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 THURSTON # ANIMAL AS MACHINE AND 
 
 PRIME MOTOR AND LAWS OF ENERGETIC 
 
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The Publishers and the Author will be grateful to 
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 their attention to any errors of omission or of commission 
 that they may find therein. It is intended to make 
 our publications standard works of study and reference, 
 and, to that end, the greatest accuracy is sought. It 
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 size are free from errors ; but it is the endeavor of the 
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 may be aided in his task of revision, from time to time, 
 by the kindly criticism of his readers. 
 
 JOHN WILEY & SONS. 
 53 East Tenth Street. 
 
I 
 
 I 
 
THE ANIMAL ^ ^^ 
 
 AS A 
 
 MACHINE AND A PRIME MOTOR, 
 
 AND THE LAWS OF ENERGETICS. 
 
 R. H. THURSTON, 
 
 FIRST EDITION, 
 FIRST THOUSAND. 
 
 NEW YORK: 
 
 JOHN WILEY & SONS, 
 
 53 East Tenth Street. 
 1894. 
 
Copyright, 1894, 
 
 BY 
 
 R. H. THURSTON. 
 
CONTENTS. 
 
 I. INTRODUCTION. 
 
 ^''^- PAGE 
 
 1. Energy and its Transformation i 
 
 2. Forces and their Classification n 
 
 3. Energy defined - 
 
 4. Mechanics defined 3 
 
 5. Energetics defined g 
 
 6. Relations of Matter, Force, and Energy . . . .10 
 
 7. Laws of Energetics 24 
 
 8. Newton's Laws 26 
 
 9. Algebraic Expression of Energy-changes . . . .27 
 
 10. The Object of all Mechanism 30 
 
 11. The Sources and Kinds of Energy 31 
 
 12. Forms of Motor . , , 3^ 
 
 II. THE ANIMAL AS A PRIME MOTOR. 
 
 13. The Animal as a Machine 37 
 
 14. The Animal as a Motor ........ 38 
 
 15. The Processes of Vital Machines 45 
 
 16. The Efficiency of the Animal System 50 
 
 17. The Work of the Animal Machine 50 
 
 18. Work of Men and Animals 53 
 
 19. Effective Methods of Application of Power . . . .59 
 
 20. Draught of Vehicles ••...... 61 
 
 21. Intensity of Muscular Efifort 58 
 
 22. The Uses of Food ^q 
 
 23. Dietaries •••••••... 73 
 
 24. Mechanism of Transmission of Force 78 
 
 iii 
 
IV CONTENTS. 
 
 ART. PAGE 
 
 25. Equation of Applied Animal Power 79 
 
 26. Selection and Care of Men and Animals . . . .80 
 
 III. FINAL DEDUCTIONS. 
 
 27. Progress of Improvement 84 
 
 28. Objects of Search ...... . . 86 
 
 29. The Living Body as a Machine 89 
 
 30. Methods of Production of Animal Energy . . . .92 
 
 31. Advantages of Substitution of Nature's Methods . . -94 
 
 32. Costs 97 
 
THE ANIMAL 
 
 AS A 
 
 MACHINE AND A PRIME MOTOR 
 
 INTRODUCTION. 
 
 ENERGY AND ITS TRANSFORMATIONS. 
 
 ENERGETICS AND ITS LAWS. 
 
 I. Energy and its Transformations are the source 
 and the method of all useful work, as of all natural 
 phenomena involving motions of masses or of mole- 
 cules of whatever kind. All '' prime movers " are ma- 
 chines by means of which man diverts energy from 
 natural channels and compels it to do his own work. 
 The water-wheels and windmills simply transfer the 
 energy of the moving fluid to the machinery of the 
 transmission through which it performs useful work ; 
 the heat-engines and electric machinery transfer energy, 
 and at the same time convert it from the thermal or the 
 electrical to the dynamic form for application, and 
 thermodynamic or electro-dynamic apparatus thus have 
 two distinct functions. 
 
 In some instances we may observe a succession of 
 
2 THE ANIMAL AS A MACHINE. 
 
 transformations of energy, as where a steam boiler 
 transforms, and stores for transmission to the engine, 
 energy of chemical afifinity ; the engine, in turn, trans- 
 forming it into mechanical energy and transmitting it 
 to a dynamo-electric machine, where it is again trans- 
 formed, changing into the electrical current, to be sent 
 perhaps miles away to an electro-dynamic machine or 
 motor, where its retransformation into mechanical 
 power occurs, and it is set at the work of driving a mill 
 or other collection of mechanisms. A telephone sys- 
 tem illustrates in another way similar transformations 
 and retransformations of mechanical and electric energy, 
 and Mr. Hammer has thus produced a system involving 
 many transformations and including a circuit of a hun- 
 dred miles. 
 
 Nature herself has in these cases usually already per- 
 formed some such transformations of energy in the 
 reduction of that so collected and applied to the form 
 in which the mechanic and the engineer finds it ready 
 to his hand. The water has been raised from the lakes 
 and the sea, and distributed by the clouds to the elevated 
 sources from which it flows downward in the streams ; 
 the winds are the result of differences of temperature 
 and the action of heat energy ; the heat of combustion 
 is the representative of an earlier form of energy in 
 which the heat of the sun and of the still cooling earth, 
 and the formation of the coal deposits in early geo- 
 logical periods, played a part. In a general way it has 
 come to be seen that every display of energy, like every 
 new form of matter, is the result of change in some 
 antecedent form, and that neither matter nor energy 
 can be destroyed. This has been admitted from the 
 time of Lavoisier, so far as it affects matter ; it has 
 
ENERGY AND ITS TRANSFORMATIONS. 3 
 
 been admitted as applicable to physical energy since 
 the doctrines of the correlation of forces and the per- 
 sistence of energy became accepted by men of science ; 
 and we are gradually progressing towards the establish- 
 ment of a law of persistence of all existence, whether 
 of matter, of force and energy, or of organic vitality, 
 and perhaps even to its extension until it includes in- 
 tellectual and soul life. 
 
 We see that in the beginning there entered upon 
 an existence of indefinite duration a great universe 
 of matter endowed with its characterizing attributes 
 — the forces. These forces, acting upon a definite 
 quantity of matter with definite intensity, give origin 
 to a fixed amount of actual energy, and become capa- 
 ble of producing another fixed quantity of what is now 
 potential energy. Energy thus brought into exist- 
 ence remains constant in total amount as the quantity 
 of created matter remains constant. 
 
 The action of these forces upon this matter has given 
 rise to every phenomenon which has come, or which 
 can come, within the range of scientific inquiry. 
 
 2. Forces are Classified, according to their methods 
 of affecting matter, into three great classes : 
 
 (i) Those forces with which we are able to make 
 ourselves so readily and thoroughly familiar that we find 
 no difficulty in assigning to each of them its proper 
 place in the scheme of scientific systematization, and 
 which we have found it comparatively easy to distin- 
 guish by their peculiar and readily observed effects. 
 These include the familiar physical forces, as gravita- 
 tion, electrical, chemical, and mechanical forces. 
 
 (2) The vital forces — those which are preservative of 
 all life, which produce and promote the growth of or- 
 
4 THE ANIMAL AS A MACHINE. 
 
 ganisms having life, and which are less easily under- 
 stood, more difficult to study, and far less subject to 
 the modifying power of human action, than are those 
 of the first described class. 
 
 (3) The forces of the soul and of the intellect — 
 those most wonderful and most mysterious of all known 
 forms of force — forces of the nature of which we know 
 nothing, and of the effects of which, actual and possible, 
 we have the least comprehension. 
 
 By the study of the universe as it now exists, philos- 
 ophers are led to perceive that its present state is such 
 as would have resulted had the various forms of matter 
 with which we are surrounded, and of which we our- 
 selves are corporeally formed, and had other existences 
 which we suppose to form a part of our universe been, 
 at the beginning, so distributed and so placed in refer- 
 ence to the several kinds of forces that the former, 
 acted freely upon by the latter, should, by a continuity 
 of never-ceasing, ever-progressing change, take those in- 
 finite variations of growth, and all that inconceivable 
 variety of shapes, that have supposed to have been, by 
 the process called '' evolution," brought into the visible 
 universe.* 
 
 Studying the accessible universe, as far as we are per- 
 mitted, in greater detail, we find that each of the var- 
 ious kinds of forces set at work to modify the position 
 and character of matter has a special part to play, a 
 peculiar work to do ; we find that the first class has a 
 
 *As early as 1854 Helmholtz showed that the condensation of an 
 infinitely diffused nebulous mass of matter, to form the stellar systems 
 of the universe, by gravitation, was sufficient to furnish all existing 
 heat-energy, and a source of all that mechanical and other transformed 
 energy known now to exist. 
 
ENERGY AND ITS TRANSFORMATIONS. 5 
 
 sphere of operation which is fully within the reach of 
 our senses; that the second class of forces is also, to a 
 certain extent, familiar to us through a knowledge of 
 their effects: but the last of these several classes of 
 forces existing in nature is, as yet, quite beyond our 
 ken. 
 
 Studying these forms of manifestation of force which 
 are divided between the first two classes, we perceive a 
 distinction which is as well defined as is the line sepa- 
 rating the two classes of phenomena to which they give 
 rise. 
 
 (i) T\iQ physical forces — and it is intended here to in- 
 clude the mechanical and chemical, as well as the forces 
 which are usually alone treated of in works on physics — 
 are capable of being observed, of being distinguished 
 by certain readily defined qualities, and of being ac- 
 curately measured quantitatively. The conditions which 
 lead to their active display are capable of being ex- 
 actly ascertained, and the precise results of their opera- 
 tions under any given set of conditions may usually be 
 accurately predicted. These conditions are subject to 
 certain definite modifications by the power of man, 
 and the changes of effect which will result from such 
 changes of condition may be predicted. The effects 
 which nature produces in certain cases by the action of 
 these forces may be modified by man without entirely 
 defeating the original tendency to bring about a certain 
 change of mode of action of existing energy. These 
 forces, acting alone, never give rise to the more intri- 
 cate forms seen in nature. Their highest product in 
 the whole morphological range is a crystal of more or 
 less perfect shape, but of a form which is always of 
 some simple geometrical class. These forces do not 
 
6 THE ANIMAL AS A MACHINE. 
 
 exhibit the play of definitely directed energy tending 
 to effect a perfectly well defined, though remote, re- 
 sult. Their effects are the accidental and the inci- 
 dental, so far as the more wonderful and most intricate 
 of the operations of nature are concerned. 
 
 (2) The vital forces, on the other hand, effect opera- 
 tions which human power can only touch to impede or 
 to destroy. They have for their mission the creation of 
 strangely complicated and curiously organized struc- 
 tures, in ivhich are stored certain definite amounts of 
 energy, and which are given a power of acquiring and 
 of applying extraneous energy, in probably also defi- 
 nite amount, to the accomplishment of certain tasks. 
 Man may modify their operation and may produce 
 some change in the phenomena which they are ap- 
 pointed to bring about ; but it is only by deranging 
 their action. He can mar their work, but cannot di- 
 rectly aid them. That store of vital energy which was 
 created in the infinite past, and which is now passing 
 through one after another of the forms of life, new and 
 old, which are constantly coming into the field of our 
 cognizance, and as constantly disappearing from view, 
 is continually developing organisms of every grade from 
 the simple life-seed, if such exist — from the basic pro- 
 toplasm — to the human ruler of them all. 
 
 Of these two sets of forces, the one is blind and aim- 
 less, unintelligent as to the direction of its efforts, in- 
 different as to its results, and is governed by laws 
 which, under all known conditions, are as simple as 
 they are invariable. The other set appears to act at 
 all times upon a definite, far-reaching plan, and these 
 forces set themselves intelligently about the production 
 of the most elegant and intricate of designs, and the 
 
ENERGY AND ITS TRANSFORMATIONS. 7 
 
 elaboration of the most wonderful and mysterious of 
 organisms. It is only in the structures which are their 
 work that the strange, the incomprehensible phenom- 
 ena of life are exhibited to the intelligence which 
 vainly endeavors to understand them."^ 
 
 3. Energy, "living Force," ever-living force, as we 
 are now learning to regard it ; vis viva, as its first 
 discoverer, Leibnitz, called it ; the force illustrated in 
 all life and motion, as we now know it ; energy, as Dr. 
 Young first denominated it : all these expressions for 
 one common quality of every body, substance, or 
 system, in motion either as to its atoms or molecules 
 or as to its mass, denote that mysterious property 
 by which all growth, all life, all changes in physical 
 things or physical substance are brought about and 
 continued. The work of the vegetable kingdom, in 
 the elevation of the simpler, inorganic compositions 
 found in nature to the higher, complex, organic forms 
 in which they find their culmination ; those of the ani- 
 mal system which take these complex forms and erect 
 them in a still more complicated animal structure and 
 supply it with the powers of animal life ; the work of 
 the living creature in again reducing these complicated 
 structures to the lower and simplest forms, availing it- 
 self of their latent energy in the production of all the 
 grandest results of physical and intellectual life : all 
 these are but manifestations in various ways of the 
 ever-living forces, the never-ceasing energies, of the 
 universe. 
 
 In its two forms, kinetic and potential, actual and 
 
 *The preceding matter is from the vice-president's address before 
 the American Association for the Advancement of Science, R. H. 
 Thurston, 1878. 
 
8 THE ANIMAL AS A MACHINE. 
 
 latent, the sum of which is constant throughout the 
 universe, energy is the source and the basis of all life, 
 of all motion, of all development, of all evolution. It 
 is the mainspring of all physical phenomena ; and the 
 science of Energetics is the foundation of chemistry, 
 as of physics ; of astronomy, as of the mechanics of en- 
 gineering. Whatever we know of matter, even, is dis- 
 covered to us by these methods of display of energy in 
 connection with it. 
 
 The science of energetics itself is one division of a 
 broader science, that of Mechanics, — that great science 
 which bears more or less directly upon every phenom- 
 enon of nature and the universe, and which is at the 
 foundation of all the applied sciences, of all the arts of 
 construction, of all the exact sciences of physics and 
 chemistry, of astronomy, and of forces and motions. 
 
 4. Mechanics thus includes four principal divisions :* 
 (i) Statics treats of the relations of forces acting in 
 
 any system when no motion results from that action. 
 
 (2) Kinematics treats of the relations of motions sim- 
 ply, of their composition and resolution, and of their 
 resultant effects. 
 
 (3) Dynamics or Ki7ietics treats of the motions pro- 
 duced in ponderable bodies by the action of forces. 
 
 (4) Energetics treats of the measurement, the trans- 
 fer, and the transformations of energy under the action 
 of forces, and of their result in the variation of the 
 method of its manifestation. 
 
 5. Energetics is defined, therefore, as that science 
 which treats of all natural phenomena which, through 
 
 * Several pages are here taken mainly from "The Manual of the 
 Steam Engine," vol. i, by R. H. Thurston ; N. Y., J. Wiley & Sons. 
 
ENERGY AND ITS TRANSFORMATIONS. g 
 
 the action of force upon matter, result in the produc- 
 tion of motion ; whether it be a relative motion of 
 atoms, of molecules, or of masses. It is that science 
 " whose subjects are material bodies and physical phe- 
 nomena." * We may here repeat : 
 
 Energetics thus treats of modifications of energy 
 under the action of forces, and of its transformation 
 from one mode of manifestation to another, and from 
 one body to another ; and within this broader science 
 is comprehended that latest of the minor sciences — of 
 which the heat-engines and especially the steam-engine 
 illustrate the most important applications — Thermo- 
 dynamics, The science of energetics is simply a wider 
 generalization of principles which have been established 
 one at a time, and by philosophers widely separated, 
 both geographically and historically, by both space 
 and time, and which have been slowly aggregated, to 
 form one after another of the physical sciences, and 
 out of which we are slowly evolving wider generaliza- 
 tions ; thus tending toward a condition of scientific 
 knowledge which renders more and more probable the 
 truth of a principle, still broader than this science, 
 even, and which was enunciated before Science had a 
 birthplace or a name ; i.e. : 
 
 All that exists, whether matter or force, and in zv hat- 
 ever form, is indestructible by any finite poiuer. 
 
 As already remarked, that matter is indestructible 
 by finite power became admitted as soon as the chem- 
 ists, led by Lavoisier, began to apply the balance, and 
 jwere thus able to show that in all chemical change there 
 occurs only a modification of form or of combination 
 
 * Rankine ; Proc, Phil. Soc. Glasgow ; vol. iii. No. 6. 
 
10 THE ANIMAL AS A MACHINE. 
 
 of elements, and no loss of matter ever takes place. 
 The " persistence " of energy was a later discovery, con- 
 sequent largely upon the experimental determination of 
 the convertibility of heat-energy into other forms and 
 into mechanical work, for which we are indebted to 
 Rumford and Davy, and to the determination of the 
 quantivalence anticipated by Newton, shown and com- 
 puted approximately by Colding and Mayer, measured 
 with great accuracy by Joule and Rowland. 
 
 It is now generally understood that all forms 
 of energy are mutually convertible with a definite 
 quantivalence ; and it is not certain that even vital 
 and mental energy do not fall within the same cate- 
 gory. 
 
 The essentially important, as well as interesting, fact, 
 in this connection, to the engineer as well as to the 
 physicist, it should be noted, is that the laws of ener- 
 getics apply unqualifiedly to atomic and molecular 
 phenomena, as well as to energies of masses, and to all 
 transformations of energy in either class and of any 
 kind. There is, dynamically, absolutely no distinction, 
 in this respect, between the methods and processes of 
 chemistry, of physics, and of the mechanics of masses. 
 All illustrate phases of one science, and all are ener- 
 gies of matter in motion. 
 
 6. Matter, Force, and Energy are the only quan- 
 tities known to the departments of natural science. 
 The science of CJiemistry deals with the forms which 
 matter assumes under the action of measurable atomic 
 molecular forces affecting dissimilar kinds of matter ; 
 Physics is that science which deals with all the other 
 forms of sensible force and their effects. The science 
 of Energetics treats of the action of forces producing 
 
ENERGY AND ITS TRANSFORMATIONS. II 
 
 or modifying energy, whatever the kind of force, what- 
 ever the kind of matter : it thus covers the whole 
 range of chemistry and physics. 
 
 Matter is that which is capable of directly affecting 
 the senses, and which occupies space. Nothing is 
 known of the ultimate nature of matter, and we are 
 acquainted with it only as it affects the organs of the 
 body. It is usually divided into four classes : solids, 
 liquids, gases, and imponderable matter ; the latter 
 meaning that which cannot be assigned a finite specific 
 measure of mass or weight. The luminiferous ether is 
 an example of this last ; the other three are familiar 
 forms. 
 
 A Body is a limited portion of matter. 
 
 Force is that which produces, or tends to produce, 
 motion, or change of motion, in bodies ; it is measured 
 statically by the weight which will counterpoise it or 
 by comparison with a known standard of force, and 
 dynamically by the velocity which it will give a known 
 freely moving mass in a stated time, i.e., by the "ac- 
 celeration " which it is capable of producing. 
 
 Work is always performed by the expenditure of 
 energy, and is the product of the resistance overcome 
 by a force, or of the effort exerted by it, into the space 
 through which that action takes place. That resistance 
 may be constant, or variable, and due to an active, oppos- 
 ing force, to resisting pressure, to the inertia of masses, 
 or of molecules compelled to submit to acceleration or 
 retardation ; or it may be due to any one of the phys- 
 ical or chemical forces. Thus, if U represents the work 
 done by a force, F, acting through a space, s, 
 
 [/=Fs = Rs; (i) 
 
12 THE ANIMAL AS A MACHINE, 
 
 and for motion variable only, 
 
 dU=Fds (2) 
 
 For variable forces, 
 
 dU = sdF. (3) 
 
 For forces and motion variable, 
 
 dU=d{Fs) (4) 
 
 The Unit of Work is the product of the units of its 
 factors force and space, as the foot-pound, the kilo- 
 grammetre, the foot-ton, the gramme-centimetre. 
 
 Useful Work is that which is applied to the produc- 
 tion of a specified useful effect ; Lost Work is that 
 which is incidentally wasted, in the endeavor to per- 
 form useful work, in overcoming prejudicial resistances, 
 and in doing useless work ; this waste occurs usually 
 and principally in overcoming friction of moving 
 parts. 
 
 Work of Acceleration is work expended in producing 
 increased velocity in a freely moving body. The effort 
 exerted, and the resistance met, is dependent upon the 
 inertia of the mass, and is measured thus : A body 
 moving freely under the action of gravity, i. e., of a 
 force equal to its own weight, acquires, in this latitude, 
 a velocity of 32.2 feet (9.81 metres), nearly, in one 
 second, and the acceleration, or retardation, of any 
 freely-moving body is proportional to the effort applied, 
 as to the resistance met by it. If /is the actual accel- 
 eration, if g measures that produced by gravity, if F is 
 
ENERGY AND ITS TRANSFORM A l^IONS. 1 3 
 
 the statical measure of the effort, and PFis the weight 
 of the body, we have 
 
 F'.VVv.f'.g: t:i::v,-v,:f; 
 
 g 
 
 -'^^^= (5) 
 
 v^ and 7', being the initial and final velocities, and t the 
 time of action of the accelerating force. 
 
 fc> 
 
 For variable acceleration, 
 
 /=S^ <^) 
 
 ^=f-f « 
 
 V + V 
 
 The space, s, is equal to "^""^ A and the work done 
 is, for uniform acceleration, 
 
 t 2 g 
 
 W^ ^ (8) 
 
 For variable acceleration, 
 
 7/' vdv 
 
 [/^d{Fs)==: lV.d.— = W — . . . (9) 
 
14 THE ANIMAL AS A MACHINE. 
 
 Since -^- = //, the height due the velocity v, the work 
 
 is equal to that required to raise the body through the 
 difference of the two heights due the initial and the 
 final velocities, respectively. 
 
 Where the motion of the machine or of the part 
 doing work is circular, the space traversed may be 
 measured by the angular motion a, multiplied by the 
 lever-arm, /, and their product, multiplied by the force, 
 R^ exerted, gives the measure of the work done. Thus : 
 
 in which last expression ;/ is the number of revolutions 
 made in the unit of time. 
 
 These values are equivalent to the product of the 
 angular motion into the moment of the resistance. 
 
 Work may also be measured, as in steam, air, gas, or 
 water pressure engines, by the product of the area of 
 piston, A^ the mean intensity of pressure upon it, /, the 
 length of stroke of piston, /, and the number of strokes 
 made. Thus, 
 
 U = Aphi 
 = Aps 
 = PV, (II) 
 
 when V is the volume of the working cylinder multiplied 
 by the number of strokes ; in other words, the volume 
 traversed by the piston. 
 
 Where the force acting, or the resistance, acts ob- 
 liquely to the path traversed, it is evident that only the 
 component in that path is to be considered. 
 
 Diagrams exhibiting the amount of work done and 
 
ENERGY AND ITS TRANSFORMATIONS. 1 5 
 
 the method of its variation are often found useful. In 
 such diagrams the ordinate is usually made propor- 
 tional to the force acting, or to the resistance, while the 
 abscissas are made to measure the space traversed. 
 The curve then exhibits the relations of these two 
 quantities, and the enclosed area is a measure of the 
 work performed. With a constant resistance, the figure 
 is rectilinear and a parallelogram ; with variable veloci- 
 ties and resistances, it has a form characteristic of the 
 methods of operation of the part or of the machine 
 the action of which it illustrates. 
 
 Power is defined as the rate of work^ and is meas- 
 ured by the quantity of work performed in the unit 
 of time, as in foot-pounds or in kilogrammetres, per 
 minute or per second. The unit commonly employed 
 by engineers is the "horse-power," which was defined 
 by Watt as 33,000 foot-pounds per minute, equivalent 
 to 550 per second, or 1,980,000 foot-pounds per hour. 
 This is considered to be very nearly the amount of 
 work performed by the very heavy draught-horses of 
 Great Britain ; but it considerably exceeds the power 
 of the average dray-horse of that and other countries, 
 for which 25,000 foot-pounds may be taken as a good 
 average amount. 
 
 The metric horse-power, called by the French the 
 cheval-vapair, or force de cJieval, is about ij per cent, 
 less than the British, being 542.47 foot-pounds or 75 kilo- 
 grammetres per second, 4500 kilogrammetres per 
 minute, or 270,000 per hour. These quantities are al- 
 most invariably employed to measure the power ex- 
 pended and work done by machines." 
 
 * Various nations have a standard "horse-power" derived from 
 Watt's, but, owing to differences in weights and measures, they are not 
 
i6 
 
 THE ANIMAL AS A MACHINE. 
 
 It is evident that power is also measured by the pro- 
 duct of the resistance, or of the effort exerted into the 
 velocity of the motion with which that resistance is 
 overcome or that force exerted. Since s = vt^ 
 
 U=Rs= Rvt ; 
 
 and when t becomes unity, the measure of the power, 
 or of the equivalent work done in the unit of time, is 
 
 U = Rv, 
 
 in which the terms are given in units of force and space 
 as above. 
 
 The power of a prime mover is usually ascertained 
 by experimentally determining the work done in a given 
 time, the trial usually extending over some hours, and 
 often several days. It is measured in foot-pounds or 
 
 identical ; but the differences are usually less than i\ per cent. The fol- 
 lowing table, compiled by Mr. Babcock, gives these standards in kilo- 
 grammetres per second, and in foot-pounds per second expressed in 
 the foot and pound standards of each country. 
 
 STANDARD HORSE-POWER FOR DIFFERENT NATIONS. 
 
 Country. 
 
 France and Baden 
 
 Saxony 
 
 Wurtemberg 
 
 Prussia , 
 
 Hanover 
 
 England , 
 
 Austria 
 
 ■ "d 
 
 (fl-a 
 
 cflTS 
 
 m-d 
 
 cn-O 
 
 l^i 
 
 tn-O 
 
 e?3^ 
 
 •c C 
 
 •a c 
 
 S , c 
 
 CO C 
 
 ^-0 C 
 
 ceo 
 
 C G 
 
 oj C 
 
 Jr, f= ° 
 
 1^ c 
 
 
 <U 3 U 
 
 030 
 
 OJ bjC3 
 
 ■3; 3 " 
 
 w 3 
 
 ;_ 3 
 
 PI 
 
 IV:. 
 
 ?nn 
 
 nr:. 
 
 sa^ 
 
 l%z 
 
 
 4J w 
 
 i^t 
 
 ^ at 
 
 ^itt 
 
 S:^t 
 
 75 
 
 500 
 
 529.68 
 
 521-58 
 
 477-93 
 
 513-53 
 
 542-47 
 
 75 -045 
 
 500-30 
 
 530 
 
 523-89 
 
 478.22 
 
 513-84 
 
 542.80 
 
 75-240 
 
 501-36 
 
 531.12 
 
 525 
 
 479-23 
 
 514-92 
 
 543-95 
 
 75-325 
 
 502.17 
 
 531-97 
 
 525-85 
 
 480 
 
 5^5-75 
 
 544-82 
 
 75-361 
 
 502.41 
 
 532.23 
 
 526.10 
 
 480.23 
 
 516 
 
 545-08 
 
 76.041 
 
 506.94 
 
 537-03 
 
 530.84 
 
 484-56 
 
 520.65 
 
 550 
 
 76.119 
 
 507.46 
 
 537-58 
 
 531-39 
 
 485.06 
 
 521.19 
 
 550.57 
 
 CtI C 
 2 C O 
 '^ 3 U 
 
 423.68 
 423-03 
 424.83 
 425-51 
 425-72 
 429.56 
 
ENERGY AND ITS TRANSFORMATIONS. 1 7 
 
 kilogrammetres : the total work so measured is then 
 divided by the time of operation and by the value of 
 the horse-power for the assumed unit of time and the 
 mean value of the power expended thus finally ex- 
 pressed in horse-powers.* 
 
 The forces acting in machines are distinguished into 
 driving and resisting forces. That component of the 
 force, acting to produce motion in any part which lies in 
 the line of motion only, is that which does the work ; 
 and this component is distinctly called the *' Effort." 
 Similarly, only that component of the resistance which 
 lies in the line of motion is considered in measuring 
 the work of resistance. In either case, if the angle 
 formed between the directions of the motion of the 
 piece and of the driving or the resisting force be called 
 o', the effort is 
 
 P — R cos a, (12) 
 
 The other component, acting at right angles to the 
 path of the effort, is 
 
 Q = Rs\na, (13) 
 
 and has no useful effect, but produces waste of power 
 by introducing lateral pressures and consequent friction. 
 
 Energy, which is defined as capacity for performing 
 work, is either actual or potential. 
 
 Actual or Kinetic Energy is the energy of an actually 
 moving body, and is measured by the work which it is 
 capable of performing while being brought to rest, 
 under the action of a retarding force ; this work is 
 
 * Custom has not yet settled the proper form of the plural of this 
 word; there is no reason why it should not follow the rule. 
 
1 8 THE ANIMAL AS A MACHINE. 
 
 equal to the product of its weight, W, into the height, 
 
 ^'' 
 h — — , throup;h which it must fall under the action of 
 
 gravity to acquire that velocity, v^ with which it is at 
 the instant moving ; i.e., 
 
 E^U=^Wh^W~. . . . (14) 
 
 A change of velocity i\ to v^ causes a variation of 
 actual energy, E^ — E^^ and can be effected only by 
 the expenditure of an equal amount of work — 
 
 E,-E^^U^w''^^-^=W{Ji,-h:). (15) 
 
 This form of energy appears in every moving part of 
 every machine, and its variations often seriously affect 
 the working of mechanism. 
 
 The total actual energy of any system is the algebraic 
 sum of the energies, at the instant, of all its parts ; i.e., 
 
 E^:2W—', (16) 
 
 and when this energy is all reckoned as acquired or ex- 
 pended at any one point, as at the driving-point, the 
 several parts having velocities, each n times that of the 
 driving-point, which latter velocity is then v, the total 
 energy becomes 
 
 E^^w'^y- (17) 
 
 Actual energy is usually reckoned relatively to the 
 earth ; but it must often be reckoned relatively to a 
 
EXERGY AND ITS TRANSFORMATIONS. 1 9 
 
 given moving mass, in which case it measures the work 
 which the moving body is capable of doing upon that 
 mass, when brought by it to its own speed. 
 
 Potential Energy is the capacity for doing work pos- 
 sessed by a body in virtue of its position, of its condi- 
 tion, or of its intrinsic properties. Thus, a weight 
 suspended at a given height possesses the potential 
 energy, in consequence of its position, E = Wh, and 
 may do work to that amount while descending through 
 the height, //, under the action of gravity. A bent 
 bow or coiled spring has potential energy, which 
 becomes actual in the impulsion of the arrow or is ex- 
 pended in the work of the mechanism driven by the 
 spring. A mass of gunpowder or other explosive has 
 potential energy in virtue of the unstable equilibrium 
 of the chemical forces afTecting its molecules. Food 
 has potential energy in proportion to the amount of 
 vital and muscular energy derivable by its consumption 
 and utilization in the human or animal system. These 
 potential energies are not measured by the observed 
 actual energies derived from these substances in any 
 case, but are the maximum quantities possibly obtain- 
 able by any perfect system of development and utiliza- 
 tion. In practical application, more or less waste is 
 always to be anticipated. 
 
 Every instance of disappearance of actual energy in- 
 volves the performance of work, and the production of 
 potential or of some new form of actual energy in 
 precisely equal amount. A stone thrown vertically up- 
 ward loses kinetic energy as it rises, in precisely the 
 amount — resistance of the air being neglected — by 
 which it gains potential energy. A falling mass striking 
 the earth surrenders the actual energy acquired by loss 
 
20 THE ANIMAL AS A MACHINE. 
 
 of potential energy during its fall, and the equivalent 
 of the quantity so surrendered is found in the work 
 done upon the soil ; it finally passes away as the equiv- 
 alent energy of heat motion produced by friction and 
 impact. The potential chemical energy of the explo- 
 sive is the equivalent of the kinetic energy of the flying 
 projectile, and the latter has its equivalent in the work 
 done at the instant of striking and coming to rest, and 
 in the heat produced by the final change of mass- 
 motion into molecular or heat motion. 
 
 Work may be defined as that operation which re- 
 sults in a change in the method of manifestation of 
 energy, and Energy as that which is transferred or 
 transformed, when work is done. The motion of a 
 projectile is the transfer of energy from one place to 
 another. It is generated at the point of departure, 
 stored as actual or kinetic energy, transferred to the 
 point of destination, and there restored and applied to 
 the production of work. 
 
 Acceleration and retardation of masses in motion 
 can only be produced by doing work upon them, or by 
 causing them to do work, and thus, by the communi- 
 cation of energy to them or by its absorption from them, 
 in precisely the amount which measures the variation 
 of their actual energy as so produced. Every body 
 which is increasing in velocity of motion thus receives 
 and stores energy ; every mass undergoing retardation 
 must perform work, and thus must restore energy pre- 
 viously communicated to it. In every machine which 
 works continuously, and in which parts are alternately 
 accelerated and retarded, energy is stored at one period 
 and restored at another, in precisely equal amounts. 
 
 Work done upon any machine may thus be expended 
 
ENERGY AND ITS TRANSFORMATIONS. 21 
 
 partly in doing the useful work of the system, and 
 partly in storing energy ; and the same machine may 
 do work at another instant partly by expending the 
 energy received by it, and partly by expending stored 
 energy previously accumulated. 
 
 Storage or restoration of energy thus always occurs 
 when change of speed takes place. It is evident, since 
 the storage or restoration of energy implies variation 
 of speed, that the condition of uniform speed is that 
 the work done upon the machine shall at each instant 
 be precisely equal to that done by it upon other bodies. 
 The work applied must be equal to that of resistance 
 met at the driving-point. Thus, 
 
 2Pv — 2Rv'',fPdv=fRdv'', . . (i8) 
 
 and the effort at each point in the machine will be 
 equal to the resistance, and will vary inversely as the 
 velocity of the point to which it is applied ; i.e., 
 
 P v' 
 
 P'^v (^9) 
 
 In the starting of every machine, energy is stored 
 during the whole period of acceleration up to maximum 
 speed, and this energy is restored and expended while 
 the machine is coming to rest again. This latter quan- 
 tity of energy is usually expended in overcoming fric- 
 tion. 
 
 The useful and the lost work of a machine are, to- 
 gether, equal to the total amount of energy expended 
 upon the machine, i.e., to the work done upon it by its 
 'driver." The Useful \Vork\?> that which the machine 
 is designed to perform ; the Lost Work is that which is 
 
22 THE ANIMAL AS A MACHINE. 
 
 absorbed by the friction and other prejudicial resist- 
 ances of the mechanism, and which thus wastes energy 
 which might otherwise be usefully applied. These two 
 quantities, together, constitute the Total Work or the 
 Gross Work of a machine, or of a train of mechanism. 
 In every case some energy is wasted, and the work done 
 by the machine is by that amount less than the work 
 performed in driving it. In badly proportioned ma- 
 chines the lost work is often partly expended in the 
 deformation and destruction of the members of the 
 construction ; in well-designed and properly worked 
 machinery loss occurs wholly through friction. In ma- 
 chines acting upon fluids this work is usually partly 
 wasted in the production of fluid friction — i.e., of cur- 
 rents and eddies ; thus producing new forms of actual 
 energy in ways which are not advantageous : even this 
 waste energy is finally converted, like the preceding 
 form, by molecular friction, into heat, and is dissipated 
 in that form of molecular energy. Thuc all wasted 
 work is lost by conversion from the energy of mass- 
 motion into molecular energy, and ultimately disappears 
 as heat. 
 
 The Efficiency of Mechanism is measured by the quan- 
 tity obtained by dividing the amount of useful work 
 performed, by the gross w^ork of the piece or of the sys- 
 tem. It is always, therefore, a fraction, and is less than 
 unity ; which latter quantity constitutes a limit which 
 may be approached more and more nearly as the wastes 
 of energy and work are reduced, but can never be quite 
 reached. If the mean useful resistance be R, and the 
 space through which it is overcome be s , and if the 
 mean effort driving the machine be P, and the space 
 through which it acts be s, the total and the net or use- 
 
ENERGY AND ITS TRANSFORMATIONS. 23 
 
 //// ivork will be, respectively, Ps^ Rs'\ the lost work 
 will be Pt — Rs\ and the 
 
 Efficiency = -p- < i (20) 
 
 Counter-efficiency J C, is the reciprocal of the effiency ; 
 i.e., 
 
 Ps 
 
 ^=w (-) 
 
 The efficiency and the counter-efficiency of a machine, 
 or of any train of mechanism, are the products of the 
 efficiencies or of the counter-efficiencies of the several 
 elements constituting the train transmitting energy 
 from the point at which it is received to that at which 
 the work is done, i.e., from the " driving " to the 
 '' working " point. 
 
 Friction is the principal cause, and usually the only 
 cause, of loss of energy and waste of work in machinery. 
 A given amount of energy being expended upon the 
 driving-point in any machine, that amount will, in ac- 
 cordance with the principle of the persistence of energy, 
 be transmitted from piece to piece, from element to 
 element, of the machine or train of mechanism, without 
 diminution, if no permanent distortion takes place and 
 no friction occurs between the several elements of the 
 train, or between those parts and the frame or adjacent 
 objects. Temporary distortion, within the limit of 
 perfect elasticity, causes no waste of energy ; permanent 
 distortion, however, causes a loss of energy equal to 
 the total work performed in producing it. But perma- 
 nent distortion is due to deficiency of strength and de- 
 fective elasticity, and is never permitted in well-designed 
 
24 THE ANIMAL AS A MACHINE. 
 
 machinery properly operated ; and hence the important 
 principle : 
 
 In engineering, the principles of pure mechanism, of 
 theoretical mechanics, and pure theory in the science 
 of energetics, or of thermodynamics, are to be studied 
 as introductory to a science of apphcation in which all 
 actions and all calculations are to be considered with 
 reference to the modifications produced by the wastes 
 of energy and the alteration of the magnitudes and 
 other properties of forces consequent upon the occur- 
 rence of friction. 
 
 7. The Laws of Energetics, the basis of the science 
 which it has been proposed to call by that name, are : 
 
 (i) T'Jie Law of Persistence, or of Conservation of 
 Energy : — Existing energy can never be annihilated ; 
 and the total energy, actual and potential, of any iso- 
 lated system can never change. 
 
 This is evidently a corollary of that grander law, 
 asserting the indestructibility of all the work of creation, 
 which has already been enunciated. 
 
 (2) The Law of Dissipation, or of Degradation of 
 Energy : — All energy tends to diffuse itself through- 
 out space, with a continual loss of intensity, with what 
 seems, now, to be the inevitable result of complete and 
 uniform dispersion throughout the universe, and, con- 
 sequently, entire loss of availability. 
 
 It is only by differences in the intensity of energy, 
 and the consequent tendency to forcible dispersion, 
 that it is possible to make it available in the production 
 of work. 
 
 (3) The Law of Transformation of Energy : — Energy 
 may be transformed from one condition to another, 
 or from any one kind or state to any other ; changing 
 
ENERGY AND ITS TRANSFORMATIONS. 2$ 
 
 from mass-energy to molecular energy of any kind, or 
 from one form of molecular energy to another, with a 
 definite quantivalence. 
 
 These laws lead to the conclusion that, in any iso- 
 lated system of bodies, or in any isolated mass, the 
 total of all energy present is always the same ; though 
 it may be transformed in various ways, and to an ex- 
 tent only limited by the special conditions affecting the 
 system. They lead to the conclusion that energy of 
 higher intensity than the mean must occupy a limited 
 space, and will continually tend to dissipate itself by 
 dissemination through a greater volume, affecting 
 larger and larger quanties of matter, with proportional 
 reduction of intensity, until the whole system is occu- 
 pied by the originally existing energy, at a finally uni- 
 form and minimum intensity. Energy confined within 
 a limited space thus continually tends to expand, and 
 to break through its boundaries, and, if not freed from 
 this constraint, it produces a pressure upon the sur- 
 rounding surfaces, which, e.g., is exhibited as tension 
 of enclosed vapors and gases. Freed from confine- 
 ment, it tends to indefinitely expand. 
 
 Either form of energy may produce either other form 
 under suitable conditions. 
 
 Rankine's statement of the *' General Law of the 
 Transformation of Energy " is as follows : * 
 
 *' The effect of the whole actual energy present in a 
 substance, in causing transformation of energy, is the 
 sum of the effects of all its parts." 
 
 The axiom, as Rankine calls it, that '' any kind of 
 energy may be made the means of performing any kind 
 
 *Proc, Phil. Soc. of Glasgow ; vol. in. No. 5 ; 1S53. 
 
26 THE ANIMAL AS A MACHINE. 
 
 of work " is derived by '' induction from experiment 
 and observation," and confirmed by all experience. 
 
 TJie Sources of Enej-gy are : (i) Potential : {a) fuel ; {h) 
 food ; {c) head of water ; id) chemical forces. (2) 
 Actual : {a) air in motion ; {b) gravity in waterfalls ; (<:) 
 tides. 
 
 8. "Newton's Laws " follow directly from the gen- 
 eral law of persistence of energy, a corollary to which 
 may be stated thus : Change of energy can only be pro- 
 duced by the action of force, and by doing work. 
 Newton s Laws are : 
 
 (i) A free body tends to continue in the state in 
 which it, at any instant, exists, either of rest or of uni- 
 form rectilinear motion. 
 
 (2) All change of motion in a body free to move is 
 proportional to the force impressed, and is in the direc- 
 tion of that force. 
 
 (3) The reaction of the body acted upon by the im- 
 pressed force is equal, and directly opposed, to that 
 force. 
 
 Inertia is that property, observed in all bodies, in 
 consequence of the existence of which they are capable 
 of exhibiting the action of these laws. The laws of 
 Newton themselves are all easily verified by experiment. 
 The "Atwood Machine," illustrated in nearly all works 
 on physics, is constructed for this special purpose. 
 
 While Newton's laws are readily verified by experi- 
 ment, the more general laws of energetics are accepted 
 simply as being in accordance with universal experience. 
 The generally accepted theory of the constitution of 
 matter being assumed as a premise, however, the 
 general laws of energy are all easily deducible from 
 Newton's laws. Thus, the first law is but a differ- 
 
ENERGY AND ITS TRANSFORMATIONS. 2y 
 
 ently worded statement of Newton's three laws com- 
 bined. 
 
 To assert that every moving body tends to persist in 
 its rate of motion, exerting an effort always equal to 
 the retarding or accelerating force, and exerting such 
 effort in the line of action of such force, is to assert 
 that its energy can only be altered by the performance 
 of an equivalent amount of work, and an equal amount 
 of energy of opposite sign ; and this latter assertion is a 
 declaration of the indestructibility of energy. To assert 
 that all bodies, whether masses or molecules, when in 
 motion tend to move in rectihnear paths, is to assert a 
 tendency to unlimited dissipation of energy through 
 space. To assert that all matter in motion is subject to 
 Newton's laws is to assert the laws of universal conserva- 
 tion of energy, and of the quantivalence of all transforma- 
 tions, as stated in the third general law. Whenever it 
 becomes established that any phenomenon, as the trans- 
 fer of heat, of light, of electricity, or of sound, is a mode 
 of motion affecting bodies of whatever class, Newton's 
 laws bring that phenomenon within the scope of the 
 general laws of energy. Every phenomenon, molecu- 
 lar or other, which involves relative motion of masses, 
 vibrations of parts, or pulsations in fluid media, is now 
 well understood to be subject to these laws. 
 
 9. Algebraic Expressions of the transformability 
 of the energies are now readily deduced. If in any 
 isolated system a certain quantity of energy exists, 
 homogeneous in character and heterogeneously dis- 
 tributed ; and if, by any process, other and various 
 forms of energy appear in that system, these latter 
 must be the result of transformations of parts of the 
 initial stock of energy by conversion into the new 
 
28 THE ANIMAL AS A MACHINE. 
 
 forms. But every such change must be effected by a 
 perfectly definite and exact quantivalence. 
 
 Assuming this ratio of values of customary units 
 reduced to a system of equivalents, it becomes at once 
 practicable to measure all these energies in the same 
 units ; as, for example, when Joule measures either 
 heat or mechanical energy, taking y = 778 foot-pounds, 
 as the equivalent of a British thermal unit, ox J = about 
 427 kilograrnmetrcs, as the equivalent of one calorie or 
 metric thermal unit ; the thermal unit being defined as 
 the quantity of heat or energy-equivalent demanded to 
 raise the temperature of unit weight of water one 
 degree from the temperature of maximum density. 
 
 Taking either kind of unit in thus measuring, we 
 shall have the initial stock of the one kind of energy 
 altered by the quantity which, in the same units, 
 measures the aggregate several quantities of energy 
 resulting from the change ; and 
 
 where E, T, U, V, etc., are the symbols representing 
 the several energies, initial and other. 
 
 If T measure heat-energy, and U be taken as poten- 
 tial energy of the molecular kind, V the potential 
 energy of an elastic fluid varying in volume, W the 
 work of some mechanism or a dynamic process, the 
 total variation of the initial energy E, will be equal 
 to the total of all the new energies and the new work, 
 in proportions which become known as soon as the 
 
 dE 
 partial coefficients -—, etc., are determined. 
 
ENERGY AND ITS TRANSFORMATIONS. 29 
 
 If two energies only, as thermal and mechanical, are 
 affected, and if the original stock were simply heat- 
 energy, we should have a change, dE^ in the initial 
 stock of heat-energy, which would be the precise 
 equivalent of the sum of the two changes taking place, 
 simultaneously, in the initial store and in the tempera- 
 ture, T, of the system, and in work by the change of 
 volume, F, against a pressure of, say, the intensity/. 
 Then, obviously, 
 
 dE dE 
 
 and, since [-77^ measures the specific heat, K^, for 
 
 constant volume, and as (-ttv) must measure the in- 
 
 \dVJ T 
 
 tensity of pressure producing, or resisting, the change 
 of volume, 
 
 dE = KJT^pdV. (2) 
 
 If but one kind of transformation occurs, as by con- 
 version of any original form of energy, E, into work, 
 a process illustrated in every purely thermodynamic, 
 thermo-electric, or electro-dynamic operation, 
 
 dE^pdV\ ox, dE^RdS. ... (3) 
 
 Whatever the method of transformation of actual 
 energy, it is simply a process of transfer of the energy 
 of motion from one kind of matter to another, or from 
 a mass to a collection of molecules, with, usually, modi- 
 fication of the mode of motion, as from rectilinear to 
 vibratory, or from motion in an orbit of one form to 
 m.ovement in a path of different character. 
 
30 THE ANIMAL AS A MACHINE, 
 
 10. The Object of all Mechanism is to produce 
 a certain definite motion of some part or parts — the 
 position and form and the methods of connection of 
 which are known and fixed — against any resistance 
 that may be met with in the course of such movement. 
 Every machine and every train of mechanism is there- 
 fore a contrivance by means of which energy or power 
 available at one point, usually in definite amount and 
 acting in a definite direction and with definite velocity, 
 is transferred to other points, there to do work of 
 definite amount, and there to overcome known resist- 
 ances with known velocities. 
 
 The object of the engineer in designing mechanism 
 is to effect this transfer of energy and these trans- 
 formations at the least cost and with least " running 
 expense," and hence with maximum efificiency of 
 apparatus. It is often important to secure minimum 
 volume and weight of machine, as well as maximum 
 effectiveness in operation. 
 
 The work of a machine is measured by the magnitude 
 of the resistance encountered and the velocity with 
 which it is overcome. The nature of the work, aside 
 from its simple kinetic character, is as widely variable 
 as are the details of human industry. 
 
 Prime Movers are those machines which receive 
 energy directly from natural sources, and transmit it 
 to other machines which are fitted for doing the various 
 kinds of useful work. Thus, the steam-engine derives 
 its power from the heat-energy liberated by the com- 
 bustion of fuel ; water-wheels utilize the energy of 
 flowing streams ; windmills render available the power 
 of currents of air ; the voltaic battery develops the 
 energy of chemical action in its cells ; and, through 
 
ENERGY AND ITS TRANSFORMATIONS. 3 1 
 
 the movement of electro-dynamic mechanism, this 
 energy is communicated to other machinery, and thus 
 caused to do work. 
 
 ]\IacJiincry of Transmission is used in the trans- 
 formation of energy supphed by the prime mover into 
 available form, for the performance of special kinds of 
 work, or for simple transmission of power from the 
 prime mover to machines doing that work. 
 
 II. The Sources of Energy, applied by man, 
 through the prime movers, to the economic purposes of 
 life, are six in number : 
 
 (i) The potential energy of fuel, coming of the stor- 
 age, in early geological periods, of the actual energy of 
 the heat, light, and chemical forces of the sun's rays, 
 and the energy of the dispersing internal heat of the 
 earth, gathered up by the vegetation, and, in case of 
 the mineral oils, possibly, by the animal life, of those 
 primitive ages, reduced to this potential form and stored 
 in the depths of the earth for use in modern times. 
 Very possibly a still earlier history of this energy 
 may be traced in the gradual transformation of the 
 potential dynamic energy of a chaotic universe, in- 
 finitely dispersed, into the heat-energy of collision of 
 particle with particle, and of globe with globe, as the 
 existing systems of worlds took form. The potential 
 energy of fuel is converted by combustion into active 
 form. 
 
 (2) The dynamic, the kinetic, energy of falling water, 
 transferred through water-wheels without transforma- 
 tion, to do useful work. 
 
 This has a similar origin to the preceding ; the water 
 being raised from the seas, lakes, and streams to the 
 clouds by the action of the heat of the sun, thus carried 
 
32 THE ANIMAL AS A MACHINE. 
 
 to the higher portions of the land, again to return in 
 the streams to the sea-level. 
 
 (3) The kinetic energy of the air-currents, as utilized 
 by windmills, which convert it to useful purposes pre- 
 cisely as the water-wheel intercepts the energy of fall- 
 ing water with a similar end. 
 
 The primary source of this energy is again the heat 
 of the sun, which produces a convection of air-cur- 
 rents similar dynamically, in method and result, to 
 those of water in the ocean or over or on the land. 
 
 (4) The energy of the tides, the rise and fall of which 
 constitute a source of power less easy of utilization 
 than that of streams, and for this reason, rarely applied 
 to the production of power. 
 
 The origin of this energy is in the force of gravita- 
 tion as it acts upon the ocean, changing its level through 
 the attractions of the sun and the moon. This is seen 
 to be essentially different from the other cases. 
 
 (5) The energy of electricity, originally exhibited 
 either in the form of molecular energy resulting from 
 chemical action, or produced by transformation directly 
 from the dynamic form. In this latter case, the ma- 
 chine transforming it is an intermediate or a secondary, 
 instead of a prime, motor. In the former case the 
 origin is potential, in the latter kinetic. 
 
 (6) The energy of muscular action, the power of ani- 
 mals, derived from the chemical forces acting in the 
 production of vegetation and transformed for use in the 
 animal system, through either thermo-electric or thermo- 
 dynamic processes, or perhaps through the action of 
 both, each having its appropriate task. 
 
 In the animal system, the vegetable matter employed 
 as food is converted by the natural forces of digestion 
 
ENERGY AND ITS TRANSFORMATIONS. 33 
 
 and nutrition into available form for use by the nervous 
 and muscular systems of the body, by means of inter- 
 mediate processes which are as yet obscure. It is only 
 certain that they cannot all be thermodynamic pro- 
 cesses ; it seems probable that they are, in some cases, 
 at least, related to the electrical methods of transforma- 
 tion. In some instances, as in the carnivora, the final 
 conversion results from a double transformation. 
 
 Thus substantially all utilized natural energy is de- 
 rived, directly or indirectly, from the sun. 
 
 According to Sir William Thomson, '' the mechanical 
 value of a cubic mile of sunlight is 12,050 foot-pounds, 
 equivalent to the work of one horse-power for a third 
 of a minute. This result may give some idea of the 
 actual amount of mechanical energy of the luminiferous 
 motions and forces within our own atmosphere. 
 Merely to commence the illumination of three cubic 
 miles requires an amount of work equal to that of a 
 horse-power for a minute ; the same amount of energy 
 exists in that space as long as Hght continues to traverse 
 it ; and, if the source of light be suddenly stopped, 
 must be emitted from it before the illumination 
 ceases." * 
 
 The same authority says : " Taking the estimate 
 2781 thermal units centigrade, or 3,869,000 foot-pounds, 
 
 *The mechanical value of sunlight in any space near the sun's sur- 
 face must be greater than in an equal space at the earth's distance, in 
 the ratio of the square of the earth's distance to the square of the sun's 
 radius, that is, in the ratio of 46,400 to i, nearly. The mechanical 
 value of a cubic foot of sunlight near the sun must, therefore, be about 
 ,0038 of a foot-pound, and that of a cubic mile 560,000,000 foot-pounds. 
 Similarly we find 15,000 horse-power for a minute as the amount of 
 work required to generate the energy existing in a cubic mile of light 
 near the sun. — Thomson. 
 
34 THE ANIMAL AS A MACHINE. 
 
 as the rate per second of emission of energy from a square 
 foot of the sun's surface, equivalent to 7000 horse- 
 power,* we find that more than 0.42 of a pound of coal 
 per second, or 1500 lbs. per hour, would be required 
 to produce heat at the same rate. Now if all the fires 
 of the whole Baltic fleet were heaped up and kept in 
 full combustion over one or two square yards of surface, 
 and if the surface of the globe all round had every square 
 yard so occupied, where could a sufficient supply of air 
 come from to sustain the combustion ? — yet such is the 
 condition we must suppose the sun to be in, according 
 to the hypothesis now under consideration, at least if 
 one of the combining elements be oxygen or any other 
 gas drawn from the surrounding atmosphere." 
 
 12. The Forms of Motor, the special machines 
 through which these transfers and transformations are 
 effected, are the following : 
 
 (i) The animal body is a vital machine, of extra- 
 ordinary complexity, self-constructing and self-repair- 
 ing, and is automatic in its many and usually mysterious 
 internal processes. 
 
 This machine is directed by conscious intelligence 
 and will, and, when usefully applied to the production 
 of work, is guided by the mysterious action of the mind. 
 It effects conversions of energy through the processes 
 of chemical action peculiar to the animal system. 
 
 (2) TJie heat-engines, including steam-, air-, gas-, and 
 vapor-engines of various less familiar kinds. 
 
 In these machines, the potential energy of fuel is, by 
 combustion, converted into the active form, and stored 
 
 * This is sixty-seven times the rate at which energy is emitted from 
 the incandescent electric lamp at the temperature which gives 240 
 candles per horse-power. 
 
ENERGY AND ITS TRANSFORMATIONS. 35 
 
 in a gaseous or vaporous fluid, the variations of tem- 
 perature, pressure, and volume of which result in the 
 production, more or less efficiently, of mechanical power 
 in readily applicable form. 
 
 The heat-engines do by far the greater part of the 
 work of the world, and the steam-engine the main por- 
 tion of that performed by thermodynamic operations. 
 
 Solar engines, so-called, are heat-engines in which the 
 direct heat energy of the sun, instead of the stored heat 
 energy of a combustible, is utilized through the action of 
 a working fluid, as with other forms of machine of this 
 class. 
 
 (3) The zvafer-wheels, including the various classes of 
 so-called vertical wheels, and the turbines ; in which 
 latter, the water, instead of entering *' buckets," to be 
 again poured out of them, passes continuously through 
 channels, without reversal of motion. 
 
 These machines effect no transformations of energy ; 
 but simply turn it out of its natural course into an arti- 
 ficial channel of application. It is kinetic, as found, 
 and remains kinetic until transformed in the course of 
 its application to its intended purpose. 
 
 (4) Tidal viacJiines are simply floats, rising and fall- 
 ing with the tides ; or they are vertical water-wheels, 
 working in tidal currents in precisely the same manner 
 as those operated by ordinary running streams. They 
 transfer, but do not transform, energy. 
 
 (5) Windmills are pneumatic turbines, especially 
 fitted to take up the energy of moving air, and to transfer 
 it, without transformation, to machinery of transmission, 
 through which it is conveyed to its point of application. 
 
 (6) Electrical engines, electro-dynamic machines, 
 dynamos and motors, as they are variously called, are 
 
36 THE ANIMAL AS A MACHINE. 
 
 apparatus for transformation, converting the molecular 
 energy of electricity into the mechanical form in such 
 manner as permits its useful employment. 
 
 These machines, reversed, change the energy of me- 
 chanical power into the electrical form, and both direc- 
 tions of transformation in well-designed machinery 
 result in a very efficient conversion of energy. As a 
 rule, it is found much more satisfactory to derive the 
 energy, initially, from a prime mover, by conversion 
 into the electrical form, than to obtain it directly from 
 the voltaic battery. Water-power or the combustion 
 of fuel is vastly less costly than the combustion of zinc 
 and the saturation of acids with its salts. 
 
 The purpose of this discussion is to describe, briefly 
 and exactly, the characteristics of the animals as motors, 
 to describe their methods of action and their sources of 
 gain and loss of energy, and to present the principles 
 of energy-production and transformation illustrated by 
 them. 
 
11. 
 
 THE ANIMAL AS A MACHINE AND A PRIME 
 MOTOR. 
 
 13. The Animal as a Machine. — The engineer re- 
 gards the animal system with peculiar interest, as a 
 machine of singularly complicated structure, a heat- 
 engine or other prime motor — he is not certain as to 
 its classification — of extraordinary efficiency, and as 
 the embodiment of scientific problems of the highest 
 interest and greatest obscurity. In this curious ma- 
 chine, combustible matter in the form of the grains or 
 other foods, is consumed, with resultant production of 
 carbon dioxide and other chemical compounds of 
 various degrees of oxidation, and there is thus made 
 available thermal, mechanical, and probably electrical 
 as well as vital energies, all of which energies find 
 application in the processes of animal life, in the per- 
 formance of work, external and internal, and probably 
 in mental operations as well. Waste also occurs in 
 the form of heat and the rejected potential energy of 
 incomplete chemical action. 
 
 Considering the automatic system of the animal, 
 apart from intelligence and will, it is, in the eye of the 
 engineer, a self-contained prime mover, includifig its 
 furnace, its mechanism of work and energy-develop- 
 ment, and possessing mechanism of transmission of 
 power peculiarly and exactly adapted to its purposes. 
 
 37 
 
38 THE ANIMAL ASA MACHINE. 
 
 14. The Animal as a Prime Motor.* — Hirn was 
 probably the first and the greatest of those who have 
 sought to measure up the energies of hving creatures, 
 and to follow the transformations which occur in the 
 processes of vital organization and animal exertion. f 
 
 The origin of heat in the bodies of living animals has 
 been a matter awakening the greatest interest and 
 curiosity from the earliest times. The ancients thought 
 heat and light a part of the vital power, due to the 
 creative act, and without immediate source in the 
 processes of vital existence. They thought the 
 act of breathing a necessary process of cooling and 
 removal of excess of this spontaneously generated 
 heat, due to the fact of life simply. Since the estab- 
 lishment of the principles of energy in modern times, 
 however, the philosopher has only concerned himself 
 as to the method of production of this heat, recogniz- 
 ing the fact that it must have its origin, as must all the 
 exhibitions and expenditures of energy that accompany 
 it in the living being, from the potential and latent 
 energies of combustible substances subjected to the 
 processes of digestion and assimilation in the body. 
 The scientific man of later times sees in the vital pro- 
 cesses a transformation of energies originating in a 
 slow combustion at low temperature, with changes of 
 form of the resulting energies which, though none the 
 less certainly phases of the chain of vital phenomena 
 which he studies, are not all fully understood, or as 
 yet all detected and rendered evident by research. 
 The chemical compositions of these combustibles are 
 
 * From Cassier's Magazine, Feb., 1892; by R. H. Thurston. 
 \ La Thermodynamique et I'Etude du Travail chez les Etres vivants. 
 G. A. Hirn, Paris. Bureaux des Revues, 1887. 
 
THE ANIMAL AS A MOTOR, 39 
 
 known ; the quantities of energy which may be ob- 
 tained by their perfect combustion to carbonic acid 
 and water are well ascertained, and it only remains to 
 determine the exact nature of the processes by which 
 it is possible to effect their combustion at the tempera- 
 ture of the animal system, and to utilize by transform- 
 ation the resulting power through those intermediate 
 forms of energy-change which remain as yet undis- 
 covered, and, in that sense, mysterious. We do not 
 yet know how to produce combustion at a temperature 
 of 98° Fahr., that at which combustion certainly does 
 occur in the human system ; or at the still lower tem- 
 peratures at which such chemical changes go on in the 
 bodies of cold-blooded creatures ; nor do we know how 
 to secure transformation of heat into mechanical and 
 other forms of energy without sensible change of tem- 
 perature and with high efficiency. In all our uses of 
 heat-engines the wastes are a much greater proportion 
 of the available energy than in any animal system, 
 except where, as in some cases of application of the 
 heat-energy of steam, for example, the wastes of the 
 engine are, as in the human body, utilized for heating 
 purposes. 
 
 The muscles when doing work, and all the glands, 
 every organ, in fact, while performing its legitimate 
 function, is found to become warmer ; indicating the 
 final appearance of whatever .form of energy may be 
 operating in the system in the form of heat. Heat is 
 produced, apparently, in all the organs of the body, but 
 in different degree, accordingly as their action is intense 
 or deliberate. Those veins which return blood from 
 working organs bring it back slightly warmer than the 
 average for the whole system ; those coming in toward 
 
40 THE ANIMAL AS A MACHINE. 
 
 the heart from the skin bring back colder blood from 
 that constantly refrigerated system of capillaries. The 
 mean temperature of the venous blood entering the 
 heart is about one degree warmer, in man, than the aver- 
 age for the whole system ; between one and two de- 
 grees warmer than the arterial blood. The tempera- 
 ture of the body, as a whole, is automatically regulated 
 by the system of nerves studied by Bernard ; which 
 causes the flow of blood toward any part to be accel- 
 erated when that part is cold, and retarded when it is 
 too warm. 
 
 In every mechanism endowed with animal life, heat 
 is produced and work is performed. It by no means 
 follows that the work is the result of thermodynamic 
 transformation ; in fact, it seems impossible, in view of 
 the fact that we have in the animal system no differ- 
 ences of temperature such as characterize and limit the 
 action of the thermodynamic engine, that there should 
 be a thermodynamic transformation. The heat would 
 seem to be either a "by-product" or to be produced 
 simply to insure uniform and sufficient temperature to 
 permit the continuous and steady action of the vital 
 powers and the machinery of the body. All the ali- 
 mentary substances are combustible ; but it is not a 
 necessary consequence that they should be oxidized by 
 a heat-producing combustion within the animal system. 
 On the contrary, the quantity of heat which would be 
 thus produced, added to the quantity of work per- 
 formed by the vital organs, in digestion, nutrition, cir- 
 culation of the blood, — itself an enormous quantity, — 
 though reproducing the energy thus expended, as heat, 
 and thus, in one sense, costing nothing — and in brain- 
 work, to say nothing of wastes by conduction and 
 
THE ANIMAL AS A MOTOR. 4 1 
 
 radiation to surrounding objects, the total amount of 
 heat produced by such combustion would vastly ex- 
 ceed the quantity discharged from the body in any 
 given time. This discrepancy is greater in cold-blooded 
 animals than in warm-blooded ; and, in many in- 
 stances, the heat given out is probably too small in 
 amount to account for combustion of any important 
 fraction of the aliment of the system. The animal ma- 
 chine is not thermodynamic in the usual acceptation of 
 that term, even if it be in any sense. 
 
 Mon. J. Beclard was probably the first to attempt to 
 measure the relation of quantity and of transformation, 
 thermodynamically, if such energy-transformations 
 actually occur, in the animal machine. But he reached 
 no definite result. Herdenheim suceeded little better; 
 but Hirn found ways of investigation which gave real 
 quantitative results of importance. A certain corre- 
 spondence was found between work performed and 
 heat exhaled ; but nothing in his experiments gave in- 
 dications of the method of production of that heat ; and 
 it is still impossible to say whether the heat is the direct 
 product of oxidation of food, the result of oxidation of 
 worn muscular and other tissue, or due to a number of 
 thermal and other interactions occurring within the 
 body and as yet beyond the reach of scientific observa- 
 tion. The disappearance of heat unquestionably estab- 
 lished by Hirn's researches may or may not have been 
 due to thermodynamic transformations. Whatever 
 form of energy-transformation characterizes the vital 
 machine, the wastes of energy take the final form of 
 heat, and its quantity would, in any case, be reduced by 
 the production of mechanical energy and the perform- 
 ance of work within and without the body. 
 
42 THE ANIMAL AS A MACHINE. 
 
 In 1856-57 Hirn experimented with men engaged in 
 regular work and at rest, and found that when at rest 
 they produced a quantity of heat almost exactly, if not 
 precisely, proportional to the amount of oxidation, as 
 measured by the quantity of oxygen absorbed by them 
 and exhaled in carbonic acid. 
 
 This was not precisely the case when they were at 
 work. The principle of equivalence of energies then 
 takes effect, and the measure of all the energy pro- 
 duced by oxidation is found in the sum of the heat 
 discharged from the system and that energy of work 
 which stands for the parts converted into dynamic 
 forms. ^ 
 
 Hirn found that the quantity of heat generated by 
 the human body at rest, whether that of men of mid- 
 dle age, or youth of either sex approaching maturity, 
 was substantially the same under the same circum- 
 stances : about 5 calories per gramme of oxygen in- 
 spired and exhaled as a minimum, 5.2 as a maximum, 
 and usually the latter figure. The differences may be 
 ascribed to variations in observations, rather than to 
 real differences of fact. Precisely the same quantities 
 of air were measured as exhaled as were measured as 
 inhaled, in all cases. A singular and significant fact 
 was, however, discoverable in the results, as reported 
 by Hirn : The quantity of heat produced per unit of 
 oxygen absorbed and converted into compounds ex- 
 ceeds by a third the amount computed upon the basis 
 of the experiments of Favre and Silbermann. This 
 result would seem to indicate other sources of heat 
 than combustion with oxygen. It may be due to 
 
 * L'Equivalent mecanique de la Chaleur. G. A. Hirn, 1858. 
 
THE ANIMAL AS A MOTOR. 43 
 
 oxygen absorbed and exhaled through the skin ; to the 
 conversion of stored energies as yet undetected in the 
 system ; or to the combination of other elements, as 
 carbon and hydrogen, through processes resulting in 
 the production of heat."^ It is to the latter cause that 
 Hirn would ascribe this excess of exhaled energy. 
 This subject remains still to be investigated. 
 
 The same individuals being set at hard work in a 
 treadmill constructed for the purpose, in such manner 
 as give the figures for a normal condition of labor, 
 unforced but steady, and at a maximum for a day's 
 work, gave out but about one half as much heat per 
 unit of air breathed and of oxygen consumed, showing 
 clearly the transformation of heat into work. The 
 efficiencies of the human system, considered as a heat- 
 motor or -engine, ranged, according to the condition 
 and temperament of the subject of the test, from 17 
 per cent to 25 per cent when raising the load or them- 
 selves ascending, and rose to 30 and 40 per cent in 
 descent. A lymphatic youth of 18 gave the lowest 
 figures ; a strong man of 47 the highest. These results 
 all exceed those obtainable as yet from the most eco- 
 nomical forms of existing gas- or steam-engine, in 
 which 20 per cent may be taken as about the con- 
 temporary limit of their efficiency as heat-engines. 
 
 To fully secure this efficiency in the human body as a 
 heat-engine subjected to the accepted laws of thermo- 
 dynamics would demand a temperature within its 
 working parts not far from 140 Cent. (284° Fahr.), or 
 far above the boiling-point of water. This fact is 
 crucial as a proof that the transformations of energy 
 
 * SeeSarason : Revue Scientifique, 1SS7, page 306 et seq. 
 
44 THE ANIMAL AS A MACHINE. 
 
 in the animal system are not, in the accepted sense, 
 thermo-dynamic. They must involve as yet unknown 
 processes and methods, and must be free from the 
 control of thermodynamic principles, as we are accus- 
 tomed to denominate them. The ''second law of 
 thermo-dynamics " is here evaded. 
 
 In those cases in which work was done, the produc- 
 duction of heat was as much less than that anticipated, 
 as computed from the engineers' and the physicists* 
 experiments, as, in the case of rest, that figure was 
 exceeded, falling in the latter case to from 2.5 calories 
 to 3.5 per gramme, varying with the individual and his 
 familiarity with the work, and consequent efficiency as 
 a machine. 
 
 Thus the investigator shows that while the animal 
 system is unquestionably a machine producing and 
 utilizing energy by transformation, it possesses some 
 peculiarities and conceals some secrets that science 
 has still to discover through exact methods of research. 
 It further has become evident that these methods of 
 production and utilization of energy include some 
 which are very different from those familiar to us, as 
 exhibited in our inanimate heat-engines, and which, 
 once discovered and given application, should that 
 prove practicable in artificial machines of this class, 
 will probably prove enormously advantageous in the 
 saving of costly energies now so largely wasted. Could 
 we discover and apply these methods in displacing our 
 heat-engines, it would give us direct transformations of 
 energy into work at low temperatures, with little or no 
 wastes, and thus enormously extend the period of 
 human life on this globe, as well as its productiveness. 
 It will be an interesting question for the electrician 
 
THE ANIMAL AS A MOTOR. 45 
 
 and the engineer to settle : whether these as yet 
 mysterious processes are not electro-dynamic or related 
 phenomena. 
 
 15. The Processes of the Vital Machines em- 
 ployed in the development of power result mysteri- 
 ously in the production of heat, light, electricity, and 
 dynamic energy by methods still unknown, and with 
 an efficiency of development, transformation, and 
 application frequently, if not always, much greater 
 than has been yet attained by any of the machines 
 devised by man to effect similar results. Mechanical 
 power is exerted at less cost in potential energy sup- 
 plied than in the steam-engine ; heat is evolved as the 
 product of combustion or other action at a low tem- 
 perature, and with insignificant waste by non-utilization 
 in the processes of the animal economy ; light is pro- 
 duced by glow-worms and fire-flies without sensible 
 loss in accompanying thermal or other energy ; and 
 electricity, probably the motor energy of the machine, 
 is produced with similar wonderful economy by pro- 
 cesses of which we have no knowledge. Combustion 
 at ordinary low temperatures, in the tissues of the 
 body; chemical combinations of other kinds in the 
 digestive organs, by the action of peptic substances in 
 solution in the fluids of the system, and other pro- 
 cesses unknown, as yet : these evade the inevitable 
 losses of thermo-dynamic operations in the vital 
 machine, and effect results which are never economi- 
 cally obtainable by the machines of the inventor and 
 mechanic. These constitute a standing riddle and 
 challenge to the man of science and the engineer. 
 
 Lavoisier, as early as 1789, asserted that animals are 
 composed of combustible substances, and that their life 
 
46 THE ANIMAL AS A MACHINE. 
 
 is based upon chemical action involving the slow com- 
 bustion of the carbon and hydrogen of their food and 
 muscle ; respiration furnishing the needed oxygen — an 
 element discovered by him three years earlier. Rum- 
 ford, in 1797, stated that animals, considered as ma- 
 chines, were efficient prime motors, and in 1799 pub- 
 lished his discovery of the identity of heat with mechani- 
 cal energy and his approximation to the value of the 
 mechanical equivalent ; and Scoresby and Joule, and 
 especially Hirn, later completely confirmed his views 
 on these points.* 
 
 Modern research shows that the evolution of heat 
 is at least an invariable accompaniment of all action of 
 the animal system — also even of the brain and spinal 
 cord. Thought and manual labor, in the case of the 
 human machine, are alike productive of increased tem- 
 perature and of accelerated exhalation of carbon diox- 
 ide from the lungs and of salts from other organs. 
 Whether these chemical actions are direct results or 
 simply incidental to intermediate transformations of 
 matter and energy is as yet not fully determined. 
 The effect of exercise is invariably to increase greatly 
 the consumption of oxygen, and the elimination of 
 carbon dioxide, and the temperature of the body, within 
 narrow limits ; regulation being effected by exudation 
 of perspiration and its evaporation. Other effects of 
 increased exertion of the muscular system are the pro- 
 motion of digestion, the consumption of accumulated 
 combustible matter, as the fats, and increased rapidity 
 and thoroughness of blood circulation and of nutrition. 
 
 * On these points, see Seguin and Lavoisier (Premier Memoir), Rum- 
 ford's Essays, and Philosophical Magazine, 1846. 
 
THE ANIMAL AS A MOTOR. 47 
 
 which are the essentials to efficient action of the ma- 
 chine as a whole. The wonderful self-adjusting power of 
 the system makes these actions effective even locally ; 
 and the exercise of one member or part of the machine 
 produces increased circulation, increased degeneration, 
 and at the same time increased blood-supply and nutri- 
 tion of the part thus compelled to supply energy. 
 
 The muscular system constitutes about 40 per cent 
 of the weight of the body, and contains blood to the 
 amount of one third this weight, or 12 to 15 per cent 
 of the whole weight of the body. The wear of this 
 muscular tissue gives rise to a demand for the nitro- 
 genous foods to supply the waste, and thus produces 
 an appetite for lean meats or for vegetable foods rich 
 in gluten. The nervous tissue, the system of inter- 
 communication and transfer of energy from part to 
 part, is also subject to wear ; and this waste is supplied 
 by the phosphatic foods, as animal brain, marrow, nerve, 
 and glandular or other white meats, and as the fruits 
 and the grain-foods, the peculiar diet of the human and 
 especially of the brain-working creature. Overuse of 
 the muscles or of the nervous system reduces their 
 powers of recuperation, repair, and general nutrition ; 
 and it is for this reason that labor and exercise should 
 be carefully restricted within those limits marked by 
 the appearance of symptoms of exhaustion. Highest 
 efficiency of the animal, as of any other machine, can 
 be permanently maintained only when the conditions 
 of maximum perfection of parts and of operation are 
 ascertained and insured. The selection of proper foods 
 is as essential to the successful maintenance and use of 
 the animal machine as the securing of good fuel for use 
 in the heat-engines ; attention to diet and the adjust- 
 
48 THE ANIMAL AS A MACHINE. 
 
 ment of the periods of employment to best effect are 
 as important as the supply of the best coal and the 
 periodical stoppage and repair of the machinery in a 
 mill or factory. 
 
 The elimination of nitrogen and carbon dioxide is, in 
 some as yet uncertain way, a gauge of the quantity of 
 useful and lost work of the animal machine. Liebig 
 states in his Animal Chemistry (1843) that the excre- 
 tion of nitrogen is proportional to the destruction of 
 tissue, and Lehman states in his turn that he finds this 
 excretion increased by exercise. Fick and Wislicenus, 
 on the other hand, assert that the animal is a heat- 
 engine, and that the performance of work affects the 
 elimination of nitrogen shghtly, but increases that of 
 carbon dioxide enormously, and this view is confirmed 
 by Frankland and by Houghton ; while Dr. Parkes in- 
 directly gives similar testimony in the statement that 
 work is done by the consumption of other than nitroge- 
 nous foods, the elimination of nitrogen being due to 
 waste of tissue ; that of carbonic acid to combustion 
 resulting in thermodynamic action. Incidentally, 
 Liebig also confirms this idea by his statement that 
 the exhalation of nitrogen goes on long after work has 
 ceased."^ Dr. Pavy, on the other hand, found by ex- 
 periment on two well-known pedestrians that their 
 excessive exertion produced greatly increased elimi- 
 nation of nitrogen — apparently a consequence of the 
 breaking down of tissue. He concludes that the body 
 is a true heat-engine, but he finds it capable apparently 
 
 *See Frankland's Origin of Muscular Power; Houghton in the 
 Lancet, 1868 ; Parkes in the Medical Times, 1871 ; Flint on Muscular 
 Power, 1872 ; Pavy on Muscular Power, 1878. 
 
THE ANIMAL AS A MOTOR. 49 
 
 of performing more work than the food would seem 
 competent to do. In these cases it would seem very 
 possible that the observed excess may come of con- 
 sumption of tissue in addition to food ; the waste being 
 gradually repaired during a later period of prolonged 
 rest, with food-consumption above the normal rate. 
 
 Dr. Flint, who paid much attention to this subject, 
 concluded, as the result of the study of the working of the 
 muscular system of a celebrated pedestrian (Weston), 
 about 1870, during a walk of 318 miles in five days, 
 weighing all foods and excretions and noting their com- 
 position, that it is as yet impracticable to intelligently 
 compare the force-value of foods with the work of the 
 muscular system ; that such estimates, as now custom- 
 arily made, account only for a part of the work, even 
 leaving out of consideration the energy of other (vital 
 and nervous) actions ; that exercise always results in 
 waste of muscular tissues, which may not be repaired at 
 the time ; and he also beheves that the source of energy 
 is the wasted tissue, and, indirectly only, the nitrogen- 
 ized food which supplies the waste. 
 
 Dalton takes the production of heat in the body at 
 rest, per hour, as about 1.28 British heat-units per pound 
 of its weight. Houghton estimates the work done in 
 walking at one twentieth of the weight of the body in 
 pounds multiplied by the number of feet walked per 
 hour ; and it would seem possible, from Flint's compu- 
 tations, that about ten per cent of the total energy- 
 expenditure takes place in the brain and nervous sys- 
 tem in the case of man, although that author does not 
 so take it.* The processes involved in the operation 
 
 * Source of Muscular Power, pp. 100-103. 
 
50 THE ANIMAL AS A MACHINE. 
 
 of the animal mechanism, to say nothing of its mental 
 part, are too compHcated and obscure to permit at 
 present any very accurate statement of their nature, 
 methods, or results. 
 
 i6. The Efficiency of the Animal System, consid- 
 ered as a heat-engine — a probably incorrect assump- 
 tion — is very high as compared with the machines of that 
 class constructed by man. Helmholtz concluded from 
 the experiments of Hirn that the thermodynamic efifi- 
 ciency of the system is about 0.20, confirming Hirn's 
 own earlier deduction that it is more efficient than the 
 steam-engine as ordinarily constructed. The fact, how- 
 ever, that the body is sensibly uniform in temperature 
 throughout, and that the more work done the more 
 rapid the circulation, and the more certain this uni- 
 formity of temperature, seem to prove it impossible 
 that such thermodynamic processes are carried on in 
 the animal system as are familiar to us in our heat- 
 engines, in which the maximum possible efficiency is 
 proportional to Carnot's function — range of temperature 
 divided by maximum absolute temperature. Whatever 
 its. method of operation, therefore, the animal machine 
 evades Carnot's law, and must illustrate some as yet 
 undiscovered process of energy-transformation. 
 
 17. The Work of the Animal Machine is meas- 
 ured in ''horse-power" — a rate equivalent to 550 foot- 
 pounds per second, 33,000 per minute, 1,980,000 per 
 hour ; 75 kilogrammeters per second, 4500 per minute, 
 270,000 per hour, in British and metric measure respec- 
 tively ; the latter, however, being, as will be seen by 
 comparison, one seventieth less than the former. Its 
 measure may also be taken as a days work, which may 
 have widely different dynamic values in different cases. 
 
THE ANIMAL AS A MOTOR. $1 
 
 The horse, if of average weight and condition, should do 
 a day's work at the rate of about two thirds of a horse- 
 power unit, or 22,000 to 25,000 foot-pounds per minute 
 for the day. A powerful horse may give a full horse- 
 power, and any animal may do for a short time vastly 
 more than its average rate of work. A man rated at 
 from a sixth to a tenth horse-power can, for a minute or 
 two at a time, perform a full horse-power, or even more. 
 
 The daily work of the animal, at its best, depends 
 upon its exact accommodation to most favorable con. 
 ditions for the development of the best work of the 
 individual, and upon its size, natural strength, endur- 
 ance, and spirit. These qualities in turn are dependent 
 upon the breed, the state of health, and the general 
 condition of the animal, its food, its environment, the 
 weather, the climate, and the adaptation of its load to 
 its habits and training. While at work the main ele- 
 ments of most effective operation are the load and the 
 speed adopted, at the time, and its distribution, day by 
 day and hour by hour. At maximum load the animal 
 does minimum work ; at maximum speed it can carry 
 no load ; at some intermediate load and speed it gives 
 maximum work, and this maximum varies with the time 
 of working, day by day. It is higher for short, lower 
 for long, working-days. For continuous work it is 
 usually assumed that eight hours a day, at one third 
 maximum speed and under one third maximum load, 
 gives highest results ; but this is true only under most 
 favorable conditions, with animals capable of doing a 
 full day's work, day by day, continuously without loss 
 of strength. In many cases four hours, and sometimes 
 even one, constitute a fair day's work. 
 
 Animal power is most remarkably developed in the 
 
52 
 
 THE ANIMAL AS A MACHINE. 
 
 birds of fast or of long flight. A man can exert 0.25 
 horse-power for a few minutes at a time, 0.15 horse- 
 power by the hour — which, at 1 50 pounds weight of the 
 man, would require 600 to about 700 pounds per horse- 
 power. The horse weighs 1500 or 2000 pounds per 
 horse-power ; but the birds develop power at the rate of 
 probably less than one third those figures for the former, 
 and one eighth or one tenth for the latter. Falcons fly 
 60 miles an hour, pigeons 35 to 60 for hours together, 
 and the albatross accompanies fast steamers thousands 
 of miles without halt or rest. The birds weighing 
 probably lOO to 200 pounds per horse-power can carry 
 for a time an added load of 30 to 50 per cent, as when 
 the carnivorous birds carry away their prey. 
 
 According to M. Fourier, the daily work of a good 
 horse has a maximum, under the best load for each 
 speed, at about 0.90 (2.95 feet) meters per second, or 
 3200 (10.596 feet, 2 miles, nearly), an hour. Taking 
 this maximum as unity, he gives the following as prob- 
 able values of work per pound at other speeds : * 
 
 SPEED PER 
 
 HOUR. 
 
 DAILY WORK. 
 
 Metres. 
 
 Miles. 
 
 
 2,000 
 
 1.25 
 
 0.69 
 
 3,200 
 
 2.00 
 
 1. 00 
 
 4,000 
 
 2.50 
 
 •99 
 
 6,000 
 
 375 
 
 •94 
 
 8,000 
 
 5.00 
 
 .83 
 
 10,000 
 
 6.25 
 
 .68 
 
 12,000 
 
 7.50 
 
 •51 
 
 14,000 
 
 8.75 
 
 •33 
 
 16,000 
 
 10.00 
 
 .18 
 
 18,000 
 
 11.25 
 
 .07 
 
 * Genie rural, Herve Mangon ; t. in., p. 175. 
 
THE ANIMAL AS A MOTOR, 53 
 
 Where the animal must develop maximum power 
 continuously at any considerable speed, the number 
 required for a specific work will always be greatly in- 
 creased. Thus, in coaching, the proprietors of mail- 
 coaches, even on the admirable highways of Great 
 Britain, maintain one horse per mile of route for each 
 coach and worked in fours, so that, going and return- 
 ing, each travels 8 miles per day, working only an hour 
 or less each day on the average. The coach weighs, 
 loaded, two tons, and its coefTicient of friction on good 
 roads is about 0.035. Draught-horses at 2.5 miles an 
 hour are expected to do seven times the work of coach- 
 horses at 10 miles."^ 
 
 18. Tabulated Figures for the work of men and 
 animals follow, as given by Coulomb, Navier, Poncelet, 
 Rankine,t and others. Tables A, B, C, D, etc. 
 
 According to Mr. Box, the work of men and animals 
 may be taken, in foot-pounds per minute, as : 
 
 -Hours per Day. 
 
 F 4 6 8 10 
 
 Man at a winch 220 3,730 3,030 2,640 2,370 
 
 " ""treadmill 130 5,510 4,490 3,890 3,460 
 
 " ""capstan 118 4,420 3, 590 3, 100 2,770 
 
 Horse at a capstan. ... 176 24,780 20,260 17,520 15,670 
 
 Mule "" " 180 16,530 13,460 11,680 10,390 
 
 Ox "" " 120 22,044 17,980 15,570 13,920 
 
 Ass "" " .... 157 6,060 5,610 4,850 4,320 
 
 The average effort of a man at a winch should not 
 be assumed above 15 pounds for a day's work, although 
 more than double that figure may be easily attained 
 for a brief period. From 20 to 30 turns a minute is a 
 
 * Barbour's Cyclopaedia of Manufactures. 
 \ Steam Engine, Chaps. II., III. 
 
54 
 
 THE ANIMAL AS A MACHINE, 
 
 A. WORK OF A MAN.— RANKINE. 
 
 Kind of Exertion. 
 
 Raising his own weight up 
 stair or ladder 
 
 Hauling up weights with 
 rope, and lowering the rope 
 unloaded 
 
 Lifting weights by hand. ... 
 Carrying weights upstairs 
 
 and returning unloaded 
 
 Shovelling up earth to a 
 
 height of 5 ft. 3 in 
 
 Wheeling earth in barrow up 
 
 slope of I in 12, \ horiz. 
 
 veloc. 0.9 ft. per sec, and 
 
 returning unloaded 
 
 Pushing or pulling horizon 
 
 tally (capstan or oar) 
 
 8. Turning a crank or winch. 
 
 9. Working pump. 
 10. Hammering.. . . 
 
 R 
 lbs. 
 
 132- 
 26.5 
 
 12-5 
 
 18.0 
 
 \ 20.0 
 
 13.2 
 15 
 
 V 
 
 ft. per sec. 
 
 and per 
 
 min. 
 
 j 0.5 
 I 30.0 
 
 J 0.75 
 I 4500 
 J 0-55 
 I 3300 
 jo. 13 
 (7-8o 
 
 178^0 
 
 J 0.075 
 \ 450 
 j 2.0 
 I 120.0 
 5.0 & 300 
 2.5 & 150 
 14.4 & 864.0 
 2.5 & 150.0 
 ? 
 
 T" 
 
 RV 
 
 3600 
 (hours 
 p. day). 
 
 ft.-lbs. 
 per sec. 
 
 and 
 per min. 
 
 8 
 
 J 72.5 
 (4550 
 
 
 6 
 
 ]?8oo 
 
 6 
 
 i24.2 
 
 
 1 1452.0 
 
 6 
 
 \ 18.5 
 i IIIO.O 
 
 
 J7.8 
 
 
 I 468.0 
 
 10 
 
 3 9-9 
 1 594-0 
 
 
 8 
 
 1", 
 
 
 (318.0 
 
 ? 
 
 62.5:3750 
 
 8 
 
 45; 3700 
 
 2 mins. 
 
 288; 17280 
 
 10 
 
 33; 1980 
 
 8? 
 
 ? 
 
 RVT 
 
 ft.-lbs. 
 
 per day. 
 
 648,000 
 522,720 
 400,000 
 280,800 
 
 356,400 
 1,526,400 
 
 1,296,000 
 
 1,188,000 
 480,000 
 
 * Net weight of earth in the barrow. 
 
 B. PERFORMANCE OF A MAN IN TRANSPORTING LOADS. 
 
 Kind of Exertion. 
 
 n. Walking unloaded, transport 
 of own weight 
 
 12. Wheeling load L in 2-whld. 
 
 barrow, return'g unloaded. 
 
 13. Ditto in i-wh. barrow, ditto.. 
 
 14. Travelling with burden 
 
 15. Carrying burden, returning 
 
 unloaded 
 
 16. Carrying burden, for 30 se- 
 conds only 
 
 I V 
 
 L ft. per min, 
 lbs. and 
 
 per sec. 
 
 224 
 132 
 90 
 
 252 
 126 
 
 j 100 
 1i§ 
 
 i2i 
 I 150 
 J 100 
 
 o & 702 . O 
 23.i&i38( 
 
 T 
 
 3600 
 (hours 
 p. day.) 
 
 LV 
 lbs. con- 
 veyed 
 I foot. 
 
 10 
 
 700 
 
 10 
 
 373 
 
 10 
 
 220 
 
 7 
 
 225 
 
 6 
 
 233 
 
 
 
 
 
 1474.2 
 
 
 
 
 LVT 
 
 lbs. 
 
 conveyed 
 
 I foot. 
 
 25,200,000 
 
 13,428,000 
 7,920.000 
 5,670,000 
 
 5,032,800 
 
THE ANIMAL AS A MOTOR. 55 
 
 common range of speed, the handle being 15 to 18 
 inches long, and about 3500 foot-pounds per minute a 
 fair performance. 
 
 Mr. D. K. Clark gives the following as the work, 
 for one day, of a laborer, under the specified condi- 
 tions : 
 
 Load. 
 
 
 
 Kind. 
 
 Weight. 
 
 Work. 
 
 Carrying brick . . . 
 
 106 lbs. 
 
 600 mile-lbs. 
 
 coal .... 
 
 100 '* 
 
 342 - " 
 
 Loading wagon . . 
 
 100 '' 
 
 270 " " 
 
 boat 
 
 190 '' 
 
 1230 '' '' 
 
 One man breaks 1.5 cubic yards of stone, or quarries 
 5 to 8 tons of rock per day. 
 
 The walking speed of man is three to four miles an 
 hour. Running eight miles an hour is a common limit ; 
 but 100 miles in a day for a week together, and 11^ 
 miles in one hour, have been attained by practised 
 pedestrians. '' One hundred yards dash " has been ac- 
 complished at the rate of 20 miles an hour. A skater 
 has attained in one mile over 20 miles an hour ; on the 
 bicycle about 30 miles an hour has been reached ; 50 
 miles has been made in 2\ hours, 100 miles in 6 hours, 
 388 in 8 hours, 900 in 72.4 hours. ^ Swimming long dis- 
 tances only an average of about one mile an hour has 
 been made by man ; but the porpoise plays about the 
 bow of ocean steamers making 14 and 15 miles (statute) 
 or more per hour. 
 
 Ruhlmann finds the work done by a Prussian soldier 
 on the march, carrying 64 pounds, to be about 3,000,000 
 foot-pounds per day. Various authorities give about 
 
 * Whiilaker's Almanach, 1S93. 
 
56 THE ANIMAL AS A MACHINE. 
 
 2,000,000 foot-pounds when ascending mountains, and 
 from 1,250,000 to 2,500,000 turning a winch. 
 
 It is customarily assumed that a horse may develop 
 22,500 foot-pounds per minute throughout a day's work 
 of eight hours ; will carry 250 pounds 25 miles in a day 
 of eight hours; and that 1500 pounds, wagon included, 
 is a good load for a horse drawing it on good roads 25 
 miles a day of eight hours. The regular load rarely 
 exceeds one half the maximum. The load which can 
 be raised by a bird is said to be about one half its own 
 weight as a maximum. 
 
 Weisbach states that a man can walk, unloaded, ten 
 hours a day at 3^ miles an hour ; carrying 80 pounds, 
 he can walk seven hours at two thirds that speed. He 
 can walk upstairs, unburdened, at the rate of 0.48 foot 
 per second, eight hours a day, and performing 1,935,360 
 foot-pounds of work per day, assuming his weight to 
 be 140 pounds. He can traverse, without load, 12.5 
 times as much space horizontally as vertically. A day's 
 work with a " rammer," such as is used by paviors, is 
 given as 1,142,400 ft. -lbs. Turning a crank, man accom- 
 plishes 1,175,040, with a mean effort of 16 pounds and 
 a speed of 2.4 feet per second during a working day of 
 eight hours. On a capstan an able-bodied man, also, 
 can perform 1,382,400 foot-pounds of work per day. 
 On the treadmill he attains 1,750,000 foot-pounds. 
 
 The estimates of General Jouffret yield the fol- 
 lowing*: *' According to the Guide JoaimCy the ascent 
 of Mont Blanc, starting from Chamounix, is effected in 
 seventeen hours, resting-spells not included. The dif- 
 ference of level is 3760 metres. A person ascending 
 
 * Theorie de I'Energie ; Paris, 1885. 
 
THE ANIMAL AS A MOTOR. 5/ 
 
 who has a mean weight of 70 kilogrammes produces, 
 then, in order to rise, a work of 3760 x 70 = 263,000 
 kilogrammetres. This work is borrowed from the heat 
 that the carbon and hydrogon contained in the food 
 eaten disengage upon being burned in the lungs. For 
 the sake of simplicity, if we reduce the entire energy to 
 a combustion of carbon, and recall that a kilogramme 
 of the latter furnishes 3,000,000 kilogrammetres, we find 
 that the 263,000 kilogrammetres represented by the 
 ascent correspond to a consumption of 94 grammes of 
 coal — a consumption that should be added to the 
 normal rations necessary for the operation of the organs 
 during a state of rest. Such consumption is 8.35 
 grammes per hour, or 142 grammes for the seventeen 
 hours. The total consumption of coal is 256 grammes, 
 representing 708,000 kilogrammetres. The perform- 
 ance, then, is 
 
 263,000 
 
 708,000 
 
 = 37 per cent. 
 
 *'The performance of the human machine drops to 
 21 per cent when we consider a period of twenty-four 
 hours composed of ten hours of work and fourteen of 
 rest, and a mean daily work of 280,000 kilogrammetres. 
 
 '* The cannon, considered as a machine, is incompar- 
 ably superior to a steam-engine as regards the time 
 necessary to produce a given quantity of mechanical 
 work. 
 
 " Thus, for example, the lOO-ton cannon develops in 
 one JmndredtJi of a second a quantity of work equal to 
 that which would be yielded by a 47-horse-power steam- 
 engine in one hour. A man of average strength is still 
 lighter than an ordinary steam engine of equal power, 
 
58 
 
 THE ANIMAL AS A MACHINE. 
 
 but he is much inferior to the other animals of creation, 
 and particularly to insects. 
 
 C. WORK OF A HORSE AGAINST A KNOWN 
 RESISTANCE. 
 
 Kind of Exertion. 
 
 Cantering and trotting, 
 drawing a light railway 
 carriage (thoroughbred) 
 
 Horse drawing cart or 
 boat, walking (draught- 
 horse) . 
 
 Horse drawing a gin or 
 mill, walking 
 
 Ditto, trotting 
 
 {min. 22^ ) 
 mean 30J > 
 max. 50 ) 
 
 100 
 
 66 
 
 V 
 
 T 
 
 3600 
 
 RV 
 
 i4i 
 
 4 
 
 447f 
 
 3-6 
 
 8 
 
 432 
 
 3-0 
 
 8 
 
 300 
 
 6.5 
 
 4i 
 
 429 
 
 RVT 
 
 6,444,000 
 
 12,441,600 
 
 8,640,000 
 6,950,000 
 
 PERFORMANCE OF A HORSE IN TRANSPORTING 
 LOADS HORIZONTALLY. 
 
 Kind of Exertion. 
 
 L 
 
 /' 
 
 T 
 
 3600 
 
 L V 
 
 LVT 
 
 5. Walking with cart, always loaded 
 
 6. Trotting ditto 
 
 7. Walking with cart, going >oaded, 
 
 returning empty; V = \ mean 
 velocity 
 
 1,500 
 750 
 
 1,500 
 
 3-6 
 7.2 
 
 2.0 
 3-6 
 7.2 
 
 10^ 
 
 4* 
 
 10 
 10 
 7 
 
 5i40o 
 5,400 
 
 3,000 
 
 972 
 
 1,296 
 
 194,400,000 
 87,480,000 
 
 8. Carrying burden, walking 
 
 9. Ditto, trotting 
 
 34,992,000 
 32,659,200 
 
 The average weight of a horse or an ox may be 
 taken as thus : 
 
 Light carriage-horse , . • 800 lbs. 
 
 Heavy " 1200 '* 
 
 Light draught-horse 1000 " 
 
 Heavy " 1600 '* 
 
 Ox 1000 *' 
 
 The horse has galloped a mile in i minute 43 sec- 
 onds, or at the rate of 35 miles an hour, and trotted 
 a mile in 2 minutes 4 seconds, or 29 miles an hour. 
 
THE ANIMAL AS A MOTOR. 59 
 
 An Austrian army officer rode, in June, 1893, from 
 Vienna to Berlin, 388 miles, in 71.33 hours, or 5.45 
 miles an hour, resting an hour in twelve, but losing his 
 horse after the race was concluded. The '' cyclists " 
 have beaten this record. 
 
 Rennie found the hauling power of a draught-horse 
 weighing 1200 pounds was equal to about 108 pounds 
 at 2.5 miles an hour, or 22,300 foot-pounds per minute, 
 for eight hours per day, a 20-mile haul. This is a little 
 over two thirds of a Watt '* horse-power," at which 
 value Rennie rates the average draught-horse, and this 
 is taken to be, ordinarily, five times the power of a 
 man. Between 2\ and 4 miles an hour, the hauling 
 power of the horse is nearly inversely as the speed. 
 
 The mule carries a load of 200 to 400 pounds, and 
 its day's work consists, usually, in the transportation 
 of the equivalent of 5000 to 6000 pounds one mile. 
 The ass carries 175 pounds and upward, and the day's 
 work is the equivalent of 3000 to 4000 pounds one 
 mile. 
 
 According to Weisbach, a horse should be able to 
 carry 240 pounds on its back 3.5 feet per second ten 
 hours a day. Carrying 160 pounds he should be able 
 to trot 7 feet per second seven hours a day, doing, in 
 the day, ten per cent less work than before, nearly. 
 
 The pulling power is said to be, as a rule, about one 
 fifth the weight of the animal. Its usual effort, in the 
 case of the horse at least, is seldom in excess of one 
 tenth, or about one half the maximum. One hundred 
 pounds is a common pull for the average horse in 
 draught vehicles. 
 
 19. Effective Methods of Application of man-power 
 are sought by the engineer. The best is considered to 
 
6o THE ANIMAL AS A MACHINE. 
 
 be that of Coignet ; who arranged hoists in such man- 
 ner that the men employed would go up ladders or 
 stairs to the summit of the lift and then, by their 
 weight applied to the " fall " of the tackle used, de- 
 scending to the ground thus suspended, the work of 
 their descent would be transmitted to the hoist and 
 raise the load. Tables B, C, D, are for common roads. 
 Rankine gives as the approximate relative power of 
 various animals the following : The ox draws a load 
 about equal to that of the horse, the mule one half, the 
 ass one fourth. The ox moves at two thirds the speed of 
 the horse, the mule the same velocity as the horse, the 
 ass the same ; making their respective working powers 
 as I to f , to \ and J, respectively. In all cases, the 
 practical limit is determined by the method of applica- 
 tion, the character of the vehicle, if any, used, and the 
 adjustment of the animal to its surroundings, as well 
 as by its own physical characteristics. Animals do 
 their work mainly by draught of vehicles. Its amount 
 depends largely upon the character of the road 
 traversed. The effort required may be taken as ap- 
 proximately as follows, for total loads, including the 
 vehicle : 
 
 Good country road 50 lbs. per ton. 
 
 Macadamized surfaces 40 '' '' " 
 
 Asphalt pavements 38 '' " '' 
 
 Wood '' 35 " " '' 
 
 Granite tramways 27 '' " " 
 
 Granite pavement, dry, is less likely to cause falls 
 than either wood or asphalt ; when wet, wood is best 
 in this respect. Macadamized and earth roads are safer 
 than either of the pavements. 
 
THE ANIMAL AS A MOTOR. 6 1 
 
 20. The Draught of Vehicles is a case of rolling 
 friction."^ Morin, who made very extended experi- 
 ments, states its laws as follows : 
 
 (i) On hard surfaces, as paved and macadamized 
 roads, the resistance is directly proportional to the 
 weight of vehicle and load, inversely proportional to 
 the diameter of wheel, and independent of the breadth 
 of wheel-tire. It increases with velocity. 
 
 (2) On soft ground the resistance increases inversely 
 as the breadth of tire. It does not sensibly vary with 
 velocity. Morin concludes, also, that the line of draught 
 should be horizontal. 
 
 Dupuit, on macadamized roads, found the resistance 
 to vary nearly inversely as the square root of the di- 
 ameter of wheel and directly as the load. He found 
 the resistance on pavements to be increased at high 
 speeds by the concussions incident to rapid movement. 
 Clark obtains a somewhat less simple law, which he ex- 
 presses thus : 
 
 R=:a-\-bv^ yfTu, . . . . (i) 
 
 The work of hauling is then 
 
 U^Rs^{a^bv-\- ^/'^i)vt. . . . (2) 
 
 This formula is deduced from the experiments of 
 Macneil on ** metalled " roads. f The values of the 
 constants are, in British measures, <^ = 30 ; /^ =: 4 ; ^ = 10 
 pounds per ton, v being given in miles per hour, / in 
 hours. :t 
 
 * Friction and Lost work; Thurston, p. 84. 
 f Clark's Manual, p. 964. 
 X Parnell on Roads, p. 464. 
 
62 THE ANIMAL AS A MACHINE. 
 
 The resistance of all vehicles on common roads and 
 streets is principally resistance to rolling, their axle- 
 friction being comparatively small. The work of haul- 
 ing is, then, 
 
 U = Fs = fWs = fWvt (3) 
 
 The draught of vehicles loaded in any stated manner 
 may be made comparatively easy or dif^cult by proper 
 or improper methods of attachment of the animal to 
 the vehicle.* 
 
 The general principles to be observed are the fol- 
 lowing : 
 
 (i) In hauled loaded vehicles, the Hne of traction 
 should be made such as to make the hauling power 
 dependent upon adhesion between the animal and the 
 ground equal to the resistance of the vehicle, with 
 some margin of insurance against occasional slipping. 
 
 (2) The heavier the load, if in excess of the hauling 
 power due the animal's weight, the more should that 
 weight be reinforced by so adjusting the line of trac- 
 tion that it may have a vertical component tending to 
 raise the load and increase the holding and hauling 
 power of the feet of the animal. 
 
 (3) With loads lighter than those demanding the 
 total adhesion due the weight of the animal, the line 
 of traction should be so located that the haul, and, if 
 possible, the load itself, may take off a part of the 
 animal's weight. 
 
 Thus, with a two-wheeled vehicle the load may usu- 
 ally be so distributed as either to be carried, in part, 
 
 * Mr. T. H. Brigg has made a study of this point, with interesting 
 results. Trans. Am. Soc. M. E , 1893. 
 
THE ANIMAL AS A MOTOR. 63 
 
 by the horse, or to balance a part of the weight of the 
 animal ; the latter either carrying part and hauling 
 part of the load, or hauling the load and, with it, a 
 part of its own weight, transferred, by the inclined 
 upward line of traction, to the load. The former dis- 
 position is obviously suitable for heavy loads and steep 
 gradients, the latter for light loads and level or falling 
 stretches of road. Heavy wagons should be handled in 
 such manner as to give the former, light carriages the 
 latter, adjustment. It would probably, in the case of the 
 heavy vehicle be well to provide, if practicable, for the 
 change of the line of pull to suit the load and gradient, 
 as has been practised by Mr. Brigg ; who finds, in some 
 cases, a loss of one half the mechanical efficiency at- 
 tainable, due to inappropriate methods of attachment 
 of the animal to the vehicle."^ He concludes : 
 
 " The resistance which a horse can overcome depends 
 upon the following conditions : (i) his own weight ; 
 (2) his grip ; (3) his height and length ; (4) direction of 
 trace ; (5) his muscular development, which determines 
 the power to straighten the bent lever represented by 
 his body and hind legs against the two resistances, the 
 vehicle through the trace attached to the shoulder and 
 the hind feet against the ground. 
 
 *' To pull through a very low trace, or to have a man, 
 or even two or three men, on a horse's back is advisable 
 and even necessary if a horse is expected to haul a 
 load requiring the full force of his muscles at any par- 
 ticular moment — and for the moment, under such con- 
 ditions, he would be able to draw a much greater load 
 than without the added weight. But any person can 
 
 Ibid. 
 
64 THE ANIMAL AS A MACHINE. 
 
 see that the animal could not travel far with any 
 vehicle if he must carry three men on his back in 
 addition to hauling his load." 
 
 " Therefore, to deal justly with our horses, we should 
 not only study cause and effect, but should devise some 
 means by which, automatically, every possible advan- 
 tage could be given to the horse at all times.* Other- 
 wise there must be a constant waste of energy, tiring 
 the horse prematurely and increasing the chances of 
 his stumbling and falling." 
 
 These principles are thus illustrated by Mr. Brigg : 
 
 In the accompanying figure, let the horse be har- 
 nessed in the usual manner and driven up hill. 
 
 Suppose that the horse is exerting a force of 36 lbs. 
 through AB in a line from the hame to the centre of 
 the wheel. Let AC represent the vertical depression 
 necessary to hold down the shafts. Since AB and AC 
 are the forces necessary to produce motion, by com- 
 pleting the parallelogram ACDB we find that AD 
 represents the resultant of the forces AC and AB. 
 Thus we determine one arm of the lever, GS, acting 
 against GT, the other arm. GS is a line drawn at right 
 angles from the resolved angle of force AD. 
 
 If the load had been balanced on the axle, then, 
 regardless of the angle of trace or hame-chain, the 
 angle of draught would be through AB to the centre 
 of the wheel. Then a line at right angles with AB to G 
 would have been the short arm of the lever, which would 
 have enabled the horse to have pulled a much greater 
 load than is possible with the longer arm, GS. But, 
 
 * Mr. Brigg had already devised and applied such a system of self- 
 adjustment of the harness as to secure this effect. 
 
THE ANIMAL AS A MOTOR. 
 
 65 
 
 the load being behind the axle, the forward weight 
 of the animal is reduced by the lift of the shafts at A, 
 and the result is the same as if the traces had been 
 put up at the point D, and the load, with a 33-lb. pull 
 through such a trace, would be exactly balanced. 
 
 Let UV represent the horizon passing through the 
 point D. If DA represents 33 lbs., then FA will 
 
 Vendh-fgio pulfffie Horse\ 
 ~ n G off the Ground 
 
 Resultant of Components A B and A C as A D, or N D added 
 to Horse's Weight, N D equals U taken from the Load 
 and Carried by the Horse, 
 
 Fig. I . — Haulage of Vehicles. 
 
 represent 4 lbs., so that 4 lbs. must be added to the 
 horse's natural weight by the pull AD. Or, if the pull 
 through the trace AB is 36 lbs., then, drawing BE 
 parallel wdth the horizon UV, EA (14 lbs.) will repre- 
 sent the depression due to a 36-lb. pull through AB. 
 But when the lift due to the shafts, 10 lbs., is deducted 
 from the depression of 14 lbs., there remains as before 
 an increased weight of 4 lbs. on the horse. 
 
 When the horse is pulling with the same force upon 
 a level, as in Fig. 2, we find very different results. 
 Let PA be the direction from the hames to the centre 
 
66 
 
 THE ANIMAL AS A MACHINE. 
 
 of the wheel and representing a 36-lb. pull. The load 
 having been moved farther to the rear, the lift at the 
 belly-band is still 10 lbs. 2X P — the load is moved back- 
 ward to shift the centre of gravity. The resultant of 
 the two components PA and PB is PC, and PC now 
 equals about 35.9 lbs., whereas the resultant AD in 
 Fig. 6 is only 33 lbs., or 2.9 lbs. less than on the level. 
 It will now be found that 36 lbs. pull through PA will 
 increase the horse's weight 4.5 lbs., represented by 
 PO, which is determined by drawing AO from A 
 parallel with the horizon, cutting the Hne of gravity PE, 
 
 X """^----.-.^.s^ 
 
 Fig. 2. — Haulage of Vehicles. 
 
 But, as the disposition of the load is such that 10 lbs. 
 are taken from the horse, it is obvious that, if only 4.5 
 lbs. are put back by the stated pull of 36 lbs., the horse 
 has still 5.5 lbs. less than his natural weight in Fig. 2, 
 while in Fig. i he has 4 lbs. more than his natural 
 weight. 
 
THE ANIMAL AS A MOTOR. 
 
 67 
 
 If the load be shifted to the front end of the cart, 
 as indicated in Fig. 3, the resultant of the forces PJ 
 and PK hes in the direction of PL, and the added 
 
 Fig, 3. — Haulage of Vehicles. 
 
 weight on the horse is 22 lbs. instead of 4 lbs. as in 
 Fig. I, tending to thrust his hind foot into the ground 
 at O, and he is able to pull 40 lbs. as against 33 lbs. 
 under the conditions indicated in Fig. i. 
 
 It will be observed in Fig. i that the point of appli- 
 cation of force A (the hame) is above the horizontal 
 line UV, drawn through the point D, this being the 
 point at which the traces might be fixed with an 
 advantage equal to having them attached to the axle 
 when the given lift is exerted at A, with a lift at the 
 belly-band as set forth ; whereas P, the point of appli- 
 
68 THE ANIMAL AS A MACHINE. 
 
 cation of force in Fig. 2, is now much below the hori- 
 zontal line MN, drawn through the point C on the 
 resultant, or virtual line of draught. Comparing the 
 triangles ABE (Fig. i) and PAO (Fig. 2), AB and 
 PA represent the pull through the traces, and, al- 
 though the force is the same — 36 lbs., the result is 
 different. 
 
 If AB in Fig. i represents a 36-lb. pull, and AC "d. 
 lO-lb. lift, then AD (33 lbs.) is the resultant direction 
 of force appHed by the animal. A 36-lb. pull through 
 AB, together with a lift of 10 lbs. through AC ox 2. 
 pull of 33 lbs. through AD, will both be effective in 
 lifting 2.6 lbs. from the horse's fore quarters.* 
 
 Thus the animal may be very effectively aided, or 
 may be totally incapacitated by good or bad adjust- 
 ment of the line of traction. In all cases this Hne 
 should be given such incHnation as will insure increased 
 pressure of the animal upon the ground for heavy pull- 
 ing, and decrease its weight in the opposite case, just 
 to the extent required to make adhesion ample with- 
 out unnecessary surplus. 
 
 21. Muscular Power varies enormously with the 
 animal, its condition, habits of exercise, and other cir- 
 cumstances ; but the results of many experiments indi- 
 cate that the muscles of the human body have a power 
 measured, in good condition, by a maximum of not 
 far from 10 kilogrammes per square centimetre, and 
 averaging 7 or 8 (142,110,114 pounds per square inch 
 respectively). The influence of exercise and custom 
 on the working power of the muscle is enormous, in 
 some cases being found to vary in the proportion of 
 
 Ibid. 
 
THE ANIMAL AS A MOTOR. 69 
 
 one to at least three. ^ This quantity of work done 
 has no ascertained relation to the value of the energy 
 of the foods consumed ; although the work which an 
 animal can do is dependent upon the quantity of energy- 
 producing food which it can digest and assimilate under 
 the conditions to which it is subjected while at work. 
 The stored energy of the foods varies, according to 
 Frankland, from about 500 kilogrammes per gramme, or 
 45 foot-pounds per ounce, for lean meats, to three times 
 this quantity for the grain-foods and to six times this 
 value for butter; but the total need of the system 
 determines the kind and quality of food desirable at 
 any given time and for any given case. In general 
 the use of the grain-foods is, from a scientific and 
 possibly from a physiological point of view, most 
 productive of useful power in both man and the 
 domestic animals. Where the work is severe and long- 
 continued no time is allowed for proper digestion and 
 assimilation, and in such cases special care must be taken 
 to provide the best conditions for insuring endurance. 
 It is in illustration of this point that the case of the Arab 
 living on the coffee-berry, and the pedestrian on long 
 walks living entirely on the same material in the form 
 of a beverage, may be referred to. The warm drink is 
 at once stimulus and food, and demands little energy 
 in digestion and assimilation. A permanent dietary, 
 however, must contain all the elements demanded for 
 nutrition of all parts of the system in proper propor- 
 tions, and must at the same time provide the needed 
 mechanical and other stimuli of all the organs of the 
 body. The ivJiole wheat used by man, fruits, and the 
 
 * Nipher on Strength of the Muscle, Am. Jour. SlL, Nov. 1875. 
 
JO THE ANIMAL AS A MACHINE. 
 
 grains consumed by horses and cattle are considered 
 to be most perfect examples of these foods. Eggs and 
 milk, among animal foods, correspond most nearly to 
 the same desirable composition, but require an admix- 
 ture of vegetable foods to insure their proper action in 
 the human system. The meats are always defective 
 in essential elements of food, and can never be safely 
 used alone by man. The carnivora, devouring the 
 whole body of their prey, and especially fond of the 
 blood, which contains all its elements in solution, are 
 able thus to live upon animal food. 
 
 Working animals are always herbivorous or grami- 
 nivorous, and, as in the case of man, should have their 
 best dietary carefully determined to insure their effi- 
 cient action as prime movers, and maximum economy 
 of transformation of the potential energy of their 
 foods into mechanical power. When doing no work 
 an herbivorous diet is probably best ; but when work- 
 ing the grains, and when hard worked "cut feed " and 
 coarse meals, mixed with a moderate amount of water 
 and given warm, are best. Cold water should be avoided 
 with meals, and when the creature is warm from exer- 
 tion especially ; but oat-meal water can be safely taken 
 in any quantity by man or beast. 
 
 22. The Uses of Foods in the body are thus stated 
 by Professor Atwater^ : 
 
 Food furnishes : 
 
 (i; The material of which the body is made. 
 
 (2) The material to repair the wastes of the body, and to protect 
 its tissues from being unduly consumed. 
 
 Food is consutned as fuel in the body to : 
 
 (3) Produce heat to keep it warm. 
 
 * Century Magazine, July 1887, P- 370. 
 
THE ANIMAL AS A MOTOR. 7 1 
 
 (4) Produce muscular and intellectual energy for the work it has to 
 do. 
 
 The body is built up and its wastes are repaired by the nutrients. 
 
 The nutrients also serve as fuel to warm the body and supply it with 
 
 strength. 
 
 [forms the nitrogenous basis of blood, muscle, 
 
 ^, . , r . I sinew, bone, skin, etc. 
 
 The protein of food A . , , . , , ,1., 
 
 *^ IS changed mto fats and carbohydrates. 
 
 \^is consumed for fuel. 
 
 ^, , ^ r r J \ *^^^ stored in the body as fat. 
 
 The fats of food \ , , -^ 
 
 ( are consumed for fuel. 
 
 The carbohydrates j are changed into fat. 
 
 of food { are consumed for fuel. 
 
 ^, . , ( are transformed into the mineral matters of 
 
 The mmeral matters ) , j t. • 
 
 \ bone and other tissue, 
 of food \ , . . ^, 
 
 ( are used m various other ways. 
 
 A growing child or young animal requires much 
 muscle and nerve-making material, and the proportions 
 of the several elements in the food are more nearly 
 those of the body itself than in the case of the adult. 
 The adult, when doing little work, requires little food, 
 and that mainly of the kinds which are required to 
 supply heat and to compensate the slight wastes of 
 tissue then occurring ; while the working system, and 
 particularly if hard worked, demands considerable 
 quantities of combustible, heat-producing food. Simi- 
 lar differences of dietary are required, as the climate 
 compels the development of more or less of caloric to 
 preserve the temperature of the body, which at above 
 104" Fahr., or a little below 98", fails to meet the 
 requirements of life. 
 
 According to Dr. Letheby, the working-power of the 
 human body may be taken as follows * : 
 
 * Letheby on Food, p. 96. 
 
72 
 
 THE ANIMAL AS A MACHINE. 
 
 Foot-pounds. 
 External work or actual labor.. i,oi 1,670 
 
 Work of circulation (75 beats a minute). . . . 500,040 
 
 Work of respiration (15 a minute) 98,496 
 
 Total ascertainable work per day 1,610,206 
 
 The ascertainable external and internal work of the 
 food we eat is only one sixth of its actual energy, ac- 
 cording to Letheby ; but it is not impossible that the 
 unascertained work of the vascular system and other 
 parts may account for the full amount, nearly. 
 
 According to Dr. Frankland, this power is supplied 
 by food in the following proportions ^ : 
 
 ENERGY-VALUES OF FOODS. 
 
 
 Per Cent 
 
 of 
 Water 
 in Ma- 
 terial. 
 
 Pounds of Water 
 Raised i° F. 
 
 Pounds Lifted i 
 Foot High. 
 
 Name of Food. 
 
 When 
 
 Burnt 
 
 in 
 
 Oxygen. 
 
 When 
 
 Oxidized 
 
 in the 
 
 Body. 
 
 When 
 
 Burnt 
 
 in 
 
 Oxygen. 
 
 When 
 
 Oxidized 
 
 in the 
 
 Body. 
 
 Butter 
 
 15 
 24 
 15 
 15 
 15 
 13 
 47 
 19 
 62 
 
 44 
 54 
 71 
 71 
 
 71 
 73 
 
 87 
 86 
 89 
 
 18.68 
 
 11.95 
 
 10.30 
 
 10.12 
 
 10 12 
 
 9.80 
 
 8.82 
 
 8.61 
 
 6.13 
 
 5-74 
 5-09 
 4.60 
 3-38 
 3.38 
 2.60 
 1.70 
 1.36 
 1. 12 
 
 18.68 
 11.20 
 10.10 
 9.87 
 9-57 
 9-52 
 8.50 
 8.61 
 5.86 
 5-52 
 4.30 
 4.14 
 3-01 
 3.01 
 2.56 
 1.64 
 1.33 
 1.08 
 
 14-421 
 9.225 
 7-952 
 7.813 
 7-813 
 7.566 
 6.809 
 6.649 
 4-732 
 4-431 
 3.929 
 3-551 
 2.609 
 2.609 
 2.007 
 1.312 
 I-050 
 .864 
 
 14.421 
 8.649 
 7.800 
 7-623 
 7-487 
 7.454 
 6.559 
 6.649 
 4.526 
 4.263 
 3.321 
 3.200 
 2.324 
 2.324 
 1.987 
 1.246 
 1. 031 
 .834 
 
 Cheese 
 
 Oatmeal 
 
 Wheat flour 
 
 Ground rice 
 
 Yolk of efifsf 
 
 Lump sugar 
 
 Entire t^g (boiled). . 
 Bread 
 
 Ham 
 
 Mackerel. 
 
 Lean beef 
 
 Lean veal 
 
 Potatoes 
 
 Milk 
 
 Carrots 
 
 Cabbage 
 
 
 * Frankland on Food of Man, 1887, p. 68. 
 
THE ANIMAL AS A MOTOR. 
 
 73 
 
 23. Dietaries. — Dr. Pavy gives the following as the 
 quantities of the specified foods^required to support 
 human Hfe * : 
 
 Nitrogen , 300 grains. 
 
 Carbon 4800 " 
 
 Carbon. Nitrogen. 
 
 14,000 grains (2 lbs.) of bread contain 4200 140 
 
 5,500 " (about I lb.) of meat contain 605 165 
 
 Total (2f lbs.) 4805 305 
 
 Six pounds meat \ 4^°° S""^^"^ c^^^^"' 
 
 ( 1309 " nitrogen. 
 
 Four pounds bread \ 9°°° ^'^'""^ ^^'^b^"- 
 
 ( 300 " nitrogen. 
 
 The estimates of Moleschott for weight of foods in a 
 dry state, for the average individual, are as follow : f 
 
 Dry Food. 
 
 Albuminous matter 
 
 Fatty matter 
 
 Carbohydrates 
 
 Salts 
 
 Total 
 
 In Oz. 
 
 Avoir. 
 
 4.587 
 
 2.964 
 
 14.250 
 
 1.058 
 
 22.859 
 
 In Grains. 
 
 2006 
 
 1296 
 
 6234 
 
 462 
 
 9998 
 
 In Grammes. 
 
 130 
 
 84 
 
 404 
 
 30 
 
 648 
 
 Reckoning ordinary food to contain 50fi^ of water, then, these 23 
 ounces will correspond to 46 ounces solid food in the condition eaten 
 — additional to this, 60 to 80 ounces of water is taken in some form. 
 The dynamic or force-producing value of this daily standard diet 
 amounts to about 4000 foot-tons. 
 
 The relative values of the common articles of diet 
 are given by Scammell as follows \ : 
 
 * Treatise on Food, p. 473. 
 
 t Ibid., p. 452. Also Mott's Chart (N. Y., J. Wiley & Sons, 1889). 
 
 X Mott's Chemist's Manual, p. 575. 
 
74 THE ANIMAL AS A MACHINE, 
 
 THE RELATIVE VALUES OF FOODS. 
 
 Articles. 
 
 Wheat 
 
 Barley 
 
 Oats 
 
 Northern corn. , 
 Southern " . 
 Buckwheat. . . . 
 
 Rye 
 
 Beans 
 
 Peas 
 
 Rice 
 
 Potatoes 
 
 Parsnips 
 
 Turnips 
 
 Cabbage 
 
 Milk 
 
 Veal 
 
 Beef... 
 
 Lamb 
 
 Mutton 
 
 Pork 
 
 Chicken 
 
 Codfish 
 
 Trout 
 
 Salmon 
 
 Oysters 
 
 Eggs (white of) 
 " (yolk of). 
 
 Butter 
 
 Bacon 
 
 Cheese 
 
 Chocolate 
 
 Cream 
 
 Ham 
 
 Lard 
 
 Onions 
 
 Barley 
 
 As 
 
 Material 
 
 for the 
 
 Muscles. 
 
 As 
 
 Heat- 
 givers. 
 
 14.6 
 
 66.4 
 
 12.8 
 
 52.1 
 
 17.0 
 
 50.8 
 
 12.3 
 
 67.5 
 
 34.6 
 
 39-2 
 
 8.6 
 
 530 
 
 6.5 
 
 75.2 
 
 24.0 
 
 40.0 
 
 23.4 
 
 41.0 
 
 5.1 
 
 82.0 
 
 1.4 
 
 15.8 
 
 2.1 
 
 14.5 
 
 1.2 
 
 4.0 
 
 1.2 
 
 6.2 
 
 5-0 
 
 8.0 
 
 17.7 
 
 14-3 
 
 19.0 
 
 14.0 
 
 19.6 
 
 14-3 
 
 21.0 
 
 14.0 
 
 17-5 
 
 16.0 
 
 21.6 
 
 1.9 
 
 16.5 
 
 I.O 
 
 16.9 
 
 0.8 
 
 20.0 
 
 Some fat 
 
 12.6 
 
 
 13.0 
 
 .... 
 
 16.9 
 
 29.8 
 
 * 8'.4 
 
 100. 
 62.5 
 
 30.8 
 
 28.0 
 
 8.8 
 
 3-5 
 
 35-0 
 
 88.0 
 
 4-5 
 32.0 
 
 .... 
 
 lOO.O 
 
 0.5 
 
 5-2 
 
 4-7 
 
 78.0 
 
 As Food 
 
 for the 
 
 Brain and 
 
 Nervous 
 System. 
 
 1.6 
 
 4.2 
 3.0 
 I.I 
 4.1 
 1.8 
 0.5 
 3 5 
 2.5 
 0.5 
 0.9 
 1.0 
 
 0.5 
 0.8 
 1.0 
 
 2.3 
 2.0 
 2.2 
 2.0 
 2.2 
 2.8 
 2.5 
 4-3 
 6 or 7 
 0.2 
 2.8 
 2.0 
 
 0.5 
 4.7 
 1.8 
 
 4.4 
 
 0.5 
 0.2 
 
 Water, 
 
 14 o 
 14.0 
 13.6 
 14.0 
 14 o 
 14.2 
 
 13-5 
 14.8 
 14. 1 
 9.0 
 74.8 
 794 
 90.4 
 
 91-3 
 86.0 
 
 65.7 
 65.0 
 
 63.9 
 63.0 
 
 64.3 
 
 73-7 
 80.0 
 78.0 
 74.0 
 87.2 
 84.2 
 51.3 
 
 28'. 6 
 36.5 
 
 92.0 
 28.6 
 
 93-8 
 9-5 
 
 Waste. 
 
 3.4 
 16.9 
 16.9 
 
 5.1 
 
 8.1 
 22.4 
 
 4.3 
 17.7 
 19.0 
 
 3-4 
 7.1 
 3.0 
 3-9 
 0.5 
 
 1-4 
 
 7.6 
 
 The study of these figures permits the construction 
 of a proper dietary for any case in which stated 
 rations are required or desirable. Professor Atwater 
 gives the following"^ : 
 
 * Century Magazine, 185S, p. 25S. 
 
THE ANIMAL AS A MOTOR. 
 
 75 
 
 STANDARDS FOR DAILY DIETARIES.* 
 
 Weights of Nutrients and Calories of Energy (Heat Units) 
 IN Nutrients required in Food per Day. 
 
 1. Children to ij^ years \ 
 
 2. Children 2 to 6 years \ 
 
 3. Children 6 to 15 years \ 
 
 4. Aged woman 
 
 5. Aged man 
 
 6. Woman at moderate work j 
 
 (Voit) f 
 
 7. Man at moderate work (Voit). 
 
 8. Man at hard work (Voit) 
 
 9. Man with moderate exercise I 
 
 Playfair) f 
 
 10. Active labor (Playfair) 
 
 11. Hard labor (Playfair) 
 
 12. Woman with light exercise I 
 
 (Writer) f 
 
 13. Man with light exercise ( 
 
 (Writer) ( 
 
 14. Man at moderate work | 
 
 (Writer) \ 
 
 15. Man at hard work (Writer) 
 
 
 Nutrients. 
 
 
 
 
 
 
 
 Poten- 
 
 Protein. 
 
 Fats. 
 
 Carbo- 
 hydrates. 
 
 Total. 
 
 tial 
 Energy. 
 
 Grms. 
 
 Grms. 
 
 Grms. 
 
 Grms. 
 
 Calories. 
 
 28 
 (20-36) 
 
 (36-70) 
 
 37 
 
 (30-45) 
 
 40 
 
 (35-48) 
 
 75 
 
 (60-90) 
 
 200 
 
 (100-250) 
 
 140 
 
 295 
 
 767 
 1418 
 
 (70-80) 
 80 
 100 
 
 (37-50) 
 50 
 68 
 
 (250-400) 
 260 
 
 350 
 
 443 
 
 390 
 518 
 
 2041 
 
 1859 
 2477 
 
 92 
 
 44 
 
 400 
 
 536 
 
 2426 
 
 118 
 145 
 
 56 
 100 
 
 500 
 450 
 
 674 
 695 
 
 3055 
 3370 
 
 119 
 
 51 
 
 531 
 
 701 
 
 3139 
 
 X 
 
 71 
 71 
 
 568 
 568 
 
 795 
 824 
 
 3629 
 3748 
 
 80 
 
 80 
 
 300 
 
 460 
 
 2300 
 
 100 
 
 100 
 
 360 
 
 560 
 
 2820 
 
 125 
 
 125 
 
 450 
 
 700 
 
 3520 
 
 150 
 
 150 
 
 500 
 
 800 
 
 4060 
 
 DIETARIES FOR MAN DOING MODERATE MUSCULAR 
 
 V^ORK. 
 
 
 Nutrients. 
 
 Potential 
 
 
 Protein. 
 
 Fats. 
 
 Carbo- 
 hydrates. 
 
 Energy. 
 
 Playfair 
 
 119 grms. 
 130 " 
 
 120 " 
 118 " 
 
 51 grms. 
 40 " 
 
 35 " 
 56 " 
 
 530 grms. 
 550 " 
 540 " 
 500 " 
 
 3135 calories 
 3160 " 
 3032 " 
 3055 
 
 Moleschott 
 
 Wolff 
 
 Voit 
 
 
 Mr. Edward Atkinson has given a number of die- 
 taries, each having the requisite proportion of proteids, 
 
 * Nos. I, 3, 4, and 5 are as proposed by Voit and his followers ol 
 the Munich School ; No. 2 by Atwater. One ounce = 2'^\ grammes, 
 nearly. 
 
1^ 
 
 THE ANIMAL AS A MACHINE. 
 
 Starch, and fat for thorough nutrition with minimum 
 consumption of food and at minimum cost. Of these 
 the following is an example of a dietary which would 
 serve where low wages or other conditions compel the 
 adoption of most economical rations : 
 LOW-COST DIETARY.* 
 Proteid. Fat. 
 
 Article. Pounds, 
 
 Flour 22 
 
 Grain 12 
 
 Butter 2 
 
 Suet 2 
 
 Sugar 2 
 
 Potatoes 10 
 
 Beets 
 
 Carrots 
 
 Onions 
 
 Squash 
 
 Cabbage 
 
 Parsnips J 
 
 2.64 
 
 1.68 
 
 .02 
 
 .20 
 
 .44 
 
 .84 
 
 1.73 
 
 1.78 
 
 Carbo- 
 hydrate. 
 
 15.18 
 
 7.60 
 
 1-93 
 2.10 
 
 Calories. Cost at Bos- 
 ton prices 1891 
 
 0.55 
 
 13 .03 
 
 50 
 
 36,520 
 19,800 
 7,230 
 7,200 
 3,600 
 4,300 
 
 120 
 
 57 4.67 4.82 27.31 
 
 1.90 .155 .160 .910 
 
 Variables in Table Showing Method of Analysis 
 Beef, neck or 
 
 I2C".S^)2.00 .40 
 
 5 -62 .34 
 
 4 .40 2.80 
 
 2 .40 .10 
 
 I .19 -03 
 
 I .03 .78 
 
 For 30 days. 
 For I day.. . 
 
 shin 
 
 Mutton, neck. 
 
 Bacon 
 
 Beef-liver. . . . 
 
 Veal 
 
 Salt Pork.... 
 
 79,770 
 2,659 
 
 5,200 
 2,476 
 11,840 
 1,120 
 460 
 3,160 
 
 .48 
 .56 
 .12 
 .10 
 .25 
 
 .25 
 
 $2.31 
 .077 
 
 .72 
 .30 
 .48 
 .12 
 .08 
 .08 
 
 For 30 days. . 25 
 
 3.64 4-45 
 
 Total. 
 
 82 
 
 For I day. . . . 2.73 
 
 .277 
 
 9.27 
 .309 
 
 27.31 
 .910 
 
 24,256 
 
 104,026 
 3,467.5 
 
 .78 
 
 $4.09 
 .136 
 
 The succeeding dietary is one which is considered 
 an economical and satisfactory scheme for families of 
 
 * The prices on which these computations are made were the retail 
 prices in Boston, Mass., U. S. A., in the first six months of the year 
 1891. 
 
THE ANIMAL AS A MOTOR. 7/ 
 
 small income. In both cases the first list will sustain 
 life, and the second comprises the usually added but 
 unessential articles. In acting as commissary the en- 
 gineer should endeavor always to provide the equiva- 
 lent of the first dietary, and, where practicable, the 
 second. 
 
 22 
 
 3 
 
 Articles. 
 
 pounds Flour, 
 " Oatmeal, 
 
 
 at 
 at 
 
 |0.02^ 
 .04 
 
 $0.55 
 .12 
 
 \^cllUIlCS. 
 
 3 
 
 " Cornmeal, 
 
 
 at 
 
 .03 
 
 .09 
 
 
 6 
 2 
 
 " Hominy, 
 " Butter, 
 
 
 at 
 
 at 
 
 .04i 
 
 .28 
 
 .27 
 .56 
 
 
 2 
 
 Suet, 
 
 
 at 
 
 .06 
 
 .12 
 
 
 lO 
 
 " Potatoes, 
 
 
 at 
 
 .02^ 
 
 .25 
 
 
 3 
 
 2 
 
 " Cabbages, 
 " Carrots, 
 
 
 at 
 at 
 
 .03 
 
 .02| 
 
 .09 
 •05 
 
 
 2 
 
 " Onions, 
 
 
 at 
 
 .o5i 
 
 .11 
 
 
 2 
 2 
 
 Sugar, 
 - 57 
 
 Variables, 
 pounds shin of Beef, 
 
 " round of Beef, 
 
 
 at 
 
 at 
 at 
 
 .05 
 
 $0.06 
 
 .18 
 
 .10 
 
 $2.31 
 
 $0.36 
 .36 
 
 79»770 
 
 6 
 
 " neck of Mutton, 
 
 
 at 
 
 .06 
 
 .36 
 
 
 2 
 
 I 
 
 Eggs, 
 " Cheese, 
 
 
 at 
 
 at 
 
 .18 doz. .27 
 .16 .16 
 
 
 30 
 
 Skimmed Milk, 
 
 
 at 
 
 .02 
 
 .60 
 
 
 I 
 
 White Beans, 
 
 
 at 
 
 .07 
 
 .07 
 
 
 I 
 
 Pease, 
 
 
 at 
 
 .07 
 
 .07 
 
 
 4 
 
 2 
 
 " Halibut, nape, 
 Haddock, 
 
 
 at 
 at 
 
 .05 
 .08 
 
 .20 
 .16 
 
 
 3 
 
 " Salt Cod, 
 
 
 at 
 
 .08 
 
 .24 
 
 
 I 
 
 2 
 
 " Oleomargarine, 
 " Macaroni, 
 
 
 at 
 at 
 
 .16 
 .15 
 
 .16 
 .30 
 
 
 I 
 2 
 
 " Oatmeal, 
 Cornmeal, 
 
 
 at 
 at 
 
 .04 
 .03 
 
 .04 
 .06 
 
 
 I 
 
 Rice, 
 
 
 at 
 
 .06 
 
 .06 
 
 
 I 
 
 " Hominy, 
 -66 
 
 
 at 
 
 .04 
 
 .04 
 
 $3-51 
 
 41,051 
 
 
 123 pounds, total for 30 days 
 
 4.1 " " " I day. 
 
 Cost per 
 
 week 
 
 , $1-35. 
 
 $5.82 
 .194 
 
 120,821 
 4.027 
 
78 THE AiYIMAL AS A MACHINE 
 
 24. The ''Mechanism of Transmission" of the 
 
 power of the animal is the vehicle or other apparatus 
 through which the power is exerted in the moving of 
 the load. In some cases the load is directly applied, as 
 where pack-animals are employed ; in others a wagon 
 is used ; in still other cases the pull on a rope is made 
 effective in raising weights. A strong man can walk 
 an average of about 3^^ miles an hour 10 hours a day, 
 unloaded ; under 80 pounds he can walk at half this 
 speed seven or eight hours a day ; and he may lift at 
 long intervals 180 to 200 pounds. The work of hori- 
 zontal transport may be approximately computed by 
 taking it at 0.08 the product of weight carried into 
 distance moved over. Thus measured, we find from 
 the above statement that a man should do about 
 2,000,000 foot-pounds of work per day, his weight 
 being included in the amount taken as load. By the 
 use of a wagon, or its equivalent, the weights that may 
 be transported are increased, often, ten times or more. 
 Training may double the efficiency of a workman in 
 manual employments and enormously increase it in 
 cases of skill coming of long practice. The differences 
 between reputably first-class workmen may amount to 
 15 or 20 per cent. 
 
 The pull of the average draught-animal is usually 
 not far from one fifth its weight. Gerstner gives us 
 the following"^ : 
 
 Weight. Av. Pull. Fft. per Work per Work per 
 Lbs. Lbs. Sec. Av. Sec. 8-hr. Day. 
 
 Man 150 30 2.5 75 2,160,000 
 
 Horse... 600 120 4.0 480 13,824,000 
 
 Ox 600 120 2.5 300 8,640,000 
 
 Mule 500 100 3.5 350 10,080,000 
 
 Ass 360 72 2.5 180 5,184,000 
 
 * Mechanik, vol. i. 
 
THE ANIMAL AS A MOTOR. 79 
 
 25. Equations connecting the time, effort, and work 
 of animals have been proposed, all of which are only- 
 approximate, at best ; since the conditions of each 
 case are certain to differ more or less from the mean, 
 and are always difficult to evaluate. Rankine follows 
 Maschek, who gives the expression 
 
 ^ _F r _ 
 
 i?, + F, "f" r, ~ ^ ' 
 
 in which i?, , F, , T^, are respectively one third, each, 
 of the maximum load, maximum speed, and maximum 
 time in the day's work. Thus a maximum day's work 
 is obtained under the load R — R^, at the speed 
 F= F, , and T^^T^, working eight hours per day. 
 Any departure from this adjustment is presumed to 
 give sensible loss of result. Bouguer proposes and 
 Gerstner endorses the following, R^ and V^ being max- 
 imum loads and speeds : 
 
 ^ = (- vY' 
 
 Gerstner, taking R^ and V, at their mean values, as 
 per table, would write the equations thus : 
 
 For small variations from the times, loads, and speeds 
 of best effect, the total effect may be taken as varying 
 with those variations. 
 
 In ascending inclines, the work may be taken as 
 approximately increasing with the inclination and at 
 a rate proportional to the ratio i -[- {a -^ \ 1.5°) ; since 
 
8o 
 
 THE ANIMAL AS A MACHINE. 
 
 the work performed in horizontal carriage of burdens 
 is nearly equivalent to raising the total weight one 
 foot in five, for which we have sin-i-i-:^ 11.5°. Xhe 
 art of securing best results in the use of animals draw- 
 mg loads in vehicles of various sorts is that of so pro- 
 portioning load, line of pull, weight of vehicle, and 
 speed of travel as to permit the animal to take its 
 natural gait and best total effort under load, this 
 effort being measured at the traces. Obviously, the 
 lighter the wagon or cart it is found practicable to em- 
 ploy for the proposed load the better. Also, the larger 
 the loads transported in one vehicle the better, as a 
 rule ; and thus, in all large operations, heavy loads in 
 comparatively light carriages, and drawn by numbers 
 of animals, give most economical results. As inclines 
 decrease the useful work in rapid proportion with 
 their rise, the production of level and smooth roads is 
 an essential to economy. This is illustrated in the 
 case of railways, where enormous sums are expended 
 to insure straight, level, and smooth tracks. For men 
 the treadmill, and for animals well-constructed '^ horse- 
 powers," embodying the same principles of construc- 
 tion, give highest efficiency as measured by the work 
 performed per day, in foot-pounds or kilogrammetres. 
 Walking up a moderate incline carrying only the 
 weight of the body is the most easy and natural of all 
 methods of employing its power. This system is 
 capable, however, of but very limited appHcation in 
 ordmary industrial work. It is oftenest seen in use in 
 threshing-machines and other agricultural apparatus. 
 
 26. In Selection and Care in the employment of 
 men and animals, the engineer is compelled to regard 
 them as machines, to be selected with careful reference 
 
THE ANIMAL AS A MOTOR. 8 1 
 
 to the exact requirements of the work proposed to be 
 done, to be handled in such manner as to give him 
 maximum returns for his expenditures, and to be made 
 to produce large commercial results throughout the 
 period of their use. Fortunately, a wise regard of 
 these principles results in giving the man or the animal 
 highest health, in insuring him against overwork, and 
 in encouraging high spirits by the supply of good food, 
 permitting ample allowance for sleep and rest, and 
 prolonging the period of useful life. In exceptional 
 cases the animal machine must be exposed to deleteri- 
 ous influences, overstrain, or liability to serious acci- 
 dent ; but these cases can usually be made extremely 
 rare by intelligent engineering, and, in the case of 
 man at least, the individual so exposed receives what 
 is thought by him satisfactory compensation for the 
 risks so taken. 
 
 In the selection of the man or animal for a specified 
 work, the wise and experienced engineer, or his con- 
 tractor, looks for light, active, spirited creatures for 
 light work, heavy and powerful, though slow, animals 
 for heavy work, and can usually find just that com- 
 bination of qualities of body, intelligence, and spirit 
 which his experience teaches him are best for the 
 specified purpose. The racehorse, the roadster, the 
 hackney, and the draught-animal all have their special 
 parts to perform. Neither can satisfactorily do the 
 work of the other ; and the same is true of man, 
 whether performing purely manual labor, working at a 
 trade, or taxing his mind in the direction of an indus- 
 trial army or otherwise. For every sort of task there 
 is to be found a kind of man specially and peculiarly 
 adapted to its successful accomplishment. Not only 
 
82 THE ANIMAL AS A MACHINE. 
 
 individuals, but families, tribes, and even races, adapt 
 themselves, through natural constitution and peculiar 
 characteristics of body and mind, to special kinds of 
 work. Among the best species, races, tribes, or 
 families, individuals may always be found especially 
 well fitted to perform a specified work ; and among 
 such individuals, the age, state of health, conditions of 
 environment, may produce serious differences at 
 different times. All such variations are noted by the 
 engineer and serve as the basis of his judgment in 
 apportioning work, in assigning duties, and in deter- 
 mining compensation. 
 
 The work once assigned, the person in charge 
 should be expected not only to see that the conditions 
 of best effect are adhered to, strictly and continuously, 
 but to arrange the times and methods of serving 
 meals, the character, amount, and method of prepara- 
 tion of the dietary with a view to insuring the best 
 possible conversion of its potential energy into work 
 and at minimum cost consistent with highest results. 
 Even satisfaction with the bill-of-fare, by promoting 
 appetite and digestion, is an element of success, with 
 animals as well as with men. Periods of rest should 
 be so arranged that the food may be taken neither 
 when fatigue nor immediately succeeding labor may in- 
 terfere with its digestion. Two meals, even one hearty 
 and well-digested meal per day is sometimes found, 
 for this reason, better, on the whole, than a larger 
 number resulting in impaired digestion and defective 
 nutrition. In hot climates, particularly, natives are 
 observed often to be well satisfied with a single meal, 
 taken after a hard day's work ; the precaution being 
 observed to secure an hour of complete rest before 
 
THE ANIMAL AS A MOTOR, 83 
 
 taking it. Hard-worked stage-horses, fed an hour be- 
 fore going upon the road in the morning with a warm 
 mixture of cut hay and corn-meal, moderately wet, 
 and fed again after their rest on coming in at night, 
 have been found to do the season's work better than 
 when given a third meal at noon. The meal should, 
 in all cases, consist of nutritious food of proper com- 
 position, and in ample quantity to satisfy the appetite, 
 without permitting excess. 
 
 No less essential in securing the most that can be 
 obtained from the working man or animal is the pro- 
 vision of suitable clothing and housing. Weather- 
 tight, warm, thoroughly comfortable, and yet well- 
 ventilated stables are essential to highest economy in 
 the employment of animals ; and the same care, pre- 
 cisely, is demanded in providing for men, with the 
 additional requirement that everything within reason 
 that shall conduce to content and cheerfulness, high 
 spirits, ambition, and an inclination to do their best 
 work should be conscientiously provided. 
 
III. 
 
 FINAL DEDUCTIONS.* 
 
 27. Our Progress, whether in the direction of indus- 
 trial improvement or of intellectual growth, depend, 
 the first mainly, the second largely, upon the extent 
 and the success of man's utilization of the four great 
 natural forces, or *' energies," as the man of science 
 calls them : heat, light, electricity, mechanical or dyna- 
 mic power. Civilization is based upon their application 
 to the purposes of humanity in the world of matter; 
 intellectual and even moral progress is advanced by 
 that steady march of improvement which, in modern 
 times especially, has so constantly promoted the ma- 
 terial welfare of the world, and has thus given leisure 
 for that employment of the mind in higher work which 
 is the essential prerequisite to either intellectual or 
 moral elevation. 
 
 The greatest of all our problems to-day is thus that 
 of making this utilization of the forces of nature more 
 general, more efficient, and more fruitful. Could the 
 engineer, to whom all this work is intrusted, find a way 
 of producing steam-power at a fraction its present 
 cost ; could he transform heat energy directly and 
 without waste into dynamic ; could he find a method 
 of evolution of light without that enormous loss now 
 
 * From The Forum, Sept. 1892 : " The Great Problems of Science," 
 by R. H. Thurston. 
 
 84 
 
FINAL DEDUCTIONS. 85 
 
 inevitable in the form of accompanying heat ; could 
 he directly produce electricity, without other and lost 
 energy, from the combustion of fuel — could he do 
 these things to-day, the growth of all that is desirable 
 to mankind and the advancement of all the interests 
 and powers of the race would be inconceivably ac- 
 celerated. Moral sentiments, logical power, inventive 
 genius, capacity for accomplishing all the grander tasks 
 of civiHzation, develop together. All gain and retain 
 existence through the mysterious power, possessed by 
 all, of transforming and utilizing those original natural 
 energies coming to us all alike from the central sun, 
 and to the central sun from initial chaos and a diffused 
 universe. Every motion and every power of each and 
 all is due to conversion of these primary energies for 
 a specific purpose and in a specific manner. 
 
 The engineer, to whom is confided this duty of 
 utilizing all the forces of nature for the benefit of his 
 fellows, has, however, now apparently reached a point 
 beyond which he can see but little opportunity for 
 further improvement, except by slow and toilsome and 
 continually limited progress. He seems to have come 
 very nearly to the limit of his advance in the directions 
 which have, up to the moment, been so fruitful of 
 result. His steam-engine is doing nearly the best that 
 can be done, so far as he can see, in the conversion 
 of heat into power ; light is produced through the 
 steam-engine and the dynamo-electric machine about 
 as efficiently as he can hope to obtain it by known 
 methods; heat is obtainable for his thousand purposes, 
 economically at least, only by the combustion of his 
 rapidly disappearing stores of fuel laid by in the past 
 millenniums for his use during a brief life on the globe, 
 
86 THE ANIMAL AS A MACHINE. 
 
 and without visible substitute when they shall have 
 been exhausted ; and civilization, the life of the race, 
 dependent upon our coal-beds, is only assured of 
 ultimate and, on the geologist's scale of time, early 
 extinction ; unless, indeed, again consulting nature 
 and studying the lessons of life, as we have so often 
 profitably done before, we can learn of new ways of 
 availing ourselves of existing forms of energy in 
 nature, or of enormously improving our methods and 
 reducing those wastes which are now so frightful, as 
 judged from the standpoint of both the engineer and 
 the man of science. Whether we can expect or even 
 hope to accomplish the first of these tasks is extremely 
 doubtful, not to say absolutely improbable ; that we 
 may possibly succeed in the second may be less un- 
 likely. In any case, our only recourse is the same 
 method which has brought us all that we now possess : 
 scientific research and the study of nature's own 
 methods. 
 
 28. What we are to Seek is, first, a method of 
 producing, directly or by modification of other ether- 
 vibrations, just that sort of ether -wave which we 
 require, in the form of heat, light, or electricity, of 
 exactly defined rate and amplitude of vibration ; 
 secondly, the complete transformation of either or all 
 forms into mechanical power, into '' dynamic " energy. 
 It is easy to say and usually is safe to assert that what 
 has been done may be again done ; what is accom- 
 plished to-day in nature may be, in a similar manner 
 or by parallel methods, performed by man. Nature 
 accomplishes many of the tasks that man is about 
 attempting, and has been holding up to him the 
 solution of his problems throughout the ages. It is 
 
FINAL DEDUCTIONS. 87 
 
 for him to solve her riddles and thus to obtain power 
 at a fraction of its present cost ; prolong the life of 
 the race indefinitely ; secure light, isolated from heat, 
 and in many times the quantity for a given amount of 
 labor now expended ; and produce electricity without 
 loss and directly, instead of, as at present, through the 
 intervention of heat-engines with their now enormous 
 wastes. Human progress depends upon the ability of 
 mankind to do more work, and to accomplish greater 
 tasks, to supply the necessaries of life with less expen- 
 diture of time and strength, thus to secure leisure for 
 the production of the comforts and the luxuries that 
 give modern society its characteristics, and to insure 
 that leisure for thought, invention, intellectual de- 
 velopment of every kind, which still more strikingly 
 characterize the highest civilization. In all this, only 
 the application of the forces of nature without waste 
 and the complete subjection of all its energies can 
 give maximum result. 
 
 It is now well known that the heat-engines, whether 
 steam, gas, hot air, or ether, only utilize a fraction of 
 the power latent in their fuel, and that this fraction, 
 as a maximum, in even an ideally perfect engine, is 
 measured by the division of the range of temperature 
 through which they expand their '* working fluids " by 
 the " absolute " temperature of the fluid as supplied 
 to the engine ; that is, a temperature measured from 
 a point about 460°, on the Fahrenheit scale, below the 
 Fahrenheit zero. This fraction, we have learned, is, 
 in the case of the modern steam-engine, usually 
 between one fourth and one half ; while the actual 
 performance of our engines falls to one fourth or one 
 half this ideal maximum, in the ordinary and best 
 
«« THE ANIMAL AS A MACHINE. 
 
 engines, respectively.* The engine fully utilizing, 
 ideally, but two and one half pounds of steam and 
 one fourth of a pound of coal per horse-power per 
 hour practically demands six to eight times this 
 amount, even when of the best construction ; while 
 the average engine probably utilizes but one pound in 
 ten, and often but one in twenty, wasting from ninety 
 to ninety-five per cent of all the heat from its furnaces. 
 The gas-engine gives higher thermodynamic perform- 
 ance than the steam-engine ; but it compensates this 
 advantage by loss, through a ''water-jacket," of one- 
 half of all the heat that it should completely transform 
 into useful work.f No method is yet discovered 
 of imitating nature in direct conversion of heat 
 into other forms of energy without waste ; and our 
 production of light, in our most recent and most 
 wonderful inventions, involves the same waste by the 
 intermediate use of the heat-engine for primary trans- 
 formation of heat into mechanical energy, in turn to 
 be converted, with great efficiency, into electricity, 
 thence to be once more transformed, with great waste 
 again, into light. The direct evolution of light, 
 purely, or of electricity alone and without loss, from 
 fuel oxidation, though it is constantly performed by 
 nature, is as yet beyond the power of man. Could 
 these problems of life be solved, power and light 
 would cost us but a small fraction of their cost to-day ; 
 and the exhaustion of our coal-beds would be deferred 
 
 *" Steam and its Rivals," R. H. Thurston: Forum, May 1888, 
 p. 34T. Also "Manual of the Steam-engine," vol. i. (New York, 
 J. V^iley & Sons, 1890). 
 
 f " Last Days of the Steam-engine," R. H. Thurston: North 
 American Review^ July 1889. 
 
FINAL DEDUCTIONS. 89 
 
 thousands of years. Were grander problems ever 
 presented or nobler prizes ever offered the man of 
 science than these ? Nature solved them in the 
 earliest days of the earth's history ; it begins to seem 
 probable that man may find a way to penetrate the 
 secrets and solve the problems of life and vitality. 
 All that he seeks may be evolved from the mysteries 
 and lessons of life. 
 
 29. The Living Body is a machine in which the 
 "law of Carnot," which asserts the necessity of waste in 
 all thermodynamic processes and in every heat-engine, 
 and which shows that waste to be the greater as the range 
 of temperature worked through by the machine is the 
 more restricted, is evaded ; it produces electricity with- 
 out intermediate conversions and losses ; it obtains 
 heat without high-temperature combustion, and even, 
 in some cases, light without any sensible heat. In other 
 words, in the vital system of man and of the lower 
 animals nature shows us the practicability of directly 
 converting any one form of energy into any other, 
 without those losses and unavoidable wastes character- 
 istic of the methods the invention of which has been 
 the pride and the boast of man. Every living creature, 
 man and worm alike, shows him that his great task is 
 but half accomplished ; that his grandest inventions are 
 but crudest and remote imitations ; that his best work 
 is wasteful and awkward. Every animate creature is a 
 machine of enormously higher efficiency as a dynamic 
 engine than his most elaborate construction as illus- 
 trated in the 30,000 horse-power engines of the " Cam- 
 pania" or the '' Lucania," or in the most powerful 
 locomotive. Every gymnotus living in the mud of a 
 tropical stream puts to shame man's best effort in the 
 
90 THE ANIMAL AS A MACHINE. 
 
 production of electricity ; and the minute insect that 
 flashes across his lawn on a summer evening, or the 
 worm that lights his path in the garden, exhibits a sys- 
 tem of illumination incomparably superior to his most 
 perfect electric lights. 
 
 Nature in each of these cases converts the energy of 
 chemical union, probably of low-temperature oxidation, 
 into just that form of energy, whether mechanical or of 
 a certain exactly defined and required rate of ether- 
 vibration, that is best suited to the intended purpose, 
 and without waste in other force, utilizing even the 
 used-up tissue of muscle and nerve for the production 
 of the warmth required to retain the marvellous ma- 
 chine at the temperature of best efficiency, whatever 
 the environment, and exhaling the rejected resultant 
 carbonic-acid gas at the same low temperature. Here 
 is nature's challenge to man ! Man wastes one fourth 
 of all the heat of his fuel as utilized in his steam-boiler, 
 and often ninety per cent as used in his open fire- 
 places ; nature, in the animal system, utilizes substan- 
 tially all. He produces light by candle, oil-lamp, or 
 electricity, but submits to a loss of from one fifth to 
 more than nine tenths of all his stock of available 
 energy as heat ; she, in the glowworm and firefly, pro- 
 duces a lovelier light without waste measurable by our 
 most delicate instruments. He throws aside as loss 
 nine tenths of his potential energy when attempting to 
 develop mechanical power ; she is vastly more econom- 
 ical. But in all cases her methods are radically different 
 from his, though they are as yet obscure. Nature con- 
 verts available forms of energy into precisely those other 
 forms which are needed for her purposes, in exactly the 
 right quantity, and never wastes, as does invariably the 
 
FINAL DEDUCTIONS, 9 1 
 
 engineer, a large part of the initial stock by the pro- 
 duction of energies that she does not want and cannot 
 utilize. She goes directly to her goal. Why should 
 not man ? He has but to imitate her processes. 
 
 Mysterious as seem these processes and methods, 
 however, and wonderful as seem their results when 
 compared with the crude ways of the engineer and 
 the man of science, we at least know something of 
 them, and are even familiar with many facts relating to 
 them. The facts are these : Every living creature 
 throughout the animal kingdom is a machine which 
 takes into its internal furnace, or whatever it may 
 prove to be, its fuel, its " food," composed of vegetable 
 matter or, like the body receiving it, itself directly de- 
 rived from vegetation ; and by a chemical process in 
 what the chemist calls the " wet way " it consumes this 
 food, the resulting products of this chemical action being 
 such as, dissolved in the blood, may be converted into 
 brain, nerve, muscle, and fat ; and by later combustion 
 and transformations at low temperature it may produce 
 heat certainly, electricity probably, often light, and 
 always mechanical power. The composition of this 
 fuel is known to be principally familiar chemical ele- 
 ments mingled with the rarer in minute proportions. 
 The hydrocarbons, water, and a little lime, phosphorus, 
 sulphur, and other minerals, such as iron, constitute 
 the food of all living creatures. 
 
 Every process involved is carried on at '' blood-lieat " 
 in the higher animals, and at much lower temperatures 
 in the "■ cold-blooded " creatures ; and all parts of the 
 system are retained at substantially the same tempera- 
 ture at all times. All heat is thus the result of low- 
 temperature combustion ; all light and electricity are 
 
92 THE ANIMAL AS A MACHINE. 
 
 evolved at a constant low point on the scale, and these 
 energies are converted into new forms, or into dynamic 
 energy, and applied to the performance of work with- 
 out variation of that temperature. That heat is pro- 
 duced is a matter of constant experience and observa- 
 tion, and we throw off more as we work harder, whether 
 with mind or body, and as we move more rapidly. 
 That this heat, so far as converted into other energies 
 by the body, must be so converted at a sensibly con- 
 stant temperature is obvious from the fact that the 
 change goes on in a mass of circulating fluids ; that 
 this proves that the conversion is not thermodynamic, 
 but is due to some entirely different and unknown 
 method, is equally evident to the engineer, who under- 
 stands that only so could the "law of Carnot " be 
 evaded. That this action is possibly electrodynamic is 
 indicated by the fact that electric currents traverse the 
 system, and that we may at any moment compel the 
 muscles to do work by the application of a current 
 from an external source. 
 
 30. Of the Methods of Production of Energies 
 in the body, we know as yet absolutely nothing ; but 
 we do know that electricity may be produced in large 
 quantity, and at '' high pressure," as the electrician 
 says, as illustrated by the torpedo and the gymnotus 
 or electric eel ; and the anatomist knows the mechani- 
 cal structure of the organs from which it is evolved, 
 though he is ignorant of the processes therein con- 
 ducted. We also know that the best currents for 
 electrodynamic operations are those of low intensity, 
 such as are easiest of control and insulation in the 
 body. By analogy with the other methods of trans- 
 formation, we may presume that the source of this 
 
FINAL DEDUCTIONS. 93 
 
 vital fluid in the animal is low-temperature combustion 
 or other chemical action, and that a system of direct 
 conversion is there in operation. 
 
 Scientific men are somewhat more familiar with the 
 case of the firefly, curiously enough ; that is to say, 
 the production of light without heat, as well as the 
 transformation of energies resulting in the economical 
 production of heat and power in the animal system. 
 It has long been known that certain chemical com- 
 pounds, notably fats containing sulphur and phospho- 
 rus, may be burned at exceedingly low temperatures, 
 with an evolution of a mild light almost or quite 
 entirely free from heat. Some such compounds are 
 found in nature, and the chemist has artificially pro- 
 duced others. He finds that he may at will produce, 
 in some cases, slow and cold light-production or rapid 
 and heat-producing oxidation. Numerous experiments 
 upon the firefly and the glowworm indicate that theirs 
 is a light thus obtained. This so-called "■ phosphores- 
 cence" is seen in many insects, worms, fishes, and 
 mollusks, and even in vegetable and mineral matter. 
 For a century this investigation has been in progress, 
 and it is well established that the low-temperature 
 combustion of a peculiar substance, given form in the 
 body of the firefly, for instance, by peculiar organs 
 specially constituted for that purpose, results in the 
 production of light without heat. This has been most 
 recently and most conclusively proved by Messrs. 
 Langley and Very, who show by actual measurement 
 with the Langley " bolometer," an instrument capable 
 of measuring even the heat received from the moon, 
 that " insect light " is accompanied by approximately 
 one four-hundredth part of the heat which is ordinarily 
 
94 THE ANIMAL AS A MACHINE. 
 
 associated with the radiation of flame of the luminous 
 quality of those familiar to all of us. Thus '* nature 
 produces this cheapest light at about one four-hundredth 
 part of the cost of the energy which is expended in the 
 candle-flame and at but an insignificant fraction of the 
 electric light or the most economic light which has yet 
 been devised." Many deep-sea fishes and nnmberless 
 animalcules exhibit a solution of this problem. 
 
 31. The Advantage to be hoped for from the sub- 
 stitution of the economical ways of nature for the 
 wasteful ways of man may be imagined from the fol- 
 lowing facts: Experiments by Mr. Merritt, in the Cor- 
 nell University laboratories, have shown the wastes of 
 the incandescent electric lamp to be from 93I- to 99I- 
 per cent, according to intensity of current ; while Mr. 
 Nakano's tests, in the same place, of the arc lamp give 
 a waste of 95 to 84 per cent. The insect wastes almost 
 nothing. But even now the electric light has ten or 
 fifteen times the efficiency of the oil-lamp, and is still 
 better as compared with the candle. Professor Lang- 
 ley found the common gas-burner to waste 99 per cent 
 of the developed energy of combustion. His fireflies 
 were more efficient in the proportion of one to thousands. 
 The six millions of tons of coal supposed to be con- 
 cealed in the earth, at our present rate of consumption, 
 if employed for power-production, would supply about 
 fifteen thousand millions of horse-power for twelve 
 thousand years ; but could we discover and employ 
 nature's methods and gain in such proportion as is 
 indicated above, we might feel sure that all the wants 
 of the race would be supplied as long as the earth 
 should continue the possible abode of man. Years 
 ago it was remarked in an inaugural address as presi- 
 
FINAL DEDUCTIONS. 95 
 
 dent of the '' American Society of Mechanical En- 
 gineers " *: 
 
 " I have sometimes said that the world is waiting for 
 the appearance of three great inventors, yet unknown, 
 for whom it has in store honors and emoluments far 
 exceeding all ever yet accorded to any one of their 
 predecessors. The first is the man who is to show 
 how, by the consumption of coal, we may directly pro- 
 duce electricity, and thus, perhaps, evade that now 
 inevitable and enormous loss that comes of the utiHza- 
 tion of energy in all heat-engines driven by substances 
 of variable volume. Our electrical engineers have this 
 great step still to take, and are apparently not likely 
 soon to gain the prize that will reward some genius yet 
 to be born. The second of these greatest of inventors 
 is he who will teach us the source of the beautiful soft- 
 beaming light of the firefly and the glowworm, and 
 will show us how to produce this singular illuminant 
 and to apply it with success practically and commer- 
 cially. This wonderful light, free from heat and from 
 consequent loss of energy, is nature's substitute for the 
 crude and extravagantly wasteful lights of which we 
 have, through so many years, been foolishly boasting. 
 The dynamo-electrical engineer has nearly solved this 
 problem. Let us hope that it may be soon fully solved, 
 and by one of those among our own colleagues who are 
 now so earnestly working in this field, and that we may 
 all live to see him steal the glowworm's light and to see 
 the approaching days of Vril predicted so long ago by 
 Lord Lytton. The third great genius is the man who 
 is to fulfil Erasmus Darwin's prophecy closing the 
 stanza : 
 
 * Transactions "A. S. M. E.," November 1881, R. H. T. 
 
96 THE ANIMAL AS A MACHINE. 
 
 " ' Soon shall thy arm, unconquered steam, afar 
 Drag the slow barge or drive the rapid car, 
 Or on wide-waving wings expanded bear 
 The flying chariot through the fields of air ' " 
 
 And even this latest of the mechanic's triumphs, al- 
 ready known to present far less difficulty than was 
 formerly supposed, will attain highest success only 
 when nature's methods of energy-transformation are 
 discovered and adopted. 
 
 Should the day ever come when transformations of 
 energy shall be made in nature's order, and when 
 thermo-electric changes shall be a primary step toward 
 electrodynamic application to purposes now universally 
 attained only by the unsatisfactory processes of thermo- 
 dynamics as illustrated in our wasteful heat-engines, 
 the engineer, following in his work the practice of 
 nature, which has been so successful throughout the 
 life of the animal kingdom, will find it easy to drive 
 his ship across the ocean in three days ; will readily 
 concentrate in the space now occupied by the engines 
 of the " Majestic " a quarter of a million horse-power; 
 will transfer the 3,000,000 horse-power of Niagara to 
 New York, Boston, Philadelphia, to be distributed to 
 the mills, shops, houses, for every possible use, furnish- 
 ing heat, light, and power wherever needed ; and may 
 possibly do quite as much for the benefit of mankind 
 by breaking up the modern factory system and distrib- 
 uting labor in comfortable quarters as by this reduc- 
 tion of costs of products to the consumer. One of the 
 many difficulties in the way of successful navigation of 
 the air is known to be that of securing some propelling 
 instrument that shall not weigh more than about ten 
 pounds to the horse-power. Could we evade Carnot's 
 
FINAL DEDUCTIONS. 97 
 
 law by complete energy-transformation, we could to- 
 day build engines of over 400 horse-power to the ton 
 weight, and that obstacle would be out of our way. 
 Could we completely transform heat or mechanical 
 power into light, a resulting advantage would also be 
 the reduction of the whole system of light-producing 
 machinery in weight and bulk in corresponding degree. 
 These gains would be observed in innumerable direc- 
 tions. 
 
 32. Costs. — On the other hand, nature in all her 
 transformations makes use of chemical processes and 
 organic and complex compounds that may prove to be 
 too costly as substitutes for the fuels, though the latter 
 are subject to present wastes ; and thus the question 
 of dollars and cents, always controlling, comes in to 
 confuse the wisest of scientific men. However that 
 may be, these problems must always afford instructive 
 lessons to the student of the mysteries of nature ; and 
 the bare possibility that by following her methods he 
 may find ways of so enormously benefiting his fellow- 
 man and of adding so greatly to the comfort, the 
 pleasure, the safety, and the opportunities of the race, 
 must be quite sufficient to stimulate every young 
 aspirant for fame and every lover of research to strive 
 to achieve some one or all of these solutions of the 
 grandest scientific problems that remain unsolved. It 
 seems more than probable that it is to the mysteries 
 and lessons of life that the chemist, the physicist, the 
 engineer, must turn in seeking the key that shall un 
 lock the still unrevealed treasures of coming centuries. 
 These constitute nature's challenge to the engineer.