed, that is; the angle ACB. This being done, the edges of the rulers are moved along against the pins, and a pencil at C will describe the arc required. 35. Large circles may be described by a contrivance equally simple. On an axle, a foot or a foot and a half 82 GEOMETRY. long, there are placed two wheels, M and F, of which one is fixed to the axle, name- ly, M, and the other is capable of being shifted to different parts of the axle, and, by means of a thumb-screw, made capable of being fixed at any point on the axle. These wheels are of different diameters, say of 3 and 6 inches, the fixed wheel F being the largest. This instru- ment being moved on the paper, the circles M and F will roll, and describe circles of different radi . the axle will al- ways point to the centre of these circle*, and there will be this proportion : As the diameter of the larg-e wheel Is to the difference of the diameters of the two wheels, So is the radius of the circle to be described by the large wheel To the distance of the two wheels on the axle. 36. If the diameters of the wheels are as above stated, and it is required to describe a circle of 3 feet radius, then from the above proportion we have 6:6 3 : : 3 feet or 36 inches : 18 inches = the distance of the two wheels, to describe a circle 6 feel in diameter. 37. It may be observed, that it will be best to make the difference of the wheels greater if large circles are to be de- scribed, as then a shorter instrument will serve the purpose. 38. We will conclude this appendix, by making a few remarks on the Diagonal Scale and Sector, the great use of the lattei jf which, especially, is seldom explained to the young mechanic. 39. The diagonal scale to be found on the plain scale in common pocket-cases of instruments, is a contrivance for measuring very small divisions of lines ; as, for instance, hundredth parts of an inch. 40. Suppose the accompanying cut to E A represent an enlarged view of two di- visions of the diagonal scale, and the bottom and top lines to be divided into two parts, each representing the tenth part of an inch. Now, the perpendicular lines BC, AD, are each divided into ten equal parts, which are joined by the crossing lines, 1, 2, 3, 4, &c., and the diagonals BF, DE, INSTRUMENTS. 83 nre drawn as in the figure. Now, as the division FC is the tenth part of an inch, and as the line FB continually approaches nearer and nearer to BC, till it meets it in B, it will follow, that the part of the line 1 cut off by this diagonal will be a tenth part of FC, because Bl is only one- tenth part of BC ; so, likewise, 2 will represent two-tenth parts, 3, three-tenth parts, and so on to 9, which is nine- tenth parts, and 10, ten-tenth parts, or the whole tenth of an inch ; so that, by means of this diagonal, we arrive at divisions equal to tenth parts of tenth parts of an inch, or hundredths of an inch. With this consideration, an exami- nation of the scale itself will easily show the whole matter. It may be observed, that if half an inch and the quarter of an inch be divided, in the same manner, into tenths and tenths of tenths, we may get thus two-hundredth and four- hundredth parts of an inch. THE SECTOR. 41. THIS very useful instrument consists of two equal rulers each six inches long, joined together by a brass folding joint. These rulers are generally made of boxwood or ivory; and on the face of the instrument, several lines or scales are engraven. Some of these linjes or scales pro- ceed from the centre of the joint, and are called sectorial lines, to distinguish them from others which are drawn parallel to the edge of the instrument, similar to those on the common Gunter's scale. 42. The sectorial lines are drawn twice on the same face of the instrument; that is to say, each line is drawn on both legs. Those on each face are, A scale of equal parts, marked L, A line of chords, marked C, A line of secants, marked S, A line of polygons, marked P, or Pol. These sectnrial lines are marked on one face of the instru- ment; and on the other there are the following: A line of sines, marked S, A line of tangents, marked T, A line of tangents to a less radius, marked L 84 GEOMETRY. Tins last line is intended to supply the defect of the former and extends from about 45 to 75 degrees. 43. The lines of chords, sines, tangents, and secants, but not the line of polygons, are numbered from the centre, and are so disposed as to form equal angles at the centre ; and it follows from this, that at whatever distance the sec- tor is opened, the angles which the lines form, will always be respectively equal. The distance, therefore, between 10 and 10, on the two lines marked L, will be equal to the distance of 60 and 60 on the two lines of chords, and also to 90 and 90 on the two lines of sines, &c., at any particu- lar opening of the sector. 44. Any extent measured with a pair of compasses, from the centre of the joint to any division on the sectorial lines, is called a lateral distance; and any extent taken from a point in a line on the one leg, to the like point on the similar line on the other leg, is called a transverse or parallel distance. With these remarks, we shall now proceed to explain the use of the sector, in so far as it is likely to be serviceable to mechanics. USE OF THE LINE OF LINES. 45. This line, as was before observed, is marked L, and its uses are, To Divide a line into any number of equal parts : Take the length of th^line by the compasses, and placing one of the points on that number in the line of lines which denotes the number of parts into which the given line is to be divided, open the sector till the other point of the com- passes touches the same division on the line of lines marked on the other leg ; then, the sector being kept at the same width, the distance from 1 on the line L on the one leg, to 1 on the line L on the other, will give the length of one of the equal divisions of the given line to oe divided. Thus, to divide a given line into seven equal parts : take the length of the given line with the compasses, and setting one point on 7, on the line L of one of the legs, move the other leg out until the other point of the compasses touch 7 on the line I, of that leg ; this may be called the trans- verse distance of 7 on the line of lines. Now, keeping the sector at the same opening, the transverse distance of 1 will be the length of one of the 7 equal divisions of the INSTRUMENTS. f>5 giver line ; the transverse distance of 2 will be two of these divisions, &c. 46. It will sometimes happen, that the line to be divided will be too long for the largest opening of the sector ; and in this case we take the half, or third, or fourth of the line, as the case may be ; then the transverse distance of 1 to 1, will be a half, a third, or a fourth of the required equal part. 47. To divide a given line into any number of parts that shall have a certain relation or proportion to each other: Take the length of the whole line to be divided, and placing one point of the compasses at that division on the line of lines on one leg of the instrument which expresses the; smn of all the parts into which the given line is to be divided, and open the sector till the other point of the compasses is on the corresponding division on the line of lines of the other leg. This is evidently making the sum of the parts into which the given line is to be divided a transverse distance; and when this is done, the proportional parts will be found by taking, with the same opening of the sector, the transverse distances of the parts required.- To divide a given line into three parts, in the proportion of 2, 3, 4: The sum of these is 9; make the given line a transverse distance between 9 and 9 on the two lines of lines; then the transverse distances of the several numbers 2, 3, 4, will give the proportional parts required. 48. To find a fourth proportional to three given lines: Take the lateral distance of the second, and make it the transverse distance of the first, then will the transverse dis- tance of the third be the lateral distance of the fourth; then, let there be given 6:3:: 8, make the lateral distance of 3 the transverse distance of 6 ; then will the transverse distance of 8 be the lateral distance of 4, the fourth propoi- tional required. 49. This sector will be found highly serviceable in draw- ing plans. For instance, if it is wished to reduce the draw- ing of a steam engine from a scale of 1^ inches to the foot, to another of f to the foot. Now, in lg inches there are */ parts; so that the drawing will be reduced in the propor- tion of 12 10 5. Take the lateral distance of 5, and keep the compasses at this opening ; then open the sector till the points of the compasses mark the transverse distance of 12 ; keep now the sector at this opening, and any measure taken on the drawing, to be copied and laid off on the sector as a 8 86 MECHANICAL DRAWING lateral distance, the transverse distance taken from that point will give the corresponding measure to be laid down in the new drawing. 50. If the length of the side of a triangle, of which we have the drawing, is to he reckoned 45 ; what are the lengths of the other two sides ? Take the length of the side given, by the compasses, and open the sector till the measure be the transverse distance of 45 to 45 ; then the lengths of the other sides being applied transversely, will give their numerical lengths. USE OF THE LINE OF CHORDS. 51. By means of the sector, we may dispense with the protractor. Thus, to lay down an angle of any number of degrees: take the radius of the circle on the compasses, and open the sector till this becomes the transverse distance of 60 on the line of chords ; then take the transverse dis- tance of the required number of degrees, keeping the sec- tor at the same opening; and this transverse distance being marked off on an arc of the circle whose radius was taken, will be the required number of degrees. We will not enter farther on the use of the sectorial lines, as what we have said will, we hope, be found sufficient for the purposes of the practical mechanic. MECHANICAL DRAWING AND PERSPECTIVE. 52. A FLAT rectangular board is first to be provided, of any 'convenient size, as from 18 to 30 inches long, and from 16 to 24 inches broad. It may be made of fir, plane tree, or mahogany ; its face must be planed smooth and flat, and the sides and ends as nearly as possible at right angles to each other the bottom of the board and the left side should be made perfectly so ; and this corner shouL! be marked, so that the stock of the square may be always applied to the bottom and left hand side of the board. To prevent the board from casting, it is usual to pannel it on the back or on the sides. 53. A T square must also be provided, such that by AND PERSPECTIVE. 87 means of a thumb-screw fixed in the stock, it may be made to answer either the purposes of a common square, or bevel, the one-half of the stock being movable about the screw, and the other fixed at right angles on the blade. The blade ought to be somewhat flexible, and equal in length to the length of the board. 54. Besides these, there will be required a case of mathe- matical instruments ; in the selection of which it should be observed, that the bow compass is more frequently defect- ive than any of the other instruments. After using any of the ink feet, they should be dried ; and if they do not draw properly, they ought to be sharpened and brought to an equal length in the blade, by grinding on a hone. 55. The colours most useful are, Indian ink, gamboge, Prussian blue, vermilion, and lake. With these, all colours necessary for drawing machinery or buildings may be made ; so that, instead of purchasing a box of colours, we would advise that those for whom this book is intended should procure these cakes separately : the* gamboge may be bought from an apothecary a pennyworth will serve a lifetime. In choosing the rest, they should be rubbed against the teeth, and those which feel smoothest are of the best quality. 56. Hair pencils will also be necessary, made of camel's hair, and of various sizes. They ought to taper gradually to a point when wet in the mouth, and should, after being pressed against the finger, spring back. 57. Black-lead pencils will also be necessary. They ought not to be very soft, nor so hard that their traces can- not be easily erased by the Indian rubber In choosing paper, that which will best suit this kind of drawing is thick, and has a hardish feel, not very smooth on the sur- face, yet free from knots. 58. The paper on which the drawing is to be made, must be chosen of a good quality and convenient size. It is then to be wet with a sponge and clean water, on the opposite side from that on which the drawing is to lie made. When the paper absorbs the water, which may be seen by the wetted side becoming dim, as its surface is viewed slantwise against the light, it is to be laid on the drawing board v/ith the wetted side next the board. About half an inch must be turned up ou a straight edge all round the paper 88 MECHANICAL DRAWING and then fastened on the board. This is done because th paper when wet is enlarged, and the edges being fixed or. the board, act as stretchers when the paper contracts by drying. To prevent the paper from contracting before the paste has been sufficiently fastened by drying, the paper is usually wet on the upper surface, to within half an inch of the paste mark. When the paper is thoroughly dried, it will be found to lie firmly and equally on the board, and is then fit for use. 59. If the drawing is to be made from a copy, we ought first to consider what scale it is to be drawn to. If it is to be equal in size to, or larger than the copy ; and a scale should be made accordingly, by which the dimensions of the several parts of the drawing are to be regulated. The diagonal scale, a simple and beautiful contrivance, will be here found of great use for the more minute divisions ; and whenever the drawing is to be made to a scale of 1. inch, inch, | inch to the foot, a scale should be drawn of 20 or 30 equal parts ; the last of which should be subdirided into 12, and a diagonal scale formed on the same principles as the common one, but with eight parallels and 12 diagonals, to express inches and eighths of an inch. For making such scales to any proportion, the line L on the sector will be found very convenient. 60. Great care should be taken in the penciling, that an accurate outline be drawn, for on this much of the value of the picture will depend. The pencil marks should be distinct, yet not heavy, and the use of the rubber should be avoided as much as possible, as its frequent application ruffles the surface of the paper. The methods already given for constructing geometrical figures will be here found applicable, and the use of the T square, parallel ruler, &c., will suggest themselves whenever they require to be employed. 61. The drawing thus made of any machine or building is called a plan. Plans are of three kinds a ground plan, or bird's-eye view, an elevation or front view, and a per- spective plan. 62. When a view is taken of the teeth of a wheel, with the circumference towards the eye, the teeth appear to be nearer as they are removed from the middle point of the circumference opposite the eye, and it may not be out of AND PERSPECTIVE. , 89 place here to give the method of representing them on paper: IfABbe the circumference of a wheel as viewed by the eye, and it is ^T required to represent the teeth as they appear on it. Only half of the circum- ference can be seen in this way at one time, consequently we can only represent the half of the teeth. On AB describe a semicircle, which divide into half as many equal parts as the wheel has teeth ; then from each of these points of division draw perpendiculars to the wheel AB, then will these perpendiculars mark the relative places of the teeth. 63. When the outline is completed in pencil, it is next to be carefully gone over with Indian ink, which is to be rubbed down with a little water, on a plate of glass 01 earthenware so as to be sufficiently fluid to flow easily out of the pen, and at the same, time have a sufficient body of colour. While drawing the ink lines, the measurement should all be repeated, so as to correct any error that may have slipped during the penciling. The screw in the drawing pen will regulate the breadth of the strokes ; which should not be alike heavy ; those strokes being the heaviest which bound the dark part of the shades. Should any line chance to be wrong drawn with the ink, it may be taken out by means of a sponge and water, which could not be done if common writing ink were employed. 65. In preparing for colouring it is to be observed, that a hair pencil is to be fixed at each end of a small piece of wood, made in the form of a common pencil, one of which is to be used with colour, and the other with water only. If the colour is to be laid on, so as to represent a flat sur- face, it ought to be spread on equally, and there is here no jise for the water brush ; but if it is to represent a curved surface, then the colour is to be laid on the part intended .o be shaded, and softened towards the light by washing with the water brush. In all cases it should be borne in *nind, that the colour ought to be laid on very thin, other- wise it will be more difficult to manage, and will never make so fine a drawing. 66. In colours even of the best quality, we sometimes meet with gritty particles, which it is desirable to avoid Instead of rubbing the colour on a plate with a little water 8* 90 MECHANICAL DUAWING as is usual, it will be better to wet the colour, and rub it on the point of the forefinger, letting the dissolved part drop off the finger on to the plate. 67. In using the Indian ink, it will be found advanta- geous to mix it with a little blue and a small quantity of lake, which renders it much more easily wrought with, and this is the more desirable as it is the most frequently used of all the other colours in Mechanical Drawing, the shades being all made with this colour. The depth and extent of the shades will depend on various circumstances on the figure of the .object to be shaded, the position of the eye of the observer, and the direction in which the light comes, = Leo#* of side. 7 Heptagon 51 : 128* 3-6339124 1-11 867 1-16 8 Octagon 45' 135 4-8284271 1-08 765 1-307 9 Nonagon 40 140 6-1818242 1-062-681 1-47 10 Decagon 36 144 7-6942088 1-05 616 1-625 11 Urulecagon 32 T 8 T 147J\ 9-3656405 1-04 561 1-777 12 Dodecagon 30 150 11-1961524 1-037 515625 1-94 1 102 MENSURATION. The first column of this table gives the number of sides of the polygon ; the second, the name ; the uses of the third and fourth will be explained in the note at the bottom of the page,* and the uses of the rest will appear by the fol- lowing rules and examples. The answers found are only approximate, but come sufficiently near the truth for all practical purposes. Side of polygon 3 x No. column AREA = area. Ex. In *a figure of 10 equal sides, the length of one side being 8, we have 8' 2 = 8 x 8 = 64 ; hence 64 X 7-6942088 = 492-4293632 = the area. Take the length of a perpendicular, drawn from the centre to one of the sides of a polygon, and multiply this by the numbers in column A, the product will be the radius of the circle that contains the polygon. Ex. If the length of a perpendicular drawn from the centre to one of the sides of an octagon be 12, then 12 x 1*08 = 12-96 = radius of circumscribing circle. The radius of a circle multiplied by the number in column B, will give the length of the side of the correspond- ing polygon which that circle will contain. Suppose, for an octagon, the radius of a circle to be 12-96, then 12-96 X '765 = 9-9144 = the length of one side of the inscribed polygon of 8 sides. The length of the side of a polygon multiplied by the corresponding number in the column C, will give the radius of circumscribing circle. Thus the length of one side of a decagon being 10; then 10 x 1'625 = 16-25 = radius of circumscribing circle. 6. For the circle. 1st, diameter X 3-1416 = circumference; * The third and fourth columns of the table of polygons will greatly facilitate the construction of these figures by the aid of the sector. Thus, if it be required to describe a polygon of eight sides, then look in column Angle F, opposite Octagon, and you find 45. With the chord of 60 on the sector as radius describe a circle, then taking the length 45 on the same line of the sector, mark this distance off on the circumference, which being repeated round the circle, will give the points of junction of the sides cf the octagon. The fourth column of the table gives the angle in degrees, which any < wo adjoining sides of the respective figurei make with each other. MENSURATION. 103 , circumference 2) (A-BxV) , . . . - - = the velocity of A after the stroke. A-f-r> _ the velocity of B after the stroke. A+L* PARALLELOGRAM OF FORCES. 19 2 X V = the velocity of A after the stroke. X V = the velocity of B after the stroke. A + B 2 A A x B Ex. If the weight of an elastic body A be 6 Ibs., and its velocity 4, and the weight of another body B be 4 Ibs., and its velocity 2; then we have these results: in the first case, (2x4x2) + (6 4x4) , . , . = -8 = velocity of A alter the stroke. 6 + 4 (2x6x4) + (6 4X2) i = 5-2 velocity of B after the stroke. The sum of these two velocities, viz. 5-2 and -8 = 6, which was the sum of the velocities 2 and 4 before the stroke ; and this is a general law. The reader may exercise him- self with the rules for the other cases. It is to be observed, that when non-elastic bodies, that is, bodies which have no spring, strike, they will both move in the direction of the motion of that body which has the greater momentum ; but if they are elastic, they will recoil after the stroke, and move contrary ways. THE COMPOSITION AND RESOLUTION OF FORCES. j IF a body be acted upon By two forces, one of which would cause it to move from A to B in any given time, and the other would cause it to move from A to C m 12! MECHANICS the same time ; then if these forces act upon the body at one instant, it will move in neither .of the lines AB, AC, but in the line AD, which is the diagonal of the parallelo- gram of which the two lines AB and AC are containing sides ; and by the action of the two forces, the body will be found at D, at the end of the time that it would have, been found at B or C, by the action of either of the forces singly This important fact in mechanical science, is usually called the parallelogram of forces. From this statement it will be seen, that if we have the quantity and direction of any two forces urging a body at the same instant, we can find the resulting motion, both in quantity and direction. It will not be difficult to understand, that if the two forces which act upon a body, act not at an angle, but in the same straight line, and in contrary directions, the resulting motion will be in that straight line, and in the direction of the greater force ; but if the forces be equal, the body will remain at rest. If, while a body A is urged by a force in the direction AB, which would carry it to A, it be acted on by another force in the direction AC which would carry it to C, and a third force in the direction DA, which would carry it over a space as great as that from D to A, these being the sides and diagonals of a parallelogram, the body A will remain at rest. Also, if a body A has a tendency to move in the direction AB, but is counteracted by a force DA, and if we wish to keep the body A from moving, altogether, we must apply another force AC, forming the other side of the parallelogram of which AB is one side and AD the diagonal. If there be three forces acting on a body at the same time, make the sides of a parallelogram represent any two of them ; then the diagonal of this parallelogram, together with the third force as the two sides of another parallelo- gram, will give a diagonal which will be the result of the three forces acting* at once on the body. If the two forces which urge the body, both produce a uniform motion, the resulting motion will be in a straight line; tout if one of them act by impulse, which would pro- duce a uniform motion, and the other act constantly so as to produce an accelerated motion, the resulting motion will be in a curve. Thus, if the ball of a cannon were sent in a horizontal direction, it would never deviate from this straight line unless acted on by some external force. The THE LEVER. 12} force of gravity acts on the body constantly, so as to draw it to the earth, by a uniformly accelerated motion ; and the result is, that the ball will move in a curve, and this curve may bo easily shown to be that of the parabola. The re- sistance of the air being taken into account together with these circumstances, constitute the basis of the science of gunnery. We shall give a simple example, to show the application of the former part of this subject. One force will cause the body A to move 20 miles in a day, and another, acting at right angles, will cause it to move 18 miles a day; draw these lines 20 and 18 from the line of lines on the sector, as the sides AB, AC, of a parallelogram, and complete it: draw the diagonal, then measure it, and it will be found to be 26'9, the resulting motion ; and the angle being measured, will give the direction. There are other methods of doing this by calculation, but this is simple, and is suffi- cient to show the principle. MECHANICAL POWERS. 1. A MACHINE is any instrument employed to regulate motion, so as to save either time or force. No instrument can be employed by man so as to save both time and force ; for it is a maxim in mechanics, that whatever we gain in the on" of these two, must be at the expense of the other. 2. The simple machines, or those of which all others are constructed, are usually reckoned six : the lever, the wheel and axle, the pulley, the inclined plane, the wedge, and the screw. To these the funicular machine is sometimes added. 3. The weight signifies the body to be moved, or th resistance to be overcome ; and the power is the force em ployed to overcome that resistance, or move that body They are frequently represented by the first letters of theii .names, W and P. THE LEVER. 4. A LEVER is an inflexible bar, either straight or bent, supposed capable of turning round a fixed point, called the fulcrum 1] 122 MECHANICS. According to tho relative positions of tho weight, power and fulcrum, on the lever, it is said to be of three kinds, viz. when the fulcrum is somewhere betwixt the weight and power, it is of the first kind ; when the weight is between the power and the fulcrum, it is of the second kind ; and when the power is between the weight and the fulcrum, it is of the third kind : thus, 5. 1st. - 6. 3d. 7. 3d. 8. In the first and second kinds there is an advantage of power, but a proportionate loss of velocity ; and in the third kind, there is an advantage in velocity, but a loss of power. 9. When the weight X its distance from the fulcrum = the power x its distance from the fulcrum, then the lever will be at rest, or in equilibrio ; but if one of these pro- ducts be greater than the other, the lever will turn round the fulcrum in the direction of that side whose product is the greater. 10. In all the three kinds of levers, any of these quanti- ties, the weight or its distance from the fulcrum, or, the power or its distance from the fulcrum, may be found from the rest, such, that when applied to the lever, it will remain at rest, or the weight and power will balance each other. weight X its dist. from fulc. 11. -re 2 7 TT-J = power. dist. of power from fulc. power x its dist. from fulc. dist. of weight from fulc. , weight x dist. weight from fulc. 13. =dist. power from ful. power powerxdist.power from fulc. .. 14. =dist. weight from fulc. weight. 15. In the first kind of lever, the pressure upon the ful- crum = the sum of weight and power; in the second and third = their difference. 16. If there be several weights on both sides of the ful- crum, they may be reckoned powers on the one side of the fulcrum, and weights on the other. Then, if the sum of the product of all the weights x their distances from tho THE LEVER. 123 fulcrum he = to the sum of the products of all the power* X their distances from the fulcrum, the lever will be at rest, if not, it will turn round the fulcrum in the direction of that side whose products are gre;>: 17. In these calculations, the weight of the lever is not taken into account ; but if it is, it is just reckoned like any other weijrht or power acting at the centre of gravity. 18. When two, three, or more levers act upon each other in succession, then the entire mechanical advantage which they give, is found by taking the product of their separate advantages. 19. It is to be observed, in general, before applying these observations to practice, that if the lever be bent, the dis- tances from the fulcrum must be taken, as perpendiculars drawn from the lines of direction of the weight and power to the fulcrum. Ex. In a lever of the first kind, the weight is 16, its distance from the fulcrum 12, and the power is 8 ; there- fore, by No. 13 of this chapter, = 24, the distance of power from the fulcrum. 8 In a lever of the second kind, a power of 3 acts at a distance of 12 ; what weight can be balanced at a distance of 4 from the fulcrum ? Here, by No. 12, 3 x 12 o w ' = 9, weight. In a lever of the third kind, the weight is 60, and its dis- tance 12, and the power acts at a distance of 9 from the fulcrum.; therefore, by No. 11, 60 X 12 . = 80, the power required. if If there be a lever of the first kind, having three weights, 7, 8, and 9, at the respective distances of 6, 15, and 29, from the fulcrum on one side, and a power of 17 at the dis- tance of 9 on the other side of the fulcrum ; then a power is ,to be applied at the distance of 12 from the fulcrum, on the last mentioned side : what must that power be to keep the l^ver in balance ? Here (6 x 7) + (15 x 8) + (29 x 9) = 423 = the effect of the three weights on the one side of the ful- crum ; and 17 X 9 = 153 = the effect of the power on the other side. Now, it is clear that the effect of the weight is 124 MECHANICS. far grei ter than the effect of the power ; and the difference 423 1 53 = 270 requires to be balanced by a power ap- plied at the distance of 12, which will evidently be found by dividing 270 by 12, which gives 22'5, the weight re- quired. 20. The Roman steel-yard is a lever of the first kind, so contrived that only one movable weight is employed. The common weighing balance is also a lever of the first kind. The requisites of a good balance are : that the points of suspension of the scales and the centre of motion, or ful- crum of the beam, be all in one straight line that the arms of the beam be equal to each other in every respect that they be as long as possible that the centre of gravity of the beam be a very little below the centre of motion that the beam be balanced when the scales are empty, &c. But we may ascertain the true weight of any body even by a false balance, thus : weigh the body first in one scale, then in the other, and multiply their weights together ; then the square root of this product will be the true weight. THE WHEEL AND AXLE. 21. THE wheel and axle is a kind of lever, so contrived as to have a continued motion about its fulcrum, or centre of motion, where the power acts at the circumference of the wheel, whose radius may be reckoned one arm of the lever, the length of the other arm being the radius of the axle, on which the weight acts. If the power acts at the end of a handspike fixed in the rim of the wheel, then this in- creases the leverage of the power, by the length of the handspike. The wheel and axle consists of a wheel having a cylindric axis passing through its centre. The power is applied to the cir- cumference of the wheel, and the weight to the circumference of the axle. In the wheel and axle, an equilibrium takes place when the power multiplied by the radius of the wheel, is equal to the weight multiplied by the radius of the axle ; or, P : W : : CA. : CB. For the wheel and axle being nothing else but a lever so contrived as to have a continued motion about its ful- THE WHEEL AND AXLE. 125 cnim C, the arms of which may be represented by AC and BC, therefore, by the property of the lever, P : W : : CA :CB. If the power does not act at right angles to CB, but obliquely, draw CD perpendicular to the direction of the power, then, by the property of the lever, P : W : : CA : CD. 22. It will be easily seen, that if two wheels fastened together and turning round the same centre, be so adjusted, that while they turn round they will coil on their cir- cumferences strings, to which weights are suspended ; one of those wheels being larger than the other, the larger wheel will coil up a greater length of the string than the smaller one will do in the same time, and this will depend either on the radii or circumferences of the two wheels. The velocity of the weight will be in proportion to the length of string coiled in a given time ; therefore, the ve- locity of the weight will be greater as the wheel is larger. Now, as in the lever we saw that a small weight required a great velocity to balance a large weight with a small velo- city, we may infer, that the rules given for levers will also apply to the wheel and axle ; since the velocity of any body on a lever depends upon its distance from the fulcrum. Ex. A weight of 13 Ibs. is to be raised at a velocity of 14 feet per second, by a power whose velocity is 20 feet per second ; how great must that power be ? 13x14 -- = 9-1, the power required. If the velocity of the weight, be to that of the power, as 14 to 20, and the radius of the axle on which the weight is coiled be 7 ; then, 20 x 7 = 10, radius of wheel on which the power acts. If a weight of 36 Ibs, is to be raised by an axle 3 inches diameter ; what must be the power applied at the end of a handspike 4 inches long, fixed in the rim of the wheel con- nected with the axle, the wheel being 6 inches diameter ? /Here the handspike will increase the distance of the power from the fulcrum, and will add to the diameter of th wheel twice its own length ; therefore, 8 -f- 6 = 14 ; hence, ] 4 : 3 : : 36 : 7'77, the power required to keep the weight in equilibrio. 11* 126 MECHANICS. 23. Wheels acting on each other by teeth or bands, may be easily calculated in the same way. Thus, if a wheel which has 30 teeth, drives another of 10 teeth, it is evident, that as the larger wheel has three times as many teeth as the smaller, the smaller wheel will be turned round three times for once that the larger one is turned round ; so that the velocities of the wheels will be inversely as their num- ber of teeth. In like manner, it is clear, that if the larger wheel drives the smaller not by teeth but by a band, their revolutions will be inversely as their circumferences. Ex. The number of teeth in one wheel are 160, and in another driven by it are 20, and the larger wheel makes 12 revolutions in a minute ; how many does the smaller one make ? 20 : 160 : : 12 : 96 = the number of turns which the smaller wheel makes in a minute. 24. The larger wheel is usually called the wheel, driver, or leader, and the smaller one is called the pinion, driven wheel, or follower. 25. Let us now see what would be the action of two wheels and a pinion. If the first wheel contains 80 teeth, the pinion 12 teeth, and second wheel 36 teeth. Place the first wheel and the pinion on the same axis, so that they move together, one revolution of the one being in the same time as a revolution of the other, and the pinion drives the second wheel. If the first wheel makes 16 revolutions in a minute, the pinion will do the same, and the pinion drives the second wheel ; therefore, 36 : 12 : : 16 : 5 3 = the velocity of the second wheel. Place these so, that the teeth of the first wheel act in the teeth of the pinion, and these again act in the teeth of the second wheel. If the first wheel make, as before, 16 turns in a minute, then the pinion will make 12 : 80 : : 16 : 106 T 8 ^ = in a minute ; consequently, the revolutions of the second wheel will be 36 : 12 : : 106 T R ? : 35*55 = turns of the second wheel in a minute. 26. When there are a number of wheels A, B, C, D, E, acting on the respective pinions o, b, c, r/, e, as then the effect of the whole may be found thus : if the letters which epresent the wheels and pinions be understood to signify the number of teeth of each, THE WHEEL A>'P AXLE. 127 power xAxBxCxDxE = weight. x6xcxBC, The pressure on the plane (_ J AB. These properties give rise to the following rules : weight X height of plane power = , length 01 plane power x length of plane weight = : , jr-i height of plane weight X base of plane pressure on the plane = length of plane 33. The force with which a body endeavours to descend down an inclined plane, is as the height of the plane. When the power does not act parallel to the plane, then from the angle C of the plane, draw a line perpendicular to the direction of the power's action ; then the weight, the power, and the B * pressure on the plane, will be as AC, CB, AB. When the line of direction of the power is parallel to the plane, the power is least. 34. If two bodies, on two Inclined planes, sustain each other, by means of a string over a pulley, their weights will be inversely as* the lengths of the planes. 35. In the exercises on inclined planes, it is often neces- sary to find the length of the base, and height, or length of the plane. Any two of these being given, the third may be found and this is done on the principle stated in Geo- metr) r , that the hypotenuse 3 of a right-angled triangle (the length of the plane) is equal to the base a + height 3 . Ex. The height of an inclined plane is 20 feet, and its length TOO ; what is the pressure on the plane of a weight of 1000 Ibs.? Here we must first ascertain the base, (100 a 20 2 ) k = 97-98 = the base of the plane ; and from THE INCLINED PLANE. 133 what has been said above, 100 : 1000 :: 97'98 : 979-8 the pressure upon the plane; also 100 : 20 : : 1000 200, the power necessary to keep the body from rolling down the plane. If a wagon of 3 cwt. on an inclined railway of 10 feet to the 100, be sustained by another on an opposite railway of 10 feet to 90 of an incline ; what is the weight of the second wagon ? Here 100 : 90 : : 3 : 2-7 cwt. = the weight oi the second wagon. 36. The space which a body describes upon an inclined plane, when descending on the plane by the force of gravity, is to the space which it would fall freely in the same time, as the height is to the length of the plane ; and the spaces being the same, the times will be inversely in this proportion. Ex. If a body roll down an inclined plane 320 feet long, and 26 feet in height; what space will it pass down the plane in one second, by the force of gravity alone ? 320 : 26 : : 16 : 1-3 foot = the answer. This subject, as connected with railways, will be resumed when we come to treat of friction and railways. THE WEDGE. 37. THE wedge is a triangular prism, formed either of wood or metal, whose great use is to split or raise timber, stones, &c. The circumstances in which it is applied are such that it is not easy to devise a general rule to determine the amount of its action. The wedge has a great advantage over all the other mechanical powers, in consequence of the way in which the power is applied to it, namely, by per cussion, or a stroke, so that by the blow of a hammer, almost any constant pressure may be overcome. THE SCREW. 38. THE screw is a kind of continued inclined plane, being an inclined plane rolled about a cylinder the height of the plane being the distance between the centres of two threads, and its length the circumference ; hence, 12 134 MECHANICAL CENTRES the rule to find the power of a screw pressing either up- wards or downwards, is as the distance between two threads of the screw is to the circumference where the power i? applied : thus., if the distance of the centres of two threads of the screw be | of an inch, and the radius of the hand- spike attached to the screw be 24 inches ; the circumference j>( the screw will be 150J- inches, nearly: therefore, | : 150| : : 1 : 603} ; and if the power applied be 150 Ibs., the force of the screw will therefore be 603 X 150 == 90480 Ibs. 39. REMARKS ON THE MECHANICAL POWERS. The me- chanical powers may be variously modified and applied, but still they form the elements of all machinery. In our calculations of their effects, we have not made allowance for friction, or the resistance arising from one body rubbing against another a subject which will be discussed hereafter. The justice of the remark made before, will now be seen to hold generally, that of the two velocity and power > whatever we gain in the one, we lose in the other ; or, as power and weight are opposed to each other, there will always be an equilibrium between them, when the power X its velocity = the weight x its velocity, that is, when the momentum of the one is equal to the momentum of the other. All the advantage that we can obtain from the mechanical powers, or their combinations, is to raise great weights, or overcome great resistances, and this must be done at the expense of time; or, to generate rapid velocities, as in turning-lathes, or cotton-spinning machinery, and this is done at the expense of power. MECHANICAL CENTRES. 1. THESE are the centres of gravity, oscillation, percus- sion, and gyration. THE CENTRE OF GRAVITY. 2. THERE is a certain point in every body, or system of bodies connected together ; .which point, if suspended, the THE CENTRE OF GRAVITY. 135 body or system of bodies will remain at rest when acted upon by the force of gravity alone ; this point is called the Centre of Gravity. If a body or system of bodies be suspended by any other point than the centre of gravity, such body or system of bodies will move round that point, until the centre of gravity be in a vertical line with the point of suspension. If a body be sustained from falling by two forces, the lines of direction in which these two forces act, will meet in the centre of gravity of the body, or, in the vertical line which passes through it. 3. It is often useful in calculation to consider the whole weight of a body as placed in its centre of gravity, but it is to be remembered, that gravity and weight do not signify the same thing gravity is the force by means of which bodies, if left to themselves, fall to the earth in directions perpendicular to the earth's surface ; weight, on the other hand, is the resistance or force which must be exerted, to prevent a given body from obeying the law of gravity. 4. To find the centre of gravity of any plane figure, me- chanically : Suspend the figure by any point near its edge, and mark the direction of a plumb-line hung from that point, then suspend it from some other point, and mark the direction of the plumb-line in like manner. The centre of gravity of the figure will be in that point where the marks of the plumb-line cross each other. For instance, if we wish to find the centre of gravity of the arch of a bridge, we draw the plan upon paper to a certain scale, cut out the figure, and proceed with it as above directed ; and by means of the plumb-line from the points of sus- pension, its centre of gravity will be found ; whence, by measuring the relative position of this centre in the plan by the scale, we may determine by comparison its position in the structure itself. 5. We can find the centre of gravity of many figures by calculation. 6. The centre of gravity of a line, parallelogram, prism, cylinder, circle, circumference of a circle, sphere, and regular polygon, is the geometrical centre of these figures respectively. ff. To find the centre of gravity of a triangle draw a line from any angle to the middle of the opposite side, then f 13t MECHANICAL CENTRES. of this line from the angle will be the position of the centre of gravity. 8. For a trapezium, draw the two diagonals, and find the centres of gravity of each of the four triangles thus formed, then join each opposite pair of these centres of gravity, and the two joining lines will cut each other in the centre of gravity of the figure. 9. For the cone and pyramid, the centre of gravity is in the axis, at the distance of ? of the axis from the vertex 10. For the arc of a circle, radius of circle X chord of arc - , . = distance of the length ot arc centre of gravity from the centre of the circle. 11. For the sector of a circle, 2 X chord of arc x radius of circle : ? = distance of 3 x length of arc the centre of gravity from the centre of the circle. 12. For a parabolic space, the distance of the centre of gravity from the vertex is of the axis. 13. For a paraboloid, the centre of gravity is f of the axis from the vertex. 14. For two bodies, if at each end of a bar a weight be hung, the common centre of gravity will be in that point which divides the bar, in the same ratio that the weights of the bodies bear to each other, and this point will be nearest the heavier body. Examples. If the line drawn from the middle of the base of a triangle to the opposite angle be 15, then we have 15 X 2 = 10 = the distance of the centre of gravity from o the vertical angle. If the height of a cone be 24 inches, then we have 24 X 3 = 18 = the distance of the centre of gravity from the vertex. If the length of the arc of a circle be 157-07, and the chord 153-07, and radius 200 ; then, 200 X 153-07 1 ^7-07 == "***" = distance of the centre of gravity from the centre of the circle. If there be the sector of a circle of which the chord OSCJU.ATiON AND I'M ISC 1VSJON. 137 radius, and length of :irc, arc the same as in the last ex anipli-, we have 2 X 153-07 X 200 lonQ 3 X l-)?-07 ~ = = distance of the centre of gravity from the centre of the circle. In a parabolic space, if the axis be 25 inches long, then 25 X 3 = 15 = the distance of the centre of gravity from o the centre. 30 In a parabdoid, if the axis be 30, then we have X 2 3 = 20 = the distance of the centre of gravity from the vertex. A bar of wood, 24 feet long, has a weight suspended at each end, that at one end being 16 Ibs., and the other 4 : then, we have 20 : 24 : : 16 : 19-2 and 20 : 24 : : 4 : 4-8 the distances of the weights from the common centre of gravity, the greater weight being least distant. Hence we see, that 19-2 -f 4-8 = 24, the whole length of the bar; and also 4x19-2 = 16x4-8 = 76-8 ; so that the prin- ciple of virtual velocities, stated before, holds good here also ; and here it may be observed, that it is of the greatest im- portance to trace any leading principle of this kind through its various applications, as it serves to link together and harmonize the whole, and enables us to apply and remember it with greater facility. It is often necessary to determine the centre of gravity experimentally, as in many cases it cannot be conveniently done by calculation. To maintain the firmness of any body resting on a base, it is necessary that the perpendicu- lar drawn from the centre of gravity of the body, to the base on which it rests, be within that base ; and the body will be the more difficult to overset, the nearer that per- pendicular is to the centre of the base, and the more ex- tensive the base is, compared to the height of the centre of gravity. T* HE CENTRE OF OSCILLATION. THE PENDULUM, AND CENTRE OF PERCUSSION. 1. THE centre of oscillation in a vibrating body, is that point in the axis of vibration, in which, if the whole matter 12* 138 MECHANICAL CENTRES. contained in the body were collected, and acted upon by the same force, it would, if attached to the same axis of motion, perform its vibrations in the same time. The centre of oscillation is always situated in the straight line which passes through the centre of gravity, and is perpen- dicular to the axis of motion. It will be seen by these remarks, that the subject of pendulums must be considered here. 2. In theory, a simple pendulum is a single weight, con- sidered as a point, hanging at the lower extremity of an inflexible right line, having no weight, and suspended from a fixed point or centre, about which it vibrates, or oscil- lates ; a compound pendulum, on the other hand, consists of several weights, so connected with the centre of suspen- sion, or motion, as to retain always the same distance from it, and from each other. 3. If the pendulum be inverted, so that the centre of oscillation shall become the centre of suspension, then the former centre of suspension will become the centre of os- cillation, and the pendulum will vibrate in the same time : this is called the reciprocity of the pendulum ; and it is a fact of the greatest utility, in experimenting on the lengths of pendulums. 4. Of the simple pendulum we may observe, that its length, when vibrating seconds, must in the first place be determined by experiment, as it vibrates by the action of gravity, which force differs at different distances from the pole of the earth. By the latest experiments, the length of the seconds' pendulum in the latitude of London, has been found to be 39-1393 inches, or 3-2616 feet; the length at the equator is nearly 39-027, and at the pole 39-197 inches. The length for the latitude of London may be taken for all places in Britain, without any material error. 5. The times of vibration of two pendulums, are directly proportional to the square roots of the lengths of these pen- dulums. 6. Thus : what will be the time of one vibration of a pendulum of 12 inches long at London? x/39-1393 : x/ 12 :: I : 0-5537 = time of one vibration. If the pendulum be 36 inches long, v/39-1393 : v/ 36 :: 1 : 0-9599 = time of one vibration. 7. The lengths of the pendulums are to each other in- OSCILLATION, AND PERCUSSION. 139 trersely as the squares of the numbers of vibrations made in a given time. What is the length of a pendulum vibrating half-seconds or making 30 vibrations in a minute ? (60) a : (30) a :< 39-1393 : 9-7848 = length in inches. The length of a pendulum to make any given number of vibrations in a minute, may be easily found by the following short rule : 140850 i- -i " -- = length. number of vibrations 3 Thus a pendulum to make 50 vibrations in a minute, will be 140850 140850 _ SO* 2500 8. All the rules for simple pendulums may be expressed as follows : The time of one vibration in seconds of any pendulum is _ 1 _ number of vibrations in one second I or |/ the length of the pendulum\ \> 39-1393 Exam. If the number of vibrations of a pendulum be 6256, then - = 1-598 = the time of one vibration. "o25o Or, if the length of the pendulum be 100 inches, then The length of a pendulum in inches is = 39-1393 x time of one vibration 8 ; 39-1393 or - -- number of vibrations' Exam. If the time of one vibration be 1'598 ; find the length. 39-1393 X l'598 a = 100, length of pend. Or. if the number of vibrations in a second be as above, 6856, then we have 39-1393 . 6256 a = 100, length of pendulum. 14C MECHANICAL CENTRES. The number of vibrations in a second may be found thus : | 39-1393 . . r f j- : = number ol vibrations ; \length of pendulum or, the number of vibrations in a second is time of one vibration Tf the time of one vibration be, as above, 1*598 ; then - = '6256, number of vibrations ; i *oy o ' or, if the length of 100, we have" ~) = When a clock goes too fast or too slow, so that it shalj lose or gain in twenty-four hours, it is desirable to regulate the length of the pendulum so that it shall go right. The pendulum bob is made capable of being moved up or down on the rod by means of the screw. If the clock goes too fast, the bob must be lowered, and if too slow, it must be raised ; and we have this rule : number of threads in an inch of the screw X the time in minutes that the clock loses or gains in 24 hours ; this product divided by 37 will give the number of threads that the bob must be screwed up or down, so that the clock shall go right. Ex. If the rod have a screw 70 threads in the inch, and the pendulum is too long, so that the clock is 12 minutes slow in 24 hours ; then we have 2 x 70 x 12 = 45 Jf = threads we must raise the bob, o7 so that the clock shall go right. 9. It is often desirable that a pendulum should vibrato- seconds, and yet be much shorter than 39-1393 inches; Avhich may be done by placing one bob on the rod above the centre of suspension, and another below it : then, having the distances of the weights from the centre of suspension, we may find the ratio which the weights should bear to each other by this rule. Call D the distance of the lower, and d the distance of the upper weight, from the centre of suspension ; then, 39-1393 x D D s OSCILLATION ANU PERCUSSION. 141 a number which, when multiplied by the lower weight, will give the hi-licr. 1) anil d are. taken in inches. Ex. In a pendulum having two bobs, the one 12 inches oelow the centre of suspension, and the other 9-6 inches above the same centre, the lower weight being 8 ounces ; what is the upper weight? 39-1393 X 12 12 3 = . 39-1393 x 9-6 + 9-tt* then, 0-696 X 8 = 5-568 ounces = the weight of the upper bob. 10. If a common walking-stick be held in ^ie hand, and struck against a stone, at different points of its length, it will be found that the hand receives a shock when it is struck at any part of the stick, but at one particular point, at which, if the stick be struck, the hand will receive no shock. This point is called the centre of Percussion, and is usually defined thus : The centre of percussion is that point in a body revolving about an axis, at which, if it struck an immovable obstacle, all the motion of the body would be destroyed, so that it would incline neither way after the stroke. 11. The distance of the centre of percussion from the axis of motion, is the same as the distance of the centre of oscillation from the centre of suspension ; and the same rules serve for both centres. See Oscillation. 12. The distance of either of these centres from the axis of motion, is found thus : 13. If the axis of motion be in the vertex of the figure, and the motion be flatwise ; then, 14. In a right line, it is = * of its length ; In an isosceles triangle = | of its height ; In a circle = f of its radius ; In a parabola = i of its height. 15. But if the bodies move side wise, we have it In a circle = | of the diameter ; In a rectangle suspended by one angle = f of the diagonal. 16. In a parabola suspended by its vertex, = 4 axis + i parameter;* hot if suspended by the middle of its base, = ^ axis -f 5 parameter. 142 MECHANICAL CENTRES. 3 X arc X radius 17. In the sector of a circle = 18. In a cone = f axis -f 4 x chord (radius of base)' 5 x axis 10 T u 2 x , T , 19. In a sphere = r r + radius -}- f>l anft . ..190000 COMPOSITIONS Gold 5, copper 1, Silver 5, copper !, Swed. copper 6, tin Block tin 3, lead 1, Tin 4, lead 1, zinc OF -50000 ...48500 1,. 64000' ...10200 1,. 13000 ...45000 Do. razor temper,150000 Cast tin, Eng. block, 5200 Dn n-rsjin .. fi'lOO 7.\nf. :... 2flOO c. The same from Rennie : Weight that would tear it asunder in Ibs. Length in feet that would break with its own weight Cast steel, 134256 Swedish iron,-"." 72064 English iron, 55872 Cast iron, 19096 Cast copper, 19072 Yellow brass, 17958 Cast tin, 4736 Castlead,"-- 1824 39455 19740 16938 6110 5092 5180 1496 306 Good hemp rope, Do. one inch diam. 6400 18790 5026 18790 D. The cohesive force of a square inch of iron ; from dif- ferent experimentists. Ibs. . Ibs. ...fil fiOfl Dn Dn ...fifVTTP .. . R4QfiO Tin ... f^^ffR , . ,(\i nni T) n .. . ^04.79 Fin Dn. . 5SOOO ..1fi9S5 STRENGTH OP MATERIALS. 151 E. Table of the lateral strength of the following materials one foot long, and one inch square. Weight that will break them. Weight which they CM tear with safety. O-jt . . 20Q - 1 1ft A rri*>rir;in whitfimnp.. . 9OR _ C.'.t - F. The force necessary to crush one cubic inch. Aberdeen granite, blue, Very hard freestone, Black Limerick limestone, Compact limestone, Craigleith stone, Dundee sandstone, Yorkshire paving stone, Redbrick, 1817 Pale red brick, 1265 Chalk, 1127 Cubes of one-fourth of an inch. Iron cast vertically, 11140 horizontally, 10110 Cast copper, 7318 Cast tin, 9.66 Cast lead, 483 Having made these statements, we shall proceed to show how, by the assistance of theoretical results, they may be applied to the wants of the practical engineer. The absolute strength of ropes or bars, pulled length wise, is in proportion to the squares of their diameters. All cylindrical or prismatic rods are equally strong in every part, if they are equally thick, but if not, they will break where the thickness is least. 'The lateral strength of any beam or bar of wood, stone, met^il. &c., is in proportion to its breadth X its depth 8 . In square beams the lateral strengths are in proportion to the cubes of the sides, and in general of like-sided beams as the cubes of the similar sides of the section. 152 STRENGTH OP MATERIALS. The lateral strength of any beam or bar, one end being fixed in the wall and the other projecting, is inversely as the distance of the weight from the section acted upon ; and the strain upon any section is directly as the distance of the weight from that section. If a projecting beam be fixed in a wall at one end, and a weight be hung at the other, then the strain at the end in the wall, is the same as the strain upon a beam of twice the length, supported at both ends and with twice the weight acting on its middle. The strength of a projecting beam is only half of what it would be, if supported at both mds. If a beam be supported at both ends, and a weight act upon it, the strain is greatest when the weight is in the middle ; and the strain, when the weight is not in the middle, will be to the strain when it is in the middle, as the product of the weight's distances from both ends, is to the square of half the length of the beam. Take any two points in a beam supported at both ends ; call one of these points a and the other b ; then a weight hung at a will produce a strain at 6, the same as it would do at a if hung at b. In a beam supported at the ends p c A. and B ; the strain at C, with the whole weight placed there, is to the strain at C with the whole weight placed equally between C and P, as AC is to AP x 5 PC ; and the strain at C by a weight placed equally along AP, is to the strain at C by the same weight placed on C, as AP is to AC. If beams bear weights in proportion to their lengths, either equally distributed over the beams or placed in similar points, the strains upon the beams will be as their lengths 2 . If a beam rest upon two supports, and at the same time be firmly fixed in a wall at each end, it will bear twice as much weight as if it had lain loosely upon the supports ; and the strain will be everywhere equal between the supports. In any beam standing obliquely, or in a sloping direction, As strength or strain will be equal to that of a beam of the same breadth, thickness, and material, but only of the length of the horizontal distance between the points of support. Similar plates of the same thickness, either supported at STHENGTII OF MATERIALS. 153 the ends or all round, will carry the same weight either uniformly distributed or laid on similar points, whatever be their extent. The strength of a hollow cylinder, is to that of a solid cylinder of the same length and the same quantity of mat- ter, as the greater diameter of the hollow cylinder is to the diameter of the solid cylinder ; and the strength of hollow cylinders of the same length, weight, and material, are as their greater diameters. The lateral strength of beams, posts, or pillars, are dimi- nished the more they are compressed lengthwise. The strength of a column to resist being crushed is directly as the square of the diameter, provided it is not so long as to have a chance of bending. This is true in metals or stone, but in timber the proportion is rather greater than the square. The strength of homogeneous cylinders to resist being twisted round their axes, is as the cubes of their diameters ; and this holds true of hollow cylinders, if their quantities of matter be the same. PROBLEMS. To find the strength of direct cohesion : Area of transverse section in inches x measure of cohe- sion = strength in Ibs. to resist being pulled asunder. Ex. In a square bar of beech, 3 inches in the side, we have 3 X 3 X 9912 = 89208 Ibs. NOTE. The measure of cohesion for timber is taken from col. C, table A, and for other materials, from tables B or C. In a beam of English oak, having four equal sides, each side being four inches, we have 4 x 4 x 9836 = 157376 Ibs., the strength. In a rod of cast steel, 2 inches broad and Ik inch thick, we have 2 X U X 134256 = 402768 Ibs., the strength. What is the greatest weight which an iron wire - v of an inch thick will bear ? The area of the cross section of such wire will be '007854, hence we have -007854 x 84000 = 659-736 Ibs. /To find the ultimate transverse strength of any beam : When the beam is fixed at one end and loaded at the other then the dimensions being in inches, 154 STRENGTH OF MATERIALS. breadth x depth 2 x transverse strength = the ultimate length of beam transverse strength. NOTE. In column S, Table A, will be found the trans- verse strength of timber, and in table E, that of iron, / (145) = 12 inches, nearly. t>y x 4 To find the deflection of a beam fixed at one end, and loaded at the other : length of beam in inches 3 X 32 x weight f tab. numb. E (in table A) x breadth x depth 3 flection in inches. J(OTE. If the beam be loaded uniformly, use 12 instead of 32 in the rule. If a weight of 300 be hung at the end of an ash bar fixed 156 STRENGTH OF MATERIALS. m a wall at one end, and five feet long, it being 4 inchei square : what is its deflection ? 60 3 X 32 X 300 = 1-23 inches = the deflection. 6580750 X 4 x 4 3 If the beam be supported at both ends and loaded in the middle : length (in inches) 3 X weight . tab. numb*. (E, table A) X breadth x depth 3 NOTE. When the beam is firmly fixed at both ends, the deflection will be f of that given by the rule. Ex. If a beam of pitch pine, 8 inches broad, 3 inches thick, and thirty feet long, is supported at both ends and loaded in the centre with a weight of 100 Ibs. ; what is its deflection ? 360 3 x 100 = 4-407 inches, deflection. 4900466 X 8 x 3 3 If the beam had been firmly fixed at both ends, the de- flection would have been 4-408 X | = 2-938 inches. If the beam had been supported at both ends, and loaded uniformly throughout, the deflection would have been 4-408 X !- = 2-754. To find the ultimate deflection of a beam l " e depth. To find the thickness from the same circumstances, we nave by the 3J, 12 8 x 2S-28 3 x 3 go v. or>a - == ^ inches, the thickness. O X oU The same remarks hold true to a certain extent in roof- ing. A high roof is both heavier and more expensive than d low roof, as they will always be as the squares of the lengths of the couple-legs, so far as the scantling is con- cerned ; but the slates and other materials increase in weight WHEELS. 165 ind expense as the length of the couple -legs simply. High roofs have, however, the advantage of being less severe upon the walls than low ones, that is to say, so far as a tendency to push out the walls is concerned. To obtain the length of the rafter from that of the span, a common rule is to multiply the span by -66, which gives the length of the rafter; thus, 14 feet of span gives 14 x '66 = 9-24 feet, the length of the rafter. NOTE. The numbers in the tables of the strength of materials are such as will break the bodies in a very short time ; the prudent artist, therefore, will do well to trust no more than about one-third of these weights ; also great allowance must be made for knotty timber, and such as is sawn in any part across or obliquely to the fibres. WHEELS. IN page 136 we promised again to resume the subject of wheel-work ; and we now proceed to consider, in the first place, the formation of the teeth of wheels. A Cog-wheel is the general name for any wheel which has a number of teeth or cogs placed round its circumference. A Pinion is a small wheel which has, in general, not more than 12 teeth ; though, when two toothed wheels act upon one another, the smallest is generally called the pinion ; so is also the trundle, lantern, or wallower. When the teeth of a wheel are made of the same material and formed of the same piece as the body of the wheel, they are called teeth ; when they are made of wood or some other material, and fixed to the circumference of the wheel, they are called cogs ; in a pinion they are called leaves ; in a trunflle, staves. The wheel which acts is called a leader, or driver ; and the wheel which is acted upon by the former is called a foBower, or the driven. When a wheel and pinion are to be so formed that the .pinion shall revolve four times for the wheel's once, then they must be represented by two circles, whose diameters a/e to one another, as 4 to 1. When these two circles are so placed that they touch each other at the circumferences, then the line drawn joining their centres, is called the lina 166 WHEELS. of centres, and the radii of the two circles the proportions* radii. These circles are called, by mill-wrights in general, pitch-lines. The distances from the centres of two circles to the ex- tremities of their respective teeth, are called the real radii, and the distances between the centres of two contiguous teeth measured upon the pitch-line, is called the pitch of the wheel. Two wheels acting upon one another in the same plane, are called spur geer. When they act at an angle, they are called bevel geer. Teeth of wheels and leaves of pinions require great care and judgment in their formation, so that they neither clog the machinery with unnecessary friction, nor act so irre- gularly as to produce any inequalities in the motion, and a consequent wearing away of one part before another. Much has been written on this subject by mathematicians, who seem to agree that the epicycloid is the best of all curves for the teeth of wheels. The epicycloid is a curve differing from the cycloid formerly described, in this, that the gene- rating circle instead of moving along a straight edge, moves on the circumference of another circle. The teeth of one wheel should press in a direction per- pendicular to the radius of the wheel which it drives. As many teeth as possible should be in contact at the same time, in order to distribute the strain amongst them ; by this means the chance of breaking the teeth will be dimi- nished. During the action of one tooth upon another, the direction of the pressure should remain the same, so that the effect may be uniform. The surfaces of the teeth in working should not rub one against another, and should suffer no jolt either at the commencement or the termination of their mutual contact. The form of the epicycloid satis- fies all these conditions ; but it is intricate, and the involute of the circle is here substituted, as satisfying equally these conditions, and as being much more easily described. Take the circumference ABC of the wheel on which it is proposed to raise the teeth, and let a be a point from which one surface of one tooth is to spring, then fasten a string at B, such that when stretched and lying on the circumference shall reach to a/ fix a WHEELS. lb'7 pencil at a, and keeping the string equally tense, move the pencil outwards, and it will describe the involute of the circle which will form the curve for one side of the tooth. Fasten the string at B so that its end, to which the pencil is fixed, be at the point from which the other face of the tooth is to spring and proceed as above ; then the curve of the other side of the tooth will be formed ; and the figure of one of the teeth being determined, the rest may be traced from it. The teeth of the pinion are formed in like manner. The observation of practical men has furnished us with a method of forming teeth of wheels, which is found to an swer fully as well in practice as any of the geometrical curves of the mathematician. We have the pattern here of the segment of a wheel with cogs fixed on in their rough state, and it is required to bring them to their proper figure : they are consequently understood to be much larger than they are intended to be when dressed. The arc 6, 6, is the circumference of the wheel on which the bottoms of the teeth and cogs rest. Draw an arc a, a, on the face of the teeth for the pitch line of their point of action ; draw also rf, rf, for their extremities or tops. When this is done, the pitch circle is correctly divided into as many equal parts as there are to be teeth. The compasses are then to be opened to an extent of one and a quarter of those divisions, and with this radius arcs are described on each side of every division on the pitch line a, a, from that line to the line d, d. One point of the compasses being set on c, the curve f, g, on one side of one tooth, and o, n, on the other sides of the other are described. Then the point of the compasses being set on the adjacent division k, the curve /, m, will be de- scribed : this completes the curved portion of the tooth e. The remaining portion of the tooth within the circle a, a, is bounded by two straight lines drawn from g and m to- wards the centre. The same being done to the teeth all round, the mark is finished, and the cogs only require to be dressed down to the lines thus drawn. / It will be easy to determine the diameter of any wheel having the pitch and number of teeth in that wheel given Thus, a wheel of 54 teeth having a pitch of 3 inches, we 163 WHEELS. have 54 quently, X 3 = 162 inches, the circumference, conse- 162 = 51-5 inches diameter, nearly. 3-1416 or about 4 feet 3 inches. In the following table we have given the radii of wheels of various numbers of teeth, the pitch being one inch. To find the radius for any other pitch, we have only to multiply the radius in the table by the pitch in inches, the product is the answer. Thus for 30 teeth at a pitch of 3| inches, we have 4-783 x 3-5 = 16-74 inches, the radius. 1 2 3 4 5 6 7 8 9 10 1-668 1-774 1-932 2-089 2-247 2-405 2-563 2-721 2-879 3-038 20 3-196 3355 3-513 3-672 3-830 3-989 4-148 4-307 4-465 4-624 30 4-783 4-942 5-101 5-260 5-419 5-578 5-737 5-896 6-055 6-214 40 6-373 6-532 6-643 6-850 7-009 7-168 7-327 7-486 7-695 7-804 50 7-963 8-122 8-231 8-440 8-599 8-753 8-962 9-076 9-235 9-399 60 9-553 9-7121 9-872 10-031 10-190 10-349 10-508 10-662 10-826 10-935 70 11-144 11-303 11-463 11622 11-731 11-940 12-099 12-758 12-417 12-676 80 12-735 12-895 13-054 13-213 13370 13531 13690 13-849 14-008 14-168 90 14-327 14-4H6 14-645 14-804 14-963 15-122 15281 15-441 15-600 15-759 100 15-918 16-072 16-236 16-305 16-554 16713 16-873 17-032 17-191 17-350 110 17-504 17-6U8 17-987 17-827 18-146 18-305 18-464 18-623 18-782 18-941 120 19-101 19-260 19-419 19-578 19-737 19-896 20-055 20-2 f4 20-374 20-533 130 20-692 20-851 21-010 21-169 21-328 21-48S 21-647 21-806 21-460 22-124 140 22-283 22-44222-602 22-761 22920 23074 23-238 23397 23-556 23-716 150 23875 24-03424-193 24-352 24-511 24620 24-830 24-989 25-148 25-307 160 25-466 25-625 25-784 25-944 26-103 26-262 26-421 26-580 26-739 26-894 170 27-058 27-217 27-376 27-535 27-694 27-853 27-931 28-172 28-331 28-490 180 28-699 28-80828-967 29-126 29-286 29-445 29-604 29-763 29-922 30-086 190 30-241 30-400 30-559 30-718 30-S77 31-036 31-196 31-355 31-514 31-673 200 31-832 31-992 32-150 32-310 32-469 32-628 32-787 32-846 33-105 33-264 210 33-424 3358333-742 33-901 34-060 34-219 34278 34-537 34-697 34-856 220 35-015 35-174 35-333 35-492 35-652 35-811 35-970 36-129 36-288 36-447 230 36-607 36-76636-925 37-084 37-243 37-402 37-561 37-720 37-880 38-039 240 38-198 38-357 38-516 38-725 38-835 38-994 39-153 39312 39-471 39-631 250 39-790 39-949 ! 40-108 40-262 40-426 40-585 40-744 40-904 41-063 41-222 260 41-381 41-54U41-699 4i-858 42-019 42-177 42-336 42-495 42-654 42-813 270 42-973 43-13243-291 43-450 43-609 43-768 43-927 44-087 44231 44-405 280 44-564 44-723 44-882 45-042 45201 45360 45519 45-678 45837 45-996 290 46-156146 315,46-474 46-633 16-792 46-751 47-111 47-270 47-429 47-583 1 1 This will be found a very useful table in abridging calcu- lation, for instance, if we wish to find the radius of a wheel having 132 teeth, we look for 130 at the left-hand side column, and 2 at the top, and where these columns meet, we find the number 21-010, which, if the pitch of the wheel be 2 inches, we multiply by 2|. WHKKl.s. 169 21-010 x 2-5 = 52-525 inches, radius of required wheel. An easy practical rule Cor the same purpose is the fol- lowing : Take the pitch by a pair of compasses, and lay it off on a straight line, seven times, divide this line into eleven equal parts ; each will be equal to four ot' the radius, which is supposed to consist of as many parts as the wheel has teeth. Let the pitch be two inches, and the number of teeth 60 t-ien the diagram will show how to lay it down. 1 2 :* 4567 i~~2T~3~~4" ~5~6 7. 8 9 10 11 C D 4, 8, 12, 16, &c. The upper line is the pitch laid off seven times, and forming AB, which is divided into 11 equal parts, one of which, CD, being repeated for every four teeth in the wheel, that is, in this case, fifteen times, will give the radius. The same may be done by calculation, going by the principles of the rule, thus, 2x7 = 14, then = 1-272, which divided by 4 gives 0-318 = the value of of the radius ; 4 60 wherefore, -318 x 60 = 19-08. By the table we have, 9-552 X 2 = 19-104, the difference in the two results being 19-104 19-08 = -024, or twenty-four thousandth parts of an inch. Reversing the operation, let it be required to find the pitch, the radius of the wheel being 19-104, and number of teeth 60. We have --* -318, then -318 x 4 = 1-272, 60 and 1-272 X 11 = 13-992. Now this is the whole line AB, 13*992 and therefore, = 1-998, which is so verv nearly / 7 two inches, the difference being 2 1-998 = -002 oi an inch, we ought in practice to take two as the pitch. 15 170 WHEELS. A little reflection on the part of the reader will show *? 11 6Qfi that since = -636, and = 1-571, and = *159 117 4 Tve have, (1) pitch x '159 x number of teeth = radius. /n\ radius ' number of teeth x '159 = radius (3) - ; - TTT: = number of teeth. v ' pitch X '159 Thus, (1) 2 X '159 X 60 = 19-08 = radius, 19 19 ( 3 ) ^ - ;W = 60 = number of teeth. v ' 2 x -159 NOTE. The number -16 may be employed instead of 159, being easily remembered. These rules are approxi- mate, and the error diminishes as the number of teeth in- creases. The true pitch is a straight line, but these rules give it an arc of the circle, which passes through the centre of the teeth, whereas it should be the chord of the arc. An eminent writer on clock-work gives the following rules regarding wheels and pinions : (A) As the number of teeth in the wheel + 2-25, Is to the diameter of the wheel, So is the number of teeth in the pinion + 1-5, To the diameter of the pinion. A wheel being 12 inches diameter, having 120 teeth, drives a pinion of-20 leaves ; wherefore, 120 + 2-25 = 122-25 and 20 + 1-5 = 21-5, Then 122-25 : 12 : : 21-5 : 2^104 = the diameter of the pinion. (B) As the number of teeth in the wheel + 2-25, Is to the wheel's diameter, So is 3 (teeth in wheel -f leaves in pinion) To the distance of their centres. A wheel's diameter being 3'2 inches, number of teeth 96, the leaves in the pinion being 8, then, 104 96 + 2-25, = 98-25 and (96 -f 8) = - - = 52. 171 Hence, 98-25 : 3'2 : : 52 : 1-6936 = the distance which the centres ought to have. The strength of wheels is a subject which has occupied the attention of the most eminent practical engineers, but the rules they have given us are entirely empirical, that is to say, the result of experiment. The strength of the teeth will vary with the velocity of the wheel, the strength in horses' power at a velocity ol' 2-27 feet per second, will be breadth of the tooth x its thickness" - = power, length of tooth Required the strength in horses' power of a tooth 4 inches broad, 1-3 inches thick, and 1-6 inches long, at a velocity of 2-27 feet per second, here we have 4 X l"3 a = 4-225, the horses' power at a velocity of 2 27. 1'6 The power at any other velocity may be found by pro- portion, thus the same at 6 feet per second. 2-27 : 6 :: 4-225 : 11-1 = horses' power a* i, velocity of 6 feet per second. The thickness of a tooth x 2-1 = the pitch The thickness of a tooth x 1'2 = length. Ex. The thickness of a tooth being l in- hos, then we have 1-5 X 2-1 = 3-15 = the pitch. 1-5 X 1-2 = 1-8 = the length The breadth in practice is usually 2'5 times the pitch. The arms of wheels generally taper from the axle to the rim, because they sustain the greatest stress towards the axle. It is obvious, that the more numerous the arms of a wheel are, they each suffer a proportionately less strain, as the resistance will be diffused over a greater number. The power acting at the rim X length of :rm 3 number of arms X 2656 X 0-1 and cube of depth. Ex. If the force acting at the extremity of the arm of a wheel be 16 cwt.; the radius of the wheel being 5 feet, and the number of arms 6, then we have 16 X 112 = 1792 Ibs. .== the force ; wherefore, 1792 X 5 3 224000 r^T656^roT == -159F6 * 14 ' breadth and CUbe f depth. 172 WHEELS. Now, let us suppose that the breadth is two inches, we Amst divide this 140 by it, whence, 140 - = 70, the cube of the depth, 9 ai.d the cube root of 70 will be found = 4*121, which is the depth of each arm. When the depth at the axis is intended to be double of the depth at the rim, the number 1640 is to be used in the rule instead of 2't56. The tables vhich follow will be found in the highest degree useful to (D 2 > ? "i - ? -i 9 9 X B *< I ! ! I 5 CD a tp g> ca : : : : : P -7- --7 fr Honet' power. -,- l-i- Breadth of teeth in incho. _____,; _ ,i , : ,i ^: . W W 00 63 SO COCO Revolves per minute. ODQOO'OlO9taW^.COfcS*fcO r. - r. H- H-" H- 1 > OO>-^-O500Oth ill inches. Strengih of ll'rlhjiT lll>. of horses' ]* nvcr. at 4 cund. Horses' power at 3 feet per second. Horses' po*er at 6 feet per second. Horses' power at 3 feet per second. 3-99 1-9 7-6 27-43 20-57 41-14 54-85 3-78 1-8 7-2 23-32 17-49 34-98 46-64 3-57 1-7 6-8 19-65 14-73 29-46 39-28 3-36 1-6 6-4 16-38 12-28 24-56 32-74 3-15 1-5 6- 13-5 10-12 20-24 26-98 2-94 1-4 5-6 10-97 8-22 16-44 21-92 2-73 1-3 5-2 8-78 6-58 13-16 17-34 2-52 1-2 4-8 6-91 5-18 10-36 13-81 2-31 1-1 4.4 5-32 399 7-98 10-64 2-1 1-0 4- 4-0 3-0 6-0 8-0 1-89 9 3-6 2-91 2-18 4-36 5-81 1-68 8 3-2 2-04 1-53 3-06 3-08 1-47 7 2-8 1-37 1-027 2-04 2-72 1-26 6 2-4 86 64 1-38 1-84 1-05 5 2- 5 375 75 1- HYDROSTATICS. HYDROSTATICS comprehends all the circumstances of the pressure of non-elastic fluids, as water, mercury, -r>!) 45-26 55-23 65-28 76-1 7 17-79 27-15 36-82 46-79 56-84 67-65 78-53 ; 71 18-41 28-08 38-05 48-1 58-91 69-79 81- ! 71 19-03 29- 39-05 49-86 60-74 71-95 83-45 71 19-64 29-69 40-5 51-38 G2-r>9 74-09 86- : 8 20-02 30-83 41-71 52-92 61-42 76-23 88-35 ; . 'Q > . S 4 20-86 31-74 42-95 54-45 '66-26 78-38 90-81 8.| 21-69 32-9 44-4 56-21 68-33 80-76 93-49 * 8| 22-09 33-59 45-4 57-52 69-95 82-68 95-72 ft 22-71 34-52 46-64 59-07 71-8 84-84 98-18' 192 HYDROSTATICS. Diini. of bore. iL. Inch. Inch. Inch. Inch. f Inch. Inch. Inch. lb. lb. lb. lh. 11). lb. lb. 8i 23-31 35-43 47-86 60-59 73-63 86-97 100-63 9* 23-93 36-36 49-09 62-13 75-47 89-13 103-1 9| 24-55 37-28 50-32 (j:Mi6 77-32 91-28 105-54 10 25-16 38-2 51-54 65-2 79-16 93-42 108 10i 25-77 39-11 52-77 66-73 80-99 95-57 110-44 10* 26-38 40-04 54 68-26 82-84 97-71 113 10| 27 40-96 55-22 69-8 84-67 99-86 115-35 11 27-62 41-88 56-46 71-33 b6-,";2 102-01 117-81 Hi 38-22 42-8 57-67 72-86 88-35 104-15 120-26 "i 28-84 43-71 58-9 74-39 90-19 106-3 122-71 11* 29-45 44-64 60-13 75-93 92-04 108-45 125-18 12 30-06 45-55 61-35 77-46 93-6 110-6 127-6 Diam. of bore. Inch. Inch. Inch. 1 Inch. H Inch. U Inch. li Inch. 1* Inch. 2 Inch. Inch. lb. lb. lb. lb. lb. lb. lb. " lb. lb. 12* 63-5 97-3 114 132 149 167 205 243 285 13 66 101 118 137 154 173-5 212 252 294 18* 68-4 104-8 122 141-5 160 179 219 260 304 14 75 108-2 126 146 165 185 227 269 314 '*! 73-4 112-3 130 151 170 192 234 277 324 15 75-8 115-7 135 156 176 198 242 286 334 15* 78-1 119 139 .161 181 204 250 295 344 16 80-7 123 143 166 187 211 257 303 355 16* 83-1 126-5 147 170-1 192 217 264 312 363 17 85-5 130 152 178-5 198 223 271 322 376 17* 87-8 133-5 157 180-5 203 229 278 330 383 18 90-5 137 161 185 209 235 285 338 ' 393 18* 93 140-5 166 190 217 241 293 347 402 19 95-5 144-8 169 195 222 247 300 354 412 19* 97-8 148-5 174 200 227 253 307 363 422 20 100 152 178 205 233 259 315 372 432 | 20* 102-5 156 ': 183 210 238 26 323 381 442 The following TABLE of the weight of different sub- stances used in building and engineering requires no ex planation. SPECIFIC GRAVITY. 193 NamMofBodim. Weight of a ubic foot in ounces. VfeifM of a cubic foot in p'.Ulllt. Wright of a cubic inch in ounces. Weight of a cubic inch in (ouil'l-. Nuabcr oT I cubic inche* uu , a pound. 71 Copper, cast.... Copper, sheet 8788 8915 8396 7271 7631 11344 7833 7816 7190 7292 9880 8784 1520 1250 2000 2416 2672 2742 3160 2880 945 240 544 556 660 696 745 760 852 970 870 915 932 927 1000 1028 1015 1026 J13568 549-25 557-18 52 -1-7 5 151-43 47(>-i)3 709-00 489-56 488-50 449-37 455-75 619-50 649-00 95-00 78-12 125-00 151-00 167-00 171-37 197-50 180-00 59-00 15-00 34-00 34-75 41-25 43-50 46-56 47-50 53-25 60-62 54-37 57-18 58-25 57-93 62-50 64-25 63-43 64-12 848-00 5-086 5-159 4-852 4-203 4-410 6-456 1-527 4-517 4-156 4-215 5-710 5-0775 8787 7225 1-156 1-396 1-544 1-585 1-826 i-r.fU 5462 138 315 321 382 403 431 440 493 561 503 529 539 536 578 594 587 593 7-851 3178 3225 3037 263 276 4103 2833 2827 26 2636 3585 3177 055 0452 0723 0873 0967 0991 1143 1042 0342 0087 0197 0201 024 0252 027 0275 0308 0351 0315 0331 0337 03352 03617 0372 0367 037 4908 3-146 3-103 3-293 3-802 3-623 2-437 3-530 3-537 3-845 3-790 2-789 3-147 18-190 22-120 13-824 11-443 10-347 10-083 8-750 9-600 29-258) 115-200! 50-823 49-726 41-890 39-724 37-113 36-370 32-449 28-505 31-771 30-220 29-665 29-288 27-648 26-894, 27-24$ 26-949 2-037 Steel, soft Coal Stone, paving \Tirh1p. .. rjiocc . Pnrk . F,l m Pine, pitch Teak AVi . . Mahogany Oak . Oil of turpentin Linseed oil ... Spirits, proof-- - Water, distilled Tir . . 17 194 HYDROSTATICS. The foregoing tables and rules will be found of the ut- most service, in the ready calculation of the weight of materials commonly used in engineering. What is the weight of a bar of Swedish iron 16. feet long, 3 inches broad, and !! inch thick? By table B, 3-38 is the weight of a piece of Swedish iron, of one foot long and one inch square, wherefore, 3-38 x 16 X 3 = 162-24; and then for the fraction -1, in table A, we have for the weight of 1 foot by ! of an inch square = -034; hence, -034 x 3 x 16 = 16-32; wherefore the sum of the two = 162-24 + 16-32 = 178-56 Ibs., the weight/ If we wish the weight of an equal bar of cast iron, we must employ the multipliers in table D ; hence, 178-56 X '925 = 165-168. If we wished it for lead, the multiplier from the same table being 1-457, we have, 178-56 x 1-457 = 260-1619 Ibs., &c., &c, Then if lead were 1 penny per pound, the price of such a bar would be The following practical rules are often useful and may be easily remembered. For round bars of iron, diameter (m) 3 X length in ft. X 2-6 = weight of wrought iron in Ibs. diameter (m) a X length in ft. x 2-48 = weight of cast iron bars in Ibs. A cylindrical bar is 2 inches diameter and 29 inches long, therefore, 2 s x 2-5 x 2-6 = 26 Ibs. if it be wrought iron, but if cast, 2 s x 2-5 x 2-48 = 24-8 Ibs. Multiply the sum of the exterior and interior diameters of a cast iron ring by the breadth and thickness of the rim, and also by 0074, he results will be the weight in cvvts. HYDRODYNAMICS. As hydrostatics embraces the consideration of fluids at rest, so hydrodynamics or hydraulics comprehends the cir- cumstances of fluids in motion. Of this science, little, comparatively speaking, is yet known ; but as it is of the utmost importance to man, we will endeavour to lay before our readers a statement of the more important results of recent inquiry into it. If a fluid move through a pipe, canal, or river, of various breadths, always filling it, the velocity of the fluid at dif- ferent parts will be inversely as the transverse sections of these parts. Thus let there be a canal, AB, of various breadths at different places, then will the velocity in the portion ab be to that of the velocity in erf, as the area of the cross section at cd is to that at ab, and the velocity at ef will be to that at cd as the area at cd is to the area at ef, being always in inverse proportion. Suppose the velocity at ab 10 feet per second, and the area there 100 feet, then if the area at cd be 25 feet, we have 25 : 100 : : 10 : 40 feet, the velocity of the water at erf; and if the area at efbe 50 feet, then 50 : 25 : : 40 : 20 feet, the velocity at ef, the canal being kept con- tinually full. The quantity of water that flows through a pipe, or in a canal or river, at any part, is in proportion to the area multiplied by the velocity at that part. The calculation of the motion of rivers is often of the hig/iest utility to the engineer. This is sometimes done by Jhe employment of very intricate formulas, but such methods, if easier could be found, would evidently be in- 195 196 HYDROl/rNAMICS. consistent with the nature of this work. The method which we shall give is simple, and will be found to answer all the purposes of the practical man. In a river, the greatest velocity is at the surface and in jthe middle of the stream ; from which it diminishes toward the bottom and sides, where it is least. The velocity at the middle of the stream may be ascer tained, by observing how many inches a body floating with the current passes over in a second of time. Gooseberries will fit this purpose exceedingly well; if they are not at hand, a cork may be employed. Take the number of inches that the floating body passes over in one second, and extract its square root ; double this square root, subtract it from the velocity at top, and add one, the result will be the velocity of the stream at the bottom. And these velocities being ascertained, the mean velocity, or that with which if the stream moved in every part, it would produce the same discharge, may be found = the velocity at top v/velocity at top + '5. Exam. If the velocity at the top and in the middle of the stream, be 36 inches per second, then, 36 (2 X \/36) -f 1 =36 12 + 1 = 25 = the least velocity, or the velocity at bottom. And the mean velocity will be = 36 v/36 -f -5 = 36 6 + -5 = 30-5. When the water in a river receives a permanent increase from the junction of some other river, the velocity of the water is increased. This increase in velocity causes an in- crease of the action of the water on the sides and bottom, from which circumstance the width of the river will always be increased, and sometimes, though not so frequently, the depth also. By the reason of this increased action of the water on the bottom, the velocity is diminished until the tenacity of the soil or the hardness of the rock afford a sufficient resistance to the force of the water. The bed of the river then changes only by very slow degrees, but the bed of no river is stationary. It is of the greatest use to know the amount of the action of any stream on its bed, and for this purpose a knowledge of the nature of the bed and of the velocity at bottom, are absolutely necess-ary. Every kind of soil has a certain velocity which will insure the stability of the bed. A less velocity would allow the HYDRODYNAMICS. 197 waters to deposit more of the matter which is carried with the current, and a greater velocity would tear up the chan- nel. From extensive experiments it has been found, that a velocity of 3 inches per second at the bottom, will just begin to work upon the fine clay used for pottery, and, however firm and compact it may be, it will tear it up. A velocity of 6 inches will lift fine sand 8 inches, will lift coarse sand (the size of linseed) 12 inches, will sweep along gravel 24, will roll along pebbles an inch diameter and 3 feet at bottom, will sweep along shivery stones the size of an egg. When water issues through a hole in the bottom or side of a vessel, its velocity is the same as that acquired by a body falling through free space from a height equal to that of the surface of the water above the hole. The most correct rule for ascertaining the velocity of water running through pipes and canals is this : 57 X height of head X diam. of pipe\ 1 Vlength of pipe X 57 X diam. of pipe/ the velocity in inches with which the water will issue from the orifice. All the measures are understood to be taken in inches. Exam. If there be a reservoir of water whose depth is 6 feet, having a tube 1 foot long and 2 inches bore, open so as to let the water escape at a distance of 18 inches from the bottom, then we have, 6 X 12 = 72 = whole depth of water on the reservoir, and 72 18 = 54, the height of the head of the fluid above the orifice, wherefore by the rule, v' (4-5) X 231 = 2-121 X 23s = 49-49 inches per second, the velocity of the water. And, by multiplying this result by the area of the orifice, we get the quantity discharged in one second hence, if the pipe be circular, we have, 2-5 2-5 x 3-1416 . = 1-25 = radius, and = naif ^ tircu inference = 1-9635 = area of orifice, hence, 49-49 X 1-9635 = 97-173 cubic inches. The* quantity of water that flows out of a vertical rectan- gular aperture, that reaches as high as the surface, is | of 17* 198 HYDRODYNAMICS. the quantity that would flow out of the same aperture, placed horizontally at the depth of the tiase. When water issues out of a circular aperture in a thin plate placed on the bottom or side of a reservoir, the stream is contracted into a smaller diameter, to a certain distance from the orifice. The vein is smaller at the distance of half the diameter of the orifice where the area of the section .of the vein is {-{? of that of the orifice, and at the above point the stream has the velocity given by theory, so that to ob- tain the quantity of water discharged, we multiply the velocity by the area of the orifice, and { of this will be the true result. -When the water issues through a short tube, the vein of the stream will be less contracted than in the former case, in the proportion of 16 to 13. But when the water issues through an aperture which is the frustum of a cone, whose greater base is the aperture, the height of the conic frustum = one half the diameter of the aperture and the area of the small end to that of the large end, as 10 : 16 ; then, in this case, there will be no contraction of the vein ; and from this it may be inferred, that, when a supply of water is required, the greatest possible from a given orifice, this form should be employed. To determine the quantity of water discharged by a small vertical or horizontal orifice, the time of discharge, and the height of the fluid in the vessel, when any two of these quantities are known. Let A represent the area of the small orifice, W the quantity of water discharged ; T the time of discharge, H the height of fluid in the vessel, and # = 16-087 feet, the space described by gravity in a second. Then we have, W = 2 x A x * N/# X H 4. 2 X t X W x H w s H = 4 x g X t 2 X A 3 By means of these formulas we may determine the quan- tity of water W which is discharged in the same time T, from any other vessel in which A' is the area of the orifice, HYDRODYNAMICS. 199 and H the altitude of the fluid ; for since t and g are con etant, we shall have W : W'= A,/ H : A' -,/ H'. Table shou'iag the quantify of JTater discharged in one Minute by Orifices differing in form and position. aslant H( a iL-!it of the Fluiil above the centre of the orifice. Form and position of the Orifice. Diameter of the orifice. No. of cubic inches dis- charged in a minute. Ft. in. lin. Lines. 11 8 10 Circular and Horizontal, 6 2311 Circular and Horizontal, 12 9281 Circular and Horizontal, 24 37203 Rectangular and Hori- - zontal, 12 by 3 2933 Horizontal and Square, 12 side 11817 Horizontal and Square, 24 side 47361 900 Vertical and Circular, G 2018 Vertical, and Circular, 12 8135 400 Vertical and Circular, 6 1353 Vertical and Circular, 12 5436 , 507 Vertical and Circular, 12 628 From these results we may conclude, 1. That the quantities of water discharged in equal times by the same orifice from the same head of water, are very nearly as the areas of the orifices ; and, 2. That the quantities of water discharged in equal times by the same orifices under different heads of water, are nearly as the square roots of the corresponding heights of the water in the reservoir above the centres of the orifices. 3. The quantities of water discharged during the same time by different apertures under different heights of water in the reservoir, are to one another in the compound ratio of the areas of the apertures, and of the square roots of 'the heights in the reservoirs. This general rule may be considered as sufficiently cor- rect for ordinary purposes ; but, in order to obtain a great Jflegree of accuracy, Bossut recommends an attention to he three following rules. I. Friction is the cause, that, of several similar orifices 200 HYDRODYNAMICS. the smaLest discharges less water in proportion than those which are greater, under the same altitudes of water in the reservoir. 2. Of several orifices of equal surface, that which has the smallest perimeter ought, on account of the friction, to give more water than the rest, under the same altitude of water in the reservoir. 3. That, in consequence of a slight augmentation which the contraction of the fluid vein undergoes, in proportion as the height of fluid in the reservoir increases, the expense ought to be a little diminished. Table of Comparison of the Theoretic with the Real dis charges from an orifice one inch in diameter. Constant height of the water in the reservoir above the centre of the orifice. Theoretical dis- charges through acircular orifice one inch in dia- meter. Real discharges in the same time through the same orifice. Ratio of the theoretical to the real discharges. Paris feet. Cubic inches. Cubic inches. 1 4381 2722 1 to 0-62133 2 6196 3846 1 to 0-62073 3 7589 4710 1 to 0-62064 4 8763 5436 1 to 0-62034 5 9797 6075 1 to 0-62010 6 10732 6654 1 to 0-62000 7 11592 7183 1 to 0-61965- 8 12392 7672 1 to 0-61911 9 13144 8135 1 to 0-61892 10 13855 8574 1 to 0-61883 11 14530 8990 1 to 0-61873 12 15180 9384 1 to 0-61819 13 15797 9764 1 to 0-61810 14 16393 10130 1 to 0-61795 15 16968 10472 1 to 0-61716 1 2 3 4 It appears from this table, that the real as well as the theoretical discharges are nearly proportional to the square roots of the heights of the fluid in the reservoir. Thus for the heights 1 and 4, whose square roots are as 1 to 2 feet, the real discharges are 2722 and 5436, which are to one another as 1 to 1-997, very nearly as 1 to 2. HYDRODYNAMICS. SOi Let it be required to determine the quantity of water dis- charged from an orifice of 3 inches in diameter, under an altitude of 30 feet. Then, since the real quantities dis- charged are in the compound ratio of the orifices, and the square roots of the altitudes of the water, and since the theoretical discharge by an orifice 1 inch in diameter, under an altitude of 15 feet is 16968 cubical inches in a minute, we have 1 ^/ 15 : 9 v/ 30 = 16968: 215961, the theoreti- cal discharge. But the theoretical is to the real discharge as 1 to -62, the above value being diminished in that ratio, gives 133309 cubic inches for the real quantity, of water discharged by the orifice. The following formulae have been given by M. Prony as deduced from the preceding experiments of Bossut, Q = 0-61938 AT ^/ 2 g H, A being the area of the orifice in square feet, H the altitude of the fluid in feet, T the time, g the force of gravity at the end of a second, and Q the quantity of water in cubic feet. As ^/ 2 g is a constant quantity, and is equal to 7*77125, we have Q = 4-818 AT */ H for orifices of any form. If the orifices are circular, and if d represents their dia- meter, then Q = 3-7842 d* T rding to expe- riments ir adu in Scotland. 1 0,403 0,428 2 1,WO 1,211 3 2,095 2,226 4 3,225 3,427 5 4,507 4,789 6 5,925 6,295 7 7,466 7,933 8 9,122 9,692 9 10,884 11,564 10 12,748 13,535 11 14,707 15,632 12 16,758 17,805 13 18,895 20,076 14 21,117 22,437 15 23,419 24,883 16 25,800 27,413 17 28,258 30,024 18 30,786 32,710 Talk containing the quantities of Water discharged by Cylindrical Tubes one inch in diameter and of different lengths, whether the Tubes were inserted in the bottom or in the sides of the vessel. Constant altitude of the fluid above the superior base of the tube 11 feet 8 inches and 10 lines. Lengths of the Tubes expressed in lines. charged in a minute. The tube filled with the \ jj issuing fluid f J iy The tube not filled Avith - the issuing fluid 3 12274 12188 12168 9282 IIYDKODVNAMICS. 203 Table, of comparison of lite Theoretical u-itft the Rial Dixtliurgefi from an additional Tube of a cylindrical form, one inch in diameter ana tico inches long. foment alli-u.lt TJieorrtical dis- Ri-il ilivhargei in the it the Wi-n in chir^.5 'hrnn^li a * ilnc: tinir l.y > cy- Ratio of the throrcticil itHivr !(]< (t, n. circular orifice one nu h ID diameter. in iliiiin-'ir .iii.l livo to the real discharge* of the i s.? Oj O U PS 2 u 1 7-62 3-27 4-16 21-63 130 6 90-07 2 10-77 4-62 5-88 15-31 92 6 90-16 3 13-20 5-66 7-20 12-50 100 8 90-00 4 15-24 6-53 8-32 10-81 97 9 89-67 5 17-04 7-30 9-28 9-70 97 10 90-02 6 18-67 8-00 10-19 8-83 97 11 89-86 7 20-15 8-64 10-99 . 8-19 90 11 89-92 8 21-56 9-24 11-76 7-65 84 11 89-80 9 22-86 9-80 12-47 7-22 72 10 89-68 10 24-10 10-33 13-15 6-84 82 12 89-86 11 25-27 10-83 13-79 6-53 85 13 90-16 12 26-40 11-31 14-40 6-25 75 12 90-00 13 27-47 11-77 14-99 6-00 72 12 89-94 14 28-51 12-22 15-56 5-78 75 13 89-77 15 29-52 12-65 16-13 5-58 67 12 90-06 16 30-48 13-06 16-63 5-41 65 12 90-06 17 31-42 13-46 17-14 5-25 63 12 89-99 18 32-33 13-86 17-65 5-10 61 12 89-72 19 33-22 14-24 18-13 4-96 60 12 90-65 20 34-17 14-64 18-64 4-83 58 12 90-09 It is desirable that the millwright should possess short easy rules, which would answer the purposes of practice rather than the conditions of mere theory. The following will be found useful, as they give the power with allowance for friction and waste of water. WATER WHEELS. 213 For an undershot : Height of fall X quantity of water flowing per minute DOOQ the number of horses' power which the effect is equal to. For an overshot : Power of an undershot X 2| = horses' power. For a breast-wheel : Find the power of an undershot from the top of the fall to where the water enters the bucket ; then for an overshot for the rest of the fall the sum of these two is the power of the breast wheel. NOTE. The quantity of water flowing per minute, ana the height of the fall are both taken in feet. Ex. What power can be obtained from an undershot wheel the fall being 25 feet, the section of the stream being 9 feet, and the velocity of the water 18 feet per minute? 9 x 18 X 25 4050 5000 5000 one horse power being unit. And an overshot in the same situation would be '81 X 2-5 == 2-025 horses' power. And if, in a breast wheel, the water enters the bucket 10 . r eet from the top of the fall, then we have, 10 X 8 X 9 ol _ 720 o , _ 1800-0 _ ~~5000~ ~~5000 X : 5000 = for an overshot, and for the undershot we found it before 81 ; hence, '36 + '81 = 1-17 horses' power for the breast wheel. BARKER'S MILL. IN plate 1st, fig. 4, we have given a view of Barker's mill, where CD is a vertical axis, moving on a pivot at D, and carrying the upper millstone m, after passing through an opening in the fixed millstone C. Upon this axis is fixed a vertical tube TT communicating with a horizontal rube AB, at the extremities of which A, B, are two aper- tures in opposite directions. When water from the mill- course MN is introduced into the tube TT, it flows out of the apertures A, B, and by the reaction or counterpressure of the issuing water, the arm AB, and consequently the 214 HYDRODYNAMICS. whole machine, is put in motion. The bridge-tree ab is elevated or depressed by turning the nut c at the end of the lever cb. In order to understand how this motion is produced, let us suppose both the apertures shut, and the tube TT filled with water up to T. The apertures A, B, which are shut up, will be pressed outwards by a force equal to the weight of a column of water whose height is TT, and whose area is the area of the apertures. Every part of the tube AB sustains a similar pressure ; but as these pressures are balanced by equal and opposite pres- sures, the arm AB is at rest. By opening the aperture at A, however, the pressure at that place is removed, and consequently the arm is carried round by a pressure equal to that of a column TT, acting upon an area equal to that of the aperture A. The same thing happens on the arm TB ; and these two pressures drive the arm AB round in the same direction. This machine may evidently be ap- plied to drive any kind of machinery, by fixing a wheel upon the vertical axis CD. This ingenious machine has not been much employed, even in those situations for which it is best adapted ; partly, we suspect, from the millwright's riot having in his posses- sion sufficiently simple rules for its construction ; as the theory of Barker's mill, simple as its construction and action may appear, is not by any means well developed. In the mean time the following directions may be found useful to the mechanic. 1. Make each arm of the horizontal tube, from the centre of motion to the centre of the aperture of any convenient length, not less than ^ of the perpendicular height of the water's surface above these centres. 2. Multiply the length of the arm in feet by -61365, and the square root of this product will be the proper time for a revolution, in seconds ; then adapt the other parts of the machinery to this velocity ; or, If the time of a revolution be given, multiply the square of this time by 1-6296 for the proportional length of the arm in feet. Multiply together the breadth, depth, and velocity per second of the race, and divide the last product, 14-27 X the square root of the height ; the result is the area of either aperture ; or, multiply the continual product of the breadth, depth, and velocity of the race, by the square root BARKER'S MILL. 215 of the height, and by the decimal -07, the last product divided by the height will give the area of the aperture. Multiply the area of either aperture by the height of the head of water, and this product by 55*795 (or, in round numbers, 56) for the moving 1 force, estimated at the centres of the apertures in Ibs. avoirdupois. Ex. If the fall be 18 feet from the head to the centre of the apertures, then the arm must not be less than 2 feet, as^of 18 = 2, and,/ (2 x -61305) = v/( 1-22730) = 1-107 the time of a revolution in seconds; also, the breadth of the race being 17 inches, and depth 9, and the velocity of the water 6 feet per second, here we have, 17 in. = 1-41 feet, and 9 in. = -75 feet, then 1-41 x '75 x 6 = 6-34 = the area of section of the race x velocity of water ; hence, 6-39 x N/ 18 X -07 = 1-896 = the area of the aperture in inches ; and, 1-876 x 18 X 56 = 1909 Ibs. the moving force. The following dimensions have been employed in prac- tice with success. The length of arm from the centre pivot to the centre of the discharging hole, 46 inches ; inside diameter of the arm, 13 inches ; diameter of the supplying pipe, 2 inches ; height of the working head of water 21 feet above the level of the discharge. When a machine of these dimensions, and in such circumstances, was not loaded and had one orifice open, it made 115 turns in a minute. PNEUMATICS. PNEUMATICS comprehends the knowledge of the proper- ties of common air and elastic fluids in general. Air is capable of being compressed to almost any degree, that is, may be forced into a space infinitely smaller than the space which it commonly occupies, and this is effected by additional pressure. When this additional pressure is taken away, the air will regain, by its elasticity, its former magnitude. Were it not for this circumstance, the subject of this chapter might have been introduced when we dis- cussed the equilibrium and motion of water and fluids, which are non-elastic or incompressible, as their fundamen- tal laws are the same. It has, indeed, been found oy recent experimenters, that water, mercury, &c., are compressible, but to a very limited degree ; so that although the distinction of elastic and non-elastic fluids is not absolutely correct, it is yet sufficiently so to retain Pneumatics, in elementary arrangement, as a distinct branch of science. The air or atmosphere is a fluid body which surrounds (he earth, and gravitates on all parts of its surface. The mechanical properties of air are the same as other elastic fluids, and being the most common, inquiries in pneumatics are generally confined to this fluid. The air has weight. A cubic foot of it weighs 1 P 2857 ounces at the surface of the earth, or, as some state it, 1'222. The air being an elastic fluid, it is compressible and ex- pansible, and its degrees of compression and expansion are proportional to the forces or weights which compress it. All the air near the earth's surface is in a state of com- pression, in consequence of the weight of the atmosphere which is above it. As the less weight that presses the air compresses it the less, or causes it to be less dense, and as the higher we rise in the atmosphere there will be the less weight, so the higher we go in the atmosphere the air will be the less dense. 2Jfi OF THE ATMOSPHERE. 217 The spring or elasticity of the air is equal to the weight of the atmosphere above it, and they will produce the same effects since they always sustain and balance each other. It' the density of the air be increased by compression, its spring or elasticity is also increased, and in the same pro- portion. By the pressure and gravity of the atmosphere on the surface of fluids such as water, they are made to rise in pipes or vessels, where the spring or pressure Within is taken off or diminished. This fact, a knowledge of which is applied to a multitude of useful purposes, will uot be difficult of explanation. L*it a tube 3 feet long bo filled with water, the tube being open at one end and close at the other; one unacquainted witn the subject might naturally expect that if this tube were held perpendicularly with the open end downmost, the water would flow out of *he tube by reason of its weight. But if we consider all the c.ireum- stances, we will see that this can only happen on certain conditions. The water has a tendency to fall to thr earth in consequence of its weight, but then the air of the aL:no- sphere, which we have stated before as also possessed of weight, presses upon the surface of the water at the r.pen end of the tube ; and as the pressure of fluids of t-Il kinds is exerted in every direction, it follows, that the \\r will have a tendency to force the water up the tube. Now the pressure of the atmosphere at the surface of the earth is about 15 Ibs. for every square inch, which is therefore the force by which the water will be pressed up the tube by the action of the air. A column of water 3 feet high does not exert such a pressure on the base ; wherefore , as the pressure upwards is greater than the pressure downwards, the water will remain suspended in the tube. Let us now take a tube 36 feet long, similar to the former, filled with water and inverted in the same way as before, it will now be found that a part of the water will tlow out of the tube, the reason of which will be easily seen. , It was stated under Hydrostatics, that the pressure of a column of water 30 feet high was equal to 13 Ibs. on the /quare inch. So that we see, that the pressure of the air will keep 30 feet of the water in the tube, but it will keep more, for the pressure of the air is 15, and that of 30 feet of water is only 13 ; and as the pressure of the water will be as its depth, we say, 13 : 15 : : 30 : 34, which, there- 19 PNEUMATICS. fore, is the greatest height at which the water will be sup- ported by the pressure of the atmosphere. For the purpose of arriving at this conclusion of the effect of the pressure of the atmosphere, we might have employed a much shorter tube if we had used a heavier fluid than water, for instance, mercury. Now the cubic foot of mercury weighs 13600 ounces, and a cubic inch will be found, 13600 = 7-866 ounces, or nearly 8 ounces, that is about half a pound avoirdupois ; therefore 30 inches will weigh 15 Ibs., hence, the atmo- sphere will balance by its pressure 30 inches of mercury. Thus we have arrived at the principle of the barometer, or weather glass, as it is commonly called. The pressure of the air at the surface of the earth is not always constant, but varies within certain limits. The mean pressure is about 14 Ibs. to the square inch, and the corresponding height of the mercury in the barometer will therefore be 15 : 14 : : 30 : 28 inches. It will appear evident, from what has been said before, that as the higher we. ascend in the atmosphere there will be less pressure, and therefore the mercury in the barometer will fall, and this fact has been used as a means of measur- ing heights by the barometer. If the air were of the same uniform density up to the top of the atmosphere as it is at the earth's surface, we might very easily determine its height, for the specific gravity of air being to that of water as 1-222 to 1000, nearly, we have this proportion, 1'222 : 1000 : : 33-25, (the mean height of a water barometer in feet,) : 27200 feet, which is very nearly 5| miles ; but by a process which proceeds on correct principles, .the height of the atmosphere has been estimated at about 50 miles. The law of the diminution of density at different heights in the atmosphere is this, that if the heights increase in arith- metical progression, the densities will decrease in geometri- cal progression; for instance, if the density at the surface of the earth be called 1, and if at the height of 7 miss it be called 4 times rarer than at 14 16, 21 it will be 64 times rarer, 28 256, 35 1024, PRESSURE OK THE ATMOSPHERE. 219 and in this way it might be shown, that at the height of one- half the diameter of the earth, one cubic inch of atmospheric air of the density which we breathe, would expand so much as to fill the bounds of the solar system. Many eminent men have investigated this subject, and derived theorems of great use for determining altitudes by the barometer. Some of these are exceedingly complex and unfitted for a work of this nature : that of Sir J. Leslie is the most simple, and gives results sufficiently near the truth for all ordinary purposes. As the sum of the heights of the mercury at the bottom and top of the mountain is to the difference of the heights, so is 52000 to the altitude of the mountain in feet. At the bottom of a hill the barometer stood at 29'8, and at the top 27*2, wherefore, 29-8 + 27-2 = 57 = the sum, and 29-8 27-2 = 2-6 = the difference ; hence, 57 : 2*6 : : 52000 : 2372 feet, the height of the mountain nearly. When air becomes denser, its elastic force is increased, and that in proportion. Thus, when air is compressed into half its bulk, its elastic force will be double of what it was before. It will, therefore, be easy to calculate the elastic force of air compressed any number of times ; thus, if, by any means, we condense the air in a vessel into of the space which it occupied when not confined, it will press on the inside of the vessel with a force of 15 X 3 = 45 Ibs. on every square inch. It must be remembered, however, that the atmosphere presses with a force of 15 Ibs. on each square inch of the outside of the vessel, which therefore counter- acts so much of the force of the condensed air within the real pressure, therefore, is 45 15 = 30 Ibs. It is clear, then, that whatever be the degree of condensation of the enclosed air, we must always deduct the pressure of the at- mosphere to ascertain its true effect. The young mechanic will easily understand what is meant by the phrase a pressure of 2, 3, 4, or any number of atmospheres, one Atmosphere being understood as exerting a pressure of 15 Ibs. on the square inch, two atmospheres 30, and three 45, &c. When the air is by any means entirely taken out of sny vessel, there is said to be a vacuum in that vessel. What is the whole amount of pressure on the inside sur- 220 PNEUMATICS. (ace of a sphere, which contains air condensed to | of its natural bulk, and is 6 inches in diameter within. Here, by mensuration, we have, 6- X 3-1416 = 113-0976 = the surface of the inside of the sphere and 15 x 4 15 = 45 = the pressure on a square inch, therefore, 113-0976 X 45 = 5089-3920 Ibs. on the inner surface of the globe. Here the globe is supposed to be in a vacuum. In a cylinder 6 feet long, and closed at the bottom, a pis- ton is thrust down to the distance of one foot from the bot- tom, the cylinder being 24 inches in diameter, then, by the rules in mensuration, the area of the piston will be found to be 452-4 inches, the diameter of the piston being 24 inches, and the cylinder being 6 feet long, and the piston being pressed down to 1 foot from the bottom, the air will be com- pressed into -g- of its former bulk, and its elastic force will be 6 times greater than it was before. At first it was 15 Ibs. to the square inch, but now it will be 15 X 6 = 90 on the square inch, and one atmosphere being deducted for the contrary pressure of the atmosphere above the piston, the pressure is 90 15 = 75 Ibs. to the square inch, where- fore, 452-4 x 75 = 33930 Ibs., the force by which the piston will be pressed upwards. THE SYPHON. A SYPHON, or, as it is frequently written, siphon, is any bent tube. If a syphon be filled with water and inverted, so that the bend shall be uppermost, then if the legs be of equal length, and it be held so that the two lower ends of the syphon are on a level, then we will find that if the perpen- dicular height of the bend of the tube above the level of the two ends be not more than 32 or 33 feet, the water will re- main suspended in the tube. It will not be difficult to see how this happens, for the atmosphere pressing on the water at the orifice of the tube at each extremity, presses the water up the tube with a force capable of raising it 33 feet ; but in the case supposed, the orifices and the legs are equal, and do not exceed the limit of 32 or 33 feet, therefore, since the pressure on one orifice is the same as the pressure on the other, there will be an equilibrium and the water in the one leg has no more power to move than that in the other. If we now suppose the syphon to be inclined a little, so PUMPS. 221 that the twc orifices shall not be on a level, or what is the same thing, if we suppose the length of the one leg to be greater than that of the other, we will find that the equi- librium will be no longer maintained ; and the water will flow out of the orifice which is lowest. For although the air presses equally on both orifices with a force of 15 Ibs. to the square inch, yet the contrary pressures downwards by the weight of the water are not equal, therefore motion will ensue where the power of the water is greatest. If the shorter leg be immersed in a vessel of water, and the syphon be set a running, the water will flow out of the lower end of the syphon, until the other end be no longer supplied. Instead of filling the syphon with water, as has been supposed above, a common practice is to apply the mouth to the lower orifice, and by sucking, exhaust the air in the tube, which diminishes the pressure at the other orifice, and consequently the action of the atmosphere will force the water in the vessel up the tube of the syphon and fill it, and it will continue to act in the same way as before. PUMPS. A PUMP is a machine used for exhausting vessels con- taining air, or for raising water, sometimes by means of the pressure of the atmosphere, sometimes by the condensa- tion of air, and sometimes by a combination of both. It may be necessary here to explain what is meant by the term valve, that our remarks on the action of the pump may be rendered more intelligible. A valve is usually defined to be a close lid affixed to a tube or opening in a vessel, by means of a hinge or some sort of movable joint, and which can be opened only in one direction. There are various kinds of valves. The clack valve consists merely of a circular piece of leather covering tlje hole or bore of the pipe which it is intended to stop, .and moving on a hinge, sometimes a part of itself, and sometimes made of metal. The butterfly valve, which is superior to the clack valve, consists of two pieces of leather each formed into the shape of a half circle ; they are at- Aached by hinges on their diameters, or straight parts, to a bar that crosses the centre of the orifice to be closed. The button or conical valve consists of a plate of brass ground in such a way as exactly to fit the conical cavity in which it lies. Sometimes valves are made in the form of pyramids 19* 222 PNEUMATICS IB consisting of four triangular flaps which form the "sides of the pyramid, and move upon hinges which are placed round the edge of the orifice to be closed. The tops of these flaps must all meet accurately in the middle of the orifice and are supported by four bars which meet in the centre. The action of the air pump may be thus explained. Le' R be the section of a glass bell, called a receiver, closed at the top T, but open at the bottom, and having its lower edge ground smooth, so as to rest in close contact with a smooth brass plate, of which SS is a section. In the middle is an opening A, which communicates by a- tube AB with a hollow cy- linder or barrel, in which a solid piston P is moved. The piston rod C moves in an air-tight collar D, and at the bottom of the cylinder a valve V is placed, opening freely outward, but immediately closed by any pressure from without. There is thus a free communication between the receiver R, the tube AB, and the exhausting barrel BV. When the piston CP is pressed down, and has passed the opening at B, the air in the barrel BV will be enclosed, and will be compressed by the piston. As it will thus be made to occupy a smaller space than before, its density, and con- sequently its elasticity, will be increased. It will therefore press downwards upon the valve V with a greater force than that by which the valve is pressed upwards by the external air. This superior elastic force will open the valve, through which, as the piston descends, the air in tke barrel will be driven into the atmosphere. If the piston be pushed quite to the bottom, the whole air in the barrel will be thus expelled. The moment the piston begins to ascend, the pressure of the air from without closes the valve V com- pletely, and, as the piston ascends, a vacuum is left beneath it; but, when it rises beyond the opening B, the air in the receiver R and the tube AB expands, by its elasticity, so as to fill the barrel BV. A second depression of the piston will expel the air contained in the barrel, and the process PUMPS. 223 may be continued at pleasure. The communication be- tween the barrels and the receiver may be closed by a stop- cock at G. In consequence of the elasticity of the air it expands and fills the barrel, diffusing itself equally through- out the cavity in which it is contained. The degree of rarefaction produced by the machine may, hojivever, be easily calculated. Suppose that the barrel contains one- third as much as the receiver and tube together, and, there- fore, that it contains one-fourth of the whole air within the valve V. Upon one depression of the piston, this fourth part will be expelled, and three-fourths of the original quan- tity will remain. One-fourth of this remaining quantity will in like manner be expelled by the second depression of the piston, which is equal to three-sixteenths of the ori- ginal quantity. By calculating in this way, it will be found that after thirty depressionsAf the piston, only one 3096th part of the original quantity will be left in the receiver. Rarefaction may thus be carried so far that the elasticity of the air pressed down by the piston shall not be sufficient to force open the valve. We now proceed to the consideration of the common suction pump. This pump consists of a hollow cylinder A, of wood 'or metal, which contains a piston B, stuffed so as to move up or down in the cy- linder easily, and yet be air tight : to this piston there is attached a rod which will reach at least to the top of the cylinder when the piston is at the bottom. In the piston there is a valve which opens upwards, and at the bottom of the cylinder there is another valve C also rising upwards, and which covers the orifice of a tube fixed to the bottom of the cy- linder, and reaching to the well from whence the water is to be drawn. This tube is commonly called the suction tube, and the cylinder, the body of the pump. From what has been said of the pressure of the atmo sphere, it will not be difficult to understand how this ma- diine operates. For when the piston is at the bottom of the cylinder, there can be no air, or at least very little, between it and the valve C, for as the piston was pushed clown, the valve in it would allow the air to escape instead of being condensed, and when it is drawn up, the pressme of the air would shut 'he valve, and there would be a vacuum produced ffl 224 PNEUMATICS. in the body of the cylinder when the piston arrived at the top. But the air in the cylinder being very much rarifisd, the pressure of the valve C on the water at the bottom will be greatly less than that of the external atmosphere on the surface of the water in the well ; therefore, the water will be pressed up the pump to a height not exceeding 32 or 33 feet. As the valves shut downwards, the water is pre- vented from returning, and the same operation being repeated, the water may be raised to any height, not exceeding the above limit, in any quantity. The quantity of water discharged in a given time, is de- termined by considering that at each stroke of the piston a quantity is discharged equal to a cylinder whose base is the area of a cross section of the body of the pump, and height the play of the piston. Thus, if the diameter of the cylin- der of the pump be 4 inches^nd the play of the piston 3 feet, then, by mensuration, we have to find the content of a cylinder 4 inches diameter, and 3 feet high now, 4 inches is the f of a foot, or -333, hence, -333 a x '7854 = -110999 X '7854 = -08796 = the area of the cross section of the cylinder in square feet; hence, -08796 X 3 = -2639 = the content of the cylinder in cubic feet = the quantity in cubic feet of water discharged by one stroke of the piston. Now, a cubic foot of water weighs about 63-5 Ibs. avoirdu- pois, wherefore, -2639 x 63-5 = 16-756 Ibs. avoirdupois, and an imperial gallon is equal to 10 Ibs. of water ; whence, dividing the above number 16-756 by 10, we get the num- ber of ale gallons = 1-6756. The piston, throughout its ascent, has to overcome a resistance equal to the weight of a column of water, having the same base as the area of the piston, and a height equal to the height of the water in the body of the pump above the water in the well. In our calculations of the effects of the pump, it will be necessary to determine the contents of pipes, for which purpose the following simple rules will serve. Diameter of pipe in inches 8 = number of avoirdupois pounds contained in 3 feet length of the pipe. If the last figure of this be pointed off as a decimal, the result will be the number of ale gallons, and if there be only one figure this is to be considered as so many tenths of an ale gallon : ale gallons x 282 = the. number of cubic inches. Thus, in a pipe 5 inches diameter, we have, PUMPS. 225 5 9 = 25 = number of avoirdupois pounds contained in 3 feet of the pipe 2-5 = the number of ale gallons and 2'5 x 282 = 705 cubic inches. These rules find the content for three feet in length of the pipe, the content for any other length may be found by proportion; thus, for a pipe 6 inches in diameter, and IV feet long ; we have, 6 a = 30 = pounds of water avoir, con- tained in the pipe to the length of 3 feet ; therefore, 3 : 12 : : 36 : 144 = the number of pounds in 12 feel length, and, 14-4 = ale gallons, and 14'4 X 282 = 4060-8 = the cubic inches in 12 feet length. The resistance which is opposed to a pump rod in raising water, is equal to the weight of a column of water whose base is the area of the piston, and height the height of the surface of the water in the body of the pump above the surface of the water in the well, together with the friction and the piston and piston rod. Suppose the body of the pump to be 6 inches in diifmeter, and the height to which the water is raised be 30 feet, and also the weight of the piston and rod is 10 Ibs., and the friction is - of the whole weight of the water. Now, fi 8 = 36 = the Ibs. avoirdupois of 3 feet of the column of water, but the column is 30 feet, therefore, 3 : 30 : : 36 : 360 Ibs., the weight of the whole column. To this we must add the effect of friction, which we have sup- posed to be y of the weight of the water ; hence, ^fid ' = 72 Ibs., and this must be added to the weight of D the column of water, which gives 360 + 72 = 432 Ibs. the whole amount of resistance arising from the weight of the water and friction ; to this must be added the weight of the piston and pump rod, therefore, 432 -\- 10 = 442 = the whole resistance opposed to the rising of the piston, any thing greater than this will raise it. In the construction of pumps it is usual to employ a lever to work the piston, which gives an advantage in power ; *and if in the case estimated above, we employ a lever who? e 'arms are in the proportion of 10 to 1, the pump might te wrought with a force of 44*2 Ibs., or we may say 45 Ibs. For the convenience of workmen we insert the following table. It has been calculated on the supposition that the handle of the pump is a lever which srives an advantage on 22C PNEUMATICS. the piston rod of 5 to 1, and that a man can, with a pump 30 feet long, and a 4 inch bore, discharge 27'5 wine gallons (oil measure) in a minute. And if it be required to find the diameter of a pump that a man could work with the same ease as the above pump at any required height above the surface of the well, this table will give the diameter of l-ore, and the quantity of water discharged in a minute. Height of (lie pump above the surfc.ee of the mill in feet. Diameter of the bore where the piston works iu iuchei. Water discharged per gallons and pints. 10 6-93 81 6 15 5-66 54 4 20 4-90 40 7 25 4-38 32 6 30 4- 27 2 35 3-70 23 3 40 3-46 20 3 45 3-27 18 1 50 3-10 16 3 55 2-95 14 7 60 2-84 13 5 65 2-72 12 4 70 2-62 11 5 75 2-53 10 7 80 2-45 10 2 85 2-38 9 5 90 2-31 9 1 95 2-25 8 5 100 2-19 8 1 We stated before that water could not be raised to a greater height than 32 feet by means of the kind of pump we have described, and it may seem strange that this table extends to 100 ; but these are pumps acting on a different principle, by means of which water may be raised to any height, and whose action will be considered before we leave this subject. The lifting pump. This pump, like the suction pump, has . two valves and a piston, both opening upwards ; but the valve in the cylinder, instead of being placed at the bottom of the cylinder, is placed in the body of it, and at the height PtJMPS. 227 where the water is intended to be delivered. The bottom of the pump is thrust into the well a considerable way,, and if the piston be supposed to be at the bottom, it is plain, that as its valve opens upwards, there will be no obstruction to the water rising in the cylinder to the height which it is in the well ; for, by the principles of Hydrostatics, water will always endeavour to come to a level. Now when the piston is drawn up, the valve in it will shut, and the water in the cylinder will be lifted up ; the valve in the barrel will be opened, and the water will pass through it, and can- not return, as the valve opens upwards ; another stroke of the piston repeats, the same process, and in this way the water is raised from the well : but the height to which it may be raised, is not in this, as in the suction pump, limited to 32 or 33 feet. To ascertain the force necessary to work this pump, we are to consider that the piston lifts a column of water whose base is the area of the. piston, and height the distance between the level of the water in the well and the spout, at which the water is delivered. Thus, -if the diameter of the pump's bore be 4 inches, and the height of the spout above the level of the well = 40 feet, then we have 4 2 = 16 Ibs. in three feet of the barrel; wherefore, 3:40::16:213j Ibs. the weight of the water, and the friction and weight of the piston and rod must be added to this, to find the whole force necessary. If the friction be reckoned, as it usually is, ][, then we have, wherefore, 213 -|- 42 = 255; as we have neglected frac- tions we may reckon it 256, and if the weight of the piston and rod be 20 Ibs. the whole will be 256 -f 20 = 276 Ibs.. the whole force necessary to balance the piston ; any thing greater than this will raise it. The forcing pump remains to be consi- dered. The piston of this pump has no valve, but there is a valve at the bottom of ,the cylinder, the same as seen at A. In the side of the cylinder, and immediately above tl/e valve B, there is another valve A open- ing outwards into a tube which is bent up- wards to the height H at which the water is to be delivered. When the piston is raised, the valve in the bottom of the pump 228 PNEUMATICS opens, ana a vacuum being produced, the water is pressed up into the pump on the principle of the sucking pump But when the piston is pressed down, the valve A at the bottom shuts, and the valve B at the side which leads into the ejection pipe opens, and the water is forced up the tube. When the piston is raised again the valve B shuts, and the valve A opens. The same process is repeated, and the water is thrown out at every descent of the piston, the dis charge therefore is not constant. It is frequently required that the dis- charge from the pump should be continu- ous, and this is effected by fixing to the top of the eduction pipe an air vessel. This air vessel consists of a box AB, in the bottom of which there is a valve C opening upwards into the box. This valve covers the top of the eduction pipe D. A tube, E, is fastened into the top of the box, which reaches nearly to the bottom of the box, it rises out of the box, and is furnished with a stop cock. If the stop cock be shut, and the water be sent by the action of the pump into the air vessel, it cannot return because of the shutting of the valve at the bottom of the box ; and be- cause of the space occupied by the water, the air in the box is condensed, and will consequently exert a pressure on the water in the air vessel. If the water fill three-fourths of the box, then the air will be compressed so as to exert four times its original force ; and the stop cock being opened, the water will be forced up the tube, with a force which will send it one less than as many times 32 feet as the air is compressed, that is, in the case supposed 3 X 32 = 96 feet. On this principle it is that jets of fountains act. The air vessel may therefore be considered as a magazine of power, and so long as there is as much water forced into the fir vessel by pumping, as there is forced out by the pressure of the air, there will be a constant jet of water. The force necessary to raise the piston in this pump, is found exactly in the same way as for the suction purnp. And the force necessary to depress the piston, is found by taking the weight of a column of water, whose height is equal to the height of the spout where the water is de- livered above the level of the piston, before it begins to descend Thus, if the piston when raised is 26 feet above WINDMILLS. 229 the level of the well, and the spout is 63 feet above the same level, therefore, the height of the column* is 63 26 = 37 feet; and supposing the diameter of the ejection pipe to be 5 inches, we have for 3 feet of the pipe 5 a = 25 Ibs.. wherefore for 37 feet we have, 3 : 37 :: 25 : 308 1 Ibs. The weight of the piston and its rods oppose the raising of the piston, but assist in depressing it. The power applied to the piston rod of a suction pump should be an intermitting power, otherwise there will be a waste of .power ; but in a forcing pump the power must be continued throughout equable. A single stroke steam en- gine will be best to raise water by the sucking, and a double stroke by a forcing pump. The piston rod of a forcing pump should be loaded with a weight sufficient to balance a column of water, whose base is the section of the piston, and whose height is the excess of the height of the spout from the level of the water in the cistern above 68 feet. This will cause a regular application of power when this pump is wrought with a steam engine. WIND AND WINDMILLS. WE have seen the effect of the pressure of air, arising from its weight and elasticity when at rest ; it now remains for us to consider its effects when put in motion, as in the case of wind. Were it not for the irregularity in direction and force of the wind, it would be the most convenient of all the first movers of machinery, but even as it is, its efficacy may be taken advantage of, and deserves our consideration. The force with which wind strikes against a surface, is as the square of the velocity of the wind. This simple theorem is so nearly true that it may be employed without fear of error. The force in avoirdupois pounds with which the wind strikes on any surface on which it acts perpendicularly may be found by using the rule, surface struck x velocity of wind 3 x '002288 ; \vhere the surface and velocity of wind are taken in feet, amd the time 1 second. If the wind moves at the rate of 30 feet per second, and the surface exposed to it. action be 14 feet square, then, 14 x 30 3 x '002288 = 28-8288. From this statement it might appear at first sight, that iu 20 830 PNEUMATICS. the case of mills winch act by the impulse of wind on re- . volving surfaces called sails it might appear, we say, that the greater quantity of sail exposed to the action of the wind, the greater would be the effect of the machine. But this has been found not to hold : it would appear that the wind requires space to escape. The sails of the windmill may be supposed to intercept a cylinder of wind ; and it would seem, that when the whole cylinder is intercepted, the effect of the machine is diminished ; and it is concluded from experiments, that the sails should not intercept above seven-eighths of the cylinder of the wind. We here subjoin a tabular view of the effects of wind at different velocities. Table showing the pressure of the Wind for the following Velocities. Velocity of the Wind. Force upon 1 square foot in pounds avoir. Miles in 1 hour. Feet in 1 second. 1 1-47 005 2 2-93 020 3 4-40 044 4 5-87 079 5 7-33 123 10 14-67 492 15 22-00 1-107 20 29-34 1-968 25 36-67 3-075 30 44-01 4-429 35 51-34 6-027 40 58-68 7-873 45 66-01 9-963 50 73-35 12-300 60 88-02 17-715 80 117-36 31-490 100 146-70 49-200 Windmills are constructed either so that the sails shall move in a horizontal plane, or in a plane nearly vertical ; their former are called horizontal, and the latter vertical windmills. In plate 2,, fig. 1 and 2, we have given a plan and section of a horizontal windmill, on an improved con- WINDMILLS. 231 struction. HH are the side walls of an octagonal building which contains the machinery. These walls are surmounted by a strong timber framing GG, of the same form as the building, and connected at top by cross-framing to support the roof, and also the upper pivot of the main vertical shaft AA, which has three sets of arms, BB, CC, DD, framed upon it at that part which rises above the height of the walls. The arms are strengthened and supported by diagonal braces, and their extremities are bolted to octagonal wood frames, round which the vanes or floats EE are fixed, as seen in outline in fig. 2, so as to form a large wheel, resembling a water wheel, which is less than the size of the house by about 18 inches all round. This space is occupied by a number of vertical boards or blinds FF, turning on pivots at top and bottom, and placed obliquely, so as to overlap each other, and completely shut out the wind, and stop the mill, by forming a close case surround- ing the wheel ; but they can be moved altogether upon their pivots to allow the wind to blow in the direction of a tangent upon the vanes on one side of the wheel, at the time the other side is completely shaded or defended by the boarding. The position of the blinds is clearly shown at FF, fig. 2. At the lower end of the vertical shaft AA, a large spur-wheel aa is fixed, which gives motion to a pinion c, upon a small vertical axis rf, whose upper pivot turns in a bearing bolted to a girder of the floor n. Above the pinion c, a spur-wheel e is placed, to give motion to two small pinions f, on the upper ends of the spindles g, of the millstone n. Another pinion is situated at the opposite side of the great spur-wheel aa, to give motion to a third pair of millstones, which are used when the wind is very strong ; and then the wheel turns so quick as not to need the extra wheel e to give the requisite velocity to the stones. The weight of the main vertical shaft is borne by a strong timber 6, having a brass box placed on it to receive the lower pivot of the shaft. It is supported at its 'ends by cross-beams mortised into the upright posts 66, as sjnown in the plan, fig. 2. A floor or roof 1 1 is thrown across the top of the brick building to protect the machinery from the weather, and to prevent the rain blowing down the opening through which the shaft descends, a broad cir- cular hoop K is fixed to the floor, and is surrounded by another hoop or case L, which is fixed to the arms DD of 23 PNEUMATICS. the wheel. This last is of such a size, as exactly to go over the hoop K, without touching it when the wheel turns round. By this means, .the rain is completely excluded from the upper room M, which serves as a granary, being fitted up with the bins mm, to contain the different sorts of grain which is raised up by the sack-tackle. A wheel i is fixed on the main shaft, having cogs projecting from both sides. Those at the under side work into a pinion on tho end of the roller K, which is for the purpose of drawing up sacks. Another pinion is situated above the wheel i, which has a roller projecting out over the flap-doors seen at p, in fig. 2, to land the sacks upon. The two pinions mm, fig. 2, are turned by the great wheel act, and are for giving motion to the dressing and bolting machines, which are placed upon the floor N, but are not shown in the drawing, being exactly similar to the dressing machines used in all flour-mills. The cogs upon the great wheel a are not so broad as the rim itself, leaving a plain rim about three inches broad. This is encompassed by a broad iron hoop, which is made fast at one end to the upright post b ; the other being jointed to a strong lever n, to the extreme end of which a purchase o is attached, and the fall is made fast to iron pins on the top of a frame fixed to the ground. This apparatus answers the purpose of the brake or gripe used in common windmills to stop their motion. By pull- ing the fall of the purchase 0, it causes the iron strap to em- brace the great wheel, and produces a resistance sufficient to stop the wheel. The mill can be regulated in its motion, or stopped entirely, by opening or shutting the blinds F, which surround the fan-wheel. They are all moved at once by a circular ring of wood situated just beneath the lower ends of the blinds upon the floor 1 1, being connected with each blind by a short iron link. The ring is moved round by a rack and spindle which descend into the mill room below, for the convenience of the miller. The mode of bringing the sails back against the wind, which Mr. Beatson invented, is, perhaps, the simplest and best for that end. He makes each sail AI, fig. 3, to consist of six or eight flaps or vanes, AP b 1, b I c 2, quare inches, is this, The diameter x circumference - = area. 4 Here we have, 30 X (30 x 3-1416) 2827-44 = 706-86, 4 4 equa the area of the piston in square inches ; and 12 the effective pressure, 6 the length of stroke, 16 the number of double strokes in a minute ? 706 86 Xl2x6xl6x2_ 1628605*44 _ 44000~~ 44000 horses' power. If the cylinder of a higrh-pressure steam engine has a piston of 5 inches diameter, with a twelve inch stroke, making 32 double strokes in a minute ; steam being ad- mitted of an elastic force equivalent to 7 atmospheres on the inside of the cylinder. Its effective pressure will be 7 X 15 = 105 Ibs. to the square inch without friction; but al- lowing one-fifth for friction, the effective pressure will be 105 21 = 84 Ihs. to the square inch. 5 X (3-1416 X 5) here - - - - = 19-63 the area of the piston : 19-63 X 84 x 1 X 32 x 2 _ 105530-88 44000 " 44000 horses', power. A convenient rule for finding the power of a high-pres- sure engine, is let P be the force of the steam in the boiler, A the area of the piston, and V the velocity of the piston in feet per minute, then, 0-9 P _ 6 x A X V 44000 ^ The pressure of the steam in a boiler is 30 Ibs. per square inch, the diameter of cylinder 12 inches, length of 25tl STEAM ENOINE. stroke 3 feet, and the engine making 30 double strokes put minute. Here the area of piston will be 113-097, tho velocity of piston = 3 x 30 X 2 = 180 feet per minute and since 0-9 x 30 6 = 21, then, 0-9 x 30 6 X 113-097 X 180 427506-66 44000 9*7 horses' power. We might simplify this rule still farther on the consi deration, that the divisor 44000 may be viewed as the de nominator of a fraction whose numerator is one, and by converting this into a decimal, and multiplying by it, we might avoid the necessity of division. Since - = -0000227, hence we may devise the rule. 44000 Effective pressure of steam X area of piston in square inches x length of stroke in feet x number of strokes per minute x 227 ; and from the product cutting off seven places as decimals ; the horses' power of the engine. This is for a single stroke engine for a double stroke engine the multiplier is 227 X 2 = 454. If the cylinder be 42 inches diameter, and the piston moves 210 feet per minute, then the engine being low pressure, we have, area of cylinder equal 1385-44 ; hence 227 X 1385-44 X 210 X 12 = 792527097 : and the seven figures cut off as decimals, leave 79 horses' power. These are at best but approximations, and for safety it might be advisable that a lower- number than 12 should be employed, as the effective pressure of the steam ; the num her 10 may be used as being easily managed, and coming near the truth ; and thus the above rule may be simplified by neglecting the pressure of the steam, and cutting off six places for decimals instead of seven, as there is reason to believe that the above results will answer only ponies in- stead of strong horses. The stroke of an engine is commonly reckoned equal to one complete revolution of the crank shaft, and therefore double the length of the cylinder, and it has been stated by Mr. Thomas Tredgold, that to ascertain the velocity of the piston when the engine performs at its maximum, we may employ the rule, STEAM ENGINE. 257 120 X v/ length of stroke = velocity. If an engine has a two feet stroke, then, 120 X N/ 2 = 120 x 1-4142 = 109-704, or we may say 170, as the velocity of the piston per minute in feet ; wherefore as the engine has a single stroke of 2 feet we have, 170 = 42s strokes in the minute. 4 If an engine have a four feet stroke, then we have, 120 X v/ 4 = 120 X 2 = 240 = the velocity of the piston per minute ; and, 240 = 30, equal the number of strokes per minute, o The safety valves of most of the steam engines in this part of the country, are generally loaded with a weight of from 3 to 4 Ibs. to the square inch of their area; let us take 3 5 Ibs. in the present instance. The temperature of steam necessary to balance this pressure, is, according to the best experiments, 223 degrees of Fahrenheit's thermometer. But besides this sensible heat, there is a quantity of latent heat not indicated by the thermometer, and which can only be detected when the steam passes, by condensation, into the fluid state ; as the latent heat is then given out. Now, if the latent heat of the steam at the above temperature, be found on the principle stated in our remarks on heat, that the sensible and latent heats of steam at all temperatures, when added together, make a constant quantity ; we will find that the latent heat of steam at this temperature is 989. The real quantity of heat then in the steam is 223 -f 989= 1212 degrees. We will not be far from the truth in supposing, that one cubic foot of this steam will, when condensed into water, measure one cubic inch ; and the steam is supposed to be condensed by the injection of cold water. Now it is evident, that the temperature of the water formed by the condensation of the steam, will be somewhere between the temperature of cold waierandthe boiling point. Say that the temperature of the injected water is 50 degrees, and that the temperature of the water arising from the condensation of the steam is 100. We must deduct the 100 degrees from Lj:e heat of the uncondensed steam, that is, 1212 100 = H112, which is left to be communicated to the injection 22* 258 STEAM ENGINE. water , and since each cubic inch of the cold water requires 50 of heat to raise it to the temperature of the water found after the condensation of the sieam, therefore, 1 1 12 = 22 T 3 , cubic inches 50 of water necessary to condense one cubic foot of steam to the temperature of 100, the injected water being 50. From these considerations may be Serived a rule for de- termining the quantity of water necessary to condense any quantity of steam, at any given temperature. Total heat of the steam temperature of warm water temp, of warm water temp, of cold water quantity of steam in cubic feet = the quantity of cold water in cubic inches necessary to produce the effect. Let us illustrate this by an example. What quantity of cold water will it require of the temperature of 60, to con- dense 8 cubic feet of steam, of the temperature of 223, to water at 90 ? The whole heat is as before, 989 -f 223 = 1212, wherefore by the rule, 1212 90 X 8 = 299-2 cubic inches = 90 60 299-2 = *17 of a cubic foot of water. 1728 From this it will be easy to determine how much water must be discharged by the pump which feeds the condenser, in order that a proper vacuum may be formed. From practice it would appear that about 26 cubic inches of cold water for condensing should be used for each cubic foot of the capacity of the cylinder. We may infer from observation, that the engines com- monly in use require betwixt 3| and 4 gallons of cold water per minute for each horse's power. If the water is return- ed as it is in some engines, then a greater quantity will be necessary. Now, in the usual construction of engines, the pump rod which supplies the condenser with cold water, is fixed halfway between the end of the beam and the cen- tre ; hence, the length of its stroke is one-half that of the piston in the large cylinder: therefore, if there be a 40 horse power engine, the length of whose stroke is 6 feet, the length of the stroke of the pump will be 3 feet. Now an imperial wine gallon occupies a space of 277'274 STKAM KNGI.M:- 259 cubic inches, and 71 Dillons will occupy a space of 277'274 X 7'5 = 2079-555 cubic inches; and as the engine is 40 horses' power, there must be discharged in one minute, 2079-555 x 40 = 83182-2 cubic inches, and if the engine makes 30 strokes per minute, then 83182-2 = 277-274 cubic inches 30 discharged at one stroke : but the stroke is 3 feet long, and it remains only to find what must be the diameter of a pump's bore, whose length is 36 inches, so that its capacity shall be 2772 ; hence we find that, 2772 -^- = 7/ inches, nearly equal to the area of the pump's bore ; now the area of circles are to each other as the squares of their diame- ters, and the area of a circle whose diameter is 9, is 63-6: therefore, 63-6 : 77 : : 0- : JM, the square root of which will be the diameter of the pump, and will be found = 9-9 inches. With respect to the fly wheel, Horses' power of engine x 2000 Velocity of circumfer. wheel in feet per second- the weight of the fly wheel in cwts. If the diameter of the fly of a 30 horse power engine be 20 feet, and make 18 revolutions per minute, then, 20 X 3-1416 = 62-832 = circumference in feet, and 62-832 X 18 = 1128-97 feet, the space which the circumference moves through in one minute ; hence, 1128-97 =18-81 feet per second; 30 x 2000 60000 18-81- = 353* == 169 CWtS ' r= 8 tons 9 cwts. the weight of the fly. In the working of the valve of a steam engine, an eccentric wheel is often employed, and it becomes necessary to cal- culate the degree of eccentricity necessary to give a certain length of stroke. The eccentric wheel's radius mav bo 260 STEAM ENGINE. easily found; thus, suppose the length of stroke required is 20 inches, and the diameter of the shaft on which the wheel is screwed is 5 inches, and the thickness of metal required to key on the wheel 21 inches. Take the half of the re- quired stroke, that is, 10 inches, as the distance of the cen- tre of the shaft from the centre of required wjieel, and add- ing to this the half thickness of the shaft = 2,1 inches, as likewise the thickness of metal necessary for keying = 21, then 10 + 21 + 21 = 15 inches, ihe radius of the wheel. Now let E be = the radius of the eccentric wheel L = the length of the eccentric rod, and / -= the length of the bar between the other end of this rod and the slide ; and let e = the length of slide; then, E = L _*_? r == /xE / e I x E L x e P / L E Suppose the length of the stroke of the slide e 6 inches, the length of the slide rod / = 5 inches, and the radius of the eccentric = 24 inches = E, then the length of the rod 5 X 24 L = = 20 inches. 6 , The other rules are wrought on the same principle We have before spoken of the governor while treating of central forces and rotation. It remains for us here only to observe, that the governor performs in one minute half as many revolutions as a pendulum, whose length is the perpendicular distance between the plane in which the balls move and the centre of suspension. Thus, if the distance between the point of suspension and the plane in which the balls move be 28 inches : [/ 39-1386 \ .]( ^ ) = I 1 182 vibrations in a second from the nature of the pendulum ; hence, 1-182 - = 0-591, the revolutions of the governor in a se- cond, or 0-591 x 60 = 35-46 in one minute. The piston rod of a steam engine may be made to move up and down in a right line in various ways. The rod may be made to terminate in a rack, the teeth of which act in S1EAM ENGINE 2611 the teeth of an arched head of the .oAg lever, called the working beam : but the most efficacious of all contrivances of this kind, is that of Watt, commonly called the parallel motion This contrivance is founded on geometrical prin- ciples, which it would be inconsistent with the plan of this work to consider ; we shall therefore simply describe the contrivance of this illustrious mechanic. The working beam has an alternating circular motion ound its centre A, and it is clear that the points B ami G ill have a circular motion round the common centre A. et the point B be exactly in the middle, between the centre and end of the beam. Let there be a bar or rod CD, of the same length as AB, capable of moving round the centre C, by means of a pivot. The other end of this rod is" attached by means of a pivot, to the rod DB. Now, by the alternate rising and falling of the beam, the points B and D will move in circular arches, but the middle point P of the connecting rod BD, will move upwards and djwnwards in a vertical straight line, or at least so very neatly so, as the difference cannot be perceived. Now, to this point P, there is attached the end of the pump rod, which will, of course, follow the direction of the impelling point, and move in a straight line. For the purpose of communicating a similar motion to the other piston rod, conceive another rod CP' introduced, of the same length as BD, and its extremities moving likewise on pivots. The oiston rod of the cylinder is attached to the point P', and .this point moves quite in the same way as the point P. The only difference in the motion of these two points will jje, that the point P' will move twice as fast as the point P, or will, in the same time, move twice as far. 262 STEAM ENGINE. The length of the links are made = 4 to 5, the length of the stroke being 1, according to circumstances, the longef link being preferred when practicable. From the length of the links must be determined the position of the radius bar, for the vertical distance between the centres of motion of the working beam and the radius bar must be equal to the length of a link. When the parallel bar is not more than one-half of the working beam's radius, then, Let B = radius of the beam, P = length of parallel bar, S = length of stroke, R = length of radius bar; we have B 2Px(iS)" R B ^B' [iS] 2 ) X2P "* Suppose the length of the beam from the centre = 12 feet, the length of stroke 6, and of parallel bar 5 feet, that is, B = 12, S = 6, and P = 5, then, B 2 P X (S) a = 12 10 X (^6) 3 = 18 = the dividend ; then, B v/(B 3 [|S] a ) x 2 P = 12 v/(12 a [16] 2 ) x 10 = 12 11-62 X 10 = 0-38 X 10 = 3-8 the divisor, wherefore, 18 - + 5 = 9-74 = the length in feet of the radius bar. 3'8 When the parallel bar is more than half the length of the radius of the beam, the rule is, 2P-BX(|S) B (B a [|S] 2 ) x 2P by which rule it will be found that when the length of stroke and radius bar are each 6, and the radius of beam 10 feet, the length of radius bar will be 2-75 feet. Many rules have been given for the quantity of fuel necessary for the production of steam, but they cannot be depended on, so many circumstances must be taken undei consideration the quality of material used for fuel and the mode of constructing the fireplace. It has been found that 3 cwt. of Newcastle coals are equivalent to 4 cwt. of Glasgow co?ls, or 9 cwt. of wood, or 7 cwt. of culm. A chaldron of coals in London contains 36 bushels, and weighs 3136 Ibs., or nearly 1 ton. 8 cwt. . STEAM ENGINE. 263 It would appear, that in the common low-pressure steam engines, the eonsumpt of coal per hour for 1 horse power, is about 16 Ibs., of wood 56 Ibs.,- and of culm 35 Ibs. These statements are given somewhat large, and by proper regulation much less fuel might serve. In the boiler there are certain proportions generally ob- served. The width, depth, and length, are as the numbers 1, 1-1, 2-5. So that if the width be 5 feet, then the depth will be 1-1 x 5 = 5 feet 6 inches ; and the length 5 x 2*5 = 12 ft. 6 in. ; and the whole content of the boiler will be, 5 x 5-5 X 12-5 = 343-75 cubic feet. Now Boulton and Watt allow 25 cubic feet of space in the boiler for each horse power ; and according to this estimate, 343'75 = 13 and a fraction, the number of horses' power of this engine for which this boiler would be fitted. Some, instead of computing the size of boiler in this way, allow 5 square feet of surface of water for each horse's power; but in all cases, it is common to make the boiler of a size fitted for an engine of at least 2 horses' power more than that to which it is applied. There are two ways of loading the safety valve of a boiler ; the one by placing a weight on the top of it, and the other by causing the weight to act on the valve by a lever. When the weight is placed upon the valve ; area of valve X pressure per square inch = whole weight, and also whole weight = pressure per square inch. area of valve Thus, if a weight of 50 Ibs. be placed upon a valve whose area is 10 inches, then the pressure per square inch is = 5 Ibs. pressure per square inch. When the weight acts by a lever, it is placed at one end the fulcrum being at the other, and the valve connected with the lever somewhere between them ; this, then, is a simple case of the lever. Hence, if the length of the lever be 24 inches, the diameter of the valve 3 inches, (its area will be 7,) the distance between the fulcrum and the valve 3 inches, then to give 60 Ibs. pressure per square inch on Ahe valve 60 x 7 = 420 Ibs. the whole pressure on the valve, and 264 STEAM ENGINE, 420 x 3 60 Ibs. will be the weight hung at the 24 3 end of the lever to give the required pressure. To find the action of the weight of the lever divide its whole length by the distance of the valve from the fulcrum, and multiply the quotient by half the weight of the lever. The following rules for calculations connected with the steam engine are extracted from a useful little compendium lately published by Mr. Templeton, of Liverpool. These rules we have inserted here, not so much for their superior accuracy, as from a desire to present our readers with methods by which they may approximate to the true results by means of the sliding rule. It is to be observed that the term gauge point is used to denote the number to be taken on the line stated in the rule. Length of strtfke in ft. and in. Gauge point. Length of stroke in ft. and in. Gauge point. 2 295 6 392 2 6 318 7 41 2 9 322 8 414 3 33 MARINE ENGINES. 3 6 335 3 3 4 343 3 6 31 4 6 355 4 317 5 385 4 6 326 RULE. Set the gauge point upon C to 1 upon D, and against the number of horses' power upon C, is the diame- ter in inches upon D ; or, against the diameter in inches upon D, is the number of horses' power upon C. Ex. 1. What diameter must a cylinder be with a 4 feet stroke, to be equal to 20 horses' power? Set 343 upon C to 1 upon D ; and against 20 upon C is 24'2 inches diameter upon D.. Ex. 2. What number of horses' power will an engine be equal to, when the cylinder's diameter is 19 inches and stroke 3 feet ? 19 3 X "7854 x 7-25 x 192 _ 394672-7328 _ 33000 33000 11*96 or 12 horses' power nearly. i. STEAM ENGINE. 265 The proportion of parts of a high-pressure steam en- gine. The U:ngih of the stroke should, if possible, be twice its diameter. 'The velocity in feet per minute should be 103 times the square root of the length of the stroke in feet. Anil, as 4S-M) is to the velocity thus found, so is the area of the cylinder to the area of the steam passages. The proportions of the parts of an atmospheric en- gine. The length of the cylinder should be twice the dia- meter. The velocity in feet per minute should be ninety- eight times, the square root of the length of 'the stroke in feet. The area of the steam passages will be as 4800 is to the velocity in feet per minute, so is the area of the cylin- der to the area of the steam passage. If the area of the " cylinder in feet be multiplied by half the velocity in feet, and that product by 1"23 added to 1'4 divided by the dia- meter in feet, the result divided by 1480 will give the cubic feet of water required for steam per minute. If the num- ber of times the quantity of water required for injection must be greater than that required for steam, in general it will be about twelve times the quantity, but it had better be a little in defect than excess. The aperture for the injec- tion must be such that the above quantity of water will be injected during the time of the stroke. In order that the injection be sufficiently powerful at first, the head should be about three times the height of the cylinder ; and making the jet apertures square, the area should be the 850th part of the area of the cylinder. The conducting pipe should be about four times the diameter of the jet. The piuportions of the parts of a single-acting low- pressure engine. The length of the cylinder should be twice its diameter. The velocity of the piston in feet per minute should be ninety-eight times the square root of the length of the stroke. The area of the steam passages should be equal* to the area of the cylinder, multiplied by the velo- city of the piston in feet per minute, and divided by 4800. The air pump should he one-eighth of the capacity of the cylinder, or half the diameter and half the length of the strike of the cylinder, and the condenser should be of the same capacity. The quantity of steam will be found bv multiplying the area of the cylinder in fet by half the velocity in feet; with an addition of one-tenth for cooling f ami waste, and this divided by the volume of the steam corresponding to its force in the boiler, gives the quantity 23 266 RAILWAYS. of water required for steam per minute, from whence the proportions of the boiler may be determined.* At the com- mon pressure of two pounds per circular inch on the valve, the divisor will be 1497. The quantity of injection water should be twenty-four times that required for steam, and the diameter of the injection pipe one-thirty-sixth of the diameter of the cylinder. The valves in the air pump bucket should be as large as they can be made, and the discharge and foot valves not less than the same area. Summary of proportions of a double engine, working at full pressure. The length of a cylinder should be twice its diameter ; for a cylinder having this proportion exposes less surface to condensation than any other enclosing the same quantity of steam. The area of the steam passages * should be about one-fifth of the diameter of the cylinder; or their area should be equal to the area of the cylinder, multiplied by the velocity of the piston in feet per minute, and divided by 4800. The diameter of the air pump should be about two-thirds of the diameter of the cylinder, and half the length of stroke ; and the larger the passages through the air bucket and the discharging flap are, the better. The quantity of water for injection should be about 283 times that required for steam, or about 26 cubic inches to each cubic foot of the contents of the stroke of the pis- tog. Watt considered a wine pint, or 28g cubic inches, quite sufficient. There should be 62 times as much water in the boiler as is introduced at one feed. These proportions are taken from Tredgold's valuable treatise on the steam engine. RAILWAYS, STEAMBOATS, &c. IT has been deduced from very extensive experiments or the Liverpool and Manchester railways, that the 'effective power of a locomotive engine is about '3 of the pressure of the steam on the piston, on the calculated power of the engine being 1. In one case, for instance, a cylinder 21 inches diameter was used, the elasticity of steam in the boiler was 30 Ibs. to the square inch, above the pressure * To 459 add the temperature in degrees, and multiply the sum by 76-5. Divide the product by the force of the steam in inches of mer- cury, and the result will be the space in feet the steam of a cub'c foot of water will occupy. RAILWAYS. . -867 ol the atmosphere. The length of the rail, which was in- clined, \vas :H65 feet, and the height 24 feet. The time of drawing 6 loaded wagons, each weighing 9010 Ibs. up the rail, was 570 seconds, during which time the engine made 444 single strokes, each 5 feet long. Now, 21 s x '7854 = 346-36 = the area of the piston in square inches, wherefore, 346'36 x 30 = 10390 Ihs. = the pres- sure of steam upon the piston, whose stroke was 5 feet, and number of strokes in the given time 444; hence 444 x 3 == 2220 feet = the space through which the power 10390 has traversed; therefore, 10390 x 2220 = 23065800 Ibs. = the impelling power of the engine. Now, it was found that the actual weight including resistance moved, wa* '7124415 Ihs.; then, 7124415 which will give the effect about 30-9 per 230uobOO cent., but the foregoing number may be taken as a safe me- dium, that is, 30 per cent or -3. The amount of retardation, arising from steam carriages moving on railways, has been estimated thus ; Loaded carriages weighing altogether 8522 Ibs. the fric- tion amounted to 50 Ibs., or the ^-$ part of the weight. In empty carriages weighing 2586 Ibs., the friction amounted to 10 Ibs., or the ^TS P art f tne weight; and the friction may be regarded as a constant retarding force. Wrought iron rails seem from a multitude of experiments to be much better than those of cast-iron, as they are more durable and cause less friction. The Rocket was tried, weighing 4 tons and 5 cwt., to it there was attached a tender with water and coals, weighing 3 tons, 2 cwt. quar. 2 Ibs. ; and two carriages loaded with stones, weighing 9 tons, 10 cwt. 3 qr. 26 Ibs., making in all .17 tons. At full speed she moved at the rate of 30 miles, in 2 hours, 6 minutes, 9 seconds, or 14| per hour at the end of stage, about 6 miles ; and the greatest velocity was 29 1 miles per hour. The quantity of water used 92'6 cubic feet, and it required 11/j Ibs. of coke for each cubic foot of steam. In the Rocket the boiler is cylindrical, with flat ends 6 feet long, and 3 feet 4 inches in diameter. To one end of the boiler there is attached a square box as a furnace, 3 feet Jong by 2 feet broad, and about 3 feet deep at the bottom of this box five bars are placed, and the box is entirely surrounded with a casting, except at the bottom and the "8 RAILWAYS. side next the boiler. Betwixt the casting and the box there is left a space of about 3 inches, which is kept con- stantly filled with water. The upper half of the boiler is used .as a reservoir for steam; the under half being kept filled with water, and through this part copper tubes reach from one end to the other of the boiler, being open to the fire box at one end, to the chimney at the other ; these tubes are 25 in number, each being 3 inches in diameter. The cylinders were each 8 inches in diameter, and one was at each side of the boiler; the piston had a stroke of 16^ inches. The diameter of the large wheels was 4 feet 85 inches. The area of the surface of water, exposed to the radiant heat of the fire, was 20 square feet, being that sur rounding the fire box or furnace ; and the surface exposed to the heated air or flame from the furnace, or what may be called communicative heat, is 117'8 square feet. The average velocity of the Rocket may be stated at 14 miles per hour, and during one hour she evaporates 18'24 cubic feet of steam, with a consumpt of about 17'7 Ibs. of coke for each cubic foot of water. An empirical rule has been given for the ascertaining of the quantity of fuel necessary for steam carriages, which may be useful. The weight of the load X 51 '55 -f weight of carriages 898 the quantity of coals required to carry one mile, but a near approximation to the truth may be to allow 2 Ibs. for every ton for one mile. Iron railroads are of two descriptions. The flat rail, or tram road, consists of cast iron plates about 3 feet long, 4 inches broad, and 5 an inch or 1 inch thick, with a flaunch, or turned up edge, on the inside, to guide the wheels of the carriage. The plates rest at each nd on Ptone sleepers of 3 or 4 cwt. sunk into the earth, and they are joined to each other so as to form a continuous horizon- tal pathway. They are, of course, double; and the distance between the opposite rails is from 3 to 4| feet, according to the breadth of the carriage or wagon to be employed The edge rail, which is found to be superior to the tram rail, is made either of wrought or cast iron ; if the latter b* 1 used, the rails are about 3 feet long, 3 or 4 inches broad, and from 1 to 2 inches thick, being joined at the ends by cast metal sockets attached to the sleepers. The upper edge of the rail is generally made with a convex surface RAILWAYS. 269 to which the wheel of the carriage is attached by a groove made somewhat wider. When wrought iron is used, which is in many respects preferable, the bars are made of a smaller size, of a wedge shape, and from 12 to 18 feet long; but they are supported by sleepers, at the distance of every 3 feet. In the Liverpool railroad the bars are 15 feet long, and weigh 35 Ibs. per lineal yard. The wagons in common use run upon 4 wheels of from 2 to 3 feet in diameter. Railroads are either made double, 1 for going and 1 for returning; or they are made with sidings^ where the carriages may pass each other. See M'Cullocli's Diet. Table showing the effects nf a force of traction of 100 pounds, ai different velocities, on canals, railroads, and turnpike roads.* Velocity of motion. Load moved by a power of 100 ll. Miln per hour. Feet per second. On a Canal. On a level Railway. On a level Turnpike Road. Total mass moved. UKful ef- fect. Total man moveJ . L'Kfal ef- fect. Total man ! Dseful ef- moved. I feet. 2 3 3-66 55,500 39,400 4-40 38,542 27,361 Ibt. 14,400 14,400 10,800 10,800 Us. i Hi. 1,800.1,350 1,800 1,350 3d 5-13 28,316 20,100 14,400 10,800 1,800 1,350 4 5-86 21,680 15,390 14,400 10,800 1,800 1,350 5 7-33 13,875 9,850 14,400 10,800 1,800 1,350 6 8-80 9,635 6,840 14,400 10,800 1,800 1,350 7 10-26 7,080 5,026 14,400 10,800 1,800 1,350 8 11-73 5,420 3,848 14,400 10,800 1,800 1,350 9 13-20 4,282 3,040 14,400 10,800 1,800 1,350 10 14-66! 3,468 2.462 14,400 10,800 1,800 1,350 13-5 19-9 1,900 1,359 14,400 10,800 1,800,1,350 The subject of steam vessels has been investigated by different engineers, on mathematical principles, but the calculations which their rules direct are by far too intricate for a work of this nature. We will, however, insert a state- ment of the proportions, &c.. of several steamboats already made, which will doubtless be acceptable to the practical man, and those who wish to investigate the theory will find ' ample material in the work of Tredgold. * The force of traction on a canal varies a< the square of the velocity but the mechanical power necessary to move the boat is usually reckoned Ao increase as the cube of the velocity. On a railroad or turnpike, the force of traction is constant; but the mechanical power necessary to move the carriage, increases as the velocity. 23* 870 STEAMBOATS. cc GO P=H O w -3 d . . to S f | e< "" . CO & M co d 3 U! 2 ksl! 1 t- 1 CD t *" CO ^ *** m K3 O) "" a'to N o (M IM CO CO P-l P, 00 CO 00 C . "~ S _c a ! d 8 H d, 8 to "" Cft a ^ > 1 "j o 00 **" d C-J ^ ** co CO ^ Q O CO " (M CD O CJ CO CO CO PH 1 &, CD (M 00 o CO t- ^ as QJ d, d ""* C "* e m O-i w S tc^ o "" (^ ~ c C o ^ ^j ^* . sr I K d 00 ^d CO o o J3 ** CD ff OO O ^ o oo o c* 1- 1> C* 00 . 4, C - a> no A t- m C* 00 1-1 O5 **" o ' U CO Ti< S-J - Q (D 05 w .-. 1-1 1^ * 1-1 N ^ 1C N h-1 (S d 0! ai "2 d 1 ** *j ^ M O 1 11 (j g < & ,000 S *** * a m o S3 10 - 2 CO 00 rj< Si 00 CD .2 d 01 d 15 d OJ a 4) 5 tfi J3 CO S , fl o c o A co 4-4 1 1 * ' o o c < ** m > w N co O O o o * CO g GD {-< "* CO <-< c* e* m co t* Zi w me of the vessel . . . s . . S : : s "3 ! -o a 5 te of construction . . culated power ofen- nes at the best velo- ;y and full pressure 8 IM O r X 2 engines 05 O "^ r - > s e LX 5 **" 7 C X u 1 o S o PH | 3S 8 f C """ d X "*" X 'c oo ft. VM o X to u 'SJD j; | * Passengers N 00 ft. s = c . ft. V C B. c " X "^ c X _c; Z x t! O - r - . 2 e c i C 4 ? rt - T e CJ ci x - _ ' t^ 1 i s ft p* 31 SJ T? -" N - bo ft. O CC * c; _ 5 c: 5 ~ X CC f a "^ 5 4 ,__ c. :5 '5r It, 1 ." 4 |_ r = v S f- "3 ^ ^ ~>. ~z k = "^ ^T^ ~^ * * ^5 ^ *" ^; it -5 c 1 ^ -= -r r ~ c. > "~ i --: C z .-S 2 ~ a t2 ~ : v: d 272 STEAMBOATS. r .S-S g Cn c* 00 . s.2' A s p CO _ -5 c .1 . .2 .0 d *s * 00^ 3 o CO ~ O "tc ^i jJ * e* 00 J CO ,-, _, 05 ^H CO w co co ""* *~ S .2 A Uj A i 1 4> -H < ^ *: d 11 '& a a j o o o s '** '"^ (7* cs 55 CO * CO C^ N 00 ^* ^ -< N 1-1 w >* *< 11 " H .sl- s A 1 8 1 H id !| 1 1 o 1 1 0> -* S CO p CO 0* J s'^ 1 1 I I II ~ O s 8 V o 00 (N t- C5 -H X (M A g d 03 U3 ; p QJ 1 o X! .2 *J -^ 's ~ ^ be CO j; o o c S .-^ 1C O CO ^ O ^ " "5 o *** 5 u - C 'hnJd B o J -a o j- -5 .fi ,. Q- tD ^ GH c3 ? ^ rt ^ f, , ^ co S o a "13 M ^-r ^ ^ f 1 g ? ^ ^ JJ? ^ 'S "5 t . .0 1 >, a hjpQi^caHi^^ M o s ^ o o o ^e QO tb '3 , ANIMAL STRENGTH. 273 The rule for determining the tonnage is according to law. but by no means according to correct principles. It is as follows : Take the length = L from the back of the main stern ?ist to the fore part of the main stem< beneath the bow- sprit, and subtract from it the length of the engine room = E, and from the remainder subtract three-fifths of B = the breadth of the vessel taken from outside to outside of the planks at the widest part of the vessel, whether it be above or below the wales, and divide this last remainder by 188 ; the quotient multiplied by the square of B will give the register tonnage, or, Wherefore the length being 162 feet, the length of engine -oom 47, and the breadth of the vessel 32, then, tonnage. ANIMAL STRENGTH. % THERE is a certain load which an animal can just bear but cannot move with it, and there is a certain velocity with which an animal can move but cannot carry any load. In these two circumstances it is clear, that the exertion of the animal can be of no avail as a mover of machinery. These are, as it were, the extremes of the animal's exertion, where its effect is nothing ; but between these two extremes, there must be weights and velocities with which the animal can move, and be more or less efficient. If one man travel at the rate of three miles an hour, and jarry a load of 56 Ibs., and another move at the rate of 4 miles an hour and carry a load of 42 Ibs., the speed of the first is 3, and the load 56, the useful effect may there- fore be estimated as the momentum = 168. The other Carries only 42 Ibs., but travels at the rate of 4 miles an hyur ; therefore, in the same way, his useful effect will be nyur ; tnei r x 42 = X 42 = 168, the same as before: hence the effect of 274 ANIMAL STRENGTH. these twc men are the same. It will not be difficult to show, that in the same time they perform the same quantity of work. For the first will in six hours carry 56 Ibs. 3x6 = 18 miles, as he travels at the rate of 3 miles an hour; and if he be supposed to carry a different load, hut of the 3ame weight every rnile, he will in the six hours have car- ried altogether 18 X 56 = 1008 Ibs. ; but the other carries in the same way, 4 times 42 Ibs. every hour, that is 168 Ibs. in one hour therefore in 6 hours he will have carried 168 x 6 = 1008 Ibs., the same as the other. It will now be seen what is meant by the phrase useful effect, and from what has been observed above, we will be led to conclude, that when the load is the greatest which the animal can possibly bear ; the useful effect is nothing, because the animal cannot move ; and when the animal moves with its greatest possible speed, the useful effect will also be nothing, for then the animal can carry no load ; and it becomes a very useful problem to determine where between these two limits, the load and speed are so related that the useful effect of the animal will be the greatest. By investigation it has been found that the maximum effect of an animal will be when it moves with 5 of its greatest speed, and carries ^ths of the greatest load it can bear. Thus, if the greatest speed at which a man could travel or run, without a load, be 6 miles per hour ; and if the greatest load which he can "bear, without moving, be 2 cwt., then this reduced to Ibs. is 280 Ibs.. hence, - = 124-4 Ibs. = the load, and = 2 miles, the y 3 speed with which a man will produce the greatest useful effect. Sir John Leslie gives a formula for a horse's power, in traction, in which he denotes the velocity in miles per hour, I (12 - V) 2 by which it will be found that if a horse begins this pull with a force = 144 Ibs., he would draw 100 at the rate of 2 miles, 64 at 4, and 36 at 6 ; the greatest effect being at 4 miles per hour. The French employ a measure of animal action which they denominate a Dynamical unit, which is a cubic metre of water raised to the height of a metre. There are so many causes operating to produce variations in animated beings even of the same kind, that it is difficult, if not impossible, 10 form a correct estimate of the amount FRICTION. 275 of any one particular class, or the comparative strength of different classes, hence we find great differences in the results of different experimenters. Gregory has estimated the average force of a man at rest to he 70 Ibs., and his utmost walking velocity, when un- loaded, to be 6 feet per second ; and that a man will pro- duce the greatest mechanical effect in drawing, when the weight was 31^ '.os., with a velocity of 2 feet per second. But this is not the most advantageous way of applying the strength of men, although it has been found to be the bes\, war of employing the strength of horses. Robertson Bu- chanan states, that the mechanical effects of men in work- ing a pump, in turning a winch, in ringing a bell, and rowing a boat, are as the numbers 100, 107, 227, and 248. According to Hatchette, of a man working at the cord of a pulley to raise the ram of a pile engine = 50 dynamical units. A man drawing water from a well by means of a cord 71 ; a man working at a capstan 116. The dynami- cal unit being, as stated before, equivalent in English mea- sure to 2208 Ibs., or 4 hogsheads of w.iter raised to the height of 3-281 feet in a minute; these things being con- sidered, the above results will give the average strength of men per day. We meet with similar difficulties in estimating the strength of horses. According to Desagulicrs and Smea- ton, 1 horse equal to 5 men. According to Bossut, 1 horse equal to 7 men. Schulze makes it 14 men; and Bossut states, that I ass is equivalent to 2 men. It is also stated by Amontons, that 2 horses yoked in a plough exert a power of 150 Ibs. See the section on the Steam Engine. FRICTION. WE have considered the effects of the first movers of machinery, and we must now direct our attention to the subject of Friction, which, as we have frequently noticed, tends to diminish these effects. On this subject it is not .OIK- intention to dwell long, as all the researches that have been hitherto made in this branch of mechanical science, a/e not of such a nature as to furnish means of deducing satisfactory laws. The resistance arising from one surface 276 FRICTION. rubbing against another is denominated friction ; and it is the only force in nature which is perfectly inert its ten- dency always being to destroy motion. Friction may thus be viewed as an obstruction to the power of man in the construction of machinery ; but, like all the other forces in nature, it may, when properly understood, be turned to his advantage, for friction*is the chief cause of the stability of buildings or machinery, and without it animals could not exert their strength. The friction of planed woods and polished metals, with- out grease, 4m one another, is about one-fourth of the pres- sure. The friction does not increase on the increase of the rub- bing surfaces. The friction of metals is nearly constant. The friction of woods seems to increase after they are some time in action. The friction of a cylinder rolling down a plane, is in- versely as the diameter of the cylinder. The friction of wheels is as the diameter of the axle di- rectly, and as the diameter of the wheel inversely. The following hints may be of use for the purpose of diminish- ing friction. The gudgeons of pivots and wheels should be made of polished iron ; and the bushes or collars in which they move should be made of polished brass. In small and delicate machines, the pivots or knife edges should rest on garnet. Oily substances diminish friction swine's grease and tallow should be used for wood, but oil for metal. Black lead powder has been used with effect for wooden gudgeons. The ropes of pulleys should be rubbed with tallow. As to the friction of the mechanic powers. The simple lever has no such resistance, unless the place of the ful- crum be moved during the operation. In the wheel and axle the friction on the axis is nearly as the weight, the diameter of the axis, and the angular velocity it is, how- ever, very small. When the sheaves rub against the block? the friction of the pulley is very great. In most, if not in all screws, the friction of the screw is equal to the pres- sure the square threaded screw is the best. In the inclined plane, the friction of a rolling body is far less than that of a sliding one. FRICTION. 277 To estimate the amount of the friction of a carriage upon a railway, we have, P X T P = friction, in which rule P signifies the power that will keep the wagon on the plane, independent of friction, T the time of descent without friction, both of which are to he deter- mined by the laws of the inclined plane given before : and t is the time of actual descent of the wagon or carriage. There is a loaded carriage on a railroad 120 feet in length, having an inclination of one foot to the hundred. The carriage, together with its load, weighs 4500 Ibs. Now, the height of the plane may be found by the princi- ples of geometry, from the proportion of similar triangles. IOC : 120 : : 1 : i'2 == the height of the plane ; and by the laws of falling bodies, and the properties of the inclined plane, J4? 1 X 120 = -2731 X 120 = 32-772 = the time ^( 16 in seconds in which the carriage would descend the plane without friction and by the properties of the inclined plane, 100 : 1 : : 4500 : 45 = the force that sustains the carriage, without friction, from rolling down the plane : wherefore, by the rule, 45 ; 20-421 = the friction in pounds", 60 which retards the carriage in rolling down the railway. OF MACHINES IN GENERAL, THEIR REGULATION AND COMPARATIVE EFFECTS. A. MACHINE, howsoever complicated it may be, is nothing else than an organ or instrument placed between the work- men, or source of force or power, whatever it may be, and the work to be done. Machines are used chiefly for three reasons. 1. To accommodate the direction of the moving force to that of the resistance which is to be overcome. 2, To render a power, which has a fixed and certain velocity, effective in performing work with a different velocity. 3, To make a moving power, with a certain intensity, capable of balancing or overcoming a resistance of a greater in- tensity. These objects may be accomplished in different ways, either by using machines which have a motion round some fixed point, as the three first mechanic powers ; or by those which furnish, to the resistance to be moved, a solid path along which it may be impelled, as is the case in the last three mechanic powers : hence some authors have reduced the simple machines to two the lever and inclined plane. Simplicity in the construction of machines cannot be too warmly recommended to the young engineer; for com- plexity increases the friction and expense, and endangers the chance of success from the derangement of the parts. In consequence of friction, it is well known, that no machine can overcome a resistance without an expense of the power of the first mover, and as the more complicated the machine is, the greater will the friction be ; so also will the machine be less powerful. If two machines be con- structed, the one simple and the other complex, and be such, that the velocity of the impelled point is to the velocity of the working point in the same proportion in both ; then will the simple machine be the most powerful. The methods of communicating motion from one point to another are infinitely diversified ; and we, in the last 278 MACHINERY. 219 caapter, gave an account of the best of these which have hitherto been invented. We confine ourselves in the mean time to a few general remarks on the construction of machinery. When heavy stampers are to be raised in order to drop on matter to be pounded, the wipers by which they are raised should be of such a form, that the stampers may be r.ised by a uniform pressure, or with a motion as nearly as p.ssible uniform. If this is not the case, and the wiper is merely a pin sticking out of the axis, the stamper will be "arced into motion at once, which will occasion violent jolts n the machine, together with great strains on its moving parts and points of support. But if gradually lifted, no inequality will be felt at the impelled point of the machine. The judicious engineer will therefore avoid, as much as possible, all sudden changes of motion, especially in any ponderous part of a machine. When several stampers, pistons, or other reciprocal i/iovers are to be raised and depressed, common sense teaches us to distribute their times of action in a uniform n:anner, so that the machine may be always equally loaded with work. When this is done, and the observations in the foregoing paragraph attended to, the machine may be made to move almost as smoothly as if there were no re- ciprocations in it. Nothing shows the ingenuity or skill of the contrives more than the simple yet effectual con- trivances for obviating those difficulties which are unavoid- able, from the .nature of the work to be done by the machine, or of the power applied. There is also much ingenuity required in the management of the moving power, when it is such as does not answer the kind of mo- tion required ; for instance, ,n employing a power which necessarily reciprocates to produce a motion which shall be uniform, as in the employment of a steam engine to drive a cotton mill. The necessky of reciprocation of the first mover causes a waste of much power. The impelling power is wasted first in imparting, and then in destroying a vast quantity of motion in the working beam. The en- gineer will see the necessity of erecting the mover in a f separate building from the machinery moved, which pre- vents the great shaking and speedy destruction of the /buildings. The gudgeons of a water wheel should ne\ er rest on tho 28C MACHINERY building, but should be placed on a separate erection ; and if this is not practicable, blocks of oak should be placed below them, which tend to soften all tremors, like* the springs of a carriage. It will often conduce to the equality of motion of ma- chinery, to make the resistance unequal, to accommodate the inequalities of the moving power. There are some beautiful specimens of this kind in the mechanism of the human body. It is always desirable, that the motion of a machine should be regular, when this can be effected ; and we now pro-* seed to state the various methods that have heretofore been employed for producing regularity in the motion of the machine, both as regards the reception and distribution of power. Even supposing that the first mover is perfectly constant and equable in its action, the machine may not be regular in its movement, from the irregularity of the resistance to be overcome. But still, if both the power and the resist- ance were perfectly regular, the machine would not be perfectly uniform in its motion ; for there are particular positions in which the moving parts of a machine are more efficacious than in others, as in the crank for instance : hence the energy of the first mover will be unequally trans- mitted, and irregularity in the motion of the machine will consequently follow. The motion of some machines bears a constant tendency to accelerate, others to retard ; and others alternately to accelerate and retard ; and perhaps in no case whatever can the motion of a machine be said to be perfectly uniform. But of this we will speak more at large when we come to treat of the maximum effect of machines. We intend to confine our attention chiefly to the regula- tors of machinery employed in the steam engine, making occasional remarks on others as we go along. For the purpose of regulating the moving power, the conical pendulum or governor is commonly employed. The nature of this beautiful contrivance has been described under central forces, and alluded to in our remarks on the steam engine. The ring on the shaft acts upon a lever of the first kind, whose other end opens or shuts a valve, which is fixed in the pipe that admits the steam from the boiler to the cylinder ; and according to the degree of opening or MACHINERY. 281 shutting of tliie valve, and consequently the divergence or convergence of the halls, or the velocity of the shaft, will be the quantity of steam admitted to the cylinder. The governor is frequently applied to the water wheel, and acts in a similar way by a board or valve in the shuttle, which delivers the water to the wheel. So likewise in the wind- mill, it is employed to furl or unfurl more or less sail. Sometimes the governor is found inadequate to the regu- lation of the machine, and another contrivance of great power and simplicity is introduced. The machine is made to work a pump, which tends continually to fill a cistern with water. From this cistern there proceeds an eduction pipe, leading to the reservoir, from which the water is drawn by the pump. Tliis simple contrivance is so regu- lated, that when the machine goes with its proper velocity, the pump throws just as much water into the cistern as the ejection pipe draws from it; consequently, the water in the cistern remains at the same level. But if the machine goes too fast, then the pump will throw in more water than is let out by the ejection pipe, wherefore the level of the water will rise in the cistern. If the machine goes too slow, the level of the water will in like manner fall. Now, on the surface of the water in the cistern, there is a float which rises or falls with the surface of the water ; and is thus made to answer the same purpose as the ring of the governor. It may be observed, that the delicacy of this kind of regulator will depend, in a great measure, upon the smallness of the surface of the water which supports the float ; for then a small difference between the supply and discharge, will cause a greater difference in the elevation or depression of the surface, than if the surface were large. To procure a constant supply of steam in the steam en- gfne, it is necessary that the water in the boiler be always at the same level. To effect this purpose, there is a lever fixed on a support, on the top of the boiler, to one end of which lever there is attached a slender rod, which descends into the boiler, and is terminated by a float, which rests on the surface of the water in the boiler. To the other end of the lever, there is attached another rod, to the end of which is affixed a valve, opening and shutting the orifice i of a pipe which leads into the boiler. The top of the pipe, /where the valve is placed, opens into a cistern of water, is supplied by a pump driven by the engine itself. 24* 282 MACIIINEUY. When the water in the boiler falls below its common level in consequence of the formation of steam, the float falls with it, and consequently depresses that side of the lever to which the float rod is attached ; the other arm rises and opens the valve at the top of the pipe, which leads from the cistern into the boiler, and thus admits water until the float rises to the proper height, and then the valve is closed. In this beautiful contrivance, the water is not supplied to the boiler in jolts, but the float and valve continuing in a state of constant and quick vibration, the supply is rendered quite constant. There is a very ingenious contrivance called the Tacho- meter, from its use as a measure of small variations in velocity, which is often employed in the steam engine and other machinery. The simplicity of this contrivance will render its action easily understood. If a cup with any fluid, as. mercury, be placed on a spindle, so that the brim of the cup shall revolve horizontally round its centre, then the mercury in the cup will assume a concave form, that is, the mercury will rise on the sides of the cup, and be de- pressed in the middle ; and the more rapid the motion of the cup is, the more will the surface of the mercury differ from a plane. Now, if the mouth of this cup be closed, and a tube inserted in it, terminated in the cup by a ball-shaped end, and half filled with some coloured fluid, as spirits of wine and dragon's blood ; then it is clear, that the more the surface of the mercury is depressed, the more the fluid in the tube will fall, and vice versa : consequently, the rapidity or slowness of the motion of the cup, will be indi- cated by the height of the coloured fluid in the tube ; and thus it becomes a measure of small variations in velocity. In the steam engine, we also find an apparatus for regu- lating the strength of the fire of the boiler, which apparatus is called the self-acting damper. There is a tube inserted into the boiler, reaching nearly to the bottom, which tube is open at both ends. Now, from the principles of Pneuma- tics, it is plain, that the greater the pressure of the steam in the boiler is, the water will be pressed to the greater height in this tube. The water in the tube supports a weight, to which there is attached a chain going over two wheels ; and to the other end of the chain is attached a plate r , which slides ovei ihe mouth of the flue which leads into the fire. These thii.gs are so formed, that the rising of the weight MACHINERY. 283 in the tube will cause more or less of the flue to he covered by the plate ; and thus increase or diminish the quantity of air which feeds the fire. Now, if there is too much steam produced, there will be a greater pressure on the surface of the water in the boiler, and it will be forced up the tube the weight in the tube will be raised, and consequently the plate at the other end of the chain will fall, and cover more of the mouth of the flue, and thus diminish the quantity of air which feeds the fire ; and there will consequently be generated in the boiler a less quantity of steam. We come now to speak of the nature and use of the fly wheel. A fly in mechanics may be defined to be a heavy wheel or cylinder, which moves rapidly upon its axis, and is applied to a machine for the purpose of regulating its motion. We have already stated that there are many circum- stances which tend to render the motion of a machine ir- regular variation in the energy of the first mover, whether it be water, wind, steam, or animal strength variation in the resistance or work to be done and variations in the efficacy of the machine itself, arising from the nature of its construction, whereby it is of necessity more effective in one position than in another. We have already seen how many of these irregularities are compensated, and we are now come to speak of the fly, which is the simplest and most effective of them all. The principle on which the fly acts is that of inertia, one of the most important of the first principles of mechanical science. At any one given time, a body must be in one or other of these two states rest or motion. And let any body be in one or other of these two state*, it has no power within itself to change it, if it be at rest, it has no power to put itself in motion and if in motion, it has no power in itself either to increase, diminish, or destroy that motion. From a knowledge of this fact, and from what was stated before on the momentum, or moving force of a body, that it is the quantity of matter multiplied by the velocity of the moving body the nature of the operation of the fly will be easily understood. As the fly wheel, to do its office effectually, must have a considerable velocity, it is clear that its rim, which has a considerable weight, must also have a considerable momen- turn, and consequently a considerable power to overcome . snv tendency either to increase or retard its motion. 284 MACHINERY. To apply these observations to actual cases, let us sup- pose th'at a single horse drives a gin. .When the gin has been set in motion, the animal cannot exert a uniform strength- there will be occasional increases and relaxations in the velocity of the gin ; but suppose a fly wheel to be added, then, whenever the animal slackened its exertions, the machine would have a tendency to move slower, but the momentum which the fly had acquired, would overcome this tendency to retardation, and -continue the motion of the machine at the same rate as before, until the animal had recovered iiself so as to exert the same strength as before. So, likewise, if the animal exerted an extraordinary pull, the inertia of the wheel would oppose a resistance which would check the tendency to increase in the velocity of the gin. In this way the fly wheel regulates the motion of the gin, whether the animal takes occasional rests, or makes occasional extraordinary exertions. It is evident that the fly would operate in the same way, if the first mover were steam, water, or wind, and that the other regulators which we have described, are merely assistants to the fly wheel. Variations in the resistance, or work to be performed, are also compensated by the fly wheel. For instance, in a small thrashing mill without a fly. When the machine is not regularly fed with the corn, there will be an occasional resistance, which will have a sensible effect on the whole train of the machinery, even the water wheel itself; which irregularity, may, however, be avoided by the introduction of a fly, as its inertia will procure equality of motion : but it may be observed, that when the machine is large, there will be less necessity for a fly, as the inertia of the machine itself will then effect the same purposes. It was before stated, that even supposing the first mover and resistance to be perfectly uniform, the machine itself is liable to variations in energy at different positions. It was seen, for instance, that a crank is more effective in one position than another ; but the momentum communicated to the fly, when the crank is in the most effective position, will carry the crank past its least effective position. There are many cases, however, where there are irregularities of motion proceeding from the nature of the machinery, which could be compensated better than with a fly. Thus, if a bucket is to be drawn from the bottom of a coal pit, which is 60 fathoms in depth: the weight of bucket beiug 14 MACHINERY. 285 cwt., and the chain by which it is coiled up round the cylin tier weighing 8 Ibs. to every fathom, it is plain, that when the bucket is at the bottom, not only the weight of the bucket, but also the weight of the chain, will require to be overcome in the raising of the bucket. Now the weight of the chain is 60 + 8 = 480 Ibs., and the amount of the weight of the bucket is 14 cwt. or 1568 Ibs. ; hence 1 568 + 480 = 2048 Ibs. ; but the weight of the chain will always be getting less as it is coiled round the cylinder, until the bucket comes to the cylinder, when the chain will be all coiled, and there will remain only the weight of the bucket. Now, the use of a fly may be advantageously dispensed with, if the barrel on which the chain is coiled is formed like a cone ; the diameter of the barrel thus increasing with the uniform diminution of the weight. The effect of the fly wheel in accumulating force, has led some to suppose that there is, positively, a creation of force in the fly ; but this is a mistake, for it is only, as it were, a magazine of power, where there is no force but what has been delivered to it. The great use of the fly wheel is thus to deliver out at proper intervals, that force which has been previously communicated to it ; and although there is ab- solutely a small loss of power by the use of the fly, yet this is more than compensated by its utility as a regulator. The motion of machines may, as stated before, be re- duced to three kinds. That which is gradually accelerated, which generally takes place at the commencement of a machine's action: that which is entirely uniform: that which is alternately accelerated and retarded. The nearer that the motion of a machine approaches to uniformity, the greater will he the quantity of work done. In order that the few remarks, which we intend to make on the effect of machines, may be clearly understood, we desire the reader to attend to the following definitions. The impelled point of any machine, is that point at which the force which moves the machine, may be considered as applied as the piston of a steam engine, or the float board of a water wheel. The working point, on the contrary, is that point where the resistance may be supposed to act. The velocity of the moving power is the same as the ve- locity of the impelled point, the velocity of the resistance is the same as the velocity of the working point. 886 MACHINERY. The performance or effect of a machine is measured by the resistance or work performed, (calculated by weight,) multiplied by its velocity, which is, in other words, the mo- mentum of the working point. The momentum of impulse, on the other hand, is measured by the energy of the first mover, (also estimated by weight,) multiplied by the ve- locity of the impelled point. These definitions being understood, we proceed to a simple statement of principles. When any power is made to act in opposition to a resist- ance, by means either of a simple or compound machine ; which machine will be in a state of rest, when the velocity of the power is to that of the resistance as the weight of the resistance is to that of the power. In this state of things the machine can do no work, because it has no motion ; but if the power is increased, so as to overcome the resistance, the machine will have an accelerated motion so long as the power exceeds the resistance. If the power should diminish, the machine would accelerate less and less, until its motion became uniform. The same effect would ne- cessarily follow, if the resistance increased, a circumstance which may arise from various causes. From the resistance of the air, which increases with an increase of velocity ; and also from friction, which often increases with the in- crease of velocity. Hence we find, that machines have commonly a tendency to become uniform in their motion. We have seen before, while treating of the water wheel, that the velocity of the floats of the undershot wheel, must be less than the velocity of the stream. For, when the float board is at rest, the water will impinge on it with the greatest possible effect ; but so soon as the float begins to move, then it leaves the water, as it were, and does not re- ceive the whole impetus of the stream ; and if the velocity of the float were equal to that of the stream, it is clear that the water would have no effect upon it at all ; and, as was stated before, there is a certain relation between the velocity of the wheel and that of the stream, at which the effect will be a maximum. This is not confined to the water wheel, but is common to all machines, as we have seen illustrated in the steam engine. We have seen before, that the maximum effect of an animal was, when its velocity was one-third of its creates possible speed, and the load which it bore, or the resistance MACHINERY. '287 which it overcame, was equal to four-ninths of its greatest possible load. The following tables (A and B) constructed from the re- sults of Dr. Kobison, will be useful to the mechanic. Table A contains the least proportions between the velo- cities of the impelled and working points of a machine ; or between the levers by which the power and resistance act. The use of this table is very simple, for suppose we wished to raise 3 cubic feet of water per second, by means of a water wheel, whose radius was 8 feet, (= the length of the lever by which the power acts,) and the power which moves the wheel being 6 cubic feet of water per second. Employ this rule : Power, : x 10 = a number, Resistance, which look for in column M, and against it in column N, will be found a number which, when multiplied by the length of lever at which the power acts, will give the lengtK of lever at which the resistance should act. Wherefore, in the above case, / X 10 = 20, the number corresponding to which is 0-732051, hence 0-732051 X 8 = 5-856408 = the radius of the axle at which the resistance or work to be done acts. This table will be found very useful in the construction of machines ; but they are frequently already constructed, and it becomes then necessary for us to regulate the power and resistance in order to produce a maximum effect, with- out making -\ny alteration in the machine. For this pur- pose we employ table B, in order to show the use of which *re give the following rule and example : Length of lever of resistance, T-J = a number, which, when Length of lever of power, found in column O, will stand against a number in column P: such, when multiplied by the energy of power, will give the proper energy of resistance. Thus, if a man exerts a constant force of 56 Ibs. on the handle of a capstan, whose leverage is 4 feet, and the barrel is one foot in radius, then we have. =- a number, which will be found in column O, cor 4 4 288 MACHINERY. Desponding to which will be found, in column P, the num- ber 1*8885 ; wherefore, by the rule, 1-8885 x 56 = 105-756 = the resistance which the man in these circumstances, can overcome with the greatest ad- vantage, or with the maximum mechanical effect. TABLE A. TABLE B. M N M N 1 0-048809 20 0-732051 2 0-095445 21 0-760682 3 0-140175 - 22 0-788854 4 0-183216 23 0-816590 5 0-224745 24 0-843900 6 0-264911 25 0-870800 7 0-303841 26 0-897300 8 0-341641 27 0-923500 9 0-378405 28 0-949400 10 0-414211 29 . 0-974800 11 0-449138 30 1-000000 12 0-483240 40 1-236200 13 0-516575 50 1-449500 14 0-549193 60 1-645600 15 0-581139 70 1-828400 16 0-612451 80 2-200000 17 0-643168 90 2-162300 18 0-673320 100 2-.3 16600 19 0-702938 o P P * 1-8885 7 0-03731 1 3 1-3928 8 0-03125 3 0-8986 9 0-02669 1 0-4142 10 0-02317 2 0-1830 11 0-02037 3 0-1111 12 0-01809 4 0-0772 13 0-01622 5 0-0587 14 0-01466 6 0-0457 15 0-01333 MACHINERY. 28S Oi Oi S O Hi to 4* Ui ~l OO O O O O * GO Oi Ci -1 -J .toWbaOOtOCDGO^J cb i> to ob ti> A cb -J cii co cb ti ob 5' Ol w w' tO __ 1 ? s-8 gas " '-; .3 n 1 3 s.* 3 "" Hi oooo3oSowowowoo!o&oSogo5;Sw r. Is" 5sl2SSii32S^^^^3SSSfe^^- i.}': tOK>a>*.0040-J-i-JtOtOCOOJ-J COOWOOOO*.^ il 5'? a- 0><3>05^' J 0.*^^^WCOtO- 5-9160 3-271 83 9-1104 4-362 131 11-4455 5-078 96 6- 3-301 84 9-1651 4-379 132 11-4891 5-091 37 6-0827 3-332 85 9-2195 4-396 133 11-5325 5-104 38 6-1644 3-361 86 9-2736 4-414 134 11-5758 5-117 39 G-2449 3-391 9-3-273 4-431 135 11-6189 5-129 40 6-3245 8419 9-3808 4-447 136 11-6019 5-142 41 6-4031 3-448 89 9-4339 4-464 137 11-7046 5-155 42 6-4807 3-476 | 90 9-4868 4-481 138i 11-7473:5-167 43 6-5574 44 (;<;:<:.: 3-503 : 91 1 9-5393 ; 4-497 3530 92 9-5916,4-514 139 11--, 140 ll-83vil 5-180 5-192 45 6-7082 3-556 93 9-043I) 4-530 141 11-8743 5-204 46 6-7823 3583 94 9-U953 4-546 142 119163 5-217 47 6-8556 3608 95 9-7467 4-562 143 11-9582 5-229 48 6-9282 3-634 96 9-7979 4-578 144 12- 5-241 25* 296 SQUARE AJCD CUBE ROOTS. No. Square root. Cube root. HO. Square root. Cube root. No. Square root. Cab* root 145 12-0415 5-253 193 13-8924 5-778 241 15-5241 6-223 146 12-0830 5-265 194 13-9283 5-788 242 15-5563 6-231 147 12-1243 5-277 195 13-9642 5-798 243 15-5884 6-240 148 12-1655 5-289 196 14- 5-808, 244 15-6204 6-248 149 12-2065 5-301 197 14-0356 5-818 245 15-6524 6-257 150 12-2474 5-313 198 14-0712 5-828 246 15-6843 6-265 151 12-2882 5-325 199 14-1067 5-838 247 15-7162 6-274 152 12-3288 5-336 200 14-1421 5-848 248 15-7480 6-282 153 12-3693 5-348 201 14-1774 5-857 249 15-7797 6-291 154 12-4096 5-360 202 14-2126 5-867 250 15-8113 6-299 155 12-4498 5-371 203 14-2478 5-877 251 15-8429 6-307 156 12-4899 5-383 204 14-2828 5-886 252 15-8745 6-316 157 12-5299 5-394 205 14-3178 5-896 253 15-9059 6-324 158 12-5698 5-406 206 14-3527 5-905 254 15-9373 f 333 159 12-6095 5-417 207 14-3874 5-915 255 15-9687 &-341 160 12-6491 5-428 208 14-4222 5-924 256 16- 6-349 161 12-6885 5-440 209 14-4568 5-934 257 16-0312 6-357 162 12-7279 5-451 210 14-4913 5-943 258 16-0623 6-366 163 12-7671 5-462 211 14-5258 5-953 259 16-0934 6-374 164 12-8062 5-473 212 14-5602 5-962 260 16-1245 6382 165 12-8452 5-484 213 14-5945 5-972 261 16-1554 6-390 166 12-8840 5-495 214 14-6287 5-981 262 16-1864 6-398 167 12-9228 5-506 215 14-6628 5-990 263 16-2172 6-406 168 12-9614 5-517 216 14-6969 6- 264 16-2480 6-415 169 13- 5-528 217 14-7309 6-009 265 16-2788 6-423 170 13-0384 5-539 218 14-7648 6-018 266 16-3095 6-431 171 13-0766 5-550 219 14-7986 6-027 267 16-3401 6-439 172 13-1148 5-561 220 14-8323 6-036 268 16-3707 6-447 173 13-1529 5-572 221 14-8660 6-045 269 16-4012 6-455 174 13-1909 5-582 222 14-8996 6-055 270 16-4316 6-463 175 13-2287 5-593 223 14-9331 6-064 271 16-4620 6-471 176 13-2664 5-604 224 14-9666 6-073 272 16-4924 6-479 177 13-3041 5-614 225 15- 6-082 273 16-5227 6-487 178 13-3416 5-625 226 15-0332 6-091 274 16-5529 6-495 179 13-3790 5-635 227 15-0665 6-100 275 16-5831 6-502 180 13-4164 5-646 228 15-0996 6-109 276 16-6132 6-510 181 13-4536 5-656 229 15-1327 6-118 277 16-6433 6-518 182 13-4907 5-667 230 15-1657 6-126 278 16-6733 6-526 183 13-5277 5-677 231 15-1986 6-135 279 16-7032 6-534 184 13-5646 5-687 232 15-2315 6-144 280 16-7332 6-542 185 13-6014 5-698 233 15-2643 6-153 281 16-7630 6-549 186 13-6381 5-708 234 15-2970 6-162 282 16-7928 6-557 187 13-6747 5-718 235 15-3297 6-171 283 16-8226 6-565 188 13-7113 5-728 236 15-3622 6-179 284 16-8522 6-573 189 13-7477 5-738 237 15-3948 6-188 285 16-8819 6-580 190 13-7840 5-748 238 15-4272 6-197 286 16-9115 6-588 191 13-8202 5-758 239 15-4596 6-205 287 16-9410 6-596 192 13-8564 5-768 240 15-4919 6-214 288 16-9705 6-603 SQUARE AND CUBE ROOTS. 297 ;: 8quurool. 'ubr root. No. Square root. ?ute root. No. Square root. Cub* roc 1 289 17- 6-611 337 18-3575 6-958 385 19-6214 7-274 290 17-0293 6-<>19 338 18-3847 6-965 386 19-6468 7-281 291 17-0587 6-626 339 18-4119 6-972 387 19-6723 7-287 292 17-0880 6-634 340 18-4390 6-979 388 19-6977 7-293 293 17-1172 6-641 341 18-4661 6-986 389 19-7230 7-299 294 17-1464 6-649 342 18-4932 6-993 390 19-7484 7-306 295 17-1755 6-656 343 18-5202 7- 391 19-7737 7-312 296 17-2046 6-664 344 18-5472 7-006 392 19-7989 7318 297 17-2336 6-671 345 18-5741 7-013 393 19-8242 7-324 298 17-2626 6-679 346 18-6010 7-020 394 19-8494 7-331 299 17-2916 6-686 347 18-6279 7-027 395 19-8746 7-337 300 17-3205 6-694 348 18-6547 7-033 396 19-8997 7-343 301 17-3493 6-701 349 18-6815 7-040 : 397 19-9248 7-349 302 17-3781 6-709 350 18-7082 7-047 398 19-9499 7-355 303 17-4068 6-716 351 18-7349 7-054 399 19-9749 7-361 304 17-4355 6-723 352 18-7616 7-060 400 20- 7-368 305 17-4642 6-731 353 18-7882 7-067 401 20-0249 7-374 306 17-4928 6-738 354 18-8148 7-074 402 20-0499 7-380 307 17-5214 6-745 355 18-8414 7-080 403 20-0748 7-386 308 17-5499 6-753 356 18-8679 7-087 404 20-0997 7-39S 309 17-5783 6-760 357 18-8944 7-093 405 20-1246 7-398 310 17-6068 6-767 358 18-9208 7-100 406 20-1494 7-404 311 17-6351 6-775 359 18-9472 7-107 407 20-1742 7-410 312 17-6635 6-782 360 18-9736 7-113 408 20-1990 7-416 313 17-6918 6-789 361 19- 7-120 409 20-2237 7-422 314 17-7200 6-796 362 19-0262 7-126 410 20-2484 7-428 315 17-7482 6-804 363 19-0525 7-133 411 20-2731 7-434 316 17-7763 6-811 364 19-0787 7-140 412 20-2977 7-441 317 17-8044 6-818 365 19-1049 7-146 413 20-3224 7-447 318 17-8325 6-825 366 19-1311 7-153 414 20-3469 7-453 319 17-8605 6-832 367 19-1572 7-159 415 20-3715 7-459 320 17-8885 6-839 368 19-1833 7-166 416 20-3960 7-465 321 17-9164 6-847 369 19-2093 7-172 417 20-4205 7-470 322 17-9443 6-854 370 19-2353 7-179 418 20-4450 7-476 323 17-9722 6-861' 371 19-2613 7-185 419 20-4694 7-482 324 18- 6-868 372 19-2873 7-191 420 20-4939 7-488 325 18-0277 6-875 373 19-3132 7-198 421 20-5182 7-494 326 18-0554 6-882 374 19-3390 7-204 422 20-5426 7-5dO 327 18-0831 6-889 375 19-3649 7-211 423 20-5669 7-506 328 18-1107 6-896 376 19-3907 7-217 424 20-5912 7-512 329 18-1383 6-903 377 19-4164 7-224 425 20-6155 7-518 330 18-1659 6-910 378 19-4422 7-230 426 20-6397 7-524 331 18-1934 6-917 379 19-4679 7-236 427 20-6639 7-530 332 18-2208 6-924 380 19-4935 7-243 428 20-6881 7-536 333 18-2482 6-931 381 19-5192 7-249 429 20-7123 7-541 334 18-2756 6-938 382 19-5448 7-255 ; 430 20-7364 7-547 335 18-3030 6-945 383 19-5703 7-262 431 20-7605 7-553 836 18-3303 6*853 384 19-5969 7-268 1) 438 20-7848 7-559 89b SQUARE AND CUBE ROOTS. Mo. Squire root. Cuberdbt. No. Squire root. Cube root. No. Square root. Cube root. 433 20-8086 7-565 481 21-9317 7-835 529 23- 8-087 434 20-8326 7-571 482 21-9544 7-840 530 23-0217 8-092 435 20-8566 7-576 483 21-9772 7-846 531 23-0434 8-097 436 20-8806 7-582 484 22- 7-851 532 23-0651 8-102 437 20-9045 7-588 485 22-0227 7-856 533 23-0867 8-107 438 20-9284 7-594 486 22-0454 7-862 534 23-1084 8-112 439 20-9^23 7-600 487 22-0680 7-867 535 23-1300 8-118 440 20-9761 7-605 488 22-0907 7-872 536 23-1516 8-123 441 21- 7-611 489 22-1133 7-878 537 2:M732 8-128 442 21-0237 7-617 490 22-1359 7-883 538 23-1948 8-133 443 21-0475 7-623 491 22-1585 7-889 539 23-2103 8-138 444 21-0713 7-628 492 22-1810 7-894 540 23-2379 8-143 445 21-0950 7-634 493 22-2036 7-899 541 23-2594 8-148 446 21-1187 7-640 494, 22-2261 7-905 542 23-2808 8-153 447 21-1423 7-646 495 22-2485 7-910 543 23-3023 8-158 448 21-1660 7-651 496 22-2710 7-915 544 23-3238 8-163 449 21-1896 7-657 497 22-2934 7-921 545 23-3452 8-168 450 21-2132 7-663 498 22-3159 7-926 546 23-3666 8-173 451 21-2367 7668 499 22-3383 7-931 547 23-3880 8-178 452 21-2602 7-674 500 22-3606 7-937 548 23-4093 8-183 453 21-2837 7-680 501 22-3830 7-942 549 23-4307 8-188 454 21-3072 7-685 502 22-4053 7-947 550 23-4520 8-193 455 21-3307 7-691 503 22-4276 7-952 551 23-4733 8-198 456 21-3541 7-697 504 22-4499 7-958 552 23-4946 8-203 457 21-3775 7-702 505 22-4722 7-963 5f)3 23-5159 8-208 458 21-4009 7-708 506 22-4944 7-968 554 23-5372 8-213 459 21-4242 7-713 507 22-5166 7-973 555 23-5584 8-217 460 21-4476 7-719 508 22-5388 7-979 556 23-5796 8-222 461 21-4709 7-725 509 22-5610 7-984 557 23-6008 8-227 462 21-4941 7-730 510 22-5831 7-989 558 23-6220 8-232 463 21-5174 7-736 511 22-6053 7-994 559 23-6431 8-237 464 21-5406 7-741 512 22-6274 8- 560 23-6643 8-242 465 21-5638 7-747 513 22-6405 8-005 561 23-6854 9-247 466 21-5870 7-752 514 22-6715 8-010 562 23-7065 8-252 467 21-6101 7-758 515 22-6936 8-015 563 23-7276 8-257 468 21-6333 7-763 516 22-7156 8-020 564 23-7486 8-262 469 21-6564 7-769 517 22-7376 8-025 565 23-7697 8-267 470 21-6794 7-774 518 22-7596 8-031 566 23-7907 8-271 471 21-7025 7-780 519 22-7815 8-036 567 23-8117 8-276 472 21-7255 7-785* 520 22-8035 8-041 568 23-8327 8-281 473 21-7485 7-791 521 22-8254 8-046 569 23-8537 8-286 474 21-7715 7-796 522 22-8473 8-051 570 23-8746 8-291 475 21-7944 7-802 523 22-8691 8-056 571 23-8956 8-296 476 21-8174 7-807 524 22-8910 8-062 572 23-9165 8-301 477 21-8403 7-813 525 22-9128 8-067 573 23-9374 8-305 478 21-8632 7-818 526 22-9346 8-072 574 23-9582 8-310 )479 21-8860 7-824 527 22-9564 8-077 575 23-9791 8-315 480 21-9089 7-829 5^8 22-9782 8-082 576 24- 8-320 SQUARE AND CUBE ROOTS. 299 No. Square Tool. i Cube root. fc Square root. Cube root. No. S pre root. Cub. mot. 577 24 0208 8-325 625 25- 8-549 673 25-9422 8-763 578 24-0416 8-329 G2C, ^5-0199 8-554 674 25-9615 8-767 579 24-0624 8-334 <;-,'7, 26-0399 07 5 25-9807 8-772 580 24-0831 8-339 628 25-^)599 8-563 676 26- 8-776 581 24-1039 8-344 629 25-0798 8-5C8 <;-,? 26-0192 8-780 582 24-1246 8-349 630 25-0998 8-6T2 678 26-0384 8-785 583 24-1453 8-353 631 25-1197 8-577 2()-(i:>"/(i 8-789 584 24-1660 8-358 632 25-13!*6 8-581 680 26-0768 8-793 585 24-1867 8-363 633 25-1594 8-586 t;si 26-0959 8-797 586 24-2074 8-368 634 25-1793 8-590 26-1151 8-802 587 24-2280 8-372 635 25-1992 8-595 683 26-1342 8-806 588 24-2487 8-377 636 25-2190 8-599 J684 26-1533 8-810 589 24-2693 8-382 637 25-2388 8-604 685 26-1725 8-815 590 24-2899 8-387 638 25-2586 8-608 IkSli 26-1916 8-819 591 24-3104 8-391 639 25-2784 8-613 687 26-2106 8-823 592 24-3310 8-396 640 25-2982 8-617 688 26-2297 8-828 593 24-3515 8-401 641 25-3179 8-622 689 26-2488 8-832 594 24-3721 8-406 642 25-3377 8-626 690 26-2678 8-836 595 24-3926 8-410 643 25-3574 8-631 61)1 26-2868 8-840 596 24-4131 8-415 644 25-3771 8-635 i)!>2 26-3058 8-845 597 24-1335 8-420 645 25-39B8 8-640 r,!:: 26-3248 8-849 698 24-4540 8-424 646 25-4165 8-644 694 26-3438 8-8M 599 24-4744 8-429 647 25-4361 8-649 695 26-3628 8-857 600 24-4948 8-434 648 25-4558 8-653 69<> 26-3818 8-862 601 24-5153 8-439 649 25-4754 8-657 897 26-4007 8-866 602 24-5356 8-443 650 25-4950 8-662 098 26-4196 8-870 603 24-5560 8-448 651 25-5147 8-666 6