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 UNIVERSITY OF CALIFORNIA 
 AT LOS ANGELES
 
 THE 
 
 Steam Engine and the Indicator: 
 
 THEIR ORIGIN AND PROGRESSIVE DEVELOPMENT; 
 
 INCLUDING THE 
 
 MOST RECENT EXAMPLES OF STEAM AND GAS MOTORS, 
 
 TOGETHER WITH 
 
 THE INDICATOR, ITS PRINCIPLES, ITS UTILITY, 
 AND ITS APPLICATION. 
 
 BY 
 
 WILLIAM BARNET LE VAN, 
 
 MEMBER OF THE FRANKLIN INSTITUTE AND OF THE AMERICAN SOCIETY OF 
 MECHANICAL ENGINEERS. 
 
 Illustrated by 2O5 Engravings chiefly of Indicator-Cards. 
 
 PHILADELPHIA: 
 HENRY CAREY BAIRD & CO., 
 
 INDUSTRIAL, PUBLISHERS, BOOKSELLERS, AND IMPORTERS, 
 810 WALNUT STREET. 
 
 LONDON: 
 
 E. & F. N. SPON, 125 STRAND. 
 l8Q2.
 
 Copyright by 
 WILLIAM BARNET LE VAN, 
 
 PRINTED AT 
 
 COLLINS PRINTING HOUSE, 
 
 PHILADELPHIA, f. s. A.
 
 -J 
 
 PREFACE. 
 
 . 
 
 THE author has endeavored, in the following pages, to explain 
 how, economically, to make use of steam in an engine, and has 
 also discussed the most important principles regarding the theory 
 and action of the steam engine, with a fair degree of techni- 
 cality; and yet so as to be intelligible to the ordinary student. 
 He has made an attempt to state the principles laid down by 
 theoretical writers: Clausius, Tyndall, Rankine, Clark, Max- 
 well, Colburn, Northcott, Graham, Nystrom, and others, in 
 such a form as to be useful to practical engineers, and to test, 
 by these principles, the modes of working which have been 
 found, in practice, most advantageous. 
 
 The early chapters refer especially to the history of the steam 
 engine, and to the theory of the action of steam in the cylinder 
 of a steam engine, and the succeeding ones to the application 
 of the theory in practice. 
 
 Having felt personally the want of more practical informa- 
 tion on the subject than is contained in existing works, it has 
 been the aim of the writer to supply such want, and to enable 
 those who have not the opportunity of making experiments to 
 gain a more intimate knowledge of THE INDICATOR. And it is 
 hoped that the directions here given for the practical applica- 
 tion of this instrument will at the same time give the volume 
 a considerable degree of interest to those engineers who are 
 conversant with its ordinary working, but lack a knowledge of 
 the principles involved. 
 
 He gladly acknowledges the assistance afforded by the prac- 
 tical treatises of Main and Brown, Stillman, Porter, Salter, 
 Graham, and others, the Engineering periodicals, and above all, 
 by the late John W. Nystrom, who kindly furnished him with a 
 copy of his new tables on the properties of Water and Steam, 
 and also with considerable matter bearing on the Indicator. 
 
 He is also under obligations to Messrs. Egbert P. Watson & 
 (Hi) 
 
 21C361 
 383
 
 iv PREFACE. 
 
 Son, publishers of The Engineer, New York, for the use of indi- 
 cator cuts. 
 
 He has had an experience of over thirty years with the Indi- 
 cator, and the majority of the diagrams here given were taken 
 by himself. 
 
 The tables given in the volume, will be found very useful. 
 By their means almost all calculations connected with the use 
 of steam may be solved by any one who is acquainted with the 
 first four rules of arithmetic. 
 
 WILLIAM BARNET L,EVAN. 
 
 Philadelphia, July 25, 1889. 
 
 3607 Baring Street.
 
 CONTENTS. 
 
 CHAPTER I. 
 
 INTRODUCTION. 
 
 PAGB 
 
 What the steam engine is ; Work done by the steam ; Physical constitution 
 of heat; What heat is the product of 17 
 
 Dynamics ; Definition of dynamics ; Principles of the dynamical branch 
 of mechanics; Various uses of the term " energy" 18 
 
 Energy, proper definition of 19 
 
 CHAPTER II. 
 
 WHO INVENTED THE STEAM ENGINE? 
 
 Translation of Hero's book by Bennet Woodcroft ; Hero not an inventor, 
 but the power of steam was understood in his time ; First steps in the 
 invention ; Hero's fountain and other ingenious machines 20 
 
 Ignorance of the inventors in ancient times of the principles governing 
 the action of such machines, and of the true nature of steam ; Loss of 
 knowledge and progress by reason of the false methods and philosophy 
 of the ancients ; The aeolipile described by Vitruvius 21 
 
 The aeolipile, illustrated and described ; Illustration of a similar apparatus 
 described by Hero 22 
 
 Use of the pressure of vapors by the Egyptian priests in their mysteries ; 
 Giovanni Batista Porta's translation of Hero's "Spiritalia," with addi- 
 tional description of apparatus ; Magic lantern and camera obscura said 
 to be inventions of Porta 23 
 
 Porta's machine for raising water by steam pressure illustrated and de- 
 scribed ; Porta's description of the action of condensation in producing 
 a vacuum 24 
 
 The first recorded notice of the power of steam as shown by an apparatus 
 used by Athemius A. D. 540 ; Exhibition of a boat propelled by steam 
 at Barcelona, June 17, 1543, by Glasco de Garoy ; Description of a ma- 
 chine for raising water by the expanding power of steam by Salomon de 
 Caus, 1615 ; General knowledge of the expansive properties of steam 
 before the I7th century ; The actual steam engine an invention of the 
 1 7th century; First application of steam power on a large scale by the 
 Marquis of Worcester about A. D. 1650, and description of his apparatus. 25 
 
 Apparatus invented, in 1697, by Savery, used for raising water at Vaux- 
 hall, London, and at Raglan Castle ; No real progress in the knowledge 
 or apprehension of the fundamental principles of steam from Archimedes 
 
 (v)
 
 vi CONTENTS. 
 
 FAOK 
 
 to De Caus ; Commencement of real progress with the appearance of 
 men like Descartes, Kepler and Galileo ; Weight and pressure of the at- 
 mosphere proved, in 1643, by Torricelli 26 
 
 Otto von Guericke's air-pump and hemispheres ; Comparison of progress 
 before and after the 1 7th century; Pascal's rejection and final accepta- 
 tion of Torricelli's position; His experiment, September 20, 1646, on the 
 summit of the Puy de Dome, at Clermont 27 
 
 Torricelli's experiments and Guericke's invention of the air-pump the true 
 germ of the steam engine ; Difference in the significance between Torri- 
 celli's tube and the aeolipile and other previous ingenious devices ; First 
 suggestion, in 1690, by Papin, of the condensation of steam for the pro- 
 duction of a vacuum ; Extent of contraction of steam under ordinary 
 pressure 28 
 
 Recognition of the advantages of the use of steam by Papin; The "at- 
 mospheric engine" the first engine the principles of whose action are 
 comprehended; Papin's manner of condensing steam and forming a 
 vacuum applied, in 1698, by Savery ; Defects of Savery's engine ; Appli- 
 cation of the cylinder and piston to the purposes of steam power, in 1705, 
 by Newcomen and Cawley, of Dartmouth, England; Description of their 
 engine 29 
 
 Savery's engine an "atmospheric engine;" Accidental discovery of jet 
 condensation; Origin of the "plug frame" and valve gear of to-day 
 due to a device of the boy Humphrey Potter 30 
 
 First attempts in America to propel boats by steam made by John Fitch of 
 Windsor, Conn., and James Rumsey of Maryland; Successful invention 
 and construction of a steamboat, in 1789, by Nathan Read of Western 
 (now Warren), Mass 31 
 
 Invention and construction by Mr. Read of a portable furnace tubular 
 boiler, and application by him, Feb. 8, 1790, for a patent on a locomotive 
 steam carriage ; Mr. Read's various discoveries as set forth by a recom- 
 mendation from a select committee of the American Academy of Arts 
 and Sciences ; Mr. Read's just claims to being the original inventor of 
 the successful application of steam power for locomotion compared with 
 those of his predecessors 32 
 
 Historical data in reference to the application of steam power for pumping 
 engines; Catalogue of Watt's discoveries; "Jet condenser" and "sur- 
 face condenser" 33 
 
 The "real steam engine" as distinguished from the "ideal engine;" "Cyl- 
 inder condensation;" "Indicator;" "Fly-ball governors;" "Copying 
 press" . . '. 34 
 
 The laws which are the key to the whole problem of converting the work 
 of combustion into dynamic power, discovered by Watt ; Cornish pump- 
 ing engines and explanation of a "hundred millions of duty" 35 
 
 Further historical data in reference to the application of steam power for 
 locomotion prior to Mr. Read ; The successful use of steam as a propel- 
 ling power in navigation rendered possible by the invention of the rotary 
 
 steam engine by Watt, and of the tubular boiler by Read 36 
 
 General Stevens's experiments in steam navigation; the invention of the
 
 CONTENTS. vii 
 
 PAGB 
 
 tubular boiler erroneously attributed to him; Chancellor Livingston's 
 projects with steam on the Hudson ; Fulton's first attempt at steam navi- 
 gation ; Launch and first successful trip of the "Clermont;" First steam- 
 ship to cross the ocean 37 
 
 The ' ' Savannah ' ' the first steamship ever built to cross the ocean ; An- 
 nouncement of the intended attempt in the London Times, May u, 1819; 
 Ludicrous declaration of a distinguished scientist 38 
 
 The American steamer regarded with suspicion by the English anthorities. 39 
 
 The Savannah at Copenhagen, Stockholm and St. Petersburg ; Loss of the 
 Savannah 4 
 
 Lesson taught by the steam engine ; Tribute to Watt 4 1 
 
 CHAPTER III. 
 
 HEAT AND WORK. 
 
 Materiality of heat discredited by the earliest philosophers ; Rumford's, 
 Mayer's and Joule's experiments ; Dynamical value or mechanical equiv- 
 alent of heat ; Science of thermodynamics ; Consumption of coal per 
 hour per horse power, of a condensing engine ... 42 
 
 Units of heat generated by a pound of carbon ; What an indicated horse- 
 power means ; Water ; Investigations of water by Priestley, Cavendish 
 and Lavoisier 43 
 
 Specific gravity of ice; Latent heat of liquefaction; Maximum density of 
 water ; Vaporization of water ; Dalton's experimental results on evapora- 
 tion below the boiling temperature 44 
 
 Boiling point of water ; Vaporous condition of water ; Temperature of the 
 gaseous state of water ; Specific heat of water ; Boiling 45 
 
 Philosophy of boiling and generation of steam ; Saturated and super- 
 heated steam 46 
 
 Steam ; Definition of steam ; Quantity of heat required to convert a given 
 quantity of water at 212 F. into steam 47 
 
 Various conditions of water ; Density of steam ; Specific gravity of steam ; 
 Weight of air, steam and water 48 
 
 Atmospheric pressure ; Measurement of pressure ; Vapors ; Definition of 
 vapor ; Liquefaction of solids ; Formation of vapors 49 
 
 Saturated and unsaturated vapors ; Coefficient of expansion of super- 
 heated steam ; Steam or aqueous vapor ; Evaporation of water ; Circum- 
 stances on which the weight of water evaporated depends 50 
 
 Temperature of the boiling point, on what it depends ; Ideal zero of aque- 
 ous vapor; Latent heat of steam ; Explanation of latent heat 51 
 
 Work accomplished by latent units of heat ; Volume of water ; Latent and 
 total heat in water from 32 degrees 52 
 
 Temperature of boiling liquid ; Condensation of steam ; Wet and dry steam ; 
 Throttling of steam 53 
 
 Low and high pressure steam ; Proper terms for engines ; Absolute pres- 
 sure ; Ways of expressing the elastic force of steam ; Effect due to 
 vacuum 54 
 
 Measurement of absolute pressure of steam ; Steam gages and vacuum
 
 yiii CONTENTS. 
 
 PAGE 
 
 gages; Difference between a non-condensing and condensing engine; 
 
 Explanation of absolute or total pressure 55 
 
 Latent heat and the heat of chemical combination ; Explanation of latent 
 
 heat of water and of steam ; Units ; Difficulty of the exact determination 
 
 of the equivalent values of units 5^ 
 
 Unit of work or power ; Unit of elasticity ; Unit of temperature ; Unit of 
 
 heat 57 
 
 Specific heat of a body ; Unit of specific gravity ; Expansion ; Rate of 
 
 expansion 5^ 
 
 CHAPTER IV. 
 
 EXPANSION. 
 
 Increase in efficacy by cutting off the steam ; Expansion of steam ; Law 
 of expansion 59 
 
 "Full stroke;" Gain and losses from expansion ; The action of expanding 
 steam exemplified ; Pushing or lifting power of one cubic inch of water 
 wholly evaporated to steam 60 
 
 Utmost power to be got out of a steam engine without a cut-off; The law 
 of expansion, discovered by James Watt, exemplified 6l 
 
 The most economical point of cut-off; Considerations which modify the 
 result of expansion ; Determination of the lowest final pressure in non- 
 condensing engines; Lowest advantageous final pressure; Highest ad- 
 vantageous rates of expansion 62 
 
 Percentage of the heat used which is converted into work by steam en- 
 gines ; Cause of loss of heat ; Action and work of expanding steam ; 
 Exemplification of no cut-off, cut-off at half stroke, and cut-off one- 
 fourth of the stroke, with theoretical indicator diagrams 63 
 
 Mean pressure, how calculated ; Ratio, or grade of expansion, how calcu- 
 lated 67 
 
 Hyperbolic logarithms ; Table for hyperbolic logarithms for numbers up 
 to 39 68 
 
 Table of hyperbolic logarithms running from i.n up to y^; Expansion of 
 steam and its effects with equal volumes of steam 69 
 
 Mode of calculating the expansion ; Most convenient way of calculating 
 the horse power of an engine . 70 
 
 Gain by using steam expanding three-fourths of the stroke 71 
 
 "Indicator coefficient" of the engine ; Other valuable effects of expansion; 
 Action of steam when expanded ; Action of saturated steam in the cyl- 
 inder ; Nature of the curve described by the pencil of an indicator ... 72 
 
 Table of initial and mean effective pressure in the cylinder ; Expansion 
 diagram of steam in a cylinder, illustrated 73 
 
 Manner of finding the mean pressure for any intermediate point of the 
 stroke 74 
 
 The theoretical gain by the expansion of steam ; Rule for finding the in- 
 crease of efficiency from using steam expansively 75 
 
 Rule for finding the terminal pressure ; Saving in fuel by expansion ... 76 
 
 Rule for computing the gain in fuel 77
 
 CONTENTS. IX 
 
 PAGB 
 
 Terminal pressure ; Rule for finding the pressure at the end of the stroke ; 
 Losses of steam by "wire-drawing," condensation, friction, etc.; Increase 
 in knowledge by the improvement in the power of measurament ; The in 
 dicator, and reading of an indicator diagram 78 
 
 Expansion curves of indicator diagrams ; What the actual card from an en- 
 gine indicates ; Variations in the form of diagrams ; Indication of leakage 
 by the expansion curve ; Precautions necessary in indicating an engine . 79 
 
 CHAPTER V. 
 
 THE INDICATOR. 
 
 Use and value of the indicator ; Ignorance of many manufacturers of what 
 power is yielded by their engine; Consumption of coal per hour per 
 horse power by a good engine 80 
 
 Large engines more economical than small engines ; Evaporative efficiency 
 of the boiler; Defects in the machinery which can be discovered by 
 means of the indicator ; Comparison of the indicator with the stethoscope. 8l 
 
 Principle of, and construction of the indicator 82 
 
 The best forms of indicator ; The use which can be made of a card or dia- 
 gram taken from a steam engine ; The simplest example of an expendi- 
 ture of power 83 
 
 Attraction of gravity as a general standard of resistance 84 
 
 CHAPTER VI. 
 
 THE ACTION OF STEAM IN THE CYLINDER OF AN ENGINE. 
 
 Operation of the steam in the cylinder ; Nature of the process 85 
 
 Falling pressure the result of "wire-drawing" of the steam ; Discharge of 
 the steam from the cylinder; Interpretation of the term "vacuum"; 
 Pressures to be considered in regard to the quantity of work of steam and 
 
 its efficiency in the steam engine 86 
 
 Events which take place in supplying an engine with steam 87 
 
 "Distribution" and "periods of distribution"; The action of steam in the 
 cylinder as shown by the indicator diagrams ; Function and utility of the 
 
 indicator, with diagram illustrating the same 88 
 
 Engine power; Manner of ascertaining what power an engine is exerting, 
 
 exemplified and illustrated by indicator diagram 90 
 
 Rule for finding the foot pounds raised per minute 92 
 
 CHAPTER VII. 
 
 HORSE-POWER. 
 
 Definition of the real horse-power ; Means of raising ore in use by the early 
 English miners; Use of horses for pumping by London brewers; Horse- 
 power of a steam engine; Origin of the term "horse-power;" The real 
 horse-power according to the experiments of Smeaton 94 
 
 Watt's experiments to determine a horse-power ; The unit of power express- 
 ing a horse-power 95
 
 x CONTENTS. 
 
 PAGB 
 
 Watt's method of calculating the power of his engine ; What the term 
 "horse-power" meant when first used, and what it now means 96 
 
 "Nominal horse-power;" Distinction between nominal and actual horse- 
 power ; Confusion between the terms nominal and commercial as applied 
 to the horse-power of engines 97 
 
 Definition of work ; Definition of power ; Measurement of the work done 
 by a force ; Man-power ; Equivalence of man-power as established by 
 Morin 98 
 
 Foreign terms and units for horse-power ; Rule for finding the absolute 
 horse-power of a steam engine 99 
 
 Definition of "duty"; Common practice of estimating the performance of 
 an engine ; Duty of an engine in foot pounds which produces a horse- 
 power by the consumption of one pound of coal per hour per horse-power. 100 
 
 Successive improvements in the steam-engine traced by the progress made 
 in the economy of fuel ; Units of heat developed in the combustion of one 
 ,x>und of ordinary coal IO1 
 
 Horse-power by the indicator ; Manner of obtaining the indicated horse- 
 power of an engine ; Definition of horse-power constant, and how found ; 
 Example of computing the horse-power exerted in a diagram from the 
 cylinder of a Corliss engine, with illustration 102 
 
 Manner of calculating the indicated horse-power ; " Piston displacement," 
 what it is 103 
 
 Measurement of the power required by a single machine among many run- 
 ning in a factory 104 
 
 Manner of ascertaining the mean pressure of the indicator card ; How to 
 divide a line into a number of equal spaces, with illustrations 105 
 
 The planimeter, with illustration 107 
 
 Directions for using the planimeter, with illustration 108 
 
 Economical and wasteful engine diagrams (See Figs. 14 and 15) no 
 
 How to calculate the diagram of a condensing engine 113 
 
 Indicated horse-power ; Effective horse-power ; Engine friction ; Percent- 
 age of friction 114 
 
 Reduction of gross power to effective motive power ; Variations in the 
 effective motive power ; Back-pressure in engines, with illustration ... 115 
 
 Diagram showing excessive back-pressure 116 
 
 Impossibility of obtaining a perfect vacuum in practice ; Ways in which an 
 approximation to a vacuum is effected ; Power expended in removing air 
 from the water used for steam engine purposes . . . 117 
 
 Pressure of the atmosphere ; Table of mercury in pounds and vacuum in 
 inches ; Object of knowing the exact pressure of the atmosphere ; Differ- 
 ence in the vacuum shown by the indicator and the vacuum gage . . . . 118 
 
 Vacuum gage ; Construction of vacuum gages ; Manner of drawing the line 
 of perfect vacuum and that of the boiler pressure on diagrams represent- 
 ing condensing engines ; Variation of the line of perfect vacuum in its 
 distance from the atmospheric line 119 
 
 How to find the mean pressure above the atmosphere during the stroke, 
 the mean average pressure per square inch, and the gross indicated horse- 
 power exerted ; The strictly accurate mode of measurement 120
 
 CONTENTS. XI 
 
 PAGB 
 
 Manner of drawing the line of boiler pressure on diagrams for non-condens- 
 ing engines ; Manner of ascertaining the mean pressure in non-condens- 
 ing engines ; Mode of calculating, on stationary engines, the power 
 shown by the frictional diagrams 121 
 
 Manner of ascertaining the power required in non-condensing engines to 
 overcome the resistance of the atmosphere 122 
 
 Necessity of obtaining the average diagram , 123 
 
 CHAPTER VIII. 
 
 DIAGRAMS SHOWING THE ACTION OF STEAM IN A STEAM- 
 ENGINE CYLINDER. 
 
 The best test of the efficiency of the engine ; The action of steam in the 
 cylinder ; An ideal diagram and manner of obtaining it, with illustration. 124 
 
 The atmospheric line ; The line of perfect vacuum, illustrated by a diagram. 125 
 
 The line of boiler pressure ; The clearance line 126 
 
 The best method of calculating the clearance ; Division of the outline 
 drawn by the instrument during a revolution of the engine ...... 127 
 
 Admission line ; The steam line ; On what the maintenance of a propel 
 steam pressure in the cylinder depends 128 
 
 Importance of the steam line traced by the indicator running in a hori- 
 zontal direction ; Good results obtained with the Corliss and Buckeye 
 valves; The point of cut-off; The expansion curve; Definition of an 
 equilateral hyperbola ; Difference between the true ratio of expansion 
 and the corresponding pressures 129 
 
 The effect of leakage in altering the actual expansion curve ; Influences 
 affecting the mean temperature of the cylinder 130 
 
 Relative effect of the various degrees of expansion and of speed ; The 
 point of release or opening of the exhaust-port ; A loss of work in- 
 volved in the non-release of the steam before the end of the stroke . . . 131 
 
 The exhaust line ; Means of getting rid of the pressure of steam before 
 the piston commences its return stroke ; Insurance of the greatest 
 amount of work 132 
 
 Back-pressure, or line of counter-pressure ; Pressure of condensation ; 
 Cause of the pressure in the condenser j^ 
 
 The principal cause of increased back pressure ; Variation in the excess of 
 the back pressure over the atmospheric pressure in non-condensing 
 engines 134 
 
 The back-pressure line ; Back pressure in diagrams from non-condensing 
 and from condensing engines ; Size of the passages and pipes communi- 
 cating with the atmosphere 135 
 
 The point of exhaust closure ; The line of compression or cushioning ; The 
 most advantageous adjustment of compression ; Indication of an excess 
 of compression 136 
 
 Beneficial effects of the proper regulation of compression 137 
 
 No loss of efficiency by compression 138 
 
 Lead, what it means; Definition of the lead of a valve ; Outside and inside 
 lead 139
 
 Xli CONTENTS. 
 
 PAGE 
 
 Lead allowed by the Baldwin Locomotive Works ; Regulation of the steam 
 
 admission by lead and compression 140 
 
 The mean effective pressure ; The terminal pressure ; The initial pressure . 141 
 
 Initial expansion ; Wire-drawing and throttling 142 
 
 Loss due to wire-drawing ; Cause of wire-drawing or lamination of steam ; 
 The ordinary throttling governor not economical in fuel ; Wire-draw- 
 ing less in locomotive engines than in throttling engines 143 
 
 Improvement in the economy in performance of the locomotive ; Avoid- 
 ance of wire-drawing by modern automatic cut-off valve arrangements ; 
 
 Wire-drawing and throttling accompanied by direct loss 144 
 
 Undulations, or waviness of the expansion line, with illustrations .... 145 
 Great value of the wavy lines ; Means of diminishing the extent of the 
 undulations; Manner of determining the area; Effect of friction in 
 
 indicators 146 
 
 The expansion curve of indicator diagrams; Causes of variations in 
 diagrams ; Precautions required in indicating an engine 147 
 
 CHAPTER IX. 
 
 CORRECT INDICATOR DIAGRAMS. 
 
 Essentials for the correctness of indicator diagrams ; Method to obtain the 
 reducing motion of the piston 148 
 
 The proper place to attach the indicator ; Advantage of employing two in- 
 dicators 149 
 
 Precautions in applying the cylinder ; Advisability of the repeated retracing 
 of diagrams ; Difficulty in taking indicator diagrams from engines run- 
 ning at over 300 revolutions perminute 150 
 
 Facts in regard to which the diagrams will testify ; Length of indicator 
 diagrams 151 
 
 The correctness affected by long cards ; The record obtained by the indi- 
 cator ; Indicator diagrams and manner of taking them from one end of 
 the cylinder, with illustrations 152 
 
 Gross indicated horse power, how obtained 154 
 
 Diagram from a Corliss engine, 8 inches diameter, 24 inches stroke, and 90 
 revolutions 155 
 
 Manner of taking a diagram from the other or both ends of the cylinder ; Use 
 of the indicator for showing the condition of the engine, with illustration. 156 
 
 Determination between nominal, indicated and effective horse power, by 
 the use of the indicator 158 
 
 Data for ascertaining the power exerted by the steam engine furnished by 
 the indicator ; The geometry of the indicator diagram 159 
 
 Back-pressure ; Cause of the mean back-pressure exceeding the pressure 
 of condensation 160 
 
 Gain of mean effective pressure with a condensing engine over that of a 
 non-condensing engine 161
 
 CONTENTS. xiii 
 
 CHAPTER X. 
 
 STEAM EXPANSION CURVES OR PRESSURE OF STEAM IN 
 CYLINDER. 
 
 Discrepancy between the theoretical curves of expansion and the actual 
 expansion line drawn by the indicator explained 162 
 
 Difference between gases and vapors ; Relationship between the pressure 
 and the volume of a gas as established by Boyle and Mariotte, explained 
 and illustrated 163 
 
 Conditions under which Boyle's and Mariotte's law holds good with all 
 gases 164 
 
 Causes of the fall and rise of the expansion curve drawn by the indicator, 
 below and above the theoretical expansion curve, with illustration . . 165 
 
 The true cause of a higher terminal pressure in cylinders using steam more 
 expansively than the law of the expansion of gases can account for . . 166 
 
 Effect due to a leaky piston and exhaust valve, with illustration ; Isother- 
 mic or hyperbolic and adiabatic curves 167 
 
 The greatest quantity of work obtained in practice from a given quantity 
 of heat ; The theoretical diagram with expansion curves produced under 
 the different conditions 169 
 
 The theoretical diagram representing the theoretical curve of expansion ; 
 How the total amount of work done during one stroke is represented in 
 every diagram 170 
 
 Representation of the value of the work wasted, with illustrations .... 171 
 
 Confused notions resulting from the inexact use of language as regards the 
 upper and lower lines of the diagram ; What the real lower line of the 
 diagram is ; How a correct and complete diagram of the pressure on that 
 side of the piston upon which the steam is admitted is obtained, with 
 illustrations 172 
 
 Diagram representing the pressure exerted by the exhaust steam and at- 
 mosphere to oppose the return of the piston 173 
 
 Diagram showing the total opposing forces 174 
 
 Method of drawing the diagram showing the total opposing forces ; The re- 
 lation between the pressure and volume of saturated steam, as shown by 
 the indicator diagram 175 
 
 Nature of saturated steam ; Great value of a curve expressing the relation 
 between the pressure and volume in interpreting the diagrams given by 
 an indicator ; Definition of "specific volume" or "relative volume" . . 176 
 
 Table of temperature and corresponding pressure of saturated steam ; Devi- 
 ation in the form of the curve expressing the relation between the pressure 
 and the volume from Boyle's and Mariotte's law 177 
 
 C. Cowper's diagram of the expansion of saturated steam, with illustration. 178 
 
 Diagrams presenting a summary of successive improvements in the steam 
 engine 179 
 
 Clearance ; What is meant by clearance ; The effect of clearance ... .181 
 
 Reason why the terminal pressure as shown by an indicator diagram is us- 
 ually very much higher than it would be found according to rule .... 182
 
 xiv CONTENTS. 
 
 PAGE 
 
 Modification of the diagram required for its completion, with illustration . 183 
 
 Reduction of loss from clearance 184 
 
 Principles which always hold good ; Effect of too much clearance on the 
 
 diagram, with illustration 185 
 
 The expansion curve ; Application of the Mariotte, or Boyle, curve to the 
 
 expansion of steam, with illustration 187 
 
 Application of a hyperbola to a diagram 188 
 
 CHAPTER XL 
 
 COMPARATIVE INDICATOR DIAGRAMS. 
 
 Standard for comparing engines ; Total clearance in the ordinary commer- 
 cial steam-engine ; Manner of calculating the clearance 189 
 
 Mode of constructing a theoretical diagram, with illustration 191 
 
 The advantage of variable automatic expansion ; Means of ascertaining the 
 
 increase of economy which can be gained in an automatic cut-off engine. 194 
 Ideal expansion diagram ; The further advantage of variable expansion and 
 
 condensing ; Secret of economy in using steam expansively 195 
 
 Minimum saving by automatic cut-off condensing engines 196 
 
 Explanation of the diminished efficiency of the throttling-engine ; The the- 
 oretical diagram : how to construct it geometrically, with illustration . . 197 
 How to lay out the hyperbolic curve from the point of cut-off, with illustra- 
 tion 199 
 
 How to fix the clearance line when not known ; The disadvantage of too 
 
 large an engine 200 
 
 How a direct loss occurs in the non-condensing engine, with illustration . 201 
 What the work of an engine for its economical use should be ; Diagram 
 
 from an automatic cut-off engine 203 
 
 Condensation in steam-engine cylinders ; Heating power of one pound of 
 carbon, and units of heat it is capable of imparting ; Difference in the 
 amount of heat taken up by different substances ; Definition of " specific 
 
 heat" 204 
 
 Explanation of the unsatisfactory results of high expansive working . . . 205 
 
 Varying temperature of the cylinder 206 
 
 The value of short strokes and high rotative speeds 207 
 
 CHAPTER XII. 
 
 STEAM-JACKETS. 
 
 The steam-jacket first used by Watt ; Principle of the steam-jacket ; Con- 
 ditions of the steam-cylinder in practice 208 
 
 The use of an entirely unprotected cylinder wrong and wasteful, with illus- 
 tration 209 
 
 Causes of loss in a steam-engine unprotected by a steam-jacket, with illus- 
 trations 210 
 
 The expansion curve of steam in an imperfectly protected cylinder, with 
 illustration 212 
 
 Condition of the steam in cylinders covered with non-conducting material. 213
 
 CONTENTS. XV 
 
 PAGE 
 
 Alternate heating and cooling of a cylinder covered with non-conducting 
 material, and Watt's endeavor to eliminate it ; The action of the cylinder 
 
 on the steam 214 
 
 Erroneous opinion of many engineers regarding the steam-jacket ; Especial 
 
 use of the steam-jacket in the expansive engine 215 
 
 Indicator diagram from an expansive engine with a non-jacketed cylinder. 216 
 Indicator diagram from an expansive engine with a jacketed cylinder . . . 217 
 
 Facts upon which the utility of steam-jacketed cylinders is based 218 
 
 Extension of the use of the steam-jacket ; Disadvantages of jacketing with 
 exhaust steam ; Supply of steam to the jacket ; How the walls of the 
 
 cylinder may be kept nearly as hot as the entering steam 220 
 
 Diagram from an engine with a steam-jacket over the ends and sides; Loss 
 
 from condensation prevented by the use of a steam-jacket 221 
 
 Work performed by the steam in the jacket ; Saving in the efficiency of 
 steam with jacketed cylinders ; Actual loss from expanding steam in an 
 unjacketed cylinder ; Advisability of the use of a jacket in the absence 
 
 of super-heating 222 
 
 Necessity of the jacket being distinct from the cylinder ; Reason why the 
 utility of the steam-jacket is often called in question 223 
 
 CHAPTER XIII. 
 
 VARIETIES OF STEAM-ENGINES. 
 
 Various modes of classing engines 224 
 
 Condensing engines ; Condenser ; Function of the condenser ; Necessity of 
 condensation for very early engines 225 
 
 The exact relation of the condenser ; Jet condenser ; Extent of the vacuum 
 created in the condenser ; Capacity and temperature of the condenser . 226 
 
 Surface condensation ; Results of experiments on marine engines using 
 surface condensation ; Removal of water from the condensers 227 
 
 Increase in the economical power of an engine by a good condenser; Cause 
 of the efficiency of condensers 228 
 
 Advantages of employing an independent condensing apparatus ; Amount 
 of injection water required and loss resulting therefrom ; The reason why 
 only a small percentage of the power contained in each pound of coal is 
 realized ' 229 
 
 Importance of utilizing standing water in ponds or wells ; Lifting condens- 
 ing water ; No loss of power involved in the lifting of injection water to 
 a condenser by the action of the vacuum in the latter 230 
 
 Air-pump ; Capacity of the air-pump 231 
 
 Work of the air-pump ; High pressure steam ; Hornblower the inventor of 
 the double or compound cylinder engine ; The first practically useful 
 high-pressure engine built and put in operation by Oliver Evans . . . 232 
 
 Specification of Arthur Woolf's patent for certain improvements in the 
 construction of steam engines ; Peculiar theories held by Woolf ; Advo- 
 cacy of the economy of high pressure steam with expansion by Treve- 
 thick and Woolf 233
 
 XVI CONTENTS. 
 
 Increase in the duty of an engine by high pressure of steam and expand- 
 ing; Comparative efficiency of different engines; The "atmospheric 
 engine" .............................. 2 34 
 
 Function of the steam in the atmospheric engine ; Indicator diagram from 
 an atmospheric engine ....................... 235 
 
 Single acting engines ; Best type of a single acting engine ........ 236 
 
 The principle of single acting engines ; Remarkable examples of the ap- 
 plication of single acting steam engines to pumping ......... 237 
 
 Indicator diagrams from a single acting engine and their interpretation . 238 
 
 Calculation of the horse power of a single acting pumping engine; Double 
 acting engines ; Diagram from a double acting engine ......... 240 
 
 Diagram from a condensing engine .................. 241 
 
 Automatic steam engines; The most prominent in general use in the 
 United States; The object of using steam expansively; How the greatest 
 difference between the mean pressure in the cylinder through the stroke 
 and that at the end of the stroke is obtained ............. 242 
 
 Superiority of steam engines with a variable cut-off as compared with the 
 throttling engines .......................... 243 
 
 Economy in using steam expansively; Requirements for economically run- 
 ning a steam engine at a high grade of expansion ; Present imperfect 
 condition of the steam engine ; Class of non -condensing engine most in 
 use ................................. 244 
 
 Diagram from a non-condensing throttling engine showing excessive back 
 pressure .............................. 245 
 
 Diagram exhibiting the improvement in modern throttling engines in the 
 valve motion ............................ 246 
 
 Non-condensing automatic cut-off engines ; Automatic expansion engines; 
 The fundamental idea of automatic expansion engines ........ 247 
 
 The liberating valve-gear devised by Frederick E. Sickles ; Reasonings of 
 the advocates of this system ; The distribution of steam required by the 
 theory of working by variable expansion ............... 248 
 
 Automatic cut-off engines; The modern cut-off engine brought out, in 
 1849, by George H. Corliss ...................... 249 
 
 Difficulties of Mr. Corliss in introducing his engine ; Indicator diagram 
 from a non-condensing Corliss egine, showing the distribution of steam 
 in the cylinder ........................... 250 
 
 Recognition of the value of high pressure, and considerable expansion, in 
 the early part of the present century ; The Greene and other automatic 
 engines; Probable substitution of the "positive motion cut-off" for the 
 "drop cut-off" liberating valve gear ................. 251 
 
 The fundamental principle of high rotative speeds ........ ... 252 
 
 Positive motion cut-off engines ; Perfection of the Porter Allen engine, by 
 Mr. Charles T. Porter ; Diagram from a Porter Allen engine ; The Buck- 
 eye engine ............................. 253 
 
 Indicator diagrams from a Buckeye automatic engine .......... 254 
 
 The "straight line engine" invented by John E. Sweet; Objection to a 
 single-valve cut-off engine; Diagram from a single-valve straight line 
 engine ............................... 255
 
 CONTENTS. xvii 
 
 ,PAGE 
 
 New engine designed by Mr. Sweet 256 
 
 Wherein Mr. Sweet's new engine differs from all others , . . . 257 
 
 The Westinghouse single-valve engine ; The most serious results from high 
 speed in the horizontal engine eliminated by it ; The merit of the single 
 acting and self-lubricating principles established by the Westinghouse 
 
 engine ; Improvement in the Westinghouse engine 258 
 
 Locomotive engines; Diagram from a Baldwin four-driver locomotive; 
 
 Diagrams from Baldwin locomotive engine No. 81 259 
 
 Indicator diagrams showing the tractive power exerted nnder different rates 
 
 of speed ; Load ; Composition of the train 260 
 
 Diagrams from an English locomotive ; Engines of the London and North 
 Western Railway ; Diagrams showing the tractive power of the "Pre- 
 cursor" 262 
 
 Average weight of trains hauled by the " Precursor " 266 
 
 Compound steam engines ; What compounding is 267 
 
 Jonathan Hornblower's patent for using two cylinders 268 
 
 First public announcement of the benefit to be derived from the expansion 
 of the steam ; Application of the principle of the double cylinder by 
 
 Arthur Woolf 269 
 
 Preference of the compound engine for marine purposes ; Difference be- 
 tween the simple and compound systems 270 
 
 Loss of pressure with a compound engine 271 
 
 The action and arrangement of the principal varieties of compound 
 
 engines, with illustrations 272 
 
 Curious form of continuous expansion compound engine 274 
 
 Compound engines with intermediate reservoir, or receiver ; Diagram from 
 
 a compound vertical engine with intermediate receiver 277 
 
 " Continuous expansion engine, " with illustration 278 
 
 Advantages claimed for engines built upon the continuous expansion 
 
 system . 279 
 
 Disadvantage of the system 280 
 
 Diagrams from continuous expansion engines ; Compound versus simple 
 
 engines ; Points of superiority in the compound engine 281 
 
 Liquefaction more injurious in simple than in compound engines; Diagram 
 
 from a compound engine 282 
 
 Theoretical diagram ; Values of the low pressure diagram 283 
 
 Amount of loss due to back pressure, illustrated 284 
 
 To avoid intermediate expansion ; Arrangements for the avoidance or re- 
 duction of intermediate drop, with illustration 285 
 
 The theoretical diagram expanding twelve times in a simple engine ... 286 
 
 Theoretical diagram of a compound condensing engine 287 
 
 Diagram from a simple compound Westinghouse engine ; Compound con- 
 densing engines ; Diagrams from a Westinghouse compound condensing 
 engine ; Table of actual steam consumed per indicated horse-power 
 
 Westinghouse compound engine 288 
 
 Diagrams from a compound condensing engine 289 
 
 Early compound engines ; An old French work giving particulars of the 
 steamers plying, in 1842, upon the Gironde and the Garonne 290
 
 xviii CONTENTS. 
 
 PAGE 
 
 Advantages of the compound steam engine 291 
 
 Impossibility of explaining by any of the laws heretofore laid down that it 
 is more economical to use steam expansively in the compound engine 
 than in any form of the ordinary engine ; Erroneous reasons of many 
 engineers for condemning the compound engine ; The offices the steam 
 
 has to perform upon entering the cylinder 292 
 
 Tyndall's researches on aqueous vapors ; Experiments made by Mr. C. E. 
 Emery ; The transfer of heat from the metal walls of the cylinder to the 
 exhausting steam ; Variation in the quantity of heat transferred from a 
 
 radiating to an absorbing body 293 
 
 Triple expansion engines ; The arguments for and against this new class of 
 
 engine 294 
 
 Advantages of the triple expansion engine ; Causes of its superior economy. 295 
 
 Diagrams from a compound condensing triple expansion engine 297 
 
 Diagrams from a horizontal compound condensing triple expansion engine. 298 
 Chart of relative economy, under varying loads ; Diagram of the perform- 
 ance of a single cylinder non-condensing engine, as contrasted with the 
 
 compound engine, non-condensing and condensing 299 
 
 Compound locomotives ; Their introduction, in 1850, by John Nicholson . 300 
 
 M. Jules Morandiere's attempt at compounding locomotives 301 
 
 M. Anatole Mallet's system of compound locomotives ; Chief features of 
 
 this system 302 
 
 Diagrams from M. Mallet's locomotive ; Economy of fuel with compound 
 locomotives ; Improved compound locomotive designed and patented by 
 
 Mr. Francis W, Webb 303 
 
 Success of the Webb compound locomotives ; Importation of one of these 
 locomotives by the Pennsylvania Railroad, for trial ; Indicator diagrams 
 
 from a compound locomotive 304 
 
 The assertions of economy made for the Webb locomotives not borne out 
 by the diagrams ; Objection to and drawbacks of the Webb locomotive ; 
 
 Compound locomotive patented by T. W. Worsdell 305 
 
 The " intercepting valve" and the starting valve one of the chief features 
 
 of Mr. Worsdell's locomotive ; The action of this arrangement 306 
 
 Indicator diagrams from the Worsdell locomotive 308 
 
 Failure in this country of the compound locomotives as economizers of fuel ; 
 Opinion of Mr. A. B. Underbill 309 
 
 CHAPTER XIV. 
 
 GAS-ENGINES. 
 
 History of gas-engines ; Principal features of Dr. Alfred Drake's engine ex- 
 hibited at the New York Crystal Palace, in 1855 310 
 
 Lenoir and Hugon gas-engines ; Otto and Langen's gas-engine ; Otto's im- 
 provements in gas-engines ; Otto's " silent " gas-engine 311 
 
 Advantages of gas-engines ; Their extensive use a benefit to gas manufac- 
 turers and gas consumers ; Probability of air being the chief motive 
 power of the future ; Gas-engines ; M. Dugald Clerk's theory of the gas- 
 engine 312
 
 CONTEXTS. XIX 
 
 PAGE 
 
 The distinct types of gas-engines at the present time 31* 
 
 Calculation of the amounts of gas required by the various types 314 
 
 Error of previous observers in calculating the efficiency of the gas-engine 
 
 from its diagram 315 
 
 Early gas-engines ; Classification of this kind of early motors 316 
 
 Johnson's patent for a gas-engine ; Early recognition of the value of gas- 
 engines ; Unscrupulous claims made for the Lenoir gas motor .... 317 
 Lenoir's priority of invention contested by Hugon and Keithmann ; Diffi- 
 culty in constructing a satisfactory gas-engine ; Diagrams from a Lenoir 
 
 gas-engine 318 
 
 The Otto and Langen atmospheric gas-engine ; Its drawbacks and advan- 
 tages 319 
 
 Otto's silent gas-engine ; External appearance of these gas-engines and 
 
 their method of working 320 
 
 Diagrams from the Otto and Langen and Otto's gas-engines 321 
 
 Points in which the new Otto motor differs from its predecessors ; The cost 
 
 of working the Otto engine 323 
 
 The Clerk gas-engine ; Its distinctive features 324 
 
 Diagrams from the Clerk gas-engine 326 
 
 The " Stockport " gas-engine 327 
 
 Difference between the Stockport and Otto engines 328 
 
 Gas consumption of the Stockport engine ; The Atkinson gas-engine ; Dia- 
 gram from an Atkinson "cycle" gas-engine 331 
 
 Arrangement of the Atkinson gas-engine 332 
 
 Causes of the great economy of the Atkinson gas-engine 333 
 
 Trial of an Atkinson patent "cycle" gas-engine, with diagrams of engine 
 
 and pump 334 
 
 Result of the trial 336 
 
 Brake trial of the Atkinson gas-engine 337 
 
 Table of real percentages of heat actually turned into work, etc 338 
 
 The " Forward " gas-engine ; Distinguishing feature of the Forward . . . 339 
 Trial of the Forward; Self-acting gas-engine; Clerk's arrangement for 
 
 starting the engine 340 
 
 Otto's twin-cylinder gas-engine ; The self-starting arrangement of this en- 
 gine 341 
 
 Spiel's petroleum engine 342 
 
 Dowson's water-gas ; Apparatus for manufacturing the gas 344 
 
 Manner of using the gas 345 
 
 Trials of the Dowson gas by Messrs. Crossly of Manchester ; Cost of the 
 
 Dowson gas 346 
 
 The future of the gas-engine 347 
 
 Gas and steam-engine heat efficiency 348 
 
 CHAPTER XV. 
 
 AUTOMATIC CUT-OFF VS. POSITIVE CUT-OFF. 
 Importance of the question, What will be the cost of fuel to do a given 
 amount of work with either type of engine? Utility of the indicator in 
 solving the question illustrated by a case from practice 349
 
 XX CONTENTS. 
 
 PAGE 
 
 Indicator diagrams from a condensing engine 353 
 
 Relative economy of different engines ; Diagrams illustrating the relative 
 
 engine economy 354 
 
 How the relative economy of different engines may be illustrated 355 
 
 Comparison of cost per horse power with a throttling engine and automatic 
 
 non-condensing engine 356 
 
 Diagrams from an automatic non-condensing and an automatic condensing 
 
 engine 357 
 
 Diagrams from a pair of automatic condensing engines, from a condensing 
 
 automatic cut-off engine, and from a non-condensing engine 359 
 
 Diagram from a pumping engine 360 
 
 Diagrams from a passenger locomotive 361 
 
 Diagrams from a freight locomotive 362 
 
 Light on some questions about which engineers now differ in opinion to be 
 
 expected from a careful study of diagrams from locomotives 363 
 
 Diagrams from a locomotive of the Southern Pacific Railroad 365 
 
 Diagrams taken in testing the Worthington pumping engine at Belmont, 
 
 Philadelphia, May, 1872 367 
 
 CHAPTER XVI. 
 
 MISCELLANEOUS. 
 
 Leakage of steam-engines as shown by the diagram ; Diagram from an au- 
 tomatic cut-off engine 372 
 
 Mode of finding the percentage of leakage 373 
 
 Distorted indicator diagrams ; Diagram from a modern built automatic cut- 
 off engine 374 
 
 Diagrams from an upright automatic cut-off engine, see Figs. 178, 179, 180 
 
 and 181 375 
 
 The economy of a steam-engine ; How to calculate the amount of steam 
 
 (water) consumed from an indicator diagram 376 
 
 Reasons why the total amount of water cannot be estimated, except by 
 
 measuring the feed water 377 
 
 Manner of ascertaining the weight of the steam, of which the indicator 
 
 shows the pressure , 378 
 
 To compute the economy of water consumption ; Method for finding the 
 
 rate of water consumption for the engine alone 379 
 
 To make allowance for compression and clearance, with illustrations . . . 380 
 
 Computation Table No. 8 383 
 
 Explanation of Table No. 8; Example for use of Table No. 8 384 
 
 Illustration of Table No. 8 by comparison of diffent types of engines ; Ex- 
 planation of the comparative steam economy between "throttling" and 
 
 automatic cut-off regulation, with illustration 385 
 
 Evil of light loads ; An over-large engine destructive to good economy . . 386 
 Efficiency or duty of pumping engines ; Definition and expression of duty ; 
 
 Methods generally employed in estimating the duty 387 
 
 Simple way of measuring the water delivered into a reservoir, suggested by 
 Mr. Nystrom 3 S8
 
 CONTENTS. XXI 
 
 PAGE 
 
 Trial of Mr. Nystrom's instrument at Fairmount and other steam pumping 
 
 works of Philadelphia 389 
 
 Reducing motion ; Essentials for the correctness of the diagram 390 
 
 Simple plans for reducing the motion, with illustrations 391 
 
 Methods of attaching the various devices to the crosshead ; Precautions in 
 
 the use of these devices - 393 
 
 Engine tests at electrical exhibition, Philadelphia, 1884; Test of Porter- 
 Allen engine 394 
 
 Diagram showing the mean of all the indicator cards during the test ; Dia- 
 gram of the card representing most nearly the mean horse power devel- 
 oped ' ' ' 395 
 
 Table giving the pressures corresponding to the different parts of the stroke 
 
 on the mean indicator card ; Test of the Buckeye engine 397 
 
 Mean card (Buckeye engine) 399 
 
 Trial of the Southwark engine 401 
 
 Diagrams showing the mean of all the indicator cards taken during the 
 
 test, and of the card coming most nearly to the mean horse power . . . 403 
 Table giving the pressures corresponding to the different parts of the stroke, 
 
 which would give the mean indicator card 404 
 
 Horse power ; Manner of obtaining the total indicated horse power of the 
 
 engine 405 
 
 Mean indicator card ; Water accounted for by the indicator cards .... 406 
 An approximation to the effective mean pressure; Process of making a 
 close approximation of the mean pressure of a diagram, with illustration; 
 
 Frequent mistake in measuring on the ordinate lines 407 
 
 Conclusion ; Causes which influence the form of the indicator diagram . . 408 
 
 APPENDIX. 
 
 The indicator ; Service of the indicator in developing the steam-engine ; 
 
 Office of the indicator ; Conclusions from the indicator are the results of 
 
 a process of reasoning 411 
 
 Instruction to be derived from a careful and comprehensive study of the 
 
 diagrams from different engines 412 
 
 Indicators in general use ; The Thompson indicator, with illustrations . . 413 
 
 Tabor indicator, with illustrations 414 
 
 The Crosby steam-engine indicator, with illustration 415 
 
 Boilers ; The best results obtained with the " flue " boiler 416 
 
 High pressure steam ; Steel vs. iron 417 
 
 The reason why mild steel plates are preferred to the best iron plates ; 
 
 Super-heated steam 418 
 
 Priming or boiler disturbance ; Horizontal flue boiler ; Incrustation of 
 
 boilers 419 
 
 Drawbacks arising from the incrustation of boilers 420 
 
 George W. Lord's boiler compound 421 
 
 Power of a boiler ; Fahrenheit and Centigrade thermometers ; Falling 
 
 bodies . . 422
 
 xxii CONTENTS. 
 
 PAGE 
 
 Bodies falling in a vacuum ; Reason why heavy bodies fall faster than light 
 
 bodies in air 423 
 
 Table of horse-power constants for single cylinder engines .... . . . 425 
 
 Horse power constants 426 
 
 Method of computing power 427 
 
 Table of areas and circumferences of circles from ^ to 4 inches in diame- 
 ter, varying by sixteenths ; and from 4 inches to 100 inches in diameter, 
 
 varying by one-eighth inch 428 
 
 Rule for finding the areas of larger circles ; Properties of water and steam ; 
 
 In relation to heat ; Volume of water 433 
 
 Properties of water 434 
 
 Latent and total heat in water from 32 degrees 435 
 
 Tables of the properties of water 436 
 
 Steam or aqueous vapor ; The ideal zero of aqueous vapor 443 
 
 Properties of steam 444 
 
 Latent heat of steam 445 
 
 Tables of the properties of steam 446 
 
 Index 453
 
 STANDARD NOTATIONS OF LETTERS. 
 
 I have throughout this work attempted to adopt a standard 
 notation of letters, for which some new characters have been 
 added to distinguish different quantities which have heretofore 
 been denoted by identical letters, thereby causing confusion as 
 well as errors. 
 
 I have hoped that by so doing that a mere glance at the for- 
 mulas will denote this meaning, without special reference to the 
 characters. 
 
 INDICATOR DIAGRAMS NOTATIONS. 
 
 A D denotes atmospheric line. 
 
 V V denotes line of perfect vacuum. 
 
 B C denotes line of boiler pressure in pounds. 
 
 k denotes the initial steam pressure of diagram. 
 
 e denotes the point of cut-off. 
 
 f denotes the expansion curve. 
 
 / denotes the point of release. 
 
 g denotes the termination of the expansion line. 
 
 d denotes the termination of the fall of exhaust line. 
 
 h denotes the commencement of the compression line. 
 
 m denotes the termination of the exhaust line. 
 
 i denotes the commencement of the steam lead. 
 
 STEAM NOTATIONS. 
 
 P = absolute or total steam-pressure, in pounds per square inch. 
 p steam-pressure above that of atmosphere, as is shown on 
 
 the steam gage. 
 
 tf = steam volume compared with that of its water. 
 H units of heat per pound in steam. 
 If units of heat per cubic foot in steam. 
 L = latent heat per pound in steam. 
 L' = latent heat per cubic foot in steam. 
 ( xxiii )
 
 XXIV STANDARD NOTATIONS OF LETTERS. 
 
 f& = pounds of steam per cubic foot. 
 
 ( = pounds of steam per pound. 
 
 7 = temperature of steam Fahrenheit. 
 
 / = temperature of steam Centigrade. 
 
 J = thermodynamic equivalent. 
 
 g = grade or ratio of expansion that is, when the steam is 
 expanded to double its volume, then g = 2 ; when 
 three times the volume, g = 3 and so on. 
 
 WATER NOTATIONS. 
 
 ty = volume of water that at 39 or 40 degrees = i. 
 
 / = temperature of water Centigrade. 
 
 7 = temperature of water Fahrenheit. 
 
 / = latent heat per pound in water from 32 degrees. 
 
 V = latent heat per cubic foot in water. 
 
 *$ = weight in pounds per cubic foot of water. 
 
 ( = fraction of a cubic foot per pound of water. 
 
 W cubic feet of water. 
 
 w = cubic inches of water. 
 
 Ibs = pounds of water. 
 
 MISCELLANEOUS NOTATIONS. 
 
 The letters T and t denote time, T and t> temperature, V 
 and v denote velocity, HP denotes horse-power, and a equals 
 infinite, or denotes that one quantity varies as another; as P 
 varies as \. 
 
 = denotes equality. 
 
 4- denotes plus or addition. 
 
 denotes minus or subtraction. 
 
 X denotes multiplication. 
 
 -5- denotes division. 
 
 V denotes square root. 
 
 f denotes cube root. 
 
 3* denotes 3 is to be squared. 
 
 4 s denotes 4 is to be cubed. 
 
 d denotes diameter. 
 
 T denotes 3.1416, or periphery or a circle when d I. 
 
 f denotes fraction, or broken number.
 
 CHAPTER I. 
 
 INTRODUCTION. 
 What The Steam Engine Is. 
 
 A STEAM-ENGINE is popularly understood to be a machine by 
 which the power generated in a steam boiler is transmitted to 
 where the work is to be executed. From well-known experi- 
 mental data, the volume of steam generated by the evaporation 
 of a given volume of water being known, this steam volume 
 multiplied by the steam pressure gives the work done by the 
 steam. This work divided by the time in which it is executed, 
 gives the natural effect, or power of the evaporation, indepen- 
 dent of the power transmitted by the steam-engine; suppos- 
 ing that the steam is fully admitted throughout the stroke of the 
 piston. 
 
 When the steam is expanded in the steam-engine cylinder, 
 the above defined power multiplied by i, plus the Hyperbolic 
 logarithm for the expansion, gives the natural effect of the 
 steam, as will be shown further on. 
 
 Physically the steam-engine is an apparatus whereby the 
 work latent in the coal is caused to manifest itself as molecular 
 motion, or heat, and is eventually transformed into work and 
 motive power. 
 
 The physical constitution of heat is not yet well understood, 
 for which reason we cannot give an intelligent explanation of 
 the dynamic elements of combustion and evaporation ; but one 
 thing appears to be certain namely, that the temperature of the 
 heat represents force, which is the origin of all power and work. 
 It is also known and demonstrated that heat is convertible into 
 work; and consequently, heat must be the product of the three 
 simple physical elements force, velocity and time. 
 
 If the temperature of the heat represents force, then the space 
 occupied by the heat must evidently represent the product of 
 velocity and time.
 
 i8 
 
 THE STEAM-ENGINE AND THE INDICATOR. 
 
 Dynamics. 
 
 Dynamics is the science of forces in motion, producing power 
 and work. 
 
 The dynamical branch of mechanics consists of the following 
 simple principles: 
 
 Elements. 
 
 Functions. 
 
 Force, 
 Velocity, 
 Time. 
 
 Power, 
 Space, 
 Work. 
 
 Force is any action that can be expressed simply by weight. 
 
 Velocity is rate of motion in regard to assumed fixed objects. 
 
 Time is duration, or that measured by a clock. 
 
 Power is the product of the first and second elements, force 
 and velocity. 
 
 Space is the product of the second and third elements, velocity 
 and time. 
 
 Work is the product of the three elements, force, velocity and 
 time. 
 
 All dynamical problems, without exception, can be solved 
 with the above six principles. 
 
 The term most used in a majority of engineering works is 
 "energy" with various adjectives, as follows: 
 
 Energies. 
 
 Translation. 
 
 Plain energy, 
 Potential energy, 
 Intrinsic energy, 
 Kinetic energy, 
 Internal energy, 
 External energy, 
 Equality of energy, 
 Factor of energy, 
 Energy excited, 
 Actual energy, 
 Mechanical energy, 
 
 Power, 
 
 Powerful power, 
 Genuine or true power, 
 Motive power, 
 Inside power, 
 Outside power, 
 Alike power, 
 Terms of power, 
 Power that pushes, 
 Real power, 
 Power in mechanics.
 
 INTRODUCTION. 19 
 
 All the terms employed, as above, whereby to define energy, 
 simply mean power, but they are used loosely to denote work, 
 with but little regard, frequently, to accuracy of definition. 
 
 Within the last few years there have been published in this 
 country a number of works on mechanics, written by professors 
 of institutions of learning in which the foregoing terms are em- 
 ployed ; terms that are not understood by the majority of prac- 
 tical mechanics, and hence the value of such works is to a large 
 extent lost. 
 
 Energy may be properly defined, so as to be understood by 
 all, as being the power or capacity to do work.
 
 CHAPTER II. 
 
 WHO INVENTED THE STEAM-ENGINE? 
 
 IF, like Topsy, any invention "wasn't born," but "growed," 
 it is that of the steam engine. Go, reader, to the Franklin In- 
 stitute of Philadelphia, and ask for Mr. Bennet Woodcroft's 
 translated edition, now out of print, of Hero's book of A. M., 
 3804, or, say, the year 200 B. C. Hero was not an inventor at 
 all, so far as we know at any rate his book asserts no personal 
 claims; yet, in his time, the power of steam, and a great deal of 
 what goes to make up the steam-engine including the slide 
 valve, the spindle valve, and the metallic piston in a metallic 
 cylinder were understood. 
 
 No doubt one of the first steps in the invention was the dis- 
 covery of combustion or fire, the expansion of water into steam 
 under the influence of heat, and the availability of this expan- 
 sive force for the performance of useful work. As to who first 
 observed this cardinal fact we have no historical record, but 
 Hero of Alexandria (in Spiritalia seu Pneumatica\ describes 
 several ingenious machines, of which perhaps the best known 
 is that which still bears the name of "Hero's Fountain." 
 Among other devices, he describes a ball suspended in mid-air 
 by means of a steam-jet, an apparatus which was revived as an 
 air-jet and exhibited as something quite new (?) at the Centen- 
 nial Exhibition at Philadelphia, and which created considerable 
 interest and discussion as to the principles involved. Hero also 
 describes an apparatus which we of to-day might call a steam 
 turbine. Another apparatus of Hero represents a priest stand- 
 ing before an altar. When fire is kindled upon the altar, water 
 which it contains is heated, and the steam thus generated forces 
 out by its pressure the water remaining. This water passes 
 through a concealed tube, so that the priest appears to pour 
 water from his flask into an urn upon the altar. 
 
 All of these devices are only ingenious, and at that time were 
 merely marvelous toys. They involve, it is true, facts and 
 (20)
 
 WHO INVENTED THE STEAM-ENGINE? 21 
 
 principles which, rightly apprehended, might have led to the 
 greatest results. But it is quite clear that they were not thus 
 apprehended, and that the inventors of such toys were them- 
 selves ignorant of the principles which governed their actions. 
 A philosophy which arbitrarily assumed that all nature was 
 composed of four elements earth, air, fire and water and that 
 steam was a kind of air, generated by the two elements fire and 
 water, which accordingly strove to rise to the place of the next 
 highest element and such a philosophy prevailed blinded the 
 eyes of mankind, and prevented a proper interpretation of those 
 very facts of nature of which they even made daily use. The 
 ancients knew nothing of the true nature of steam could know 
 nothing as long as they were blinded by their arbitrary ideas of 
 what it ought to be. Nature was continually pointing them to 
 roads fruitful on every side with discoveries, but they could not 
 recognize her indications. What of knowledge and progress 
 have been lost to the world by reason of the false methods and 
 philosophy of the ancients, can never be estimated. That it is 
 much is evidenced by the astonishing results of but a few years 
 of modern progress. It is even more strikingly shown by the 
 very discoveries which, in spite of all obstacles, those keen and 
 highly-trained minds achieved, and by the wonderful sagacity 
 they displayed a sagacity which, in view of their limitations, 
 would seem almost to resemble inspiration. 
 
 Thus, the principles involved in Hero's machines remained 
 unrecognized and without result, and we find, accordingly, 
 Vitruvius, a Roman architect at the beginning of the Christian 
 era, describing, without the least reference to previous inven- 
 tions, and apparently without the least perception of its rela- 
 tions to them, an apparatus called the ceolipile. This famous 
 apparatus consisted simply of a hollow metallic ball with a 
 small hole in it. That is all ! The ball being heated and the 
 inclosed air rarefied, it was then immersed in water. A quan- 
 tity of water having thus been sucked in as the heated air in the 
 ball cooled and contracted, the ball was taken out of the water, 
 and again heated. Of course, steam was formed, which would 
 for some time issue from the hole with considerable force.
 
 22 THE vSTEAM-ENGINE AND THE INDICATOR. 
 
 The ^-Eolipile. 
 
 This machine with some modifications is susceptible of a very 
 fair degree of efficiency, and no doubt it is quite within the 
 bounds of possibility that this instrument may yet displace the 
 cylinder and piston now so universally employed. 
 
 Its principle and mode of action will be understood from 
 Figure i, where C represents a globe moving freely on its axis 
 in such a manner as to permit the constant introduction of 
 steam from the boiler A through the tube B. 
 
 FIG. i. 
 
 The steam escapes through the bent tubes EE, and gives, by 
 its reaction, a rotary motion in the direction of the arrows. 
 From the collar F on the centre of the globe, motion could be 
 given to machinery. 
 
 This, no doubt, is the original rotary steam-engine. Hero 
 also describes another apparatus, in which A is a globe, see 
 Figure 2, partially filled with water, which is converted into 
 vapor by the application of heat. A pressure is produced on 
 the surface of the water, which is consequently driven up 
 through the syphon B, into the vessel E, from which it descends 
 by the pipe D, into the close vessel C, also partially filled with
 
 WHO INVENTED THE STEAM-ENGINE? 33 
 
 water. When the globe A cools, the water it contains is re- 
 lived from the greater part of its pressure by condensation of the 
 steam, and the water rises from the vessel C through the pipe 
 F, to supply what had been driven over by the elasticity of the 
 vapor. 
 
 FIG. 2. 
 
 There is no doubt that the Egyptian priests used the pres- 
 sure of vapors in performing their mysteries in and about their 
 temples. 
 
 Giovanni Batista Porta, in 1606, published a translation of 
 Hero's "Spiritalia" and added a description of an apparatus by 
 which the pressure of steam might be made to raise a column 
 of water. 
 
 Porta was known as an educated gentleman, a mathematician, 
 chemist, and physicist, and was a man of large means. The 
 invention of the magic lantern and the camera obscura are 
 attributed to him; these inventions are described in his com- 
 mentary on the " Pneumatica. "
 
 24 THE STEAM-ENGINE AND THE INDICATOR. 
 
 Porta's machine for raising water by steam pressure is shown 
 in Figure 3. 
 
 The retort or boiler, A, has a long neck, which passes through 
 the bottom of the air-tight cistern B. A bent pipe or syphon C, 
 is fitted into the top of the cistern, and descends nearly to the 
 bottom. When the fire is lighted under A, the steam ascends 
 
 c 
 
 FIG. 3. 
 
 in the cistern, and presses upon the water, and forces it up the 
 syphon C, into the atmosphere, or it may be led to any desired 
 height. This was called by Porta an improved ' ' steam foun- 
 tain." 
 
 He also described with accuracy the action of condensation in 
 producing a vacuum, and sketched an apparatus in which the 
 vacuum thus secured was filled by water forced in by the pres- 
 sure upon it of the external atmosphere. 
 
 Here, then, are some of the essential principles of the steam- 
 engine of to-day. 
 
 Porta's contrivance is the first in which the boiler is separate 
 from the "forcing vessel" which later inventors claim as ori-
 
 WHO INVENTED THE STEAM-ENGINE? 25 
 
 ginal with them, and claim special distinction on account 
 thereof. 
 
 Anno Domini 540, Athemius, an architect, arranged several 
 cauldrons of water, each covered with the wide bottom of a 
 leathern tube, which rose to a narrow top, with pipes .extended 
 to the rafters of the adjoining building. A fire was kindled be- 
 neath the cauldrons, and the house was shaken by the effect of 
 the steam ascending the tubes. This is the first notice of the 
 power of steam recorded. 
 
 In 1543, June 17th, Glasco de Garoy exhibited a boat of 209 
 tons, propelled by steam with tolerable success, at Barcelona, 
 Spain. The apparatus consisted of a cauldron of boiling water 
 to generate steam, a crude engine, and a movable wheel on 
 each side of the boat. It was laid aside as impracticable. 
 
 Salomon de Caus, in 1615, an engineer of mark, published a 
 work at Frankfort in which he describes a machine designed to 
 raise water by the expanding power of steam. 
 
 This machine, like that of Porta, consisted of a metal vessel 
 partly filled with water, in which a pipe was fitted, leading 
 nearly to the bottom, and open at the top. Fire being applied, 
 the steam formed by its elastic force drove the water out through 
 a vertical pipe, raising it to a height limited by the strength of 
 the vessel. 
 
 Very little improvement upon the contrivances described by 
 Hero was made for many centuries. The expansive properties 
 of steam must have been tolerably widely known, but apparently 
 no serious attempt was made to utilize them. So marked is this 
 circumstance that the actual steam-engine may be truly consid- 
 ered an invention of the lyth century. 
 
 The first useful application of steam power on a large scale 
 appears to have been by Edward Somerset, second Marquis of 
 Worcester, about AD, 1650. The apparatus employed consisted 
 of an independent steam generator, and two separate strong ves- 
 sels. One of these vessels being filled with cold water, steam was 
 admitted into it from the generator, and, pressing directly upon 
 the surface of the water, the latter was forced upwards through 
 an ascending pipe, to a height of about forty feet. Vessel No. i 
 being emptied of water in this way, the steam was turned off 
 from it, and on to vessel No. 2, No. i being then refilled by man-
 
 26 THE STEAM-ENGINE AND THE INDICATOR. 
 
 ual labor. Obviously a great deal of the steam must have con- 
 densed without doing any work; and considerable inconvenience 
 must have arisen from the necessity of refilling the vessels by 
 hand. Thomas Savery removed the latter inconvenience about 
 the year 1697. Savery's apparatus was somewhat similar to the 
 last, but when the vessels became emptied of water and filled 
 with steam, he cut off communication, both with the ascending 
 water pipe and the steam generator, and, opening communica- 
 tion between the vessel and the water supply, condensed the 
 steam in the forcing vessels by the external application of cold 
 water. A vacuum being thereby formed in the forcing vessel, 
 a fresh supply of water was caused to flow into it by the pressure 
 of the atmosphere. This machine was one of the first to do 
 useful work. This apparatus was used for raising water at 
 Vauxhall, London, and at Raglan Castle, his home. 
 
 With the Marquis, therefore, we reach the first practical 
 application of the power of steam. But, looking back now over 
 the ground from Archimedes to De Caus, we fail still to find the 
 least real progress in the knowledge or apprehension of funda- 
 mental principles. Thus far only known facts have been var- 
 iously combined. Twenty centuries have passed with scarcely 
 a practical result, and without any clearer insight into the laws 
 and principles involved than in the beginning. The ball of 
 Hero and the seolipile disappear, only to reappear again in some 
 slightly changed form, and constitute eventually all that is 
 known. Progress in natural laws implies investigation of 
 nature, and the time when this truth begins to be recognized 
 we have now but just reached. All has been accomplished that 
 could have been expected from a method which ignored nature 
 and philosophy which dogmatized about that which it could 
 not comprehend. But with the seventeenth century comes a 
 change and a great awakening from the slumber of ages. Men 
 like Descartes, Kepler and Galileo appear, and real progress be- 
 gins. Compare now this progress of only two centuries in 
 every department and in all directions with the preceding twenty, 
 and what we owe to science to-day becomes apparent. Torri- 
 celli, in 1643, following in the footsteps and working in the 
 spirit of his illustrious master, Galileo, was the first to prove 
 experimentally the weight and pressure of the atmosphere.
 
 WHO INVENTED THE STEAM-ENGINE? 2J 
 
 Otto von Guericke followed, with his air pump and hemi- 
 spheres, and forces the unwilling and tardy conviction of a skep- 
 tical world. Unwilling conviction! for the old beliefs died 
 hard, as the life and sufferings of Galileo sufficiently attest. 
 Torricelli's demonstration of the pressure of the atmosphere 
 produced at first only opposition. Old dogmas and long-estab- 
 lished beliefs proved very tenacious of life. They still live, and 
 die hard. 
 
 It is not surprising, then, that Torricelli's discovery remained 
 for a long time unheeded. The progress of these two centuries 
 is well illustrated by the fact that such a discovery made to-day 
 would be known, repeated by thousands of independent obser- 
 vers, and accepted by the scientific world within 48 hours. In 
 that day, however, it was not until 1646, three years later, that 
 Pascal first heard of Torricelli's discovery and repeated it. He 
 rejected at first, however, Torricelli's interpretation, and con- 
 cluded that "nature's abhorrence of a vacuum was limited." 
 As Galileo sarcastically expressed it, " Nature only abhorred a 
 vacuum as high as 30 inches." The sarcasm of Galileo ex- 
 pressed the serious belief of Pascal. One would naturally sup- 
 pose that the ecclesiastics would have welcomed a conclusion 
 from such an authoritative source, so entirely in sympathy with 
 their methods of thinking; but, on the contrary so inconsistent 
 is dogmatism the scholars attacked Pascal with virulence, for 
 "daring to limit the powers of nature," until, excited by their 
 ignorant opposition, and enraged by their savage attacks, he 
 returned to the investigation anew, and brilliantly demonstrated, 
 beyond cavil, the truth of Torricelli's position. 
 
 He reasoned that if Torricelli were right, and if the mercury 
 column in the barometer tube were really sustained by the pres- 
 sure of the atmosphere, its height must be less when taken to 
 the top of a high mountain, where there is less air above it, 
 than in the plain below, where there is more. On the 2Oth of 
 September, 1646, just at the close of the Thirty Years' War, he 
 tried the experiment on the summit of the Puy de Dome, at 
 Clermont. It was completely successful and conclusive, and 
 the joyful peals of Miinster and Osnabruck, which still lingered 
 in the air, as they rang out the long and dreary war, fitly rang 
 in the triumph of science, and a more glorious victory than they
 
 28 THE STEAM-ENGINE AND THE INDICATOR. 
 
 knew. Otto von Guericke followed up the proof by his inven- 
 tion of the air pump, by which he pumped air out of vessels 
 like so much water, and so multiplied proofs of the most strik- 
 ing character that no room for doubt remained, even to the 
 most intolerant dogmatizer of them all. Here we have reached, 
 in my opinion, the true germ of the steam engine. It begins 
 right here, and it could not possibly begin before. All attempts 
 hitherto made have been merely gropings in the dark. 
 
 From the moment when the action of the atmosphere was 
 rightly apprehended, and thus the true significance of a vacuum 
 understood, the steam engine became an inevitable consequence. 
 Torricelli, with his barometer tube, sowed the seed of which we 
 reap the fruits to-day. Was not Torricelli's tube a mere mar- 
 velous toy also? like the seolipile, the fountain, the priest and 
 the altar? No! for these were only detached facts, divorced 
 from their true significance, while that illustrated and made 
 clear a principle. Principles are fruitful, and lead to innumera- 
 ble results ; facts alone are barren when they do not lead to prin- 
 ciples. Torricelli planted better than he knew, and the results 
 of that simple experiment, just because it was an experiment, 
 a questioning of nature, will reach through all the future ages 
 of man's life upon this earth, just as it now clothes and feeds a 
 world. That simple experiment marks an epoch, and a most 
 memorable epoch. We can scarcely conceive at this day the 
 momentous importance of this simple, and to us most evident, 
 fact of atmospheric pressure. 
 
 We have been born and brought up in the knowledge of it, 
 and accept it as the air we breathe. The significance of a 
 vacuum, as a space devoid of air upon which the outside air 
 pressure was unbalanced, began now to be appreciated. At- 
 tempts are at once made to utilize this astonishing air-power 
 by producing a vacuum, and a new era begins. Many devices 
 were suggested and tried for this purpose, but remained without 
 result, until Papin in 1690 first suggested the condensation of 
 steam for the production of a vacuum. Many other substances 
 expand when heated and contract when cooled, but when it is 
 stated that one cubic foot of steam under ordinary pressure con- 
 tracts to about one cubic inch of water when cooled, its peculiar 
 fitness for the purpose suggested, namely, the production of a
 
 WHO INVENTED THE STEAM-ENGINE? 29 
 
 vacuum, becomes at once apparent. The fact of the condensa- 
 tion of steam was by no means unknown before, but only now 
 has the time arrived when that fact stands out in its true signi- 
 ficance as a means of producing a vacuum, and thus making the 
 air do work. Papin recognized the advantages which the use 
 of steam presented, and endeavored to utilize it. Here, then, 
 we have a steam engine, or rather, an "atmospheric engine," 
 as it may be called, because it is really the pressure of the at- 
 mosphere which furnishes the power, and steam is only used to 
 produce a vacuum. Thus we have for the first time an engine 
 the principles of whose action are comprehended. To Papin, 
 then, as much as to any one man, is due the honor of the con- 
 ception of a steam engine in the light of a proper comprehension 
 of the principles involved and the end to be attained. It is, of 
 course, but a beginning. It simply points out the way, and in 
 itself, in its present shape, is of no practical utility whatever. 
 Indeed, so evident were its defects that Papin himself abandoned 
 it as impracticable. Improvement, however, is but a matter of 
 detail when once principles are clearly recognized. Here is 
 the central idea clearly apprehended and illustrated. The way 
 is at last opened, Savery in 1698 having learned from Papin 
 the manner of condensing steam and forming a vacuum, by 
 making use of the direct pressure of expanding steam as well 
 as the pressure of the atmosphere obtained by condensing the 
 steam. 
 
 This being one step in advance and nearer to the steam 
 engine of to-day, was the first practical machine, and was to some 
 extent actually used for raising water. This engine was no 
 doubt suggested by Papin's engine. But the defects of Savery's 
 engine were many; the most serious was the enormous con- 
 sumption of fuel for the work done. 
 
 Newcomen and Cawley, mechanics of Dartmouth, England, 
 appear to have been the first to apply the cylinder and piston to 
 the purposes of steam power. In their engine, constructed 
 about the year 1705, steam of low pressure was used to raise a 
 piston against the pressure of the atmosphere. The steam 
 under the piston being then condensed by the application of 
 cold water to the outside of the cylinder, and a vacuum thereby 
 formed, the piston was forced down by atmospheric pressure.
 
 30 THE STEAM-ENGINE AND THE INDICATOR. 
 
 The actual work, which consisted in this case also of raising 
 water, was performed during the downward stroke only. 
 
 Savery's engine was an "atmospheric engine," the piston 
 being forced down by the weight of the atmosphere. In the 
 engine originally patented the steam was condensed by the 
 application of cold water to the outside of the cylinder, or by 
 surface condensation. 
 
 These inventors also accidentally discovered that steam could 
 be condensed much faster by admitting a jet of cold water into 
 the cylinder itself than by water applied externally to the cyl- 
 inder. And with them originated the principle of jet injection. 
 
 The number of great discoveries made by pure accident is 
 very few. Nature discloses her secrets only to patient and per- 
 sistent inquiry. But just here we meet with an apparent excep- 
 tion a genuine and important discovery made by chance. 
 
 The piston of one of these engines was covered on top with a 
 layer of water to make it air-tight. One day the engine was 
 observed to work with great and unusual rapidity, the steam 
 seeming to be condensed more quickly than usual. Examina- 
 tion showed that the wearing away of the piston had allowed 
 water to enter the cylinder and come into direct contact with 
 the steam. Thus was discovered the fact of condensation by 
 means of water injected into the cylinder, or, as we may call it, 
 jet condensation, and Savery's share in the patent of Watt 
 became necessary. 
 
 And now a little boy takes a part in the work of development, 
 and does good service too. The cocks for the admission of 
 steam and water to the cylinder had to be turned by hand just 
 at the right moment. Evidently if the steam-cock is open too 
 long, there is danger of blowing the piston out of the cylinder. 
 The wearisome and monotonous task of watching the stroke 
 and opening and closing the cocks at the proper moment was 
 intrusted to a little boy by the name of Humphrey Potter. He 
 doubtless soon found the work rather unsatisfactory, and his 
 bright wits suggested a remedy.. He attached strings to the 
 walking-beam and to the cock-handles in such a manner that 
 the machine was made to watch itself and turn the cocks itself. 
 Simple as it is, this contrivance, suggested by the desire of a 
 boy to join the sports of his playfellows, constituted one of the
 
 WHO INVENTED THE STEAM ENGINE? 3! 
 
 most important improvements in detail ever made to the steam 
 engine. It was at once adopted by Newcomen, and was the 
 origin of the so-called "plug frame" and valve gear of to-day. 
 
 John Fitch, a native of Windsor, Conn., and James Rumsey, 
 a native of Maryland, were the first in America who made the 
 attempt to propel boats by steam. 
 
 Fitch was the first to commence building his boat in 1783,1 
 but did not complete it so as to try his experiment until 1787. 
 His attempt was to apply steam power to oars. He launched 
 the boat and made the trial on the Delaware; but his machinery 
 proved insufficient and ill-adapted to the purpose of navigation. 
 This was his first and last experiment, although he retained full 
 faith in the ultimate success of steam for propelling boats. 
 
 Rumsey commenced building his boat later in the year 1783 
 than Fitch, in Shepherdstown, near his residence on the southern 
 bank of the Potomac, and launched it in 1786. His first effort 
 was the application of steam power to a pump, by which he 
 sought to propel the boat by drawing in water at the bow and 
 pouring it out at the stern. This proved inadequate for loaded 
 boats or river navigation against the current. He then at- 
 tempted to apply his steam power to setting-poles, but without 
 success, and abandoned his project with no further trial. 
 
 Nathan Read,* a native of Western (now Warren), Mass., an 
 apothecary in Salem, Mass., and afterward a member of Con- 
 gress from Danvers, Mass., noticed the failures of Fitch and 
 Rumsey, and believed they were occasioned by their ill-con- 
 structed machinery; that their long awkward oars, and still 
 more awkward pumps and setting-poles, condemned themselves 
 as unsuited to the purpose for which they were designed. Ac- 
 cordingly, in 1789, eighteen years before Fulton appeared with 
 his experiments upon the Hudson, Mr. Read successfully in- 
 vented and constructed a steamboat of sufficient size to carry a 
 man, and safely propelled himself across an arm of the sea 
 which separates Danvers from Beverly. His boat was con- 
 structed with two paddle-wheels, fixed to an axis which extended 
 across the gunwale of the boat, precisely on the same principle 
 as applied at the present day to all steamboats propelled by 
 paddle-wheels. 
 
 * Nathan Read : A contribution to the early History of the Steamboat and 
 Locomotive Engine, by his friend and nephew David Read, New York, 1870.
 
 32 THE STEAM-ENGINE AND THE INDICATOR. 
 
 Undoubtedly this was the first steamboat ever built, and the 
 first voyage ever taken in a steamer constructed upon the same 
 plans and principles as our present boats. The Rev. Dr. Prince, 
 of Saleni, and several other gentlemen, were present on this oc- 
 casion and witnessed this successful experiment of Mr. Read. 
 
 At this time he invented and constructed a portable furnace 
 tubular boiler, with the suitable machinery attached to give it 
 locomotion, and made a model of a locomotive steam carriage, 
 and applied for a patent February 8, 1790. This was before 
 any patent laws or regulations had ever been established by the 
 government. At this time Congress was in session in New 
 York, and Mr. Read spent the most of the winter of 1790 in the 
 latter city. He had letters of introduction from Gen. Benjamin 
 Lincoln to President Washington, and members of Congress 
 arid other gentlemen of New York City. He was finally re- 
 warded by having his application granted him. The application 
 and petition to Congress were accompanied by a recommenda- 
 tion from a select committee of the American Academy of Arts 
 and Sciences, setting forth his various discoveries as follows : 
 
 "An improvement in distillation by a new still and refrigera- 
 tory. 
 
 "Obtaining a perpetual tide fountain for water works, keep- 
 ing pumps, mills, carding machines, etc., constantly at work 
 from the accumulated forces of the wind. 
 
 "An economical portable steam engine. 
 
 "Application of steam to purposes of navigation and land 
 carriages. 
 
 "A method of constructing perpetual chronometers and self- 
 moving planetaries. " 
 
 That Mr. Read has not been accorded justice, as being the 
 original inventor of the successful application of steam power 
 for locomotion, is apparent from a glance at the statements of 
 the experiments made previous to this date. Want of space 
 here will only permit of a brief mention of them. 
 
 The Marquis of Worcester made the first experiments in this 
 direction as early as 1655, and expressed his belief that steam 
 power might be used for propelling vessels, but he never tried 
 the experiment. 
 
 In 1680 Prince Rupert made an unsuccessful attempt to
 
 WHO INVENTED THE STEAM-ENGINE? 33 
 
 propel a boat on the Thames by steam, but it was an utter 
 failure. 
 
 Savery, an Englishman, about 1698, is supposed to have been 
 the first to apply steam power to any practical purpose. He 
 used it for pumping water from the mines in Cornwall, and ex- 
 pressed the idea that he could turn paddle-wheels on the outside 
 of a vessel if connected with his pumping engine; but there is 
 no record of his ever having tried the experiment. 
 
 In 1707 Denys Papin introduced his steam machine for rais- 
 ing water in one instant to an elevation of 70 feet. In 1710, 
 Newcomen made the first steam-engine in England. In 1718 
 patents were granted to Savery for the first application of the 
 steam-engine. 
 
 The high-pressure engine with two cylinders was proposed by 
 Leupold about A. D., 1725. The compound system of working 
 steam in two cylinders originated with Hornblower, and was 
 improved upon by Woolf. 
 
 In 1736, Jonathan Hulls set forth in a publication the idea of 
 steam navigation. 
 
 James Watt in 1759 had his attention directed by Dr. Robi- 
 son to the subject of the steam-engine, and for a few years after 
 wards made various experiments on the properties of steam. 
 
 The progress which he made was marvelous. He discovered 
 all the laws which we now know with almost perfect precision, 
 and he showed us how to apply them to produce results in al- 
 most perfect accordance with those laws under which steam 
 must act. 
 
 Let us catalogue what this great genius did. He discovered 
 the essential truth that steam must be condensed in a vessel 
 other than the cylinder in which it is used to produce power: 
 and he invented the application of the air-pump to the con- 
 denser in order to make a true steam-engine that is, an engine 
 from which air is excluded, and in which the piston works be- 
 tween two vessels, the boiler and condenser, each of which con- 
 tains steam, but of different pressures, the power resulting from 
 that difference. 
 
 He invented two forms of condensers the "jet condenser," 
 in which the steam is cooled by a spray of cold water injected 
 into it, to be used when fresh water is available, and the "sur- 
 3
 
 34 THE STEAM-ENGINE AND THE INDICATOR. 
 
 face condenser," in which the steam is separated from the cold 
 water by a thin partition of metal, and is condensed by contact 
 with the cold surfaces. Without this last invention our 
 modern steamships could not carry high-pressure steam in their 
 boilers, and could not attain their wonderful speed. 
 
 He discovered the law under which steam used expansively 
 increases its power in a certain ratio; and he invented the best 
 form of cut-off for utilizing this discovery known to man, until 
 it was rmproved, upon the same principles, by Sickles, Corliss, 
 Thompson, and others. 
 
 Watt, by his investigation of the action of steam in the 
 cylinder of the Newcomen engine, revealed the fact and im- 
 portance of that waste by cylinder condensation, which is only 
 to-day becoming recognized as an essential element in the 
 theory of the "real" steam engine of the engineer, as dis- 
 tinguished from the u ideal" engine of the authors of the theory 
 of thermodynamics, and which is recognized as imperatively 
 demanding consideration, if that theory is to be made of prac- 
 tical use in engineering. 
 
 Watt's discovery of this "cylinder condensation" led him to 
 the invention of his separate condenser, and of the long 
 neglected but now familiar steam jacket, an attachment which 
 was, for many years, only seen upon the Watt's Cornish 
 engine, and was almost never used elsewhere. It has now 
 come in with the compound engine, and is familiar to every 
 engineer. 
 
 He invented the "Indicator," an instrument which gives us 
 a graphic representation of the force exerted by the steam, and 
 proves the truth of the laws he discovered. 
 
 He invented the "fly- ball governor" for maintaining uniform 
 speed of the engine under varying conditions of load and 
 pressure. 
 
 He also invented a great number of subordinate details too 
 numerous to mention here; and, as if to admonish the world 
 not to depart from these principles, he invented the "copying 
 press" now in common use everywhere. 
 
 When he died he seems to have left no successor capable of 
 appreciating the discoveries he made, and for a generation after 
 his death the art of producing power from fuel by the interveu-
 
 WHO INVENTED THE STEAM-ENGINE? 35 
 
 tion of a steam engine retrograded, so that less power was 
 obtained from a pound of coal consumed than could be obtained 
 by the use of methods invented and fully explained by James 
 Watt. 
 
 The problem is to convert the work of combustion into 
 dynamic power, and that steam engine is the best which can 
 obtain the most power from the least coal. 
 
 These three laws are the key to the whole problem, and they 
 were all discovered by James Watt: 
 
 First A cubic inch of water converted into steam, will lift 
 a ton a foot high. 
 
 Second It costs no more fuel to evaporate a cubic inch of 
 water at the pressure of 200 pounds to the sqnare inch than it 
 does to evaporate it in an open vessel ; and 
 
 Third The gain of power depends upon the number of times 
 the compressed steam is permitted to expand after it has done 
 the work of lifting a ton a foot high. 
 
 Founded upon these principles, the steam engines which 
 were made by Watt and his associates and pupils, before 1830, 
 produced a horse-power with less than two pounds of coal an 
 hour. These engines are known as the Cornish pumping en- 
 gines; and if we look into the history of these machines, we 
 will find them reported as doing a "hundred millions of duty," 
 which is a technical phrase intended to express the fact that a 
 hundred million pounds of water were lifted a foot high for a 
 hundred weight of coal consumed. Turning that into horse- 
 power, it means about two pounds of coal per hour per horse- 
 power. This result was produced by cutting off steam in the 
 cylinders at one-eighth or one-tenth of the stroke, and allowing 
 it to expand eight or ten times. The engines of that day, 
 of course, were very imperfectly constructed, and great losses 
 occurred from leaking pistons and from imperfectly constructed 
 boilers; but notwithstanding that loss, the result was equal to 
 two pounds of coal per hour per horse-power. 
 
 Reconstruct these engines with the tools and machinery of 
 to-day, and the result would be appreciably higher. Or, in 
 other words, an engine expanding steam ten times, and evapor- 
 ating eight pounds of water to a pound of coal in the boiler, 
 and without any losses from leakage, ought to make a horse-
 
 36 THE STEAM-ENGrNE AND THE INDICATOR. 
 
 power with a pound and a half of coal an hour. These results 
 were obtained by obeying Watt's laws, already stated, as nearly 
 as it was possible then to do. 
 
 The work of Watt in the systematic experimental study of the 
 steam engine was not taken up by his successors in the pro- 
 fession until about 1850, when it was done by G. A. Hirn, and 
 others. 
 
 Watt made the first perfect steam engine in 1764. 
 
 Thomas Paine first proposed the application of steam naviga- 
 tion in America in 1778. 
 
 In 1785 two Americans published a work on the steam 
 engine. 
 
 Oliver Evans, a native of Philadelphia, constructed a locomo- 
 tive or steam carriage to travel on turnpike roads in 1793. 
 
 The French Academy of Sciences having offered a prize for the 
 successful application of steam power for the propelling of ves- 
 sels, one Bonouville wrote an essay in 1753, in which he 
 demonstrated the principle that it could be accomplished by 
 the rotary motion only, and he won the prize as having offered 
 the most feasible plan. 
 
 Genevois, a Frenchman, tried the experiment of operating a 
 paddle in the form of a duck's foot, with an opening and closing 
 motion, but it proved a failure. 
 
 Another Frenchman, the Marquis de Jouffroy, was also an 
 unsuccessful experimenter. 
 
 It is also said that a Scotchman of the name of Miller moved 
 a boat along the Firth of Clyde canal by steam power, at the 
 rate of seven miles an hour; but Miller himself pronounced his 
 trial a failure and his machinery unfitted for the purpose. 
 
 It was not until after Watt, in 1784, produced his rotary 
 steam-engine, that it was made possible to successfully use 
 steam as a propelling power in navigation; but he never made 
 the attempt of so applying it. In fact, it was not until the in- 
 vention of the tubular boiler by Mr. Read, and his application 
 of Watt's rotary engine, that the thing was made possible in 
 1789. 
 
 At the time Mr. Read was in New York prosecuting his ap- 
 plication for a patent, in 1790, he met and explained to General 
 Stevens his drawings and models of a tubular boiler and paddle-
 
 WHO INVENTED THE STEAM-ENGINE? 37 
 
 wheels, in combination with Watt's double-acting rotary 
 engine. In the very next year General Stevens, who was a 
 man of great wealth, began his experiments in steam naviga- 
 tion, and is erroneously recorded by Renwick, in his "History 
 of the Steam-Engine," as being the inventor of the tubular 
 boiler; but it is plain that Stevens had formed no idea of a 
 tubular boiler himself, or any ideas whatever of steam naviga- 
 tion, except as derived from Read. 
 
 It was eight years afterwards, in 1797, that Chancellor Liv- 
 ingston commenced his projects with steam on the Hudson, and 
 in 1801 he went as Minister to France, and there met Robert 
 Fulton, who had been for five years experimenting unsuccess- 
 fully under the patronage of the French government. 
 
 In 1803, Livingston employed Fulton, and under his patron- 
 age made his first attempt to propel a boat by steam and paddle- 
 wheels, using Read's invention of a tubular boiler and Watt's 
 rotary engine, and in a trial on the Seine that same year, suc- 
 ceeded in attaining a rate of speed of four miles an hour. Living- 
 ston then arranged with Fulton to construct a boat of large size 
 for use on the Hudson. In this arrangement General Stevens 
 became a partner of Livingston. In the new boat they substan- 
 tially adopted the same ideas and methods of Read; the very 
 same style of tubular boiler and paddle-wheels that he invented, 
 together with one of Watt & Boulton's double-action rotary 
 engines made in England, which was delivered in New York, 
 !n 1806, and in 1807 the famous "Clermont" was launched on 
 the Hudson, and made her notable and very successful trip to 
 Albany, eighteen years after Mr. Read's successful steaming 
 across the bay between Danvers and Beverly. 
 
 The First Steamship to Cross the Ocean. 
 
 One of the most curious things in the history of Transatlantic 
 steam navigation is the claim that has been set up on the other 
 side of the water to the construction and fitting out of the first 
 pioneer Transatlantic steamers, or, more strictly speaking, to 
 the proprietorship of the first vessels which crossed the ocean 
 propelled exclusively by steam-power. These pioneers, it is 
 claimed, were the Sirius and the Great Western, the former 
 built for another class of voyages, and afterward lost on the sta- 
 
 r
 
 38 THE STEAM-ENGINE AND THE INDICATOR. 
 
 tion between Cork and London, the latter built expressly foi 
 Atlantic navigation. They made the voyage in 1838, which, 
 as will be seen, was twenty years too late for pioneers. If ' ' ex- 
 clusively propelled by steam-power," as is urged for them, 
 means that no sails were set during the passage, the claim may 
 be founded on fact, but that it is deceptive and misleading, 
 there is surely no doubt. The Savannah, an American steam- 
 ship, was the first ever built to cross the ocean, and, if she 
 carried auxiliary sails and set them when the wind was fair, she 
 did no more than every steamer has done from that time up to 
 the present, and could by no means be forced on that account to 
 forego her claim to being the first steamship that crossed the 
 seas. She was built in 1818, by Col. John Stevens, of New 
 York, and the news of her master's intention to tempt the seas 
 soon reached the English world, being heralded by the London 
 Times in its issue of May n, 1819, in the following paragraph: 
 
 "Great experiment. A new steam vessel of 300 tons has 
 been built at New York for the express purpose of carrying 
 passengers across the Atlantic. She is to come to Liverpool 
 direct." This was the Savannah, which, in May, 1819, left the 
 port of New York for Savannah, from which port she sailed, 
 under the command of Capt. Moses Rogers, bound for St. 
 Petersburg via Liverpool. She reached the latter port on June 
 20, having used steam 18 days out of the 26, and thus proved 
 the feasibility of Transatlantic steam navigation. 
 
 The Savannah, when first descried on the southern coast of 
 Ireland, was reported as a ship on fire at the mast, and moving 
 without sail. The admiral, who lay in the cove of Cork, dis- 
 patched one of the King's cutters to her relief. But great was 
 their wonder at their inability, with all sail, in a fast vessel, to 
 come up with a ship under bare poles. After several shots were 
 fired from the cutter the engine was stopped, and the surprise 
 of her crew at the mistake they had made, as well as their 
 curiosity to see the singular Yankee craft, can be easily im- 
 agined. They asked permission to go on board, and were much 
 gratified by the inspection of this novelty. 
 
 A distinguished scientist had declared long before that it was 
 not possible to cross the ocean by steam. Indeed, so sure was 
 he that it could not be done that, when he heard that Captain
 
 WHO INVENTED THE STEAM-ENGINE? 39 
 
 Rogers proposed to make the attempt, he declared that he 
 would swallow the first vessel that should safely reach the 
 British Isles from this country. It would not, therefore, have 
 seemed immodest had Captain Rogers, upon the arrival of the 
 Savannah, have called upon the savant to fulfill his promise 
 and swallow the ship. 
 
 "On approaching Liverpool, hundreds of people came off in 
 boats to see the steamship. She was compelled to lie outside 
 the bar until the tide should serve for her to go in. During 
 this time she had her colors all flying, when a boat from a 
 British sloop of war came alongside and hailed. The sailing 
 master was on the deck at the time, and answered. The 
 officer of the boat asked him, "Where is your master?" to which 
 he gave the laconic reply, "I have no master, sir." "Where's 
 your captain, then?" "He's below. Do you wish to see 
 him?" "I do, sir." The captain, who was then below, on 
 being called, asked what he wanted, to which the officer an- 
 swered, "Why do you wear that pennant, sir?" "Because 
 my country allows me to, sir." "My commander thinks it 
 was done to insult him, and if you don't take it down he will 
 send a force that will do it." Captain Rogers then exclaimed 
 to the engineer, " Get the hot water engine ready. " Although 
 there was no such machine on board the vessel, the order had 
 the desired effect, and John Bull was glad to paddle off as fast 
 as possible. 
 
 Several naval officers, noblemen and merchants from London 
 came down to visit her, and were very curious to ascertain her 
 speed, destination, and other particulars. 
 
 It is curious in looking over the English newspapers of that 
 date to see how suspiciously the English authorities regarded 
 the American steamer. America was looked upon as very 
 ambitious, and an enterprise like this on the seas, filled the 
 British breast with great alarm. It seems that Napoleon being 
 now in captivity at St. Helena, his brother had offered a large 
 reward to whoever should rescue him, or rather there was, it 
 would appear, a rumor to that effect, and the British press was 
 sure that this Yankee steamer was in European waters for no 
 other purpose. 
 
 The Savannah remained nearly a month in British waters.
 
 40 THE STEAM-ENGINE AND THE INDICATOR. 
 
 On the 23d of July, the Savannah set out for St. Petersburg, 
 under steam. She stopped at Copenhagen and also at Stock- 
 holm, where, as in England, she was the object of general 
 attention, being visited by all the members of the royal family 
 and the nobles. Captain Rogers' diary says: "Mr. Huse 
 (Christopher Hughes, the American Minister) and lady, and all 
 the Furran ministers and their Laydes, of Stockholm, came on 
 board." In her passage up the Baltic, and while lying in the 
 port of Cronstadt, she was saved from wreck during a terrible 
 storm, in which many vessels were lost, only by the assistance 
 rendered by her paddles. While at Stockholm, Captain Rogers 
 took aboard, as an invited guest, Lord Lynedock, a distinguished 
 English general, who made the journey to St. Petersburg 
 aboard the steamer. When he left the ship, he presented Cap- 
 tain Rogers with a massive gold-lined tea-kettle. This tea- 
 kettle is yet preserved by the descendants of Captain Rogers. 
 It bears the following inscription: 
 
 "Presented to Captain Moses Rogers, of the steamship Sav- 
 annah (being the first steam vessel that had crossed the At- 
 lantic), by Sir Thomas Graham, Lord Lynedock, a passenger 
 from Stockholm to St. Petersburg, September i5th, 1819." 
 
 During her stay at St. Petersburg, Alexander, Emperor of 
 the Iron North, pleased with the novel idea of a steamship, 
 presented Captain Rogers with two iron chairs, one of which 
 (one of the only relics left of the adventurous bark) was up to a 
 late period in the possession of Mr. Dunning, of Savannah. 
 
 The Savannah sailed for America on October loth, 1819, and 
 reached Savannah, Ga., November 3oth. 
 
 Thus it will be seen that the Savannah, which, by the way, 
 was lost off the south side of Long Island, anticipated the 
 alleged steam pioneers Sirius and Great Western by nearly 
 twenty years. 
 
 And to-day, viewing one of those gigantic engines to be seen 
 in some of our large steamboats, who will deny that there is 
 something awfully grand in the contemplation of it? Stand 
 amidst its ponderous beams and bars, its wheels and cylinders, 
 and watch their increasing play, how regular, yet how wonder- 
 ful ! A lady's Waltham watch is not more nicely adjusted the 
 rush of the waterfall is not more awful in its strength. Old
 
 WHO INVENTED THE STEAM-ENGINE? 41 
 
 Gothic cathedrals and ruined abbeys are solemn places, teach- 
 ing solemn lessons touching solemn things; but to the contem- 
 plative mind, a steam engine can teach a solemn lesson too: 
 it can tell him of mind wielding matter at its will; it can tell 
 him of intellect battling with the elements; it can tell him of 
 genius to invent, skill to fashion, and perseverance to finish. 
 
 Many men of genius fill obscure graves in whose souls the 
 living fire of poetry, or the bright sparks of genius, lay hidden 
 and lost, merely wanting opportunity or fortuitous circum- 
 stances to have enabled them to shed a lustre over their race. 
 And in some retired spot, may remain the mortal tenement 
 from which the soul of an Arkwright, a Davy, a Watt, an Evans, 
 or a Webster may have fled, which merely wanted education 
 and opportunities for this development. The fact should be a 
 lesson to those who laugh at novelties and put no faith in fur- 
 ther invention, that the mighty steam engine, the tritfmph of 
 art and skill, was once the laughing stock of jeering thousands, 
 and once the waking dream of a boy's mind, as he sat, and in 
 seeming idleness, mused upon a small column of steam spouting 
 from a tea-kettle. 
 
 To Watt, however, must always be awarded the first place 
 amongst the inventors and improvers of the steam-engine. 
 For, although the scope of its application and usefulness has 
 since been much extended, and numberless improvements in 
 detail have been effected, the principles and action of the steam- 
 engine remain much as Watt left them, nor has the economy of 
 its running been greatly increased.
 
 CHAPTER III. 
 
 HEAT AND WORK. 
 
 THE materiality of heat was discredited even by the earliest 
 of philosophers, whose writings are preserved to us, and specu- 
 lations were originated which indicate great philosophic intui- 
 tion, and at some points approach very closely to the theories 
 now almost universally accepted. 
 
 These, however, were hypotheses merely until Rumford 
 proved experimentally that heat could not be a material sub- 
 stance, but was probably a manifestation of work, Mayer 
 suggested the identity of heat with work, and the interchange- 
 ability of heat and motive force. Joule proved by a long series 
 of experiments that the production of heat was attended by the 
 disappearance of a definite amount of mechanical work. 
 
 The labors of Mayer and Joule resulted in the important 
 discovery of the dynamical value of heat, or as it is usually 
 termed, the mechanical equivalent of heat. This was found to 
 be equal to 772 foot pounds for a degree Fahrenheit, communi- 
 cated to one pound of water at its greatest density. 
 
 On the basis of this important discovery, and mainly by the 
 labors of Rankine and Thomson, the experimental and other 
 investigations of Black, Carnot, Rudberg, Regnault, and others 
 have been elaborated into the science of thermodynamics. 
 
 The knowledge which the above law gives us is exceedingly 
 valuable. From it we learn that in the very best engines that 
 can be made, we are getting only about ten per cent, of the 
 actual power of the coal employed. 
 
 If we take a condensing engine averaging 350 horse-power, 
 with a consumption per hour of 630 pounds of coal on the fire- 
 grate, the consumption per hour per horse-power will be: 
 
 -2 = 1.8 pounds of coal. 
 
 The average anthracite coal contains about eighty-five per 
 (42)
 
 HEAT AND WORK. 43 
 
 cent, of carbon. Throwing away the other constituents, we are 
 burning eighty-five per cent, of 1.8 pounds of pure carbon; or 
 
 Carbon = 1.8 X 0.85 = 1.53 pounds. 
 
 Experiments show that a pound of carbon generates, while 
 burning to carbonic acid, 14,500 units of heat, that is, it gives 
 off as much heat as will raise 14, 500 pounds of water one degree 
 Fahrenheit; and therefore 1.53 pounds will generate 
 
 14,500 X 1.53 = 22,185 units of heat. 
 
 We are, therefore, generating in round numbers 22,000 units 
 of heat, and getting in exchange one indicated horse-power. 
 
 Above we have seen that one unit of heat is equivalent to 
 772 pounds raised one foot high; and therefore 22,000 units of 
 heat are equivalent to 
 
 22,000 X 772 = 16,984,000 foot pounds. 
 
 But an indicated horse-power means 33,000 pounds raised one 
 foot high per minute, which is equivalent to 33,000 multiplied 
 by 60 minutes: 
 
 33,000 X 60 = 1,980,000 foot pounds per hour. 
 
 From this we see that we are burning coal sufficient to raise 
 
 16,984,000 foot pounds. 
 
 16,984.000 
 1,980,000 
 
 Therefore we are, in fact, out of one of the very best steam 
 engines, getting but one-ninth, or about ten per cent, of the 
 power we should do: 
 
 100 8.58 = 91.42 or ten per cent. 
 
 Water. 
 
 Water was supposed to be an element until the latter part of 
 the eighteenth century, when Priestley discovered that when 
 hydrogen was burned in a glass tube water was deposited on 
 the sides. 
 
 It is due to Cavendish and Lavoisier, who investigated water, 
 that its chemical composition was determined. 
 
 The several conditions of water are usually stated as the 
 solid, the liquid and the gaseous. Two conditions are covered
 
 44 THE STEAM-ENGINE AND THE INDICATOR. 
 
 by the last term, and water should be understood as capable of 
 existing in four different conditions the solid, the liquid, the 
 vaporous and the gaseous. At and below 32 Fahr. water ex- 
 ists in the solid state, and is known as ice. According to 
 Rankine, ice at 32 has a specific gravity of 0.92. Thus a cubic 
 foot of ice weighs 57.45 pounds. 
 
 When water passes from the solid to the liquid state, heat is 
 required for liquefaction sufficient to elevate the temperature of 
 one pound of water 143 Fahr. This is termed the latent heat 
 of liquefaction. According to M. Person, the specific heat of 
 ice is 0.504, and the latent heat of liquefaction 142.65. 
 
 From 32 to 39 the density of water increases; above the 
 latter temperature the density diminishes. 
 
 Water is said to be at its maxium density at 39 Fahr, and 
 under pressure of one atmosphere weighs, according to Berze- 
 lius, 62.382 pounds per cubic foot. 
 
 Water is said to vaporize at 212 Fahr, and at a pressure of 
 14. 7 pounds (one atmosphere), but Faraday has shown that vapor- 
 ization occurs at all temperatures from absolute zero, and that 
 the limit to vaporization is the disappearance of heat. Dalton 
 obtained the following experimental results on evaporation be- 
 low the boiling temperature: 
 
 Temp. Rate of Evaporation. Barometer. 
 
 212 i.oo 29.92 
 
 180 0.50 15.27 
 
 164 0.33 10.59 
 
 152 0.25 7.93 
 
 144 O.2O 6.49 
 
 138 0.17 5.57 
 
 From this, the general law is deduced that the rate of surface 
 evaporation is proportional to the elastic force of the vapor. 
 
 Thus, suppose two tanks of similar surface dimensions and 
 open to the atmosphere, one containing water maintained con- 
 stantly at 212 Fahr., and the other containing water at 152 . 
 Fahr. 
 
 Then for each pound of water evaporated in the last tank, 
 four pounds will be evaporated in the first tank. 
 
 It should be understood that the law of Dalton holds good 
 only for dry air, and when the air contains vapor having an
 
 HEAT AND WORK. 45 
 
 elastic force equal to that of the vapor of the water, the evapo- 
 ration ceases. 
 
 The boiling point of water depends upon the pressure. Thus 
 at 14.7 pounds (barometer 29.22") the temperature of ebullition 
 is 212*. With a partial vacuum, or absolute pressure of one 
 pound (2.037 inches of mercury) the boiling point is 101.36 
 Fahr. 
 
 Upon the other hand, if the pressure be 89. 7 pounds absolute 
 (75 pounds by the gage), the temperature of evaporation be- 
 comes 320. 10 Fahr. 
 
 The vaporous condition of water is limited to saturation. 
 That is to say, when water has been converted by heat into 
 steam (vapor), and when this steam has been furnished with 
 latent heat sufficient to render it anhydrous, the vaporous con- 
 dition ends and the gaseous state begins. Superheated steam 
 is water in the gaseous state. Steam exists only as saturated 
 and as superheated steam. 
 
 The temperature of the gaseous state of water, like that of the 
 vaporous, depends upon the imposed pressure. Under pressure 
 of 14.7 pounds, water exists in the solid state at and below 32 
 Fahr., from 32 to 212 it exists in the liquid state, at and 
 above 212 in the vaporous state, and above saturation in the 
 gaseous state. 
 
 It has been stated that water boils at 212, but MM. 
 Magnus and Donney have shown that when water is freed of 
 air and is elevated in temperature to 170, it will boil. 
 
 The specific heat of water under the several conditions is as 
 follows: 
 
 Solid, 0.504 Vaporous, 0.475 to i.ooo. 
 
 Liquid, i.ooo . Gaseous, 0.475. 
 
 Boiling. 
 
 The temperature at which the formation of vapor takes place 
 internally as well as on the surface of a liquid, is called the 
 boiling point, and depends on the essential nature of the liquid 
 and the superincumbent pressure. Water boils at 212 Fahr. 
 under the normal atmospheric pressure of 29.92 inches of 
 mercury, equal to a pressure on the square inch of 14.696 
 pounds, very nearly. It is common to say that an atmopshere
 
 46 THE STEAM-ENGINE AND THE INDICATOR. 
 
 is 15 pounds on the square inch, or 30 inches of mercury. 
 When evaporation occurs in a closed boiler, the space unoccu- 
 pied by water is speedily filled with steam mixed with the air 
 already present. To the pressure of the air the tension of the 
 steam is now added, and consequently the water cannot boil at 
 212 Fahr. If the mixed air and steam are allowed to escape 
 until the former has been entirely expelled, and the outlet valve 
 is then closed and the temperature kept constant, in a short 
 time as much steam will be formed as is possible at that tem- 
 perature, and no further evaporation can take place. The 
 steam has reached its maximum density and tension, and is 
 termed saturated. Steam of higher pressure cannot exist at 
 that temperature. A rise of temperature causes fresh evapora- 
 tion, but this only continues until the steam attains the maxi- 
 mum pressure corresponding to the new temperature, hence the 
 unit of volume of saturated steam weighs more than at a lower 
 temperature, and therefore its density must be greater. Density 
 and pressure of saturation (tension) stand in a fixed and invari- 
 able relation to each other, dependent upon temperature, and 
 this forms the principal difference between steam and the so- 
 called permanent gases. The latter follow Mariotte's law, and 
 independently of temperature may be reduced to all degrees of 
 density and pressure which are attainable by ordinary means. 
 So long as water is present, steam in an inclosed vessel will 
 remain saturated at all temperatures, but if heated when in- 
 closed in a vessel by itself, the tension will rise in the same way 
 as with gas; at the same time, however, the steam ceases to be 
 saturated, and assumes the condition known as superheated. 
 In this condition, of course, neither volume nor density can be 
 changed. If saturated steam be allowed to expand at constant 
 temperature, it ceases to be saturated, and decreases in tension 
 and density, and behaves like superheated steam. 
 
 All steam may be considered as superheated which possesses 
 a higher temperature at an equal density, or a lower density at 
 an equal temperature, than saturated steam. 
 
 Steam which is greatly superheated approaches in its beha- 
 vior a perfect gas, but if only slightly superheated, it is subject 
 to special laws which lie between the two extremes of saturated 
 steam and perfect gas.
 
 HEAT AND WORK. 47 
 
 Slight superheating frequently occurs without additional 
 extraneous heat, for instance by throttling it in its passage. 
 Should the steam in a pipe suddenly encounter an obstacle in 
 the form of a reduction of section, an increase of speed at once 
 takes place in the flow of steam; but, as this increase necessarily 
 involves a lessening of the pressure, the steam behind the con- 
 traction is superheated, that is to say, its temperature is 
 higher than the existing pressure warrants. 
 
 Steam. 
 
 Steam, like air, is an elastic, invisible fluid, into which 
 water is converted by heat. It is a great mistake to imagine 
 that the cloudy vapor that is seen issuing like white smoke 
 from steamboats or locomotives is steam: the moment it be- 
 comes thus white and cloudy it ceases to be steam. 
 
 These misty particles are particles of water, and not steam. 
 If a glass vessel is filled with pure steam, the steam will be as 
 invisible as is the atmosphere. Steam is a gas made from water 
 by the application of heat. 
 
 Steam may exist in different states of density; the pressure or 
 elasticity is in proportion to the density. 
 
 It is well known that about 5.55 times the quantity of heat is 
 necessary to convert a given quantity of water, at a temperature 
 of 212 degrees, into steam, as is required to raise the same 
 quantity of water from 32 to 212 degrees (Fahrenheit), and it 
 further has been ascertained that steam, when produced under 
 the pressure of the atmosphere (or 15 pounds per square inch), 
 expands to nearly 1700 times the volume of the water which 
 was evaporated, and that, during the process of evaporation, the 
 temperatures of both water and steam continue at the same point 
 as that of the water when ebullition commenced, which, under 
 the pressure of 15 pounds per square inch, was 212 degrees Fahr. 
 
 The same law obtains at every degree of pressure under 
 which steam might be formed, that is, until the whole of the 
 water subjected to the experiment is evaporated; and however 
 ardent the heat applied may be, the water and steam main- 
 tain the same temperature at which ebullition commenced. 
 
 This temperature varies with the pressure; and the volume is 
 in the inverse ratio of the pressure nearly.
 
 48 THE STEAM-ENGINE AND THE INDICATOR. 
 
 The quantities of heat required to convert equal quantities of 
 water into steam are theoretically the same under every pres- 
 sure; but it must be observed that low pressure steam, when 
 passing off rapidly from the vessel in which it is formed, con- 
 tains many particles of water in mechanical combination with 
 it. On the other hand, under high pressure, the water is thor- 
 oughly evaporated; hence the ratio of volume to pressure, and 
 to the consumption of fuel, is augmented. The volume is also 
 further increased under these circumstances, in consequence of 
 the higher temperature. Water is familiar to us in three con- 
 ditions, namely, 
 
 First As a Solid. 
 
 Second As a Liquid. 
 
 Third As a Gas. 
 
 ist. It requires 140 degrees of heat to convert a pound of ice 
 at 32 degrees into a pound of water at 32 degrees, with a de- 
 crease of volume of about one-ninth Q). 
 
 2d. It requires 180 degrees of heat to raise water at 32 degrees 
 to the boiling point (212 degrees under a pressure of 15 pounds 
 per square inch), with an expansion of 0.0433. 
 
 3d. It requires about 1000 degrees of heat to convert a given 
 quantity of water into steam at 212 degrees, with an increase 
 of volume of 1700 under a pressure of 15 pounds per square inch. 
 
 The temperatures at which fluids boil depend on the pressure. 
 
 The volume of steam produced depends on the pressure and 
 temperature. 
 
 The elasticity varies with the temperature. An increase of 
 pressure augments the temperature, and vice versa. The den- 
 sity of steam, considered as a gas, varies inversely with the 
 temperature under like pressures; and is directly as the pres- 
 sure under like conditions of temperature. 
 
 It is inversely as the volume. 
 
 The specific gravity of steam under the pressure of the atmos- 
 phere is equal to 625, that of air being equal to 1000. 
 
 The weight of a cubic foot of air at 60 degrees is 535.68 
 grains. The weight of a cubic foot of steam at 212 degrees is 
 254.3 grains. The weight of a cubic foot of water at 60 degrees 
 is 62.5 pounds.
 
 333 
 
 HEAT AND WORK. 49 
 
 Atmospheric Pressure. 
 
 The pressure of the atmosphere varies a little at different 
 times in the same localities, and the variation is not the same 
 in one locality as compared with another, but the pressure is 
 generally taken at 14^ pounds per square inch, as the average 
 pressure at the sea level; and is most commonly reckoned at 
 15 pounds in mechanical calculations, in order to avoid the frac- 
 tion T V. 
 
 At i4 T V pounds per square inch the atmosphere will balance 
 a column of mercury (quicksilver) of about 30 inches in height. 
 If a vacuum gage (either a spring gage or a column of mercury 
 like a barometer), attached to the condenser of a steam-engine 
 should indicate 14^5 pounds, the condenser would be void or 
 empty, that is, no steam or air would be in it But should 
 there be air or vapor in the condenser, the gage will show the 
 pressure of the same by a fall in the mercury's height, or a fall- 
 ing back of the index of the gage. Thus, should the mercury 
 stand at 29, 28, or 27 inches, or at 13^, i2rV or iiiV pounds by 
 the spring gage, then there would be a back pressure of i, 2, 
 or 3 pounds per square inch in the condenser. 
 
 All pressures are measured from zero, or nothing, or from a 
 vacuum, which word signifies void, or containing nothing. 
 
 Vapors. 
 
 A vapor is a gas at a temperature near to that at which con- 
 densation occurs. % A11 bodies assume the gaseous condition at 
 suitable temperatures. In an intensely heated furnace even 
 carbon has been made to appear as a gas, although only in a 
 small quantity. Most solids- liquefy before becoming gaseous; 
 but some appear to become gases at once when subjected to in- 
 tense heat. 
 
 According to Professor James Thomson, this always occurs 
 when the boiling point of the substance at the given pressure is 
 lower than the freezing point for the same pressure. 
 
 Vapors are formed more readily in vacuo than in the air; but, 
 for any given temperature, the quantity of vapor which will form 
 in a space from an exposed liquid is the same, whether air or 
 other gases be present or not, the vapor being formed almost 
 instantaneously in the second case, and requiring more or less 
 time for formation in the first. 
 4
 
 50 THE STEAM-ENGINE AND THE INDICATOR. 
 
 The pressure which this vapor eventually adds to the pressure 
 of gases already existing in the space, depends on the tempera- 
 ture only, and is the same, no matter what may have been the 
 previously existing pressure. When no more liquid will change 
 into vapor, we may say that the space is saturated. 
 
 Unsaturated vapors follow approximately the laws of gases in 
 expanding with heat. Steam, when passing along hot pipes to 
 the engine, may be superheated; and its co-efficient of expan- 
 sion will be found to differ very little from that of common air. 
 By superheating steam we increase its volume, whilst its pres- 
 sure, within certain limits, is unchanged. We also render it 
 less liable to condense in the cylinder; and we convert into 
 steam many particles of water which are often carried over 
 from the foam in the boiler when the steam is not superheated. 
 
 Steam or Aqueous Vapor. 
 
 Water evaporates at all temperatures, and even ice, when 
 exposed to the air, loses weight on this account. The evapora- 
 tion of water takes place only on the surface in contact with air. 
 
 When the temperature of the water is elevated to or above 
 that of the boiling point, then evaporation takes place in any 
 part of the water where the temperature is elevated. 
 
 The weight of water evaporated in a given time is dependent 
 on the following circumstances : 
 
 First. The area of the surface of exposed water. 
 
 Second. The temperature to which it is subjected. 
 
 Third. The movement of the atmosphere. When in a state 
 of tranquillity, the air immediately above the water which is 
 evaporating becomes saturated, and evaporation can then only 
 continue as vapor, already set free, escapes by diffusion. When, 
 on the contrary, the air is agitated, the damp strata are contin- 
 ually borne away and replaced by drier ones, and thus the pro- 
 cess of evaporation is facilitated. 
 
 Fourth. The relative humidity of the atmosphere. The fur- 
 ther the air is from its point of saturation, the more rapidly 
 does evaporation take place. 
 
 Fifth. The pressure of the atmosphere. The less the pres- 
 sure, the swifter the evaporation. 
 
 Sixth. By reason of adhesion to any moist body with which 
 the water may be in contact.
 
 HEAT AND WORK. 51 
 
 The temperature of the boiling point 'depends upon the pres- 
 sure on the surface of the water. 
 
 P=pressure in pounds per square inch above vacuum on the surface of 
 
 the water. 
 T =temperature Fahrenheit of the boiling point. 
 
 T=200i/P 101 ................... I 
 
 Example i. At what temperature will water boil under a 
 pressure of P=8 pounds to the square inch ? 
 
 This is under a vacuum of 14.7 8=6.7 pounds to the square 
 inch. 
 
 6 _ 
 
 Temperature, T = 2OO]/ 8 101 = 181.8 
 
 Example 2. What pressure is required to elevate the tempera- 
 ture of the boiling point of water to T = 330 ? 
 
 f33o-(-ioi i $ 
 Pressure P= 2QQ - = 100 pounds. 
 
 The temperature of the boiling point is the same as that of the 
 steam evaporated under the same pressure. 
 
 Supposing the above formulas to be correct, the ideal zero of 
 aqueous vapor should be at 101 degrees Fahr. , or at the tem- 
 perature 101 degrees below Fahr. zero, there is no pressure of 
 the vapor; that is, the force of attraction between the atoms is 
 equal to the force of expansion by heat. 
 
 Latent Heat of Steam. 
 
 One pound of water heated, under atmospheric pressure, from 
 32 to 212, requires 180.9 units of heat. If more heat is sup- 
 plied, steam will be generated without elevating the tempera- 
 ture until all the water is evaporated, which requires 1146.6 
 units of heat, and the steam volume will be 1740 times that oc- 
 cupied by the water at 32. 
 
 Then, 1146.6 180.9=965.7 units of heat will be absorbed 
 in the steam, the temperature of the latter not being raised. This 
 is what is called latent heat, because it does not show as tem- 
 perature, but is the heat consumed in performing the work of 
 converting the water into steam.
 
 52 THE STEAM-ENGINE AND THE INDICATOR. 
 
 One cubic foot of water at 32 weighs 62.387 pounds; if 
 heated to the boiling point, 212, there will be required: 
 62.387 X iSo.9=ii285.8 units of heat, 
 
 and if evaporated to steam under atmospheric pressure, there 
 will be required: 
 
 62.387 X 1146.6=71532.9 units of heat, 
 
 of which 
 
 71532.911285.8=60247.1 will be latent, 
 
 It is this latent heat which generated 1740 cubic feet of steam 
 from the cubic foot of water. 
 
 The work accomplished by these latent units of heat against 
 the atmospheric pressure will be : 
 
 K=i44Xi4-7X(i74o+i)=368ni5 foot pounds. 
 Foot pounds per unit of heat, Joule^^Q =61.1. 
 
 The heat expended in elevating the temperature of the water 
 from 32 to 212 is not realized as work. 
 
 Volume of Water. 
 
 Water, like other liquids, expands in heating and contracts 
 in cooling, with the exception that in heating it from 32 to 
 40 it contracts, and expands in heating from 40 upwards. 
 The greatest density or smallest volume of water is therefore at 
 40 Fahr. 
 
 Latent and Total Heat in Water from 32 Degrees. 
 
 When water expands it absorbs heat, which is not indicated 
 as temperature, but remains latent. 
 
 The latent heat in water heated from 32 to 40 is negative, 
 that is, the water indicates more temperature than units of heat 
 imparted to it. The volume at 32 is 1.000156, and the heat 
 units required to raise the temperature of one pound of water 
 from 32 to 40 or 8 are: 
 
 0.999844X8=7.99875 units. 
 
 The heat units required to raise the temperature of one pound 
 of water from 32 to 212 or 180 are 181 units. The heat 
 units required to raise water from 32 to 350 or 318 are 322 
 units, or 4 units more than the increase of temperature.
 
 HEAT AND WORK. 53 
 
 Temperature of Boiling Liquid. 
 
 While the temperature of saturated steam always corresponds, 
 when protected against cooling, to the pressure, that of the 
 liquid from which the steam is formed may vary within a few 
 degrees; for, when the latter begins to boil, the lower layers 
 which lie immediately above the heated bottom are hotter than 
 the upper. The steam bubbles which form at the bottom of the 
 vessel condense as they rise with noise (illustrated by the so- 
 called singing of the water that takes place in the common tea- 
 kettle), and only reach the surface when the temperature 
 throughout becomes more uniform. 
 
 For the formation of such bubbles in a liquid, it is necessary 
 that the cohesion of the particles among themselves, and their 
 adhesion to the sides of the vessel, be overcome. 
 
 Condensation of Steam. 
 
 Steam is condensed either by cooling or compression, passing 
 during the process of condensation from the unsaturated to the 
 saturated, and finally into the liquid state. As a very large 
 amount of heat is set free by condensation, steam is, for many 
 purposes, a very convenient vehicle for the conveyance of heat. 
 
 "Wet and Dry Steam. 
 
 Steam which is formed rapidly carries with it from the boiier 
 fine drops of water, and is called "wet steam;" to distinguish it 
 from "dry steam," which is unmixed with liquid. The em- 
 ployment of wet steam causes a great loss, as the heat contained 
 in the water is not available in either the steam-engine or the 
 heating apparatus, while the water itself collected in the steam 
 pipe is apt to give trouble in the cylinder. Therefore, the best 
 steam boilers are those provided with a steam dryer. Steam is 
 especially moist when the evaporation follows decrease of pres- 
 sure. 
 
 Throttling of Steam. 
 
 When steam is reduced in pressure by passing it through a 
 contracted passage, as in a stop-valve partly closed, the speed 
 of the steam in passing through will increase correspondingly. 
 As soon as the narrow part is passed, however, the normal speed 
 is resumed, and the force acquired by the steam escapes as heat
 
 54 THE STEAM-ENGINE AND THE INDICATOR. 
 
 Any water it may have originally conveyed is, by the increase 
 of heat, converted into steam, and thus the steam is drier than 
 before the throttling. 
 
 Low and High Pressure Steam. 
 
 Steam, or the vapor of water, when produced at the usual 
 pressure of the atmosphere and 15 pounds above, is commonly 
 called low pressure; and that which exceeds 15 pounds per 
 square inch is termed high pressure. 
 
 The early steam engines used steam at the atmospheric pres- 
 sure, or a few pounds per square inch above the atmosphere, 
 and were fitted with a condenser, and by condensing the ex- 
 haust steam gained the additional pressure due to the atmos- 
 phere; and were usually called low pressure engines, instead of 
 condensing engines, their proper name. 
 
 In the present advanced state of the art, high pressure steam 
 is now most generally used for supplying condensing engines. 
 
 The proper terms for engines at the present time are condens- 
 ing, compound condensing, non-condensing and non-condensing 
 compound engines, respectively. 
 
 Absolute Pressure. 
 
 It is customary to express the elastic force of steam in three 
 ways: 
 
 First. In pounds of pressure that it exerts on the square inch. 
 
 Second. The height of the column of mercury which it sus- 
 tains. 
 
 Third. In atmospheres. As the actual pressure of the atmo- 
 sphere is continually varying, engineers have decided to employ 
 29.922 inches of mercury, which is equal to a pressure on a 
 square inch of 14.696 pounds, nearly, but in practice 14.7 
 pounds is used. 
 
 Water evaporated in the open air is said, according to this 
 notation, to be transformed into steam of zero pressure, instead 
 of steam of 14.7 pounds pressure per square inch, which pres- 
 sure counter-balances that of the atmosphere. If such steam is 
 used in a condensing engine, the effect is said to be due to 
 vacuum, which is still regarded by some people as a separate 
 force unconnected with steam, and in fact operating on the
 
 HEAT AND WORK. 55 
 
 opposite side of the piston. When steam of higher pressure is 
 used, it is customary, in finding the horse-power, to add the 
 vacuum to the steam pressure, thus carrying out the same idea. 
 
 The absolute pressure of steam is measured from zero or 
 perfect vacuum, and consists of the pressure as shown by the 
 steam-gage (which only shows the pressure above atmospheric 
 pressure), and as before stated, the pressure of the atmosphere 
 is indicated by the barometer. The latter may, for all practical 
 purposes, be taken at 15 pounds, corresponding to 30.6 inches 
 of mercury. The vacuum gages in general use are usually 
 graduated to agree with the scale of the barometer, and the 
 vacuum is usually stated in inches of mercury. To the steam 
 pressure shown by gage, add 15 pounds for total pressure. 
 Thus, if the pressure gage indicates 75 pounds, the total or 
 absolute pressure is 90 pounds per square inch. When the 
 piston moves forward in an engine, the total pressure on steam 
 side at any point in the stroke of piston is, the pressure above 
 the atmosphere plus 15 pounds, and the total pressure for whole 
 stroke is the mean pressure above the atmosphere plus 15 
 pounds. Thus, if the mean pressure for the whole stroke is 25 
 pounds as per gage, the total mean pressure is 15 -f- 25 = 40 
 pounds; and this 40 pounds, whether the engine is operated as 
 a condensing or non-condensing engine, is the variable factor 
 in estimating the load on the engine. 
 
 Now if the engine be operated as a non-condensing one, 
 the 15 pounds (pressure of atmosphere) on steam side is bal- 
 anced by a like pressure of atmosphere on exhaust side of piston, 
 and its effect is annihilated or reduced to nothing. But, if the 
 engine be operated as a condensing one, a large proportion of 
 the pressure of atmosphere on the steam side of the piston is 
 made to do useful work. With well-proportioned condensing 
 apparatus, the pressure of the atmosphere on the exhaust side of 
 the piston can be reduced nearly ninety per cent. in other 
 words, a vacuum in the exhaust end of the cylinder of 26.5 
 inches (13 pounds) may be maintained, and this 26.5 inches or 
 13 pounds per square inch of area of the piston is an absolute 
 gain, and should in all cases be utilized. 
 
 Absolute or total pressure means the steam pressure in pounds 
 per square inch, including the pressure of the atmosphere, and
 
 56 THE STEAM-ENGINE AND THE INDICATOR. 
 
 is generally denoted by P; and p is used to denote the steam 
 pressure above atmosphere, as is shown on the ordinary steam 
 gage. If a mercury column is used, it is shown in inches and 
 fractions of an inch. The specific gravity of mercury at 32 
 Fahr. is 13.5959, compared with water of maximum density at 
 39. One cubic inch of mercury weighs 0.491 of a pound; and 
 a column of 29.922 inches is equivatent in weight to that of the 
 atmosphere or 14.7 pounds per square inch, very nearly. 
 
 Latent Heat and the Heat of Chemical Combination. 
 
 If we warm a pound of ice, having a temperature of 32 de- 
 grees Fahr. , we find that when all the ice is melted the water 
 exhibits no augmentation of temperature, the thermometer still 
 standing at 32 degrees, although heat enough has been added to 
 have heated one pound of water, at 32 degrees, to 143 degrees 
 Fahrenheit. If, again, we continue to heat the resulting water, 
 the temperature rises until the thermometer stands at 212 de- 
 grees, when the water begins to boil. The thermometer now 
 remains stationary, and the water gives off steam, at the same 
 temperature, until it is all boiled away; and to convert the 
 pound of water, at 21 2 degrees, into a pound of steam at the 
 same temperature, 966.6 times as much heat is required as is 
 needed to raise one pound of water one degree of Fahrenheit. 
 Hence the latent heat of water is said to be 143 degrees; that of 
 steam 966.6 degrees Fahrenheit; so designated by those who 
 first observed the phenomenon, because the heat thus employed 
 to melt the ice, or evaporate the water, was hidden and not 
 sensible to the thermometer. The mechanical theory of heat, 
 however, explains what has become of this hidden heat. It de- 
 clares that the heat thus expended is consumed in doing internal 
 work. It separates the particles of the ice to form water, or of 
 the water to form steam, and it is given off whenever the water 
 is frozen or the steam condensed. The quantity of heat which 
 is evolved in these changes of state is but very small compared 
 to that set free when the constituent elements of the water 
 undergo combination. 
 
 Units. 
 
 The exact determination of the equivalent values of the units 
 is very difficult, and has been the subject of much scientific in-
 
 HEAT AND STEAM. 57 
 
 vestigation. When a quantity can be measured directly, the 
 unit is generally of the same quality as the thing to be meas- 
 ured; thus, the unit of time is time, as a day or second; the unit 
 of length is length, as one inch, foot; the unit of volume is 
 volume, as one cubic foot; the unit of money is money; of 
 weight is weight; of momentum is momentum. The unit of 
 work or power is one pound raised one foot high, or one pound 
 of force acting through one foot of distance, and is called the 
 foot-pound, and is taken as our standard unit of work done. 
 
 33,000 foot-pounds, or units of work, performed in one min- 
 ute, or 550 pounds in one second, represent one horse-power. 
 
 The unit of elasticity, by which the expansive force exerted 
 by elastic fluids is measured, is, for popular use, one pound on 
 one square inch. 
 
 The scientific unit of elasticity is one atmosphere. 
 
 One atmosphere is equal to 29.9218004 inches of mercury. 
 
 One atmosphere is equal to 406.814704 inches of water. 
 
 One atmosphere is equal to 14.696303 pounds on the square 
 inch. 
 
 One pound on the square inch is equal to 27.68143 inches of 
 water. 
 
 One pound on the square inch is equal to 2.03601 inches of 
 mercury. 
 
 The unit of temperature is the degree Fahrenheit, or T H part 
 of the distance on the thermometric scale between the freezing 
 and the boiling points of water, under the pressure of one 
 atmosphere. 
 
 The unit of heat is the quantity of heat necessary to be added 
 to one pound of water, at or near to its freezing point, to raise 
 its temperature one degree Fahrenheit. Water at 32 Fahren- 
 heit is the unit, or standard, of comparison employed for all 
 measurement of the capacities for heat of all substances what- 
 ever. If the specific heat of water were constant, then the unit 
 of heat would be merely the quantity of heat required to raise 
 the temperature of one pound of water one degree, which would 
 be the same throughout the entire thermometric scale; but 
 since the specific heat of water is not constant, the unit must 
 be the quantity so required at the temperature at which the 
 specific heat of water is one, and that is 32. It is immaterial
 
 58 THE STEAM-ENGINE AND THE INDICATOR. 
 
 what the volume of a pound of water may be, as the density of 
 water has no relevancy to this branch of the subject. 
 
 One unit of heat is equivalent to 772 units of work. This is 
 known as the mechanical equivalent of heat, or in honor of the 
 physicist by whose investigations this relation has been estab- 
 lished, is known as "Joule's equivalent." 
 
 The specific heat of a body is the quantity of heat necessary 
 to be imparted to it in order to raise its temperature one degree, 
 as compared to the quantity that is required to raise by one 
 degree the temperature of an equal weight of water at or about 
 the temperature of 32 degrees. The specific heat of water is 
 greater than that of any other substance, so that this being 
 taken as one, that of any other substance is expressed in 
 decimals. 
 
 The specific heat of superheated steam was investigated by 
 M. Reynault, who ascertained it to be 0.48051. 
 
 The unit of specific gravity is the weight of water. The 
 specific gravity of a body is its weight at the temperature of 
 32 degrees Fahrenheit, compared with that of an equal volume 
 of water. 
 
 The volume of water being i 
 
 That of the same weight of air at 32 is 773.283. 
 
 And that of the same weight of mercury at 32, 0.0735514. 
 
 The volume of one pound of water is 27.68143 cubic inches, 
 or 0.01602 of a cubic foot. 
 
 The weight of a cubic foot of water is 62.4245 pounds. 
 
 The weight of a cubic foot of air is 0.080727 of a pound. 
 
 The weight of a cubic inch of water is 0.036126 of a pound. 
 
 The weight of a cubic inch of mercury is 0.49116 of a pound. 
 
 Expansion. 
 
 The rate of expansion of water by heat varies more than that 
 of any other substance. Between 39.1 and 212 its volume 
 increases from i to 1.04332, and its expansion for each one 
 degree added to its temperature, increases from o at 40 to 
 0.00044 at 212. Above the latter point nothing is known 
 about it.
 
 CHAPTER IV. 
 
 EXPANSION. 
 
 WHEN a volume of air is compressed into a smaller volume, a 
 certain amount of power is expended in compressing it, which 
 power, as in the case of a bent spring, is given back when the 
 pressure is withdrawn. If, however, compressed air is suddenly 
 released into the atmosphere, the power expended in compress- 
 ing it is lost. But the work existing in such compressed air 
 can be readily utilized in propelling a piston by its expansion. 
 Now, the steam used to propel engines is in the condition of 
 air already compressed, and to save the power which would be 
 lost if the steam were suddenly released into the atmosphere, it 
 must be used expansively, and to use it expansively with regard 
 to economy, it must be cut off, that is, the steam-port must be 
 closed before the piston has completed its stroke. If the flow 
 of steam to an engine be cut off when the piston has performed 
 one-half stroke, leaving the stroke to be completed by the ex- 
 panding steam, it has been found by experiment that the effi- 
 cacy of a given quantity of steam will be increased 1.7 times 
 beyond what it would have been if the steam at half-stroke had 
 been released into the atmosphere, instead of allowing it to 
 expand in the cylinder. If cut off at one- third of the stroke, 
 the efficiency will be increased 2.1 times; at one-fourth stroke, 
 2.4 times; at one-fifth, 2.6 times; at one-sixth, 2.8 times; at 
 one-seventh, 3 times; and at one-eighth, 3.2 times. 
 
 Expansion of Steam. 
 
 The law of the expansion of steam is established with hardly 
 less certainty than that the attractive force of gravity is in- 
 versely as the square of the distance. Whatever pressure may 
 be exerted upon the piston of a steam engine, while the com- 
 munication between the boiler and the cylinder is open, it is 
 absolutely certain that unless the steam be immediately con- 
 densed or discharged into the air, pressure will be exerted after 
 
 (59)
 
 6O THE STEAM-ENGINE AND THE INDICATOR. 
 
 the communication with the boiler has been closed. If the 
 piston be free to move along the cylinder, a gradually diminish- 
 ing pressure, corresponding to the increased volume to which the 
 steam is thus expanded, will be exerted. All the force thus 
 obtained while the piston is in motion, and after the closing of 
 the valve, is so much gain over and above the effect due to the 
 same amount of steam when employed in the manner known as 
 "full stroke," inasmuch as none of this additional pressure 
 would have been exerted had the stroke of the piston termi- 
 nated at the point at which the steam was cut off. From this 
 gain, however, whatever it may be, is to be deducted the friction 
 of the engine while running with expanded steam, and as the 
 steam loses a considerable pact of its temperature during expan- 
 sion, there is a further loss also from the fact that the cylinder is 
 cooled, and it thus condenses a certain amount of steam on the 
 next stroke, before its temperature is restored. These losses 
 may be measured, however, and they should never, as they sel- 
 dom do, exceed the gain realized from expansion. To secure 
 the highest gain from expansion, the engine must be fitted with 
 a condenser. 
 
 To simplify the action of expanding steam let us take an up- 
 right cylinder one inch in diameter and at least 1,700 inches in 
 height, pour into it one cubic inch of water, fit into it a steam 
 tight piston, resting on the water, so counterbalanced as to be 
 weightless, and so arranged as to work without friction, and 
 then place a lamp under the cylinder; we then notice that so 
 soon as the water reaches the temperature of 212 degrees, it 
 will begin to boil and produce steam, and the steam will begin 
 to push up the piston. So long as the lamp continues to burn 
 and the water continues to boil, so long will the steam continue 
 to push up the piston, until all of the water has been evaporated 
 into steam. When all of the water has so evaporated, it will 
 be found that from one cubic inch of water there has been pro- 
 duced 1,700 cubic inches of steam, and as this would fill 1,700 
 cubic inches of the cylinder, and as the pressure of the atmo- 
 sphere the only resistance in this case to be overcome is 15 
 pounds (14. 7 exact) to the square inch, this experiment would 
 show that one cubic inch of water wholly evaporated into 
 steam, will push or lift, say 15 pounds 1,700 inches, or 142 feet.
 
 EXPANSION. 6l 
 
 If, now, the experiment be carried a little further with a similar 
 cylinder and piston, and 15 pounds be loaded on the piston, 
 making with atmospheric pressure 30 pounds, we shall find 
 that under this additional pressure the temperature of the water 
 must be raised to 252 degrees, instead of 212 degrees, before it 
 begins to boil, and before the steam begins to push up the 
 piston, and that when the whole of the water is evaporated, 
 there will be only 850 instead of 1,700 cubic inches of steam, 
 and the piston will be pushed or lifted up only 850 instead of 
 1,700 inches, or in round numbers, 71 feet. If, then, one 
 cubic inch of water wholly evaporated, will produce steam 
 enough to push or lift 15 pounds 142 feet, and 30 pounds 71 
 feet, it would produce steam enough to push or lift 142 times 
 15 pounds, or 
 
 142 x 15 = 2,130 pounds- 
 say one ton one foot. When, then, the steam from one cubic 
 inch of water has pushed or lifted one ton one foot, it has done 
 all it can do, and, if the experiment is to be repeated, this spent 
 steam must be released by means of a valve, called the exhaust 
 valve, and more steam admitted or generated to push or lift up 
 the piston. The machinery used in this experiment represents 
 simply a full-stroke or non-expansion engine, making one 
 stroke, and for each stroke made by such an engine, the utmost 
 possible power to be obtained is equivalent to one ton lifted one 
 foot for every cubic inch of water evaporated, no more, no less. 
 This is all the power we can get out of a steam engine without 
 a cut-off. 
 
 But let us experiment a little further. Suppose we load the 
 piston with one ton of bricks, and suppose, instead of opening 
 the exhaust valve, we remove one of the bricks, the load being 
 thus to this extent diminished, the steam, no longer compressed 
 by the whole ton, will expand a little and push or lift up the 
 rest of the bricks a little further, and as brick after brick is 
 removed, the steam will push or lift up the rest of the bricks 
 further and further, until the last brick having been removed, it 
 will be found that the steam has pushed or lifted up the piston 
 to the full height of. 1,700 inches, or 142 feet. Now, it will be 
 seen from this experiment, that all the power which was exerted 
 by the steam, as the bricks were successively removed, was a
 
 62 THE STEAM-ENGINE AND THE INDICATOR. 
 
 clear gain, as it cost no fuel or steam other than that which had 
 already pushed or lifted the one ton one foot, and it could do 
 no more, unless and until the steam was relieved of a part or 
 the whole of the resisting weight or pressure. This principle, 
 the law of expanding steam, was discovered by James Watt. 
 
 The Most Economical Point of Cut-off. 
 
 The higher the grade or ratio of expansion the greater is 
 the economy; but the result is somewhat modified by other 
 considerations. 
 
 First. The higher the rate of expansion the lower is the 
 mean or average pressure throughout the stroke, and a low 
 mean pressure involves the use of a large engine for a given 
 power. 
 
 Second. With a high rate of expansion the mean pressure is 
 much lower than the initial pressure, and although the power 
 of the engine is only due to the mean pressure, the strength of 
 the engine must be sufficient to withstand the initial pressure. 
 
 Third. A very high rate of expansion also leads to a very low 
 final pressure, and as to drive the engine itself against its own 
 friction only, and to expel the steam from the cylinder, seldom 
 requires less than three pounds above the external pressure, it 
 follows that if the steam is so far expanded that the terminal 
 pressure falls below this, the expansion is excessive, and the 
 reverse of advantageous. 
 
 In non-condensing engines the lowest final pressure is deter- 
 mined by the pressure of the atmosphere, say 15 pounds per 
 square inch, and 18 pounds may be taken as the lowest pressure 
 to which steam can be expanded with advantage. If the ex- 
 haust passages are small or the exhaust steam damp, a higher 
 final pressure will be more economical. In condensing engines 
 the temperature of the condenser is generally about 100 degrees 
 Fahr., and the pressure corresponding to this is about one 
 pound per square inch, but the presence of air in the condenser 
 generally prevents the pressure there falling below two pounds 
 per square inch. From four to five pounds may be taken as 
 the lowest advantageous final pressure. 
 
 Fourth. The highest advantageous rates of expansion, even 
 with jacketed cylinders, appear in practice to be between twelve
 
 EXPANSION. 63 
 
 and sixteen times. Higher rates are and should be aimed at, 
 but with our present arrangement of engine, it is doubtful 
 whether the increased economy of very high ratio or grades, 
 pays for the increased complications and the extra cost of the 
 apparatus required to attain it. In unjacketed cylinders the 
 limit of advantageous expansion is much under the lowest of 
 the grades named. 
 
 In practice the best result of steam engines does not convert 
 more than ten per cent, of the heat used by it into work, and 
 this too in engines of considerable size, and with boilers and 
 furnaces fairly efficient. In small engines it is much less; in- 
 deed, it is certain that few among the thousands of steam 
 engines in daily use below five horse-power, give an efficiency 
 greater than Jive per cent. The great cause of loss is the 
 amount of heat necessary to change the water from the liquid to 
 the gaseous state, most of this being expelled with the exhaust 
 either into the condenser or the atmosphere. Many attempts 
 have been made to use liquids of lower specific heat than water, 
 and requiring less heat for evaporation, the principal being 
 plcohol, ether and carbon bisulphide; but for obvious reasons 
 no success has been attained. 
 
 Action and "Work of Expanding Steam. 
 
 When steam is supplied to move a piston alternately in a 
 cylinder, and the valve for admission of steam is open during 
 the full stroke of the piston, the cylinder is filled with steam at 
 every stroke, of a pressure nearly equal to that of the boiler, 
 and is exhausted at nearly the same density. The following 
 diagram, Fig. 4, was taken under such circumstances. 
 
 In order to save steam, or more correctly to employ its effects 
 to a higher degree, the admittance of steam to the cylinder is 
 cut off when the piston has moved a portion of its stroke. 
 From the cut-off the steam acts expansively with a decreased 
 pressure on the piston, as shown in the following diagram, 
 
 Fig- 5- 
 
 If we admit steam of 85 pounds boiler pressure, to which we 
 add 15 pounds, the atmospheric pressure, the total pressure per 
 square inch in the cylinder will be as follows: 
 
 85 + 15 = ioo pounds per square inch.
 
 64 THE STEAM-ENGINE AND THE INDICATOR. 
 
 Now if we cut off the steam when the piston has traveled half 
 the length of the stroke, from k to e, the steam remaining in 
 the cylinder will expand to double its volume in forcing the 
 
 FIG. 4. 
 
 piston to the end of the cylinder, and a certain amount of work 
 has been done with half the quantity of steam, as illustrated in 
 the shaded diagram Fig. 5. The steam in expanding after the 
 
 FIG. 5. 
 
 port is closed, during the rest of the stroke continues to do work, 
 as the pressure of the expanding steam is greater in the cylinder 
 than that in the condenser. Now this work performed after 
 the steam was cut off, is greatly in excess of that performed in
 
 EXPANSION. 65 
 
 Fig. 4, as compared to the respective volumes, as 5 is to 10, 
 and has been obtained by the use of expansion. In this latter 
 case the steam expanded twice its volume, and its pressure was 
 exactly half what it was before; namely, 50 pounds per square 
 inch. 
 
 In making this calculation for pressure of steam after it has 
 expanded, the total pressure P, must be used, which is reckoned 
 from perfect vacuum. 
 
 In Fig. 4, VB is the diameter, and A D the length of the 
 stroke; the pressure during the stroke, when there is no expan- 
 sion, is assumed at 85 pounds, as per steam gage, plus 15 pounds 
 for perfect vacuum. 
 
 85 + 15 = loo pounds total pressure per square inch. 
 
 Now, if the steam is cut off when the piston has moved one- 
 half the length of the cylinder, see diagram Fig. 5, from k to <?, 
 the steam, the volume of which is V, B, e and m, must expand 
 and fill the whole cylinder, its pressure getting less and less, so 
 that such lines as , m, /, ^, and g, V, in Fig. 5 and , m, /, 
 <?, j, ^ and^- Fin Fig. 6, represent pressure at different parts of 
 the stroke, and the curve <?, f, /, j, and g, is the expansion curve. 
 
 FIG. 6. 
 
 The above diagram, Fig. 6, represents the same engine cut- 
 ting off at one-quarter the stroke, the average pressure being 
 59.65 pounds mean pressure. 
 
 In fact, Figs. 4, 5 and 6 (heavy shading) are theoretical indi- 
 
 5
 
 66 THE STEAM-ENGINE AND THE INDICATOR. 
 
 cator diagrams, supposed to be taken from a condensing engine. 
 The diagram on the face is the ideal one. The average pressure 
 from a non-condensing engine would be arrived at in the same 
 way, but 15 pounds would be deducted after the calculations 
 were made to allow for pressure of the atmosphere, and hence 
 their areas indicate the relative amounts of work performed in 
 a single stroke of the engine, when there is: 
 
 First. No cut-off. 
 
 Second. Cut-off at half stroke. 
 
 Third. Cut-off at one-fourth of the stroke. 
 
 Now the area of Fig. 5 is nearly equal to that of Fig. 4, so 
 that when expansion is allowed, a cylinder half full of steam 
 will perform more than three-fourths as much work as the 
 cylinder full of steam at the same initial pressure, can perform 
 without expansion. 
 
 As a further illustration, Fig. 6 is the diagram that would be 
 made if the steam were cut off after the piston had traveled one- 
 fourth of the stroke. In this case only one-fourth the steam 
 would be required, as was for Fig. 4, performing more than one- 
 half as much as the latter with one-fourth of the steam. 
 
 Assuming that in the cylinder the volume of steam varies 
 inversely as the pressure, the work done in one stroke of the 
 piston is: 
 
 Or, in words, the work done is the value of the hyperbolic 
 logarithm x, from table 2, page 69, plus one, multiplied by the 
 product of the initial pressure P, multiplied by /, (the distance 
 the piston moves before steam is cut off), and this product by 
 the area A, of the cylinder in square inches. 
 
 Where A = area of cylinder or piston in square inches ; 
 
 L = length of stroke of piston in inches ; 
 
 / = distance traveled by the piston before the steam is cut 
 off; 
 
 g = grade or ratio of expansion j 
 
 x hyperbolic logarithm of g (see table 2) ; 
 
 P = initial pressure of steam in pounds per square inch, 
 measuring from perfect vacuum in cylinder before cut-off takes 
 place ;
 
 EXPANSION. 67 
 
 Then mp = mean average pressure after cut-off takes place and 
 during full stroke, in pounds per square inch, and is found by 
 the following formula: 
 
 Mean Pressure. 
 
 When the steam is expanded in the cylinder, the mean pres- 
 sure (mp} throughout the stroke of the piston, will be less than 
 the initial pressure P. The mean pressure mp during expan- 
 sion, will be according to formula 2; or in words: 
 
 Rule. Divide the initial pressure P by the proportion or 
 grade g of the stroke, during which the steam is admitted, and 
 multiply the quotient by the hyperbolic logarithm x, plus one 
 ( take the value x from table 2). 
 
 Ratio, or Grade of Expansion. 
 
 The proportion or grade g of the stroke during which the 
 steam is admitted, is found by dividing the length L in inches 
 of the cylinder swept through by the piston by the length / in 
 inches of the space into which the steam is admitted. 
 
 Example. Suppose the length of the stroke of the piston is 
 L = 80 inches, the initial pressure P=qo pounds per square 
 inch, and the steam to be cut off at / = 20 inches of the stroke, 
 what will be the mean pressure? 
 
 Formula 2: 
 
 Grade or ratio g = - = 4 grade. 
 
 Hyperbolic logarithm of 4 = 1.386 (see x in table No. 2). 
 Then we have 
 
 m p = &L x ( i + 1.386 )= 53.68 pounds per square inch, 
 
 the mean pressure required. 
 
 The initial pressure P given above is the total pressure, meas- 
 ured from perfect vacuum. To find the initial pressure P, add 
 the atmospheric pressure 15 pounds to the pressure/, as shown 
 by the steam gage, and from the mean pressure (mp) found as
 
 68 
 
 THE STEAM-ENGINE AND THE INDICATOR. 
 
 above, subtract the counter or back pressure from effective 
 mean pressure exerted. Thus, in the above case the steam 
 gage is supposed to show a pressure p of 75 pounds, to which is 
 added 15 pounds for the atmosphere, making 
 
 75 -f- 15 = 90 pounds total pressure. 
 
 Assuming the engine to be condensing, in practice we must 
 deduct for loss from imperfect vacuum not less than four 
 pounds, and for a non-condensing engine the pressure of the 
 atmosphere. Any estimated counter or back pressure above 
 that must be subtracted from the mean pressure obtained by the 
 calculation. 
 
 TABLE NO. i. 
 HYPERBOLIC LOGARITHMS. 
 
 r 
 
 o.ooooo 
 
 2.6 
 
 0.95548 
 
 4.2 
 
 1.43505 
 
 5-8 
 
 1.75785 
 
 I.I 
 
 0.09530 
 
 2.7 
 
 0.99323 
 
 4-3 
 
 L45859 
 
 5-9 
 
 1-77495 
 
 1.2 
 
 0.18213 
 
 2.8 
 
 1.02962 
 
 4.4 
 
 I.48l6l 
 
 6. 
 
 I -79 I 75 
 
 i-3 
 1.4 
 
 0.26234 
 0.33646 
 
 2-9 
 
 3- 
 
 1.06473 
 1.09861 
 
 tl 
 
 1.50408 
 1.52603 
 
 6.1 
 
 6.2 
 
 1.80827 
 1-82545 
 
 1.5 
 
 0.40505 
 
 3-1 
 
 1.13140 
 
 4-7 
 
 1-54753 
 
 6-3 
 
 1.84055 
 
 1.6 
 
 0.46998 
 
 3-2 
 
 1.16314 
 
 4-8 
 
 1.56859 
 
 6.4 
 
 1.85629 
 
 i-7 
 
 0.53063 
 
 3-3 
 
 I-I9594 
 
 4-9 
 
 1.58922 
 
 6-5 
 
 1.87180 
 
 1.8 
 
 0.58776 
 
 3-4 
 
 1.22373 
 
 5- 
 
 1.60944 
 
 6.6 
 
 1.88658 
 
 J -9 
 
 0.64181 
 
 3-5 
 
 1.25276 
 
 5-1 
 
 1.62922 
 
 6-7 
 
 1.90218 
 
 2. 
 
 0.69315 
 
 3-6 
 
 1.28090 
 
 5-2 
 
 1.64865 
 
 6.8 
 
 1.91689 
 
 2.1 
 
 0.74190 
 
 3-7 
 
 1.30834 
 
 5-3 
 
 1.66770 
 
 6-9 
 
 I-93I49 
 
 2.2 
 
 0.78843 
 
 3-8 
 
 1.33046 
 
 5-4 
 
 1-68633 
 
 7- 
 
 I-9459I 
 
 2-3 
 
 0.83287 
 
 3-9 
 
 1.36099 
 
 5-5 
 
 1.70475 
 
 7-i 
 
 1.96006 
 
 2.4 
 
 0.87544 
 
 4- 
 
 1.38629 
 
 5-6 
 
 1.72276 
 
 7-2 
 
 1.97406 
 
 2-5 
 
 0.91629 
 
 4.1 
 
 1.41096 
 
 5-7 
 
 1.74046 
 
 7-3 
 
 1.98787 
 
 7-4 
 
 2.00149 
 
 8.8 
 
 2.17482 
 
 12 
 
 2.48491 
 
 26 
 
 3.25810 
 
 7-5 
 
 2.01490 
 
 8.9 
 
 2.18615 
 
 13 
 
 2.56494 
 
 27 
 
 3-29584 
 
 7.6 
 
 2.02816 
 
 9- 
 
 2.19722 
 
 14 
 
 2.63906 
 
 28 
 
 3-33220 
 
 7-7 
 
 2.04115 
 
 9-1 
 
 2.20837 
 
 15 
 
 2.70805 
 
 29 
 
 3-36730 
 
 7.8 
 
 2.05415 
 
 9-2 
 
 2.21932 
 
 16 
 
 2.77259 
 
 30 
 
 3.40120 
 
 7-9 
 
 2.06690 
 
 9-3 
 
 2.23014 
 
 17 
 
 2-83321 
 
 3i 
 
 3-43399 
 
 8. 
 
 2.07944 
 
 9-4 
 
 2.24085 
 
 18 
 
 2.89037 
 
 32 
 
 3-46574 
 
 8.1 
 
 2.09190 
 
 9-5 
 
 2.25129 
 
 19 
 
 2.94444 
 
 33 
 
 3-49651 
 
 8.2 
 
 .10418 
 
 9-6 
 
 2.26191 
 
 20 
 
 2-99573 
 
 34 
 
 3-52636 
 
 8-3 
 
 .11632 
 
 9-7 
 
 2.27228 
 
 21 
 
 3-04452 
 
 35 
 
 3-55535 
 
 8.4 
 
 .12830 
 
 9-8 
 
 2.28255 
 
 22 
 
 3.09104 
 
 36 
 
 3-58352 
 
 8-5 
 
 .14007 
 
 9-9 
 
 2.29171 
 
 23 
 
 3-13549 
 
 37 
 
 3.61092 
 
 8.6 
 
 .15082 
 
 10 
 
 2.30258 
 
 24 
 
 3- 1 7805 
 
 38 
 
 3-63759 
 
 8-7 
 
 .16338 
 
 ii 
 
 2.39589 
 
 25 
 
 3.21888 
 
 39 
 
 0-66356 
 
 Hyperbolic Logarithms. 
 
 In estimating the power which an engine will exert with a 
 given pressure of steam, to be cut off at any given point of the
 
 EXPANSION. 
 
 69 
 
 stroke, we ascertain the mean pressure on the square inch 
 which will be exerted during the stroke by means of the table 
 of hyperbolic logarithms, which latter are calculated for expan- 
 sion according to the law of Boyle and Mariotte. 
 
 The common logarithm multiplied by 2.30258509 gives the 
 hyperbolic logarithm, and the hyperbolic logarithm multiplied 
 by 0.43429448 gives the common logarithm. 
 
 The above table contains hyperbolic logarithms for num- 
 bers up to 39, which is considered sufficient for application to 
 expansion of steam. 
 
 TABLE NO. 2. 
 
 Portion of Stroke 
 at which 
 Steam is Cut-off. 
 
 Grade or Ratio 
 of 
 Expansion. 
 
 Hyperbolic 
 Logarithm . 
 
 Mean Pressure 
 of Steam 
 during the 
 Whole Stroke. 
 
 Percentage 
 of Gain 
 in Fuel or 
 Power. 
 
 / 
 
 g 
 
 X 
 
 mp 
 
 % 
 
 T V or o.i 
 
 10.0 
 
 2.302 
 
 3-302 
 
 230.0 
 
 | or 0.125 
 
 8.0 
 
 2x79 
 
 3-079 
 
 208.0 
 
 or 0.166 
 
 6.0 
 
 1.791 
 
 2.791 
 
 179.0 
 
 -fo or 0.2 
 
 5-o 
 
 1.609 
 
 2.609 
 
 161.0 
 
 ^ or o. 25 
 
 4.0 
 
 1.386 
 
 2.386 
 
 130.0 
 
 T 5 or 0.3 
 
 3-33 
 
 1.203 
 
 2.203 
 
 I20.O 
 
 or 0.333 
 
 3-o 
 
 1.099 
 
 2.099 
 
 IIO.O 
 
 I or 0.375 
 
 2.66 
 
 0.978 
 
 1.978 
 
 97.8 
 
 J or 0.4 
 
 2-5 
 
 0.916 
 
 1.916 
 
 91.6 
 
 or 0.5 
 
 2.0 
 
 0.693 
 
 1-693 
 
 69-3 
 
 or 0.6 
 
 1.666 
 
 0.507 
 
 1-507 
 
 50.7 
 
 or 0.625 
 
 1.6 
 
 0.470 
 
 1.470 
 
 47.1 
 
 | or 0.666 
 
 5 
 
 0.405 
 
 1.405 
 
 40-5 
 
 lv or 0.7 
 
 .42 
 
 o.35i 
 
 1-351 
 
 35-1 
 
 1 or 0.75 
 
 33 
 
 0.285 
 
 1.285 
 
 22.3 
 
 ^y or 0.8 
 
 25 
 
 0.223 
 
 1.223 
 
 20.5 
 
 | or 0.875 
 
 143 
 
 0.131 
 
 1.131 
 
 I3-I 
 
 & or 0.9 
 
 .11 
 
 0.104 
 
 1.104 
 
 10.4 
 
 The above, Table 2, contains the hyperbolic logarithms for numbers run- 
 ning from 1. 1 1, the grade, or ratio, of T 9 7 , or 0.9 cut-off, up to &, or o.i, repre- 
 senting T \j cut-off, which is considered sufficient for application to expansion 
 of steam for all practical purposes. 
 
 Expansion of Steam and Its Effects with Equal Volumes 
 
 of Steam. 
 
 The theoretical economy of using steam expansively is shown 
 by the foregoing table, the same volume of steam being ex- 
 pended in each case, and expanded to fill the increased spaces.
 
 70 THE STEAM-ENGINE AND THE INDICATOR. 
 
 In Table No. 2, no deductions are made for a reduction of the 
 temperature of the steam while expanding or for loss by back 
 pressure. 
 
 The same relative advantages follow in expansion, as given 
 in the above table, whatever may be the initial pressure of the 
 steam. 
 
 The pressure of the atmosphere is to be included in calculat- 
 ing the expansion. It must, therefore, be deducted from the 
 results in non-condensing engines. In condensing engines a 
 deduction must be made for perfect vacuum. This will amount 
 to about (2^2 pounds per square inch) five inches in well pro- 
 portioned engines. 
 
 Where there is no cut-off, as in diagram Fig. 4, the work 
 done equals A PL, or the area ,A of the cylinder, multiplied 
 by the absolute pressure P, and this product by the length of 
 stroke L of the piston in feet. 
 
 When the cut-off takes place at one-fourth of the stroke Z, at 
 the point e, diagram Fig. 6, there is only one-fourth as much 
 steam admitted as in case of diagram Fig. 4, but the work, in- 
 stead of being 
 
 25, 
 
 4 4 
 
 will be as before stated 
 
 A ^ P ( I + .*), or i X 0.25 X i ( I + 1.386 ) = 59.65 pounds. 
 
 To make this more clear to the general reader, we will as- 
 sume an engine doing actual work. It is well known that the 
 most convenient way of calculating the horse-power of an 
 engine, is to multiply the area of the piston in square inches by 
 the speed of the piston in feet per minute, and divide this pro- 
 duct by 33,000. The result so obtained will be the horse-power 
 of one pound mean effective pressure, and is called the horse- 
 power constant, which, if multiplied by the whole mean effec- 
 tive pressure on the piston during the stroke, will give the 
 indicated horse-power of the engine. 
 
 For example, suppose that the engine that would produce 
 indicator diagrams as represented by Figs. 4, 5 and 6, had a 
 stroke L = 3 feet, making r = 100 revolutions per minute, and a 
 diameter of piston A = no square inches, and a piston speed of
 
 EXPANSION. 71 
 
 100 X 3 X 2 = 600 feet per minute. 
 
 Then the horse-power value of one pound mean effective 
 pressure will be as follows: 
 
 Horse-power constant = = 2 horse-power. 
 
 33,000 
 
 Now diagram Fig. 4 averaged initial pressure P= 100 pounds, 
 or a mean effective pressure throughout the stroke. The horse- 
 power, therefore, will be as follows: 
 
 Horse-power = 100 X 2 = 200 horse-power. 
 
 In diagram Fig. 6, the steam was cut-off after the piston had 
 moved from B to , or one-fourth of its stroke, the grade or 
 ratio of expansion being y = 4. Therefore, the mean effective 
 pressure mp, will be, according to formula (2): 
 
 or substituting values, 
 
 mp = ( I -f 1.386 ) = 59.65 pounds per square inch ; 
 or to simplify it still further, it will be as follows: 
 
 2 = 4 hyp. log. of 4 = 1.386 + i = 2.386 ; 
 then 
 
 == 25 X 2.386 = 59.65 pounds per square inch. 
 
 Now diagram, Fig. 6, shows a mean effective pressure mp 
 = 59.65 pounds per square inch, which multiplied by the horse- 
 power constant will be: 
 
 P= 59.65 X 2 = 119.30 horse-power. 
 
 Therefore, we see that one-fourth of the steam expanded per- 
 forms three-fifths^ or nearly sixty per cent, of the whole work, 
 so that by using expansion the work obtained from one pound 
 of steam is 2.386 times what was obtained when permitting full 
 stroke without expansion, as shown by diagram, Fig. 4, or a 
 gain of forty per cent, by using steam expanding three-fourths 
 of the stroke. 
 
 = 40.5 per cent, of gain.
 
 72 THE STEAM-ENGINE AND THE INDICATOR. 
 
 The number 2.386 has lately been called the "indicator co- 
 efficient" of the engine. By cutting off at one-tenth of the 
 stroke, the efficiency of the steam is increased 3. 3 times, that is, 
 the ' ' indicator co-efficient " is 3. 3. 
 
 Expansion is valuable in another way. At the end of every 
 stroke the piston stops momentarily, returning on its old 
 path, and it is advisable to prepare for the sudden reversal of 
 motion of the piston, by diminishing the steam pressure. 
 Now, when expansion is used, the greatest pressure is exerted 
 at the beginning of the stroke, when the piston moves slowly, 
 and when it is most advisable to get up a great velocity. The 
 pressure after cut-off diminishes gradually until it is very little 
 greater than that of the atmosphere, so that the steam experi- 
 ences little difficulty in escaping by the exhaust passages on the 
 return stroke. In fast-running engines the exhaust ports are 
 opened before the end of the stroke, and the exhaust port on the 
 other side of the piston is closed, that there may be a cushion 
 of the steam to prevent "shocks" or "jars." 
 
 Action of Steam when Expanded. 
 
 Steam in its ordinary condition as saturated steam, though it 
 does not rank as a perfect gas, nevertheless acts in the cylinder 
 of a steam engine so much to the same effect as a perfect gas 
 could do, that its performance may be treated in the same way 
 as if it were perfect as a gas. The quality in consideration of 
 which a gas is said to be perfect is, as has already been stated, 
 its property of expanding into a larger volume in the same pro- 
 portion inversely as the pressure falls, the temperature being 
 supposed to remain the same. Now, though saturated steam 
 does not and can not exactly follow this ratio, seeing that the 
 pressure falls more rapidly than the volume increases, yet it is 
 found that the work performed by steam by expansion in the 
 cylinder of an engine is practically the same as if it acted on the 
 principle of a perfect gas. 
 
 Therefore, it will be seen that the curve described by the 
 pencil of an indicator indicating the falling pressure of dry 
 saturated steam expanding behind an advancing piston is, if 
 not exactly, nearly hyperbolic in its nature, or such that the 
 products of the pressure at all points of the stroke multiplied 
 by the respective volumes of steam, are equal to each other.
 
 EXPANSION. 
 
 73 
 
 TABLE NO. 3. 
 
 INITIAL AND MEAN EFFECTIVE PRESSURE IN THE CYUNDER. 
 Assuming that the pressures are inversely as the volume. 
 
 
 
 
 Mean Pressure 
 
 Initial Pres- 
 
 Portion of Stroke 
 at which 
 Steam is Cut-off. 
 
 Grade or Ratio 
 of 
 Expansion. 
 
 Hyperbolic 
 Logarithm. 
 
 during the 
 Stroke, the In- 
 itial Pressure 
 being taken 
 
 sure in Cyl- 
 inder, the 
 Mean Pres- 
 sure being 
 
 
 
 
 as i. 
 
 taken as i. 
 
 ' 
 
 g 
 
 X 
 
 mp 
 
 P 
 
 | or 0.75 
 
 1-333 
 1.428 
 
 0.2876 
 0.3506 
 
 0.965 
 0-949 
 
 1.036 
 1.054 
 
 T f or o!&66 
 
 1.5 
 
 0.4055 
 
 0-937 
 
 1.067 
 
 ,% or 0.6 
 
 1.666 
 
 0.5108 
 
 0.904 
 
 1.106 
 
 i or 0.5 
 
 2.0 
 
 0.6931 
 
 0.846 
 
 1.182 
 
 A or 0.4 
 
 2-5 
 
 0.9163 
 
 0.766 
 
 ' I-305 
 
 i or 0.333 
 
 3-o 
 
 0.0986 
 
 0.669 
 
 1-495 
 
 T ff OJ" O. ^ 
 
 3-333 
 
 1.2040 
 
 0.661 
 
 I-5I3 
 
 A or 0.25 
 
 4.0 
 
 1.3863 
 
 0.596 
 
 1.678 
 
 or 0.2 
 
 5- 
 
 1.6094 
 
 0.522 
 
 1.916 
 
 oro.i66 
 
 6.0 
 
 1.7918 
 
 0.465 
 
 2.150 
 
 i or o. 142 
 
 7- 
 
 1-9459 
 
 0.421 
 
 2-375 
 
 or 0.125 
 
 8.0 
 
 2.0795 
 
 0.385 
 
 2.598 
 
 ii or o. in 
 
 9-o 
 
 2.1972 
 
 0-355 
 
 2.817 
 
 TT7 or o. i 
 
 IO.O 
 
 2.3025 
 
 0.330 
 
 3-030 
 
 Y'Y or 0.09 
 
 II. O 
 
 2.3979 
 
 0.309 
 
 3-236 
 
 T ' 2 or 0.083 
 
 12. 
 
 2.4849 
 
 0.293 
 
 3-448 
 
 y 1 ^ or 0.076 
 
 13.0 
 
 2.5649 
 
 0.274 
 
 3-649 
 
 T 1 ^ or 0.071 
 
 14.0 
 
 2.6391 
 
 0.260 
 
 3-846 
 
 T J 5 or 0.066 
 
 15.0 
 
 2.7081 
 
 0.247 
 
 4.048 
 
 fa or 0.062 
 
 16.0 
 
 2.7726 
 
 0.236 
 
 4-237 
 
 1*7 or 0.058 
 
 17.0 
 
 2.8332 
 
 0.226 
 
 4-425 
 
 T V or 0.055 
 fa or 0.052 
 
 18.0 
 19.0 
 
 2.8904 
 2-9444 
 
 0.216 
 0.208 
 
 4.629 
 4.807 
 
 fa or 0.05 
 
 20. o 
 
 2.9967 
 
 0.200 
 
 5.00 
 
 j T or 0.047 
 
 21.0 
 
 3-0445 
 
 0.192 
 
 5-208 
 
 fa or 0.045 
 
 22. 
 
 3.0910 
 
 0.186 
 
 5-376 
 
 ^5 or 0.043 
 
 23.0 
 
 3-1355 
 
 0.180 
 
 5-555 
 
 fa or 0.041 
 
 24.O 
 
 3.1781 
 
 0.174 
 
 5-747 
 
 fa or 0.04 
 
 25.0 
 
 3-2189 
 
 0.169 
 
 5-9I7 
 
 Expansion Diagram of Steam in a Cylinder. 
 
 The hyperbolic curve of expansion, expressive of the falling 
 pressure, relative to the increasing volume, is represented by C 
 g on diagram, Fig. 7. 
 
 The rectangle V B C I 7 is supposed to be the section of a 
 cylinder having a stroke of 24 inches. The diagram is divided 
 into 24 parts, or inches of stroke. During five of these, that is 
 six inches of the stroke, or one-fourth B e, the steam is ad-
 
 THE STEAM-ENGINE AND THE INDICATOR. 
 
 mitted, and it is expanded during the remaining three-fourths 
 m D. Assuming that there is no clearance, the terminal pres- 
 sure g D would be one-fourth of the initial pressure /> during 
 admission, that is, it would be equal to the initial pressure /> 
 taken in this case at 100 pounds total pressure per square inch, 
 multiplied by the period of admission, and divided by the 
 length 1=6 inches of the stroke ; or 
 
 100 X = 25 pounds per square inch, 
 
 the terminal pressure. 
 
 FIG. 7. 
 
 \ 
 
 \ 
 
 \ 
 
 \ 
 
 1 2 3 4 5 6 7 8 9 1O 11 12 13 14 15 16 17 18 19 2O 21 22 23 24 
 
 The pressure for any intermediate point of the stroke may be 
 found similarly, by taking the portion of the stroke described 
 from the commencement to the given point, as the divisor. 
 Thus at the end of 12 inches of the stroke, the total pressure is: 
 
 loo X = 50 pounds per square inch. 
 
 Finding the pressure similarly for each intermediate inch of the 
 stroke, and drawing ordinates for each inch of stroke, the curve 
 may be formed by tracing it through the extremities of the 
 ordinates, as shown in Fig. 6, shown in shaded lines. The 
 one in outline is the best that can be produced in practice. See 
 page 65.
 
 EXPANSION. 75 
 
 From the above it will be seen that the work done by expan- 
 sion may be calculated from the particulars without the aid of 
 hyperbolic logarithms. 
 
 The Theoretical Gain by the Expansion of Steam. 
 
 To find the increase of efficiency arising from using steam 
 expansively : 
 
 Rule, Divide the total length of the stroke by the distance 
 (which call one) through which the piston moves before the 
 steam is cut-off. The Napierian logarithm of the part of the 
 stroke performed with the full pressure of steam before cut-off 
 represents the increase of efficiency due to expansion. 
 
 Example. Suppose that the steam be cut-off at (^) two- 
 tenths, or o. 2 of the stroke, what is the increase of efficiency due 
 to expansion? 
 
 Now, o. 2 of the whole stroke is the same (1) one-fifth of the 
 whole stroke; and the ratio, or grade, of the expansion equals 5. 
 The hyperbolic logarithm of 5 is 1.609, which, increased by i, 
 the value of the portion performed with full initial pressure, 
 gives: 
 
 1.609+12.609 
 
 as the relative efficiency of the steam when expanded to this 
 extent (eight- tenths), instead of i, which would have been the 
 efficiency if there had been no expansion. 
 
 If the steam be cut off at the following points of the stroke, 
 the respective ratios, or grades of expansion, will be as follows: 
 
 Cut off at A, A, T V. A, &, A, T 7 0) A or T 9 *th. 
 
 Grade of expansion 10, 5, 3.33, 2.5, 2.00, 1.66, 1.42, 1.25, i.n. 
 
 Hyperbolic logarithm 2.303, 1.609, I - 2O 3> 0.916, 0.693, 0.47, 0.351, 0.223, 0.104. 
 
 Cut off at , |, f, |, f, f or. 
 
 Grade of expansion 8, 4, 2.66, 2, 1.6, 1.33, 1.143. 
 
 Hyperbolic logarithm 2.079, 1-386, 0.978, 0.693, -47> 0.285, 0.131. 
 
 With the above data, it will be easy to compute the mean 
 pressure of steam of any given initial pressure when cut off at 
 any eighth or any tenth part of the stroke; as we have only to 
 divide the initial pressure of the steam in pounds per square 
 inch by the ratio of expansion, and to multiply the quotient by 
 the hyperbolic logarithm, increased by one, of the number re- 
 presenting the ratio or grade, which gives the mean pressure
 
 76 THE STEAM-ENGINE AND THE INDICATOR. 
 
 throughout the stroke in pounds per square inch. Thus, if 
 steam of 65+1580 pounds absolute, be cut off at half stroke, 
 the ratio or grade of expansion is 2; and 80 divided by 2=40, 
 which multiplied by 1+0.693=67.72 mean pressure in pounds 
 per square inch throughout the stroke. 
 
 The terminal pressure is found by dividing the initial pres- 
 sure by the ratio or grade of expansion; thus, the terminal pres- 
 sure of steam of 80 pounds cut off at half stroke will be: 
 
 - =40 pounds per square inch. 
 
 Example. What will be the mean pressure, throughout the 
 stroke, of steam of 160 pounds per square inch cut off at one- 
 eighth of the stroke? 
 
 First we divide 160 by 8=20, which, multiplied by the hyper- 
 bolic logarithm of 8, which is 2.079+1=3.079. 3.079X20= 
 61.580 pounds per square inch, which is the mean pressure ex- 
 erted on the piston throughout the stroke. If the steam were 
 cut off at rV of the stroke instead of i then we should divide 
 
 160 
 
 This, multiplied by 2.303+1=3.303 gives: 
 
 3-303 X 16 = 52.85 pounds per square inch, 
 
 which would be the mean pressure on the piston throughout 
 the stroke in such a case. 
 
 If the initial pressure of the steam were 10 pounds per square 
 inch, and the expansion took place throughout T V of the stroke, 
 or the steam were cut off at ^th, then 10 divided by 5 = 2, 
 which multiplied by 1.609 + J =2.609; then 
 
 2.609 X 2 = 52.18 pounds per square inch, 
 
 the mean pressure. 
 
 Saving in Fuel by Expansion. 
 
 When steam is cut off before the end of the stroke in a 
 cylinder, the pressure effected by it for the portion at which it 
 flowed for full stroke is represented by i, and the pressure ex- 
 erted afterwards by the result due to the relative expansion.
 
 EXPANSION. 
 
 77 
 
 The total pressure or work is represented by the sum of these 
 units. If the steam had flowed for the full stroke of the piston, 
 the pressure would have been i added to the proportionate 
 distance during which the steam was admitted had it been used 
 expansively. 
 
 The gain of expanding steam by cutting off the supply after 
 the piston has traveled a portion of the stroke: 
 
 Cutting off at T V the stroke, efficiency is increased 3.3 times. 
 i 
 
 2.61 
 
 2.386 
 
 2.203 
 
 1.98 
 
 1.92 
 
 1.69 
 
 I-5I 
 
 1-47 
 
 35 
 
 .285 
 
 .22 
 
 13 
 .IO 
 
 From the above we can compute the gain in fuel as follows: 
 
 Rule. Divide the relative effect, or in other words, the num- 
 ber of times the efficiency is increased by the grade of expansion 
 g (see table of hyperbolic logarithms), and divide i by the 
 quotient. The result is the initial pressure of steam required 
 to be expanded to produce a like effect of steam at full stroke. 
 Divide this pressure by the number of times the steam is ex- 
 panded, and subtract the quotient from i. The remainder will 
 give the percentage of gain of fuel. 
 
 Example. Suppose the steam in an engine cylinder to be cut 
 off after the piston has moved one-fourth the length of the 
 stroke, what is the gain in fuel ? 
 
 The relative effect (see efficiency due to expansion above) 
 equals 2. 386, and the number of times of expansion equals 4. 
 
 Then 
 
 2.386 divided by 4=0.5965, 
 
 and 
 and 
 and 
 
 i divided by 0.5965=1.69 initial pressure, 
 1.69 divided by 4=0.41, 
 I. 0.41=0.59 per cent
 
 78 THE STEAM-ENGINE AND THE INDICATOR. 
 
 Terminal Pressure. 
 
 Rule for finding the pressure at the end of the stroke, or at 
 any point during expansion: 
 
 P initial pressure of steam in pounds per square inch, in- 
 cluding the pressure of the atmosphere. 
 
 L = distance travelled by the piston when the pressure of 
 steam equals x. 
 
 I = distance travelled by the piston before the steam is cut off. 
 
 x = pressure of steam in the cylinder, including the pressure 
 of the atmosphere, when the piston has travelled a distance L. 
 
 PI 
 
 or, in words, the terminal pressure for any cut-off is the abso- 
 lute pressure />, multiplied by the distance /, the piston has 
 moved when steam is cut off, and this product divided by 
 stroke L. 
 
 The steam pressure on the boiler is readily known; but the 
 steam in its passage to the cylinder is subject to various losses, 
 as "wire-drawing," condensation, friction, etc., so that fre- 
 quently the pressure on the piston does not exceed two-thirds 
 of that on the boiler. 
 
 Therefore, recourse must be had to the indicator for furnish- 
 ing the exact data for ascertaining the precise pressure in the 
 cylinder, so as to ascertain the power exerted by the engine, 
 namely, the mean or average pressure of steam; or, more ac- 
 curately, the excess of pressure on the acting side of the piston 
 to produce motive force. And from no other source can it be 
 accurately learned. 
 
 In every branch of science our knowledge increases as the 
 power of measurement becomes improved; and we have now to 
 discuss the measuring instrument peculiarly appropriated to the 
 steam-engine, namely, The Indicator invented by Watt. The 
 student must thoroughly understand the reading of an indicator 
 diagram before he can appreciate the reason for the various 
 methods of construction adopted with reference to some of the 
 working parts of an engine.
 
 EXPANSION. 79 
 
 Expansion Curves of Indicator Diagrams. 
 
 A correct curve does not necessarily show an economical 
 engine, since the leakage out may balance the leakage in, in 
 rare cases, and not affect the diagram. But the opposite is in- 
 disputable, that an incorrect curve necessarily and infallibly 
 shows a wasteful engine, to at least the amount calculated upon 
 the diagram. 
 
 As indicator diagrams represent the measure of force or pres- 
 sure of the steam in the cylinder at every point of the stroke, 
 the actual card from an engine, as compared with the theoretic 
 diagram (other things being equal), indicates the working value 
 and economy of the engine. 
 
 Therefore they should truthfully represent the real perform- 
 ance of the engine. Diagrams vary in form from various 
 causes; namely, quality or condition of the steam, leakage, 
 condensation, adjustment, and construction; their influence 
 being most noticeable in the expansion curve. This curve will 
 not, in practice, conform exactly to the true theoretical curve. 
 The terminal pressure will always, under the most favorable 
 conditions, be found relatively too high, the amount being 
 greater as the ratio or grade of expansion increases. Where 
 this is not the case and the expansion curve of the diagram 
 coincides exactly with the theoretic curve, the conclusion can- 
 not be otherwise than that the leakage is greater than the 
 re-evaporation; but in the present state of the arts there are no 
 practical means of working steam expansively and preserving 
 the exact temperature due to the pressure while expanding. 
 
 When the expansion curve falls throughout its entire length 
 below the hyperbolic or theoretical curve, it is evidently due to 
 leakage. The expansion curve of the indicator diagram, in all 
 ordinary cases, terminates above that of the theoretical curve, 
 in fact, sometimes far above it, due to the re-evaporation of the 
 moisture in the cylinder. An engineer when indicating an 
 engine should see to it that the piston and valves are tight. 
 Unless they are so, the diagram will not indicate what the 
 engine is really doing, and the engineer cannot ascertain the 
 causes of any peculiarities in the form of the diagram.
 
 CHAPTER V. 
 
 THE INDICATOR. 
 
 THE use of the indicator is now very general, and its value is 
 becoming more and more appreciated as an instrument which 
 gives, in skilled hands, exact and valuable information upon 
 various matters connected with the working of the steam engine 
 which formerly were enveloped in mystery. Few high grade 
 engines are now set up without having their valves adjusted for 
 greatest efficiency, as shown by diagrams taken with the indi- 
 cator, nor are these engines accepted by the purchasers without 
 having diagrams taken to show whether the steam is acting 
 properly or not, and to ascertain the horse-power which is 
 developed by the engine, when running at its intended speed 
 and under its proper load. When a man buys an engine, he 
 generally wants to know what it will cost to run it. There is 
 a certain standard to which any engine may be referred in order 
 to judge of its economy, and this is the amount of coal con- 
 sumed per hour for each horse-power developed. Many manu- 
 facturers, while aware of what amount of coal is consumed, are 
 totally ignorant of what power is being yielded by their engines, 
 and hence do not know whether they are working economically 
 or not. They may be losing annually a large amount of money 
 in consequence of having an engine which is wasteful of fuel, 
 and it therefore becomes important to know just what a horse- 
 power is costing, and whether an engine of certain size is really 
 developing that power which calculation shows it ought to 
 be giving. Engines, designed with a special view to great 
 economy, have been run with an expenditure of two pounds of 
 coal per hour per horse-power, and even less than two pounds; 
 but in general an engine may be considered as very good, if it 
 yields a horse-power for every three pounds of good coal con- 
 sumed, per hour. Fuel of poorer quality will require perhaps 
 three and one-half to four pounds, which, bearing in mind the 
 quality of coal, may still be considered a good performance. 
 
 (80)
 
 THE INDICATOR. 8 1 
 
 Engines in general will consume various amounts of coal, other 
 than these figures,. sometimes running as high as nine to twelve 
 pounds per hour per horse power, which is extremely wasteful. 
 
 An indicator diagram enables us to calculate the exact horse- 
 power developed, and, knowing what coal is consumed, we can 
 easily find how much is required per hour per horse-power, and 
 compare the figure found with figures which are considered to 
 represent good economy. Large engines will, in general, be 
 found much more economical than small engines, because, 
 although the sources of loss are the same, the proportion which 
 they bear to the total power is very much less. But it must be 
 remembered that the standard for efficiency referred to, includes 
 the working of both engine and boiler, and that, to produce the 
 best results, each must be designed to secure the highest possi- 
 ble economy. Sometimes a good economical engine is supplied 
 with steam from boilers whose evaporative efficiency is very 
 low, and in such a case, it is not fair to charge the engine with 
 a defect which properly belongs to the boiler. In such instance 
 there can be made a separate test of the boiler. Starting 
 with the known fact that an economical boiler should evaporate 
 say nine pounds of water per pound of coal, and ascertaining 
 next the evaporative capacity of the boiler under test with the 
 coal it is consuming to evaporate a given quantity of water, we 
 will at once arrive at a knowledge of how much below the 
 standard is the boiler under test. 
 
 The indicator enables us also to discover whether there are 
 any defects in those parts of the machinery by which the steam 
 is admitted to the piston, as follows: 
 
 First. It indicates whether the valves are properly set. 
 
 Second. It indicates whether the steam ports are large 
 enough. 
 
 Third. It indicates whether the steam valves are leaky. 
 
 Fourth. Whether a different arrangement of the working 
 parts of the machinery would be advisable. 
 
 Fifth. It will at any time of application, and under any 
 given circumstances, when it may be desirable to apply it, in- 
 dicate what is the actual power developed by the engine. 
 
 In fact, in the hands of a skillful engineer, the indicator is as 
 the stethoscope of the physician, revealing the secret workings 
 6
 
 82 THE STEAM-ENGINE AND THE INDICATOR. 
 
 of the inner system, and detecting minute derangements in 
 parts obscurely situated, and it also registers the power of the 
 engine. 
 
 In principle the indicator is nothing more than an instrument 
 for registering the varying steam pressures in the cylinder dur- 
 ing a complete revolution of the engine shaft, or if there is no 
 shaft, during a complete reciprocation of the piston. 
 
 Construction of the Indicator. 
 
 The indicator considered in its simplest form consists merely 
 of a small piston working in a cylinder with considerable clear- 
 ance, carrying a pencil at the end of its piston rod. One end 
 of this small cylinder is placed, at pleasure, in connection with 
 either end of the steam-engine that is to be indicated, by means 
 of a cock and pipes, and the other end of the indicator cylinder 
 is in free communication with the air, by means of holes drilled 
 in the upper portion of the indicator cylinder or cover, so that 
 if steam goes into the steam-engine cylinder, the pressure is 
 admitted directly to the bottom side of the indicator piston, 
 while upon the other side the air presses continually with 
 whatever the barometric pressure may be at the time. 
 
 A spiral spring is attached to the cover of the indicator 
 cylinder at one end, and to the indicator piston itself at the 
 other end. This spring regulates the movements of the piston, 
 and as the steam is at a greater or less pressure, so the spring is 
 more or less compressed. 
 
 Assuming that the piston of the steam-engine is at one end 
 of the stroke, and just commencing to move, the indicator spring 
 will be compressed by the steam pressure under it, and the 
 amount to which the indicator piston rises is a measure of the 
 steam pressure. For example, supposing that the spring is 
 compressed one-eighth (^) inch for every pound, then, if the 
 steam pressure is ten pounds, the piston will rise one and one- 
 quarter (i y^] inches. As the piston of the engine travels for- 
 ward on its stroke, the steam pressure begins to diminish, and 
 becomes less and less able to compress the indicator spring, and 
 consequently the indicator piston continually falls. In order to 
 register these continually varying pressures, a piece of paper is 
 held on a small cylinder or barrel, in front of the pencil on the
 
 THE INDICATOR. 83 
 
 indicator piston, and as the engine piston moves backward and 
 forward, the barrel of the indicator partially rotates backward 
 and forward; and the curved line traced by the pencil moving 
 vertically up and down on the paper,/ moving at right angles to 
 the up and down movement of the pencil, is called an indicator 
 card or diagram. The diagram is nothing more than a register 
 of the varying pressures in the cylinder as the piston moves to 
 and fro. 
 
 The best forms of indicator as made and sold are commercially 
 known as the "Thompson," "Crosby" and "Tabor," and are 
 so well known and described in the circulars of their respective 
 manufacturers that I will not repeat them here. 
 
 After a card or diagram is taken from a steam-engine, we 
 must see what use can be made of this register of pressures. 
 The connection between a curved figure and the power de- 
 veloped by the engine is not at first sight apparent; and before 
 showing what it is, it is necessary for me to endeavor to clear 
 away all misunderstanding as to what is a true measure of 
 power exerted. Without a most clear and definite conception 
 of what constitutes a mechanical expenditure of work done, it 
 is impossible to form any notion either of what is meant by 
 economical use of steam, or of the connection between the indi- 
 cator diagram and the indicated horse-power. 
 
 The simplest example of an expenditure of power, and also 
 the commonest, is that of a weight raised from the ground. If 
 one pound has been raised one foot high, just half the work has 
 been required which would be required to raise two pounds one 
 foot high. This is so simple a conception as not to require 
 further explanation. A little consideration will show that, 
 generally speaking, the work required to lift any weight to any 
 height may be said to be equal to a certain number of pounds 
 raised one foot high; or what is just the same thing, one pound 
 raised a certain number of feet high, is equal to a certain 
 number of foot-pounds. 
 
 It is a general law in mechanics that when work or power is 
 expended, some resistance has been overcome through some 
 distance, and what is really done in raising a weight is to over- 
 come the attraction of the earth, or gravity, through a certain 
 distance. If we had overcome any other resistance than the
 
 84 THE STEAM-ENGINE AND THE INDICATOR. 
 
 attraction of gravity, as, for instance, compressing a spring, we 
 might, in just the same way, say the expenditure of work was 
 equal to that required to lift a certain number of pounds through 
 a certain height. 
 
 We may take the attraction of gravity as a general standard 
 of resistance, and whenever any resistance is overcome, we may 
 refer it to this standard. 
 
 A steam-engine at work overcomes some resistance, either 
 propelling a vessel, or pulling a train, or driving machinery; 
 and the amount of force or work expended by the engine in 
 overcoming this resistance through a certain distance is equiva- 
 lent to a certain number of pounds raised through a certain 
 number of feet.
 
 CHAPTER VI. 
 
 THE ACTION OF STEAM IN THE CYLINDER OF AN ENGINE. 
 
 THE force of steam in a cylinder is exerted for the perform- 
 ance of work. Steam is introduced into the cylinder at nearly 
 the pressure and temperature at which it is generated. Steam 
 operates in the cylinder in a two-fold manner. First, it is ad- 
 mitted, with a greater or less degree of freedom, from the boiler 
 into the cylinder, during a portion of the stroke, following the 
 piston at or near the boiler pressure. When the communica- 
 tion from the boiler to the cylinder is cut off, and the flow 
 stopped, the quantity of steam enclosed within the cylinder con- 
 tinues, though isolated, to force the piston to the end of the 
 stroke by expansion. 
 
 A two-fold action takes place as follows: 
 
 First. The steam flows into the cylinder and .forces the piston 
 to the point of cut-off. 
 
 Second. After cut-off it is "worked expansively" upon the 
 piston to the point of exhaust. 
 
 In fact, the whole process is essentially one of expansive ac- 
 tion, as the steam admitted direct from the boiler flows into the 
 cylinder by virtue of the expansive force of the steam already 
 generated and being generated, the boiler constitutes the 
 fulcrum or basis. The process is continued on a more limited 
 scale within the cylinder after the steam is cut off, the steam 
 continuing, in virtue of its own elastic force, its expansive action 
 against the piston, when the end of the cylinder constitutes the 
 fulcrum. 
 
 The difference of the steam pressure during the two periods, 
 that of admission and that of expansion, is found by the appli- 
 cation of the indicator. But in certain conditions and adjust- 
 ments of the valves the difference disappears. The uniform 
 pressure of the steam. on entering the cylinder is not in all cases 
 maintained, and it will be found that the steam line falls, as- 
 
 (85)
 
 86 THE STEAM-ENGINE AND THE INDICATOR. 
 
 suming the characteristic of expanding steam. This falling 
 pressure, which takes place while the communication between 
 the boiler and the cylinder is open, is the result of what is ex- 
 pressively called a "wire-drawing" of the steam, the flow of 
 steam into the cylinder being partially arrested at the "steam 
 port" or inlet, by the slide-valve when nearly closed, and the 
 volume being thus reduced or "wire-drawn" to a lower 
 pressure. 
 
 After the steam has passed into the cylinder, and done its 
 appointed work, it is to be expelled, and its discharge should be 
 effected by the time the piston has completed the stroke. It is 
 discharged either into the atmosphere, if a non-condensing 
 engine is employed, opposed by a pressure of 14.7 pounds per 
 square inch, or in round numbers, 15 pounds, or into the con- 
 denser, if a condensing engine is employed, opposed by a resist- 
 ance of about one pound per square inch more or less, according 
 to the excellence of the means of condensation. The piston of 
 an engine, in fact, works between two pressures, and continues 
 in motion or has a tendency to do so as long as the pressure in 
 the boiler is greater than that of the atmosphere or that in the 
 condenser, or more exactly, in the exhaust passage, and when 
 steam is very greatly expanded in a condensing engine, a low 
 pressure in the condenser is no less necessary than a high pres- 
 sure in the boiler. If all losses and difficulties incidental to 
 and perhaps in some degree inseparable from the use of steam 
 of very high pressure be neglected, then it must be maintained 
 that the highest pressure in the boiler, coupled with the lowest 
 pressure in the condenser, would give the highest duty for a 
 given quantity of heat, provided the steam is expanded in the 
 cylinder from the greater pressure down to, or nearly down to, 
 the lower pressure. 
 
 It may here be remarked, that the term "vacuum " is liable 
 to a double interpretation, signifying either the absolute pres- 
 sure in the condenser, or the difference between this and the 
 atmospheric pressure. Now, in regard to the question affecting 
 the quantity of work of steam and its efficiency in the steam- 
 engine, there are the total pressures respectively in the two 
 separate vessels which require to be considered; that is to say, 
 the initial pressure in the cylinder, and the total pressure in the
 
 ACTION OF STEAM IN THE CYLINDER. 87 
 
 condenser, into which the exhausted steam is propelled by the 
 boiler pressure on the piston. If the pressure of the atmosphere 
 were 10 or 30 pounds, in place of (14.7) 15 pounds per square 
 inch, as it is, it would not at all affect the action of a condens- 
 ing engine further than slightly diminishing or increasing the 
 force required to work the air pump, and causing a greater or 
 less weight to be placed upon the safety-valve, in order to obtain 
 the same total pressure in the boiler. When the mercury in an 
 ordinary barometer is observed to stand at a height of 30 inches, 
 and the mercury in another tube communicating with the con- 
 denser of a steam-engine at a height of 5 inches, instead of de- 
 scribing the conditions of the case as representing a vacuum of 
 25 inches of mercury, it would afford a clearer conception of the 
 matter to consider that the total pressure in the condenser is 
 equal to 5 inches of mercury, while the total pressure in the 
 boiler is equal to 30 inches of mercury plus the load on the 
 safety-valve. In short, the operations of a condensing engine 
 are practically independent of the incidental variations of 
 atmospheric pressure. 
 
 But, the operations of a non-condensing engine, exhausting 
 into the atmosphere, are referable to the atmospheric pressure, 
 as it affords the datum or base line to which the expansive and 
 exhaust pressure should be approximated, and below which the 
 former should not, and the latter cannot, be extended. It is 
 usual, therefore, in dealing with non-condensing engines, to 
 designate the pressure of steam by the difference or excess of its 
 pressure above that of the atmosphere namely (14.71) 15 
 pounds absolute pressure per square inch ; this absolute pressure 
 being adopted for the zero of the non-condensing scale. 
 
 In supplying an engine with steam, four distinct events take 
 place in consecutive order with respect to each end of the 
 cylinder, as follows: 
 
 First The admission of the steam at, or just before, the be- 
 ginning of the stroke. 
 
 Second The suppression, or cut-off, of the steam. 
 
 Third The release, or exhaust, of the steam. 
 
 Fourth The closing of the exhaust valve, causing "com- 
 pression," or "cushioning," of the exhaust steam, prior to 
 the opening of the steam port.
 
 88 
 
 THE STEAM-ENGINE AND THE INDICATOR. 
 
 These four events, together, constitute the "distribution" 
 for the cylinder; and their duration, measured in parts of the 
 stroke, are the "periods of the distribution." 
 
 By the aid of the indicator, which, as its name implies, is a 
 sort of stethoscope for the observation of what transpires within 
 the cylinder a simple instrument for receiving and registering 
 the pressure of the steam a minute and accurate picture of the 
 operation within is transferred by pencil to paper, affording 
 valuable and, indeed, indispensable data for the measurement 
 of the power and efficiency of the steam in the cylinder. 
 
 The Action of Steam in the Cylinder as Shown by the Indi- 
 cator Diagrams. 
 
 The action of steam is illustrated in its most simple form in 
 the non-condensing or "high-pressure" engine, in which the 
 question of the vacuum does not enter. 
 
 PIG. 8. 
 B. Steam Stroke > O 
 
 <- - - Admission - Cut^Off X Exhaust 
 
 The function and utility of the indicator, as a means by 
 which the action of the steam in the cylinder is portrayed, will 
 appear by an examination of the diagram Figure 8. 
 
 The base line A D is the line of atmospheric pressure, m D 
 represents the stroke of the piston, and the irregular space
 
 ACTION OF STEAM IN THE CYLINDER. 89 
 
 w, , e and D y may be supposed to be the interior of the 
 cylinder. The heavily lined figure k, e, f, g, h, and z, is a 
 diagram of the indicated action of the steam, when the piston 
 moves in the cylinder at an average speed of 100 feet per min- 
 ute; and shows by its angularity how the steam is controlled by 
 the valve, and the precise points of the stroke at which the 
 changes of the distribution take place. The piston is repre- 
 sented as having started from the left-hand end of the cylinder, 
 under an initial steam pressure of 45 pounds per square inch 
 above the atmosphere, the line of pressure being traced from 
 the upper left-hand corner k, until it reaches the point e of cut- 
 off. The admission being terminated, the period of expansion 
 is commenced, the pressure falls as the piston advances before 
 the expanding steam, and continues to do so until the piston 
 reaches the point of release f. At this point the piston enters 
 on its third and last stage of progress toward the end of the 
 stroke; the steam primarily admitted at 45 pounds above the 
 atmosphere, and reduced to 15 pounds pressure previously to 
 being released, quickly discharges itself into the atmosphere, 
 by its elasticity, and is entirely discharged before the end of the 
 stroke, as indicated by the rapid fall of the steam line during 
 the period of exhaust towards the point g. The exhaust is, 
 however, only relative, not absolute, as steam of atmospheric 
 pressure remains in the cylinder, though not obviously sensible 
 in the indicator diagram, during the return stroke; therefore, 
 the valve ought to maintain the exhaust end of the cylinder 
 continuously open, to allow the steam of one atmosphere of 
 pressure to escape from before the returning piston. The 
 benefit of this provision is proved by the diagram, in which it 
 appears that during the continuation of the exhaust the steam 
 of latent pressure remains at the zero point of the scale; at the 
 instant the exhaust valve closes at the point of compression ^, 
 and there is no longer an exit for the latent steam before the 
 piston, the exhaust line commences to rise upwardly towards 
 the left-hand side, and the steam is compressed against the end 
 of the cylinder. While the volume of the compressed steam is 
 being thus forcibly reduced, the pressure is increased; the pres- 
 sure is raised until the accumulation of back pressure so induced 
 is merged at ?', with the boiler pressure of the steam admitted at
 
 90 THE STEAM-ENGINE AND THE INDICATOR. 
 
 this point by lead during the remainder of the return stroke for 
 the supply of the next stroke. 
 
 The action of the steam in the cylinder may thus, with the 
 aid of the indicator-diagram, the different sections of which are 
 distinctly marked, be clearly traced through the revolution of 
 the engine. 
 
 The period of admission, in the example just described, is 
 about two- thirds of the whole stroke; that of expansion about 
 three-tenths; and a simple inspection of the diagram shows that, 
 in this case, nearly one-third of the work of the steam is per- 
 formed by simple expansion while shut up in the cylinder. 
 Even the period of exhaust supplies its quota of effect, inasmuch 
 as the exhaust is a work of time; and the extra positive pressure 
 so yielded is represented by the small triangular space fg and d, 
 between the point of release and the end of the stroke at D. The 
 force developed by the compression space h m and i is properly 
 designated resistance, as it is opposed to the motion of the 
 piston, and must be classed with the slight opposition also made 
 by the lead or entering steam at i for the next stroke. 
 
 Engine Power. 
 
 To ascertain what power an engine is exerting, the simplest 
 way is to find out how many pounds weight it raises in a min- 
 ute, and through how many feet it raises such weight; the term 
 minute is used as a convenient unit of time, and it is the unit 
 generally adopted. 
 
 Now, let us take as an example the following indicator 
 diagram Fig. 9, and divide it into ten equal spaces. The dis- 
 tance, from A to B is one-tenth of the whole length of the indi- 
 catoi card, and during the time the card traveled horizontally 
 from A to B, the piston of the engine traveled one-tenth of its 
 stroke; while the card traveled from B to C, the piston of the 
 engine traveled another one-tenth of* its stroke, and when the 
 piston had traveled its whole stroke, the card would have 
 traveled from A to K, and so backwards on the return stroke. 
 It is not a matter of any importance what the length A K is 
 when compared with the stroke of the piston, and for conveni- 
 ence A K is usually made about four inches, excepting in high 
 speed engines. All that we care about is, that when the piston
 
 ACTION OF STEAM IN THE CYLINDER. 91 
 
 has moved through one-tenth of its stroke, the card shall have 
 done so also, and that the motions go on corresponding in this 
 way throughout the stroke. Then we have only to look at the 
 indicator card to see what pressure of steam there was in the 
 
 CPE P O H I J K 
 
 17 16 15 14 13 12 11 
 
 cylinder at any part of the stroke. In this particular case 
 a *V spring was attached to the piston of the indicator, which 
 means that for every one pound pressure on the square inch of 
 the piston, the pencil of the indicator will rise ?T of an inch. 
 If we have 48 pounds boiler pressure, the pencil will rise two 
 (2) inches as soon as the steam is admitted up to the point i; 
 then, as the piston and card move, the pencil, still held up by 
 the steam, moves to 2, then to 3. Somewhere about this point 
 the steam is cut off, then the steam pressure falls as the piston 
 moves on, and the pressure can no longer compress the spring 
 so much, and the pencil falls gradually to 4, then to 5, and so 
 on to 10, where the steam is exhausted into the air, and the 
 spring being no longer compressed, the pencil falls to the line 
 called atmospheric line. 
 
 At ii the engine begins the return stroke, and up to 19 the 
 steam continues to exhaust into the air; at this point the valve
 
 92 THE STEAM-ENGINE AND THE INDICATOR. 
 
 closes, and what is left in the cylinder is compressed until the 
 point 21 is reached, when steam is admitted again and the 
 spring compressed up to I. 
 
 From this curved figure we must now find what power the 
 engine was exerting. We measure the distance in the center 
 of each of the spaces A B, B C, CD, up to and including /A", 
 by a scale which has the inch divided into 24 spaces, each space 
 on the scale represents one pound, on dotted lines drawn be- 
 tween the above spaces A B etc. These pressures added to- 
 gether and divided by ten the number of spaces will give 
 the mean effective indicated pressure acting on the piston 
 during one stroke. 
 
 To find the foot pounds raised per minute, we multiply the 
 area of the piston by the mean pressure and by the stroke 
 multiplied by two. 
 
 FIG. 10. 
 
 If the engine is a double-acting one, the diagrams for each 
 end of the cylinder are usually taken on the same card, giving 
 a double figure, as in fig. 10. Bach of these diagrams has its 
 own mean pressure, and they are rarely the same. In practice 
 they are nearly always treated as above; the horse-power for 
 each end of the cylinder being rarely calculated separately. In 
 the present instance the mean pressure of the left-hand diagram 
 is 28.16 pounds, and that of the right-hand one 29.22 pounds; 
 the mean of both is 28.69 pounds. To find the foot-pounds 
 raised per minute we multiply the mean pressure, 28.69, by 
 twice the stroke in feet, by the number of revolutions per min- 
 ute, and by the area of the piston in square inches. 
 
 Example. Assuming the diameter of the cylinder to be 12
 
 ACTION OF STEAM IN THE CYLINDER. 93 
 
 inches and the stroke 24 inches, making 200 revolutions per 
 minute, what number of foot-pounds will be exerted? 
 
 28.69 X 200 X 2 X 113 = 1,296,788 foot-pounds per minute. 
 
 Having now shown what power an engine is exerting in the 
 simplest way, that is to say, how many pounds weight it raises 
 in a minute, we will now explain how Watt arrived at this 
 method.
 
 CHAPTER VII. 
 
 HORSE-POWER. 
 
 THE power of a horse, or that part of his muscular force 
 which in traveling he is capable of applying upon the load, has 
 been variously stated by different authors. It is not the force 
 exerted by a dead pull, or for a short period, by which we are 
 to estimate a horse's strength, but what he can exert daily, for 
 a long period, without injury to his powers. That is the 
 standard for practice. 
 
 The real horse-power, that which a good horse can lift, ac- 
 cording to experiments made by Smeaton, is twenty-two thou- 
 sand (22,000) pounds one foot high per minute. This power 
 was derived from the average force exerted by the ordinary 
 draft-horses working at mines. Early English miners had no 
 other means of raising ore. Their apparatus consisted of a fixed 
 pulley at the surface, over which a rope passed. To one end of 
 this rope a horse was hitched, and to the other end a bucket, 
 which latter, on being lowered in the mine and loaded, was 
 raised to the surface by the horse walking horizontally from the 
 pit. London brewers also used horses for pumping by gins 
 and winches. 
 
 Horse-power of a Steam-engine. 
 
 When James Watt began to replace the old-fashioned horse- 
 gins and winches for pumping water with his steam-engine, he 
 soon found that some standard of power should be adopted, to 
 enable his customers to obtain an engine suited to the purpose. 
 It was natural that the horses superseded by the steam-engine 
 should be used as the standard of comparison, and thus the 
 term "horse-power" was introduced. About the year 1784, 
 James Watt was making engines for the London brewers, who 
 were using horses for pumping purposes. When they wished 
 to know what power one of Watt's engines would exert, they 
 asked him how many horses it would be equivalent to. 
 
 (94)
 
 HORSE-POWER. 95 
 
 Watt set to work to determine by a series of practical experi- 
 ments what a horse-power was. It meant nothing to tell them 
 that the engine had such a sized cylinder, made so many revo- 
 lutions per minute, with steam of so many pounds pressure per 
 square inch. They knew nothing of cylinders and steam pres- 
 sures, but as long as the term "horse-power" was one of 
 definite meaning, they could understand that. Watt ascer- 
 tained, therefore, that a good London horse could go on lifting 
 one hundred and fifty (150) pounds over a pulley at the rate of 
 two and one-half (2^) miles an hour, or two hundred and 
 twenty (220) feet per minute, and continue the work for eight 
 (8) hours a day. Now the mechanical work done in this case is 
 the same as lifting 220 times the weight through the ^ part of 
 the distance in the same time, thus: 
 
 5280 X 2.5 = 13,200 feet traveled per hour, 
 
 60 
 
 X 150 = 33,000 pounds lifted one foot high per minute, 
 
 = 350 pounds lifted one foot per second. 
 
 This experiment resulted in his taking as a unit of power 
 33,000 pounds lifted one foot high in a minute, which is the 
 same as a force of 550 pounds acting with a velocity of one foot 
 per second. He called this manifestation one horse-power. 
 
 This power he guaranteed to all his early engines, so that the 
 purchaser, having one and a half times the power of a good 
 horse, should not be in a position to complain of the engine as 
 being inadequate. 
 
 This standard, or unit of power, has been retained to the 
 present day to express a horse power. In his own practice he 
 obtained an effective steam-pressure, including the vacuum, of 
 course, (for he used steam but little above the atmospheric pres- 
 sure,) of seven (7) pounds per square inch; and he found that his 
 piston speed was about one hundred and twenty-eight (128) 
 times the cube root of the stroke of the cylinder in feet per 
 minute, being one hundred and twenty-eight (128) feet for a one 
 foot stroke, and two hundred and fifty-six (256) feet for an eight 
 (8) foot stroke, It became his habit, therefore, to estimate the 
 power of his engines, and as he took good care to conform to
 
 96 THE STEAM-ENGINE AND THE INDICATOR. 
 
 his actual practice, his estimates were always very near the 
 mark. 
 
 At the time Watt introduced this measurement, steam was 
 used only at the atmospheric pressure, or (14. 7) 15 pounds on 
 the square inch, of which 4.7 pounds was considered to be lost 
 by imperfect condensation, and three pounds by the friction of 
 the engine, leaving, as before stated, seven (7) pounds for 
 effective steam-pressure upon the piston. The speed of piston 
 employed averaged two hundred and twenty (220) feet per 
 minute. 
 
 Watt then calculated the power of his engine by multiplying 
 the square of the diameter of the piston in inches by the cube 
 root of the stroke in feet, and dividing the product by sixty (60). 
 This rule would give a horse power for about seven (7) pounds 
 per square inch of piston, supposing it to move at one hundred 
 and twenty feet per minute. 
 
 When Watt first used the term horse power for raising coal 
 and pumping water, it meant work actually done in the pumps, 
 etc., not the work done by the steam. 
 
 To determine the horse-power of an engine, Watt, and those 
 who immediately followed him, supposed every square inch on 
 the piston to be able to lift a weight of seven pounds; and when 
 doing this work, it was found that the piston would move 
 through two hundred to two hundred and fifty-six feet a minute 
 in a double-acting engine. The area of the piston in square 
 inches multiplied by seven pounds, multiplied by the number 
 of feet traveled through per minute, divided by thirty-three 
 thousand (33,000), was called a horse-power. It is curious to 
 observe that the seven pounds mentioned here were not sup- 
 posed to be seven pounds of mean steam pressure on the piston, 
 but seven pounds of pressure actually transmitted through the 
 pump-rods, and was equivalent to .considerably more than seven 
 pounds of steam-pressure, for all the friction of the machine had 
 to be added, as well as the power required for the air pumps, etc. 
 
 Smeaton considered that in his improved engines of New- 
 comen's type, which preceded Watt's, while his mean steam- 
 pressure was 10.5 pounds, 1.74 pounds or 16^ per cent, of this 
 was exerted in overcoming friction. Now it means the work 
 done by the steam; from this the friction of the moving parts
 
 HORSE- POWER. 
 
 97 
 
 must be deducted before we get at the power transmitted through 
 the shaft. 
 
 All of Watt's calculations were made accordingly, and thus 
 at its first introduction the term " nominal horse-power" really 
 meant something which bore a fixed relation to a real horse- 
 power, and at the time, the use of the term was found not only 
 convenient but almost indispensable. 
 
 At the present day, pressures are employed as high as five 
 hundred pounds per square inch, and instead of piston-speeds 
 of one hundred and twenty-eight times the cube root of the 
 stroke, the length of stroke is now known to have but little in- 
 fluence on the speed, and we have many engines running at six 
 hundred times the cube root of the length of their stroke, in 
 feet per minute. 
 
 Originally, the number of horse-power defined at once the 
 size and the power of an engine; but when a variety of steam- 
 pressures and speeds came to be employed, the same expression 
 could no longer answer both purposes, and a distinction was in- 
 troduced, which still prevails, between the nominal and the 
 actual horse-power; the former being applied to the size of 
 engine, irrespective of the pressure or speed employed, and the 
 latter to the power which they exert. 
 
 The term nominal horse-power has, moreover, acquired a 
 variety of significations in different localities, and it has become 
 difficult to tell, in any case, precisely what is meant by it. In 
 fact, it is merely an expression for the diameter of cylinder and 
 length of stroke, or a measure of the dimensions of an engine, 
 without any reference to the amount of power actually exerted 
 by it. 
 
 The term nominal is now commonly confounded with the 
 term commercial as applied to the horse-power of engines, and 
 the name theoretical horse-power is substituted to represent the 
 received scientific horse- power of 33,000 foot pounds lifted one 
 foot high in one minute. 
 
 In the present advanced state of engineering the term nominal 
 horse-power is seldom used; engineers, although employing the 
 term, do so with mental reservation, or at least mentally define 
 it in consideration of pressure per square inch, area of piston in 
 square inches, and velocity of piston in feet per minute. 
 7
 
 98 THE STEAM-ENGINE AND THE INDICATOR. 
 
 Work is done when a force overcomes resistance through any 
 space. For instance, the force of gravity acting on a mass of 
 one pound of anything is commonly called a force of one pound; 
 and if the weight be allowed to move downwards any distance, 
 whether we still hold it in our hand, or allow it to fall freely 
 vertically, or down a curve or an inclined plane, so that there 
 is always a distance traversed by it in a vertical direction, the 
 force of gravity is said to do work. Again, in lifting a weight, 
 we do work, for we overcome the force of gravity through a 
 distance. Pressure in a boiler does no work on the shell, but 
 the steam, if properly directed, will do work. Pressure on a 
 piston does work when the piston yields to it. This work, 
 divided by the time in which it is executed, gives the power. 
 
 Work is, therefore, the product of three simple elements, 
 force, velocity and time, as has been already stated. 
 
 Power is the product of force and velocity; that is to say, a 
 force multiplied by the velocity with which it is acting is the 
 power in operation. 
 
 The work done by a force is measured by the product of the 
 force into the distance through which it acts. The unit of 
 work commonly employed is the work done by gravity on the 
 mass of one pound in falling through one foot, and is commonly 
 called a foot-pound. A force of fifty pounds acting through a 
 distance of four feet is said to do: 
 
 50 x 4 = 200 foot pounds of work. 
 
 The number of units of work performed in a given time, say 
 one minute, is a measure of the efficiency of the agent em- 
 ployed. 
 
 Man- power. 
 
 Man-power is a unit of power^ established by Morin, to be 
 equivalent to fifty foot-pounds of power, or fifty effects; that is 
 to say, a man turning a crank with a force of fifty pounds and 
 with a velocity of one foot per second is a standard man-power. 
 An ordinary workman can exert this power eight hours per day, 
 without overstraining himself. 
 
 Horse-power is a unit, as before stated, of power established 
 by Watt, to be equivalent to a force of five hundred and fifty
 
 HORSE-POWER. 
 
 99 
 
 pounds acting with a velocity of one foot per second, which is 
 the same as a force of thirty-three thousand pounds acting with 
 a velocity of one foot per minute. That is to say, one horse- 
 power is five hundred and fifty foot-pounds of power or effects, 
 or eleven man-power of fifty effects each. The product of any 
 force in pounds, and its velocity in feet per second, divided by 
 55) gives the horse-power in operation. 
 
 In Watt's rule for horse-power is given a velocity of only one 
 foot per minute, which is equal to two-tenths (o. 2) or \ of an 
 inch per second about the velocity of a snail. The force 
 corresponding to this velocity is 33,00x3 pounds, or about 15 
 tons, which is too large for a clear conception of its magnitude, 
 and a horse can never pull with such a force. A horse can pull 
 550 pounds with a velocity of one foot per second, which is the 
 most natural expression for horse-power. This expression is 
 used on the continent of Europe. 
 
 FOREIGN TERMS AND UNITS FOR HORSE-POWER. 
 
 Countries. 
 
 Terms. 
 
 English 
 Translation. 
 
 Unit. 
 
 English 
 Equivalent. 
 
 English 
 French 
 German 
 Swedish 
 
 Horse-power. 
 Force de cheval. 
 Pferde-kraft. 
 Hist-kraft. 
 
 Horse-power. 
 Force-horse. 
 Horse-force. 
 
 550 foot-pounds. 
 75 kilogr. -metres. 
 513 Fuss-pfunde. 
 600 skal-pund-fot. 
 
 550 foot-pounds. 
 542.47 foot-pounds. 
 582.25 foot-pounds. 
 
 Russian 
 
 Sul-lochad. 
 
 Force-horse. 
 
 550 Fyt-funt. 
 
 550 foot-pounds. 
 
 An engine which raises 550 pounds through one foot in one 
 second is said to accomplish one horse-power. 
 
 When absolute horse-power of a steam engine is required, the 
 "Indicator" is attached to the engine cylinder so as to be in 
 communication with each side of the piston, and the action of 
 the steam in the cylinder is registered on a piece of paper called 
 a card or diagram, from which the average steam -pressure on 
 the piston can be calculated. 
 
 Example. A steam-engine the area of whose piston is A = 
 i TO square inches, the mean pressure on the piston by the in- 
 dicator diagram is p = 50 pounds per square inch. Now the 
 product, A p = no X 50 = 5500 pounds, expresses the whole 
 pressure on the piston; this multiplied by the length of the 
 stroke, L = 2 feet, will give 5500 X 2 = n,ooo foot-pounds, 
 the amount of work done in one stroke of the piston; and this
 
 IOO THE STEAM-ENGINE AND THE INDICATOR. 
 
 product multiplied by the number of strokes, s = 10 in one 
 second, gives: 
 
 A p L s = no X 50 X 2 X 10= 110,000 foot-pounds done by 
 the steam in one second of time; this divided by 550 gives the 
 horse-power; hence the expression: 
 
 A * L * = "0X50X2X10 20Q h 
 
 550 550 
 
 Duty. 
 
 In large engines, especially pumping engines, the term 
 "duty" is a measure of their efficiency, and is applied to indi- 
 cate the number of millions of pounds raised through a height 
 of one foot by the burning of one hundred pounds of coal in 
 England one hundred and twelve (112) pounds is used. But 
 this measure, though suitable for estimating the work done by 
 pumping engines, is not convenient for other purposes, and it 
 has become the more common practice to estimate the perform- 
 ance of an engine by ascertaining the number of pounds of coal 
 burnt per hour for each horse-power at which the engine is 
 working. This gives a useful measure in small numbers, easily 
 remembered. 
 
 It was formerly a common performance with steam-engines 
 to consume from four to ten pounds of coal per hour per horse- 
 power. In the present state of the arts a first-class automatic 
 cut-off engine very seldom exceeds the former, and in order to 
 form an idea of the number of pounds that should be consumed 
 per hour per horse-power, we deduce the duty of a modern 
 engine as follows: 
 
 Example. Let the duty be estimated by the burning of one 
 hundred pounds of coal. Then four pounds do the work rep- 
 resented by 550 x 60 x 60 = 1,980,000 foot-pounds per hour. 
 Therefore one hundred pounds do the work represented by: 
 
 1,980,000 X loo _ 49)500)000 foot-pounds, the duty of the engine. 
 4 
 
 This being so, it follows that the duty of an engine which 
 would produce a horse-power by the consumption of one pound 
 of coal per hour per horse-power would be four times as great, 
 or would be represented by 198,000,000 foot-pounds.
 
 HORSE-POWER. IOI 
 
 The progress made in the economy of fuel by successive im- 
 provements in the steam engine may be readily traced by com- 
 parison of the number of pounds of coal burnt per hour per 
 horse-power. 
 
 Thus, in Smeaton's early engines, on Newcomen's principle 
 in 1775, the consumption was thirty pounds of coal per hour 
 per horse-power. In his later engines it was improved to 
 eighteen pounds per hour. 
 
 In Cornish pumping engines originally the consumption was 
 eleven pounds, in the year 1811; in 1842, one and three-quarter 
 pounds; and in 1872, it had increased to three pounds. It is 
 said that Watt began with eight pounds and reduced the con- 
 sumption to three pounds. 
 
 Mr. George H. Corliss, in 1878, reduced the consumption of 
 coal per hour, per indicated horse-power, to one and seven-tenths 
 pounds; coal per effective horse-power per hour was one and 
 eight-tenths pounds; duty 109,979,487 foot-pounds for each one 
 hundred pounds of coal. 
 
 Mr. E. D. Leavitt, Jr. , about the same time, consumed one 
 and sixty-three hundreths pounds of coal per indicated horse- 
 power per hour, and the duty was 111,548,925 foot-pounds for 
 each one hundred pounds of coal consumed. 
 
 Prior to 1860, the average consumption of coal for driving the 
 best marine and stationary engines was about four pounds per 
 hour per horse-power, as per indicator diagrams. In 1872 it 
 appeared, from a comparison of nineteen ocean steamers, that 
 the consumption had been reduced to an average of two and one- 
 tenths pounds, being a saving of about fifty per cent. , and in 
 stationary engines the average was three pounds, a saving of 
 about thirty- three per cent. 
 
 One pound of ordinary coal develops in its combustion about 
 ten thousand units of heat, which, in their turn, represent: 
 
 10,000 X 772 = 7,720,000 foot-pounds of work. 
 
 This number of foot-pounds represents a consumption of about 
 one-quarter of a pound of coal per hour per indicated horse- 
 power; whereas few engines of the present day produce an in- 
 dicated horse-power with less than ten times that consumption, 
 or say two and one-half pounds of coal.
 
 IO2 THE STEAM-ENGINE AND THE INDICATOR. 
 
 Horse-Power by the Indicator. 
 
 From the experiments of Watt the standard unit of work or 
 power, as before stated, is one pound lifted twelve inches, or 
 one pound of force acting through one foot of space, and is 
 called the foot-pound; and 33,000 foot-pounds, or units of work, 
 performed in one minute, or 550 foot-pounds in one second, 
 make a horse-power. 
 
 We have also shown how to calculate the number of foot- 
 pounds raised by the engine per minute, and if we divide that 
 number by 33,000 we get the indicated horse-power of the 
 engine. 
 
 If the engine is a single-cylinder one, the indicated horse- 
 power is: 
 
 Area of Cylinder x Mean-pressure X Revolutions X 2 X Stroke 
 33,000. 
 
 If the engine were a double-cylinder one, the power of both 
 cylinders would have to be added together to get the power of 
 the engine. 
 
 Where there are a number of cards all taken from the same 
 engine to be calculated out, a further simplification is made. 
 Instead of multiplying the area of the piston by 2, and by the 
 stroke, and dividing by 33,000 each time for each card, we may 
 find what this sum, which is invariable for each particular 
 engine, is, and multiply it by the mean pressure and the revo- 
 lutions. This quantity is called the horse-power constant for the 
 engine, and is the number of horse-powers which would be ex- 
 erted by one pound of mean pressure. It is found by multiply- 
 ing together the area of the piston in square inches and the feet 
 traveled by it per minute, and dividing the product by 33,000. 
 
 In illustration of the above rules, we will compute the horse- 
 power exerted in the following diagram, taken from the cylinder 
 of a Corliss engine. The diameter of piston was six inches, the 
 length of stroke sixteen inches, and the revolutions per minute 
 108; diameter of piston rod one and one-half inches. What is 
 the horse-power of this engine by the indicator? 
 
 Cylinder, 6 inches diameter; stroke, 16 inches; revolutions, 
 108; boiler pressure, 70 pounds. To find the mean effective 
 pressure on the piston, proceed as follows:
 
 HORSE- POWER. 103 
 
 Divide the card into ten equal spaces and measure the length 
 of each dotted line or ordinate by the scale corresponding to the 
 spring of the indicator (which in this case is 30 pounds equal 
 to one inch in height). The sum of the lengths of the ten or- 
 dinates amounts to 344 pounds, which divided by ten, the num- 
 ber of ordinates, gives an average mean effective pressure of 
 34.4 pounds per square inch. 
 
 FIG. ii. 
 
 To calculate the indicated horse-power, multiply the area of 
 the piston in square inches by twice the length of the stroke in 
 feet, and the product by the number of revolutions per minute. 
 (This product is known as the " piston displacements' 1 } Divide 
 this product by 33,000 and the result is the " ''horse-power con- 
 stant"" 1 or the power developed for every pound of mean effective 
 pressure. Multiply the quotient by the mean effective pressure, 
 (ascertained from the diagram) and the result will be the indi- 
 cated horse-power. 
 
 The area of the piston = 6 X 6 X 0.7854 = 28.274." 
 The area of the piston rod = I ' 5 X I>5 X -7 8 54 _ o
 
 104 T HE STEAM-ENGINE AND THE INDICATOR. 
 
 Average area of piston, less one-half area of rod, 27.391. 
 (28.274 0.883 27.391.) 
 
 The speed of piston in feet per minute l6 X 2 X Io8 = 288 feet. 
 The constant for this engine is, therefore, 
 
 HP 27 ' 391 x 28S = 0.239, the horse-power constant. 
 33,000 
 
 The mean pressure, as per diagram, is 34.4 pounds, and the 
 power developed is, 
 
 HP 34.4 X 0.239 = 8.22 horse-power. 
 
 Where great accuracy is required in estimating the power of 
 steam-engines from indicator diagrams, care should be taken to 
 calculate the power of forward and back strokes separately, as 
 the mean effective pressures are not always alike. 
 
 In this manner the power exerted by an engine may be as- 
 certained under every variety of circumstances, and also the 
 power required for every kind of machine. 
 
 Measuring the power required by a single machine among 
 many running in a manufactory requires great care, but can be 
 done with certainty, even to a small fraction of a horse-power. 
 It is necessary that every thing should be in the same condition 
 during the whole experiment. The proper time to test is after 
 running for several hours, and directly after stopping, when 
 everything is in the best working condition; say, at noon-time. 
 First indicate for the shafting alone, afterwards put on the 
 machine to be tested, the power required for which is to be as- 
 certained; after it has been running for a few minutes, and, 
 finally, after the belt has been thrown off, indicate for the shaft- 
 ing again. 
 
 In case the pencil should run over the paper several times, it 
 should be ascertained if it follows the diagram exactly when re- 
 moved a little from the paper. The first and third diagrams 
 (that is the friction diagram of the shafting) should be identi- 
 cal, and the excess of the second diagram is the power required 
 by the machinery tested. Care should be observed that all 
 the diagrams are taken at the same speed of the engine.
 
 HORSE-POWER. 105 
 
 In all cases the greatest pains should be taken to determine 
 if the diagrams are a true representation of the power exerted. 
 See if the pencil will repeat the diagram both when in contact, 
 and when not in contact with the paper. Often the diagram 
 will not repeat exactly. Whenever this is the case, the pencil 
 must be allowed to run over the paper a sufficient number of 
 times, and the average of all the figures must be taken as the 
 true one. 
 
 As before stated, the indicator-card is usually run out, or in 
 other words, the mean pressure of the card is usually ascertained 
 by reading off with the aid of the scale the different mean pres- 
 sures on each of the ten spaces; then adding them together and 
 dividing them by ten, or whatever number of spaces there are. 
 This is correct, provided each reading is an accurate one. The 
 following is a far better and easier method: Take a long strip 
 of paper, say one-half an inch wide, and from 10 to 20 inches 
 long, according to the nature of the card. Mark a starting 
 point on the edge near one end. Then lay the strip of paper 
 along the first dotted line and mark off the length of second 
 dotted line, then lay it on the second space and add the length 
 to second dotted line, and so on to the tenth dotted line. By 
 this means the lengths of each of the ten lines are laid end to 
 end. If we now take a rule and read off how many inches there 
 are in the whole length, and divide them by ten, we get the 
 number of inches in the mean pressure of the whole card. 
 
 Generally expressed, we multiply the total number of inches 
 read off the strip by the scale, and divide by ten. 
 
 This is one of the best and safest, if not the very best, way of 
 finding the mean pressure of a card or diagram; it is certainly 
 greatly superior to the method of reading off ten different pres- 
 sures, and adding them together and dividing by ten as hereto- 
 fore described. 
 
 How to Divide a Line Into a Number of Equal Spaces. 
 
 A foot-rule or scale is usually divided into inches, halves, 
 quarters, eights and tenths of an inch; and, when the line 
 to be divided into a required number of equal spaces is a 
 multiple of those spaces, it is, of course, easy to divide it. 
 Thus it is easy, by applying the rule, to divide a line four
 
 io6 
 
 THE STEAM-ENGINE AND THE INDICATOR. 
 
 inches long into four inch spaces, or eight half-inch spaces 
 or sixteen quarter-inch spaces, or thirty-two eighth-of-an- 
 inch spaces. But, when the line is not such a multiple of 
 the space, it cannot be divided by applying the rule to it; and 
 the following method may be used: For instance, a line 41 
 inches long is to be divided into ten equal spaces. First draw 
 a line at right angles to the given line, at one end of it; then 
 take a strip of paper, and, applying the rule to the strip, mark 
 off on it ten equal spaces, which together will exceed the length 
 of the given line; then place one end of the strip at the open 
 end of the given line, and carry the other end of the strip up 
 
 FIG. 12. 
 
 iintil the last point marked off on it touches the right-angled 
 line, and through the points on the strip draw lines parallel 
 with the right-angled line to the given line; and the given line 
 will be divided as required. 
 
 Thus let A B, Fig 12, be the given line; draw B D at right 
 angles to it; the first 10 equal spaces on the rule, which will 
 exceed the length of A B (2^ or 2.062) will be ten one-quarter 
 inches; mark this ten one-quarter inches off on a strip A to C; 
 place the end A of the strip to the end A of the line, and move 
 up the strip until the point C touches B Z?/and, through points 
 i, 2, 3, 4, 5, 6, 7, 8, 9, and 10 on the strip, draw lines #, , c, 
 e ift &i h, i, and m, parallel with B D ; and the line A B will 
 be divided into ten equal spaces.
 
 HORSE-POWER. 
 
 107 
 
 To those who are frequently in the habit of computing the 
 horse-power of engines from diagrams, this method will be 
 found very advantageous. 
 
 The Planimeter. 
 
 In the present state of the arts there is a most ingenious in- 
 strument called a planimeter, which is now in general use for 
 finding the mean pressure. This instrument not only enables 
 one to measure the areas of indicator diagrams correctly, but the 
 
 FIG. 13. 
 
 mean pressures may at once be read off, without the aid of in- 
 tricate mathematical calculations. The action of the plan- 
 imeter is quite simple, as will be readily understood by Fig. 13. 
 It consists only of two arms, hinged together, and a wheel. 
 At the end of each arm there is a sharp point. In using the 
 instrument one of these points is stuck lightly through the 
 paper, and the other is moved along the line drawn by the indi- 
 cator pencil, until it has passed entirely around and returned to 
 the point it started from. Meanwhile the wheel rolls about on 
 the paper. On the edge of the wheel there are numbers, and 
 opposite the upper part of it there is a pointer or zero mark. 
 When the instrument is in position and the engineer is ready to
 
 IO8 THE STEAM-ENGINE AND THE INDICATOR. 
 
 move the point along the line, as already described, he reads 
 the number opposite the pointer. He reads it again when the 
 pointer comes back to the starting place, and the difference be- 
 tween the two readings is the area of the card in inches. He 
 next measures the length of the card by means of a machinist's 
 scale, graduated say to hundredths, and he divides the area, as 
 found by the planimeter, by the length, as found by the scale. 
 The result is the average height of the card. Multiplying by 
 the scale of the card gives the average effective pressure. 
 
 The planimeter is one of the most wonderful instruments yet 
 invented. It will find the area of the most irregular card just 
 as easily and just as exactly as it will find the area of a square. 
 It is so very simple in construction that it was announced, when 
 it was first introduced, that there was something mysterious be- 
 hind it. This is not so, however, for its action can be fully 
 explained, though not without the use of algebra and higher 
 mathematics. 
 
 Directions for Using the Planimeter. 
 
 To find the area of a diagram, place the instrument on the 
 drawing (whether a plan or indicator diagram), in about the 
 position shown, that is to say, so as to allow perfect freedom of 
 motion in every direction in which it is necessary to move; sink 
 the needle-point Pa. little so that the needle will remain fixed, 
 and place the weight upon it. 
 
 Then place the point of the tracer, F, upon any given point, 
 say <2, of the outline of the figure to be measured, and either 
 adjust the wheels to their respective zeros or take a first reading 
 where they happen to stand; follow the outline of the figure 
 carefully with the tracer-point, moving in the direction taken 
 by the hands of a watch, returning to the starting point, Q; 
 then the index must be read. 
 
 Having started from zero, suppose we find that the highest 
 figure on the roller wheel, D, that has passed by zero on the 
 vernier is 2, which in this style of planimeter represents units, 
 and we find the number of intermediate graduations that have 
 also passed zero on the vernier to be 4, then we find the number 
 of the graduation on the vernier, E, which exactly coincides 
 with a graduation on the wheel, to be 8; then we have 2.48
 
 HORSE-POWER. 109 
 
 square inches as the area of drawing. If we start with an old 
 reading, instead of from zero, the first reading should be de- 
 ducted from the second reading, then the difference represents 
 the area of the drawing. If the amount of the first reading 
 should exceed that of the second, 10 should be added to the 
 second reading before subtracting. If the figure is drawn to a 
 scale, multiply the result by the square of the scale for the actual 
 contents of the surface which the drawing represents. If it is 
 an indicator diagram, and we have found the areas, as per above 
 directions, to be 2.48, divide this by the length of the diagram, 
 which we will assume to be 4 inches, and we have 0.62 inch as 
 the average height; multiply this by the scale or number of the 
 spring, which in this instance we will call 40, and we have 24.8 
 pounds as the average pressure per square inch on the piston. 
 FIG. 14. 
 
 When a set of diagrams are taken, which are of the same 
 length, it is only necessary to multiply the area in square inches 
 with a co-efficient obtained by dividing the "scale" with the 
 length in inches. 
 
 For instance: 
 
 Area = 3.80 square inches 
 Length of diagram = 4. inches 
 Scale = 30. pounds per square inch 
 
 3- = 7.5 co-efficient 
 
 3.80 X 7.5 = 28.5 pounds per square inch. 
 
 In calculating the power from diagrams of condensing 
 engines, it: is usual to measure the area above and below the 
 atmospheric lines separately. This method gives the value of 
 the average vacuum obtained, and thus indicates the extent to 
 which the back pressure is reduced below atmospheric pressure.
 
 no 
 
 THE STEAM-ENGINE AND THE INDICATOR. 
 
 In measuring the indicator diagram it is of no consequence 
 what the character of it may be, whether most wasteful, like the 
 Figs. 14 and 15, or most economical, like Fig. 16. 
 
 FIG. 15. 
 
 For, ascertaining the power exerted, we have merely to 
 measure its included area, and so get the mean-pressure on one 
 square inch during the stroke, which this area represents. This 
 pressure being multiplied into the number of square inches, we 
 have the total number of pounds of force exerted. This force 
 
 FIG. 1 6. 
 
 is acting through the distance traveled by the piston. We 
 multiply it by the distance in feet' through which the piston 
 travels in one minute, and the product is the number of foot-
 
 HORSE-POWER. 
 
 Ill 
 
 pounds of force exerted in one minute. This divided by 33,000, 
 gives the number of horse-power. It is to be observed, that in 
 this calculation force and distance are treated as convertible. 
 However extremely unequal, as in Fig. 17, the pressures may 
 be at different points of the stroke, these are all reduced to an 
 average pressure, which is conceived to be uniformly exerted 
 throughout the stroke. Then, finally, all the power exerted in 
 a minute is conceived as a certain number of pounds of force 
 exerted through one foot. 
 
 The above calculation gives what is called "the indicated 
 
 FIG. 17. 
 
 power" of the engine not the gross power exerted by the 
 engine. The included area of the diagram represents only the 
 difference between the opposing forces which act to produce and 
 to resist the motion of the piston. The force of the steam must 
 in all cases be first applied to overcome what is called the back 
 pressure. In a non-condensing engine this must be at least the 
 pressure of the atmosphere. It is always, in fact, more than 
 this, by the amount of force that is required to expel the ex- 
 haust steam through the port, passages, and pipe, against the 
 resistance of the atmosphere. Sometimes the excess of back 
 pressure above that of the atmosphere is scarcely preceptible, as
 
 112 THE STEAM-ENGINE AND THE INDICATOR. 
 
 in diagram Fig. 18. In badly constructed engines, on the other 
 hand, the force required for this purpose may be very great, as 
 in diagram Figures 14 and 15, which are almost too bad in this 
 respect to be credited, but the writer has the originals in his 
 possession. The usefulness of the indicator in revealing defects 
 of this nature can hardly be estimated. Locomotives were run- 
 ning before the introduction of indicators, for high speeds some 
 twenty years ago, with a back pressure of ten to twenty pounds 
 above that of the atmosphere. The office of the condenser and 
 air-pump is to remove the back pressure, or resistance of the 
 atmosphere, from the piston of the engine to the piston or 
 
 FIG, 1 8. 
 
 plunger of the air-pump; by which means indeed, it is, to the 
 extent of the vacuum obtained, got rid of altogether, since the 
 atmosphere exerts there the same force to produce motion in 
 one direction that it does to oppose it in the contrary one. But 
 in all cases it is only the net power exerted, after deducting 
 that which is necessary to overcome the back pressure, as rep- 
 resented in the included area of the diagram. 
 
 A diagram from a condensing or "low pressure" engine 
 differs from one produced by a non-condensing or "high-pres- 
 sure" engine, from the fact that in the former the line of back 
 pressure, instead of being a little above atmospheric pressure, 
 approaches more or less to that of perfect vacuum.
 
 HORSE-POWER. 113 
 
 In calculating the power from diagrams of condensing or 
 "low-pressure" engines, it is usual to measure the area above 
 and below the atmospheric line separately. This method gives 
 the value of the average vacuum obtained, and thus indicates 
 the extent to which the back pressure is reduced below atmo- 
 spheric pressure; see diagram, Figure 19. 
 
 FIG. 19. 
 
 
 Scale: 16 pounds equal i inch. 
 
 In this the average mean pressure due to the steam was 21 + 
 21 + 6 = 48 pounds, which divided by 10 (the number of 
 divisions on the card) equals 4.8 pounds; and the average 
 vacuum realized was 12 + 12 + 12 + n + 9 + 6.5 + 5 + 4.5 + 
 4 -f 2.5 = 78.5 pounds, which divided by 10 equals 7.85 pounds; 
 showing that the power realized in this case by removing the 
 resistance of the atmosphere was about sixty per cent, of that 
 shown by the indicator, thus: 
 
 _ 6o per cent 
 
 In well constructed engines with an early cut-off, the expan- 
 sion curve, eg, (diagram 19,) will often cross the atmospheric 
 line, A D, before the piston has moved half the length of the 
 cylinder. In such cases as this the mean pressure represented
 
 114 TH E STEAM-ENGINE AND THE INDICATOR. 
 
 by the area above the atmospheric line, A D, will be less than 
 below it, which difference is due to the reduced back pressure 
 by reason of the comparative vacuum in the condenser. The 
 above diagram, Figure 19, indicates a large amount of expan- 
 sion. 
 
 Indicated Horse-power. 
 
 The indicated horse-power is the power developed by the 
 steam on the piston of the engine, without any deduction for 
 friction. The indicated horse-power is calculated from the 
 diagram or cards taken by the application of the indicator to the 
 steam engine cylinder. It is the total unbalanced power of an 
 engine employed in overcoming the combined resistance of 
 friction and the load. 
 
 Effective Horse-power. 
 
 The effective horse-power is the actual and available horse- 
 power delivered to the belt or gearing, and is always less than 
 the indicated, from the fact that the engine itself absorbs power, 
 due to the friction of its moving parts. 
 
 Engine Friction. 
 
 The power absorbed in driving an engine against its own 
 friction is a most variable quantity. With a good and well 
 constructed engine having ample bearing surfaces, efficient 
 means of lubricating them, and valves nearly balanced without 
 over-complication, the friction may not exceed ten per cent, of 
 the indicated power. But in badly constructed engines the 
 friction may be nearer fifty per cent. In the case of an engine 
 having ordinary unbalanced slide valves, it is probable that 
 quite one-third of the whole frictional resistance is due to the 
 valve cut-off. The heat due to the internal engine friction 
 that is to say, the friction of the valves and piston is imparted 
 to the steam, and either the whole or greater part of it is carried 
 to the condenser or atmosphere with the exhaust steam. 
 
 The power absorbed in overcoming friction is not only wasted, 
 but it is wasted in wearing out the engine. 
 
 In the diagram, Figure n, the calculation gave what is called 
 the indicated power, that is, the effective available power of the
 
 HORSE-POWER. 115 
 
 engine. It does not show the gross or whole power of the 
 engine. This gross power is reduced to effective motive power 
 in three ways, namely: 
 
 First. In expelling the steam left in the cylinder at the end 
 of the stroke, the expelled steam carrying its heat with it to the 
 atmosphere in a non-condensing or "high-pressure" engine, 
 and to the condenser in a condensing or "low pressure " engine. 
 
 Second. In compressing the steam in the cylinder after the 
 exhaust-port is closed, but as this steam is again used after com- 
 pression, the power used in compressing it is not necessarily 
 wholly wasted. 
 
 Third. In overcoming the friction of the moving parts of the 
 machinery, including, in locomotives, the friction on rails, and, 
 in stationary engines, the friction of the belt or gearing. 
 
 The effective, available motive power will therefore vary in 
 proportion to the power lost through these reducing causes. 
 The less power required to expel and compress the steam left in 
 the cylinder and to overcome the friction, the greater will be 
 the effective motive power, and vice versa. 
 
 In calculating this power, however, from a diagram, only the 
 first and second of these causes are, or can be, considered. 
 
 The piston of an engine is always acted upon by two oppos- 
 ing forces, one propelling and the other repelling, and the 
 difference between them is what in practice is called the effective 
 motive force or power. 
 
 The propelling force must, of course, in all cases be suffi- 
 cient at least to overcome the repelling force or back-pressure. 
 This back- pressure, as will presently be seen, is always greater 
 in non-condensing or "high-pressure" engines, than in con- 
 densing or "low-pressure" engines. In the former the pro- 
 pelling steam left in the cylinder at the end of the stroke (that 
 is, the exhaust steam) escapes, or is expelled into the air; in 
 the latter, into the condenser. In the former the back-pressure 
 must necessarily be at least the pressure of the atmosphere, 
 which averages about fourteen pounds to the square inch (see 
 Fig. n), but it is always greater than this, because of the fric- 
 tion of the exhaust steam in the ports and pipe connections, and 
 in badly constructed engines it is much greater. In condens- 
 ing, or "low-pressure" engines, the back-pressure should
 
 Il6 THE STEAM-ENGINE AND THE INDICATOR. 
 
 always be less than the pressure of the atmosphere, depending 
 upon the approximation to vacuum obtained in the condenser. 
 
 In the diagram, Fig. 20, taken from a non-condensing engine, 
 it will be seen that the back-pressure line, gdh,\s considerably 
 above the atmospheric line, A D, indicating excessive back- 
 pressure. 
 
 Excessive back-pressure in a non-condensing engine is caused 
 by, or results from, too great impediment to the escape of the 
 exhaust steam, and in condensing engines to imperfect vacuum 
 in the condenser. The value of the indicator in revealing de- 
 fects of this kind cannot be overestimated. 
 
 FIG. 20. 
 
 -er 
 
 The difference between a non-condensing and a condensing 
 engine is, as has been seen, that in the former the exhaust 
 steam escapes or is expelled more or less directly according to 
 the construction of the port-passages and pipe connections into 
 the air, and in the latter into the condenser. 
 
 In the former the back-pressure is the pressure of the atmos- 
 phere increased more or less as the escape of the exhaust steam 
 is more or less impeded. In the latter the back-pressure de- 
 pends chiefly upon the pressure of the exhaust steam, or, in 
 other words, the degree of vacuum, in the condenser.
 
 HORSE-POWER. 117 
 
 A perfect vacuum cannot in practice be had but an average 
 of about 26 inches or 13 pounds is usually obtained by the gage; 
 diagrams generally show from 3 to 4 pounds less. The approxi- 
 mation to a vacuum, and corresponding diminution of back- 
 pressure, are effected in three ways, namely: 
 
 First. The temperature of the condensing water. 
 
 Second. The pressure of the atmosphere. 
 
 Third. The friction of the exhaust-pipes and ports. 
 
 First. If the temperature should be 32 degrees Fahrenheit, 
 the pressure would be only 0.085 pounds to the square inch, 
 and the vacuum as nearly perfect as is obtainable. The con- 
 densing water is, however, usually taken at 40 to 80 degrees, 
 and leaves the condenser at from 90 to 120 degrees, making the 
 temperature in the condenser generally about 100 degrees, 
 which would give a back-pressure from this cause alone of 
 about one pound to the square inch. 
 
 Second. If the barometer stands at only 28 inches, 13. 7 pounds 
 would be a perfect vacuum; 30 inches of mercury being equiv- 
 alent to 14.7 pounds; and if the water in the condenser be at a 
 temperature of 130 degrees, its vapor will form a resistance of 
 2.21 pounds; therefore the lowest attainable vacuum would be 
 but 13.7 2.21 = 11.49 pounds. Whereas, if the barometer 
 stood at 31 inches, a perfect vacuum would be 15.2; and if the 
 water was but 100 degrees its vapor would give a resistance of 
 only 0.9 pound, and consequently the highest attainable 
 vacuum would be 15.2 0.9 = 14.3 pounds, making a differ- 
 ence of 2.81, or a gain of twenty per cent. 
 
 Third. The friction of the exhaust-pipe and ports will be ex- 
 cessive, if they are too small, to the same extent as in the case 
 of non-condensing engines. 
 
 The water used for steam engine purposes invariably contains 
 more or less air, which if allowed to accumulate would grad- 
 ually destroy the required vacuum. It is necessary, therefore, 
 to draw off this air as well as the water, and this is done by 
 means of an "air pump" worked by the engine; and, of course, 
 the power required to do this, although needfully expended, is 
 so much power to be deducted from the given power, reducing 
 the efficient motive power of the engine. The power thus ex- 
 pended is usually equivalent to from one-half to one pound
 
 n8 
 
 THE STEAM-ENGINE AND THE INDICATOR. 
 
 pressure. But it is frequently necessary to raise the condensing 
 water from a lower level to the line of the condenser, and in 
 that case the power required to do this work is also power to be 
 deducted from the gross power, also reducing the efficient mo- 
 tive power of the engine. In all cases it is only the net motive 
 power, after deducting the power needed to overcome the back- 
 pressure, that is represented in the area of the diagram. 
 
 The pressure of the atmosphere is usually taken as 15 pounds, 
 which is too high, being correct only when the barometer 
 stands at 30.54 inches a most unusual occurrence; but the 
 error is unimportant, and it is very convenient to avoid the use 
 of a fraction, and to say that 30 pounds, 45 pounds, 60 pounds, 
 and so on, represent 2, 3, 4, 5, 6 atmospheres of pressure. 
 
 Mercury in Pounds, and Vacuum in Inches. 
 TABLE NO. 4. 
 
 Inches of 
 Mercury. 
 
 Pounds. 
 
 Inches of 
 Mercury. 
 
 Pounds. 
 
 2.037 
 4.074 
 6.IH 
 8.148 
 10.189 
 12.226 
 14-263 
 
 I 
 
 2 
 
 3 
 4 
 5 
 6 
 
 7 
 
 16.300 
 18.337 
 20.374 
 22.411 
 24.448 
 26.485 
 28.522 
 
 8 
 
 9 
 10 
 ii 
 
 12 
 13 
 
 14 
 
 The principal object of knowing the exact pressure of the 
 atmosphere is to ascertain the duty performed by the condenser 
 and the air pump. The temperature of discharge being known, 
 the pressure of vapor inseparable from that temperature is also 
 known (see Nystrom's Pocket Book, page 400). and this being 
 deducted from the actual pressure of the atmosphere, the re- 
 mainder is the vacuum in which the water would boil. The 
 power of the air-pump is shown in the closeness with which the 
 vacuum approaches this point. 
 
 The vacuum shown by the indicator will generally vary from 
 that shown by the vacuum gage, when it is constructed with a 
 glass tube, heremetically sealed at the top; for such gages are 
 designed to show the variation from a perfect vacuum without 
 reference to the weight of the atmosphere; but the vacuum 
 shown by an indicator is affected by all its variations.
 
 HORSE-POWER. 1 19 
 
 Vacuum Gage. 
 
 The common gage for indicating the vacuum of a condenser, 
 consists of an inverted syphon, or \j shaped tube, the lower 
 part of which contains mercury, and whose legs have a scale at- 
 tached to them, divided into divisions 1.018 inches apart, and 
 indicate pounds pressure, for the reason that the descent of 
 1.018 inch in one leg, causes a rise of 1.018 inch in the other, 
 making a difference in the level of the mercury of 2.036 inches, 
 which corresponds to one pound. One leg, by means of a con- 
 nection, communicates with the condenser; the other is open to 
 the air. The mercury stands lowest in that leg in which the 
 pressure on its upper surface is most intense; and the difference 
 of level of the mercury in the two legs indicates the difference 
 between the pressure in the condenser, and the atmospheric 
 pressure. Mercurial vacuum gages are made, which indicate 
 directly the absolute pressure within the condenser, by being 
 constructed like a barometer, having the leg containing the 
 mercurial column that balances the pressure to be measured her- 
 metically closed at the top, with vacuum above the mercury, 
 produced in the usual way, by inverting the tube and boiling 
 the mercury in it. It is necessary to lay out the scale accu- 
 rately and have it exactly vertical. 
 
 On diagrams representing condensing engines, the line of 
 perfect vacuum should be drawn at the bottom, and the line of 
 the boiler pressure, as shown by the steam gage, at the top. 
 The line of perfect vacuum varies in its distance from the 
 atmospheric line, or, more correctly, the latter varies in its 
 distance from the former, according to the pressure of the atmos- 
 phere, as shown by the barometer, from 13.72 pounds on the 
 square inch when the mercury stands at 28 inches, to 15 pounds 
 when it stands at 30.6 inches, and it should be drawn according 
 to the fact, if this can be ascertained. The engineer should 
 always have a good aneroid at command. 
 
 The principal object of knowing the exact pressure of the 
 atmosphere is to ascertain the duty performed by the condenser 
 and air-pump. The temperature of the discharge being known, 
 the pressure of vapor inseparable from the temperature is also 
 known, and this being deducted from the actual pressure of the 
 atmosphere, the remainder is the total attainable vacuum at 
 that temperature.
 
 120 THE STEAM-ENGINE AND THE INDICATOR. 
 
 As before stated, the areas of the diagram above and below 
 the atmospheric line, are usually calculated separately, to ascer- 
 tain how effectually the resistance of the atmosphere is removed 
 from the non-acting side of the piston, by those parts of the 
 engine whose function this is. In case of engines working very 
 expansively, however, the expansion curve crosses the atmos- 
 pheric line, and sometimes at an early point of the stroke, as in 
 diagram, Fig. 19. In such cases, the whole space between the 
 atmospheric line and the line of counter-pressure should be 
 credited to the condenser and air-pump; not, of course, to be 
 considered in estimating the power exerted, but for ascertaining 
 the degree of economy in the consumption of steam, which de- 
 pends greatly on the amount of vacuum maintained. 
 
 The lines having been accurately drawn, as above directed, 
 ascertain, by careful measurement with the scale or planimeter, 
 the mean pressure in each division, between the atmospheric 
 line and the upper outline of the diagram, until this crosses 
 the former, if it does so. Add these together, and point off one 
 place of decimals, or divide their sum by the number of 
 divisions, if there are more than ten, and the quotient will be 
 the mean pressure above the atmosphere during the stroke. 
 Then repeat the process for the area between the atmospheric 
 line, or the expansion curve, after it has crossed this line, and 
 the lower outline of the diagram. Add the two mean pressures 
 to ascertain together which will give the mean average pressure 
 per square inch. Then find the number of square inches con- 
 tained on the surface of the piston; this latter multiplied by the 
 average pressure as found above, this product by the mean 
 velocity of the piston in feet per minute, and divided by 33,000, 
 and the quotient will be the gross indicated horse-power ex- 
 erted; or the power represented by the two areas of the diagram, 
 above and below the atmospheric line, may be calculated sep- 
 arately. 
 
 The strictly accurate mode of measurement is, to measure the 
 pressure of steam from the line of perfect vacuum, when the 
 line of 15 pounds pressure will come a little above the atmos- 
 pheric line, but it is more convenient, and answers all the pur- 
 poses of the diagram better, to measure each way from the latter. 
 
 The space above the steam line and between this and the line
 
 HORSE-POWER. 121 
 
 of boiler pressure, shows how much the pressure is reduced in the 
 cylinder by throttling, or by the insufficient area of the ports, 
 proper allowance being made for the difference of pressure nec- 
 essary to give the required motion to the steam in the pipe; 
 whilst the space between the line of counter-pressure and the 
 line of perfect vacuum shows the amount of resistance to the 
 motion of the piston. 
 
 On diagrams for non-condensing engines, the line of boiler 
 pressure should also be drawn at the top, and it is well to draw 
 the line of perfect vacuum also, that the engineer may be able 
 to see at a glance the quantity of steam consumed, and to com- 
 pare with it the amount of work done. It is not possible that 
 
 FIG. 21. 
 
 the back pressure resisting the motion of the piston shall be 
 less than the pressure of the atmosphere, but it may be a great 
 deal more; and very frequently in non-condensing engines, the 
 line of resistance is as much as 2 or 3 pounds above the atmos- 
 pheric line, though it is quite possible to avoid this excess 
 altogether, as is shown in diagram, Fig. 18, page 112. 
 
 The mean pressure is ascertained in the manner already 
 directed for obtaining the pressure above the atmospheric line 
 in condensing engines, and the power is calculated in the same 
 way. 
 
 In the same manner, on stationary engines, the power shown 
 by the frictional diagrams can be calculated, and also the va-
 
 122 
 
 THE STEAM-ENGINE AND THE INDICATOR. 
 
 rious powers shown by diagrams, Figs. 17 and 21, taken when 
 the shafting only was being driven, and when greater or less 
 proportions of the whole resistance are being overcome; whilst 
 on vessels, the effects of different depths of immersion can be 
 determined. 
 
 So also the power required in non-condensing engines, to 
 overcome the resistance of the atmosphere, is readily ascertained. 
 
 It often happens, in non-condensing engines working expan- 
 sively, that the expansion curve falls below the atmospheric 
 
 FIG. 22. 
 
 line, as illustrated in Fig. 17, and the following Fig. 21. In 
 such cases the enclosed area below the atmospheric line must 
 be deducted from that above this line, to give the power really 
 exerted; for it is obvious that daring the latter portion of the 
 stroke, while the expansion curve ran below the atmospheric 
 line, the pressure of steam was insufficient to overcome the re- 
 sistance of the atmosphere, which was then exerted, in that 
 degree, to retard the motion, and this deficiency must be made 
 good during the earlier portion of the stroke. 
 
 Generally, engines will give the same figure at each revolu-
 
 HORSE-POWER. 
 
 123 
 
 tion, the pencil retracing the same line so long as the resistance 
 continues the same; but sometimes this is not the case, as in 
 the engine from which the diagram Fig. 22 was taken, where 
 are shown three distinct expansion curves. In such cases, care 
 must be taken to obtain the average diagram. Also, in com- 
 paring the pressures required to overcome different resistances, 
 it is essential that the speed of the engine in each case be the 
 same a requirement often disregarded.
 
 CHAPTER VIII. 
 
 DIAGRAMS SHOWING THE ACTION OF STEAM IN A STEAM- 
 ENGINE CYLINDER. 
 
 SOME of the disturbing causes on diagrams of a steam-engine 
 which make the real differ from the ideal form of the diagram, 
 have already been considered incidentally. At present the 
 more important and usual of these deviations, are to be classed 
 and considered in detail. 
 
 These causes affect the power of the engine, as well as the 
 character and shape of the diagram. 
 
 The indicator diagram is, of course, the key to the action of 
 the steam in the cylinder. A part of the work performed by 
 the steam is spent in overcoming the friction of the engine 
 itself, and consequently, the efficiency of the engine is most 
 fairly tested by the amount of external work absolutely per- 
 formed against a brake or otherwise. 
 
 Where the efficiency of the steam alone is concerned, how- 
 ever, the diagram is the only true criterion; and it will be nec- 
 essary to deal with its theory carefully to prevent misunder- 
 standings, which are frequent in practice. 
 
 The Action of Steam in the Cylinder. 
 
 The action of steam in any steam-engine cylinder is best 
 understood from a diagram representing the varying pressures 
 and volumes through the stroke. 
 
 An Ideal Diagram. 
 
 Such a diagram is usually obtained by an indicator applied 
 to the cylinder, and in such case the pressures shown are 
 actually those of the steam in use. For purposes of comparison 
 and calculation, however, it is more convenient to construct an 
 ideal diagram, as nearly as possible, such as would be given by 
 an indicator applied to an engine as nearly perfect as practicable, 
 working under the same conditions. Such a diagram is shown 
 
 (124)
 
 INDICATOR DIAGRAMS. 
 
 125 
 
 in Fig. 23, where horizontal distances represent volume and 
 vertical distances pressure. 
 
 The several lines on the ideal diagram will be designated 
 here, reference being had to this diagram. 
 
 The base lines of the theoretical diagrams are as follows: 
 
 The Atmospheric Line. 
 
 When the atmosphere has free access to both sides of the pis- 
 ton of the indicator before steam is admitted, a straight line, A 
 D, will be drawn by applying the pencil to the moving paper; 
 this line is called the line of atmospheric pressure, or zero, on 
 the steam gage. From this line we measure pressure for non- 
 condensing engines. 
 
 FIG. 23. 
 
 The atmospheric line should not be taken until after the rest 
 of the diagram has been completed; because as the parts become 
 warm by the steam, slight variations occur in its position, de- 
 pending principally on the alteration in the force of the spring; 
 and since this line serves as the origin from which the pressures 
 are dated, it is necessary to have it laid down as correctly as 
 possible. 
 
 The Line of Perfect Vacuum. 
 
 The line FFrepresents it. This line cannot be drawn by 
 the indicator, but must be drawn by hand, parallel with the
 
 126 THE STEAM-ENGINE AND THE INDICATOR. 
 
 atmospheric line, and at the proper distance below it to repre- 
 sent the pressure of the atmosphere, as shown by the barometer, 
 according to the scale of the indicator diagram. When the 
 actual pressure is not known, it is to be assumed at 15 (14.7 
 pounds exact) on the square inch, corresponding almost exactly 
 with 30 inches of mercury, which is about the average pressure 
 at the level of the sea. The barometric column falls one one- 
 hundredth of its height for every two hundred and sixty-two 
 feet of elevation above the sea level. 
 
 The Line of Boiler Pressure. 
 
 This line is represented by the letters B C, and is also drawn 
 by hand, parallel with the atmospheric line, and at the proper 
 distance above it to indicate the steam pressure per square inch, 
 as shown by a correct steam gage, measured off by the scale of 
 the indicator diagram. It can be drawn by the indicator 
 attached to the cylinder only when the engine is at rest, and 
 while an equilibrium of pressure is established between the 
 boiler and cylinder. It is generally somewhat higher than the 
 initial pressure in the cylinder. 
 
 The Clearance Line. 
 
 This line is represented by B V, and is at right angles to the 
 atmospheric line A D, and at such distance from k i m and n, 
 that the included space, B A V, n m and , correctly represents 
 the clearance. 
 
 This clearance is the cubical contents of the steam-port pas- 
 sages and the space between the piston and the end of the 
 cylinder, or head, to which it is nearest at the end or beginning 
 of a stroke, supposing them, when added together, to be at each 
 end one-twelfth of the whole cubical contents of the cylinder 
 for one stroke of the piston, then the distance A m, would be 
 made one-twelfth (rV) of m D. In 'the diagram, Figure 23, one- 
 twentieth (zV) has been taken, so that the line A m, is one- 
 twentieth (uV) of the length of m D. It is necessary to take 
 these cubical contents into account, for the passages and clear- 
 ance must always be filled with steam at each stroke, which is 
 compressed and expands just precisely the same as the rest of 
 the steam in the cylinder does after the steam has been cut off.
 
 INDICATOR DIAGRAMS. 127 
 
 It is necessary to draw this line and to add this space to the in- 
 dicator diagram, whenever the theoretical curve is constructed 
 to compare with the actual curve traced by the indicator, and 
 must be reckoned as part of the diagram in calculating the 
 average pressure, and in producing the theoretic curve, or line 
 of perfect expansion. The clearance is, however, rarely given, 
 and it varies in different engines from one to twenty per cent, 
 of the space swept through by the piston in one stroke. If we 
 have the drawings of the engine we can calculate it; if we know 
 the style of engine we can approximate it. 
 
 The best method, providing the piston is tight, is as follows: 
 Put the engine on the center, remove the valve chest cover, 
 uncover the steam-port on the end where the piston is, fill the 
 steam passage and piston clearance full with water up level with 
 the valve seat; allow it to remain a few minutes, and if it main- 
 tains its level it is evident the piston is tight; then draw off the 
 water, measure or weigh it, reduce it to cubic inches, and we 
 have it exactly. The number of cubic inches of clearance di- 
 vided by the cubic inches of space swept through by the piston 
 in one stroke gives the ratio of cylinder capacity to clearance. 
 This matter will be more fully illustrated hereafter. 
 
 Division of the Outline Drawn by the Instrument During 
 a Revolution of the Engine. 
 
 The diagram, Fig. 23, shows all the lines that would be 
 traced by the pencil of the indicator during one revolution of 
 the engine, assuming the action of the steam to be nearly theo- 
 retically correct. In order that the student may better under- 
 stand the subject matter, the following names have been given 
 to the lines represented as follows: 
 
 The line from / to k, the admission line. 
 
 The line from k to e, the steam line. 
 
 The line from e to g, the expansion line. 
 
 The line from g to d, the exhaust line. 
 
 The line from d to h, the back pressure, or line of counter pressure. 
 
 The line from h to i, the compression line. 
 
 Of these divisions, the first four are drawn during the forward 
 stroke of the piston and until it is at, or very close to, the 
 termination of its stroke, and the last two are drawn during the 
 return stroke.
 
 128 THE STEAM-ENGINE AND THE INDICATOR. 
 
 Admission Line. 
 
 The admission line, i k, shows the rise of pressure due to the 
 admission of steam to the cylinder. This line is generally very 
 nearly vertical, and when this is the case, it shows that steam 
 of nearly boiler pressure is had at the commencement of the 
 stroke while the piston is nearly stationary. Should this line 
 incline forward, as shown in Figure 15, or at k in Figs. 17 
 and 29, curve with the steam line the reverse as indicated; or 
 should this line continue vertically beyond, and then suddenly 
 drop to the level of the steam line, Fig. 16, it signifies that the 
 steam is wire-drawn, and cannot keep up the full pressure as 
 the piston starts forward; but should this line, after projecting 
 above, be suddenly depressed below the level of the steam line, 
 vibrating back and forth one or more times on the latter line 
 with acute angles of return, it may be attributed to the momen- 
 tum of the reciprocating parts of the indicator while running at 
 very high speeds: this will be hereafter more fully explained. 
 
 The Steam Line. 
 
 The steam line, k e, is traced while the steam is being ad- 
 mitted to the cylinder, and should be nearly parallel to B C, 
 and is invariably several pounds pressure below it; this loss in 
 pressure occurs from radiation and friction in the pipes from the 
 boiler to the cylinder. This line also represents the initial 
 pressure acting on the piston up to the point of cut-off, and 
 should be of unvarying height to show that full boiler pressure 
 is maintained. It also shows at its termination the point at 
 which the valve closes, or steam is cut off. 
 
 To maintain a proper steam pressure in the cylinder depends 
 of course, in the first place, upon the amount of steam-port area. 
 It will be noticed in diagram, Fig. n, taken from a Corliss 
 engine, that the piston obtained nearly the full boiler pressure 
 at the very commencement of th6 stroke the initial cylinder 
 pressure was 97 per cent, of the pressure in the boiler; while in 
 the diagram, Fig. 22 (fitted with the ordinary slide-valve and 
 the steam controlled or regulated by a valve in the steam pipe), 
 the maximum cylinder pressure reached but 66 per cent, of the 
 boiler pressure, notwithstanding the slower speed of the engine, 
 the former making ninety, and the latter but forty revolutions 
 per minute.
 
 INDICATOR DIAGRAMS. 129 
 
 An important consideration in connection with the admission 
 of steam is that the maximum cylinder pressure be fully main- 
 tained until the closing of the valve; in other words, that the 
 steam line traced by the indicator should, as much as possible, 
 run in a horizontal direction. (See Figs. 9, 10, n, 18, and 23.) 
 To effect this, it is necessary to have the steam-port fully un- 
 covered early in the stroke, so that the steam can be rapidly 
 introduced into the cylinder. Referring to the above mentioned 
 diagrams, we find that the steam-line is kept well up to the 
 boiler pressure, and this pressure is nearly fully maintained 
 until the point of cut-off is reached. If we take into considera- 
 tion the small amount of lead obtained in these cases, we must 
 attribute the comparative good results solely to the employment 
 of Corliss and Buckeye valves, which permit with a smaller 
 amount of angular advance of the eccentric a very rapid and 
 good introduction of steam. In locomotive engines the dia- 
 grams taken with a high rate of expansion, more particularly at 
 high speeds, the steam line generally falls more or less during 
 the period of admission, indicating that the steam-port opening 
 
 is too small. 
 
 The Point of Cut-off. 
 
 This takes place at e. In the theoretical diagram the corner 
 is abrupt, but in practice it is more or less rounded. The dia- 
 gram does not always show clearly the exact point where the 
 convex curve of the rounded corner changes to the concave 
 curve of the expansion line, but the point of cut-off is properly 
 located at the point where the direction of curvature changes 
 from convex to concave. 
 
 The Expansion Curve. 
 
 This is represented by the line e g, and results from a fall 
 of pressure due to the expansion of the steam remaining in the 
 cylinder after cut-off takes place. The actual curve, as drawn 
 by the indicator, will be above the theoretical curve laid down 
 by the law of Boyle and Mariotte hereafter explained. That 
 is to say, the pressure is inversely as the volume, and the 
 curve which expresses the pressure for every point of the stroke 
 is an equilateral hyperbola. In all indicator diagrams, a mate- 
 rial difference will be noticed between the true ratio of expan- 
 9
 
 130 THE STKAM-ENGINE AND THE INDICATOR. 
 
 sion and the corresponding pressures; the amount of departure 
 of the actual pressures from the theoretical curve bearing, how- 
 ever, a certain relation to the degree of expansion, as will be 
 seen hereafter. 
 
 There are various causes which produce this action during 
 the period of expansion, but their precise influence is more or 
 less difficult to ascertain. In the first place, leakage at the 
 valves or past the piston is, of course, calculated to alter the 
 actual expansion curve. 
 
 The effect of leakage, if such occurs, is generally easily de- 
 tected by the irregular form of the indicator curves. The main 
 cause of the peculiar action of the expanding steam is, according 
 to a large number of experiments made, the heat given off by 
 the cylinder to the contained steam after its communication 
 with the boiler has been cut off. This condition is facilitated 
 by the presence of a certain quantity of water, which at the 
 commencement of the expansion has the temperature of the live 
 steam; but as the pressure is reduced in the cylinder this water 
 will be instantaneously evaporated, and thus abstract from the 
 cylinder a certain amount of heat. The heat absorbed with 
 such rapidity is sufficient to raise the pressure considerably 
 above that which would have existed had no condensation and 
 re-evaporation taken place. The amount of heat which can be 
 absorbed depends, of course, upon the difference of temperatures 
 between the steam and the metal. 
 
 On the other hand, the mean temperature of the cylinder is 
 influenced by the amount of protection against radiation and 
 conduction of heat from the cylinder, by the amount of "throt- 
 tling" from the boiler to the cylinder, by the extent to which 
 expansion has been carried, and by the speed in revolutions per 
 minute. 
 
 When the communication between the boiler and the piston 
 is o _n, the cylinder will acquir a temperature practically the 
 same as that of the boiler pressure, and if the cylinder contained 
 nothing but dry, or superheated steam, this temperature would 
 probably be maintained for the greater part of the stroke; but 
 owing to a certain amount of water which has been deposited 
 in the cylinder, and which is re-evaporated at the expen e of 
 heat imparted to the cylinder, this latter will become materially 
 cooled by the time the piston has reached the end of the stroke.
 
 INDICATOR DIAGRAMS. 13! 
 
 For these considerations the relative effect of the various de- 
 grees of expansion and of speed will readily be appreciated. As 
 the degree of expansion is increased the quantity of water con- 
 verted into steam becomes also greater, necessitating, however, 
 a larger condensation of high pressure steam during admission; 
 and the longer the duration of the stroke in other words, the 
 slower the engine is running the more heat will be absorbed 
 from the cylinder by the conversion of this water into steam. 
 
 The Point of Release or Opening of the Exhaust-port. 
 
 This is at g, Fig. 23. To provide a rapid egress for the 
 exhaust steam, and in order that its pressure may be as nearly 
 as possible at a minimum, after the work in the cylinder has 
 been performed, it is necessary that the exhaust-port should be 
 opened before the piston reaches the end of its stroke. The 
 proper amount of this pre-release depends, of course, upon the 
 velocity of the piston and the quantity of steam to be discharged, 
 or the grade of expansion. If, on the contrary, the steam be 
 confined until the last instant, the back pressure at the com- 
 mencement of the return stroke will be considerably increased, 
 or in proportion to the 'period of admission. The deficiency of 
 early release produces in the indicator-curves a sharp corner at 
 g, at the end of the stroke, as shown in diagrams 1 1 and 20. 
 It will be noticed, also, that a considerable loss of effective pres- 
 sure is caused, for the same reason, as clearly shown by the re- 
 duction of the area of the indicator diagrams. The amount of 
 back pressure against the piston during the remainder of the 
 exhaust, also depends directly upon the amount of release, and, 
 indirectly, upon the speed of the engine. If the exhaust-port 
 is not well open at the end of the stroke, it is evident that the 
 greater volume of the steam must be discharged during the re- 
 turn stroke of the piston until the closing of the exhaust-port; 
 but as the piston attains its maximum velocity at half-stroke, 
 the minimum back pressure above the atmospheric line must 
 then be greater than it would be under the more favorable con- 
 dition of premature escape of the steam. Therefore, the non- 
 release of the steam before the end of the stroke involves not 
 only a direct loss of the work done by the steam, as shown by 
 the corner cut off from the indicator diagrams 1 1 and 20, but
 
 132 THE STEAM-ENGINE AND THE INDICATOR. 
 
 its injurious effect is also manifest during the greater part of the 
 return stroke. The loss of work done through an early release 
 of the exhaust is more than regained during the return stroke, 
 the back pressure against the piston becoming reduced to that 
 of the atmosphere in non-condensing engines. See Figs. 9 and 
 18. 
 
 The Exhaust-line. 
 
 It is, of course, desirable that the pressure of the steam be got 
 rid of as completely as possible before the piston commences its 
 return stroke. This is accomplished by having the exhaust- 
 port and passages sufficiently large, and opening the port a 
 sufficient time before the termination of the stroke, according 
 to the density of the steam to be released and the velocity of the 
 piston. 
 
 The exhaust line commences at the point of release g, Figs. 
 18 and 23, where the expansion-curve changes to convex as 
 the pencil travels to the line of counter pressure, and shows the 
 fall of pressure caused by the release or opening of the exhaust- 
 port for the escape of the steam before the forward stroke is 
 finished, in order to diminish the back pressure. In an engine 
 in which there is no pre-release (the exhaust port opening ex- 
 actly at the end of the forward stroke), the diagram during the 
 return stroke is usually a curve more or less similar to the line 
 g d, see Fig. 20. 
 
 The lower side of the theoretical diagram, Fig. 23, used in 
 calculations, being the line V V, representing the pressure in the 
 condenser, or in non-condensing or "high pressure" engines 
 the atmospheric pressure line, A D. 
 
 By making the release occur early enough, for example, at 
 the point corresponding to^, in Fig. 23, the entire fall of pres- 
 sure may be made to take place towards the end of the forward 
 stroke, so as to make the back-pressure coincide sensibly with 
 that corresponding to the line V V; then the end of the dia- 
 gram will assume a figure represented by the line g D d, in 
 Fig. 23, which is usually more or less concave. The greatest 
 amount of work is insured by making the release take place at 
 point g, so that about one-half of the fall of pressure shall take 
 place at the end of the forward stroke, from g to Z>, and the 

 
 INDICATOR DIAGRAMS. 133 
 
 other half at the commencement of the return stroke, as indi- 
 cated by the curve, D d. The line g D d is traced while the 
 excess of pressure remaining at the point of exhaust is being 
 released. 
 
 Back-pressure, or Line of Counter-pressure. 
 
 If the steam used in working engines were unmixed with air, 
 and if it could escape without resistance, and in an inappreciably 
 short time from the cylinder after having completed the stroke, 
 the back-pressure would be simply, in non-condensing engines 
 (called "high pressure engines' 1 * 1 }, the atmospheric pressure for 
 the time; and in condensing engines, the pressure correspond- 
 ing to the temperature in the condenser, which may be called 
 
 PIG. 24. 
 
 Scale : 40 equal i inch. 
 
 the pressure of condensation. The mean back-pressure, how- 
 ever, always exceeds the pressure of condensation, and some- 
 times in a considerable proportion. One reason for this, which 
 operates in condensing engines only, is the presence of air 
 mixed with the steam, which causes the pressure in the con- 
 denser, and consequently the back-pressure also, to be greater 
 than the pressure of condensation of the steam. For example, 
 an ordinary temperature in a condenser when working properly,
 
 134 
 
 THE STEAM-ENGINE AND THE INDICATOR. 
 
 is about 100 degrees Fahrenheit, to which the corresponding 
 pressure (absolute) of steam is about one pound on the square 
 inch. But the absolute pressure in the best condensers is 
 scarcely ever less than two pounds on the square inch, or nearly 
 double the pressure of condensation. 
 
 The principal cause, however, of increased back pressure, is 
 resistance to the escape of the steam from the cylinder, by 
 which in condensing engines, the mean back pressure is caused 
 to be from one to three pounds on the square inch, greater than 
 the pressure in the condenser. 
 
 In non-condensing engines, experiments show that the excess 
 of the back pressure above the atmospheric pressure varies 
 nearly as the square of the speed; this excess of back pres- 
 sure is less, the shorter the cut-off is, in other words the greater 
 
 FIG. 25. 
 
 the ratio or grade of expansion; that is to say, the longer the 
 time during which the expansion of the steam lasts. In cylin- 
 ders with a mean of 16 per cent, of release, that is, with the ex- 
 haust port opened when the piston had performed 0.84 of its 
 stroke with steam cut off at one-half the length of stroke 
 that is, with a ratio or grade of expansion of 2 nearly, and with 
 a piston speed of 600 feet per minute, being the maximum of 
 speed in a good engine, the excess of the back-pressure above 
 atmospheric pressure was about 0.163 of the excess of the pres- 
 sure of the steam at the instant of release above the atmospheric 
 pressure. When the pressure falls during expansion, as in Fig.
 
 INDICATOR DIAGRAMS. 135 
 
 24, as low as the return or back-pressure, this exhaust line does 
 not exist. 
 
 When the steam is exhausted below the return pressure, as in 
 Figs. 17, 21 and 25, and the exhaust line is forced up from x to 
 /, it indicates a rush of steam from the exhaust chamber back 
 into the cylinder. This shows that the engine is too large for 
 the work, and is working at a loss. 
 
 When the steam is exhausted at a high pressure, and through 
 cramped passages, the exhaust line extends over most of the re- 
 turn stroke, as shown in Fig. 20. 
 
 The Back-pressure Line. 
 
 This is represented by the line d h, Fig. 23, and is the pres- 
 sure behind the piston during the return stroke, and is called 
 back-pressure because it acts in opposition to the return move- 
 ment of the piston. In diagrams from non-condensing engines, 
 (commonly called "high-pressure" engines) it is coincident 
 with one or more pounds pressure above the atmospheric line, 
 (see diagrams, Figs, n and 26) while in diagrams from con- 
 densing engines (commonly called "low-pressure " engines) it 
 is 22 or 24 inches of vacuum below, or such a distance below 
 the atmospheric line as will coincide with the vacuum attained 
 in the condenser (see diagrams, Figs. 16 and 19). The resist- 
 ance offered to the escape of the released steam has the effect of 
 reducing, by a corresponding extent, the effective or indicated 
 power of the engine. When the steam escapes from a non- 
 condensing engine, the back-pressure cannot be less than the 
 atmospheric pressure (14.7 pounds) at the time; and when it 
 escapes from a condensing engine into a condenser, the back- 
 pressure upon the piston cannot be less than the pressure of 
 vapor existing in the condenser. The excess of resistance over 
 these limits depends chiefly upon the state of the steam, the size 
 and direction of the exhaust passages, and the speed of the 
 engine. 
 
 Therefore, the passages and pipes communicating with the 
 atmosphere should be at least fifty per cent, larger than the 
 ports, and as free from angles as possible. 
 
 These requirements apply to condensing engines even more 
 strongly, and in addition the condenser and air-pump must be 
 able to maintain a proper vacuum.
 
 136 THE STEAM-ENGINE AND THE INDICATOR. 
 
 The Point of Exhaust Closure. 
 
 This is shown at h in diagram, Fig. 23, and is where the ex- 
 haust port is closed against the escaping steam. It cannot be 
 located in all cases very exactly by inspection, for while, like 
 the point of cut-off and exhaust, it is anticipated by a change 
 of pressure due to a more or less gradual closing of the valve, it 
 is not marked by a change in curvature of the line. 
 
 The Line of Compression or Cushioning. 
 
 This line, when it exists, is formed by closing the exhaust 
 before the end of the return stroke for example: at the point 
 
 FIG. 26. 
 
 corresponding to ^, on Figs. 18, 23, 26 and 27. A certain 
 quantity of steam in the cylinder is then compressed by the 
 piston during the remainder of the return stroke, and the rise 
 of its pressure is represented by the curve h i. In the dia- 
 grams, Figs. 17, 18, taken from one of the most advanced types 
 of engines, this curve terminates at /, and represents the 'most 
 advantageous adjustment of compression, which takes place 
 when the quantity of confined or cushioned steam, is just suffi- 
 cient to fill the clearance at the initial pressure. 
 
 If this line should be projected above the initial pressure, and 
 then suddenly drop nearly perpendicular to the level of the 
 steam line, thus forming a loop, see Fig. 27, it would indicate 
 an excess of compression, due to closing the exhaust too soon.
 
 INDICATOR DIAGRAMS. 137 
 
 It is evident that this would be very objectionable, involving a 
 loss of efficiency. In computing such a diagram, the area con- 
 tained in the loop x, at the commencement of the stroke, denot- 
 ing negative work as it were, should be subtracted from the 
 total area included in the indicator diagram. 
 
 Compression, also, has a useful effect in the working of an 
 engine, by providing an elastic cushion, whereby the momen- 
 tum of the piston and its connections is gradually absorbed, 
 and the direction of motion reversed without "thump" or 
 "shock," so there is no "jar" from the entering steam when 
 a new stroke begins. The proper regulation of compression 
 serves to make an engine work easily and smoothly, and con- 
 
 FIG. 27. 
 
 
 sequently reduces the wear and tear of the working parts. The 
 pressure due to the momentum of these parts will, of course, de- 
 pend upon their weight and velocity, increasing directly as the 
 square of the speed. These data being given, the amount of 
 cushion or pressure required to counterbalance work stored up 
 in the reciprocating parts, can easily be ascertained. It follows 
 that the compression should decrease rapidly as the speed di- 
 minishes, and vice versa. 
 
 In-fast running engines, especially locomotives, compression 
 also serves to prevent waste from clearance. The capacities of 
 the clearance spaces and the steam-ports are relatively larger 
 than in most other steam engines, on account of the higher 
 speed of the former. These spaces must be filled at the com- 
 mencement of the stroke with high-pressure steam, which is
 
 138 THK STEAM-ENGINE AND THE INDICATOR. 
 
 obtained either by taking a supply of live steam from the boiler, 
 or by compressing into the clearance spaces the low pressure 
 steam that remains in the cylinder at the closing of the exhaust 
 port. But in the latter process a certain quantity of steam is 
 saved at the expense of increased back-pressure. It should be 
 borne in mind, also, that the total heat of the compressed steam 
 increases with its pressure, and as this latter approaches the 
 boiler pressure, the temperature of the steam in compression is 
 also raised, from that of about atmospheric pressure to nearly 
 the temperature of the boiler pressure. These changes of tem- 
 perature, which the steam undergoes, will affect the surface of 
 the metal with which the steam is in contact during the period 
 of compression. It follows, of course, that the ends of the 
 cylinder principally comprising the clearance spaces, acquire a 
 higher temperature than those parts where only expansion 
 takes place. This is an important consideration, since the 
 fresh steam from the boiler comes first in contact with these 
 spaces, and by touching surfaces which have been thus pre- 
 viously heated by the high temperature of the compressed steam, 
 less heat will be abstracted from the live steam, and therefore a 
 less amount of water be depcsited in the cylinder. 
 
 Power expended in compression lessens the available power 
 of the engine without necessarily lessening the efficiency of the 
 steam. Under proper management, as stated above, the com- 
 pressed steam gives out during its re-expansion the power 
 directly expended in compressing it. There is, no doubt, a 
 somewhat great proportional loss by friction, but to counter- 
 balance this, the wasteful back pressure is reduced by the 
 earlier closing of the exhaust. 
 
 The termination of the compression curve should coincide 
 with the beginning of the admission line, i k, see Fig. 23, page 
 125. 
 
 As in expansion so in compression the actual curve as shown 
 by the indicator diagrams generally, and more especially those 
 taken from locomotives, do not coincide with the theoretical 
 curve. Here again the application of the law of Boyle and 
 Mariotte, namely, the volume of the retained steam being in- 
 versely as the pressure, comes nearest to practical results. It 
 will not be difficult to account for the fact that the indicated
 
 INDICATOR DIAGRAMS. 139 
 
 compression curve should be below the theoretical curve. 
 During the period of exhaust the surface of the cylinder cover, 
 piston, and cylinder have become materially cooled. When the 
 exhaust port closes, the pressure and temperature of the retained 
 steam rapidly rise, the temperature of the metal in contact with 
 it rising simultaneously, but owing 'to the surfaces being large 
 in proportion to the quantity of steam, a portion of the steam 
 will be condensed. This loss of compression pressure is at- 
 tended by a corresponding gam of total useful pressure; thus 
 the departure of this curve, as well as that of the actual expan- 
 sion line, below and above the theoretical curves, respectively, 
 shows a proportional increase of the power exerted by the 
 engine, which is clearly demonstrated by the increase of area 
 included in the indicator diagrams. 
 
 Lead. 
 
 Lead means the amount of opening given to the steam port, 
 so as to admit fresh steam into the space where the cushioning 
 is going on, just before the piston comes to the end of the 
 cylinder. In such a case the valve is said to anticipate or lead 
 the motion of the piston, and the lead of a valve may be defined 
 as the width of opening of the steam port when the piston is at 
 the end of its stroke. 
 
 By giving lead to a valve the boiler pressure is brought 
 against the piston just as it is reaching the end of its motion in 
 one direction, and the strain upon the crank-pin is correspond- 
 ingly relieved. The more rapid the motion of the piston, the 
 greater the necessity for giving lead, and accordingly we find 
 that in locomotive engines and the fast running automatic 
 engines, such as the Porter-Allen, Westinghouse, and others, 
 the lead is very considerable. 
 
 The lead, of which mention has been made, is outside lead, 
 that is, it relates to the admission of steam, but of course lead 
 can be given on the exhaust side of the valve, and in that case 
 it would be called inside lead. 
 
 The lead and the period of admission should be the same for 
 each end of the cylinder, for each point of cut-off, and, if pos- 
 sible, in locomotive engines in the back as well as the forward 
 Rear.
 
 140 THE STEAM-ENGINE AND THE INDICATOR. 
 
 It is found necessary, especially with high speeds of piston, 
 in order to insure good action of the steam, that the maximum 
 cylinder pressure should be attained at the very commencement 
 of the stroke. If the steam-port is not opened until after the 
 piston has commenced its stroke, especially where there is but 
 little compression, some appreciable time would be consumed in 
 filling the clearance space and the steam passages with steam. 
 In locomotives where the slide valve is worked by the ordinary 
 link-motion, the steam-port will not open rapidly enough to 
 enable steam of the maximum boiler pressure to fill the space 
 after the receding piston, unless the valve begins to open the 
 steam-port before the piston begins its stroke; that is, before the 
 end of its preceding stroke. The Baldwin Locomotive Works 
 allow from rV (0.0625) t & (- I 875) inch lead according to the 
 class of locomotives, but in ordinary cases from -fa or 0.03125 to 
 rV or 0.0625 f an inch will be sufficient. 
 
 When the maximum cylinder pressure is attained at the com- 
 mencement of the stroke, the admission line of the indicator 
 diagram the piston being at the end of the stroke will rise in 
 a vertical line (see Figs, u, 16, 19 and 23), but if the maximum 
 pressure is not so attained the admission line will deviate 
 slightly from the vertical (see Figs. 14, 15, and 20). 
 
 Lead and compression both regulate the steam admission. 
 If the clearance space at the beginning of the admission is 
 already filled with compressed steam, a less amount of lead is 
 necessary, and vice versa. 
 
 In locomotive engines with the shifting link motion, however, 
 not only the lead but also the compression increases rapidly as 
 the link approaches mid-gear or half stroke; this is not a draw- 
 back, as the increased compression is calculated to facilitate 
 greatly the attainment of the full pressure of steam in the 
 cylinder at the commencement of the stroke. 
 
 Furthermore, it should be remenfbered that a good admission 
 of the steam depends, not only on the amount of lead, but also 
 on the commencement of it, or, in other words, on the period 
 at which the valve opens the connection with the steam chest 
 preparatory to the next stroke of the piston.
 
 
 INDICATOR DIAGRAMS. 141 
 
 The Mean Effective Pressure. 
 
 The mean effective pressure is the difference between the mean 
 or average propelling pressure, and the mean or average back 
 pressure. This pressure is best obtained from indicator dia- 
 grams. To arrive at it correctly we divide the length of the 
 card into ten or more equal spaces so arranged that there is a 
 half space at each end (see dotted lines, Figs. 9 and n). Ten 
 is a convenient number, but this is immaterial; any other num- 
 ber may be used ; the more numerous the spaces, of course, the 
 greater the accuracy. . 
 
 The Terminal Pressure. 
 
 This term is sometimes applied to the pressure at the exhaust 
 point when the steam is released, but as it is an indispensable 
 factor in the calculations, it is properly defined as the pressure 
 that would exist at the end of the stroke if the steam had not 
 been released at that earlier point. A continuation of the ex- 
 pansion curve, as at g, in Fig. 29, page 145, see dotted line, 
 will explain the method of finding it; Figs. 9, 10, n and 19 
 show that the exhaust has taken place at the end of the stroke; 
 hence in those diagrams terminal and exhaust pressure are the 
 same. This pressure is measured from the extremity of the 
 curve to the vacuum line, V V, hence it is the absolute terminal 
 Pressure. 
 
 The Initial Pressure. 
 
 The initial pressure is that pressure which acts upon the pis- 
 ton at the beginning of its stroke up to the point of cut-off, and 
 is always less than that of the boiler, because as soon as the 
 steam leaves the boiler it begins to condense and decrease in 
 pressure. It can receive no more heat from any source, but it 
 must impart heat to everything, and supply all loss resulting 
 from radiation. A portion of the steam is always condensed as 
 it enters the cylinder, from coining in contact with the surfaces 
 which have just been cooled down by being exposed to the 
 colder vapor of the exhaust steam; more especially is this so in 
 slow-running engines where little or no compression takes 
 place.
 
 142 
 
 THE STEAM-ENGINE AND THE INDICATOR. 
 
 Initial Expansion. 
 
 Initial expansion is the expansion that takes place during the 
 admission of steam before the steam is cut off. The steam line, 
 k e, in diagram Figs. 22 and 28 shows considerable initial ex- 
 pansion, which is desirable in a "throttling" engine; from the 
 fact that saturated steam becomes superheated during the pro- 
 cess of "throttling;" but is not desirable in cut-off engines. 
 
 Wire-drawing and Throttling. 
 
 When steam is reduced in pressure by passing through a con- 
 tracted passage, as in a stop-valve partly closed, or in the com- 
 mon "throttle-valve," it is said to be "throttled," and is shown 
 
 FIG. 28. 
 
 by the fall of the steam line, k to , as exhibited in Figs. 22, 28, 
 and 60. 
 
 The term ^wire drawing' 1 ' 1 is almost identical in meaning 
 with throttling, but refers especially to the slow cutting off of 
 steam by an ordinary slide valve, the result in the diagram be- 
 ing a gradual slanting downwards of the steam line until it 
 passes imperceptibly into the expansion line. Diagram Fig. 28 
 is an example of this, and the dotted lines show what the effect 
 of a quick cut-off would accomplish by means of an expansion 
 valve. 
 
 With the ordinary valve-gearing, especially the shifting link
 
 INDICATOR DIAGRAMS. 143 
 
 in common use in locomotive engines, or when a single eccen- 
 tric connected directly to the valve-rod is used, it is impossible 
 to obtain an early cut-off without a certain amount of wire- 
 drawing. If, under these circumstances, an earlier cut-off than 
 half stroke is attempted, wire-drawing becomes excessive. 
 
 The above diagram, Fig. 28, taken from one of the most ad- 
 vanced types of locomotives, exhibits considerable wire-drawing. 
 The dotted line shows the pressure that might have been ob- 
 tained with the same amount of steam more rapidly introduced 
 into the cylinder, indicating a loss from this cause alone of 
 about ten per cent, of the whole power of the engines. 
 
 In fact, wire-drawing is due to the area of the port getting 
 less and less in area, the steam undergoing a reduction of pres- 
 sure owing to frictional resistance it has to overcome. This 
 phenomenon is called wire-drawing, or more properly by the 
 French, lamination of steam. 
 
 Diagram, Figure 28, is worthy of study and emulation by 
 builders of fixed cut-off engines, for the locomotive has simply 
 a fixed cut-off engine, variable by hand. But so long as fixed 
 cut-off engines are controlled in speed by the present system of 
 governor, which, as it were, throttles the steam supply to the 
 engine in the act of respiration, but little improvement can be 
 expected in the realized effect of valve motion. 
 
 The ordinary. throttling governor is a nuisance that should 
 not be tolerated by intelligent steam-engine builders, for in the 
 best form it robs the steam of twenty per cent, of its work in 
 effecting regulation, and the high relative economy of the 
 standard automatic cut-off engine is entirely due to admitting 
 steam at or near the boiler pressure, and cutting off the quantity 
 required to overcome the resistance, instead of wire-drawing the 
 steam until the mean pressure is equivalent to the resistance 
 per square inch on piston. 
 
 In the locomotive engine, whilst the communication between 
 the steam-dome and cylinder is not as free with early points of 
 cut-off as in the automatic engine, the wire-drawing is very 
 much less than in throttling engines; and if a valve gear be 
 devised for locomotives which will produce a maximum opening 
 of steam port for all points of cut-off, then for equal initial 
 pressures and grades of expansion the economy of the locomo-
 
 144 THE STEAM-ENGINE AND THE INDICATOR. 
 
 tive and automatic engines (size of cylinder and speed of piston 
 considered) would approximate. 
 
 For a given speed, given load, and given condition of track, 
 the resistance is represented by a certain mean pressure per 
 square inch of piston for a single stroke or for any number of 
 strokes, with the elements affecting the resistance unchanged; 
 and a nearer approximation of the initial pressure in the cylinder 
 to that of the boiler, reduced friction in the port opening as the 
 steam flows in, steam line declining less to the point of cut-off, 
 earlier cut-off and higher grade of expansion, would improve 
 
 FIG. 29. 
 
 the economy in performance of the locomotive without impair- 
 ing its efficiency otherwise. It is possible to do all this without 
 materially altering the existing valve gear. 
 
 Modern automatic cut-off valve arrangements are so designed 
 as to avoid wire-drawing with high rates of expansion; the 
 commonest and simplest being by means of double eccentrics, 
 one of which is operated by the governor so as to give a suffi- 
 ciently rapid and early cut-off; see diagrams Figs. 8, 9, n and 18, 
 which show a perfectly steady steam line up to point of cut-off, 
 with expansion through the rest of the stroke. 
 
 It is an established fact that "wire-drawing" and "throt-
 
 INDICATOR DIAGRAMS. 145 
 
 tling" are accompanied by direct loss due to the reduction in 
 pressure which takes place during the process, and by indirect 
 waste owing to the increased proportion of work expended in 
 overcoming the back-pressure. 
 
 Aside from the economic loss, there is the no less serious ob- 
 jection to contracted passages, that, as the cylinder pressure is 
 reduced, (and, therefore, the power of the engine in the same 
 proportion), a large sized engine becomes only equal to one of 
 less size, weight and cost, with more liberal steam passages. 
 
 Undulations, or Waviness of the Expansion Line. 
 
 The waviness sometimes seen in expansion lines is caused by 
 the inertia of the indicator piston, and in some cases by the use 
 
 FIG. 30. 
 
 of a weak indicator-spring on high speed engines; see diagram 
 Figs. 29 and 30. The weaker the spring the more rapidly the 
 steam will compress it, and consequently the greater will be the 
 velocity of the indicator-piston in rising; but the momentum 
 (which is proportional to the square of the velocity) carries the 
 piston above the point to which the steam pressure alone would 
 have compressed the spring. When the momentum has been 
 destroyed by the spring, the spring then forces the indicator 
 piston below the point where it and the steam would be in 
 equilibrium, and it is again forced too high. These alternate 
 up and down movements produced by the momentum, combined 
 10
 
 146 THE STEAM-ENGINE AND THE INDICATOR. 
 
 with the lateral movement of the card, give the wavy line, as 
 shown in Fig. 30. 
 
 These lines are of great value, as they show precisely the 
 degree of suddenness or violence of the action of the indicator. 
 They may occur at the point of admission, of cut-off, and of 
 exhaust. 
 
 Diagram, Fig. 29, taken from a high speed engine running at 
 the Brush Electric Light Station, Philadelphia, Pa., in 1882, at 
 292 revolutions per minute, affords a beautiful illustration of 
 this action. 
 
 FIG. 31. 
 
 To diminish the extent of these undulations, the spring of the 
 indicator should be stiff, and its mechanism light. These 
 undulations when excessive make it extremely difficult to 
 determine the mean effective pressure from the diagrams when 
 measured by ordinates. To determine the area it is customary, 
 and more accurate, to sketch a diagram freed from these undu- 
 lations, over the actual diagram taken (as represented by dotted 
 lines in Fig. 30), midway between the crests and hollows of the 
 waves. This is better than drawing a line inclosing the same 
 area with the wavy line. 
 
 Where the fall of the expansion line is a succession of steps 
 (see diagram, Fig. 31), it shows slight friction in the instrument 
 and that there is no rise of the pencil ; no reaction.
 
 INDICATOR DIAGRAMS. 147 
 
 The Expansion Curve of Indicator Diagrams. 
 
 A correct curve does not necessarily show an economical 
 engine, since the leakage out may balance the leakage in, in 
 rare cases, and not affect the diagram. But the opposite is 
 indisputable that an incorrect curve necessarily, and infallibly, 
 shows a wasteful engine, to at least the amount calculated upon 
 the diagram. 
 
 As indicator diagrams represent the measure of force or pres- 
 sure of the steam in the cylinder at every point of the stroke, 
 the actual card from an engine as compared with the theoretic 
 diagram (other things being equal) indicates the working value 
 and economy of the engine. 
 
 Therefore, they should truthfully represent the real per- 
 formance of the engine. Diagrams vary in form, from various 
 causes; namely, quality or condition of the steam, leakage, 
 condensation, adjustment and construction; their influence 
 being most noticeable in the expansion curve. This curve will 
 not in practice conform exactly to the true theoretical curve. 
 The terminal pressure will always, under the most favorable 
 conditions, be found relatively too high, the amount being 
 greater as the ratio or grade of expansion increases. Where this 
 is not the case, and the expansion curve of the diagram taken 
 coincides exactly with the theoretic curve, the conclusion can- 
 not be otherwise than that the leakage is greater than the re- 
 evaporation; but in the present state of the arts, there are no 
 practical means of working steam expansively, and preserving 
 the exact temperature due to the pressure while expanding. 
 
 When the expansion curve falls, throughout its entire length, 
 below the hyperbolic or theoretical curve, it is evidently due to 
 leakage. The expansion curve of the indicator diagram in all 
 ordinary cases terminates above that of the theoretical curve; 
 in fact sometimes far above it, due to the re-evaporation of the 
 moisture in the cylinder. An engineer when indicating an 
 engine should see to it that the piston and valves are tight. 
 Unless they are so, the diagram will not indicate what the 
 engine is really doing, and the engineer cannot ascertain the 
 causes of any peculiarities in the form of the diagram.
 
 CHAPTER IX. 
 
 CORRECT INDICATOR DIAGRAMS. 
 
 IN order that the indicator diagrams shall be correct, it is 
 essential, first, that the motion of the paper drum shall coincide 
 exactly with that of the engine piston; and second, that the 
 position of the pencil shall precisely indicate the pressure of 
 steam in the cylinder. 
 
 The first condition is frequently somewhat difficult to bring 
 about, because it is not only necessary that the beginning and 
 end of the motions shall be coincident, but that these and all 
 intermediate points shall be so. Owing to the irregular motion 
 of the engine-piston, consequent upon the varying angularity of 
 the connecting-rod, it is generally advisable to connect the 
 cord in some way to the piston-rod cross-head. If any other 
 point be chosen, it must be carefnlly seen that the motion given 
 does not vitiate the diagram. 
 
 As the motion of the parts mentioned exceeds in length the 
 motion of the indicator, it must be reduced in length by levers 
 of such proportions as may be required for that purpose. For 
 example: If the stroke of the engine is thirty -six inches, and the 
 length of the diagram is to be four inches, then the lengths of 
 levers are as one is to nine, or if only one lever is used, then the 
 indicator motion must be taken from a point on the lever suffi- 
 ciently far from its fixed end to obtain the reduced travel 
 required. 
 
 A convenient method to obtain the reducing motion of the 
 piston for the paper drum of the instrument is by a lever swing- 
 ing on a fixed centre, and connected -at its free end to the cross- 
 head of the engine, either by a connecting rod, or a pin on the 
 free end, working in a slot of an arm secured to the cross-head; 
 and on this lever a stud is fixed at the proper distance from the 
 fixed centre (as above shown by calculation), to give the required 
 motion by transmitting it by a cord to the indicator. 
 
 Either of these arrangements is easily made, and they are 
 (148)
 
 CORRECT INDICATOR DIAGRAMS. 149 
 
 very convenient, since the motion of the pin to which the cord 
 is attached is simply a vibrating one, and it can generally be 
 so placed as to enable the cord to lead directly to the indicator, 
 in a direction, of course, at right angles to the mean position 
 of the lever. The cord used should be of braided linen, about 
 one-twelfth of an inch in diameter. It should be well stretched 
 before being used, then gone over with a piece of bees- wax, and 
 afterward with a piece of soft pine wood, with a notch in it, 
 keeping it well stretched all the time. If the above directions 
 are not carried out, much inconvenience may be the result. (A 
 fine piece of piano wire is often used, and is a good substitute.) 
 Convenient means should be provided for attaching it to, and 
 detaching it from, the short length of cord on the indicator 
 paper drum. 
 
 In case of a beam-engine, a point on the beam, or beam- 
 centre, or on the parallel-motion rods, where these are employed, 
 will give the proper motion; but care must be taken that the 
 cord be so led off, that when the engine is on half stroke, it will 
 be at right angles to whatever gives it motion, a requirement 
 too often omitted. Afterwards its direction of motion may be 
 changed as required, care always being taken, however, to use 
 as few carrying pulleys as possible, and the shortest practicable 
 length of cord. 
 
 It is perhaps needless to say that the reason why the use of a 
 short direct cord is to be preferred, is that the shorter the cord 
 the less it will stretch, and guide-pulleys may cause slight ir- 
 regularities, beside stretching the cord more because of increased 
 friction and inertia. 
 
 The Proper Place to Attach the Indicator. 
 
 For great accuracy in fast running engines, the common 
 practice of connecting the two ends of the cylinder together by 
 pipes leading to the indicator is incorrect, as the steam pressure 
 will be seriously diminished by passing through long pipes of 
 small diameter. Two indicators should always be employed. 
 
 In most cases only one is used, but it is always desirable to 
 indicate both ends of the cylinder as nearly simultaneously as 
 possible, so as to avoid unknown changes of load while shifting 
 from one end to* the other. As before stated, it is best to run
 
 150 THE STEAM-ENGINE AND THE INDICATOR. 
 
 half-inch pipe from each end of the cylinder to a three-way cock 
 at the middle, where the indicator is to be attached. There 
 should also be angle stop-valves in the pipe close to the cylinder 
 ends, the angle stop-valves being merely used to shut off the 
 additional clearance due to the volume of the pipe. If the 
 three-way cock is dispensed with and a tee (T) fitting put in its 
 place, the steam when admitted will rush by the tee (T) outlet 
 to the other valve before it reacts up the outlet of the tee (T) to 
 the indicator. If a three-way cock is not used, put two straight- 
 way cocks as close as possible to the tee (T). 
 
 In applying the indicator, especially in high-speeded engines, 
 the connection should be made at some part of the cylinder 
 where the steam is as quiet as possible, so that the pressure in 
 the instrument may be the same as in the cylinder, since, from 
 the well-known laws of fluids, if the connection be made at a 
 point where there is a strong current of steam, the pressure in 
 the indicator will be materially affected. The cylinder heads, 
 therefore, will be the best place to make the connection, the 
 hole being drilled for the connection on the opposite side of the 
 steam-port, and not so low down as to be liable to receive 
 the water of condensation, as the latter makes the action of the 
 indicator very irregular. The connecting pipes should be as 
 short as possible, and no more bends or turns should be used 
 than are absolutely necessary, so that the pressure may not be 
 reduced by the friction that these give rise to, and with the 
 same object the pipe should be of large diameter, say not less 
 than one-half inch internally. 
 
 When taking diagrams they should be repeated several times 
 in order to obtain a good mean value. It is important to know 
 the effect of changes which take place in the cylinder during 
 the motion ; the indicator diagrams are best taken on the same 
 paper, in order to make a comparison. 
 
 Those who have never taken indicator diagrams from engines 
 running at over 300 revolutions per minute, must not think 
 it is unattended with difficulties. Although these difficulties 
 exist, they are far from being insuperable. To insure success 
 under such conditions, the indicator drum must be fitted with 
 stiff springs, the length of the diagrams must be made very 
 short, and stiff springs must be used in the indicator cylinder
 
 
 CORRECT INDICATOR DIAGRAMS. 151 
 
 In addition to these precautions, care must be taken that the 
 passage between the cylinders and the indicator are short and 
 as straight as possible, and the indicator must be driven in the 
 most direct manner that can be arranged, and with the least 
 possible length of cord, as at high speeds the elasticity of the 
 cord is a source of trouble. 
 
 The circumstances under which the diagram was taken should 
 be marked upon the card at once, when it is removed from the 
 drum of the instrument. 
 
 Among the facts in regard to which these diagrams will 
 testify are: 
 
 First All the functions of the valve motion. 
 
 Second Accidental circumstances, such as leaks, contracted 
 steam passages, defective packing, &c. 
 
 Third The quantity of steam contained in the cylinder at 
 any moment or point of stroke, throwing light on the amount 
 of condensation that takes place. 
 
 Fourth The horse-power that the engine is developing. 
 
 Fifth The efficiency of the steam ports and passages for the 
 admission or discharge of the steam, including the effect of the 
 condenser. 
 
 Sixth From the air-pump the nature of the performance of 
 the pump, and the power required to operate it. 
 
 Seventh It will show the line of pressure in the condenser, 
 and that of the back pressure in the cylinder, which will always 
 be less than that shown by the vacuum gage. 
 
 Eighth On the steam chest the loss of pressure due to an 
 insufficiency of area in the steam pipe. 
 
 Ninth On the exhaust pipe to show the cause of excessive 
 back pressure, whether due to too small an exhaust pipe or port 
 opening. 
 
 Tenth On the boiler to register the pulsations caused by the 
 sudden closing of the cut-off valve. 
 
 Length of Indicator Diagrams. 
 
 In slow running engines, the diagram should be at least four 
 inches in length, as a long card is better than a short one, when 
 taken for adjusting valves, because slight variations are rep- 
 resented at correspondingly greater magnitude. On the other
 
 152 THE STEAM-ENGINE AND THE INDICATOR. 
 
 hand, and particularly at high speed, long cords will sometimes 
 introduce errors that should be avoided. 
 
 Cards from high speeded engines should not exceed three 
 inches in length, according to speed and other conditions. It 
 must be borne in mind that at high speed the inertia of the 
 paper-drum becomes an important factor, and in long cards this 
 will affect its correctness. 
 
 As I have before stated, the indicator is an instrument by 
 means of which a steam engine is caused to write on a piece of 
 paper an accurate record of the performance of the steam that 
 takes place within the cylinder. It gives a record which to the 
 uninstructed eye is unintelligble, but by engineers it is looked 
 
 FIG. 32. 
 
 upon as the most reliable statement they can have of the work 
 done by an engine, inasmuch as it tells at each and every part 
 of the stroke of the piston what are the effective pressures tend- 
 ing to produce motion, and what are the back pressures tending 
 to detract from the effective pressures. 
 
 Indicator Diagrams. 
 
 Assuming that we have an indicator attached to a steam 
 engine cylinder, and so connected that the drum containing the 
 paper is moving to and fro, coincident with the piston of the 
 engine, if before letting in steam to the indicator or cylinder, 
 we apply the pencil to the surface of the paper, it will draw 
 upon the paper a horizontal line, A to Z>, in length propor- 
 tionate to the stroke of the engine. See Fig. 32.
 
 CORRECT INDICATOR DIAGRAMS. 
 
 153 
 
 Now, if we open the cock attached to the indicator cylinder, 
 and assume that the engine piston has just commenced to move 
 from A to D, the indicator piston will also move vertically, and 
 the pencil will trace the line, AB, representing the pressure per 
 square inch of the steam in the engine cylinder. 
 
 Assuming that the indicator spring is one which would com- 
 press one inch for every forty pounds pressure per square inch 
 acting on the piston, then if there were 100 pounds pressure per 
 square inch on the engine piston, the pencil would rise two and 
 a half inches from A to B. Now, suppose the engine piston to 
 have completed its stroke : the pencil having traced the line 
 BC, and the slide valve to have opened the exhaust port so as 
 to allow the steam to escape, then the indicator piston will fall, 
 and the line CD will be traced. On the return stroke, the 
 
 FIG. 33- 
 
 pencil would follow the line DA, with the exception of any 
 diversion caused by steam that might remain in the cylinder in 
 consequence of the steam not having been perfectly exhausted. 
 Leaving this out of the question, it would have returned to the 
 point /), and thence to A thus describing a parallelogram, of 
 which the horizontal line AD would represent the stroke of the 
 piston, and the vertical line VB would represent the steam 
 pressure upon the piston. The area of this parallelogram 
 would, therefore, represent pounds pressure into feet moved 
 through by the piston in its stroke, or revolution of the engine.
 
 154 THE STEAM-ENGINE AND THE INDICATOR. 
 
 Now, for simplicity, suppose that the line AD, Fig. 32, rep- 
 resents a foot stroke of the piston of one foot; that the piston 
 has an area of 99 square inches, and that the line, VB, repre- 
 sents 100 pounds pressure to the square inch, then we shall have 
 100 pounds multiplied by one foot, and this equals 100 foot 
 pounds, which multiplied by 99 square inches (area), will equal 
 9,900 pounds as the work performed by the piston in one stroke, 
 or half revolution. For both strokes, we have 9,900 multiplied 
 by two, equaling 19,800 pounds as the force exerted by the 
 engine through one revolution. If the engine makes 100 revo- 
 lutions per minute, then 19,800 X 100 = 1,980,000 pounds, 
 
 FIG. 34. 
 
 would be the force exerted by the piston of such an engine in 
 one minute. This, divided by 33,000, gives sixty-horse power, 
 which is called the gross indicated horse-power. 
 
 Diagram, Fig. 32, is one that seldom if ever occurs in practice. 
 When such are produced, they are only justified by the desire 
 to obtain the greatest possible power from a given size of engine 
 without regard to the highest economy. It will be seen that 
 steam was supposed to have been admitted during the whole 
 length of the stroke, and that no advantage whatever has been 
 taken of the expansive property of the steam. 
 
 Diagram, Fig. 33, shows steam used expansively. 
 
 Assume the same data as in former case, the 100 pounds pres- 
 sure above the atmosphere has raised the pencil from A to B;
 
 CORRECT INDICATOR DIAGRAMS. 155 
 
 also assuming that the steam has been admitted to the engine 
 cylinder up to the point , (half the length of the stroke,) and 
 then cut off by the valve; the steam now in the cylinder begins 
 to expand, and as it expands it loses pressure. By the time, 
 therefore, that the piston has arrived at^, from , the steam will 
 have lost pressure, and the pencil will gradually fall and trace 
 the curved line eg. By the time the piston has reached the end 
 of the stroke, the pressure will further have diminished, say to 
 g, and when the exhaust opens it falls down to D. 
 
 It will be seen "by this diagram that, although only half as 
 much steam was admitted into the cylinder, as in the case of 
 diagram, Fig. 32, the area of the diagram is very much more 
 than half of that of Fig. 32; as a matter of fact, it is about 0.83 
 of that area, and thus a power 0.83 has been obtained by using 
 
 FIG. 35. 
 
 expansively half the steam that was required in the case of Fig. 
 32- 
 
 As a further illustration, Fig. 34 is a diagram that would be 
 produced if the steam were cut off when the piston had moved 
 one-fourth of the stroke. In this instance only one-fourth the 
 steam required, as for Fig. 32, would be needed; but the total 
 area of the diagram is about 0.54 of that of Fig. 32, so that 
 0.54, or more than one-half as much work, is obtained for one- 
 fourth the steam. 
 
 Figure 35 is a diagram taken from a Corliss engine 8 inches 
 diameter and 24 inches stroke; 90 revolutions per minute.
 
 156 THE STEAM-ENGINE AND THE INDICATOR. 
 
 Starting from the top corner B, the steam pressure remains 
 uniform to about point e; here the cut-off valve being closed, 
 the pressure commenced to fall, as represented by the curved 
 line eg, until it reached the point g, when the exhaust-valve be- 
 ing opened (allowing the steam to pass into the atmosphere), it 
 quite suddenly drops from g to D; when the piston begins to 
 return. There remains a slight pressure in the cylinder, until 
 the time the piston gets to h, that is the back -press lire through- 
 out the stroke, so that it keeps the line of the pencil about 0.6 
 of a pound above the atmospheric line A D, until the closing 
 of the exhaust-valve, which occurs at the point ^, after which 
 time the steam remaining in the cylinder is compressed, raising 
 the indicator-pencil and forming the curved line h i. 
 
 In this case, the effective work done by the engine is repre- 
 sented by the area contained within the irregular figure /, e, 
 g, h and i. This is after allowing for the back-pressure and 
 the compression, which are contained between that figure and 
 the lines z, h and D. 
 
 We have now described how a diagram is taken from one end 
 of the cylinder. To obtain it from the other, all that has to be 
 done is to make a pipe connection from the two cylinder heads 
 fitted with a three-way cock (as before described) and diagrams 
 may be got on the same piece of paper, and would, if the engine 
 were perfectly equal in performance at the two ends, be repre- 
 sented as it was in this case by the dotted line on Fig. 26. The 
 sum of these two areas will represent pounds pressure through 
 the length of the stroke of the piston in a whole revolution, 
 which multiplied by the area of the piston and the number of 
 revolutions per minute, will give the foot-pounds. This divided 
 by 33,000, will give the gross indicated horse-power of the 
 engine. 
 
 Use of the Indicator for Showing the Condition of the 
 Engine'. 
 
 The indicator tells us not merely the power exerted by the 
 engine, but the nature of the faults by which the power is im- 
 paired. Thus, the shape of the indicator diagram may show 
 that the steam or exhaust-ports are too small, or that the valve 
 has not sufficient lead or is improperly set. Let us take, for ex- 
 ample, the following diagram, Fig. 36.
 
 CORRECT INDICATOR DIAGRAMS. 
 
 157 
 
 When the indicator pencil is at the point /, the engine 
 piston is at the commencement of its stroke, the paper-drum in 
 motion. The line is traced from k to , and thence to g, at 
 which point the stroke is finished in this direction. At the 
 point e, the valve closed the steam port, or, in other words, the 
 steam was cut off, and while the line from e to g was being 
 traced, the steam pressure in the engine cylinder was expand- 
 ing, and its pressure consequently decreasing, as shown by the 
 falling of the line eg. The line from e to g being convex, in- 
 
 FIG. 36. 
 
 stead of concave in shaded diagram, shows that either the slide 
 valve or the piston, probably both, were not in good order, and 
 admitted steam during expansion. The fall of the steam line 
 from k to e also shows that the steam ports are too small. At 
 the point g, the exhaust valve is open to the atmosphere, the 
 steam escapes, the pressure in the engine cylinder falls, and the 
 pencil descends towards D. The diagram, as here.given, shows 
 that the exhaust port is opened too late, for this corner of the 
 diagram should be very nearly square (see diagram outside of 
 shaded one). The engine piston now commences its return 
 stroke, and the line^ h is traced, representing the exhaust line, 
 and before reaching the end of its stroke, it commences to rise 
 again at ^, thus indicating that there is some pressure arising
 
 158 THE STEAM-ENGINE AND THE INDICATOR. 
 
 from the compression of the steam and vapor remaining in the 
 cylinder. This is due to the closing of the exhaust port ^, be- 
 fore the end of the stroke, causing the curved line h i. The 
 rounded corner at k shows that the valve is wanting in "lead," 
 or in other words the steam port was opened too late, as is also 
 the case at^ the exhaust end; in the latter case showing that the 
 release of the exhaust steam is not early enough, and that in 
 consequence of this the back pressure at the commencement of 
 the return-stroke is much too high. This shows that the slide- 
 valve was improperly set, a defect which can be remedied by 
 shifting the eccentric slightly ahead. This will improve the 
 exhaust by causing an earlier opening, shown by the dotted 
 curved line eg' , also causing earlier compression, as shown by the 
 outside line at the point of compression, as well as the increased 
 lead and initial steam pressure at B. The power exerted is thus 
 increased at least ten per cent, with the same amount of steam. 
 The steam-line should be parallel with the atmospheric line up 
 to point of cut-off, or nearly so. Should it fall, as the piston 
 advances, the opening for the admission of steam is insufficient, 
 and the steam is wire-drawn. 
 
 The point of cut-off on all engines should be sharp and well 
 defined : if otherwise, it shows that the valve does not close quick 
 enough. 
 
 By having an indicator at each end of the engine cylinder, 
 the back and forth action of the steam in the cylinder is simul- 
 taneously recorded in the form of a diagram, as before stated, by 
 horizontal and vertical lines and curves. This diagram com- 
 prises time of admission, steam-line, point of cut-off, expansion 
 curve, terminal pressure, point of exhaust (or relief exhaust) 
 line, back-pressure line, compression curve, initial pressure and 
 initial expansion. From these records the total work done by 
 the steam can be accurately ascertained. Very accurate mens- 
 urations have, been made by the indicator, but the average area 
 of indicator cylinders is only about one-half of a square inch, 
 while that of cylinders indicated may vary from ten square 
 inches to as many square feet. By the use of the indicator, the 
 determination between nominal (calculated), indicated (real) and 
 effective horse-power is found; the variations between which are 
 very marked.
 
 CORRECT INDICATOR DIAGRAMS. 159 
 
 The indicator also furnishes one of the data for ascertaining 
 the power exerted by the steam engine; namely, the mean or 
 average pressure of the steam during the stroke, on each square 
 inch of the piston; stated more accurately, it shows the excess 
 of pressure on the steam side of the piston to produce motion 
 over that on the exhaust side to resist it; and from no other 
 source can it be so accurately ascertained. 
 
 The pressure in the boiler is readily known, but the steam in 
 its passage to the cylinder is subject to various losses, such as 
 wire-drawing, condensation, friction, etc., so that, frequently, 
 the pressure on the piston does not exceed two-thirds of that on 
 the boiler. 
 
 The Geometry of the Indicator Diagram. 
 
 It is now generally admitted that the true curve traced b}' the 
 pencil of the indicator, when the steam is expanding in the 
 cylinder, is hyperbolical; and as the remainder of the penciled 
 figure is a portion of a parallelogram, the curve is the only 
 geometrical question to dissect. When the pencil was station- 
 ary, the atmospheric line A D (in Fig. 34, page 154) was drawn 
 straight, from the fact that there was no steam pressure to move 
 the indicator piston ; but when the steam pressure acted on it, 
 the pencil rose vertically to B. At this point the indicator paper 
 drum commenced to move, and therefore, as the pencil was 
 maintained at this height by the steam pressure acting on the 
 piston during the steam supply, a straight horizontal line was 
 traced from B to e; at <?, the steam was cut off from the cylinder, 
 and the expansion of the steam enclosed in the cylinder com- 
 menced, due to the forward motion of the engine piston, and the 
 steam pressure gradually commenced to fall as the paper drum 
 of the indicator moved forward, coincident with the engine 
 piston, and the indicator pencil described a curve as it descended, 
 until reaching the pointy below the atmospheric line. At this 
 point the paper drum stopped, from the fact that the engine pis- 
 ton had reached the end of its forward stroke, and the pencil con- 
 tinued to fall at right angles to the steam line k e, until the 
 vertical line D V was traced, the point V indicated the amount 
 of vacuum attained in the cylinder; the pencil then became sta- 
 tionary, from the fact that the atmospheric pressure forced the
 
 l6o THE STEAM-ENGINE AND THE INDICATOR. 
 
 indicator piston down and kept it in that position while the 
 vacuum was maintained, as firmly as the steam held it up dur- 
 ing the time the steam pressure was acting on the piston. From 
 this it will be seen that the indicator pencil is always motionless 
 when the/ult pressures are acting on either side of the indicator 
 piston. When the pencil stopped at V, the paper drum com- 
 menced to move in the opposite direction, and thus the line W 
 was traced, at the end of which the paper drum again stopped, 
 and when the steam was admitted again into the cylinder the 
 pencil instantly rose, and completed the line V B, thus forming 
 the theoretical diagram, Fig. 34. 
 
 The movement of the pencil is therefore instantaneous, verti- 
 cal from V\.Q B and D to V, eg is a gradual descent, while k e 
 and V V have no motion. The line A B being the admission, 
 k e steam supply, e g expansion, g V exhaust, V V continuous 
 exhaust, and V A readmission. 
 
 Back Pressure. 
 
 If the steam used to run steam-engines could escape freely 
 without resistance, the back pressure would be simply the 
 pressure of the atmosphere in non-condensing engines, and in 
 condensing engines it would be the pressure corresponding to 
 the temperature in the condenser, which is called the "pressure 
 of condensation." The mean back pressure, however, always 
 sometimes considerably exceeds the pressure of condensa- 
 tion. One cause of this, in condensing engines, is the pressure 
 of air mixed with the steam, which causes the pressure in the 
 condenser, and also the back pressure, to be greater than the 
 pressure of the condensation of the steam. The ordinary tem- 
 perature in the condenser in proper working order is about 100 
 degrees Fahrenheit, for which the pressure is about one pound 
 per square inch, whilst the actual pressure in the best condenser 
 of ordinary engines may be scarcely less than 1.15 to 2 pounds 
 to the square inch. The principal cause, however, of increased 
 back pressure is resistance to the escape of the exhaust steam 
 from the cylinder, due to the exhaust pipes being too small, 
 amounting to from one to two pounds per square inch, greater 
 than the pressure in the condenser. 
 
 There is no doubt that practically in condensing engines, the
 
 CORRECT INDICATOR DIAGRAMS. l6l 
 
 back pressure increases with the speed of the engine, and also 
 with the density of the exhaust steam and with a reduced size 
 of the exhaust ports. 
 
 But with a well constructed and proportioned condensing 
 engine, a gain of about ten pounds or 20.4. inches mean effective 
 pressure over, that of a non-condensing engine can be effected. 
 
 In non-condensation engines, especially in locomotive engines, 
 the excess of back pressure above atmospheric pressure, varies 
 nearly as the square of the speed to the pressure of the exhaust 
 steam at the commencement of the exhaust, and inversely as 
 the square of the area of the orifice of the blast pipe, that it is 
 less the greater the ratio of expansion, that it is less the longer 
 the time during which the exhaustion of the steam lasts, and 
 that it is increased when the steam is wet. Sometimes the 
 excess of back pressure above that of the atmosphere is scarcely 
 perceptible, as in diagrams Figs. 24 and 26. In a badly con- 
 structed engine, on the other hand, the force required for this 
 purpose may be very great, as in diagrams Figs. 14 and 84. 
 ii
 
 CHAPTER X. 
 
 STEAM EXPANSION CURVES OR PRESSURE OF STEAM IN 
 CYLINDER. 
 
 THE action that takes place in the cylinder of a steam-engine 
 during the period of expansion is of special importance, for the 
 purpose of comparing the various theories respecting the action 
 of the steam in an engine. The essential difference of these 
 theories consists solely in the application of several hypotheses 
 relating to the relative pressures and volumes of saturated steam. 
 The results of practice show, however, a marked discrepancy 
 between the theoretical curves of expansion and the actual ex- 
 pansion line drawn by the indicator, and I will now explain 
 how they are produced and the cause of their differences. 
 
 There are three curves of the hyperbolic form that it is neces- 
 sary to consider in comparing the lines of indicator diagrams 
 taken from steam engines. 
 
 First The curve formed when the expansion takes place by 
 the law of gases, known as either Boyle's law, or the law of 
 Mariotte, which is stated by Regnault as follows: 
 
 "The volume of a given weight of a gas, at a constant tem- 
 perature is inversely proportional to the pressure which the gas 
 sustains; or, in other terms, the densities of the gas, at the same 
 temperature, are proportional to the pressure." The theory of 
 the law is, that gas being perfectly elastic, its density must vary 
 directly, and its volume inversely, as the pressure to which it is 
 subjected. "We are accustomed," says Regnault, "to regard 
 the law of Mariotte as the mechanical expression of the perfectly 
 gaseous state." 
 
 The difference between a gas and a vapor is this: A vapor is 
 a gas near its liquefying point so that the difference is not one 
 of composition, but of condition. 
 
 Steam is a vapor, and the atmosphere is a mixture of gases. 
 It is supposed to be impossible, by any simple means now 
 
 (162)
 
 PRESSURE OF STEAM IN THE CYLINDER. 163 
 
 known, either to compress or to cool the gases which form the 
 air until they become liquid; nor can they be liquefied by both 
 pressure and cold combined; but steam would very soon become 
 liquid under either influence. 
 
 It is necessary to note this difference between gases and 
 vapors, because they behave differently under similar circum- 
 stances. 
 
 FIG. 37. 
 
 The relationship which exists between the pressure and the 
 volume of a gas as above stated was first announced, independ- 
 ently, in the latter part of the seventeenth century, by the 
 English philosopher Boyle, and by the French Abbe Mariotte, 
 namely: that if a gas (not steam, for reasons I will show pres- 
 ently) inclosed in any vessel like a steam engine cylinder with 
 a piston P (see Figure 37, where its pressure and volume can be 
 accurately observed), assume the gas against the piston P in 
 space #, to be 100 pounds per square inch, after the piston has 
 moved one fourth the length of the cylinder. Now, if the 
 piston move, as represented by /", the space a b will be filled 
 with gas of a pressure of 50 pounds, or one-half the pressure of a. 
 Again, if the piston was forced still farther, as shown by piston 
 /* 2 , the original pressure of a will be one- third, and occupy the 
 space indicated by a, b and c. And when the piston reaches the 
 end of the cylinder /**, the pressure will be one-fourth. In 
 accordance with this law a reverse condition exists when the 
 piston is forced from d to a. That is to say when the volume
 
 164 THE STEAM-ENGINE AND THE INDICATOR. 
 
 is made one-half, the pressure is doubled when the piston 
 becomes P 1 , and when it becomes P, it becomes the original 
 volume of 100 pounds pressure, the temperature of the apparatus 
 and the gas being kept the same throughout. 
 
 If the pressure and volume vary inversely (for example, if 
 when you double the one you halve the other), it is clear that 
 the two multiplied together must always be equal to a constant, 
 that is, an unchanging quantity, and accordingly Boyle's and 
 Mariotte's law is usually expressed thus: "Pressure multi- 
 plied by volume equals the constant quantity." Thus we say 
 in symbols: 
 
 P v = c. 
 
 P = The absolute pressure (measuring from the vacuum line). 
 v The volume. 
 c = The constant quantity. 
 
 The constant quantity c is known, and whatever change is 
 made in either pressure P, or volume v, will produce a change 
 in the other; namely, volume z>, or pressure P, which may be 
 found from above equation. 
 
 Example. Suppose the volume v to be five cubic feet, and 
 pressure Pto be one hundred pounds, then: 
 
 P v = loo X 5 = 500 = c. 
 
 Now let pressure P become forty pounds, then: 
 v i= 500 -f- 40 = 12.5 cubic feet. 
 
 This is a law which holds good with all gases under the fol- 
 lowing conditions: That they shall be taken at such a tempera- 
 ture and pressure, that either or both together may be vark 
 through wide limits without the gas approaching that point 
 where it begins to condense into a liquid, and that the temper- 
 ture of the gas shall be kept the same throughout the experi- 
 ment. When we work with atmospheric pressures and tem- 
 peratures, we may make wide variations, either way, with botl 
 pressure and temperature, and never come near the liquefying 
 point. But when we consider steam, we shall find that al- 
 though in practice it does so happen that when it expands the 
 pressure follows the above law, we shall also find that the tern-
 
 PRESSURE OF STEAM IN THE CYLINDER. 165 
 
 perature varies much, and consequently, if we were to put 
 steam through the same experiments as if it were a gas, we 
 should find its behavior quite different 
 
 When steam is first admitted into the cylinder at the begin- 
 ning of the stroke it comes into contact with surfaces having a 
 temperature much below its own, and a certain proportion of 
 the steam is thus condensed in raising the temperature of those 
 surfaces. So long as the inlet port is open, the steam thus con- 
 densed is made up by an additional supply from the boiler; but 
 after the cut-off has taken place, the new portions of the cylinder 
 surface exposed by the piston as it advances have to be heated 
 by the condensation of part of the steam shut into the cylinder, 
 and the consequence is that the pressure at first falls in a more 
 
 FIG. 38. 
 
 rapid ratio than that due to the expansion alone. As the ex- 
 pansion proceeds, however, and the pressure falls, the tempera- 
 ture of the steam becomes lower than that of the internal sur- 
 face of the cylinder, and then commences the re-evaporation of 
 the thin film of moisture which has been deposited on the sur- 
 face during the earlier part of the stroke. The quantity of 
 steam present being thus augmented, the pressure becomes 
 higher than that due to theory by this reboiling. The result of 
 these operations on the expansion curve drawn by the indicator 
 is to cause it at first to fall below, and subsequently to rise 
 above the theoretical expansion curve, as will be seen by the 
 above diagram (Fig. 38).
 
 i66 
 
 THE STEAM-ENGINE AND THE INDICATOR. 
 
 The theoretic expansion curve , <?, jx, , being drawn to coin- 
 cide with the expansion curve of the diagram at its commence- 
 ment from the point of cut-off , the expansion curve of diagram 
 commences at y, to rise to x, near the end of the stroke. This 
 is. due to the boiling and re-evaporation of the condensed steam 
 as the piston nears the exhausting point/ If it were not for 
 this r<?-reboiling and re-evaporation the .pressure would have 
 terminated at n. 
 
 The hyperbolic curve , x, f, g, in dotted line, was drawn to 
 coincide with the terminal prussure g, V, of the indicator dia- 
 gram. 
 
 The phenomenon of a higher terminal pressure, in cylinders 
 using steam more expansively than the law of the expansion of 
 
 FIG. 39. 
 
 gases could account for, hereafter referred to, was generally ex- 
 plained, until quite recently, by supposing that the valves 
 leaked; but when it was found to be universal, and most notice- 
 able where the steam was most saturated, thoughtful men were 
 not long in detecting the true cause. The temperature of this 
 moisture, as it enters the cylinder, is the same as that of the 
 steam, and being, in great part, relieved from pressure by the 
 expansion will instantly assume the gaseous form; provided the 
 heat (which must be rendered latent on its change of state) is 
 furnished. This heat is abstracted from the surfaces with which 
 the saturated steam comes in contact, and the excess of terminal 
 pressure above that which should exist measures ihe heat thus 
 lost, and which must be regained at the commencement of the
 
 PRESSURE OF STEAM IN THE CYLINDER. 167 
 
 next stroke from the entering steam as the piston nears the 
 exhausting point f. If it had not been for this re-boiling and 
 re-evaporation, the pressure would have terminated at n. 
 
 The indicator diagram, Fig. 39, shows the effect due to a 
 leaky piston, and exhaust-valve, the indicator expansion curve 
 falling below the hyperbola, all the way from the point of cut- 
 off e; this latter curve being drawn to coincide with the point 
 of actual cut-off. 
 
 Steam may, in driving an engine, expand under very differ- 
 ent influences according as the heat lost in working is or is not 
 returned to it, and the indicator cards that would be given are 
 known by the names respectively " Isoihermic" or Hyperbolic 
 and "Adiabatic" 
 
 When steam expands, and its temperature is maintained by 
 re-evaporation nearly the same throughout the experiment, the 
 curve formed is termed by engineers an isothermic one, signify- 
 ing equal heat But when it expands and there is no re-evapo- 
 ration, the curve becomes an adiabatic one. In an adiabatic 
 curve it is assumed that no heat is lost by the steam while do- 
 ing work, while in an isothermic curve, as already shown, the 
 lost heat is returned by the re-boiling and re-evaporation of the 
 water condensed in the cylinder after cut-offtakes place. 
 
 Therefore, when saturated steam, such as is usually generated 
 in steam boilers, expands while doing work, but meanwhile re- 
 ceiving heat, not only equal to the work performed, but suffi- 
 cient' to convert a portion of the condensed steam into saturated 
 steam by the end of the stroke, the expansion curve is isother- 
 mal or, approximately, a common hyperbola. 
 
 This is a very common case, and from the ease with which 
 calculations can be made in accordance with it, the hyperbolic 
 curve is, in practice, generally assumed for all engine diagrams, 
 and when the amount of clearance is known this curve can be 
 very readily laid down (as will be shown hereafter). 
 
 Second. The other curve, the adiabatic, is produced when 
 dry, saturated steam in a non-conducting or non-radiating 
 cylinder is expanding against pressure, or, in other words, do- 
 ing work without losing heat, in which case pressure varies 
 (according to Professor Rankine), approximately, as the recipro- 
 cal of the tenth power of the ninth root of the volume, or space 
 occupied; that is to say, in symbols:
 
 l68 THE STEAM-ENGINE AND THE INDICATOR. 
 
 P oc -v V nearly. 
 
 or more intelligibly. 
 
 P oo J V- 
 
 P = The absolute pressure of the steam. 
 v = The volume. 
 
 = Infinite, or denotes that one quantity varies as another; as P 
 varies as i. 
 
 This formula means that the absolute pressure P, existing at 
 one point of the stroke during expansion, is equal to the tenth 
 power of the ninth root of the volume v, of the cylinder, includ- 
 ing clearance at the point of cut-off, divided by the tenth power 
 of the ninth root of the corresponding volume at the point of 
 stroke in question, and multiplied by the absolute pressure P, at 
 the point of cut-off. 
 
 The above formula applies when the initial pressure is not 
 less than fifteen pounds, nor more than one hundred and eighty 
 pounds per sqnare inch. 
 
 This curve, although useful in certain theoretical investiga- 
 tions, is of little practical use, because non-conducting and non- 
 radiating cylinders do not exist. 
 
 Third When dry saturated steam expands, doing work as 
 before, but receiving meanwhile, heat to prevent liquefaction, 
 and the pressure at all points of the stroke is that due to the 
 volume and temperature of saturated steam, the pressure (ac- 
 cording to Rankine) varies nearly as the reciprocal of the sev- 
 enteenth power of the sixteenth root of the space occupied; 
 that is to say, in symbols: 
 
 P oc v }| very nearly. 
 
 This curve cannot be laid down geometrically, but this 
 equation is very convenient in calculation, because the six- 
 teenth root can be extracted with great rapidity, to a degree of 
 accuracy sufficient for practical purposes, by the aid of a table 
 of squares alone; and by a little additional labor, without any 
 table whatsoever. 
 
 "This formula has been tested for initial pressure ranging 
 from thirty to one hundred and twenty pounds to the square
 
 PRESSURE OF STEAM IX THE CYLINDER. 
 
 169 
 
 inch, and for grades or ratios of expansion varying from four to 
 sixteen." 
 
 It is found in practice that the greatest quantity of work is 
 obtained from a given quantity of heat, when sufficient heat is 
 imparted during the expansion, as in the case of steam-jacketed 
 cylinders, or superheated steam, which prevents any portion of 
 the steam in the cylinder from falling to water the fall of 
 pressure being in this case less rapid, owing to a portion of the 
 heat converted into work, being supplied by the condensation 
 of the steam in the jacket. 
 
 FIG. 40. 
 
 The Theoretical Diagram. 
 
 The diagram, Figure 40, represents a theoretical diagram 
 with expansion curves produced under the different conditions 
 before explained. 
 
 The adiabatic curve e, i, g, represents the expansion line for 
 saturated steam, dry on its admission, in a non-conducting and 
 non-radiating cylinder ; the absolute pressure varying inversely 
 as the tenth power of the ninth root of the volume, or nearly so. 
 
 This cannot, as before stated, be perfectly realized in practice ; 
 and therefore it only represents the limit which practical results 
 may approach, but cannot attain. 
 
 The curve e, 2, g, is the expansion line when saturated steam, 
 dry on its admisson and during its expansion, is prevented from 
 partially liquefying by means of a steam-jacket supplying heat 
 through the cylinder. The absolute pressure varies inversely,
 
 THE STEAM-ENGINE AND THE INDICATOR. 
 
 as the seventeenth power of the sixteenth root of the volume, or 
 nearly so. 
 
 This is, probably, the best result actually attainable in prac- 
 tice with steam that is not superheated. 
 
 The curve *?, 3, g, represents a common hyperbola, the 
 pressure varying inversely as the volume. To produce such a 
 curve the steam must contain a little absolute water on admis- 
 sion, or immediately afterward, and that water must be evap- 
 orated during the expansion by heat drawn from the cylinder. 
 This is the form of diagram, as before stated, on which calcula- 
 tions are most commonly based, and differs but little from the 
 preceding. 
 
 Therefore, in all comparisons in this series made by the use 
 of a theoretical diagram, the curve used will be that of a 
 common hyperbola. 
 
 FIG, 41. 
 
 The Theoretical Diagram. 
 
 The diagram, Fig. 41, represents the theoretical curve of 
 expansion, supposing the engine to be perfect. 
 
 The horizonal line VV of exhaust, is supposed to coincide 
 with a perfect vacimm (the barometric pressure standing 30.00). 
 The reason for this is that in inquiring into the action of ex- 
 panding steam, we must deal with the whole of the work per- 
 formed, and not with that part of it only which is utilized 
 through the piston-rod. The back pressure is a force which' 
 opposes the advance of the piston. In every diagram the total 
 amount of work done during one stroke is represented by the 
 area, not the figure usually taken by the indicator, but by one
 
 PRESSURE OF STEAM IN THE CYLINDER. 
 
 171 
 
 carried right down to the perfect vacuum line; while another 
 diagram, taken simultaneously from the exhausting side of the 
 piston, and bounded above and below by the back pressure and 
 perfect vacuum lines respectively, would represent the value of 
 the work wasted thus: 
 
 The area of Fig. 43, subtracted from Fig. 42, will give the 
 amount of work which has been utilized in a perfect non-con- 
 densing engine. 
 
 This is best understood by placing the one upon the other, 
 with the vacuum lines in contact, thus: as in Fig. 44. 
 
 The diagrams obtained in practice differ from the latter, from 
 
 FIG. 43. 
 
 the fact that diagram Fig. 43 deducted on account of back-pres- 
 sure from that of diagram Fig. 44, representing the total work, 
 is taken from the same side of the piston as the steam line, and 
 at another time; whereas the opposing force must obviously act 
 on the other side of the piston, simultaneously with the back- 
 pressure of the steam which it resists. 
 
 The included area of an indicator diagram is commonly sup- 
 posed to represent the pressure of the piston at each point of 
 the stroke. A moment's reflection will show, however, that it 
 does not. What we, for convenience, call the upper and lower 
 lines of the diagram, have, in fact, no relation to each other. 
 To get a correct idea of the nature of the diagram, we must dis-
 
 172 
 
 THE STEAM-ENGINE AND THE INDICATOR. 
 
 abuse our minds of the confused notions which result from this 
 inexact use of language. There is, in reality, no lower line 
 ever drawn by the indicator. The real lower line of the diagram 
 is always the line of perfect vacuum. During one revolution 
 the indicator draws, from opposite sides of the piston, the upper 
 
 FIG. 44. 
 
 lines of four separate diagrams, and the two which appear to- 
 gether as parts of the same outline are the ones which do not 
 belong together, having no relation to each other whatever. 
 
 FIG. 45. 
 
 IV 
 
 vl 
 
 For example: On the forward stroke a line is drawn by the 
 indicator, showing at every point the height at which the pencil 
 is raised by the pressure on that side of the piston upon which 
 the steam is admitted. Beneath this line, at the proper dis- 
 tance, let the line of perfect vacuum be drawn, and the extrem-
 
 PRESSURE OF STEAM IN THE CYLINDER. 
 
 173 
 
 ities of the two connected by lines perpendicular to the latter. 
 We have now a correct and complete diagram of the pressure on 
 that side of the piston during that stroke. 
 
 To illustrate this, we will take diagram, Fig.. 45. 
 
 The following diagram, Fig. 46, represents the pressure on 
 the acting side of the piston during the stroke when the upper 
 line of that diagram was drawn. 
 
 FIG. 46. 
 
 The lower line of diagram, Fig. 46, was commenced after the 
 upper one was finished, and is, in truth, the upper line of 
 another diagram, of which also the line of perfect vacuum is 
 the lower line, and which represents the pressure on the same 
 
 FIG. 47. 
 
 side of piston during the next stroke. Diagram, Fig. 47, drawn 
 in the manner above directed, represents this second diagram. 
 
 We say that this last diagram (Fig. 47,) represents the pres- 
 sure exerted by the exhaust steam and atmosphere to oppose the 
 return of the piston; in fact, the piston is always acted upon by
 
 174 THE STEAM-ENGINE AND THE INDICATOR. 
 
 two opposing forces, of which the difference is the motive force. 
 At every point in the motion of the piston the motive force is 
 the difference between the two opposing forces. To ascertain 
 this, we should, in this case, have the diagram representing the 
 opposing force exerted simultaneously with the force repre- 
 
 FIG. 48. 
 
 sented by diagram, Fig. 46. That would be the diagram, the 
 upper line of which was taken during the same stroke from the 
 opposite end of the cylinder. Diagram, Fig. 48, it is assumed, 
 will represent the force which was exerted in opposition to that 
 shown in diagram, Fig. 47. 
 
 Let us now place one of these over the other, their bases and 
 
 FIG. 49. 
 
 extremities coinciding, and we obtain Figure 49. So far as one 
 covers the other, the two forces neutralized each other, and may 
 be disregarded. The projecting portion A. B, e, c, of the first 
 figure, shows the force applied to the piston at each point in its 
 stroke, up to the point c, to produce its motion, and that c m
 
 PRESSURE OF STEAM IN THE CYLINDER. 175 
 
 Z?, of the second one, shows the force applied to it at each 
 point beyond c, and represents effective pressure opposing the 
 advance of the piston. The two forces, A, c, D, V, V, neu- 
 tralized each other. 
 
 Diagram Fig. 49 is the real one, as it shows the pressure act- 
 ing on each side of the piston. For computing the power ex- 
 erted by an engine, it makes no difference from which end of 
 the diagram the compression is deducted, and so, when one does 
 not care to know the effective pressure on the piston to produce 
 or to resist its motion at each point of its stroke, or the distribu-' 
 tion of force through the stroke, the diagram as produced by 
 the indicator is sufficient. But in the real diagram, Fig. 49, 
 we see in every case, at a glance, the total opposing forces. We 
 see to what extent they neutralize each other, at what point of 
 the stroke they are in equilibrium, and at every other point in 
 what degree one or the other preponderates. This diagram 
 (Fig. 49) ought, in fact, to be always drawn, for that described 
 by the indicator is liable to convey an erroneous impression re- 
 specting the distribution of force through the stroke, and by 
 this means only the truth in this respect can be clearly appre- 
 hended. 
 
 A simple and ready method of doing this is the following: 
 Lay the diagram from opposite ends on the cylinder one over 
 the other, with the atmospheric lines and extremities of the 
 diagrams coinciding, against a window-pane. Then trace on 
 the upper one with a pencil. Every diagram should be carried 
 down to the line of perfect vacuum; this will represent at a 
 glance the actual steam consumed, the quantity of heat lost by 
 conversion into forces that neutralize each other, and the pro- 
 portion which the heat so wasted bears to that which is con- 
 verted into effective work. 
 
 The Relation Between the Pressure and Volume of Satu- 
 rated Steam, as Shown by the Indicator Diagram. 
 
 Hitherto I have spoken of the expansion of air according 
 to Boyle's or Mariotte's law, as in an adiabatic curve, but in 
 applying the results of experiments on the expansion of steam 
 to a^practical use, it becomes important to regard the behavior 
 of that particular substance from another point of view.
 
 176 THE STEAM-ENGINE AND THE INDICATOR. 
 
 It has been shown that the pressure and temperature of satu- 
 rated steam rise conjointly, though not in the same degree, and 
 tables have been formed expressing the relation between the 
 pressure, volume, and temperature of saturated steam. It will 
 be borne in mind that steam in contact with the water from 
 which it is generated is called saturated steam; and further, 
 that when saturated steam at a high pressure expands while do- 
 ing work, its temperature falls, and a portion of the steam is 
 re-converted into water. Furthermore, if we operate with sat- 
 urated steam at a given temperature and endeavor to compress 
 it, we may reduce its volume, but we cannot increase its pres- 
 sure. Each temperature has its own corresponding pressure 
 (see Nystrom's "Pocket-Book of Mechanics," page 400), which 
 cannot be varied; and, as I have shown, if the volume be dimin- 
 ished while the temperature remains constant, the only result 
 will be that more and more of the steam will be re-converted 
 into water, the pressure remaining unchanged. 
 
 If the relation between the pressure and volume be plotted 
 out for any given weight of steam, we have a curve, which is 
 of great value in interpreting the diagrams given by an indi- 
 cator. It differs from Boyle's and Mariotte's curve of expan- 
 sion, it differs from the curve of expansion of superheated steam, 
 which would be that of a perfect gas; it is a curve furnished by 
 experimental data, and expresses the conditions which obtain 
 when saturated sleam changes its state of pressure, volume, 
 and temperature, without ceasing to be saturated. 
 
 The table generally used is as above stated, and has been de- 
 duced from Regnault's experiments as regards the temperature, 
 and the volume of steam of the corresponding temperature T, 
 as compared with that of water of maximum density at 40 
 Fahr., is calculated from the formula of Fairbairn and Tate. 
 The substance being saturated steam, those numbers only are 
 required for the present example: 
 
 By "specific volume," or, as it is sometimes termed, "rela- 
 tive volume," is meant the volume of the steam as compared 
 with that of the water from which it is generated; and since the 
 numbers are large, i-t is common to reduce them by increasing 
 the unit of volume fifty times. 
 
 Assuming now that we deal with a given weight of saturated
 
 PRESSURE OF STEAM IN THE CYLINDER. 
 
 I 77 
 
 steam at a steam-pressure of 40 pounds, and a volume 627.91, 
 and allow it to expand three times doing work. Therefore: 
 
 627.91 x 3 = 1883.73 volume. 
 
 From the above it is apparent that if the expansion be carried 
 TABLE NO. 5. 
 
 From Nystrom's "Pocket-Book of Mechanics," page 400. 
 
 Pressure in pounds per 
 square inch. 
 P 
 
 Temperature Fahrenheit. 
 T 
 
 Specific volume of water 
 equals i at 40. 
 V 
 
 10 
 12 
 
 13 
 14.7 
 20 
 25 
 
 30 
 
 35 
 40 
 
 193.20 
 201.90 
 205.77 
 
 2I2.OO 
 227-95 
 240.07 
 250.26 
 259.22 
 267.17 
 
 2373- 
 1994. 
 1845-5 
 1641.5 
 1219.7 
 984-23 
 826.32 
 713-8 
 627.91 
 
 to three times the original volume, the pressiire will become 
 about 13 pounds, whereas, according to Boyle's and Mariotte's 
 
 law, it should be exactly 13.33 pounds I 42. = 13.33 There 
 
 is, therefore, a small deviation from Boyle's law in the form of 
 the curve. 
 
 The point to be noticed is that the curve, when obtained, 
 represents a theoretical indicator diagram. In the present ex- 
 ample, setting out a number of intermediate points for pressures 
 at 10, 20, 30 and 40 pounds, and registering the corresponding 
 volumes, also calling 627.91 unity, we have the following dia- 
 gram, Fig. 50, where all vertical lines represent lines of pres- 
 sure, and all horizontal lines refet to volumes, and where the 
 steam is maintained in its (hypothetical) conditional state by a 
 supply of heat from without. 
 
 Let the horizontal line terminating at Vg represent the travel 
 of the piston of an engine which is supplied with saturated 
 steam at 25 pounds pressure (steam-gage), and let the pressure 
 be continued constant during one-third the stroke, as indicated 
 by B e. The steam now expands along the curved line e f #, 
 
 12
 
 I7 THE STEAM-ENGINE AND THE INDICATOR. 
 
 and its pressure falls to g y, which is a little under 12 pounds. 
 A full opening is then made to the exhaust; and if the conden- 
 sation of the steam were instantaneous and perfect, the pressure 
 would fall to zero, and would remain so during the return stroke: 
 assuming that the condensation is instantaneous, but that the 
 pressure falls only 12 pounds below the atmosphere, represented 
 by line x y, and remains constant until the piston reaches the 
 end of its stroke. 
 
 m, X- 
 
 7 
 
 
 IBV 
 
 The area A B e fg y x will represent the whole work done 
 in the double stroke, and is contrasted with the area A B e m 
 and x, which represents the work which would have been per- 
 formed by the same weight of steam if there had been condensa- 
 tion without expansion. 
 
 In 1849 Mr. C. Cowper published a complete diagram of the 
 expansion of saturated steam, ranging from a vacuum of i; 
 pounds per square inch, and up to 120 pounds boiler-pressui 
 He stated that the diagram was intended to facilitate the calcu- 
 lations of the amount of power obtained by different meth( 
 of employing steam. There were two scales namely: 
 
 First. A vertical scale of pressures from zero up to i: 
 pounds per square inch. 
 
 Second. A horizontal scale of volumes, giving the volume 
 of the same weight of steam at each different pressure as com- 
 pared with the water from which it was generated, one divisic
 
 PRESSURE OF STEAM IN THE CYLINDER. 
 
 I 79 
 
 on the scale representing 50 units of volume. The general 
 character of the diagram is shown in Fig. 51, each little square 
 being further sub-divided into twenty-five squares in the pub- 
 lished card. The dotted line represents the curve of expansion 
 from the top of the figure according to Boyle's law. 
 
 FIG. 51. 
 
 3120 
 
 As this curve is generally employed for obtaining the normal 
 or theoretical form of an indicator diagram, the following dia- 
 grams, which when rightly understood presents a summary of 
 successive improvements in the steam-engine from the atmo- 
 spheric engine to the present day. 
 
 FIGS. 52 and 53. 
 
 The shaded rectangle A D m n is the diagram of work done 
 by a given weight of steam when employed in a condensing 
 engine with steam at atmospheric pressure. The rectanglar 
 space n m V V, at the base, represents the loss by imperfect 
 condensation. 
 
 The diagram, Fig. 53, represents the work done when steam 
 at the atmospheric pressure is expanded two and one-half times 
 with condensation, as in Watt's early engines, before the em- 
 ployment of high pressure steam.
 
 i8o 
 
 THE STEAM-ENGINE AND THE INDICATOR. 
 
 This diagram Fig. 54 represents the work done by an equal 
 weight of steam at a pressure of 60 pounds, without expansion 
 and without condensation. 
 
 FIG. 54. 
 
 This diagram Fig. 55 shows a moderate expansion of steam at 
 60 pounds pressure without condensation. The expansion is in 
 this diagram carried to three volumes. The space unshaded in 
 each case represents the loss by back pressure. 
 
 FIG. 55. 
 
 Au 
 
 In this diagram Fig. 56 a steam pressure is expanded nine 
 volumes and condensed, which represents an economical engine 
 as in general use at the present time.
 
 PRESSURE OF STEAM IN THE CYLINDER. 
 
 Clearance. 
 
 181 
 
 This term includes not merely the clearance proper the 
 space between the cylinder-head and the piston at end of stroke 
 but also the space of the steam ports. By clearance is meant 
 the whole space between the piston and the valves, and is a 
 source of loss which cannot in practice be entirely avoided. It 
 is evident that this space must be filled .with steam, which ex- 
 pands, and is compressed, precisely as the rest of the steam in 
 the cylinder after the steam is cut off, and it is necessary to take 
 the cubical contents of clearance into account in ascertaining 
 the volume of steam in the cylinder. 
 
 FIG. 56. 
 
 B6Q 
 
 VIS 
 
 The Effect of Clearance. 
 
 The proportion borne by the capacity of the clearance to the 
 effective cylinder capacity, varies in different engines; it may 
 be as little as one per cent, or as much as twenty per cent. 
 The smaller the engine the greater the loss by clearance, and 
 as it always diminishes the efficiency of the engine, it should 
 be reduced to the utmost extent practicable. 
 
 One of the first things that attracts attention in analyzing an 
 indicator diagram is that the terminal pressure is usually very 
 much higher than it would be if found according to rule, by
 
 l82 THE STEAM-ENGINE AND THE INDICATOR. 
 
 dividing the initial pressure by the proportion which the stroke 
 before cut-off bears to the whole stroke. The reason is that 
 this proportion does not accurately represent the grade, or ratio 
 of expansion, for the length of the stroke, multiplied by area 
 of the cylinder, does not represent the total space finally occu- 
 pied by the steam; neither does that portion of the stroke during 
 which steam is admitted before cut-off represent the whole 
 initial volume, as the clearance space is already filled with 
 steam before the stroke commences. This steam in the clear- 
 ance expands with the admitted steam, and must be taken into 
 consideration, both before and after expansion. The total 
 initial volume will, therefore, be the steam occupying the space 
 in the cylinder passed through by the piston up to cut-off, plus 
 the steam occupying the clearance space. The final volume 
 will be the steam occupying the space passed through by the 
 piston to the end of its stroke, plus the steam occupying the 
 clearance space. The grade, or ratio of expansion, (the relation 
 between cut-off and the whole stroke,) will be the quotient 
 resulting from the division of the latter by the former; in 
 other words, the quotient resulting from the division of the 
 whole stroke, plus clearance by the stroke to apparent cut-off 
 plus clearance. 
 
 For example. The clearance space for one end of the cyl- 
 inder of diagram, Fig. 57, is, as has been shown, 0.05, or five 
 per cent, of the capacity of the cylinder. This is the product 
 of the area of the cylinder multiplyed by the whole stroke. 
 Now if the cut-off takes place at quarter stroke, the grade of 
 expansion is not i divided by 0.25 = 4, but: 
 
 1 + -5- or 1 
 
 0.25 + 0.05 0.30 
 
 It follows that the earlier the cut-off, in such a case, the 
 greater will be the relative proportion of clearance. 
 
 Thus, if the cut-off should take place at one-tenth of the 
 stroke, in the given case, the grade of expansion would not be 
 i divided by i.io = 10, but: 
 
 i + 0.05 _ i + 0.05 _ 
 0.25 + 0.05 - 0+15 ~ 7)
 
 PRESSURE OF STEAM IN THE CYLINDER. 
 
 183 
 
 and the conclusion is that when a high rate of expansion (a 
 very short cut-off) is required, the clearance must be reduced 
 to the minimum. 
 
 While, therefore, an indicator diagram accurately represents 
 by its area the work performed, and by its vertical dimensions 
 the pressure of the steam at each point of the stroke, it does not 
 accurately represent by its horizontal dimensions the volume of 
 the steam. To show this, and complete the diagram, a line 
 V B must be drawn back of the admission end of the diagram, 
 at such a distance from it as will accurately represent the clear- 
 ance space. Thus, in Fig. 57, the shaded part V B k o shows 
 clearance space. 
 
 FIG. 57. 
 
 20 18 16 14 l 2 10 P 6 4 Z O 
 
 This modification of the diagram corroborates what has 
 already been shown that the loss by clearance is greater in 
 proportion with an early, than with a late cut-off, because the 
 earlier the cut-off the greater the proportion of clearance to the 
 actual work performed. In this diagram the shaded portion is 
 clearance. 
 
 Suppose the stroke to be 20 inches, and the steam cut off 
 when the piston has moved 2 inches, from o to 2 (Fig. 57), and 
 the grade should be taken as \ - = 10. This would be incorrect, 
 for although the steam is cut-off at A of the stroke, the cylinder, 
 at the point of cut-off, contains not only a volume of steam 
 equal to A of the piston's displacement, but an additional
 
 184 THE STEAM-ENGINE AND THE INDICATOR. 
 
 volume from V to o, equal to clearance capacity. If then the 
 clearance contains & of the piston displacement, there would 
 be in the cylinder, at cut-off, a volume of steam equal to & + A 
 or & from B to *?, and the actual grade, or ratio of expansion, 
 if continued to g, the end of the stroke, instead of being 20 
 divided by 2 = 10, would be 22 divided by 4 = 5^. 
 
 With even this moderate clearance, the utmost possible prac- 
 ticable grade, or ratio of expansion, in this case, could not ex- 
 ceed ii ; that is 20 inches, plus 2 inches clearance, or 22 inches, 
 divided by 2 = u, which would be attainable if the steam 
 should be cut off immediately after the piston begins its stroke, 
 so that only the clearance space would be filled with full pres- 
 sure steam, and the entire stroke performed by and during its 
 expansion. 
 
 The expansion attainable with a given cylinder is controlled 
 by the amount of clearance, and the character of the steam in 
 it, as the expansion of steam in the clearance, unless of initial 
 pressure, lessens the actual expansion arising from a given cut- 
 off. 
 
 It is impossible, in practice, to avoid clearance altogether. 
 The capacity of ports cannot by any arrangement be reduced to 
 absolutely nothing, but loss resulting from it may be reduced, 
 if not almost entirely obviated, by closing the exhaust valve at 
 such point in the return-stroke as will cause sufficient exhaust 
 steam to be compressed, and thus fill the clearance space with 
 steam of initial pressure. Such steam acts as a constant spring, 
 giving out in its expansion the force necessary to compress it 
 again. 
 
 The smaller the clearance space the greater will be the pres- 
 sure from the closing of the exhaust valve at a given point of 
 the stroke, and the less will be the area of the cooling surface, 
 so that the gain from reducing the- clearance will be threefold. 
 
 In fast running engines the clearance space must be filled 
 with steam at the commencement of the stroke, by steam equal 
 to that of the boiler, which is obtained either from the boiler, 
 or by compressing into the clearance spaces the exhaust still re- 
 maining in the cylinder, at the closing of the exhaust-port. 
 
 By this latter process, a certain quantity of steam is saved a* 
 the expense of increased back-pressure. The total heat of the
 
 PRESSURE OF STEAM IN THE CYLINDER. 185 
 
 compressed steam increases with its pressure, and as this latter 
 approaches the boiler-pressure, the temperature of the steam, in 
 compression, must also have been raised from that of about at- 
 mospheric pressure, to nearer the temperature of the boiler 
 steam-pressure. These changes of temperature which the steam 
 undergoes, will affect the surface of the metal with which the 
 steam is in contact during the period of compression. It follows 
 from this, that the ends of the cylinder principally comprising 
 the clearance spaces, must acquire a higher temperature than 
 those parts where expansion only takes places. This is an im- 
 portant consideration, since the fresh steam from the boiler 
 comes first in contact with these spaces, and by touching sur- 
 faces which have thus been previously heated, as it were, by the 
 high temperature of the compressed steam, less heat will be ab- 
 stracted from the entering steam, and therefore a less amount 
 of water will be deposited in the cylinder. 
 
 From the above it will be seen that when the clearance is so 
 regulated that the cushion of steam at the end of the stroke 
 would attain the initial pressure of the cylinder, we may entirely 
 dispense with the consideration of clearance in calculating the 
 efficiency of an engine. 
 
 Other things being equal, the following principles always 
 hold good, and may be easily remembered: 
 
 A large clearance space requires a large ratio of compression. 
 
 An early cut-off requires a large ratio of compression. 
 
 A small clearance requires a small ratio of compression. 
 
 A late cut-off requires a small ratio of compression. 
 
 Effect of too Much Clearance on the Diagram. 
 
 The following diagram, Fig. 58, was taken from an engine 
 having a cylinder 48 inches in diameter, with a stroke of 8 feet, 
 running 15 revolutions per minute. The diagram in dotted 
 line, was taken when there was an excessive amount of clear- 
 ance, the cut-off valve being placed in the steam-pipe; therefore, 
 the steam contained in the steam-pipe and steam chest expanded 
 after the cut-off valve was closed. The effect of the extra clear- 
 ance between the slide valve and cut-off valve has raised the ex- 
 pansion curve at the point of exhaust some ten pounds above 
 vacuum line, V V. That such is the case will be seen by refer-
 
 i86 
 
 THE STEAM-ENGINE AND THE INDICATOR. 
 
 ence to the second diagram, in black lines. This diagram was 
 taken when the engine was refitted with a cut-off valve on the 
 back of the main valve, the expansion curve falling within 
 seven pounds of vacuum line by reason of the diminution of 
 clearance. 
 
 It will be observed that the pressure of steam is not the same 
 at the beginning of the stroke in the respective diagrams, nor is 
 
 FIG. 58. 
 
 K ;25 
 20 
 
 VI5 
 
 the point of cut-off exactly the same, so that the comparison is 
 not perfect; but, as before shown, clearance must be allowed for 
 in estimating the expansion curve of an indicator diagram; other- 
 wise the information given is deceptive. Another point is, that 
 excessive clearance diminishes the excellence of the vacuum, 
 by reason that the condensation is less perfect when a portion 
 of steam is stored in the passages. This is apparent from the 
 diagrams, the vacuum having improved from eight pounds in 
 the first diagram to ten pounds in the second, solely from the 
 lessening of the amount of clearance. Had there been an earlier 
 release of the steam on the exhaust side, the vacuum would have 
 been further improved, at least five per cent.
 
 PRESSURE OF STEAM IN THE CYLINDER. 
 
 I8 7 
 
 The Expansion Curve. 
 
 When steam is used expansively, in either condensing or non- 
 condensing engines, the line produced from the point where the 
 cut-off valve closes, to the end of the stroke, (if the valve is 
 properly constructed and the cylinder sufficiently protected,) 
 should be nearly a hyperbolic curve, and may be thus described. 
 
 The Mariotte, or Boyle, curve, as has previously been stated, 
 is the standard by which the character of all expansion curves 
 actually drawn by the indicator is compared, from the fact 
 that it is a determinate mathematical curve, a hyperbola. This 
 can be readily and precisely drawn, and the best curves attain- 
 able in practice coincide with it very nearly, if not exactly. 
 
 FIG. 59. 
 
 13.2 2O.9 26.4 3O.6 83.8 36.2 37.5 39.1 39.8 4Q 
 
 \ 
 
 \ 
 
 8 9 1O 
 
 The diagram, Fig. 59, has been drawn to illustrate the appli- 
 cation of this curve to the expansion of steam. The pressure is 
 represented by the vertical height, being forty pounds absolute 
 pressure to the square inch. Its length represents the stroke 
 of a piston, including clearance, divided into ten equal parts. 
 The base represents the line of perfect vacuum, assuming the 
 barometer to stand 30.75 inches of mercury, and the left-hand 
 boundary the commencement of the stroke.
 
 1 88 THE STEAM-ENGINE AND THE INDICATOR. 
 
 The diagonal of a square, drawn from the point of intersection 
 of these lines, from the commencement of the stroke and the 
 vacuum line, is the axis or centre line of every hyperbola that 
 can be described, representing expansion, (according to the law 
 of gases,) from any point of the stroke, and from any pressure 
 whatever. 
 
 Curves are described, in diagram Fig. 59, representing this 
 expansion from nine different points of cut-off. The figures at 
 the terminations of the curves give the terminal pressures, and 
 those at the commencement give the mean pressures during the 
 stroke. 
 
 Now, we assume that the steam used has an elastic force of 
 twenty-five pounds per square inch above the atmosphere. As 
 shown on a correct steam-gage, and with fifteen pounds pres- 
 sure due to the atmosphere added, this will be equal to forty 
 pounds absolute pressure. 
 
 If steam at the total pressure of forty pounds be admitted 
 into the cylinder, from o to i, a distance equal to one- tenth the 
 stroke, and then cut off, its terminal pressure will be four pounds 
 or one-tenth when the piston has moved two-tenths of the 
 stroke, or from o to 2, the pressure of the steam will be reduced 
 to eight pounds, or one-fifth. When the piston has moved 
 five-tenths (to the fifth division), it will be reduced to twenty 
 pounds, or one-half of its original pressure; if to eight-tenths, 
 to thirty-two pounds, and so on to the end of the stroke, where 
 the terminal pressure will be forty pounds, or the absolute 
 pressure at the commencement. 
 
 Now, if a line be drawn through the above mentioned several 
 points, it will represent the curve due to such a proportion of 
 cut-off; and the area described will give the average pressure 
 exerted by the steam during the stroke, as above stated. Fig. 
 59 represents such a curve, and also such other curves as would 
 have been described had the steam been cut off at either of the 
 other points. 
 
 Now we will endeavor to show how to apply a hyperbola to 
 a diagram. The hyperbola may be commenced at either end of 
 the expansion curve, but generally it will be found more ac- 
 curate to commence near the point of release. Both methods 
 will be illustrated and described geometrically.
 
 CHAPTER XI. 
 
 COMPARATIVE INDICATOR DIAGRAMS. 
 
 IN order to compare one engine with another, they should be 
 in precisely similar circumstances. As, however, this rarely 
 occurs, it is necessary to have some standard by which all 
 engines may be compared, and their relative performances 
 determined. The best means of doing this is to compare each 
 engine with a theoretically perfect engine of a similar size under 
 similar circumstances, and the engine which most nearly ap- 
 proaches the theoretical is evidently the best. 
 
 The expansion of steam, as before stated, follows a certain law 
 of gases (Boyle and Mariotte) and the quantity of steam being 
 known, as well as the space which it occupies, it is possible to 
 tell the correct pressure for each variation in the space occupied. 
 A curve can thus be calculated which will give a diagram of the 
 theoretical action of a given amount of steam in a given size of 
 cylinder. 
 
 A diagram taken from any engine may thus be compared 
 with a theoretical diagram for an equivalent quantity of steam 
 used in the same sized cylinder, and the ratio existing between 
 the actual and the theoretical diagrams will serve as a measure 
 of the perfection of the engine. 
 
 In the ordinary commercial steam engine the total clearance 
 averages not less than one-tenth (^) the piston displacement. 
 
 The following dimensions taken from an actual engine will 
 illustrate how to calculate the clearance: 
 
 Diameter of cylinder in inches, 10. 
 
 Length of stroke in inches, 20. 
 
 Clearance space between piston and cylinder cover, one-half inch, 
 or 0.5. 
 
 Dimensions of steam port and passage : 
 
 Steam port length, in inches, 10. 
 
 Width in inches, I. 
 
 (189)
 
 190 
 
 THE STEAM-ENGINE AND THE INDICATOR. 
 
 Length of steam port, in inches jrom face of valve to cylinder inlet, 12. 
 
 or 10 x i X 12. 
 
 Capacity of working part of cylinder or space swept through for 
 one stroke of the engine: 
 
 10 x 10 x 0.7854 x 20 = 1570.8 cubic inches. 
 Capacity of clearance for one end of cylinder: 
 
 10 x 10 x 0.7854 x 0.5 = 39.27 cubic inches. 
 Capacity of steam port and passage-way: 
 
 iox i X 12=1 20 cubic inches. 
 
 Total clearance for one end, 39.27 + 120 = 159.27 cubic inches. 
 Ratio of cylinder capacity to clearance: 
 
 159-27 _. oo.jo! 10. i, say ten per cent. 
 1570.8 
 
 Having determined the clearance, as above arrived at, we add 
 this length to the indicator diagram. In the present example 
 
 one-tenth has been assumed, so that the line A m in diagram, 
 Fig. 60, is one-tenth of the length of the line A D. We then 
 draw a line B C, representing the boiler pressure, which was 
 75 pounds per square inch by the steam gage, measuring from 
 the atmospheric line A Z?, with the indicator scale, which in 
 this case was 40 pounds to the inch, and also a line V Fof no 
 pressure, or perfect vacuum corresponding to the barometric
 
 COMPARATIVE INDICATOR DIAGRAMS. IQI 
 
 reading; this being as before stated 30.75 inches, corresponding 
 to 15 pounds. We then divide the length of the diagram, 
 including clearance, into ten equal spaces, or erect eleven ordi- 
 nates and number them from o to 10. We next measure the 
 pressure at the point of release /J or exhaust, which is in well 
 constructed engines usually a little say seven-hundredths (0.07) 
 of the stroke as in Fig. 60 before the end of the stroke. This 
 pressure is found by extending the expansion curve of the 
 actual diagram to the end of the stroke, fg^ Fig. 60, and meas- 
 uring the height of the extremity of the curve above vacuum 
 line VV. 
 
 Having found the terminal pressure, g V, to equal 29 pounds, 
 in Fig. 60, the pressure at any other point of the stroke is easily 
 found by the usual formula, or what is known as Boyle's or 
 Mariotte's law, according to which, as before stated, the pressure 
 of gases is inversely as the space occupied, and if, as in practice, 
 assumed applicable without qualification to steam, the expan- 
 sion curve of a diagram should be of such a shape that the pres- 
 sure represented by it at different given points would be in- 
 versely as the distance of those points from the commencement 
 of the stroke. 
 
 Thus, if at one inch from the commencement of the stroke 
 the pressure (above vacuum line) is 100 pounds, it will be 50 
 pounds at 2 inches; 33.33 at 3 inches; 25 pounds at 4 inches, 
 and so on. Hence, if the distance from any point in the expan- 
 sion curve to the clearance line B V, be multiplied by the pres- 
 sure at such point, the product will be the same wherever the 
 point be located. 
 
 This engine was regulated by a throttle valve in the steam 
 pipe, governing the amount of steam required by a Le Van 
 governor. 
 
 Diagram Fig. 60, from this engine, will illustrate the simple 
 manner in which a theoretical diagram can be constructed, as- 
 suming that the pressure of steam varies inversely as the space 
 occupied; the clearance being taken at ten per cent, of the piston 
 displacement. Assuming that the barometer stands at 30.75 
 inches of mercury, which represents a pressure of about 15 
 pounds, then measure off 15 pounds with the scale correspond- 
 ing (in this case 40 pounds equal one inch) to the indicator
 
 192 THE STEAM-ENGINE AND THE INDICATOR. 
 
 spring below the atmospheric line A D. In considering all 
 questions of expansion and compression of steam, it is the total 
 pressure, measuring from the line of no pressure V V, which 
 we must consider. 
 
 The atmospheric line, it must not be forgotten, is merely a 
 line showing what the pressure of the atmosphere happens to be 
 at the time, and the expansion curve has nothing whatever to 
 do with it. This should be well understood. 
 
 Where there are ten divisions of the diagram, as in Fig. 60, 
 the several ordinates of the expansion curve may be obtained by 
 multiplying the terminal pressure g V, by the following series 
 of numbers : 
 
 i, i. u, 1.25, 1.429, 1.667, 2, 2.5, 3.333, 5 and 10. Or more 
 simply still, by dividing the terminal pressure V, at the end 
 of the stroke, by the number of the ordinates up to the point of 
 cut-off, as follows: 
 
 In the example, diagram Fig. 60, the terminal pressure g, be- 
 ing fourteen pounds above the atmospheric line A D, and the 
 distance D V being fifteen pounds, we have 14 + 15 = 29 
 pounds terminal pressure. Now divide this terminal pressure 
 by the ninth ordinate, thus: ^ = 32.2 -pounds as the pressure 
 to lay off on space number nine; and - 2 / = 36.2 pounds to lay 
 off on space number eight, and so on for number seven, six, 
 five, four, and three. For number three the pressure becomes 
 96.7 pounds, which exceeds the boiler pressure (75 -f 15 = 90 
 pounds absolute), but we extend the ordinate to this point 
 namely, x on the diagram. 
 
 Now having found the theoretical pressure at each of the 
 several divisions of the diagram, we then trace a curve x fg 
 from x to^-. Through these points (and where the curve thus 
 found intersects the line B C of boiler pressure) is the point of 
 theoretical cut-off, E, at which the admission of steam must be 
 suppressed in our theoretical card to give the same terminal 
 pressure as in the actual card where the cut-off is at e in that 
 diagram. 
 
 On the return stroke to form the theoretical diagram complete, 
 the line D A is traced to clearance line A B, and up that to 
 boiler pressure line B C, as this engine was non-condensing. 
 Had it been a condensing engine, the return line would have
 
 COMPARATIVE INDICATOR DIAGRAMS. 193 
 
 followed the line V V, of no pressure, or absolute vacuum, and 
 up to boiler pressure. 
 
 Now we have two diagrams: the theoretical always larger 
 and enclosing the other, the actual diagram. The inner one. 
 or the real diagram, represents the work the steam actually per- 
 formed in the engine: the outer one in shaded lines is what the 
 same amount of steam should have done in a perfect engine of 
 similar capacity. The proportion which the area of the smaller 
 bears to the larger represents the relative perfection of the 
 mechanism which was used for developing the power of the 
 steam. This may be expressed in percentages of the theoretical, 
 as follows: 
 
 Take off the back pressure. In this case, 15 pounds repre- 
 sented by the space marked vacuum, bounded by A D and V V. 
 Also, leave out the first space A B p, and m y representing clear- 
 ance. Measure the other nine spaces on dotted lines as marked; 
 add up the pressures thus: 
 
 26 + 34-5 + 32.5 + 3i + 29 +26 + 22 + 18 + 13 = 232. 
 
 This sum divided by nine (the number of spaces) gives ifi = 
 25. 77 pounds for the mean effective pressure. All that part of 
 the diagram below m D, marked vacuum, is loss. This will 
 perhaps help to explain why a condensing or "low-pressure" 
 engine is more economical than a non-condensing or "high- 
 pressure" one. 
 
 Measuring the different pressures by the scale corresponding 
 to the indicator spring, they were, in the engine under consider- 
 ation, as follows: 
 
 Absolute initial pressure from line W\<Q S, 54 pounds. 
 
 Absolute terminal pressure from line^ to V, 29 pounds. 
 
 Absolute back pressure from line A D to W, 15 pounds. 
 
 Absolute average pressure from line ke f g to V V, 38.77 
 pounds. 
 
 And 38.77 15 = 23.77, actual mean pressure in pounds. 
 
 The real expansion of this card, that is, from cut-off <?, to 
 terminal point g, is f or 0.44 of total diagram. Including clear- 
 ance it is T 4 5 , or 0.4 of the actual working part of cylinder. 
 
 Now proceed to measure the theoretical diagram in the same 
 manner; add up the pressures as noted on the spaces marked 
 vacuum (see diagram, Fig. 60), and we have: 
 13
 
 194 THE STEAM-ENGINE AND THE INDICATOR. 
 
 75 + 75 + 68 + 49 + 37 + 30+ 23-5 + 19 4- 35-5 = 392. 
 
 This total, divided by nine (the number of spaces) gives 
 i2 = 43.57 pounds for the mean effective pressure. 
 
 The theoretical available mean effective pressure being greater 
 than the actual mean pressure of the engine diagram by 43. 57 
 25.77 I 7-8 pounds, the percentage of the actual to that of 
 the theoretical diagram is as follows: 
 
 % = 2 5-77 eg I A p er cent, of the theoretical diagram. 
 43-57 
 
 A good and well made modern automatic expansion engine 
 would realize ninety per cent, of the theoretical. 
 
 The Advantage of Variable Automatic Expansion. 
 
 The simplest method of ascertaining the increase of economy 
 which can be gained in an engine, under conditions of variable 
 
 FIG. 61. 
 
 automatic expansion, is to estimate what the maximum work 
 which could have been obtained from an equal amount of steam 
 used at the fullest rates of expansion would be. 
 
 This increase we can find by constructing an ideal expansion 
 diagram, which shall represent exactly the same amount of
 
 COMPARATIVE INDICATOR DIAGRAMS. 195 
 
 steam finally exhausted into the atmosphere, as in the case of 
 the actual diagram in Fig. 60, produced by the throttling 
 engine under notice. 
 
 Diagram, Fig. 61, is an ideal diagram erected from the 
 volume of steam swept through the cylinder, and calculated 
 from the terminal pressure of diagram, Fig. 60; it illustrates the 
 gain in effect if the engine had been fitted with an automatic 
 cut-off valve, in place of a throttling governor valve. The sum 
 of the pressures by the dotted ordinates is as follows: 
 
 16 + 20 + 24 + 29 + 35 + 43 + 60 + 65 + 50 = 342, 
 
 which divided by nine gives * = 38 pounds, mean pressure in 
 excess of that of the former example, Fig. 60 namely : 
 
 38 25.77 T 2-23 pounds more, mean effective pressure. 
 
 This diagram also shows an effect equal to eighty-eight and 
 four-tenths per cent., nearly, of the theoretical diagram. The 
 average mean pressure of the theoretical diagram being 43 
 pounds, and the automatic expansion diagram 38 pounds, a 
 gain of: 
 
 or a gain over the throttling engine, as per diagram, Fig. 60, of: 
 
 38- 25.77 X 'OP = 32 per cent. 
 3 8 
 
 The Further Advantage of Variable Expansion and 
 Condensing. 
 
 The secret of economy in using steam expansively in engines 
 is in the adaptation of the highest practicable pressure of steam, 
 the earliest cut-off at which the engine will do its work, and as 
 perfect condensation of steam as possible after the steam has 
 done that work. 
 
 If the engine that produced diagram, Fig. 61, had been fitted, 
 in addition, with the automatic cut-off, and a condenser, the 
 mean pressure as shown by diagram, Fig. 62, would be 49 
 pounds, as follows: 
 
 60 + 78 -f 72 + 56 + 47 + 40 + 34 + 29 + 25 = 441.
 
 196 
 
 THE STEAM-KNGINE AND THE INDICATOR. 
 
 This total, divided by nine, gives *i 49 pounds mean 
 pressure in place of 38 pounds as per diagram, Fig. 61. This 
 is a gain of ten pounds of mean effective pressure, and of 22.4 
 per cent., as follows: 
 
 49-38xioo = 22 . 4 
 49 
 
 cent. 
 
 This gain being made by removing the resistance of the 
 atmosphere. 
 
 All the above shows that the automatic engine is capable of 
 
 FIG. 62. 
 
 developing a given power at a reduction of 25 to 75 per cent., 
 as compared with the cost of power by the average throttling 
 engine. Under the most favorable conditions, the loss in 
 economy by the slide-valve throttling engine, as compared with 
 the cut-off, is nearly 30 per cent. The performance of throt- 
 tling and cut-off engines, by actual test, shows that 25 per cent. 
 is the minimum saving by automatic cut-off engines. 
 
 To the practical eye of the engineer the gain and advantages 
 are seen at a glance. In such an engine, with steam admitted 
 at nearly the boiler pressure, the duration of admission is pro- 
 portional to the resistance or load, the full initial pressure being 
 maintained to the point of cut-off.
 
 COMPARATIVE INDICATOR DIAGRAMS. 
 
 I 97 
 
 With the throttling governor, on the other hand, the boiler 
 pressure is greatly reduced in its passage from the boiler to the 
 cylinder by cramped port openings, and is "wire drawn" 
 through the governor throttle valve. In this latter fault we 
 have the explanation of the diminished efficiency of the throt- 
 tling engine, for a large portion of the work due from the 
 steam, in such an engine, is expended in getting it into the 
 cylinder, see actual diagram, Fig. 60; whereas, with an auto- 
 matic cut-off engine, in which the main valve opens for steam 
 admission directly to the cylinder, no obstruction exists to the 
 free flow from the boiler until the proper amount has been ad- 
 mitted to maintain uniform speed, see Fig. 61, when an instant 
 cut-off is effected and expansion of the enclosed steam com- 
 pletes the stroke of the piston to exhaust. This, when the 
 engine is proportioned to its work, amounts to a mere whiff. 
 
 The Theoretical Diagram: How to Construct it 
 Geometrically. 
 
 The expansion curve of a theoretical diagram may also be 
 easily drawn by finding a few points on the actual diagram by 
 geometrical construction. There are so many ways of con- 
 structing a hyperbolic curve that it is well to insert one which 
 will not confuse or put to unnecessary expense those who are 
 interested in learning how to draw it. For this purpose we 
 have taken an indicator diagram, Fig. 63, from a non-con- 
 densing engine, over which has been erected the theoretical 
 diagram as shown in shaded lines.
 
 198 
 
 THE STEAM-ENGINE AND THE INDICATOR. 
 
 First. Calculate the clearance space, as before explained; 
 then lay off the distance B p, and draw the line B V; the area 
 enclosed by B, p, m and A represents the clearance space. Also 
 draw the line V V, to represent the vacuum line parallel to the 
 atmospheric line A D, and 14.7 pounds below it. Draw the 
 line of boiler pressure B C also parallel to the atmospheric line, 
 and as many pounds above as is shown by the steam gage (as 
 before explained). 
 
 Second. Select a point f, which must not be later than the 
 commencement of exhaust opening. From f draw line f F, 
 parallel to atmospheric line, and line f 6, at right angles to it. 
 From 6 draw the diagonal line 6 V, and from its intersection 
 with or crossing the line f F, and E, erect the perpendicular 
 line E F; the point E, on line B C, is the theoretical point of 
 cut-off. 
 
 FIG. 64. 
 
 Third. Draw any desired number of vertical lines, as i, 2, 3, 
 4 and 5, downwards, from points in line B C, and from the 
 same points draw diagonal lines to point V; from the intersec- 
 tion of each of these diagonal lines, F E, draw a horizontal line 
 intersecting the vertical lines drawn from E C. These inter- 
 sections with the vertical lines locate points f, x, d, c, b and , for 
 the desired curve. 
 
 The few points being found in this way, the curve can be 
 drawn in by hand, which will be found to be a hyperbola; any 
 one familiar with the properties of conic sections will recognize 
 it as that of a rectangular hyperbola. 
 
 This curve is called the isothermal curve (signifying equal
 
 COMPARATIVE INDICATOR DIAGRAMS. 
 
 I 99 
 
 heat), because it is constructed on the assumption that the tem- 
 perature of the steam is the same at all pressures. 
 
 How to Lay Out the Hyperbolic Curve from the Point of 
 Cut-off. 
 
 In the diagram, Fig. 64, let the height/ e represent the total 
 or absolute pressure of the steam at the point of cut-off, or at 
 some point subsequent to the cut-off, if the position of the 
 latter be not accurately known. Also, let k e represent the 
 length of the cylinder filled with steam of the pressure p e; let 
 a c represent the clearance space. Then the area a, B, e, p, will 
 represent the quantity of steam to be expanded. Next, on the 
 line of perfect vacuum, V V, mark off a series of spaces, p <?, o f, 
 fi, i d, and d x, each equal to a p, and at the points o,f, z, and 
 d, erect perpendiculars, as shown. Then draw diagonal lines 
 
 FIG. 65. 
 
 from the point e to each of the points o f, t\ d, and x, and the 
 point at which each of these oblique lines intersects the perpen- 
 dicular next to that to the vacuum line of which it is drawn, is 
 the point in the desired curve. For instance, /, m, n, and^-, 
 are such points in diagram. 
 
 The curve may, of course, be extended indefinitely towards 
 the right, according to the length of stroke and degree of expan- 
 "ion.
 
 20O THE STEAM-ENGINE AND THE INDICATOR. 
 
 How to Fix the Clearance Line when not Known. 
 
 The clearance space is rarely given, and it varies in different 
 engines from one to twenty per cent, of the space swept through 
 by the piston in one stroke, as before stated. 
 
 Where the dimensions are not given, it can be computed from 
 the expansion curve as follows: 
 
 Take two points, a b, on the diagram, Fig. 65, assuming the 
 curve to be a common hyperbola. Join the points #, 3, by a 
 straight line, , #, , and x, and parallel to this line draw 
 another line through the point c. The intersection of this latter 
 line at d, with the horizontal line passing through the point a t 
 will give the distance of clearance line, B V, from diagram. 
 
 FIG. 66. 
 
 Or we may assume two points, i and 2, in the compression 
 curve, see diagram, Fig. 66, and connect them by a line, i and 
 2, and continuing this line until it intersects the line of perfect 
 vacuum, V V, at x. Draw the vertical lines, i, 5, and 2, 4, and 
 make V 5 equal to 4 x. Then erect the vertical line VB, which 
 will form the end of the theoretical diagram, including clear- 
 ance, and the distance of VB from the boundary line i k, of the 
 indicator diagram, is the clearance in the scale of the length of 
 the diagram which represents the stroke of the piston. 
 
 The Disadvantages of Too Large an Engine. 
 If an engine is too large, condensation in the cylinder takes 
 place to the fullest extent.
 
 COMPARATIVE INDICATOR DIAGRAMS, 
 
 201 
 
 The cut-off takes place early in the stroke, hence the expan- 
 sion and consequent fall of temperature are excessive. The 
 whole surface of the cylinder must be heated, and the condensed 
 steam be re-evaporated at the expense of the next admission of 
 steam. This being small in quantity, from the light load, will 
 condense very largely. With an engine suitable for the load, 
 the expansion and cooling are much less, and the amount of 
 steam admitted to restore the heat is much larger. 
 
 In the non-condensing, or "high-pressure" engine, a direct 
 loss occurs by the steam expanding below the atmospheric line, 
 thus creating a vacuum on the impelling side of the piston 
 
 FIG. 67. 
 
 which must be overcome by the momentum of the fly-wheel. 
 Diagram, Fig. 67, shows this plainly. 
 
 We have here a diagram from a steam engine for four-tenths 
 of the stroke, while for the remainder of the stroke it becomes 
 an air-pump, whose piston is dragged against 4.2 pounds re- 
 sistance per square inch (which is the average pressure of area 
 enclosed below atmospheric lines) by the momentum of the fly- 
 wheel.
 
 202 
 
 THK STEAM-ENGINE AND THE INDICATOR. 
 
 In a diagram, similar to Fig. 67, from a non-condensing 
 engine expanding below the atmospheric line, then, the pressure 
 for that part of the curve below atmospheric pressure is to be 
 considered negative, as follows: 
 
 Above the atmospheric line, 30 + 24 + 10 -j- 3 = 67 pounds. 
 
 The first four-tenths of the diagram is, as above, 67 pounds, 
 which, divided by the ten spaces, is H = 6.7 pounds. This is 
 all the forward pressure that we have; for, just at the end of the 
 fourth division or space at x, the expansion curve crosses the 
 line of counter-pressure. If we were to divide the sum of the 
 pressure by four, the number of equal divisions through which 
 the forward pressure continues, we would have a mean pressure 
 of = 16.75 pounds during that portion of the stroke. This, 
 
 FIG. 68. 
 
 however, would be of no use to us; we want to know what this 
 pressure would average, supposing it to be extended over the 
 entire stroke. We, therefore, get this by dividing the sum of 
 the mean pressure by ten, the whole number of equal divisions, 
 and the result is H = 6.7 pounds. The mean pressure to be 
 deducted from this is ascertained in a similar manner, and is as 
 follows: 
 
 Below the atmospheric line: 6 + 6 + 54-44-3 + 1 = 25 
 pounds, f$ = 2. 5 pounds mean pressure per square inch.
 
 COMPARATIVE INDICATOR DIAGRAMS. 
 
 203 
 
 Then 6.7 2.5 = 4.2 pounds effective pressure throughout 
 the forward stroke, or in other words the sum of the ordinates 
 below the back pressure line is negative, and the sum of their 
 length (2.5) must be subtracted from the sum of the positive, or 
 the length of the ordinates (6.7) above back pressure. 
 
 For the economical use of an engine its work should be such 
 that the indicator diagram would show not less than four pounds 
 terminal pressure above atmosphere. See Diagram, Fig. 68. 
 
 When the terminal pressure falls to the atmospheric line, as 
 shown in Diagram, Fig. 69, though the diagram is very correct 
 and fine in its lines, the engine is working at a loss, because 
 
 FIG. 69. 
 
 there is not sufficient steam left behind the piston to keep the 
 cylinder heated, and to furnish a cushion on the return stroke. 
 
 In fact, the actual loss is still greater than that accounted for 
 by the indicator, as the indicator does not show the friction of 
 the engine. 
 
 Diagram, Fig. 70, was taken from an automatic cut-off 
 engine; cylinder, 22 inches diameter, stroke, 44 inches; speed, 
 of piston, 520 feet per minute; scale, 40 pounds to the inch; 
 clearance, 1.75 per cent, of the space swept through by the pis- 
 ton; mean effective pressure, 36 pounds per square inch. It 
 shows very perfect performance its absolute terminal pressure 
 g V, being 22 pounds.
 
 204 
 
 THE STRAM-ENGINE AND THE INDICATOR. 
 
 Condensation in Steam-Engine Cylinders. 
 The utmost heating power of one pound of carbon is equal to 
 the evaporation of about 15 pounds of water, from a temperature 
 of 212 degrees. The quantity of heat necessary to raise the 
 temperature of one pound of water through one degree Fahren- 
 heit, is termed a "unit of heat," and as the total temperature 
 of steam is about 1178.6 degrees, or 966 degrees above the boil- 
 ing point, a pound of carbon is capable of imparting from 14,00x3 
 to 15,000 "units of heat." Different substances, however, take 
 up very different amounts of heat, and the quantity of heat 
 which would raise the temperature of one pound of water 
 
 Fie. 70. 
 
 through one degree, would raise that of nine pounds of iron to 
 the same extent. Thus, if all the heat which could be derived 
 from the combustion of one pound of coal, were imparted to 100 
 pounds of water, the elevation of the temperature of the latter 
 should be about 150 degrees. But the combustion of the same 
 weight of coal in contact with a mass of iron weighing 900 
 pounds, should raise its temperature 150 degrees, or that of 100 
 pounds of iron by 1,350 degrees. The term "specific heat" is 
 employed to express the relative capacities of bodies for absorb- 
 ing different amounts or quantities of heat at the same temper- 
 ature. Water being taken as unity or the standard of specific
 
 COMPARATIVE INDICATOR DIAGRAMS. 205 
 
 heat, that of iron is o. 14, and it may be easily ascertained by 
 experiment, that one pound of iron heated to 1,200 degrees, or 
 a bright red heat, will raise the temperature of one pound of 
 water (at say 55 degrees) by less than 130 degrees. Half a 
 pound of red-hot iron maybe cooled in a pint of water (1.08 
 pounds) without heating the latter much above blood heat. 
 
 In these facts we have the key to one of the most important 
 sources of loss in steam engines, as ordinarily worked, and they 
 enable us to comprehend why high expansive working, as com- 
 monly carried out, has given such unsatisfactory results. With 
 all our knowledge of the nature of steam, its expansion in a 
 cylinder, after the communication from the boiler has been 
 shut at one-third stroke, should afford an additional power equal 
 to the whole amount exerted up to the point of cut-off; or in 
 other words, the effect of steam should be doubled by cutting 
 off at one-third stroke. On the first admission of steam to a 
 cold cylinder, a considerable quantity is condensed into water, 
 and this is often produced to such an extent that, but for open- 
 ing the cylinder cocks, the cylinder head would be knocked off. 
 The cylinder and its attached parts in contact with the steam 
 may weigh 1,000 pounds, and may have to be raised in temper- 
 ature by 200 degrees on the average of the whole weight of 
 metal. This warming corresponds to heating 112 pounds (one- 
 ninth of looo pounds) of water through 200 degrees into steam. 
 This is about the quantity of heat ordinarily obtained from the 
 combustion of three pounds of coal, all of which, therefore, may 
 be considered as expended in warming the cylinder up to a point 
 at which high pressure steam will not condense in it. 
 
 If, now, after the cylinder had been once warmed, it would 
 retain its temperature, we might carry expansion to a high 
 pitch by cutting off at an early point of the stroke. The temper- 
 ature of the cylinder, however, is constantly varying when the 
 engine is running. Steam of 100 pounds pressure, on its ad- 
 mission to the cylinder, should heat it to its own temperature 
 of nearly 340 degrees. When, however, this steam is exhausted 
 into the air, the temperature within the cylinder falls to 212 
 degrees, and if the steam be discharged into a condenser, the 
 temperature falls to 100 degrees. Nothing is better known than 
 that the expansion and consequent rarification of steam, air and
 
 206 THE STEAM-ENGINE AND THE INDICATOR. 
 
 simple gases, is attended by cooling. Now the cylinder is not 
 heated and cooled at each stroke, to the same extent as the 
 interior space to which the steam is admitted. If it were, the 
 steam engine in its present form would be impracticable, for in 
 a fifteen-inch cylinder and thirty-inch stroke (the cylinder 
 weighing about 1,000 pounds) about three pounds of coal would 
 be expended at every stroke in warming it up from the temper- 
 ature to which it was cooled by the exhaust at the preceding 
 stroke. As it is, the inner surface of the cylinder is usually 
 cooler than the steam at the beginning of each stroke, and 
 hotter than the same steam at the end of each stroke. Experi- 
 ments have been made by placing a glass tube in communica- 
 tion with the cylinder, and at each stroke the interior of this 
 tube was covered with moisture at the beginning of the stroke, 
 while, although the steam was considerably expanded and con- 
 sequently cooled by cutting off, the tube was always dry at the 
 end of each stroke. A still more striking illustration of the 
 varying temperature of the cylinder is afforded by some of the 
 large Cornish pumping engines, to which high pressure (40 
 pounds) steam is admitted to only the upper end of a ten-foot 
 stroke. The cylinder is, of course, bored cylindrically from 
 end to end, but the top remains permanently hotter than the 
 bottom, and the difference of temperature and consequent differ- 
 ence of expansion is so great that, while the piston packing is 
 quite tight at the bottom of the stroke, it often blows steam at 
 the top. In this case, the highest temperature of the steam at 
 the top of the stroke is some 289 degrees, but as the steam is 
 expanded eight or ten fold, the bottom of the cylinder can 
 never be heated above 180 degrees, (the steam being finally dis- 
 charged into a condenser.) If steam were to be admitted also 
 at the bottom, the condensation, therefore, on the first upward 
 stroke, or until the cylinder was warmed, would be enormous. 
 We see, in a surface condenser, how instantaneously steam is 
 condensed when in contact with a cool metallic surface, and a 
 steam cylinder acts, partially, as a surface condenser at every 
 stroke of the piston. 
 
 But whatever may be the rapidity with which a cooled cast- 
 iron surface absorbs the heat of steam, by condensing that in 
 front to make room for more behind, the same cast-iron does
 
 COMPARATIVE INDICATOR DIAGRAMS. 207 
 
 not radiate its heat with the same rapidity into steam or air, 
 cooler than itself. Thus while both the steam and the cylinder 
 may be at a temperature of 300 degrees at the beginning of the 
 stroke, the latter does not fall with the former to a temperature 
 of 212 degrees, or less, at the end of the stroke. If indeed the 
 cylinder lost 10 degrees at each stroke, there would be a great 
 expenditure of fuel in keeping it up to the working temperature. 
 
 The above shows the value of short strokes and high rotative 
 speeds. It is far better to use a little steam at a time, to use it 
 very quickly, and to keep it hot. This is the fundamental prin- 
 ciple of high rotative speeds, and there is nothing more practi- 
 cally important in steam-engineering. 
 
 I have already above noted the fluctuation of temperature of 
 the interior of cylinder surfaces with each stroke with slow 
 motion. The cooling effect of the expansion penetrates further 
 into the metal of the cylinder, requiring more condensation at 
 each admission to reheat it.
 
 CHAPTER XII. 
 
 STEAM-JACKETS. 
 
 THE actual value of the steam-jacket is frequently called in 
 question, but the best engineers are unanimous in adopting it. 
 The heat abstracted from the steam-jacket transfers the lique- 
 faction from the cylinder to the jacket, and the water so formed 
 in the jacket should invariably be returned to the boiler. 
 
 Watt was the first to use the steam-jacket, but for a long time 
 its action was not clearly understood, and many engineers con- 
 sidered it an expensive and useless refinement. Nevertheless, 
 with the increasing application of high pressure and greater 
 rates of expansion, all those designers that aimed at the most 
 perfect and economical performance of the steam engine, found 
 it necessary to apply the steam-jacket. 
 
 By enclosing the cylinder in an outside jacket or envelope, 
 and keeping the space between the two filled with steam from 
 the boiler, or better still by steam from a separate boiler carry- 
 ing a high pressure, the alternate heating and cooling of the 
 cylinder will almost wholly be prevented, and the steam will 
 enter the cylinder without loss. There will then be no initial 
 condensation; and the condensation in the performance of work 
 will also be prevented, as heat will pass from the jacket to the 
 expanding steam, sufficient in many cases to keep the steam in 
 the saturated state throughout the stroke. In engines with 
 long stroke it is generally sufficient to jacket the cylinder only; 
 but in some cases the cylinder-heads are also made hollow to 
 receive steam. In marine engines', where the stroke is neces- 
 sarily short, the cylinders large, and the rate of expansion high, 
 the piston itself is formed to receive steam, as well as the heads 
 and ordinary jacket. 
 
 In practice there are three conditions of the steam cylinder in 
 the usual working of an engine, as follows: 
 
 First. The cylinder may be entirely unprotected by any 
 covering whatever. 
 
 (208)
 
 STEAM-JACKETS. 
 
 209 
 
 Second. The cylinder may be coated with felt and wood, or 
 some non-conducting material. 
 
 Third. The cylinder may be surrounded by the annular 
 space filled with steam direct from the boiler, or in other words, 
 steam-jacketed; this jacket itself being covered with a non- 
 conducting material. 
 
 It is evident, and no doubt clear to any intelligent engineer, 
 that the first mode of using steam is wrong and wasteful. Now 
 in order to impress the student with this view, I will refer him 
 to the following diagram, Fig. 71, which will give a very good 
 idea of the action of steam in an expansive engine. 
 
 The upper curve a g would be obtained by the use of a steam 
 jacket, while the lowest, eg, shows how the initial pressure is 
 lowered where there is no jacket; the middle curve, b g, shows 
 the effect of re-evaporation. 
 
 Of course, a certain quantity of heat is lost by condensation 
 
 FIG. 71. 
 
 in the jacket, but as the pressure there does not vary, and the 
 condensed water is drained off, it cannot regenerate into the state 
 of vapor, absorbing a great amount of heat, as it would do in the 
 cylinder. Thus, the heat lost in the jacket is not so great as it 
 would be if the steam were condensed in the cylinder. But 
 even supposing that the losses were equal, there would still be 
 the advantage that the/0zew of the engine would be unimpaired. 
 It is well known to all engineers that toward the end of the 
 stroke, the pressure and temperature of the expanding steam 
 having fallen considerably, the water in the cylinder, due to the
 
 2IO 
 
 THE STEAM-ENGINE AND THE INDICATOR. 
 
 above, is evaporated again, abstracting the heat from the metal 
 of the cylinder and piston. If there is no steam jacket, these 
 parts have to be heated again by the incoming fresh steam, and 
 a considerable fall of initial pressure is the result see diagram, 
 Fig. 71, at b. This effect can also be seen on any indicator 
 card, by drawing on it a theoretical expansion curve. The 
 actual curve will always be inside the theoretical diagram dur- 
 ing the first part of the expansion, while toward the end it will 
 come up to it, and may in some cases even rise above it. 
 
 One reason why engines are often not given a steam-jacket, 
 is, that it adds something to the cost of the engine; and the 
 full value of the steam-jacket has not been sufficiently known, 
 
 FIG. 72. 
 
 or understood. The whole question has been believed to be 
 one of radiation, whereas the loss is by no means measurable 
 by the loss from radiation, but is a much larger loss, and arises 
 from the fact of the inner surface of the cylinder being cooled 
 and heated by the steam at every stroke of the engine. This 
 action is clearly demonstrated by the diagrams, Figs. 72, 73, 
 74, and 75. They show the pressure really attained, together 
 with the true expansion curve for the whole quantity of steam 
 that entered the cylinder, dotted in, and which dotted curve
 
 STEAM-JACKETS. 
 
 211 
 
 would have been described, if the cylinder had been jack- 
 eted. The difference between these curves represents the 
 amount of loss from the want of the steam-jacket, and in Fig. 72 
 this loss amounts to 11.7 percent. ; in Fig. 73, to 19.66 per cent., 
 there being rather more variation of temperature in this case, 
 owing to there being more expansion. 
 
 In Fig. 74 the loss is 27. 27 per cent. ; whilst in Fig. 75 the 
 loss rises to the formidable proportions of 44. 58 per cent. This 
 
 FIG. 73- 
 
 loss is caused by the circumstance that the mass of the cylinder 
 must remain at the average temperature intermediate between 
 the highest and the lowest temperature of the steam, so that 
 when high-pressure steam, which also has a high temperature, 
 enters the cylinder, a considerable quantity of steam is at once 
 condensed, owing to the abstraction of heat by the metal, (see 
 page 209) and also to the transformation of a part of the heat into 
 mechanical power. So soon as the steam is cut off and allowed 
 to expand, it falls much more rapidly in pressure than answers 
 to its augmented volume, owing to still increased condensation, 
 more of it being condensed into water. The action of steam is 
 to heat the inner surface of the cylinder; and towards the end 
 of the stroke, when the steam is much lower in pressure, and
 
 212 
 
 THE STEAM-ENGINE AND THE INDICATOR. 
 
 consequently in temperature, than it was at first, the tempera- 
 ture of the cylinder, relatively, is sufficiently high to boil off the 
 water that was condensed from the steam as it entered the 
 cylinder; and such water becoming steam causes the pressure to 
 rise, and thus the curve approaches the true expansion cur-ve at 
 the end of the stroke. The cylinder is cooled by the loss of the 
 heat used in boiling off the water shut within it, and the cooled 
 cylinder condenses the next volume of steam that enters to per- 
 form the next stroke. Thus it follows, that without steam- 
 
 FIG. 74. 
 
 jackets a large quantity of steam passes through the cylinder in 
 the form of water, without doing work; whereas, if the cylinder 
 is steam-jacketed, no condensation takes place, and the whole 
 steam does its full duty according to the degree to which it is 
 expanded. Indeed, without steam-, or hot-air-jackets, or other 
 equivalent means of keeping up the temperature of the cylinder, 
 it will follow that the cylinder will act to some extent as a con- 
 denser at the beginning of the stroke, and as a boiler at the end 
 of the stroke. 
 
 The diagram, Fig. 76, shows the expansion curve of steam 
 in an imperfectly protected cylinder, as contrasted with the 
 true theoretical curve, which would have corresponded with
 
 STEAM-JACKETS. 
 
 213 
 
 the weight of steam found in the cylinder at the end of the 
 stroke. 
 
 In this diagram, e f g represents the actual expansion curve 
 of the steam, and a b g that which should have been the expan- 
 sion curve if the walls of the cylinder had detracted nothing 
 from the work done. The steam loses pressure on its entrance 
 by the chilling from the colder metal (see a e), and there is an 
 immediate drain upon the molecular motion within the cylinder, 
 on which we rely for the movement of the machinery outside. 
 
 FIG. 75- 
 
 The escape or loss of heat, from whatever cause it may arise, 
 is a direct subtraction from the efficiency of the work to be 
 done, and in the advanced state of the arts it can scarcely be 
 necessary to marshal all the reasons to be urged against such a 
 practice. 
 
 In the second case, where the cylinders are clothed with some 
 non-conducting material (and here it is essential to remember 
 that steam cannot expand and do work behind a piston without 
 a fall in temperature), if the steam enters the cylinder direct 
 from the boiler, as is commonly the case, it will be saturated, 
 and reduction of temperature will cause partial condensation. 
 As the expansion goes on, it appears that the temperature of
 
 214 
 
 THE STEAM-ENGINE AND THE INDICATOR. 
 
 the steam will fall below that of the surface surrounding it, and 
 toward the end of the stroke the heated metal will boil off the 
 water deposited and send it out as steam into the condenser. 
 By such an action steam will have passed through the cylinder 
 without doing work. A cylinder of metal may be covered with 
 non-conducting covering, but it is still a mass of metal, and it 
 is impossible to reason about it as if it were not alternately 
 
 FIG. 76. 
 
 heated and cooled during the running of the engine. It was 
 this alternate heating and cooling which Watt strove to elimi- 
 nate by a separate condenser and a steam-jacket. 
 
 The curve, a bg, of expansion, in diagram, Fig. 76, appears 
 to rise more than is usual toward the end of the stroke, and this 
 indicates, as clearly as if the thing were spoken in words, that 
 the steam which had been condensed by chilling is re-evapor- 
 ated by the walls of the cylinder toward the close of the stroke. 
 
 It has been found in practice that with a high grade of expan- 
 sion, and a marked difference in temperature at the beginning 
 and end of the stroke, the cylinder acts somewhat as a condensei 
 to the entering steam, and as a boiler just before it escapes. 
 
 That this is so, has been proved by an experimental trial, 
 where a glass tube, closed at one end, was fitted to the non-
 
 STEAM-JACKETS. 315 
 
 jacketed cylinder of a high-pressure engine working expan- 
 sively. It was found that the steam condensed in a cloud 
 inside the tube at the beginning of each stroke, and re-evapor- 
 ated before its conclusion. By holding a shovel of hot coals 
 near the tube, the heat effectually prevented condensation, for 
 it acted as a steam-jacket. 
 
 The point I make is, that no covering to the cylinder would 
 raise its temperature permanently to that of the entering steam, 
 for the heat deposited on condensation would not remain, but 
 would be carried away afterward, during the re-evaporation. 
 
 Third. The steam-jacket is held by quite a number of 
 engineers as a mere contrivance for keeping the cylinder warm; 
 and that while it might do this, it did it by the waste of more 
 steam than would have been wasted in the unjacketed cylinders; 
 the excess being in Tredgold's judgment, that due to the extra 
 size of the jacket over and above that of the cylinder which it 
 enveloped. 
 
 After so great an engineer as Tredgold had fallen into this 
 error, and though clear in almost every point connected with the 
 steam engine, was wrong on the steam-jacket and its office, and 
 led, from that error, to condemn Watt's use of the steam-jacket 
 as a mistake, no engineer need be ashamed to confess that he 
 does not see how a steam-jacket may be an advantage. 
 
 The steam-jacket is of especial use in the expansive engine, 
 and the greater the amount of expansion, the greater is the 
 need for and the use of the steam-jacket. 
 
 Now, for illustration, I will assume the case of an expansion, 
 non-condensing (high pressure) engine, without a steam-jacket, 
 the piston having made the forward stroke, and the pressure 
 per square inch of the exhaust being i or 2 pounds above the 
 atmosphere, and the temperature, therefore, practically that of 
 boiling water. 
 
 The metal of the cylinder walls has, so far as the interior 
 skin or surface is concerned, been cooled down to the tempera- 
 ture of the exhaust steam. In this condition of things, steam, 
 say at 100 pounds per square inch above the atmosphere, and at 
 a temperature of 338 degrees, about, is admitted from the boiler 
 into a cylinder, the walls of which are 126 degrees lower than 
 the steam. A quantity of steam sufficient to restore the heat of
 
 2l6 
 
 THE STEAM-ENGINE AND THE INDICATOR. 
 
 the walls of the cylinder must therefore be at once condensed; 
 this is done, and the condensed steam remains in the form of 
 water in the cylinder until the main slide valve has shut off 
 communication with the boiler. The steam in the cylinder 
 then begins to expand and the pressure to be reduced. The 
 water arising from the steam which was first condensed is now 
 in contact with the walls of the cylinder, which are heated to a 
 temperature of 338 degrees, due to 100 pounds pressure, while 
 the pressure in the cylinder has diminished from 100 pounds 
 gradually down to, say 10 pounds, above the atmosphere; the 
 inevitable result of this is, that the water which was first con- 
 densed becomes re-evaporated and turned into steam to be used 
 in the cylinder. It may be said that if this is so, its power, 
 which was lost in the act of condensation, will be brought back 
 again by its re-evaporation. But it must be recollected that its 
 power was lost when it was 100 pounds pressure, and that while 
 it is being re-evaporated, it is at all sorts of intermediate pres- 
 sures between 100 pounds and 10 pounds pressure. The differ- 
 ence in effect will, of course, be very great. This may be made 
 clear to the eye by constructing two diagrams. 
 
 FIG. 77. 
 
 Indicator Diagram from an Expansive Engine -with a. 
 Non-Jacketed Cylinder. 
 
 Diagram, Fig. 77, shows a card from an expansion engine 
 without a jacketed cylinder; the black lines are those made by 
 the indicator, and they would appear to represent that while m 
 greater quantity of steam than was equal to the space con-
 
 STEAM-JACKETS. 217 
 
 tained in the parallelogram, k e m n, (namely, one-fourth of the 
 stroke of the engine with a steam pressure of 100 pounds), had 
 been consumed, the work performed had been as much as was 
 equal to the area contained by the black lines, less say 2 pounds, 
 average back pressure, as indicated by the space between the 
 atmospheric line, A D, and the dotted line immediately above. 
 In fact, it would be found, if this diagram were contrasted with 
 one taken from a steam-jacketed cylinder, that the area of the 
 unjacketed diagram, representing the work done, would be 
 greater than that of the jacketed. 
 
 FIG. 78. 
 
 Indicator Diagram from an Expansive Engine with a 
 Jacketed Cylinder. 
 
 Diagram, Fig. 78, shows a card taken from a steam jacketed 
 cylinder; and if it be laid over the diagram, Fig. 77, it will be 
 found that the dotted expansion curve, e g, is lower than the 
 expansion curve, e fg. That is to say, that the height, g D, 
 of Fig. 78, is less than the height, g' g D, of Fig. 77. 
 
 Therefore, it may be said that the unjacketed engine of dia- 
 gram, Fig. 77, made a better use of the amount of steam that 
 came into the cylinder than that of the steam jacketed engine, 
 Fig. 78; but the fact is, that while in diagram, Fig. 78, the 
 parallelogram, A B e m, truly represents the quantity of TOO 
 pounds steam pressure which is delivered into that cylinder, the 
 parallelogram, k e m n, of diagram, Fig. 77, does not represent 
 it, because it does not show the actual quantity of 100 pounds 
 steam pressure which came into the cylinder, as a portion was
 
 2l8 THE STEAM-ENGINE AND THE INDICATOR. 
 
 condensed in heating up the walls of that cylinder. In order to 
 make diagram, Fig. 77, correct, there should be added to it a 
 portion, as A B k n, to show the steam condensed on its enter- 
 ing the cylinder. If this were done, it would be ascertained 
 that that steam ought to have produced, if utilized, the whole 
 of the area A B e f g' D, instead of the area k e g' D n. The 
 rise in the diagram of Fig. 77, from g to g' , represents of 
 course the re-evaporation of the condensed steam. 
 
 Now, it is upon these facts that the utility of steam-jacketed 
 cylinders is based, and it will be seen to consist in the preven- 
 tion of the condensation of high pressure steam in the cylinder, 
 and its re-evaporation in that cylinder as low pressure steam. 
 
 The steam-jacket makes the curve of pressure follow more 
 nearly the isothermal line, and so enables the engine to do a 
 larger quantity of work without sensibly increasing friction and 
 other resistance, and to use a higher rate of expansion to obtain 
 the same power, which in the case of steam implies higher 
 initial pressure, and consequently temperature of a greater fall 
 of the latter in the working substance, and hence economy. 
 
 The loss which takes place on the outside of the jacket is one 
 which may be materially diminished by proper cleading (lag- 
 ging), and is a mere loss by conduction and radiation from the 
 surface; about such as would take place from the surface of the 
 cylinder itself. It must follow, from what has been said here 
 upon steam-jacketing, that to be of use the steam in the jacket 
 should be at all times as high as the very highest steam em- 
 ployed in the cylinder; in fact, it has often been proposed in 
 large engines to jacket the cylinder with steam from a special 
 boiler kept at a higher pressure. If these facts were borne in 
 mind, we should see no more attempts at abortive steam-jacket- 
 ing, by surrounding the cylinder with steam upon the engine 
 side of the throttle-valve that is, with steam reduced by wire- 
 drawing below the boiler pressure or by jacketing with ex- 
 haust steam from the engine. 
 
 The real advantage of the steam-jacket must be sought for in 
 the fact that the condensation in the cylinder, which it is in- 
 tended to prevent, is indirectly a great source of loss. A cloud 
 or mist is produced, which is densest at the end of the stroke, 
 and during the exhaust. This removes heat from the cylinder,
 
 STEAM-JACKETS. 
 
 219 
 
 partly, perhaps, by direct conduction, but chiefly settling as 
 dew on the surface during the exhaust when the pressure is re- 
 duced. The latent heat taken up during this evaporation is 
 borrowed from the metal of the cylinder, and must be repaid by 
 the steam which enters for the next stroke, and which can ill 
 afford to be thus cooled at the outset. A certain amount of 
 alternation of temperature is a necessary consequence of expand- 
 ing under ordinary circumstances, and any cooling of the metal 
 of the cylinder which takes place during the stroke, adds, by 
 heating the steam, to the small end of the diagram; while the 
 reheating at the commencement of each stroke takes away an 
 equal portion from the other end. 
 
 FIG. 79. 
 
 The dotted line in diagram, Fig. 79, represents this action, 
 and it is evident that no great loss results so far. But any cool- 
 ing of the cylinder, which takes place during the exhaust, re- 
 quires the subtraction from the beginning of the diagram with- 
 out any corresponding compensation at the end, as I have be- 
 fore stated, and this cooling is greatly assisted by the presence 
 of moisture. It will vary in extent in different cases, being very 
 slight where the terminal pressure in the cylinder is the same 
 as the back pressure in the condenser, and increasing as the 
 difference between these increases. Where a steam-jacket is 
 used, and condensation during expansion consequently reduced 
 to almost nothing, the only source of loss of heat during the ex- 
 haust is by conduction and radiation, and it is no doubt not very 
 great; although reheating of the metal of the cylinder com- 
 mences probably very soon after the exhaust opens.
 
 220 THE STEAM-ENGINE AND THE INDICATOR. 
 
 The use of the steam-jacket has been somewhat extended of 
 late. It was originally applied to the body of the cylinder 
 only; then to the end and cover; and finally, some engineers 
 have admitted steam to the piston. This is, of course, expen- 
 sive, and involves extra joints; but it no doubt tends to 
 economy, appreciably, where the surfaces are large. It seems 
 probable, however, that more advantage accrues from the 
 steam-jacketing of one square foot of the working cylinder, 
 than of an equal area of cover or piston; since the former is 
 always kept comparatively clean by the friction of the piston, 
 while the latter surfaces soon become coated with a black car- 
 bonaceous deposit, the product of the partial decomposition of 
 the lubricants, which prevents the passage of heat to the steam 
 in the cylinder; just as in a familiar experiment, a similar 
 deposit on the bottom of a kettle protects the hand on which it 
 rests. 
 
 The practice of jacketing with exhaust steam is happily now 
 almost entirely abandoned, and it is surprising that any one 
 should have expected that steam of 220 degrees would give up 
 heat to steam of 300 degrees and onwards. It is also objection- 
 able to supply the jacket with steam which is on its way to the 
 cylinder, the result being to condense the steam partially before 
 instead of during expansion. The steam for the jacket may be 
 taken from the steam-chest, or steam-pipe, but should not be 
 returned; the condensed water should be trapped out. 
 
 Where the cylinder is covered both at its ends and sides by a 
 steam-jacket, the external casing being also protected by a 
 covering of non-conducting material, under these circumstances 
 the walls of the cylinder may be kept nearly as hot as the 
 entering steam, and the chilling effect of the metal surface is to 
 a great extent eliminated. Enough has been stated heretofore 
 to demonstrate the serious waste of heat which is inevitable 
 with even the best-constructed engines, and it is a clear advan- 
 tage to get the greatest possible amount of work out of the 
 steam just at the precise instant when it is in action. There is 
 no known material which is insensible to the action of heat; 
 that is, which cannot be warmed or cooled, and which will not 
 conduct or radiate heat. Of necessity a cylinder is made of 
 metal, a material peculiarly sensitive to changes of temperature,
 
 STEAM-JACKETS. 
 
 221 
 
 and possessing every quality, except strength, which we should 
 prefer not to find in it. It would, therefore, appear that the 
 most reasonable course would be to inclose the cylinder in a hot 
 envelope, which may serve to maintain its temperature at a high 
 point, and to supply the heat which is otherwise escaping. 
 
 FIG. 80. 
 
 Diagram Fig. 80 was taken from an engint with a steam- 
 jacket over the ends and sides, and the curve of expansion was 
 nearly that given by theory. At the end of the expansion the 
 true curve is represented by the dotted line, and it appears that 
 the actual expansion rises above it, showing that the steam was 
 a little superheated by the hot steam casing. 
 
 For the best economical running, then, it is plainly necessary 
 to prevent, as far as possible, any condensation of steam, either 
 at the period of admission or during expansion. High speed, 
 which allows but a very short time for any transfer of heat to 
 take place, is a very excellent way to lessen loss from this 
 cause; but principally may we prevent loss from condensation 
 by using a steam-jacket. When a steam-jacket is employed, 
 the cylinder is kept always at the same temperature, which is 
 at least as high as that due to the initial steam pressure. In 
 this way there is no initial condensation, nor is there any con- 
 densation during expansion, since the quantity of heat which 
 disappears by doing work is supplied by the jacket, and the steam
 
 222 THE STEAM-ENGINE AND THE INDICATOR. 
 
 is kept saturated. At the time of exhaust opening-, when con- 
 nection is made with the condenser, the steam expands as 
 before, but it is now dry, saturated steam, which receives and 
 parts with heat slowly, so that it does not abstract as much 
 heat from the cylinder when expanding into the condenser, as 
 did the wet steam in the former case. There is also no water 
 or moisture in the cylinder to be re-evaporated as soon as pres- 
 sure is relieved, and so although the steam-jacket does supply 
 enough heat to prevent liquefaction, and also heats up the 
 cylinder from the temperature due to the exhaust to that of the 
 entering steam, yet this quantity of heat is much less than that 
 which is extracted when the cylinder is unjacketed. 
 
 It is not correct to say that steam in the jacket is condensed 
 without doing any work; it does perform work, because the 
 units of heat supplied correspond to that heat which disappears 
 for the performance of work in the engine, and which causes 
 liquefaction in an unjacketed cylinder. There is also supplied 
 the quantity of heat required to make good that extracted dur- 
 ing exhaust, and which otherwise would be just so much taken 
 from the effective work of the steam in the engine. 
 
 The relative efficiency of steam, according to recent experi- 
 ments made witH engines both jacketed and unjacketed, have 
 shown a saving of 5 to 15 per cent., according to the grade or 
 ratio of expansion, in favor of jacketed cylinders, or somewhat 
 more if the heat carried away by the liquefied steam be also 
 considered. 
 
 The actual loss arising from expanding steam at high grade 
 in an unjacketed cylinder is invariably much more than 15 per 
 cent. 
 
 First. Because the expansion curve frequently rises above 
 the common hyperbola. 
 
 Second. Because the cooling during exhaust is much greater 
 than the cooling during expansion. In other words, of the 
 total quantity of heat lent the cylinder at the beginning of a 
 stroke, only a part is returned during the expansion, and the 
 remainder during the period of exhaust. 
 
 With low rates of expansion, say two or three times, it is 
 found that a moderate degree of superheating prevents very ap- 
 preciable loss, but in the absence of superheating the use of a 
 jacket is advisable.
 
 STEAM-JACKETS. 223 
 
 In all cases the jacket should be distinct from the cylinder, as 
 when the steam is passed through a jacket on its way into the 
 cylinder, the water condensed in the jacket is carried with the 
 steam into the cylinder, and the result is much the same as 
 would be produced without the jacket. 
 
 The admission of wet steam into a steam-jacketed cylinder is 
 also productive of great loss, owing to the evaporation of the 
 contained water during the stroke by heat abstracted from the 
 jacket. It is not unusual to see engine diagrams in which the 
 expansion curve rises considerably above even the hyperbolic 
 curve. In all such cases the loss must be very considerable. 
 
 It is probably chiefly owing to this source of loss that the 
 utility of the steam-jacket is so often called into question. But 
 a steam-jacket may be quite ineffectual, or somewhat worse than 
 ineffectual, if without the means of removing air and water 
 from it. 
 
 For ordinary cases we may reckon upon securing an economy 
 of ten per cent., and this with large engines, if of enough im- 
 portance to warrant the use of a steam-jacket.
 
 CHAPTER XIII. 
 
 VARIETIES OF STEAM-ENGINEa 
 
 THE steam-engine in practice assumes many different forms 
 and arrangements, each of which has a distinguishing name, 
 such as vertical, horizontal, beam, inclined, inverted, rotary, 
 etc. But these arrangements do not in any way affect the ac- 
 tion or use of the steam. It is usual, also, to divide engines 
 into two main classes: non-condensing, or "high pressure," and 
 condensing, or "low pressure," the latter being provided with 
 apparatus for condensing the steam. 
 
 Non-condensing engines are, on the whole, less economical 
 of fuel than condensing engines; but as they have fewer parts, 
 and occupy less space, they are much used where simplicity and 
 compactness are considered of more importance than economy 
 of fuel. A second mode of classing steam-engines is founded on 
 the manner in which the steam acts upon the piston, and is as 
 follows: 
 
 First. Single-acting engines, in which the steam performs its 
 work by its action on one side of the piston only. 
 
 Second. Double-acting engines, in which the steam performs 
 its work on either side of the piston alternately. 
 
 Third. Rotary engines, in which the steam drives a piston 
 revolving around the shaft. 
 
 A third mode of classification distinguishes engines into: 
 First, non-rotative, in which no continuous rotation of a shaft 
 is produced, as in single-acting pumping-engines, steam-ham- 
 mers, and direct-acting beetling-machines. Second, rotative 
 engines, in which the motion is finally communicated to a con- 
 tinuously revolving shaft. Rotative engines are now the most 
 common. Non-rotative engines are exceptional. 
 
 A fourth mode of classing engines is founded on their pur- 
 poses, as follows: First, stationary engines, such as those used 
 for pumping water, for driving manufacturing machinery, etc. 
 Second, portable engines, which can be removed from place to 
 
 (224)
 
 VARIETIES OF STEAM ENGINES. 225 
 
 place, but are stationary when at work. Third, marine engines, 
 for propelling vessels. Fourth, locomotive engines, for use on 
 railways. Stationary engines exist of all the three modes of 
 classification. Portable engines are usually non-condensing, to 
 save space and to adapt them to situations where condensing 
 water cannot be obtained in sufficient quantity. Most of them 
 are also double-acting and rotative. Marine engines are, in 
 general, condensing, double-acting, and rotative. Locomotive 
 engines are non-condensing, a few compound, and all double- 
 acting and rotative. 
 
 Condensing Engines. 
 
 Steam, the vapor of water, when produced at the usual pres- 
 sure of the atmosphere, is commonly denominated low-pressure, 
 in opposition to that which is formed at a higher pressure than 
 that of the atmosphere, and accordingly called high-pressure 
 steam. In common language, however, the term, low-pressure 
 steam, is also applied to steam which has a pressure of several 
 pounds to the square inch, and formed at a temperature higher 
 than 212 degrees. Steam-engines supplied with condensers, 
 when first made, used low-pressure steam, and, by condensing 
 the exhaust, gained the additional pressure due to the atmo- 
 sphere; were usually called low-pressure engines, instead of con- 
 densing-engines, as they should have been. In the present ad- 
 vanced state of engineering, high-pressure steam is now gen- 
 erally used in condensing engines, and to distinguish the differ- 
 ent classes they are called condensing engines, and non-condens- 
 ing engines. 
 
 Condenser. 
 
 The function of the condenser is to cool down the exhaust 
 steam so as to reduce its pressure to a minimum, and in doing 
 so the steam is converted into water. The very early engines 
 could only work by the aid of condensation, as the steam with 
 which they were supplied was generally of a lower pressure than 
 the atmosphere; it is, in fact, owing to this that the steam- 
 engine owes its birth, for steam was preferred by the early 
 mechanicians because it was so readily changed from a gas to a 
 liquid, and so produced that vacuum which Nature was sup- 
 posed to abhor, and to fill which she would do the work of 
 15
 
 226 THE STEAM-ENGINE AND THE INDICATOR. 
 
 horses. The exact relation of the condenser is better under- 
 stood by following the early history of the steam-engine from 
 the day when cooling water was admitted to the cylinder after 
 the steam, and then allowed to run freely away from the bottom 
 on the descent of the piston, to the time when Watt, having 
 perceived the waste of work in always forcing the piston up 
 against the atmospheric pressure, and in admitting the hot 
 steam into the cold cylinder, made the engine double-acting, 
 and effected the condensation in a separate chamber. The jet 
 of water continued long after Watt's time as the means of cool- 
 ing the steam, and gave in later days the distinguishing name 
 to the condenser, which is now nearly entirely suspended by a 
 more perfect apparatus. 
 
 Jet Condenser. 
 
 In a modern condensing engine, the exhaust steam has com- 
 munication from both sides of the piston, through the exhaust 
 pipes and valves, into a tight vessel or chamber, termed the 
 condenser, where the exhaust steam is condensed by being 
 intercepted by a spray or jet of cold water, which takes up the 
 sensible and latent heat in the steam, and converts it from an 
 elastic vapor to liquid water, and creates a partial vacuum (a 
 perfect vacuum is never formed in steam engine practice, 
 neither is it desirable, for the extra economy of the perfect 
 vacuum, as compared with the partial vacuum, is neutralized 
 in effect by the extra load on the air pump and diminished 
 temperature of water to the hot well). 
 
 The vacuum created in the condenser extends to the exhaust 
 end of the cylinder, and the moving piston, instead of working 
 against an atmospheric resistance of 14. 5 pounds, meets a resist- 
 ance of about 1.5 pounds, the remaining 13 pounds of atmos- 
 pheric load having been removed* by the vacuum thus formed 
 in the condenser. 
 
 The capacity of the condenser is from one-fourth to one-half 
 that of the steam cylinder. The area of the injection orifice is 
 about ^ 5 th of that of the steam piston in ordinary engines, or 
 T \th of a square inch per cubic foot of water evaporated by the 
 boiler per hour. 
 
 The temperature of the condenser is generally reduced to 100
 
 VARIETIES OF STEAM ENGINES. 22/ 
 
 degrees, consequently the vapor has an elasticity of about one 
 pound per square inch. This pressure, measured by the indi- 
 cator, is generally found to run from one to four pounds in the 
 cylinder; the latter pressure proves that the exhaust passages 
 are too small. 
 
 Sometimes, when pure water is scarce, surface-condensation is 
 employed. Here the steam passes into a number of tubes, and 
 is pumped from a vessel connecting their lower extremities by 
 means of a small air-pump. The best effects of surface-conden- 
 sation were obtained by "Joule," who passed the condensing 
 water through pipes, each of which surrounded a copper steam 
 tube. The water flowed in a direction opposite to that of the 
 steam current. He found it possible to condense 100 pounds of 
 steam per hour per square foot of tube. 
 
 In some experiments on marine engines, using surface-con- 
 densation, it was found that three to four pounds of steam per 
 hour were condensed per square foot of tube-surface; the pres- 
 sure of uncondensed steam and air being i. 7 pounds per square 
 inch. Perhaps the best results are obtained when the exhaust 
 steam is first subjected to surface-condensation, the change in 
 state being completed with the help of a small injection-jet. 
 
 With surface-condensation there is no great expenditure of 
 water, so this may be very pure when it is first put into the 
 boiler, and may be kept pure by replacing that which leaks 
 away by separate distillation. Sometimes the condensing- water 
 is also dispensed with, the surface condenser being formed of a 
 great number of tubes revolving rapidly in the air. 
 
 It has been found in practice that the best result is produced 
 by keeping the condenser at a low temperature. Even when 
 very hot feed-water is required, it is better to heat it during its 
 passage to the boiler, than to have it hot on leaving the con- 
 denser. 
 
 It has been found, that when the condenser is kept at 100 de- 
 grees Fahr. , the ratio of the amount of effective condensation to 
 the amount of water lifted by the air-pump is a maximum. 
 
 From all condensers the water must be pumped away, and it 
 is necessary for the pump to overcome the pressure of the atmo- 
 sphere. Now, when the condenser is elevated 33 feet above the 
 ordinary level, and when the water of condensation falls into a
 
 228 THE STEAM-ENGINE AND THE INDICATOR. 
 
 long pipe, the lower opening of which is beneath the surface of 
 water in a cistern, a column will always be maintained in the 
 pipe by atmospheric pressure, and the condensed water will 
 escape at the bottom into the cistern. At first sight it may 
 seem, that with this arrangement there is no loss, as in an air- 
 pump; but a little consideration will show that the engine still 
 does work in removing the condensed water. In fact, the steam 
 and the injection-water have to be raised to a height of 33 feet; 
 and in doing this, whether by creating a vacuum, or otherwise, 
 an amount of work is done which is equivalent to that done by 
 an ordinary air-pump. In the/*/ condenser, also, the air-pump 
 is dispensed with. The velocity with which steam, even when 
 at a low pressure, enters a vacuum, is taken advantage of to 
 convey the water of condensation into the hot- well. The central 
 jet of injection-water is surrounded by a nozzle for exhaust 
 steam; and the receiving-pipe gradually expands towards the 
 hot- well. This condenser is on the principle of the Giffard's 
 injector. 
 
 The area of the foot-valves varies from ^ to ^, or in pumps 
 whose buckets move very fast, to the full size of the area of the 
 opening in the bucket. 
 
 Condensers are generally provided with blow-through valves, 
 communicating with the cylinder, usually shut, but capable of 
 being occasionally opened, and with a shifting valve opening out- 
 wards to the atmosphere. Through these valves steam can be 
 blown to expel air from the cylinder and condenser before the 
 engine is set to work. 
 
 A good condenser will increase the economical power of an 
 engine from 20 to 40 per cent. , or for the same power effect a 
 corresponding saving in the amount of steam used and fuel con- 
 sumed. With an engine of any considerable size, a condenser 
 may always be employed with economical advantage, or we can, 
 when desirable, increase the power of an engine of given size 
 without adding anything to initial steam pressure, or boiler 
 capacity. Condensers owe their efficiency to the fact that they 
 create a partial vacuum on the exhaust side of the piston, and 
 thus reduce back pressure in proportion to the perfection of the 
 vacuum. Atmospheric pressure, such as non-condensing engines 
 work against, amounts to 14.7 pounds per square inch; from 10
 
 VARIETIES OF STEAM-ENGINES. 229 
 
 to 13 pounds of this may be removed by means of a condenser, 
 and is just so much added to the mean effective pressure, without 
 any additional cost, except for power required to operate the air 
 pump, which gives the injection and removes the condensed 
 steam and injection water, and as elsewhere explained, the 
 steam necessary to develop this power need not be lost when we 
 employ heaters. Since a condenser will thus add so largely to 
 the power and economy of an engine, with but slight additional 
 outlay, a condenser should always be used whenever a sufficient 
 supply of good water can be obtained for rejection. 
 
 It has been my practice to employ, whenever the conditions 
 will warrant it, an independent condensing apparatus; because 
 the vacuum is had at starting and may always be maintained, 
 regardless of the speed of the engine or varying temperatures 
 of the injection water; we can use a smaller air pump and do 
 not have to operate at all times a larger pump than necessary 
 in order to provide for emergencies; and the power required to 
 operate the pump does not act in any way to disturb the work- 
 ing of the main engine. 
 
 The amount of injection water required is from 20 to 25 times 
 the quantity fed into the boilers. Water discharged from the 
 condenser has a temperature of 100 to 120 Fahr. A portion 
 of this water may be fed into the boiler, but by far the greater 
 part has to run to waste. We may remark, in passing, that 
 this is a serious and, at present, unavoidable source of loss, 
 which is to a greater or less degree common to all steam engines. 
 In round numbers, if noo units of heat are contained in one 
 pound of steam, entering the cylinder, from 900 to 1000 of the 
 units, are carried off by the exhaust steam and imparted to the 
 condensing water. This explains why we can only realize a small 
 percentage of the power contained in each pound of coal; only 
 about 4 per cent, to 16 per cent, can be counted upon, and only 
 about 29 per cent, is possible, supposing steam of 100 pounds to 
 be expanded down to the line of perfect vacuum. The remain- 
 ing heat is necessarily lost, because there is no means by which 
 any further expansion and resulting work can be secured. But 
 while the percentage of power obtained is low, compared with 
 the power which could be realized with perfect mechanism ex- 
 tracting all the heat, yet, compared with the amount of heat
 
 23O THE STEAM-ENGINE AND THE INDICATOR. 
 
 which is possible to utilize, it may be shown that some of the 
 best types of engines yield about 50 per cent, of the highest 
 efficiency; and future improvements may be expected to in- 
 crease this figure, which is still so far below what may be con- 
 sidered attainable. 
 
 The above shows the importance of utilizing any standing 
 water in ponds or wells, in case no flowing water is obtainable. 
 Whenever the height from the surface of water in the well, 
 pond, or other body of water, from which the injection water is 
 taken, to the centre of injection pipe, does not exceed about 20 
 feet, there is no separate pump for injection water required; for 
 as a vacuum is created in the condenser, the atmospheric pres- 
 sure forces the water into the condenser, where it enters in the 
 form of fine spray. 
 
 Lifting Condensing "Water. 
 
 It is generally supposed by engineers, that there is a loss 
 of power involved in condensing water being lifted to a con- 
 denser by the action of the vacuum in the latter, or to speak 
 more correctly, by the pressure of the atmosphere on the surface 
 of the pond or well, from which the water is drawn. I find that 
 this is a subject on which some misapprehension exists, and will 
 endeavor to make the matter plain to all. 
 
 The lifting of injection water to a condenser, in the manner 
 referred to, does not involve a loss of powei. All water drawn 
 from a condenser, by an air-pump, requires as much power to 
 extract it as if this water was lifted to a height equal to that of 
 the head of water corresponding to the vacuum in the condenser, 
 and this power is unaffected by the manner in which the water 
 is supplied to the condenser. On the other hand, the resistance 
 to the water entering the condenser, must be such that the work 
 expended in overcoming it, will balance the power exerted by 
 the pump. In the majority of instances, the chief portion of the 
 work done by the entering water, is expended in overcoming 
 the frictional resistances encountered in passing the injection 
 valve or cock, rose, etc., while in cases where the injection water 
 rises to the condenser, the power corresponding to this lifting, 
 forms part of the expenditure of work, balancing the power re- 
 quired to drive the air-pump. For instance, let us suppose the
 
 VARIETIES OF STEAM ENGINES. 2$! 
 
 vacuum in a given condenser to correspond to a 28 feet head of 
 water; and let us further suppose that this condenser can be sup- 
 plied with injection water from either of two sources, one situ- 
 ated 20 feet above, and the other 20 feet below, the level at 
 which the water enters the condenser. Now, when derived from 
 the upper source, the water would enter the condenser at a rate 
 of flow corresponding to its head, as follows: 
 
 28 + 20 = 48 feet, 
 
 and the injection cock or valve would have to be set accord- 
 ingly. On the other hand, if the water was drawn from the 
 lower source, the effective head vacuum causing the flow into 
 the condenser, would be as follows: 
 
 28 20 = 8 feet, 
 
 and to obtain the same amount of injection water as before, the 
 injection cock or valve would have to be opened wider. In 
 other words, the frictional resistances offered by the injection 
 cock or valve in the two cases would be adjusted so as to 
 counter-balance the effect due to the different heights from 
 which the injection water was drawn, leaving the work to be 
 done by the air-pump constant. Of course the fall of the water 
 in the one case, and its lifting in the other, would be at- 
 tended with a rise and fall of temperature, respectively; but 
 inasmuch as the sudden arresting of a particle of water, after 
 falling 772 feet, would only cause its temperature to be raised 
 one degree Fahrenheit, the alteration of temperature, in such 
 cases as we have supposed, would be practically inappreciable. 
 
 So far we have only referred to the work done in extracting 
 water from the condenser; of course if the air-pump has to lift 
 the water after its extraction, all such lift represents extra work 
 done, as it adds to the mean effective pressure on the top of the 
 air-pump bucket. 
 
 Air-Pump. 
 
 The air-pump when single acting has a capacity usually from 
 one-fifth to one-sixth of that of the cylinder. When the air-pump 
 is double acting, it may, of course, be made one-half smaller. 
 The valves through which it draws the water, steam and air
 
 232 THE STEAM-ENGINE AND THE INDICATOR. 
 
 from the condenser, are called foot valves, those through which 
 it discharges those fluids into the hot well, delivery valves, A 
 single acting air-pump has bucket valves opening upwards in its 
 piston. Flap valves and other clacks of various forms are used 
 as air-pump valves. The ratio of the area of the valve passages 
 to that of the air-pump piston, ranges in different engines from 
 one-third to equality, being made greater, as the speed of that 
 piston is greater, so that the velocity of fluids pumped may not 
 in any case exceed about ten or twelve feet per second. 
 
 The resistance to the motion of the air-pump bucket may be 
 measured by a back pressure in the steam cylinder of from one 
 quarter to one-half pound per square inch. 
 
 The air-pump communicates with the hot well through the 
 delivery valve, and the hot well, which is a vessel generally 
 placed on the top of the condenser, communicates with the 
 waste water pipe. 
 
 The air-pump worked by the engine removes the water of 
 condensation, condensing water, air and vapor from the con- 
 denser, and delivers into a hot well, from which the water is 
 drawn to supply the boilers. 
 
 The expense of engine power in working a well proportioned 
 air-pump is trifling, and should not be considered in the selec- 
 tion of condensing apparatus. In adapting engines for maximum 
 economy, care should be had that the terminal pressure, or 
 pressure at release, should never fall below atmospheric pres- 
 sure, otherwise the vacuum will be but partially utilized. 
 
 High-Pressure Steam. 
 
 Hornblower invented the double or compound cylinder en- 
 gine for expansive working, and he intended (as did Watt in 
 his patent of 1782), to employ steam at or near the atmospheric 
 pressure. To Oliver Evans must be 'awarded the credit of hav- 
 ing built and put in operation the first practically useful high- 
 pressure steam-engine, using steam at 100 pounds pressure to 
 the square inch, or more, and dispensing with the complicated 
 condensing apparatus of Watt. The high-pressure engine of 
 Evans had advantages in its great simplicity and cheapness, and 
 ever since his day it has continued the standard steam engine 
 for manufacturing purposes in this country.
 
 VARIETIES OF STEAM ENGINES. 233 
 
 The economy resulting from the expansion of steam at a high 
 pressure was, however, first insisted upon by Arthur Woolf, a 
 Cornishman, who converted Hornblower's double cylinder en- 
 gine into a form suitable for driving machinery, for which he 
 took out a patent in 1804 (No. 2,772) for certain improvements 
 in the construction of steam engines, in which he proposed to 
 employ two steam cylinders of different dimensions, each furn- 
 ished with a piston, the smaller cylinder having a communica- 
 tion at the top and bottom with the boiler, but communicating 
 also with the two ends of the larger cylinder, in such a way that 
 the steam should cause both pistons to rise and fall together. 
 
 The specification describes the admission of steam at a pres- 
 sure of 40 pounds on the square inch into the smaller cylinder, 
 so as to drive the piston down at the same time that steam from 
 below the same piston is expanding into the larger cylinder, 
 and forcing its piston also in the same direction. 
 
 Hence, the two pistons are similarly actuated by the joint 
 pressure of the steam in each cylinder. Woolf was here adopt- 
 ing Hornblower's engine to a new purpose. Woolf erected one 
 of his engines working with high-pressure steam and condensa- 
 tion at Meux's brewery in 1806. Woolf entertained the most 
 fanciful and enormous ideas as to the power of high-pressure 
 steam when expanded, but, although quite wrong in his theory, 
 he persevered in the construction of his engines, and erected sev- 
 eral which ran with a steam pressure of from 40 to 60 pounds 
 above the atmospheric pressure. 
 
 Although Woolf had peculiar theories, he was a thoroughly 
 practical mechanic, and performed more admirable work in the 
 construction of high-pressure engines, and in advocating tubular 
 boilers for the generation of high-pressure steam. 
 
 Down to the year 1814 the pressure of steam in Cornish 
 engines never greatly exceeded that of the atmosphere, and at 
 this low initial pressure there was practically but little economy 
 resulting from expansive working; whereby it appears that 
 after Watt's immediate connection with the mining districts 
 ceased, expansion fell rapidly into neglect. Then it was Evans 
 in America, R. Trevethick and Woolf in England; the latter 
 both advocated in Cornwall the economy of high pressure steam 
 with expansion, a mode of working which was applied by
 
 234 THE STEAM-ENGINE AND THE INDICATOR. 
 
 Hornblower, in Watt's single cylinder engine, and by Woolf in 
 the double cylinder engine. 
 
 It was, indeed, proved that by high pressure of steam and 
 expanding by the new method, it was possible to raise the duty 
 of an engine from twenty million of foot pounds for one bushel 
 of coal, at which point Watt had left it, to fifty or sixty million, 
 and at the present day as high as one hundred million foot 
 pounds. 
 
 Up to 1850 marine engines were run at a pressure on the 
 boiler from 5 to 15 pounds above the atmosphere. Within the 
 last twenty years, however, a great change has occurred in the 
 construction of both marine and stationary engines. The 
 ordinary boiler pressure now runs from 80 to 160 pounds per 
 square inch. It is an everyday occurrence for a stationary 
 engine to develop a horse-power per hour with a consumption 
 of three pounds of coal, and compound marine engines with two 
 pounds. 
 
 Comparative Efficiency of Different Engines. 
 
 I shall discuss the performance of steam-engines by reference 
 to the indicator diagrams taken from them, and shall commence 
 with the atmospheric engine of Newcomen, as his was the first 
 that was considered a steam-engine. The apparatus of Savery 
 was not what would be called to-day a steam-engine, as it had 
 no moving parts, but consisted of either a single pair of closed 
 vessels or three vessels, one of which was a boiler, and the other 
 or others, metal chambers of spherical, cylindrical or ellipsoidal 
 form, which were at once condensers and pumps. The latter 
 were filled with steam, which being condensed, the water rose 
 into and filled them, and was then forced out by a succeeding 
 charge of steam, of pressure exceeding that of the head against 
 which the lift took place. The usual pressure was about (45) 
 forty-five pounds per square inch, and the consumption of coal 
 amounted to about thirty pounds of coal per hour, per horse- 
 power, as a minimum. 
 
 The "Atmospheric Steam-Engine" consisted of a steam 
 cylinder, with a piston taking steam at the bottom; the upper 
 end of the cylinder being open to the atmosphere, the piston 
 actuating a "walking-beam," and, through the latter, working
 
 VARIETIES OF STEAM ENGINES. 
 
 235 
 
 pumps attached to the opposite end. Neither crank, shaft, nor 
 fly-wheel was used, the action of the engine being controlled 
 entirely by the adjustment of its valves. In its operation, steam 
 at a little higher than atmospheric pressure, was admitted below 
 the piston ; the weight at the pump end depressed that extremity 
 of the beam, raising the piston. The steam below the piston 
 was then condensed by a jet of water thrown into the cylinder, 
 producing a vacuum, and atmospheric pressure finally forced 
 the piston down, raising the pump-rod and plunger. The 
 weight on the latter was adjusted to the work, so that, when 
 steam was admitted, this weight should force the pumps to dis- 
 charge the water. The only function of the steam was the dis- 
 placement of the atmosphere, or counterbalancing it, by entering 
 below the piston, and thus permitting the formation of a vacuum. 
 The coal consumption was, at best, about twenty pounds per 
 hour per horse-power. 
 
 FIG. 81. 
 
 O A 
 
 6 
 
 10 
 
 14.7_ V 
 
 13 
 
 12.5 
 
 12 
 
 10 
 
 In the diagram, Fig. 81, the steam pressure never rises above 
 the atmospheric line A D, the horizontal lines represent vol- 
 umes occupied by steam in the cylinder, otherwise the amount 
 of travel of the piston, for one stroke is identical with the other. 
 The diagram being intersected by ten vertical lines at equal dis- 
 tances, dividing the length of stroke into ten equal parts, the 
 first thing to be done is to determine the mean pressure of the 
 steam in each of these divisions. 
 
 The action of the steam is quite intelligible. The pressure is 
 maintained during the upward stroke, but there is a loss at the
 
 236 THE STEAM-ENGINE AND THE INDICATOR. 
 
 beginning due to the injection water, which remains in the 
 cylinder. On the downward stroke the condensation is imper- 
 fect at first, but improves afterwards, and the pressure of vapor 
 in the cylinder falls to two and one-half pounds, or five inches 
 of vacuum. 
 
 Now, by adding the number of pounds pressure at each divis- 
 ion together, we find that the sum is 
 
 15 + 13 + X 3 + J 3 + I2 -5 4- 12.5 + 12 + ii + 10 + 5 = 115, 
 
 which, when divided by ten, gives 11.4 as the mean effective 
 pressure on the piston in pounds per square inch during one 
 stroke. The dimensions of the engine and rate at which the 
 piston moves are now to be taken into account. The cylinder 
 of this engine was 80 inches in diameter and ten feet stroke, and 
 the number of strokes ten per minute; hence; 
 
 Area of piston = 80 x 80 x 0.7854 5026.5 square inches. 
 Travel of piston, per minute, 10 x 10 = 100 feet. 
 
 Indicated horse-power = 5 26 ' 5 x I0 x "' 5 = 175 horse-power. 
 
 Single Acting Engines. 
 
 The best type of a single acting engine is the Cornish pump- 
 ing engine, as invented by Watt in 1778. In this class of 
 engine there is always steam above the piston, and steam and 
 vacuum alternately beneath; but about the year 1780 it occurred 
 to Watt that the condensation might be made more perfect, and 
 a better result be realized, if these conditions were reversed, and 
 a perfect vacuum maintained beneath the piston, while an 
 alternate steam pressure and vacuum was used above it. When 
 the engine is applied to work a common pump, the force being 
 needed only when the pump buckets are raised, not in their 
 descent, an arrangement was required in the cylinder by which 
 the piston should be only driven by steam in its descent, the 
 pump buckets being then raised by the other end of the beam; 
 but in its ascent the piston would be lifted by the weight of the 
 descending buckets, without any aid from the steam. Engines 
 adapted to work pumps are therefore so arranged that the valve 
 shall only admit steam above the piston, a vacuum being made
 
 VARIETIES OF STEAM ENGINES. 237 
 
 below it in the descent. Engines constructed in this manner 
 are called single acting engines, while those in which the steam 
 acts both above and below the piston are called double acting 
 engines. 
 
 The single acting engine in its principle differs in no respect 
 from those I have described. A valve is provided at the top of 
 the cylinder by which steam is admitted above the piston when 
 it begins to descend. Another valve is provided at the bottom, 
 by which the steam under the piston passes to the condenser; 
 and the piston descends exactly in the same manner as in the 
 double acting engine. But when the piston has reached the 
 bottom of the cylinder, a valve is opened which gives a com- 
 munication between the top and the bottom of the cylinder, so 
 that the steam which has just forced the piston down now 
 passes equally above and below it, the piston being then drawn 
 up by the weight of the descending buckets. The steam which 
 was above it passes below it, through a tube attached in which 
 the valve just mentioned, communicating between the top and 
 bottom of the cylinder, is placed. When the piston has reached 
 the top of the cylinder, the steam which previously filled the 
 cylinder above the piston will now fill it below the piston ; and 
 when the piston .is about to descend by the pressure of steam 
 admitted above it, the steam below it is discharged to the con- 
 denser by another valve already mentioned, and so the opera- 
 tion proceeds. 
 
 Single acting engines are only applicable to pumping or to 
 some other operation in which an intermitting force, acting in 
 one direction, is required. 
 
 The most remarkable examples of the application of the 
 single acting steam-engines to pumping are presented in the 
 mining districts of Cornwall in England, where engines con- 
 structed on an enormous scale are applied to the drainage of 
 mines. The largest steam-engines in the world are used for this 
 purpose. Cylinders eight and nine feet in diameter are not 
 unknown. The expansive principle may here be applied with- 
 out limit, inasmuch as regularity of motion is not necessary. 
 Steam of fifty pounds per square inch above the atmosphere is 
 admitted to act on the piston, and cut off after performing from 
 i to T J 2 of the stroke, the remainder of the stroke being effected 
 by the expansion alone of the steam.
 
 2 3 8 
 
 THE STEAM-ENGINE AND THE INDICATOR. 
 
 Double acting engines are only applicable in pumping by the 
 use of doable-acting pumps. 
 
 The following indicator diagram, Fig. 82, was taken from a 
 single acting engine, or Cornish pumping engine, having a 
 
 FIG. 82. 
 
 cylinder 70 inches in diameter, making four strokes per minute, 
 under a mean pressure of fourteen and three tenths pounds per 
 square inch. 
 
 In the single acting engines two diagrams must be taken, one 
 from the top and the other from the bottom of the cylinder. It 
 will be seen that these diagrams are quite unlike in form, for 
 the action during the down-stroke is not repeated during the 
 up-stroke as in a double acting engine, and our first task will be 
 to comprehend the reasons of the particular conformation ob- 
 served. Each diagram must be interpreted in its turn. 
 
 FIG. 83. 
 
 As far as the upper diagram is concerned, that figure indicates 
 the admission and cut-off of steam, together with the opening 
 of the equilibrium valve, which corresponds to an ordinary dia- 
 gram from a condensing engine. The lower diagram, Fig. 83, 
 has reference to the state of things below the piston, where the 
 equilibrium and exhaust valves are opened consecutively.
 
 VARIETIES OF STEAM ENGINES. 339 
 
 Beginning at the point i with the piston at rest at the top of 
 the cylinder, we note that the pressure rises until the down- 
 stroke commences, when the steam line k e, and the expansion 
 e g, is traced out. The portion k e is horizontal, and cut-off 
 takes place at e. The line ap indicates that the equilibrium 
 valve is open, and that the steam pressure has fallen somewhat 
 during the circulation which takes place. At the point p the 
 equilibrium valve is closed, and compression or cushioning be- 
 gins, just as in a double acting engine. At the point i the pis- 
 ton is coming to rest, and there is a drop in the curve which is 
 often much more marked than in the present example, and 
 which indicates loss of pressure before the down-stroke begins. 
 Such loss would be due to leakage of the compressed steam 
 round the circumference of the piston, or perhaps to loss of heat. 
 
 As to the lower diagram, the nearly horizontal line, a p, shows 
 that the equilibrium valve is opened. When compression be- 
 gins at^i, above the piston, expansion will also begin to a much 
 less extent below it, and there will be a slight drop towards the 
 end of a p, otherwise the lines a p and a nearly coincide, and 
 would absolutely if there were no disturbing causes at work; but 
 the diagram shows some difference of pressure at the two ends 
 of the cylinder, when the equilibrium valve is open. 
 
 With regard to the work done, the piston is driven down by 
 the steam from above it, as opposed by the back pressure of the 
 exhaust space underneath, and that part of the action is fully 
 determined by comparison of the lines, k e, g and a p. But the 
 whole work done by the steam in the double stroke is, accord- 
 ing to our principles, obtained by a careful measurement of the 
 areas of the enclosed diagrams. 
 
 At first sight the student might imagine that the horse-power 
 may be calculated by simply noting the pressures indicated by 
 the steam and exhaust lines, the cutting away of any part of 
 the intermediate area as by compression, or by want of coinci- 
 dence of the lines ap and a affecting only the up-stroke, when 
 the weight of the pump rods is the moving force. But a little 
 consideration will show that this view is erroneous, and that the 
 compression of steam in the up-stroke, and the resistance to the 
 motion of the piston due to inequality of pressure when the 
 equilibrium valve is open, must be deducted from the total
 
 240 THE STEAM-ENGINE AND THE INDICATOR. 
 
 efficiency. The steam opposes the piston in its ascent, to some 
 degree, and this gives rise to negative work, which must be de- 
 ducted from the positive work accomplished in the down-stroke. 
 In other words, during the down-stroke the steam does the 
 work, and during the up-stroke work is done upon the steam. 
 
 It follows, therefore, that the portion of unoccupied space be- 
 tween the two intermediate horizontal lines is a veritable sub- 
 traction from the efficiency of the agent. 
 
 To calculate the horse-power in the case of a single acting 
 pumping-engine, having a cylinder 100 inches diameter with a 
 stroke of 10 feet, and making eight strokes per minute. 
 
 Taking the steam pressures as noted on the diagram Fig. 82 
 in their order, there is above the atmospheric line a series 
 amounting to 
 
 Above the atmosphere: 
 
 20 + 20 + 14 + 8 + 4 + i = 67 
 Below the atmosphere: 
 
 3 + 6 + 6 + 6 + 6 + 6 + 5-^4 + 3 + 2 = 47 
 Lower diagram : 
 
 2-5 + 3 + 3 + 3 + 3 + 3 + 3 + 3 + 3 + 2 -5 = 29 
 Total 143 
 
 This total divided by the ten ordinates = ^ = 14.3 pounds aver- 
 
 10 
 age pressure. 
 
 HP = -7854 X ICQ + IPO + io + 2 + 8 + 14.3 _ Hp 
 
 33000 
 
 Double-Acting Engines. 
 
 When steam acts on both sides of the piston alternately, the 
 engine is called double-acting. In fact, it is only in rare cases 
 that a single-acting steam-engine is now used. Gas engines are 
 single-acting. 
 
 In the following Fig. 84, diagram K, was taken from a 
 double-acting engine, with steam at atmospheric pressure only. 
 
 This engine had a cylinder 36 inches diameter, and a stroke 
 of 5 feet. 
 
 The vacuum gage attached to the condenser exhibited a con- 
 stant vacuum of about 28 inches, or 14 pounds, and it was
 
 VARIETIES OF STEAM ENGINES. 241 
 
 thought to be doing good duty; but on the application of the 
 indicator, it was found that the average vacuum acting upon 
 the piston was not over 17%! inches. 
 
 By resetting the valves, and giving a little lead to them, also 
 cutting off after the piston had moved ^ths of the stroke, and 
 increasing the steam to one pound above the atmosphere, to 
 compensate in part for this loss of power due to cutting off, a 
 much superior vacuum was produced, and the power of the en- 
 gine increased with a saving in fuel of about a ton of coal per 
 day. See diagram //'in shaded lines, Fig. 84. 
 
 FIG. 84. 
 
 The diagram, Fig. 85, was taken from a condensing-engine, 
 some thirty years ago, and will give an idea of a first-class en- 
 gine, working und^r a steam-pressure of from five to seven 
 pounds per square inch above the atmosphere. 
 
 The engine had a cylinder 80 inches diameter, with a stroke 
 of 6 feet, making fifteen revolutions per minute. 
 
 The steam pressures above the atmospheric line at the differ- 
 ent spaces are as follows: 
 
 5-5 + 5 + 5 + 5 + 4-5 + 4-5 4- 3 + 2 + I = 35-5- 
 The pressures due to vacuum are as follows: 
 
 II + 12 + 12.5 + 12.5+ 12.5 + 12 + 12 + 12+ 12 + 8= II6.5 
 
 Total 152.0 
 
 16
 
 242 
 
 THE STEAM-ENGINE AND THE INDICATOR. 
 
 Mean pressure, 152 H- 10 = 15.2 pounds. 
 _ 80 x 80 x .7854 x 6 x 2 X 15 X 
 
 15-2 _ 
 
 33,000 
 
 = 416.48 HP 
 
 Automatic Steam-Engines. 
 
 Within the last few years variable cut-off engines for station- 
 ary uses are the rule and not the exception. The fundamental 
 idea upon which this class of engines are designed is that of 
 variable expansion. 
 
 The following are the most prominent in general use in the 
 United States: The Corliss, Greene, Buckeye, Porter- Allen, 
 Straight Line, etc., etc. Engines of this class have no regulat- 
 ing valve, but full boiler pressure is maintained in the valve 
 
 FIG. 85. 
 
 chest, and admitted to the cylinder at the commencement of 
 each stroke, and the governor adjusts the force to the varying 
 resistance, acting directly on the main valves, and changing 
 the point of cut off. The action of the regulating valve raises 
 or lowers the steam line on the diagram, while that of the vari- 
 able cut-off lengthens or shortens it, as the load on the engine 
 is increased or diminished. 
 
 The object of using steam expansively is to obtain a high 
 mean pressure throughout the stroke with a low terminal pres- 
 sure, on the assumption that while the former represents the 
 work done, the latter represents the quantity of steam expended 
 in doing it. 
 
 It is readily demonstrated and abundantly proved in practice, 
 that the greatest difference between the mean pressure in the 
 cylinder through the stroke and that at the the end of the stroke,
 
 VARIETIES OF STEAM ENGINES. 343 
 
 or at the point of exhaust, is obtained by admitting the highest 
 attainable pressure at the very commencement of the stroke, 
 maintaining it up to the point of cut-off, cutting off early and 
 sharply, and permitting the enclosed steam to exert its expan- 
 sive force to the end of the stroke. Theoretically, the earlier 
 the cut-off, and the further expansion is carried, the better; but 
 this is greatly modified by various practical considerations. 
 
 It is well known that steam-engines in which uniformity of 
 speed is maintained by variable cut-off, under the direct control 
 of the governor, are, other things being equal, superior in point 
 of economy in the use of steam to similar engines which are 
 regulated by a throttle valve in the steam-pipe throttling 
 engines, so called; and that engines of the first mentioned class 
 also possess much greater efficiency with the same capacity of 
 cylinder, than engines of any other class. 
 
 To the practiced eye of the engineer these qualities are 
 revealed by a glance at the indicator diagram. 
 
 It is seen that with the variable cut-off, steam is admitted to 
 the cylinder at very nearly the full boiler pressure, and the du- 
 ration of admission is proportioned to the resistance, or work, 
 and controlled by the governor, and speed. 
 
 With the throttle- valve, on the other hand, the pressure is 
 greatly reduced in its passage from the boiler to the cylinder, 
 during regular, ordinary work; admitted at higher than the 
 ordinary pressure, for increase of resistance or work, by the 
 slow-moving governor, and reduced to still more attenuated 
 pressure for any decrease of resistance by the more rapidly re- 
 volving governor. 
 
 It will readily be seen that we have in this reduced pressure 
 an explanation of diminished power, or efficiency, of the throt- 
 tled engine with given capacity of cylinder, speed of piston, and 
 steam pressure in the boiler. 
 
 Other causes, some of which will be noticed further on, con- 
 spire with this to the same result; and all these causes, while 
 they promote efficiency, also promote economy, as will be seen 
 from an analysis of indicator diagrams from each style of en- 
 gine.
 
 244 TH E STEAM-ENGINE AND THE INDICATOR. 
 
 Economy in Using Steam Expansively. 
 
 The secret of economy in using steam expansively in engines 
 is in the adoption of the highest practicable pressure of steam; 
 thorough jacketing about the cylinders, steam-pipes, and valve- 
 chests, the earliest cut-off at which the engine will do its work, 
 and as perfect condensation of steam as possible after the steam 
 has done that work. The steam should have the readiest pos- 
 sible access to the cylinder, and the only principle upon which 
 any valve, however ingenious, can work successfully, is that of 
 providing a large opening immediately at the commencement 
 of the stroke, with prompt cut-off at whatever point may be 
 determined upon, and in early and unobstructed exhaust. 
 
 No steam-engine can run economically at a high grade of ex- 
 pansion, except it be fitted with a condenser, for the greatest 
 economy of working expansively is in expanding below the 
 pressure of the atmosphere. The highest attainable economy 
 would be in expanding down to a perfect vacuum, thereby re- 
 lieving the boiler from overcoming the pressure of the atmos- 
 phere at each half revolution of the engine, as is the case with 
 all non-condensing engines. The valve-gear and condenser for 
 attaining these resnlts, may possess different degrees of mechan- 
 ical merit; but none can be considered as successful which (with. 
 an evaporation of from eight to ten pounds of water in the 
 boiler, per pound of coal burned) require more than two pounds 
 of coal per hour per horse-power. 
 
 The steam-engine is still in an exceedingly imperfect condi- 
 tion, and we do not doubt but that it would be rapidly improved 
 were it not that there is so little room for additional discovery, 
 and that so little is left to be patented. The great principles of 
 steam-engine economy are open to the free application of all, 
 and they are so simple that none should fail to recognize and 
 adopt them. 
 
 The action of steam in an engine cylinder is developed in its 
 most simple form in the non-condensing or high pressure engine, 
 in which the vacuum takes no part. 
 
 The class most in use is the non-condensing throttling engine, 
 in which the steam follows to the end, or nearly to the end, of 
 the stroke, and in all cases where the pressure is reduced be- 
 tween the boiler and the cylinder by the action of the regulating 
 valve that is, by throttling.
 
 VARIETIES OF STEAM ENGINES. 
 
 245 
 
 The diagram given by such engines (see Fig. 86) is as follows: 
 The steam-line, k g, rapidly declines, from throttling of the 
 steam; this also occurs when the steam-ports, or steam-pipe, are 
 too small. 
 
 When the pressure declines throughout the stroke of the 
 engine, as above, on account of the contraction of the steam- 
 pipe area by the governor- valve, the steam is said to be "wire- 
 drawn." The engine being non-condensing, the atmospheric 
 line is below the whole enclosed area of the diagram. See A, D. , 
 Fig. 86. 
 
 FIG, 86. 
 
 In order to save steam, or more correctly, to employ its effect 
 more economically, we must, of course, admit the steam at a 
 greater pressure than if we are using it full stroke, because we 
 must obtain the same mean pressure. Taking, for example, an 
 engine using a steam pressure of 75 pounds per square inch, and 
 following the piston full stroke, how much must that pressure 
 be increased to run the same engine with steam expanded?
 
 246 
 
 THE STEAM-ENGINE AND THE INDICATOR. 
 
 Diagram, Fig. 87, exhibits the improvement made in modern 
 engines in the valve motion. The distance between k and e 
 shows the travel of the piston during steam admission; at e the 
 lap on the valve covers the port, the steam is cut off, and the 
 distance between e and g represents the travel of piston during 
 the expansion in the cylinder. To avoid excessive back pres- 
 sure at the commencement of the return stroke as shown in 
 diagram, Fig. 87, the steam is released at /, the distance from 
 I to g being the travel of the piston after the exhaust-port is 
 opened; the space between the atmospheric line A D, and bot- 
 tom or exhaust line of diagram, represents the back pressure. 
 
 FIG. 87. 
 
 The rising curve at the lower left-hand end from h to i is the 
 cushion or compression. The mean back pressure is less than 
 five-hundredths (0.05) of the mean direct pressure. 
 
 In the above diagram, the piston has moved to about five- 
 eighths (0.63) of the stroke when the cut-off took place. The 
 cut-off is obtained with a single slide-valve and eccentric; at the 
 point /, the exhaust-port opens after the steam has expanded 
 from e to /, or about 93 per cent, of the stroke; the early release 
 at /, allows the spent steam to discharge itself so that the press- 
 sure falls to a minimum on the return stroke.
 
 VARIETIES OF STEAM ENGINES. 247 
 
 Non-condensing, automatic cut-off engines are those in which 
 the movement of the cut-off valve (which is sometimes indepen- 
 dent of the main valve) is so controlled by the governor as to 
 cut off the steam earlier or later in the stroke, as may be re- 
 quired to maintain the desired uniformity of speed under varia- 
 tions of load and steam pressure. It is so called in contradis- 
 tinction to the throttling or "wire-drawing" engine, in which 
 the governor effects the desired regulation by throttling the 
 steam more or less in its passage to its work. 
 
 Automatic Expansion Engines. 
 
 The fundamental idea upon which automatic expansion en- 
 gines are designed, is that of variable expansion. Engines 
 of this class have no regulating valve in the steam pipe, but full 
 boiler pressure is maintained in the valve chest, and is admitted 
 to the cylinder at the commencement of each stroke, and the 
 governor adjusts the force to the varying resistance by changing 
 the point of cut-off. The action of the governor-raises or lowers 
 the steam line on the diagram, while that of the variable cut-off 
 lengthens or shortens it, as the load on the engine is increased 
 or diminished. The object of using steam expansively is to 
 obtain a high mean pressure throughout the stroke with a low 
 terminal pressure, on the assumption that while the former 
 represents the work done, the latter represents the quantity of 
 steam expended in doing it. 
 
 It is readily demonstrated, and is abundantly proven in prac- 
 tice, that the greatest difference between the mean pressure in 
 the cylinder through the stroke, and that at the end of the 
 stroke, or at the point of release, is obtained by admitting the 
 highest attainable pressure at the very commencement of the 
 stroke, maintaining it up to the point of cut-off, cutting off 
 early and sharply, and permitting the confined steam to exert 
 its expansive force to the end of the stroke. 
 
 Theoretically, the earlier the cut-off and the further expan- 
 sion is carried the better, but this is greatly modified by various 
 practical considerations. 
 
 While engineers are agreed in employing some degree of 
 expansion, perhaps no two would recommend precisely the 
 same. Expansion can certainly be overdone.
 
 248 THE STEAM-ENGINE AND THE INDICATOR. 
 
 To Frederick E. Sickles, of New York, must be given the 
 credit of the liberating valve-gear. The apparatus devised by 
 him for its application to the double-beat-valves employed on 
 steamboat engines on the North River and Long Island Sound, 
 was singularly ingenious and efficient, and has for the last fifty 
 years or more been known as the Sickles cut-off. It combined 
 an opening, at first exceedingly gradual, and then accelerated 
 as the motion of the piston was increased with an almost instan- 
 taneous closing of the port. 
 
 The reasoning of the advocates of this system was short, and 
 in their own view, conclusive. It ran as follows: 
 
 "Steam to be expanded to the best advantage must be cut off 
 sharply. The sucking in of steam into the cylinder through a 
 gradually contracting passage technically termed 'wire drawing,' 
 involves a great loss, and is not to be tolerated in any degree. 
 A valve closed by a return of the opening motion cannot effect 
 a sharp cut-off, but if it could have a motion sufficiently rapid 
 for this purpose, then the opening motion would need to be 
 equally so, and this would admit the steam so suddenly and 
 violently on the centres as soon to destroy the engine. The 
 admission must be gradual, the cut-off must be sudden. The 
 liberating gear only can give to the valve a slow opening and 
 a swift closing movement. Ergo, all the world must sooner or 
 later come to use the liberating valve gear." 
 
 The theory of working by variable expansion requires the 
 following distribution of the steam: 
 
 First. The load on the valve should be constant, or the 
 same for all points of cut-off, admitting the full pressure at the 
 beginning of the stroke. 
 
 Second. The opening should be sufficient to enable this 
 pressure to be maintained in the cylinder up to the point of 
 cut-off, and the cut-off should be so rapid that the pressure shall 
 not fall during the operation of closing the port. 
 
 Third. The exhaust action should not be affected by changes 
 in the point of cut-off; should permit the confined steam to exert 
 its expansive force, as nearly as possible, to the end of the 
 stroke, and then discharge it without loss of power from back 
 pressure. 
 
 Thus every feature of the diagram is invariable, except the
 
 VARIETIES OF STEAM ENGINES. 249 
 
 point of cut-off, which is moved by the action of the governor, 
 according to the changes occuring in the load. From the 
 above it will be seen that it is not possible to effect all these 
 objects by means of a single valve. 
 
 The exhaust-valves must differ from the admission-valves 
 both in their dimensions and in their movements'. Each must 
 be adapted to the performance of its own function, and to this 
 end must be quite independent of the other. 
 
 Automatic Cut-Off Engines. 
 
 The fundamental idea upon which these engines are designed 
 is that of variable expansion. Engines of this class have no 
 regulating valve in the steam-pipe, common to all ordinary 
 throttling .slide-valve engines, but the full boiler pressure is 
 maintained in the valve-chest, and admitted to the cylinder at 
 the commencement of each stroke, and the governor adjusts 
 the force to the varying resistance by changing the point of 
 cut-off. The action of the regulating valve raises or lowers the 
 steam-line on the diagram, while that of the variable cut-off 
 lengthens or shortens it, as the load on the engine is increased 
 or diminished. The object of working steam expansively is, 
 to obtain a high mean pressure through the stroke with a low 
 terminal pressure, on the assumption that, while the former 
 represents the work done, the latter represents the quantity of 
 steam expended in doing it. It is readily demonstrated, and is 
 abundantly proven in practice, that the greatest difference be- 
 tween the mean pressure in the cylinder through the stroke and 
 that at the end of the stroke, or at the point of release, is ob- 
 tained by admitting the highest attainable pressure at the very 
 commencement of the stroke, maintaining it up to the point 
 of cut-off, cutting off early and sharply, and permitting the 
 confined steam to exert its expansive force to the end of the 
 stroke. 
 
 Theoretically, the earlier the cut-off, and the further expan- 
 sion is carried, the better; but this is greatly modified by vari- 
 ous practical considerations. 
 
 In 1849, George H. Corliss brought out the modern "cut-off 
 engine," and advocated a boiler pressure of seventy pounds per 
 square inch in combination with a piston speed of 450 feet per
 
 250 THE STEAM-ENGINE AND THE INDICATOR. 
 
 minute, by which means he reduced the coal consumption from 
 six to eight pounds of coal per horse-power per hour, in the 
 best engines, to three pounds. 
 
 When Corliss first offered to sell his engine to manufacturers, 
 they could not understand it, although he explained to them 
 that the efficiency of it was due to a higher initial steam-pres- 
 sure in the cylinder; the steam-line maintained without expan- 
 sion ; the rapid closing of the steam-valves, whereby wire- 
 drawing was prevented, and the whole expansive force of the 
 steam secured; a low terminal, and a free exhaust. Under 
 these conditions, the steam was expanded until there was no 
 more work in it. But with all the above advantages, Mr. Cor- 
 liss could not introduce his engine at the advanced price he 
 asked over that of those then in use, except by agreeing to take 
 the saving in fuel for a stated period for his pay. This state of 
 affairs only lasted a few years, when the reputation of the 
 engine became well-established, and it was copied all over the 
 world on the expiration of the patent. 
 
 The following indicator diagram (Fig. 88) from a non-con- 
 
 FIG. 88. 
 
 deusing Corliss engine, is a fair sample of the distribution of 
 steam in the cylinder. 
 
 The knowledge acquired in the time of Watt, of the essential 
 principles of steam-engine construction, has since become
 
 VARIETIES OF STEAM ENGINES. 35! 
 
 familiar to intelligent engineers. It lias led to the selection of 
 simple, strong, and durable forms of engine and boiler, to the 
 introduction of various kinds of valves and valve-gearing, 
 capable of adjustment "to any desired range of expansive work- 
 ing, and to the attachment of efficient governors to regulate the 
 speed of the engine, by determining automatically the point of 
 cut-off which will, at any instant, adjust the work exerted by 
 the expanding steam to the load. 
 
 The value of high pressure, and considerable expansion, was 
 recognized in the early part of the present century, and Watt 
 gave the steam-engine very nearly the shape it has to-day. The 
 compound engine, in principle at least, was invented by con- 
 temporaries of Watt, and the only important modifications since 
 are the introduction of the "drop cut-off," the attachment of 
 the governor to the expansion apparatus in such a manner as to 
 control the degree of expansion, the improvement in propor- 
 tions, the use of higher steam and greater expansion, and the 
 employment of double-cylinder engines, after the rise in steam 
 pressure, and the discovery of internal condensation and re- 
 evaporation in the cylinder, which were entirely unknown to 
 Watt and his contemporaries. 
 
 The Corliss engine was followed by the Greene engine, built 
 by Thurston, Greene & Co., of Providence, R. L, and at the 
 present time by the Providence Steam-Engine Co. This engine 
 was invented by Noble T. Greene, and patented in 1855. It is 
 similar to the Corliss in having four valves two steam, and two 
 exhaust so placed as to reduce clearance to a minimum, the 
 only difference being in the type of valve, Corliss using a 
 vibrating valve worked by a "wrist-plate " connected to a single 
 eccentric, and the Greene engine using a plain slide-valve for the 
 steam, and gridiron slides for the exhaust, the latter set at right 
 angles to the steam valves; each are worked by a separate 
 eccentric. Other automatic engines are the Wright, Brown, 
 Fitchburg, etc. 
 
 In the present advanced state of the arts, it looks as if the 
 "drop cut-off" will be superseded by the "positive-motion cut- 
 off," especially for direct connection, due to the high rotative 
 speed in demand by the introduction of electric lighting. In 
 this respect, it is but a repetition of the transition in hydraulics,
 
 252 THE STEAM-ENGINE AND THE INDICATOR. 
 
 which dispensed with the ponderous overshot and breastwheels, 
 and substituted in their place the fast-running and close-gov- 
 erning turbines. 
 
 One of the greatest losses of the steam-engine is the conden- 
 sation of steam and loss of heat at entrance into the cylinder, 
 by the action of the metal surfaces to which it is exposed on all 
 sides at the beginning of the stroke, and this is augmented, 
 when at work, by light loads, large cylinders, and low rotative 
 speeds; the remedy is the converse. In non-condensing engines, 
 a direct loss occurs by expansion below the atmosphere, thus 
 creating a vacuum resistance on the impelling side of the pis- 
 ton, at the expense of the fly-wheel, see diagrams, Figures 17, 
 21 and 67, which show this plainly. High-pressure steam 
 should mean dry steam, and as a consequence there will be less 
 condensation at the commencement of the stroke. High rota- 
 tive speed, also, to a greater or less extent, diminishes cylinder 
 condensation. It is evident that the longer time steam remains 
 in contact with a cooler surface, the more it will be condensed. 
 To use a little steam at a time, to use it very quickly, and to 
 keep it hot, is the fundamental principle of high rotative speeds, 
 than which there is nothing more practically important in 
 steam-engineering. With a slow motion, the cooling effect of 
 the expansion penetrates further into the metal of the cylinder, 
 requiring more steam and entailing more condensation at each 
 admission to reheat it. High rotative speed reduces the dimen- 
 sion of the engine and the sizes of pulleys, and effects an econ- 
 omy of space which is often very valuable; therefore, in the 
 best practice, engines are now run at very high velocities of pis- 
 ton, with a given maximum speed of rotation, reducing the 
 time for condensation of each charge, and the necessary change 
 of temperature preceding such condensation. The amount of 
 steam condensed is thus made a minimum in a given time, the 
 percentage of loss of the increased quantity of steam consumed 
 by the engine becomes the least possible. 
 
 Corliss, Greene, Brown, and others, all have increased the 
 rotative speed of their engines, but have not modified their 
 designs in any degree, and are, in fact, limited in speed, due to 
 their detachable cut-off arrangements.
 
 VARIETIES OF STEAM ENGINES. 
 
 253 
 
 Positive-Motion Cut-Off Engines. 
 
 The Porter Allen engine was one of the first to show the value 
 of high rotative speed, .and is distinguished by a system of 
 valves and valve movements perfectly adapted to the speed it is 
 run at. 
 
 The perfection of this engine is due to Mr. Charles T. Porter, 
 who by his courage, persistence, and skill brought the engine 
 into use it spite of every discouragement. Now it belongs to 
 the class of variable expansion engines having an invariable ex- 
 haust; the valves receive positive movements and work in 
 equilibrium. It embodies many radical improvements, and is a 
 decided advance in steam-engineering. 
 
 FIG. 89. 
 
 The above diagram, Fig. 89, is from a Porter Allen engine, 
 
 " by 30", at 230 revolutions per minute. 
 Diagram Fig. 156, is from a condensing engine of the above 
 pattern, n^j" by"i6", and 350 revolutions per minute. 
 
 The Buckeye Engine. 
 
 This engine was designed by Mr. J. W. Thompson and built 
 by the Buckeye Engine Co., at Salem, Ohio. It is fitted with 
 a positive-motion "automatic " valve-gear and a balanced valve, 
 and has a stability and an excellence of workmanship that make 
 it safe at high speeds, while the peculiarities of its construction 
 are such as give it a high place as an economical machine. It 
 is capable of meeting, in competition, the best engines of the 
 day.
 
 254 THE STEAM-ENGINE AND THE INDICATOR. 
 
 This engine has a peculiar balanced valve which can be pro- 
 portioned to take any desired portion of the steam pressure, 
 leaving, if properly adjusted, just enough on the valve to hold it 
 with certainty to its seat, and to secure proper wear and bearing 
 on the seat. This valve is arranged to take steam through it- 
 self and deliver it outside of it; has perfectly flat wearing sur- 
 faces, positive movements of invariable extent, preventing the 
 formation of shoulders on seat or valve; while the clearance is 
 so small that it is easily counteracted as regards ill effects ordi- 
 narily due to moderate compression. It has only two ports, and 
 possesses such advantages as may be claimed for that arrange- 
 
 FIG. 90. 
 
 ment. The governor is driven by a positive connection with 
 the shaft on which it is set; and as the cut-off is adjusted by the 
 motion of an eccentric, the ratio of expansion is the same at 
 both ends of the cylinder; it possesses the advantage, common 
 to all engines having a positive-motion valve-gear, of being un- 
 restricted in speed. 
 
 Indicator diagrams, Figs. 90 and 91 are from a Buckeye auto- 
 matic engine. The steam being cut off at e is released at g. 
 
 Diagram Fig. 92 shows the action of the steam in a first-class 
 automatic condensing engine. 
 
 The only difference between this engine and the former is the
 
 VARIETIES OF STEAM ENGINES. 
 
 255 
 
 addition of a condenser. Condensing engines with automatic 
 cut-off produce diagrams as shown in Figs. 89 and 92, which 
 show the highest attainment of valve adjustment and the expan- 
 sive action of the steam.. 
 
 The previous three engines described use independent valves 
 to cut off the steam. I now propose to show indicator diagrams 
 from high-speed engines in which a single valve does duty both 
 as a distributing and a cut-off valve. The first engine to which 
 I refer is "The Straight Line Engine." It is the invention of 
 John E. Sweet, of Syracuse, N. Y. The problem proposed 
 was to design an engine which, while consisting of the smallest 
 possible number of parts, should be economical in the use of 
 steam, capable of the most perfect regulation attainable with 
 any known device, strong and stiff in every part when subjected 
 
 FIG. 91. 
 
 to the working strains of high speeds, inexpensive in first cost, 
 and as durable as a simple engine can be. 
 
 The only objection to a single-valve cut-off engine is the fact 
 that the mean pressure of the steam entering the cylinder up to 
 the point of cut-off is necessarily less than with the double- 
 valve gear introduced by Corliss, Porter- Allen, and the Buckeye 
 Engine Company, which have been long standards, and which 
 are admittedly superior in this respect. 
 
 The Sweet engine is so proportioned and arranged in the dis- 
 position of its details, that with 300 revolutions and upwards 
 there is no excessive jar, serious wear, or heating of journals. 
 
 Diagrams Figs. 94 and 95 were taken from a single-valve 
 straight line engine.
 
 256 THE STEAM-ENGINE AND THE INDICATOR. 
 
 Mr. Sweet has also designed an engine which differs from the 
 engine just described. The new engine has an independent ex- 
 haust valve similar to the Corliss, Buckeye and others. The 
 
 FIG. 92. 
 
 general design remains the same, but the cylinder is square out- 
 side. The steam valve is on one side, and the exhaust valve on 
 the other. A fixed eccentric controls the exhaust valve, and 
 
 FIG. 93. 
 
 necessarily the exhaust and compression; and a shifting eccen- 
 tric operated by the governor operates the steam valve, and so 
 controls the admission and cut-off. 
 
 A new feature is introduced which makes this engine differ
 
 VARIETIES OF STEAM ENGINES. 257 
 
 from all others so far as is known to the writer, namely, while 
 the lead of engines, having one or more valves for the steam in- 
 let, and one or more for exhaust, is made as nearly constant as 
 
 FIG. 94. 
 
 possible, in this engine the lead is variable as well as the cut-off. 
 That is to say, when taking steam at three-quarter stroke, which 
 
 FIG. 95. 
 
 it does while yet under the control of the governor, there is a 
 prominent positive lead, and when cutting off short, either no 
 lead or a negative lead. The object is to vary the lead accord-
 
 258 THE STEAM-KNGINE AND THE INDICATOR. 
 
 ing to the amount of power developed, so as to bring the recip- 
 ^ rocating parts to rest without shocks. 
 
 The Westinghouse Single Valve Engine. 
 
 In respect to high speeds the Westinghouse engine marks a 
 distinct period in steam engineering. Its design has eliminated 
 every point in which speed produces an injurious effect. The 
 most serious results from high speed in the horizontal engine 
 are found in lost motion, and the consequent close adjustment; 
 in the danger from heated bearings, due to the impossibility of 
 maintaining continuous and sufficient lubrication; in the spring- 
 ing of the transmitting parts, etc. The Westinghouse engine, 
 on the contrary, is insensible to lost motion, since its strains are 
 all in one direction, and to this extent it becomes self-adjusting. 
 Lubrication is insured by all the running parts revolving in oil. 
 All strains are transmitted direct, the shape of the bed being 
 such as to insure a degree of rigidity per pound of metal not at- 
 tained in any other design. This fact is most clearly illustrated 
 by the everyday practice, in which the matter of 50 or 100 
 revolutions more or less is considered of no practical import- 
 ance. 
 
 The practical success attained by the Westinghouse standard 
 automatic engine, has put beyond question the merit of the 
 single-acting and self-lubricating principles. The development 
 of this type of engine has been of sound and persistent growth 
 through all stages of imperfections and perfections, and against 
 unmeasured prejudice and opposition, until the number of West- 
 inghouse engines shipped each month probably equals the com- 
 bined sales of all other single-valve automatic engines in the 
 market. 
 
 Within the past year the designer of the Westinghouse engine 
 has succeeded in improving it by compounding. By this im- 
 provement they are able to develop and deliver a net effective 
 horse-power to the belt upon the smallest consumption of 
 measured water (steam) yet attained. This fact is evident by 
 9*>s,- : inspection of indicator diagrams, Figs. 123 and 124, pages 288
 
 VARIETIES OF STEAM ENGINES. 
 
 259 
 
 Locomotive Engines. 
 
 In a diagram taken from a locomotive engine when running 
 slow, the periods of steam admission, from k to e expansion, 
 
 FIG. 96. 
 
 from e to f release at f, exhaust from f to h, and compression 
 from h to z', lead from i to k, are often well marked, as confirmed 
 by the reduced diagram Fig. 96, from a Baldwin four-driver 
 locomotive with 16" by 24" cylinder and 61" drivers, running 
 at the rate of ten miles an hour, hauling 1,565,583.33 pounds 
 or 782,942 tons of 2 ocx) pounds; boiler pressure 120 pounds per 
 square inch above atmosphere. The diagram exhibits successive 
 stages in the modification of the indicator-card. 
 
 The following diagrams were taken from Baldwin locomotive 
 engine, No. 81, having two pairs of driving-wheels 68 inches in 
 diameter, on the Cincinnati, New Orleans, and Texas Pacific 
 Railway. 
 
 The dimensions of this locomotive are as follows: 
 Diameter of cylinder, 18"; stroke of piston, 24"; number of 
 drivers, 4; diameter of drivers, 68"; outside lap of valve, #j"; 
 lead in full gear, &"; length of steam port, 16"; length of ex- 
 haust port, 16"; width of steam port, i#"; width of exhaust 
 port, 2^"; diameter of exhaust nozzle, 3^"; area of grate, 17 
 square feet; heating surface in flues, 1324.6 square feet; heating 
 surface in fire-box, 133.2 square feet; total heating surface, 
 1457.8 square feet; weight in working order, 90,000 pounds; 
 weight on drivers, 60,000 pounds. Type of valve u Allen 
 Richardson. ' '
 
 260 
 
 THE STEAM-ENGINE AND THE INDICATOR. 
 
 The tractive power exerted is as follows: 
 
 i8 2 x 24 324 x 24 
 
 60 ~ fio =114.35 pounds 
 
 for each pound of effective pressure per square inch exerted on 
 the pistons. 
 
 The data furnished by the following indicator diagrams will 
 show the tractive power exerted under different rates of speed in 
 practice, the load being very nearly constant when the cards 
 were taken. 
 
 Load. 
 
 The train was composed of one hotel car, one parlor car, two 
 ordinary coaches, one mail and one baggage car; total, six 
 coaches well loaded. Approximate weight, 340,000 pounds. 
 The diagrams were taken when on regular passenger run and 
 under ordinary conditions, throttle opening, light; maximum 
 grade, sixty feet per mile; average grade, forty feet per mile. 
 
 These diagrams are a fair average of the performance of 
 American locomotives. 
 
 FIG. 97. 
 
 Boiler pressure, 140 pounds per square iuch. Cut off at ten 
 inches. Revolutions, 126 per minute. Throttle open one-half. 
 Miles per hour, 25.4. Horse-power, 624. 
 
 At this speed the steam line is maintained during the admis- 
 sion for ten inches up to the point of cut-off ^, then comes 
 expansion from e to f; at the latter point we have release, or 
 commencement of exhaust, which continues up to h, when com- 
 pression begins and extends to 2, where lead commences; see 
 diagram Fig. 96. 
 
 Diagram Fig. 97 was taken when starting with a boiler pres- 
 sure of 140 pounds per square inch, and making 126 revolutions
 
 VARIETIES OF STEAM ENGINES. 26 1 
 
 per minute. The scale of indicator was 60 pounds per inch; 
 the average mean pressure at this speed being 80.4 pounds per 
 square inch; the tractive power exerted was as follows: 
 
 i8 2 x 24 x 80.4 
 
 68 - 9I93- 74 pounds. 
 
 In diagram Fig. 98 the points shown in diagram Fig. 97 are 
 still denned, but the greater speed of the locomotive causes them 
 to lose much of their distinctive character. The boiler pressure 
 is 145 pounds, but the speed is forty-five miles per hour, or 222 
 revolutions per minute, and the piston speed 888 feet per minute 
 
 FIG. 98. 
 
 on an up grade. The mean effective pressure on piston being 
 47.8 pounds, the tractive force is as follows: 
 
 Boiler pressure per square inch, 145 pounds. Cut-off at eight 
 inches. Revolutions per minute, 222. Throttle open one- 
 third. Miles per hour, 45. Horse-power, 650. 
 
 jS 2 x 24 x 47.8 
 
 |g =5466 pounds. 
 
 and the horse-power was: 
 
 252.5 X 888 x 47-8 x 2 = 6 hors e- p ower. 
 33,000 
 
 Diagram Fig. 99 the revolutions being 276 per minute, the 
 speed of the piston being 1104 feet per minute, quite altered the 
 characteristics of the steam line. The train was running on a 
 slight descending grade at 56 miles per hour, and it is apparent 
 that steam line, cut-off, expansion, and release are hopelessly 
 blended together.
 
 262 THE STEAM-ENGINE AND THE INDICATOR. 
 
 The mean effective pressure was 29.2 pounds, which corre- 
 sponds to a tractive force of 
 
 1 8" x 24 x 29.2 
 
 68 -=4339 pounds, 
 
 and a development of 
 
 252.5 X 1104 X 29.2 x 2 horse-power. 
 
 33,000 
 
 Boiler pressure, '135 pounds per square inch. Cut-off at four 
 inches. Revolutions, 276 per minute. Throttle open one-quar- 
 ter. Miles per hour, 55.8. Horse-power, 593. 
 
 (The diagrams have been reduced in size from the originals, 
 and therefore may not be exact facsimiles.) 
 
 The diagrams, Figs. 101 to 105, are from one of the best build 
 of English locomotives performing the same service as the Bald- 
 win locomotive; therefore they will afford a favorable comparison. 
 
 FIG. 99. 
 
 The engines of the London and North-Western Railway for 
 running the Scotch express have two pair of driving-wheels, 5^ 
 feet in diameter. The cylinders are 17 inches in diameter with 
 24 inches stroke, and the tractive power exerted is, therefore: 
 
 \f x 24 289 x 24 
 
 55 55 = 105.09 pounds 
 
 for each pound of effective pressure per square inch exerted on 
 the pistons. 
 
 The data afforded by the diagrams, Figs. 101 to 105, taken 
 from the "Precursor," the first engine built of the above type, 
 will show the tractive power exerted by this locomotive under 
 different conditions in practice.
 
 VARIETIES OF STEAM ENGINES. 
 
 263 
 
 Diagram Fig. 101 was taken when starting out of Carlisle with 
 a train of fifteen carriages, and a boiler pressure of 128 pounds 
 per square inch. It shows a mean effective pressure on the 
 pistons of 97.6 pounds per square inch, and the tractive power 
 exerted was 
 
 * ==IO)257 pounds _ 
 
 66 
 
 FIG. 100. 
 
 The above calculation is based on the supposition that the 
 diagram fairly represents those which would have been obtained 
 from both ends of both cylinders. 
 
 FIG. 101. 
 
 120 
 
 100 
 
 50- 
 
 20 
 
 . v 
 
 Diagram Fig. 102 was taken while ascending a grade of I 
 in 75, with a train of n coaches, at a speed of 28 miles per 
 hour, corresponding to 142.6 revolutions per minute, and a 
 piston speed of 570.4 feet per minute. In this case the boiler 
 pressure was also 128 pounds; the mean effective pressure on 
 piston 61.7 pounds; the tractive force 
 
 if x 24 x 6i.7_ 
 66 
 
 6484 pounds ;
 
 264 THE STEAM-ENGINE AND THE INDICATOR. 
 
 and the power was 
 
 226.98x570-4x61.7 2 = 8 hors e-po w er. 
 33,000 
 
 FIG. 102. 
 
 Diagram Fig. 103 was taken ascending a grade of i in 
 125, with a train of 15 carriages, at a speed of 33 miles an 
 hour, or 168 revolutions per minute, giving a piston-speed of 
 640 feet per minute, with a boiler pressure of 128 pounds, and 
 
 FIG. 103. 
 
 a mean effective pressure of 64 pounds, corresponding to a 
 tractive force of 
 
 17* x 24 x 64 _ 
 
 66 
 
 6726 pounds, 
 
 and the development of 
 
 226.98 x 640 x 64 , 
 
 v ^ ** ^ t x 2 = 592 horse-power. 
 
 33,000
 
 VARIETIES OF STEAM ENGINES. 265 
 
 Diagram Fig. 104 was taken while descending a grade of 
 i in 106, the train consisting of 14 vehicles, with a heavy rain 
 and a side wind blowing, amounting to a gale. In this case 
 the boiler pressure was 126 pounds, the speed 49 miles per 
 hour, or 249.6 revolutions per minute, and the mean effective 
 pressure 38.6 pounds; this corresponds to a tractive force of 
 
 66 
 
 and the development of 
 
 226.98 x 249.6 x 38.6 2 horse-power. 
 
 33,ooo 
 
 The last diagram, Fig. 105, of the series, was taken with a 
 train of n carriages running on a level at a speed of 58 miles 
 
 FIG. 104. 
 
 per hour, corresponding to 295.4 revolutions, or a piston speed 
 of 1181.6 feet per minute, and a boiler pressure of 123 pounds 
 per square inch. In this case the mean effective pressure is 
 32.7 pounds, corresponding to a tractive force of 
 
 !7* x 24 x 32.7 
 
 55 : =343 6 pounds, 
 
 and the development of 
 
 226.98 xii8i.6x 32.7 X2 = 531 . 5 horse-power. 
 33,000 
 
 The " Precursor," the locomotive from which the diagrams 
 above referred to were taken, had been running about n
 
 266 THE STEAM-ENGINE AND THE INDICATOR. 
 
 months, pulling the Scotch express train between Crewe and 
 Carlisle, a distance of about 125 miles. The average weight of 
 the trains hauled was about 140 tons, exclusive of the engine 
 itself (the average gross weight of the train being about 187 tons) 
 and the consumption of fuel but 33.2 pounds per mile. On ex- 
 amination at this time, it was found that the machinery showed 
 no appreciable wear, while the tool-marks were not worn out of 
 the horn-blocks and axle-boxes, and the coupled wheels were 
 found to have worn quite equally, thus showing that a small 
 wheel locomotive can be made, which can be used for running 
 fast trains without incurring excessive wear and tear. 
 
 FIG. 105. 
 
 This boiler has 198 steel tubes i#j inches diameter, 10 feet i 
 inch long; heating surface of tubes, 980 square feet, and 94 feet 
 6 inches in fire box, being a total of 1074 square feet, and 17.14 
 square feet of grate. Three English coaches equal one Ameri- 
 can car. 
 
 Compound Steam Engines. 
 
 Compounding is a method of prolonging the expansion. 
 
 Compound engines are those which have two or more cylin- 
 ders (connected to one shaft) within which the steam acts con- 
 secutively, from one cylinder to another. Steam is admitted 
 to the first cylinder, where it may be partially expanded; and 
 when the first piston arrives at or near to the end of the stroke, 
 the steam is exhausted from the first into the second cylinder, 
 within which it expands again behind the second piston during 
 its next stroke. The steam from the second cylinder may be 
 further expanded in a third cylinder, but it is most commonly 
 exhausted from the second cylinder into the condenser.
 
 VARIETIES OF STEAM ENGINES. 267 
 
 The steam which is exhausted into the second cylinder reacts 
 upon the first piston, while the exhaust-valve is open, by back 
 pressure during its return stroke. It follows that if the second 
 cylinder had the same diameter and stroke as the first cylinder 
 the same capacity there would not be any expansive action 
 of the steam so exhausted, as it would simply pass from one 
 cylinder into the other, and there would be no useful- work 
 done; the work done by positive pressure on the second cylin- 
 der being equal to the opposing work done on the first piston 
 by back pressure. To effect useful work, therefore, in ex- 
 hausting steam from the first into the second cylinder, the 
 second cylinder must be of greater capacity than the first, 
 either by having a greater diameter or a longer stroke, or both 
 together, in order that the steam from the first cylinder may 
 expand in the second, by virtue of the enlargement of volume 
 and reduction of pressure which follows the transference. Still, 
 there is resistance (by back pressure) on the first piston in the 
 process of expansion; and as this is the same, or nearly the 
 same, pressure per square inch both ways on the second piston 
 and on the first piston it follows that the useful work done by 
 expansion from the first into the second cylinder (supposing the 
 strokes to be equal) is that due to the difference in the areas of 
 the pistons. 
 
 Generally, looking to the increase of volume by expansion 
 between the first and second cylinders, the work of the steam in 
 this (the second stage of its operation) is simply that due to the 
 number of times the final volume in the first cylinder is con- 
 tained in the final volume of the second cylinder; in other 
 words, to the ratio of expansion in the second cylinder. If there 
 is no expansive using of steam in the first cylinder, so that the 
 whole of the expansion is done in the second cylinder, then the 
 proportional work or efficiency of the steam is to be calculated 
 on the ratio of the volume of the second to that of the first 
 cylinder. But if the steam is cut off in the first cylinder before 
 the end of the stroke, then the total ratio of expansion will be 
 that of the partial expansion in the first cylinder multiplied by 
 the ratio of the volume of the second to that of the first cylinder. 
 For example: let the areas of the first and second cylinders be in 
 the proportion of i to 4, the strokes being equal. Then the
 
 268 THE STEAM-ENGINE AND THE INDICATOR. 
 
 ratio of expansion from the first into the second cylinder is 4. 
 Let the steam be cut off in the first cylinder at half-stroke, or 
 so as to expand it to twice its initial volume when the stroke is 
 completed, then the ratio of expansion in the first cylinder is 2. 
 Thus the total combined expansion of the steam in the two 
 cylinders is 4 x 2 = 8 times the initial volume, and the ratio 
 may be succinctly stated thus: 
 
 Expansion in first cylinder i to 2 
 
 Expansion in second cylinder i to 4 
 
 Total combined expansion i to 8 
 
 Now, in this instance, by means of two cylinders combined, 
 it appears that a total expansion of eight times is effected, 
 although the greatest in either cylinder individually is only an 
 expansion of four times. In this reduction of the extreme of 
 expansive working in any individual cylinder is to be found the 
 source of the advantages of using steam by compound engines. 
 
 In the year 1781, Jonathan Hornblower, who built the New- 
 comen engines, obtained a patent for using two cylinders, one 
 larger than the other, to get the benefit of the expansion, in which 
 the steam at boiler pressure, after impelling a small piston, was 
 to pass into the large cylinder and act upon the greater number 
 of square inches with a less pressure per square inch, thus 
 rendering the two cylinders approximately equal in power. 
 After getting his patent, however, he could make no use of it, 
 as Watt's claims covered every variety of engine to which such 
 a principle could be applied. 
 
 At this time, also, there were probably no engines in use sup- 
 plied with steam at a much higher pressure than 2 or 3 pounds 
 per square inch above the atmosphere. Viewed by the light 
 of our present knowledge, the employment of the double-cylin- 
 der system under such circumstances appears little better than 
 an absurdity, and it is not to be wondered that, after some years 
 of trial, it was found that Hornblower's engines could not com- 
 pete successfully with the single-cylinder engines of Watt. To 
 this result the fact that the independent condenser invented by 
 Watt in 1769 was found to be a necessary adjunct to Horn- 
 blower's engine, no doubt, in some measure contributed. 
 
 It is noteworthy that this patent of Hornblower's was the
 
 VARIETIES OF STEAM ENGINES. 269 
 
 first public announcement that there was any benefit to be 
 derived from the expansion of the steam, when not flowing 
 freely from the boiler; although Watt had made a practical 
 application of the principle in an engine erected at Soho, near 
 Birmingham, in 1776, five years before, by closing his induc- 
 tion valves before the piston had arrived at the end of the 
 stroke in an ordinary single-cylinder engine. Hornblower's 
 engine met with small success. As it used steam at low pres- 
 sure, it had but limited expansive power, and the advantages 
 were of no account; rather, they became negative on account 
 of the resistances due to the use of two pistons. At this time 
 the use of two cylinders proved unsuccessful. 
 
 But when higher pressure was employed, Arthur Woolf did 
 for the engines of Evans, Trevithick, and others, what Horn- 
 blower had done for those of Watt; he applied to them the 
 principle of the double cylinder. As he could use high-pres- 
 sure steam, there was promise of success for the invention, and 
 it did succeed, and he has given his name to engines having 
 two cylinders. 
 
 In 1804, Woolf took out a patent (No. 2772) for "certain 
 improvements on the construction of steam-engines," in which 
 he applied the same principle to high-pressure engines. Woolf 
 employed two steam cylinders of different dimensions, each 
 furnished with a piston, the smaller cylinder having a com- 
 munication at the top and bottom with the boiler, but com- 
 municating also with the two ends of the larger cylinder in 
 such a manner that the steam would cause both pistons to 
 move in the same direction. 
 
 That which contributed to the success of Woolf engines 
 was that, although the expansion was not sufficient to yield 
 much advantage over ordinary engines, the division of the 
 work of the steam between the two pistons diminished the 
 differences in pressure and the loss of steam. This was an 
 important matter in the early construction of steam-engines. 
 
 Of late years notwithstanding, on the one hand, the un- 
 reasoning advocacy of many practical men, who have claimed 
 for the system unaccountable advantages and impossible sav- 
 ings, and, on the other hand, the adverse opinions of some 
 theoretical writers, who have held it to be useless complication,
 
 270 THE STEAM-ENGINE AND THE INDICATOR. 
 
 possessing no advantage whatever the compound engine has 
 grown into considerable favor. For marine purposes, indeed, 
 it has almost displaced the simple engine. 
 
 It is well known that a given initial pressure, in expanding 
 down to a given final pressure, is capable of exerting a definite 
 quantity of motive-power, and it is certain that whether the 
 steam is expanded in one, two, or ten cylinders, this limit of 
 power cannot be exceeded. In practice, the theoretical limit 
 of power is never attained, either with simple or compound 
 engines, there being apparently sources of loss peculiar to, and 
 not easily separable from, each system. 
 
 The main difference between the simple and compound sys- 
 tems arises from the circumstance that, with the former, the 
 entire variation in temperature and pressure of steam due to a 
 high rate of expansion occurs in one cylinder, for the tempera- 
 ture of the steam falls with the pressure, and the cylinder is 
 cooled to a certain extent by the end of the stroke. When the 
 next charge of steam of higher pressure is introduced for the 
 next stroke, a part of it is condensed upon the cooler walls of 
 the cylinder, which are thus heated to nearly the temperature of 
 the entering steam. This is a direct loss, for although the steam 
 so condensed is partially re-evaporated towards the end of the 
 stroke by the heat partially returned from the cylinder to the 
 expanded steam, nevertheless, the absolute loss is so serious as 
 to nullify attempts at usefully expanding steam beyond limits 
 of about four times in one cylinder. Hence the advantage of 
 dividing the expansion of steam between two cylinders (thereby 
 reducing the range of injurious variations of temperature) more 
 or less evenly between two or more cylinders. Wide variation 
 of pressure in a single cylinder leads to objectionable irregu- 
 larity of rotative effort on the crania-pin. It may also cause 
 strains upon the mechanism somewhat in the nature of blows, 
 and in any case it imposes strains much in excess of the mean 
 strain. But variation of pressure does not affect the indicated 
 power developed. In so far, however, as the compound engine 
 equalizes the strains upon the mechanism, its action is un- 
 doubtedly advantageous. 
 
 Extreme variation of temperature in an unjacketed, or par- 
 tially jacketed cylinder, leads to initial condensation, and final
 
 VARIETIES OF STEAM ENGINES. 27! 
 
 re-evaporation in the cylinder, the effects of which are to very 
 much reduce the economy of the engine... When, therefore, (as 
 is almost invariably, but not necessarily, the case in practice) 
 the steam is expanded under conditions which allow of lique- 
 faction, any arrangement reducing the variation of temperature 
 tends to reduce the amount of alternate condensation and evap- 
 oration, and consequently, also, to reduce the loss arising from 
 such action. But if the simple cylinder be wholly jacketed, or 
 nearly jacketed, provided the steam is brought into it suffi- 
 ciently superheated to raise the temperature of its unjacketed 
 portions up to that of steam of the initial pressure, by parting 
 with its superheat, variations of temperature are productive of 
 no appreciable loss. Further, it is probable that were steam 
 used in a simple engine absolutely without liquefaction, the in- 
 dicated work developed would be quite as great as, if not 
 greater, than that obtained with any kind of compound engine. 
 
 There is, with the compound engine, an unavoidable loss of 
 pressure between the two cylinders, arising from the resistance 
 of the passages. This loss need not exceed one pound per 
 square inch of pressure, provided the steam is dry, and the pas- 
 sages properly arranged. A serious fall of pressure frequently 
 arises from the unresisted expansion of the steam into the clear- 
 ance space between the two cylinders. This loss may be, to a 
 large extent, avoided by low pressure cylinder compression.- and 
 by having an expansion valve on the low pressure cylinder. In 
 most cases, the actual fall of pressure from these two causes is 
 very appreciable, and the mean pressure obtained with a given 
 ratio of expansion falls short of that of steam expanded to the 
 same extent in a single cylinder, the work developed by a pound 
 of steam being consequently reduced. 
 
 The steam when expanded down to its final pressure, occupy- 
 ing the low pressure cylinder only, the size of this cylinder for 
 a given power would if there were no loss by useless expan- 
 sion be the same as that of a simple engine of the same power, 
 working with the same pressure and ratio of expansion. Owing 
 to the loss of pressure arising with the compound engine, the 
 low pressure cylinder has to be made somewhat larger than 
 would suffice for the simple engine. The high pressure cylin- 
 der, therefore, adds nothing to the power of the arrangement;
 
 272 
 
 THE STEAM-ENGINE AND THE INDICATOR. 
 
 but, on the contrary, if the low pressure cylinder were used 
 alone, as a simple engine, it would, with the same steam pres- 
 sure and expansion, develop a greater power than the two 
 together working on the compound system. 
 
 The following figures, 106, 108 and 109 illustrate, in outline, 
 the action and arrangement of the principal varieties of com- 
 pound engines; the shaded portion represents steam. 
 
 In Fig. 106, the two pistons travel together in the same direc- 
 tion, and work on the same connecting-rod and crank-pin, and 
 it is known in the trade as a "Tandem" engine. 
 
 The steam from the boiler enters the high pressure cylinder, 
 and after being partially expanded in that cylinder, it is 
 exhausted directly into the opposite side of the low pressure 
 cylinder, where the expansion is completed. The course taken 
 by the steam is indicated by arrows. 
 
 FIG. 106. 
 
 Indicator diagram, Fig. 107, is from a "Tandem" engine; 
 the upper diagram, //, is from the high pressure cylinder, and 
 the lower diagram, Z, from the low pressure cylinder. 
 
 It will be seen, from an inspection of Figs. 106 and 108, that 
 First: the maximum steam pressure from the boiler comes upon 
 the high pressure piston at the same time that the maximum 
 exhaust pressure from the high pressure cylinder comes upon 
 the low pressure pistons, the periods of maximum and mini- 
 mum pressure being coincident. 
 
 Second. The pressure on the connecting-rod at any point of 
 the stroke is equal to the combined load upon the two pistons 
 at that point, and the single connecting-rod upon the crank-pin 
 precisely as in the simple engine. 
 
 Third. The back pressure against the high pressure piston 
 is disregarding the friction of the steam passages always the 
 same as the forward pressure upon the low pressure piston. 
 
 Fourth. The temperature in the high pressure cylinder
 
 VARIETIES OF STEAM ENGINES. 
 
 273 
 
 varies between much the same limits as in the case of the 
 simple engine; but the variation is spread over both strokes, 
 and the high pressure cylinder is at no time in communication 
 with the condenser. 
 
 The cylinders in Fig. 108 are placed side by side; the pistons 
 travel in opposite directions, being coupled to two crank-pins 
 placed at opposite centers, or nearly so. An expansion-valve is 
 necessary for the high pressure cylinder only. Instead of locat- 
 ing the crank-pins exactly at opposite centers, it is advisable to 
 place one slightly in advance of the center, as the engine may 
 then be started from any position, and this without any sacrifice 
 of steam efficiency. 
 
 FIG. 107. 
 
 The action of steam in this engine, and consequently its in- 
 dicator diagram, is precisely the same as in the last. Although 
 the pistons are traveling in contrary directions, the points of 
 maximum and minimum pressure upon the two pistons are 
 coincident, and the rotational effort upon the crank is much 
 the same as in the last arrangement. 
 
 One curious form of continuous-expansion compound engine 
 is constructed somewhat on the principle of the bucket and 
 plunger pump (see Fig. 109). 
 
 One cylinder only is used, and the efficient area of the piston 
 is reduced on one end to, say, one-half or one-third of its total 
 area by means of a trunk piston-rod, the other side of the pis- 
 ton having its whole surface exposed to pressure. The steam 
 from the boiler is admitted on the reduced or annular side of 
 18
 
 274 
 
 THE STEAM-ENGINE AND THE INDICATOR. 
 
 the piston, or trunk side, #, and it expands here, as in an ordi- 
 nary high pressure cylinder, to the end of the stroke. It 
 exhausts, however, by an appropriate valve, to the other side, 
 A y of the piston, where it acts on a greater area, and produces 
 the return stroke, expanding ultimately to the whole capacity 
 of the cylinder, and then exhausting into the condenser. The 
 same cylinder is thus exposed to the highest and lowest pres- 
 sure, viz., that of the entering steam and that of the condenser; 
 so that one of the alleged advantages of compound engines is 
 here sacrificed. It is noticeable, too, that the high pressure 
 steam is opposed only by the back pressure in the condenser, 
 while the low pressure steam during the return stroke is 
 opposed by steam of the same pressure, the same steam, in 
 fact, acting, however, on a smaller area. In each case the 
 atmospheric pressure on the trunk is in the same direction, 
 assisting the high pressure steam and opposing the low pressure 
 
 FIG. 108. 
 
 to an exactly equal extent. It follows, therefore, that the pres- 
 sure during the return stroke must be more than that of the 
 atmosphere, unless the latter is counterbalanced by a weight, or 
 removed by the substitution of the condenser pressure. It is 
 not easy to resort to this last expedient in the engines just de- 
 scribed, except in a partial manner, by using the outer end of 
 the trunk as the ram of the air-pump. It is, however, resorted 
 to in some engines identical in principle with these, though 
 differing a little in form, the arrangement being something of 
 this kind; a high and a low pressure cylinder are placed in one 
 line, say for instance, in a vertical engine, the high above the 
 low, and the pistons secured to a single piston-rod. The ends 
 of the two cylinders which are next to each other that is, the 
 bottom of the high and the top of the low are always in free 
 communication with each other, and it is from this space that 
 the atmospheric pressure is removed by connection with the
 
 VARIETIES OF STEAM ENGINES. 
 
 275 
 
 condenser. Steam from the boiler is admitted above the small 
 piston, and completes a stroke, as before, in the high pressure 
 cylinder. On exhausting, it passes to the under side of the 
 large piston, and produces the up-stroke by pressure on the 
 increased area of the low pressure piston. Here the high pres- 
 sure steam is opposed by the pressure in the condenser, and the 
 low pressure by steam of equal pressure, as in the case of the 
 trunk compound engine. 
 
 In the above engines as the exhaust-port of the high pressure 
 cylinder opens, the low pressure piston is at the end of its 
 stroke, so that no expansion of the exhaust steam from the 
 high pressure cylinder can take place (as in the case of com- 
 pound engines with a receiver, as will be shown hereafter) 
 
 FIG. 109. 
 
 except into the clearance of the low pressure cylinder and the 
 intermediate passages. As the two pistons advance, which they 
 do simultaneously, the steam flows from the smaller to the 
 larger cylinder, expanding meanwhile. The communication 
 between the cylinders is not closed until the end of the stroke, 
 or nearly so, and consequently the lowest pressure of the ex- 
 haust in the high pressure cylinder is the same as the terminal 
 pressure in the condensing cylinder. Diagram, Fig. 107, taken 
 from an engine of this class, and the coincidence of the exhaust- 
 line of the high pressure diagram with the steam-line of the 
 low pressure, shows the reduction of pressure of the high pres- 
 sure exhaust referred to. The consequence of this reduction 
 is, that the high pressure cylinder is subjected to the cooling 
 influence of a pressure very little above that in the condenser; 
 but the loss on this account is very slight indeed, if there is 
 any, because it occurs only at the end of the exhaust stroke,
 
 27 6 
 
 THE STEAM-ENGINE AND THE INDICATOR. 
 
 and also because the second cylinder acts as a trap for any heat 
 which would otherwise escape by this means to the condenser. 
 The real practical objection to this description of engine is one 
 which applies more to marine than to stationary engines; it is 
 that the pistons must begin and end the stroke together, moving 
 therefore always in the same, or always in opposite directions, 
 so that where the cylinders are parallel, and only two are used, 
 the dead points coincide. 
 
 To get over this difficulty some engineers have made a com- 
 promise, keeping the cylinders parallel, but the cranks some 
 twenty degrees or so out of the straight line that is to say, at 
 an angle of about one hundred and sixty degrees with each 
 
 FIG. no. 
 
 Vr 
 
 ( A <-4 INTERMEDIATE RECEIVER 
 /^\ 
 
 other. By this means the engines go over the dead points with- 
 out difficulty, and the pistons move very nearly together. The 
 high pressure piston ought to commence its stroke just before 
 the other (and therefore the low pressure crank should lead); 
 then the only effect of the alteration is to give a higher back 
 pressure against the small piston at the beginning of each 
 stroke (see diagram, Figs, in and 118), by compression of the 
 exhaust steam until the low pressure steam-valve opens. This 
 valve must be arranged to close again by the time that the high 
 pressure piston reaches the end of its stroke cutting off, that 
 is to say, at about three-quarters of the stroke of its own 
 cylinder.
 
 VARIETIES OF STEAM ENGINES. 
 
 277 
 
 Compound Engines with Intermediate Reservoir, or 
 Receiver. 
 
 In Figure no the two cylinders placed side by side work 
 upon two crank-pins located at right angles to each other. 
 When one piston is at the end of its stroke, the other is in its 
 mid-position. Under this arrangement it is necessary that the 
 steam from the high pressure cylinder, instead of exhausting 
 direct into the low pressure cylinder, shall exhaust into an in- 
 termediate vessel, from which the low pressure cylinder in turn 
 draws its steam. If both cylinders have expansion-valves, and 
 the intermediate reservoir is of good capacity, the reservoir 
 
 FIG. in. 
 
 pressure may be kept very nearly constant. The action of the 
 arrangement then becomes almost identical with that of two 
 simple engines one high pressure non-condensing, the other 
 low pressure condensing each working with a moderate range 
 of expansion. 
 
 Fig. in was taken from a compound vertical engine with 
 intermediate receiver, attached to cranks at right angles. The 
 cylinders were steam-jacketed, each 24 and 38 inches diameter 
 and 27 inches stroke, having a surface condenser. One effect 
 of the intermediate receiver arrangement is to maintain a more 
 constant back pressure against the high pressure piston, and to
 
 278 THE STEAM-ENGINE AND THE INDICATOR. 
 
 reduce the variation of temperature in that cylinder. Generally, 
 in practice, the high pressure cylinder only is furnished with an 
 expansion valve, and the intermediate pressure cannot then be 
 so steadily maintained. What the engine gains in simplicity 
 by this, it loses in efficiency. The intermediate receiver com- 
 pound engine is probably the most efficient yet devised. It is 
 the form most usually adopted for marine purposes, and very 
 good results have been obtained from it, both for economy of 
 steam and regularity of motion. 
 
 It has been stated that, in compound engines provided with a 
 receiver, the work of admission to the large cylinder is some- 
 times due partly to intermediate expansion, but always partly, 
 
 FIG. 112. 
 
 and sometimes entirely, to direct transfer of work from the 
 small piston. In the continuous-expansion compounds without 
 a receiver this work of admission, transferred directly from one 
 piston to the other, occurs throughout the low pressure stroke, 
 simultaneously with the work due to expansion, and conse- 
 quently it is not distinguishable from the latter in the diagram. 
 There is another form of compound engine, if such it may be 
 called, to which the term "continuous-expansion engine" has 
 been especially applied. It has two cylinders placed side by 
 side (Fig. 112), and the cranks are at right angles with each 
 other. Steam is admitted to the high pressure cylinder .//dur- 
 ing something less than the half-stroke. At this point, or just
 
 VARIETIES OF STEAM ENGINES. 
 
 279 
 
 before it, the low pressure piston being then at the beginning of 
 its stroke, a communication is- opened between the two cylin- 
 ders through the back of the low pressure cylinder valve, and 
 through ports formed in the side of the small cylinder at about 
 half-stroke. The steam is now free to expand in both cylinders 
 during the remainder of the high pressure stroke; at the end of 
 which time the low pressure piston will have reached its. half- 
 stroke. Instead, however, of the high pressure cylinder then 
 opening at once to exhaust, the steam is retained in it for a 
 short time, during which expansion of the steam in both cylin- 
 ders continues in consequence of the advance of the large piston, 
 which is traveling at this time at its maximum velocity; the 
 small one, on the other hand, being nearly stationary. When, 
 however, the low pressure piston reaches its three-quarter stroke, 
 or thereabouts, the communication between the cylinder is 
 
 FIG. 113. 
 
 closed by the low pressure valve, and immediately afterwards 
 the high pressure cylinder exhausts into the condenser. Ex- 
 pansion is still continued in the low pressure cylinder until the 
 end of its stroke, at g, when it, too, exhausts into the condenser. 
 See diagram Fig. 114. 
 
 The advantage claimed for engines built upon this system 
 over non-compounds is that any required rate of expansion may 
 be obtained without the waste of steam which takes place in the 
 passages and clearance of the single cylinder with an early cut- 
 off. Again, the advantage over compounds lies in obtaining 
 continuous expansion to any desired extent with cranks at right 
 angles and without the use of extra valves and eccentrics.
 
 280 
 
 THE STEAM-ENGINE AND THE INDICATOR. 
 
 Three valves only are required, namely, a main valve for each 
 cylinder, and a small valve for retarding the high pressure ex- 
 haust. An expansion-valve may, however, be beneficial on the 
 small cylinder. Provision is made in these engines for render- 
 ing the cylinders independent at a moment's notice, both cylin- 
 
 FIG. 114. 
 
 ders then taking steam direct from the boiler. This is a great 
 convenience in the case, for instance, of a steam-vessel coming 
 into port, giving facility in reversing or changing the direction 
 or motion of the vessel. 
 
 The disadvantages of the system appear to be that both cyl- 
 inders are subjected to considerable variations of temperature 
 
 Fie. 115. 
 
 and pressure. Both receive steam of pressure nearly equal to 
 that in the boiler, and both ultimately communicate with the 
 condenser, so that the loss of heat by radiation, etc. , during the 
 exhaust, must be appreciable. The strain also at the time of 
 .the opening of communication between the cylinders must be 
 very great, as both pistons are under the pressure of unex-
 
 VARIETIES OF STEAM ENGINES. 28 1 
 
 panded steam. It has been found in practice that the horse- 
 power developed from the high pressure cylinder is sometimes 
 decidedly in excess of that from the low pressure, but this 
 would not be a very serious drawback in most cases. 
 
 The diagrams taken from the continuous-expansion engines, 
 of which Figs. 115 and 116 area facsimile, present no peculiar- 
 ities except the very rapid fall of pressure after the half-stroke 
 
 FIG. 116. 
 
 in the high pressure cylinder, and from the beginning of the 
 stroke in the low pressure cylinder. The repression of the ex- 
 haust from the high pressure cylinder is also very clearly shown. 
 
 Compound versus Simple Engines. 
 
 In most compound engines, the theoretical action of the steam 
 is not so perfect as in simple engines. This is owing to the re- 
 sistance of the ports and connections between the cylinders, 
 and, in many cases, to the loss by sudden expansion of the 
 steam on its admission to the receiver. Notwithstanding this, 
 the testimony of steam users who are best qualified to judge 
 is in favor of compound engines. 
 
 We may now consider other points of superiority in the com- 
 pound engine. When steam does work by expansion, the 
 quantity of heat derived from it is sufficient, not only to lower 
 the temperature of the steam to that corresponding to its de- 
 creased pressure, but also to cause a portion of it to liquefy. 
 When the communication to the condenser is opened and the 
 pressure falls to the condenser pressure, the interior surfaces of 
 the cylinder, cylinder-heads, and piston, which may be sup- 
 posed to have an intermediate temperature to that of the 
 steam and of the condenser, give out heat to the water con- 
 densed on them. This causes the water to re-evaporate, in- 
 creasing the back pressure and sending a quantity of heat direct 
 to the condenser, without having performed any useful work.
 
 282 
 
 THE STEAM-ENGINE AND THE INDICATOR. 
 
 In the same way the action of these surfaces on the entering 
 steam deprives it of some of its heat, and, consequently, lowers 
 its pressure. The great loss from liquefaction is, therefore, due 
 to the fact that it acts as an equalizer of temperature, lowering 
 the initial, and increasing the final temperatures and pressures, 
 and thus decreasing the efficiency of the steam. 
 
 There can be little doubt that liquefaction, which is one of 
 the principal causes that make the actual indicated work of 
 steam fall short of its theoretical amount, is much more injuri- 
 ous in simple engines, with higher rates of expansion, than it is 
 in compound engines. The liquefaction due to work done 
 would, of course, be the same in both cases ; but the difference 
 
 FIG. 117. 
 
 of temperature between the entering steam and the sides of the 
 cylinder (in the case of the simple expansive engine) is much 
 greater than in the compound engine, and consequently, we 
 may infer, from the laws of radiation and conduction, that the 
 reduction of the initial pressure and the increase of the back 
 pressure, in the case of the simple engine, would be greater 
 than in the compound engine. 
 
 The above diagram, Fig. 117, is what might be expected 
 from a compound engine; the lengths of the diagram being 
 made proportional to the volume of the cylinders so as to show 
 the efficiency of the expansion. The outline of the combined 
 diagrams may be taken to represent the theoretical diagram 
 from a simple engine, no allowance being made for the lower- 
 ing of the initial or the increase of the back pressure due to the 
 liquefaction.
 
 VARIETIES OF STEAM ENGINES. 
 
 283 
 
 Some objection has been urged against compound engines, 
 due to the loss by intermediate expansion. 
 
 Diagram, Fig. 118, is a theoretical diagram. In order to 
 avoid any variations of the curve due to the differing conditions 
 of expansion in a compound engine, a steam-jacket maybe sup- 
 posed to be applied throughout. Let the first part of the curve, 
 e, f, represent expansion in the small or high pressure cylinder; 
 f^ c, the intermediate expansion or "drop" in the receiver; and 
 c, g, the expansion in the low pressure cylinder. Then <?, f, p, 
 t, k, will be the high pressure diagram; z, r, g, n, h, the low 
 pressure diagram; and the waste which has resulted from hav- 
 ing an intermediate drop, or "gap" is shown by the triangle, 
 
 f>c,p. 
 
 FIG. 1 1 8. 
 
 If, therefore, a "drop" can be avoided without altering the 
 total ratio of expansion, a saving to this extent will be effected. 
 When, however, the only convenient mode of avoiding a drop 
 would be to decrease the capacity of the large cylinder, and, 
 therefore, also to diminish the total ratio of expansion, there 
 would be no saving; since more area is cut off from the end of 
 the diagram than is saved in the middle, and the result is seen 
 in Fig. 119. 
 
 The values of the low pressure diagram are very nearly the same 
 in each case; in fact, if expansion followed Mariotte's law, they 
 would be exactly the same for the initial, and, therefore, the mean
 
 28 4 
 
 THE STEAM-ENGINE AND THE INDICATOR. 
 
 pressure in the low pressure cylinder would be in inverse pro- 
 portion to the capacity, and the product of these two would be 
 identical in each case. Here the matter is affected, however, 
 by the fact remarked upon under the head of "Wire-drawing 
 and Throttling' 1 ' 1 (Chapter IX, page 142, ante), that the loss due 
 to back pressure in the condenser is in proportion to the capacity 
 of the cylinder which exhausts into it. Thus, if the choice of 
 mean pressure is between 20 pounds on a small piston, or 10 
 pounds on one double the size, and if the back pressure is 4 
 pounds, then the former of these gives just one-third more 
 available work than the latter. The area below the line h n, in 
 Figs. 118 and 119, shows the amount of loss in each case due to 
 
 FIG. 119. 
 
 back pressure. While this area increases with any increase of 
 capacity of the low pressure cylinder, the area of the high pres- 
 sure diagram increases, also, by the lowering of the line z', ^, r, 
 and the best result will therefore be attained when this line z, p, 
 <:, is brought down just so far that any further reduction would 
 take more from the low pressure diagram than it would add to 
 the high. Where an expansion valve is used, on the other 
 hand, and intermediate expansion therefore prevented, the low 
 pressure cylinder may be made of such a capacity that the pres- 
 sure of steam in it at the end of the stroke shall be little, if at 
 all, higher than that in the condenser.
 
 VARIETIES OF STEAM ENGINES. 285 
 
 To Avoid Intermediate Expansion. 
 
 There are several arrangements in use by which intermediate 
 drop may be avoided altogether, or reduced to any desired ex- 
 tent, without diminishing the amount of expansion which takes 
 place after the steam leaves the small or high-pressure cylinder. 
 The commonest of these is that referred to by providing the 
 large or low-pressure cylinder with an expansion valve, by 
 which means its capacity up to the point of cut-off may be re- 
 duced to that of the high-pressure cylinder. 
 
 FIG. 120. 
 
 Another way of avoiding a drop of pressure is to make the 
 pistons begin and end the stroke together (see Figs. 106 and 
 108), and to exhaust directly from the high-pressure cylinder 
 into the low-pressure cylinder. In this class of engines the 
 intermediate receiver is done away with, and the passages by 
 which the steam exhausts from one cylinder to the other are 
 made as small as possible, one cylinder being even placed some- 
 times within the other (see Fig. 120.) 
 
 In this class of engines, when the exhaust-port of the high 
 pressure cylinder opens, the low pressure piston is at the end of
 
 286 
 
 THE STEAM-ENGINE AND THE INDICATOR. 
 
 its stroke, so that no expansion of the exhaust steam from the 
 high pressure cylinder can take place, except into the clearance 
 of the low pressure cylinder and the intermediate passages. As 
 the two pistons advance, simultaneously, the steam flows from 
 the high pressure cylinder to the larger cylinder, expanding 
 meanwhile. The communication between the cylinder is not 
 closed until the end of the stroke, or nearly so, and, conse- 
 quently, the lowest pressure of the exhaust in the high is the 
 same as the initial pressure in the low pressure cylinder (see 
 Diagram 107.) 
 
 Diagram, Fig. 121, is a theoretical one, on the assumption 
 that there is no loss of heat during the stroke, the steam being 
 
 FIG. 121. 
 
 expanded twelve times in a simple engine and condensing; V, 
 B, represents the total initial pressure of sixty pounds absolute; 
 B, e, the constant supply of steam before cut-off takes place; 
 e is the point of cut-off, being one-twelfth part of the stroke; 
 e, g, the expansion curve; g, V, represents the terminal pres- 
 sure, and V, V, the line of perfect vacuum. 
 
 Fig. 122 represents a theoretical diagram of a compound con- 
 densing engine. The line V, B, represents the initial pressure 
 of sixty pounds above perfect vacuum, B, e, the steam line 
 before cut-off, *?, A , is the expansion curve from the high pres- 
 sure cylinder, and g, n, the expansion curve formed by the 
 condensing low pressure cylinder; g, V, the terminal pressure
 
 VARIETIES OF STEAM ENGINES. 
 
 287 
 
 in the high pressure cylinder, and equal to 17.32 pounds above 
 a perfect vacuum, and V, n, the terminal pressure in low pres- 
 sure cylinder, and equal to five pounds. 
 
 It will be seen from the above that to compound an engine 
 by adding a second cylinder of about three and one-half times 
 the piston area, which is known as the low pressure cylinder, 
 into which the exhaust steam of the first or high pressure cyl- 
 inder, instead of being thrown away, is utilized, results in a 
 further amount of work being effected. The additional work 
 thus obtained is roughly proportional to the mean effective 
 
 FIG. 122. 
 
 pressure in the low pressure cylinder multiplied by the differ- 
 ences in area of the two pistons. By this means the power of 
 the engine is increased, and the steam, when finally exhausted, 
 is at a pressure so low that little or no unused work remains in 
 it. The maximum possibilities of economy are thus secured. 
 
 Diagram Fig. 123 was taken from a simple compound West- 
 inghouse engine developing 160 brake horse-power, actual 
 water consumption 25.5 pounds per hour. 
 
 Compound Condensing Engines. 
 
 Diagram, Fig. 124, was taken from a Westinghouse com- 
 pound condensing engine developing 200 brake horse-power, 
 actual water consumption of 19.62 pounds per hour.
 
 288 
 
 THE STEAM-ENGINE AND THE INDICATOR. 
 
 TABLE NO. 6. 
 
 TABLE OF ACTUAL STEAM CONSUMED PER INDICATED H. P. 
 Westinghouse Compound Engine, Cylinders 14" and 24" x 14". 
 
 By Test, under Varying Loads and Pressures. 
 Unjacketed and Uncorrected for Entrained Water. 
 
 February, 1888. 
 
 Non-condensing. Condensing. 
 
 Boiler Pressures. 
 
 Horse 
 Powers. 
 
 Boiler Pressures. 
 
 60 Ibs. 
 
 80 Ibs. 
 
 100 Ibs. 
 
 120 Ibs. 
 
 120 Ibs. 
 
 100 Ibs. 
 
 80 Ibs. 
 
 60 Ibs. 
 
 
 
 
 22.6 
 
 2IO 
 
 18.4 
 
 
 
 
 
 
 23.0 
 
 21.9 
 
 I 7 
 
 18.1 
 
 18.8 
 
 
 
 
 24.9 
 
 23-6 
 
 22.2 
 
 I 4 
 
 18.2 
 
 18.5 
 
 20. o 
 
 
 
 25-7 
 
 23-9 
 
 22.2 
 
 "5 
 
 18.2 
 
 18.6 
 
 19.6 
 
 20.5 
 
 26.9 
 
 25.2 
 
 24-9 
 
 22.4 
 
 IOO 
 
 18.3 
 
 18.6 
 
 19.7 
 
 20.3 
 
 27.7 
 
 25.2 
 
 25-1 
 
 2 4 .6 
 
 80 
 
 18.3 
 
 18.6 
 
 19.9 
 
 20.1 
 
 30.3 
 
 28.7 
 
 29.4 
 
 28.8 
 
 50 
 
 20.4 
 
 20.8 
 
 20.7 
 
 20.4 
 
 FIG. 123. 
 
 Diameter of high pressure cylinder in inches ........ 14 
 
 Diameter of low pressure cylinder in inches 24 
 
 Length of stroke in inches 14 
 
 Revolutions per minute 250 
 
 Boiler pressure per square inch in pounds 120 
 
 Water consumption per hour in pounds 25.5 
 
 Brake Horse-power 160
 
 VARIETIES OF STEAM ENGINES. 
 
 289 
 
 Diagrams Figs. 125 and 126 were taken from a compound 
 condensing engine. The mill was originally driven by a pair 
 of horizontal slide valve engines, with cut-off of the following 
 dimensions: 
 
 Diameter of cylinders in inches 24 
 
 Length of stroke in feet 4 
 
 In order to get good results, it was arranged to erect boilers 
 adapted to carry at least 160 pounds steam per square inch, and 
 to replace one of the twenty-four inch slide-valve cylinders by 
 a Corliss cylinder fourteen inches in diameter and four feet 
 stroke: the new cylinder was steam jacketed, and the cranks be- 
 ing at right angles, a receiver was placed between the engines. 
 
 FIG. 124. 
 
 This alteration has been found to .be a very great improve- 
 ment, and the following diagrams taken from the altered 
 engines, speak for themselves. 
 
 It will be seen that running sixty revolutions per minute, 
 and with 165 pounds of steam in the boiler, the non-condensing 
 Corliss cylinder indicates 125.2 horse-power, with a mean pres- 
 sure of fifty-six pounds, and the condensing cylinder 131.1 
 horse-power, with a mean pressure of 19.75 pounds, or, collect- 
 ively, 256.3 horse-power. About one pound of difference of 
 pressure is shown between the two cylinders. 
 19
 
 2QO 
 
 THE STEAM-ENGINE AND THE INDICATOR. 
 
 This engine has been frequently run up to 350 horse-power, 
 when all the mill machinery has been on at once. The con- 
 sumption of water so stated has been measured, and found to be 
 about thirteen pounds per hour, per indicated horse-power, 
 equivalent to a consumption of 1.3 pounds of coal per hour per 
 indicated horse-power, with a boiler evaporation of ten pounds 
 of water per pound of coal. The steam was very dry, and the 
 indicator cards account for but 10.33 pounds of water per hour 
 per horse-power developed. 
 
 FIG. 125. 
 
 Diagrams 126 were taken from a pair of engines connected at 
 right angles, using 1.7 pounds of coal per hour per horse-power; 
 the boilers evaporating 8.46 pounds of water with one pound 
 of coah 
 
 Early Compound Engines. 
 
 An old and comparatively little known work entitled "Reatil 
 de Decrets, Ordonnances, Instructions, Decisons Reglementaries, 
 sur les Machines a Feu et les Bateaux a Vapeur" by C. A. 
 Tremtsuk, published at Bordeaux in 1842, gives some interest- 
 ing particulars of the steamers plying at that date upon the 
 Gironde and the Garonne. Amongst these was the Union, set
 
 VARIETIES OF STEAM ENGINES. 
 
 291 
 
 to work in June, 1829, an( ^ which was fitted with a compound 
 engine constructed by Hallette, of Arras, this engine having 
 two inclined cylinders. 
 
 FIG. 126. 
 
 High pressure cylinder, 25 inches diameter. 
 Low pressure cylinder, 44 inches diameter. 
 Stroke of piston, 36 inches. 
 Revolutions per minute, 67. 
 
 Advantages of the Compound Steam Engine. 
 
 First. It furnishes a better working engine mechanically, 
 for utilizing the benefits of the expansion of high pressure 
 steam. This point will be very generally conceded. The ex- 
 pansion of steam is necessary to secure economy; but, if the 
 application of the principle be carried to the extent desired, the 
 great changes of pressure in the cylinder cause severe strains on 
 the main connections, and, although the latter be made unusu- 
 ally strong, it is frequently found expedient to reduce the
 
 292 THE STEAM-ENGINE AND THE INDICATOR. 
 
 pressure, and, necessarily, the measure of expansion, and so 
 increase the consumption of fuel in order to reduce the losses 
 caused by frequent repairs, but more particularly by the delays 
 they occasion. The compound engine, in any form, equalizes 
 the strains, and distributes the load. 
 
 Second. Independently of mechanical considerations, it is 
 more economical to use steam expansively in a compound 
 engine than in any form of the ordinary engine. 
 
 This point must be accepted as a fact by any one who will 
 examine the evidence available, but the abstract explanation of 
 the result is impossible by any of the laws heretofore laid down 
 in respect to the steam engine. It should be borne in mind 
 that, contrary to the opinion of many, there is no gain in power 
 by the addition of the small high pressure cylinder of the com- 
 pound engine, for the effective pressure upon its piston is only 
 the difference between that of the entering steam and that ad- 
 mitted to the second cylinder. There is, in fact,, a little power 
 lost in transferring the steam from one cylinder to the other. 
 
 It is not strange, then, that many engineers condemn the 
 compound engine, and declare, in spite of all failures, that the 
 same results can be produced in a single cylinder engine if it be 
 made of sufficient strength to withstand the unequal strains. 
 These engineers simply judge from the information they have 
 had the opportunity of acquiring. They have been taught that 
 the capacity of the cylinder is the measure of the steam used, 
 and reason that, if the compound engine gives no more power 
 with the same steam, it is a useless contrivance. No other con- 
 clusion could be reached on such an assumption. The error in 
 the reasoning lies in the fact that the volume of the cylinder is 
 not an accurate measure of the quantity of steam used by the 
 engine. This fact has been proved by experiment both at home 
 and abroad, but, strange to say, has never attracted much at- 
 tention. People will assume that steam can be measured by 
 the cylinderful as accurately as pease in a bushel ; but the fact 
 is, that the metal walls of a steam cylinder are at every stroke 
 so cooled by the performance of work, and by the low tempera- 
 ture during the exhaust, that the steam from the boiler, upon 
 entering, has two offices to perform, namely : 
 
 First. To reheat the surfaces.
 
 VARIETIES OF STEAM ENGINES. 393 
 
 Second. To fill the cylinder and maintain the desired pres- 
 sure. 
 
 In many cases it may require as much steam to do the first as 
 the last; and, as the steam for the first purpose is condensed, 
 that for the second will only fill the space, and, in fact, two 
 volumes of steam may enter into a vessel capable of holding but 
 one of a liquid or non-condensable gas. 
 
 Tyndall has found that aqueous vapor is one of the most 
 powerful radiators and absorbents of radiant heat known. Steam 
 when slightly chilled by the performance of work, is in respect 
 to heat in the same condition as the aqueous vapor of the atmo- 
 sphere; therefore, if steam enters a cylinder at a temperature of, 
 say, 280 degrees, and heats the metal surface to that point, when 
 such steam is exhausted and falls in pressure so that the tem- 
 perature is, say, only 130 degrees, the surfaces rapidly radiate 
 heat, which is absorbed by the steam and carried to waste, and 
 the next steam that enters has to reheat the surface, and an ad- 
 ditional quantity is required to fill the cylinder and do the work. 
 
 Experiments made show that the cylinder of a perfect engine 
 should be made of glass or other non-conducting material. Ex- 
 periments made by Mr. C. E. Emery, of New York, proved that 
 very nearly the same results could be obtained by the use of a 
 modification of the compound engine, which involved no diffi- 
 cult mechanical details. The transfer of heat from the metal 
 walls of the cylinder to the exhausting steam takes place in two 
 ways, namely: 
 
 First. By direct contact. 
 
 Second. By radiation. 
 
 The bulk of the steam can only be acted upon by radiation, 
 which, therefore, causes the material part of the loss. 
 
 It has been proved by experiment that the quantity of heat 
 transferred from a radiating to an absorbing body varies as the 
 square of the difference in temperature; so, taking the previous 
 case, namely, that the temperature of the metal surfaces of a 
 steam cylinder is 280 degrees, and that of the exhaust steam 130 
 degrees, the difference in temperature is 150 degrees; and, if we 
 use steam in two cylinders instead of one, we may reduce the 
 temperature in each to, say, one-half that amount, and the con- 
 densation will be as i 2 to 2 2 , or one-fourth as much in the two
 
 294 THE STEAM-ENGINE AND THE INDICATOR. 
 
 cylinders as in the single one, or not less than one-third as much 
 if an allowance be made for the increased surface hi the two. 
 This explanation shows that if the condensation in the single 
 cylinder be one-half the whole amount, two-thirds of this or 
 (/i x }==) one-third of the whole may be saved by a compound 
 engine, which calculation agrees with the facts, but varies, of 
 course, with changes in the condition. 
 
 Mr. Emery speaks of many compound engines that were so 
 constructed that they gave but little better results than a single 
 cylinder engine. During his experiments several improvements 
 applicable to the compound engine were worked out, which, 
 in connection with that principle, using a steam pressure of only 
 40 pounds per square inch, reduced the cost of the power in the 
 experimental engine from 39.2 pounds of feed water per hour 
 per horse-power to 23.6 pounds. This proportion of saving 
 would, in a large engine, reduce the cost to as nearly that 
 promised by theory as the most sanguine could expect; for 
 larger engines are positively known to be more economical than 
 small ones, which may be explained by the fact that the ratio 
 of internal surface to capacity decreases with the size of the 
 cylinder. The practical evidences of the advantages of the com- 
 pound engine are overpowering, as eighty per cent, of all the 
 large ocean steamships recently constructed abroad and at home 
 have such engines, and many of the largest establishments on 
 land also employ them. 
 
 Triple Expansion Engines. 
 
 The success of the triple expansion engine is now so well as- 
 sured, and all doubts as to its efficiency and good working are 
 so effectually dispelled, that it is without doubt the engine of 
 the day. It does not differ in any essential feature from the 
 ordinary compound engine, and its success is in no small meas- 
 ure due to the fact that most makers of the new type departed 
 as little as possible from their previous practice in its general 
 construction. The arguments for and against this new class of 
 engine bear a striking resemblance to those used in the well- 
 remembered warfare of compound versus expansion engines, and 
 the objections most strongly insisted on by the opponents of this 
 new system are just those used against the original compound
 
 VARIETIES OF STEAM ENGINES. 295 
 
 engine, and are rather the echo of old battle cries than the 
 sound of new ones. A few years' experience has demonstrated 
 that the triple expansion engine is more economical than the 
 ordinary compound engine; that the wear and tear is no more 
 but rather less, when three cranks are employed than with the 
 two of the ordinary compound, and that boilers of the common 
 marine design can be made to work satisfactorily at a pressure 
 of 150 pounds per square inch, and even higher, while with 
 ordinary care, their durability and good continued working are 
 not likely to be less than those of similar boilers pressed to 60 
 pounds per square inch under similar circumstances. Speaking 
 generally the consumption of fuel is 25 per cent less with a 
 triple expansion engine than with an ordinary compound engine 
 working under similar circumstances. That is, a triple expan- 
 sion engine, supplied with steam at 140 pounds pressure, uses 
 25 per cent, less weight of water per indicated horse-power than 
 an ordinary compound engine supplied with steam at, say, 90 
 pounds pressure, both engines being equally well designed, 
 manufactured and attended to. Also that a triple expansion 
 engine is more economical than an ordinary compound engine, 
 when both are supplied with steam at the same pressure, for all 
 pressures of 95 pounds and upwards, and especially so in the 
 case of large engines. Hence it may be taken that the superior 
 economy of the triple expansion engine, as now constructed, is 
 due to two causes, namely: 
 
 First. To the higher steam pressure used, and the higher 
 rate of expansion thereby possible. 
 
 Second. To the system whereby large initial strains and 
 large variations of temperature in the cylinders and large 
 "drops" in the receivers are avoided. 
 
 Increased pressure of steam is obtained by a very slight in- 
 crease of consumption of fuel, and the efficiency of steam rapidly 
 increases with increased pressure; hence, steam of high pressure 
 is more economical than that at a lower pressure. 
 
 For example: 
 
 (a) The total heat of evaporation of one pound of water from 
 100 degrees and at 276.2 degrees Fahrenheit (corresponding to 
 45 pounds pressure absolute) is 1166.2 units of heat from 32 de- 
 grees.
 
 296 THE STEAM-ENGINE AND THE INDICATOR. 
 
 () From TOO degrees and at 322.4 (corresponding to 90 
 pounds absolute) is 1180.3 un its of heat. 
 
 (c) From 100 degrees and at 346.2 (corresponding to 125 
 pounds absolute) is 1187.5 units of heat. 
 
 (d} From 100 degrees and at 354.8 (corresponding to 140 
 pounds absolute) is 1190.1 units of heat. 
 
 (e) From 100 degrees and at 378.5 (corresponding to 190 
 pounds absolute) is 1197.4 units of heat. 
 
 Suppose in each case the steam to be expanded to a terminal 
 pressure of 10 pounds absolute, the rates of expansion will then 
 be 4.5, 9, 14 and 19, respectively; and the mean pressure corre- 
 sponding to these initial pressures and rates of expansion will 
 be 25 pounds, 32 pounds, 36 pounds, and 39 pounds respectively. 
 If the volume of a pound of steam varied exactly in the inverse 
 ratio of the pressure, these figures would represent the relative 
 values of the efficiency of the steam at the various pressures. 
 But taken exactly, the relative values are 25, 33.3, 38.5 and 
 42.6, thus showing as follows: 
 
 First. That a pound of steam at 90 pounds pressure is 
 capable of doing 33 per cent, more work than a pound at 45 
 pounds. 
 
 Second. A pound of steam at 140 pounds pressure 16 per cent, 
 more work than a pound at 90 pounds. 
 
 Third. A pound of steam at 190 pounds pressure 10.6 per 
 cent., more work than a pound at 140 pounds pressure. 
 
 In other words, an engine using steam at 140 pounds pressure 
 should, apart from any practical considerations, consume six- 
 teen per cent, less fuel than one using steam at 90 pounds; and 
 again, an engine using steam at 190 pounds should consume 
 twenty-eight per cent, less fuel than one using steam at 90 
 pounds, and ten and six-tenths per cent, less fuel than one using 
 steam at 140 pounds pressure. 
 
 Looking to see how far practice agrees with these results 
 and comparing the ordinary compound engine, using steam at 
 90 pounds, with the triple expansion engine using steam at 
 140 pounds pressure, it will be found that the latter gives a 
 greater economy than theory shows should be due to the in- 
 creased pressure. It follows, then, that there is some other 
 cause operating to produce the economic results shown in every
 
 VARIETIES OF STEAM ENGINES. 297 
 
 day practice with this new engine, for there is now no question 
 that the saving in fuel effected by a triple expansion engine 
 using steam and expanding u or 12 times, is about 25 percent, 
 compared with that used by an ordinary compound engine of 
 the same power, using steam at 90 pounds, and expanding 8 to 
 9 times. The other cause, or rather causes, are not remote, for 
 it is to be noticed at once that since by using steam in the' two 
 cylinders of a compound engine, the large variation in temper- 
 ature in the cylinder of the expansive engine was avoided (and 
 this, doubtless, was one of the chief causes of its superior 
 economy over the latter), then, by using three cylinders for the 
 higher pressures, a similar result would be obtained. Further, 
 as the ordinary compound engine is not subject to such severe 
 initial and working strains as prevail in expansive engines of 
 the same power, and using steam of the same pressure, so in 
 the triple expansion engine with three cranks, these strains are 
 still further reduced. In other words, by extending those lead- 
 ing features of the compound engine which conduced to its 
 economy, the engineers of to-day have achieved, with the triple 
 expansion, a victory similar to that obtained about twenty years 
 ago by their predecessors, but with somewhat less brilliant re- 
 sults; and it is not difficult to see that any further advances 
 must meet with still less gain. Until science and skill have 
 discovered new materials or other applications of old ones, there 
 will not be much practical advantage in using steam at higher 
 pressures than now obtained, and 200 pounds absolute pressure 
 seems about the limit at which theoretical economy is swallowed 
 up by practical losses. 
 
 It has been shown in practice that the saving in fuel is from 
 20 to 30 per cent, by the use of triple expansion over that of 
 compound engines, independent of the more even distribution 
 of pressure; also that the resistance of the slide valves is very 
 materially lessened, and the losses due to mechanical causes 
 decreased; also experience has shown that the wear and tear of 
 the triple expansion engine with three cranks is very consider- 
 ably less than with the ordinary two crank compound engine of 
 the same power and stroke, and no doubt this is due to those 
 causes already shown to exist with this class of engine. 
 
 Diagrams Fig. 127 were taken from a compound condensing,
 
 298 THE STEAM-ENGINE AND THE INDICATOR. 
 
 triple-expansion engine, developing 357 horse-power, with a 
 consumption of 1.3 pounds of coal per hour per horse-power. 
 Steam pressure in boiler, 155 pounds above the atmosphere. 
 
 FIGS. 127. 
 
 Diagrams Fig. 128 were also taken from a horizontal com- 
 pound-condensing, triple-expansion engine. The three cylin- 
 ders are placed one above the other, that is to say, the low 
 pressure cylinder is placed on the bottom next the intermediate, 
 and on top of this the high pressure cylinder: all the piston rods 
 are connected to one and the same crosshead. For boldness of 
 design this engine is unique. 
 
 The cylinders are 8^ inches, 13^ inches, and 21 inches in 
 diameter respectively, with a common stroke of 48 inches. 
 
 The valves of the high cylinder are of the Corliss type; the 
 intermediate cylinder is fitted with two slides and cut-off valves. 
 These valves can be regulated to cut-off earlier or later, to
 
 VARIETIES OF STEAM ENGINES. 299 
 
 equalize the amount of work done by the respective cylinders. 
 To facilitate adjustment the cut-off spindle has a screw index 
 wheel. 
 
 The low pressure cylinder is fitted with an ordinary slide 
 valve worked by an eccentric. 
 
 The diagrams were taken before the cylinders were lagged. 
 The small fall of steam pressure between the steam supply pipe 
 and the high pressure piston is worthy of notice, as well as the 
 
 FIG. 128. 
 
 Line of Stem Treg rare in Pipe Line of Preggnre in Steam Plpp 
 
 Low Pressure Cylinder. 21 j dla. Scalo Vao 
 
 parallel admission steam line into the high pressure Corliss cyl- 
 inder. The diagrams were taken with the full load of 187 
 horse-power on the engine at 63 revolutions per minute, but 
 under ordinary circumstances the engine works in conjunction 
 with a turbine, the latter driving from 20 to 70 horse-power ac- 
 cording to the height of the water in the supply dam. The 
 average load on the engine will be 150 to 160 horse-power. 
 
 There is a blow-through valve from the high pressure to the 
 intermediate cylinder, to get the strain fairly applied to the 
 middle of the cross-head in starting. 
 
 Chart of Relative Economy, Under Varying Loads. 
 Diagram, Fig. 129, represents the performance of a single cyl- 
 inder non-condensing engine, as contrasted with the compound 
 engine, non-condensing and condensing.
 
 3 oo 
 
 THE STEAM-ENGINE AND 
 
 :ATOR. 
 
 To fully realize what this economy means, T append the best 
 recorded duty in pounds of water per horse-power per hour of 
 some of the best types of engines working under the most favor- 
 able conditions: 
 
 FIG. 129. 
 
 Pumping engines, compound condensing 15 to 18 pounds. 
 
 Westinghouse engines, " 17 to 19 " 
 
 Corliss engines, 18 to 22 " 
 
 Westinghouse engines, compound non-condensing . . 22 to 24 
 
 Corliss engines, compound and condensing 17 to 19 
 
 Corliss engines, condensing 22 
 
 Corliss engines, non-condensing 28 to 35 " 
 
 Buckeye engines, non-condensing 25 to 30 " 
 
 It must be borne in mind that the duties above named are 
 measured by water fed to boilers. It is customary with some 
 engine builders to rate their consumption by computing from 
 the indicator diagrams. This, is misleading, as an engine show- 
 ing 22 to 24 pounds by the indicator card will actually consume 
 at least 28 to 32 pounds of weighed feed water. 
 
 Compound Locomotives. 
 
 Compound locomotives were first introduced in 1850 on the 
 Eastern Counties (now the Great Eastern) Railway, England, 
 James Samuel, superintendent, the system being due to John 
 Nicholson, engineer. 
 
 Each locomotive was fitted with two cylinders having piston
 
 VARIETIES OF STEAM ENGINES. 301 
 
 areas approximately as i to 2, the strokes being the same, and 
 the pistons being coupled to cranks at right angles in the ordi- 
 nary way, see Fig. no. Steam from the boiler was admitted 
 to the smaller cylinder up to half stroke (or less, according to 
 the power required), while at half stroke a supplementary valve 
 opened up a communication between that end of the small 
 cylinder, which had been receiving steam, and the larger cylin- 
 der, the expansion during the greater part of the remainder 
 of the stroke of the small piston going on in both cylinders 
 simultaneously, see Figs. 113 and 114. Near the end of the 
 stroke of the small piston, however, the communication between 
 the two cylinders was closed, and the main valve of the small 
 cylinder opening to the exhaust, such steam as remained in that 
 cylinder passed to the blast nozzle in the ordinary way. By 
 this time the piston of the larger cylinder had reached half 
 stroke, the remainder of the stroke being completed by the ex- 
 pansion of the steam then shut into that cylinder. To facilitate 
 the handling of the engine at starting, provision was made for 
 shutting off the communication between the cylinders, and for 
 admitting steam direct to the valve chest of the low pressure 
 cylinder. 
 
 With cylinders of the proportion above named, it will be seen 
 that approximately, and neglecting the effect of clearances and 
 steam passages with the cut-off at half stroke in the small 
 cylinder, half the steam used was expanded four- fold and half 
 of it eight-fold. One of Mr. Nicholson's objects in designing 
 this particular system of working appears to have been to secure 
 the discharge of a portion of the steam at such a pressure as to 
 maintain an effective blast, the remaining half being expanded 
 down to a very low pressure. 
 
 The next attempt at compounding locomotives was made by 
 M. Jules Morandiere of the Northern Railway of France, in 
 November, 1866, on a locomotive having eight drivers, the 
 drivers being formed in two groups two pairs in each group. 
 The wheels forming the front group were driven by a pair of 
 outside cylinders placed as usual, while the axle of the front 
 pair of wheels of the hind group was furnished with a central 
 crank driven by a single cylinder (same as the present Webb 
 system) placed under the boiler. The steam was first admitted
 
 3 02 
 
 THE STEAM-ENGINE AND THE INDICATOR. 
 
 into the single cylinder, from which it was exhausted into two 
 outside cylinders. 
 
 In July, 1876, M. Anatole Mallet, of Paris, France, intro- 
 duced on the Bayonne and Biarritz Railway, his system of com- 
 pound locomotives, three being put in service. They proved 
 very successful, and were followed by others the ensuing year. 
 One of the chief features of M. Mallet's system was the provision 
 of a special arrangement of distributing valve, by which the 
 steam from the boiler could be admitted either to the high 
 
 FIG. 130. 
 
 pressure cylinder only, or to both cylinders when required for 
 starting; the distributing valve also effecting the direct dis- 
 charge jnto the stack of the exhaust from the small cylinder 
 when the engine was working non-compound. In M. Mallet's 
 earlier engines, when working non-compound, the steam from 
 the boiler passed direct to the large cylinder, but subsequently 
 he fitted his locomotives with a reducing valve, through which 
 the steam on its way from the boiler to the large cylinder had 
 to pass, this valve being set to give in the cylinder a certain 
 fraction of the boiler pressure, thus equalizing the work done in 
 the two cylinders. Another special feature of M. Mallet's loco- 
 motive is the reversing gear, which is so arranged that, while
 
 VARIETIES OF STEAM ENGINES. 303 
 
 the gear for the two engines of the locomotive can be reversed 
 simultaneously, the cut-offs in the high and low pressure cylin- 
 ders can be adjusted independently, so as to equalize the work. 
 
 Diagrams Fig. 130 were taken with a boiler pressure of 150 
 pounds per square inch above the atmosphere, the cylinder be- 
 ing placed as in the ordinary locomotives. 
 
 In 1878 the Paris and Orleans Railway altered some of their 
 express locomotives, having io}4 inch cylinders, by replacing 
 the right-hand cylinder with a 21^ inch cylinder, the stroke 
 being 24 inches; diagram Figure 131 was taken from one of 
 these altered locomotives. 
 
 FIG. 131. 
 
 M. Mallet's system also includes an arrangement of a pair of 
 tandem compounds namely, one high pressure and one low 
 pressure cylinder on each side of the locomotive, the two pistons 
 being on one rod; this arrangement is peculiarly fitted for ap- 
 plication to outside cylinder locomotives. 
 
 M. Mallet's experiments since 1872 established the fact that 
 compound locomotives under good conditions gave an economy 
 of fuel of twenty per cent. ; this is based on a pressure not ex- 
 ceeding 120 pounds; a higher boiler pressure might have shown 
 better results. 
 
 In 1881-82 Mr. Francis W. Webb, of the London and North- 
 Western Railway, England, after having a compound locomotive 
 on M. Mallet's system running for five years, on the Ashly and 
 Nuneaton branch of the above line, found the results obtained 
 with this locomotive to be so satisfactory, that he designed and 
 patened an improved compound locomotive. This has three 
 cylinders, two high pressure outside cylinders of equal size, ar- 
 ranged to drive the hind driving axle, and one low pressure
 
 304 THE STEAM-ENGINE AND THE INDICATOR. 
 
 cylinder placed inside the frames underneath the smoke-box, 
 acting on a central crank on the front driving axle. The high 
 pressure cylinders are u ^ inches, and the low pressure cylinder 
 26 inches in diameter, the stroke in both cases is 24 inches; the 
 driving wheels are 6 feet 6 inches in diameter. By the above 
 arrangement Mr. Webb obtains the advantages of a coupled 
 locomotive without the use of coupling rods; in other words, he 
 has two pairs of single drivers on one locomotive. 
 
 These locomotives proved so successful that (to meet heavier 
 loads) the high pressure cylinders have been increased to 14 
 inches diameter, and the low pressure cylinder to 30 inches; the 
 driving wheels have been reduced to 75 inches, and the leading 
 wheels to 45 inches diameter. The total wheel base is 18' i". 
 
 The heating surface of flues in square feet = 1224.4. The 
 heating surface of fire box in square feet = 159.1. Total heat- 
 ing surface in square feet, 1401.5 Fire grate, in square feet, 
 
 FIG. 132. 
 
 20.5. Ratio of fire grate area to heating surface area i: 68.36. 
 Pressure per square inch in the boiler, 175 Ibs.. Total weight, 
 42 tons 10 cwt. 
 
 The Pennsylvania Railroad imported early in 1889 one of 
 these locomotives for trial On their line. It was built by Beyer, 
 Peacock & Co.. England, and is known as the "Dreadnaught" 
 class, and is named "Pennsylvania." 
 
 One of the Webb compound locomotives runs the Scotch ex- 
 press from Euston (London) to Carlisle, a continuous trip of 
 300^ miles, with an average load (including locomotive and 
 tender) of 207 tons. The consumption of fuel averages 29.2 
 pounds per mile, and the evaporation of water is 9.49 pounds 
 per pound of coal, the average speed being 44.7 miles per 
 hour. 
 
 Indicator diagram Fig. 132 was taken from one of the com-
 
 VARIETIES OF STEAM ENGINES. 305 
 
 pound locomotives with 13 inch high pressure, and 26 inch low 
 pressure cylinder. 
 
 Speed slow; Full gear; Boiler pressure 150 pounds; Indicator 
 scale 56 pounds = i inch. 
 
 The following diagram, Figure 133, was taken when the speed 
 was fifty miles per hour, boiler pressure 150 pounds, cutting off 
 at thirty-five per cent, of the stroke. 
 
 Speed 50 miles per hour; Boiler pressure 150 pounds per 
 square inch ; Cut-off, 35 per cent, of the stroke. 
 
 It will be seen that the work performed is nearly all done by 
 the high pressure engines, and of course there is a great drop in 
 the receiver. 
 
 FIG. 133. 
 
 The above diagrams, in view of the great publicity given to 
 these improved locomotives, do not bear out the assertions of 
 economy made for them. The work in the low pressure cylin- 
 der, at the above speed, is a mere trifle, scarcely justifying the 
 great additional complication and weight entailed. On this 
 point multiplication of parts, and crowding necessary to get 
 them in there is great objection, and it will require a much 
 longer experience and impartial judgment to determine whether 
 this type of locomotive is desirable. There is another serious 
 drawback, as I understand the Webb compound locomotive; 
 there is no arrangement for exhausting direct from the high 
 pressure cylinder into the stack; therefore, in starting, the 
 engine has to back the train first, to get rid of the accumulated 
 exhaust steam in the low pressure cylinder. 
 
 T. W. Worsdell, superintendent of the Great Eastern Rail- 
 way, England, patented a compound locomotive with inside 
 cylinders, similar to the Mallet type, the high pressure cylinder 
 being 18 inches diameter and the low pressure cylinder 26 
 inches diameter, with a common stroke of 24 inches. 
 
 The cylinders have the valve chests on top of the cylinder, 
 
 20
 
 306 THE STEAM-ENGINE AND THE INDICATOR. 
 
 the exhaust steam from the high pressure cylinder traversing 
 an arched pipe in the smoke-box on its way to the low pressure 
 valve chest. In this arched pipe is introduced the "intercepting 
 valve," which, with its adjunct, the starting valve, forms one of 
 the chief features in Mr. Worsdell's system of compound locomo- 
 tives. 
 
 The intercepting valve is a flap valve situated in a chamber 
 on the line of the high pressure cylinder exhaust pipe; the 
 normal position of this valve being open, except when starting. 
 The spindle on which this flap valve is hinged, passes out 
 through the side of the smoke box and carries at its outer end 
 an arm which enters a slot in the rod of a piston, which works 
 in a small c)dinder forming part of the starting valve casing. 
 This piston has some small holes through it. The starting 
 valve is a double one, the first movement of the spindle opening 
 the small valve only, while a further movement will open the 
 larger valve, which is then approximately balanced. Both 
 valves are normally kept up to their seats by spring pressure. 
 By means of a branch pipe the starting valve casing is placed in 
 communication with the steam pipe leading from the regulator 
 steam valve to the high pressure cylinder. 
 
 The action of the arrangement we have just described, is as 
 follows: If the engine happens to have stopped in such a 
 position that it does not start again when steam is turned on in 
 the ordinary way, the engineer pulls open the starting valve, 
 thus allowing steam from the main steam pipe to act against 
 the small piston which we have already mentioned as working 
 in a prolongation of the starting valve casing. The pressure of 
 steam on the piston uncovers a port on the upper side of the 
 cylinder in which the piston works. This port is covered by 
 a small spring loaded valve, which is raised by the steam, the 
 latter thus getting access through a bye pass to the pipe com- 
 municating with the intercepting valve chamber. At the same 
 time the forward motion of the small piston raises the inter- 
 cepting valve, and closes the communication with the high 
 pressure cylinder exhaust, and thus the steam admitted by the 
 starting valve to the intercepting valve chamber, can only get 
 access to the valve chest of the low pressure cylinder. When 
 the engine has started, the exhaust from the high pressure
 
 VARIETIES OF STEAM ENGINES. 
 
 307 
 
 cylinder, of course, acts on the upper side of the intercepting 
 valve, re-opening that valve, carrying back the starting valve 
 piston, and restoring the parts generally to the positions they 
 occupied before the starting valve was opened. These various 
 movements are perhaps tedious to describe, but the whole oper- 
 ation is exceedingly simple, and the arrangements act exceed- 
 ingly well and promptly, enabling these engines to be handled 
 as easily as non-compound engines. The low pressure cylinder 
 
 B16O 
 
 Speed 10 miles per hour. Cut-off 75 per cent, of stroke. 
 
 Horse-power of high pressure cylinder 102.3 
 
 Horse-power of low pressure cylinder . 114.8 
 
 Total indicated horse-power 217.1 
 
 Boiler pressure above atmosphere, 150 pounds. 
 
 is fitted with large spring loaded relief valves, so as to prevent 
 excessive steam pressure being exerted on the low pressure 
 piston; but as a matter of fact these valves rarely come into 
 action, the small quantity of steam which it is necessary to
 
 308 
 
 THE STEAM-ENGINE AND THE INDICATOR. 
 
 admit by the starting valve, being easily controlled by the 
 engineer. 
 
 The engines are fitted with Joy's valve-gear, and a differential 
 adjustment of the quadrants, in which the expansion block- 
 work insures such a control of the point of cut-off in the two 
 cylinders, as to secure a very close approximation to equality of 
 work. This result is well shown by the indicator diagrams: 
 Figs. 134 and 135. 
 
 FIG. 135. 
 
 1 2 3 4 5 6 7 8 9 1O 
 
 160 
 150 
 
 120 
 
 70 
 6O 
 50 
 40 
 30 
 20 
 1O 
 A O 
 
 10 
 V 15 
 
 
 mm, 
 
 Speed 55 miles per hour. Cut-off 75 per cent, of stroke. 
 
 Horse-power of high pressure cylinder 395-3 
 
 Horse-power of low pressure cylinder 368.3 
 
 763-6 
 
 This high speed diagram shows the work fairly divided be- 
 tween the two cylinders, and it also shows the result of linking 
 up both engines to cut-off at three-quarter stroke, and is in- 
 structive as showing what might be expected from bringing up 
 the low pressure gear of a Webb locomotive until the work at 
 speeds was nearly divided.
 
 VARIETIES OF STEAM ENGINES. 309 
 
 On an up grade with a heavy train, necessitating a late cut- 
 off in the high pressure cylinder, owing to the valve gear in 
 both engines being connected, the cut-off in the low pressure 
 cylinder is late also, and there is a serious loss from drop in the 
 receiver, but the two cylinders assist one another in their work. 
 
 This locomotive runs the newspaper express of twelve coaches, 
 between Newcastle and Edinburgh, and on the round trip, con- 
 sumes only 22.5 pounds of coal per mile, this coal being care- 
 fully weighed; whereas, the average consumption of these 
 trains, with ordinary locomotives, is 30 pounds per mile, showing 
 a saving for the former of twenty-five per cent. 
 
 In this county the compound locomotives tried on the Boston 
 and Albany Railroad have proved a failure as economizers of 
 fuel, and have been changed into the ordinary form. They had 
 four cylinders; large cylinders 20 inches by 26, small cylinders 
 12 inches by 26 inches, placed one in front of the other with the 
 same piston-rod, or "tandem" as it is called. They failed 
 simply for the reason that they were more expensive to maintain 
 than the ordinary locomotives, without showing any correspond- 
 ing economy. 
 
 Mr. A. B. Underhill, superintendent of motive power of the 
 road, says "The locomotive worked well, but we could get no 
 economy. Our road has heavy grades and in working direct 
 steam, in the cylinders, on the grades, we lost more than we 
 gained by compounding on the levels." "lam a good deal 
 skeptical about Compound Engines being economical for rail- 
 way service."
 
 CHAPTER XIV. 
 
 GAS-ENGINES. 
 History of Gas-Engines. 
 
 AT the present time, when gas-engines are coming into gen- 
 eral use for many purposes, a brief account of them may prove 
 interesting. 
 
 An engine driven by the explosion of a mixture of coal-gas 
 and atmospheric air was exhibited by Dr. Alfred Drake, of 
 Philadelphia, at the New York Crystal Palace, in 1855. The 
 principal feature in Dr. Drake's engine was the means employed 
 to light the mixture of gas and air within the cylinder, which 
 was done in the following manner: At two points, one for each 
 stroke, a hole was formed in the cylinder, the distance of these 
 holes from the ends of the cylinder corresponding with the 
 space into which the mixture was to be admitted before it was 
 exploded. These holes were each furnished with stuffing-boxes, 
 and in each of these stuffing-boxes was placed a cast-iron cup, 
 or thimble, the solid end of which projected into the shell of the 
 cylinder, so as to be just clear of the bore. In each of these 
 thimbles a jet of gas and air was kept constantly burning, and 
 by this means the ends of the thimbles were maintained at a 
 red heat. When, in the course of its stroke, the piston passed 
 over one of these thimbles, the mixture of gas and air which 
 had been admitted behind it came in contact with the red-hot 
 surface and was instantly ignited. The explosive mixture was 
 admitted to and released from the cylinder by ordinary double- 
 beat valves. 
 
 The air and gas were slightly compressed during their mix- 
 ture by an air-pump furnished with suitable stop-cocks, by 
 means of which the proportions of the gas and air could be reg- 
 ulated. The air-pump was worked by hand, in order to obtain 
 a supply of the explosive mixture for starting the engine; after- 
 wards it was run by the engine itself. The explosive mixture 
 used consisted of one-tenth coal-gas, and nine-tenths atmos-
 
 GAS-ENGINES. 311 
 
 pheric air, and Dr. Drake considered that, when this was ig- 
 nited, an initial pressure of about 150 pounds per square inch 
 was obtained. 
 
 The ignition of the gas in the cylinder caused considerable 
 heat to be evolved. In Dr. Drake's engine and cylinder, the cyl- 
 inder covers, piston, and piston-rods, were all made hollow, and 
 through them a constant stream of water was forced. By this 
 means they were kept moderately cool. The speed of the 
 engine was controlled by a throttle valve connected with a gov- 
 ernor, as i-n the ordinary steam-engine. This engine did not 
 come into general use at that time, from the excessive price of 
 gas ($4.00 per 1000 cubic feet) and further from the death of Dr. 
 Drake. It was followed by the Lenoir and Hugon gas-engines 
 of Paris, the latter' s engine requiring 74 cubic feet of gas per 
 hour, per horse-power, or about ten pounds of coal per hour, 
 per horse-power. 
 
 At the Paris Exhibition Otto and Langen's gas-engine was 
 shown. The consumption of gas was about 30 cubic feet per 
 hour, per horse-power. In this engine gas mixed with atmos- 
 pheric air is exploded, as in the common forms of gas-engine, 
 but instead of the pressure being imparted to a crank in the 
 usual manner, there is no resistance opposed to the movement 
 of the piston at the moment of explosion, but it is shot up in 
 the cylinder like a shot propelled from a gun, and the vacuum 
 produced by the explosion and also by momentum of the piston 
 is the moving force. The object of this arrangement is to 
 prevent an inconvenient accumulation of heat in the cylinder. 
 The gas used is coal-gas, and is ignited without the aid of 
 electricity. 
 
 Prior to 1876 many attempts had been made to produce a sat- 
 isfactory gas-engine, but all of them, including the previous 
 efforts of Otto himself, fell short of practical success, as they 
 were somewhat noisy. Otto, on May I7th, 1876, invented im- 
 provements in gas-engines of a most important character, to wit: 
 
 First. The introduction of a body of inert gas between the 
 piston and the combustible mixture by which it is impelled. 
 
 Second. The compression of the charge in the cylinder by 
 means of the return stroke. 
 
 This engine is known as the Otto "silent" gas-engine, and
 
 312 THE STEAM-ENGINE AND THE INDICATOR. 
 
 in it the violent shocks, so objectionable in former engines, are 
 avoided. 
 
 Considering that in the employment of gas-engines fuel is 
 not being consumed when the engine is not in actual operation, 
 it is evident that they form economical motors where small 
 powers are required. Further advantages are that they occupy 
 small space, are ready at a moment's notice, avoid any risk and 
 danger of explosion, reduce cost of insurance, and allow insur- 
 ance to be effected in places where, with a steam-engine and 
 boiler, companies would not undertake it. They need no special 
 buildings or chimney, and do not make the premises where they 
 are used uncomfortable with heat, dust and cinders. 
 
 Gas-engines will, before long, come into extensive use, not 
 only as supplementers to some extent of steam-engines, but 
 also as affording a cheap and efficient motive power in a great 
 number of places where the use of steam is difficult or impossi- 
 ble. It is obviously to the interest of gas companies and gas 
 managers to forward their employment as much as possible, 
 because they not only increase consumption of gas, but by using 
 it chiefly during the hours of daylight, no corresponding in- 
 crease of capital expenditure is involved; and their extended 
 use would not only benefit gas manufacturers, but also gas con- 
 sumers in general, by reducing the cost of making the gas by 
 increasing its consumption. 
 
 The problem of the conversion of heat into mechanical work 
 has been partially solved by the steam-engine, but its efficiency 
 is so low that it can not be considered as complete. Hot air, in 
 the past, has been looked upon as a possible advance, but owing 
 to many mechanical difficulties it has long been deemed useless 
 to look in that direction for better results. The great progress 
 recently made in gas-engines, from the stage of an interesting 
 but troublesome toy to a practical and powerful rival of the 
 steam-engine, has shown that air might, after all, be the chief 
 motive power of the future. 
 
 Gas- Engines. 
 
 Before proceeding to give an account of the early history of 
 these engines, I will preface it with the theory of the gas- 
 engine by M. Dugald Clerk, an expert in these motors.
 
 GAS-ENGINES. 313 
 
 There are three distinct types, of gas-engines at the present 
 time, as follows: 
 
 First: An engine drawing into the cylinder gas and air at 
 atmospheric pressure for a portion of its stroke, cutting off com- 
 munication with the outer atmosphere, and immediately ignit- 
 ing the mixture, the piston being pushed forward by the pres- 
 sure of the ignited gases during the remainder of its stroke. 
 The return stroke discharges the products of combustion. 
 
 Second: An engine in which a mixture of gas and air is 
 drawn into a pump, and discharged by the return stroke into a 
 reservoir in a state of compression. From the reservoir the 
 mixture enters a cylinder, being ignited as it enters, and with- 
 out rise in pressure, but simply increased in volume, following 
 the piston as it moves forward. The return stroke discharges 
 the products of combustion. 
 
 Third: An engine in which a mixture of gas and air is 
 compressed, or introduced under pressure into a cylinder or 
 space at the end of a cylinder, and then ignited. While the 
 volume remains constant the pressure increases. Under this 
 increased pressure the piston moves forward, and on the return 
 stroke exhausts. Types one and three are explosion engines, 
 the volume of the mixture remaining constant while the pres- 
 sure increases. Type number two is a gradual combustion 
 engine, in which the pressure remains constant, but the volume 
 increases. Calculating the power to be obtained from each of 
 these methods, supposing no loss of heat to the cylinder, it was 
 found that an engine of the first type using 100 heat-units 
 would convert 21 units into mechanical work, in the second 
 type 36 units, and in the third type 45 units. The great ad- 
 vantage of compression was clearly seen by the simple operation 
 of compression before heating, the last engine giving for the 
 same expenditure of heat 2. i times as much work as the first. 
 In any gas-engine compression before ignition, (igniting at 
 constant volume and expanding to the volume as before ignition), 
 the possible duty, D, was determined by the atmospheric ab- 
 solute temperature after compresssion, T; and hence 
 
 whatever might be the maximum temperature after ignition.
 
 314 THE STEAM-ENGINE AND THE INDICATOR. 
 
 In the formula D = duty, T= temperature after compres- 
 sion, t = temperature before compression. Increasing' the 
 temperature of ignition increased the power of the engine, but 
 it did not cause the conversion of a greater portion of heat into 
 work. That is to say, the possible duty of the engine was de- 
 termined solely by the amount of compression before ignition. 
 Compression made it possible to obtain from heated air a great 
 amount of work with but a small movement of piston, the 
 smaller volume giving greater pressures and thus rendering the 
 power developed mechanically available. Seeing the great dif- 
 ference produced between types one and three by the simple 
 difference in the cycle of operation when there was no loss of 
 heat through the outside of the cylinder, the questions arose: 
 which engine in actual practice, (with the cylinder kept cold 
 by water) would come nearest to this theory? In which of 
 the engines would there be the smallest loss of heat? Compar- 
 ing the two engines, with equal movements of piston, it was 
 found that the compression engine had the advantage of a lower 
 average temperature, and a greater amount of work done; also 
 of less surface exposed to flame, consequently it lost less heat in 
 the cylinder. Taking all- the circumstances into consideration, 
 it was certainly not over-estimating the advantage of the com- 
 pression engine to say that it would, under practical conditions, 
 give for a certain amount of heat three times the work it was 
 possible to get from an engine not using compression. 
 
 It is interesting to calculate the amounts of gas required by 
 the three types under the supposed conditions. Taking the 
 amount of heat evolved by one cubic foot of average coal gas as 
 equivalent to 505,000 foot-pounds, and calculating the gas re- 
 quired if all the heat were converted into work, it was found to 
 be 3.92 cubic feet per hour per horse-power. Therefore, the 
 amounts of gas required by the three types of engines would be: 
 
 Type one 3 ' 92 = 18.3 cubic feet per hour per horse-power. 
 
 O.2O 
 
 Type two 332- = 10.9 cubic feet per hour per horse-power. 
 0.36 
 
 Type three 2J2? = 8.6 cubic feet per hour per horse-power. 
 0-45 
 
 Comparing these figures with results obtained in practice
 
 GAS-ENGINES. 315 
 
 from the three types of engine losing heat through the sides of 
 the cylinder, it was ascertained that the amount of gas con- 
 sumed was as follows: Type one (Lenoir) 95 cubic feet per hour, 
 per indicated horse-power; (Hugon) 85 cubic feet per hour, per 
 indicated horse-power. Type two (Brayton) 50 cubic feet per 
 hour, per indicated horse-power. Type three (Otto) 20 cubic 
 feet per hour, per indicated horse-power. 
 
 It will be seen that the order of consumption coincided with 
 the theory. The Otto engine converted about 18 per cent, of 
 the heat used by it into work, while the Hugon engine only 
 converted 3.9 per cent. Taking the loss of heat to the cylinder 
 as given by the comparison of the adiabatic line of fall of tem- 
 perature with the actual line of fall as shown on the indicator 
 diagram, it appeared much less than was really the case, as 
 shown by the gas consumed by the engine. The maximum 
 pressure produced was much less than would be expected from 
 the amount of gas present. This was due to the limiting effect 
 of chemical dissociation. The gas-engine presented a more 
 complicated problem than a hot-air engine using air heated to 
 the same degree. Analyzing the disposal of 100 heat units by 
 Clerk's gas engine, it was found to convert 17.8 into work to 
 discharge 29.3 with the exhaust gases, and to lose through the 
 sides of the cylinder and piston 52.9 units. About one-half of 
 the whole heat used passed through the cylinder, and was ex- 
 pended in heating the water-jacket. St. Claire Deville had 
 shown that water was decomposed into its constituents at a 
 comparatively low temperature, considerable decomposition 
 taking place at 1200 degrees Centigrade (2192 Fahr.). The 
 cause of so near an approach to the line of theoretical fall, as 
 shown by the actual indicator diagram, was simply the continu- 
 ous combination of the dissociated gases. At a maximum tem- 
 perature of about 1600 deg. Cent. (2912 Fahr.), complete com- 
 bination of the gases with oxygen was impossible, and could 
 only take place when the temperature fell low enough. 
 
 In calculating the efficiency of the gas-engine from its dia- 
 gram, all previous observers had fallen into error, through 
 neglecting the effects of dissociation, and, accordingly, their re- 
 sults were much too high. To account for this so-called sus- 
 tained pressure, Otto advanced the theory that inflammation
 
 316 THE STEAM-ENGINE AND THE INDICATOR. 
 
 was not complete when the maximum pressure was attained at 
 the beginning of the stroke, but that by a peculiar arrangement 
 of strata he had made it gradual, and continued the spread of 
 the flame while the piston moved forward. Otto called this slow 
 combustion. This designation seemed erroneous to Clerk. 
 Such action should rather be called slow inflammation. It ex- 
 isted in the Otto engine, but only when it was working badly, 
 and was attended with great loss of heat and power. This was 
 proved by a diagram, and by certain considerations deduced 
 from Bunsen and Mallard's experiments on the rates of propa- 
 gation of flame through combustible mixtures. The conclusion 
 arrived at was that slow inflammation was to be avoided in the 
 gas-engine, and that every effort should be made to secure com- 
 plete inflammation at the beginning of the stroke. Clerk found 
 it possible to ignite a whole mass in any given time, between 
 the limits of one-tenth and one-hundredth part of a second, by 
 arranging the plan of ignition so that some mechanical disturb- 
 ance by the entering flame was permitted. A diagram taken 
 from the Otto and L,angen free-piston engine, as given in a 
 paper by Mr. F. W. Crossley, and an analysis of his reasoning, 
 showed that the results were misinterpreted, and false conclu- 
 sions arrived at concerning the nature of an explosion. Mr. 
 Crossley considered that an explosion of gas and air, pure and 
 simple, must be accompanied by a rapid rise and an almost in- 
 stantaneous fall of pressure. This, he thought, was proved by 
 the diagram, but in this statement the author could not concur. 
 From the considerations advanced in this paper, it would be 
 seen that the cause of the comparative efficiency of the modern 
 gas-engine over the old Lenoir and Hugon type may be summed 
 up in one word compression. Without compression before 
 ignition an engine could not be produced giving power econom- 
 ically and with small bulk. The mixture used might be 
 diluted, air might be introduced in front of gas and air, or an 
 elaborate system of stratification might be adopted, but without 
 compression no good effect would be produced. 
 
 Early Gas-Engines. 
 
 The early motors, in which work was attempted to be per- 
 formed by means of heat generated by the combustion of illum- 
 inating or similar gases, may be classed as follows:
 
 GAS-ENGINES. 
 
 317 
 
 The first motor, having a cylinder and piston, was introduced 
 in 1685, and was designed by Huyghens, in which powder was 
 exploded to generate the gas to drive it. Papin in 1688 also in- 
 vented a similar machine. The labors of these pioneers were 
 not crowned with success, and the gas-engine remained in this 
 embryo condition for more than a hundred years. In 1791, one 
 John Barber took out a patent in England for the production of 
 force through the combustion of hydrocarbons in air. 
 
 In 1794 Robert Street also patented a gas-engine, and in 1801 
 Franzose L,ebon, in which the ignition was produced by an 
 electric machine, also patented one. In 1823 Samuel Brown 
 invented one, and also in 1833 a Mr. Wright. This latter 
 machine showed substantial progress, compared with previous 
 efforts. It stood nearly on a level with modern constructions, 
 having a water-jacket, flame ignition, and was provided with a 
 centrifugal regulator, which regulated the air and gas supply in 
 proportion to the requirements of the work, so that the total 
 quantity of gas remained the same, and consequently the con- 
 dition of the mixture was unchanged. 
 
 Up to 1841 quite a number of gas-engine patents were issued 
 which are not worthy of mention, except one, specified by 
 Johnson in the above year. This patent pointed to the explo- 
 sive working effect of a mixture of oxygen and hydrogen, as 
 well as to utilizing the effect of the vacuum after the combustion. 
 
 To show how justly the value of gas-engines was recognized, 
 I quote a letter written in 1826 by Cheverton: "It has been the 
 wish for a long time of the practical mechanic to succeed in the 
 possession of a dynamic engine which is always ready for work 
 without costing too much to drive, and causing no loss of time 
 in preparation. These properties would make it in every case 
 applicable when only a small force is necessary at irregular 
 times; and the avoidance of manual labor is so important that 
 the advantages which society would derive from such a machine 
 would be incalcuable, even if the cost should be much greater 
 than with the employment of steam." 
 
 In 1855, Dr - Alfred Drake, of Philadelphia, succeeded in 
 constructing a gas -motor as before described, which was fol- 
 lowed in 1860 by the Lenoir gas motor, which caused unusual 
 attention, and justly so; for unscrupulous claims were every-
 
 318 THE STEAM-ENGINE AND THE INDICATOR. 
 
 where made for it. It is only just to state, however, that the 
 engines at the beginning worked tolerably well, as they were 
 carefully constructed and finished. Through these good pro- 
 perties many persons were led into giving orders without any 
 proof of the cost of working. These were so numerous that a 
 special company was formed the Lenoir Company to under- 
 take the construction. When these engines were put in place, 
 and the gas bills appeared, it was found by the users that instead 
 of a consumption of a half cubic meter (17.6583 cubic feet) of 
 gas per hour per horse-power, the Prony brake exhibited, with 
 unerring certainty, that three cubic meters (105.96 cubic feet) 
 at least were required on an average. Hugon, the director of 
 the Parisian gas works, and Reithmann, a watchmaker, of 
 Munich, hotly contested Lenoir's priority of invention. 
 
 FIG. 136. 
 
 Up to this time, independent of the large consumption of gas, 
 the great difficulty in the way of constructing a satisfactory 
 gas-engine has always arisen from the suddenness of the explo- 
 sion and expansion which has to be utilized, as shown in the ac- 
 companing diagrams taken from a Lenoir gas-engine about 1866. 
 
 FIG. 137. 
 
 The engine from which these diagrams were taken had a 
 cylinder 8.66-inch diameter, with a stroke of 16.25 inches, and 
 the explosion of the mixed air and gas was arranged to take 
 place at half stroke. Diagrams Figures, 136, 137 and 138 were
 
 GAS-ENGINES. 319 
 
 taken at a speed of 50 revolutions per minute. The explosion 
 did not take place immediately upon the closing of the valve, 
 and the pressure of the mixed air and gas within the cylinder 
 consequently fell, as the piston advanced, to n pounds above a 
 vacuum. When the explosion took place the pressure rose to 
 48 pounds, the time occupied by the explosion appearing to be 
 about ?\ of a second. 
 
 At the Paris International Exhibition of 1867, and at Phila- 
 delphia in 1876, Otto and Langen, of Deutz, exhibited their 
 atmospheric gas-engine. As the name implies, the explosive 
 effect of the gas in this engine was by no means employed 
 direct for the performance of work; it only served to throw up 
 
 FIG. 138. 
 
 the piston of the simple working cylinder, whilst it was out of 
 connection with the shaft of the engine. In order to procure a 
 place for the combustion products, the tension of the latter was 
 caused to fall very suddenly, in consequence of outside cooling, 
 and the vacuum succeeding allowed the piston to drop by its 
 own weight; and then, in connection with the shaft, the stroke 
 was not so sudden as that of Lenoir's. But it had many draw- 
 backs, which at one time were relatively great. It had many 
 complications in construction, which were calculated to cause 
 doubts as to its durability, and it also made a horrible noise, 
 much more unpleasant by reason of its irregularity. Notwith- 
 standing these drawbacks, the engine had great advantages, 
 which covered its defects. It used very little gas at the be- 
 ginning, 1.2 cubic meters, or 38.852 cubic feet, finally only 0.8 
 of a cubic meter (or 28.26 cubic feet per hour per horse-power), 
 a result which hitherto had not been exceeded. It was, there- 
 fore, practically useful for small industries. It could not only 
 compete with the steam-engine, but in many cases, beat it out 
 of the field.
 
 320 THE STEAM-ENGINE AND THE INDICATOR. 
 
 As before stated, in the Otto and Langen gas-engine the sud- 
 denness of the explosion and expansion which was to be util- 
 ized was surmounted very ingeniously by allowing the expansion 
 to take place under &free piston, whose velocity was not limited 
 by the motion of a crank, and engaging the piston-rod with the 
 driving shaft only on its downward stroke. In this way the 
 sudden expansion could, of course, be more completely utilized 
 than where the velocity was limited by the motion of a crank, 
 and engaging the piston-rod with the driving shaft only on 
 its downward stroke. Further, the sudden expansion could 
 be more completely utilized than where the velocity of the 
 piston was controlled by the usual connection to a crank-shaft. 
 The whole arrangement had, however, very distinct drawbacks, 
 and was obviously open to improvement. 
 
 In "Otto's" silent gas-engine the difficulty arising from the 
 suddenness of the explosion is removed in a totally different 
 way, namely: by making it less sudden. This could not be 
 done previously, because the mixture of air and gas was always 
 drawn into the cylinder at atmospheric pressure, and was al- 
 ready used as dilute as was possible under these conditions. If, 
 however, the mixture could be used tinder pressure, a much 
 larger dilution of air could be employed without destroying its 
 explosiveness, and in consequence, the violence and rapidity of 
 the explosion would be very much reduced. It is upon this 
 principle that the engines of to-day are constructed. The sud- 
 den explosion has been reduced to what is really not much 
 more than rapid combustion and expansion, but not too rapid 
 to be used without loss at the beginning of the stroke of an en- 
 gine arranged in the usual way. 
 
 These gas-engines in general external appearance resemble an 
 ordinary horizontal engine, but the resemblance is only super- 
 ficial. The cylinder is single-acting, open at the front end, and 
 so arranged that it only completes its cycle of operation once in 
 two complete double strokes. Its method of working is as fol- 
 lows: The piston in moving forward draws into the cylinder a 
 mixture of air and coal gas, the latter in measured quantity. 
 Returning, it compresses this mixture into little more than one- 
 third of its volume, as drawn in at atmospheric pressure. These 
 two operations require one complete double stroke. As the
 
 GAS-ENGINES. 
 
 321 
 
 piston is ready to commence the^ next stroke the compressed 
 mixture is ignited, and expanding, drives the piston before it, 
 while in the second return stroke the burnt gases are expelled 
 from the cylinder, and the whole made ready to start afresh. 
 Work is actually being done on the piston, therefore, only dur- 
 ing one-quarter of the time it is in motion, the gearing, as well 
 as the work driven, being carried forward by the fly-wheel dur- 
 ing the rest of the time. 
 
 The cylinder is enclosed in a water-jacket in order to prevent 
 overheating. To insure a circulation of water, it has been 
 
 FIG. 139. 
 
 found sufficient to simply connect the top and bottom of the 
 jacket with the top and bottom of a filled reservoir, the differ- 
 ence in the densities of the hot and cold water being enough to 
 set up and maintain the requisite circulation. The cylinder is 
 also cooled sufficiently by contact with the air in the reservoir 
 to be used continuously. To avoid shock at exhaust, the hot 
 gases are discharged through a pipe into a reservoir placed at a 
 little distance, from which they pass into the atmosphere. 
 
 Diagram Fig. 139 was taken from what is called a five-horse 
 engine, diameter of cylinder being 6 inches with a stroke of 
 12 inches, making 160 revolutions per minute; scale of indicator, 
 112 pounds equal one inch. 
 
 From diagram Fig. 140 it appears that the pressure comes 
 on very gradually, and that about one-tenth of a revolution is 
 required for the maximum pressure to be attained. Therefore, 
 there is not an explosion, but a gradual combustion. The 
 indicator diagram (Fig. 140), scale 112 pounds = one inch, is 
 21
 
 322 
 
 THE STEAM-ENGINE AND THE INDICATOR. 
 
 a fair sample of a card taken from a Otto gas-engine. Begin- 
 ning at A, the gas and air are entering the cylinder up to Z?, at 
 this point the inlet-valve closes, and on the return stroke the 
 gases begin to compress at h into the clearance space at the 
 back end of the cylinder. This compression is represented by 
 the line h /, and shows a pressure of about 45 pounds at i. 
 One revolution of the engine is now complete, and the charge 
 is ignited just as the crank is passing the center. The rapid 
 
 Fio. 140. 
 
 burning of the gas liberates a large amount of heat, increasing 
 the temperature and pressure, which latter reaches about one 
 hundred and fifty pounds per square inch as a maximum. The 
 line i, k, e, is called the explosion or rapid combustion line. 
 The gases now expand during the second forward stroke and 
 exert power upon the piston, which, by means of the fly-wheels, 
 carries the engine through the remainder of the revolution. At 
 g the exhaust valves open, allowing the burned gases to escape. 
 The line D to A shows the pressure, while these gases are being 
 expelled by the second return stroke of the piston. 
 
 When the governor prevents the admission of gas to the cyl- 
 inder, the cycle is somewhat modified. After compression of 
 the air no explosion can take place, since there is no combust- 
 ible mixture present The expansion line then follows closely 
 the previous compression line, and the cycle is completed by 
 expulsion of the air. Two revolutions are required to complete 
 the cycle when the engine takes gas at every charge; and four,
 
 GAS-ENGINES. 323 
 
 six, eight, and sometimes ten revolutions may occur before the 
 engine returns to its original state. 
 
 In fact, the new Otto motor is distinct from its predecessors, 
 by its very pleasing appearance, quiet, regular action, and har- 
 monious dimensions, and accordance with recognized principles 
 in three points, namely: 
 
 First In the compression of the gas mixture before ignition; 
 and, on account of its compactness. 
 
 Second Having a great piston velocity, the change of heat 
 into work is facilitated by prolonging the combustion. 
 
 Third By modifying the initial temperature, and by better 
 employment of the heat generated, in consequence of the cooling 
 of the cylinder. In fact, the Otto is one of the most efficient 
 constructions in the line of gas-engines, and is a striking ex- 
 ample of skill and of deep thought. 
 
 The cost of working. The consumption of gas stands only a 
 little higher than that of the atmospheric-engine; the smaller 
 powers use, on an average, 24 cubic feet per hour per horse- 
 power, while for the larger constructions the consumption of gas 
 is about 22 cubic feet. 
 
 Notwithstanding these engines are single-acting, they run 
 very regularly, particularly with a heavy load. Suction takes 
 place with pressure a little under 15 pounds, the compression 
 shows 45 pounds; through the explosion the pressure is sent up 
 to about 165 pounds, and falls gradually again in consequence 
 of the expansion to 45 pounds. Then the outlet valve opens at 
 about 10 per cent, of the piston-stroke before the end of the 
 stroke, when the pressure is about 15 pounds, remaining so to 
 the end. The gases escape at about 400 degrees. From the 
 diagrams it is conclusive that the highest temperature is 900 to 
 looo degrees. The indicated work represents about 18 per 
 cent, of the total heat of combustion of the gas. The useful 
 actual work is 14^ per cent. The best steam-engines utilize 
 only ten per cent, of the total heat of combustion of the coal, 
 and small engines scarcely exceed Jive per cent., so that it will 
 be seen that the gas-engine is by far the more perfect heat- 
 engine.
 
 324 THE STEAM-ENGINE AND THE INDICATOR. 
 
 The Clerk Gas-Engine. 
 
 This engine possesses the distinctive feature of making an 
 explosion at every revolution. The engine comprises two 
 cylinders the working, and the so-called "displacer" cylinder. 
 The pistons of the former are connected to the crank in the 
 ordinary manner, but the piston of the displacer cylinder, in 
 which the pressure is very slight, never exceeding 5 pounds to 
 the square inch, is driven by a pin in the arm of the fly-wheel. 
 The pin is at right angles to the crank and in advance of it. 
 When the piston in the displacer advances, a combustible 
 mixture of gas and air is drawn in during the first half of the 
 stroke; the admission valve is then closed, and air is admitted 
 during the remainder of the stroke. On the return of the pis- 
 ton a valve is opened, making a communication between the 
 two cylinders. At this time the piston of the driving cylinder 
 is at the outer end of its stroke, and an annular port is opened, 
 communicating with the exhaust pipe. Through this opening 
 the products of combustion from the last explosion pass, the 
 pressure in the cylinder falls, and the cylinder is ready to 
 receive its next charge from the displacer chamber. The first 
 portion that enters the cylinder from the displacer is the pure 
 air that passed in after its piston had reached the half stroke, 
 and the combustible mixture of gas and air had been cut off. 
 This flows through the motor cylinder, washing it out as it 
 were, at each stroke, and escaping through the exhaust until 
 the latter is closed by the piston starting on the return stroke. 
 Meanwhile, the explosive mixture has followed the pure air into 
 the motor cylinder, and remains, as the exhaust opening has 
 now been closed. The returning piston compresses this mixture 
 in a space at the end of the cylinder until it is about 45 pounds 
 pressure, when the charge is exploded. The pressure then 
 rises to, say 250 pounds per square inch, driving the piston for- 
 ward to the other end of the cylinder, when the exhaust is 
 again opened, and the exploded gases escape, leaving the cylin- 
 der free for the next charge from the displacer. This series of 
 operations takes place at every stroke. 
 
 It will be noticed that a particular feature of this engine is 
 the passing through the cylinder at each stroke a volume of
 
 GAS-ENGINES. 335 
 
 pure air, which cools it down and at the same time thoroughly 
 displaces all the residual gases from the previous stroke. To 
 produce this result the capacity of the displacer-chamber is 
 larger than that of the driving cylinder, and the space at the 
 end into which the explosive mixture is compressed; and as 
 half of each charge from the displacer is pure air, the desired 
 object of cleaning and cooling the cylinder at every stroke must 
 be attained. In large engines this device should be of the 
 greatest possible service, as it should effectually prevent prema- 
 ture firing of the explosive charge, which would otherwise 
 sometimes occur through the existence of sparks from the ig- 
 nition of particles of carbon on the sides of the cylinder. The 
 volume of air which sweeps through the cylinder at each stroke 
 in the Clerk engine cools it down so as to prevent the existence 
 of sparks, or if they should be created, removes them as it 
 passes rapidly to the exhaust. The valve-gear and cut-off ar- 
 rangement are very simple. The mixed charge of gas and air 
 is admitted into the displacing chamber by an automatic lifting 
 valve, and another similar valve makes a communication be- 
 tween the displacer and the driving cylinder. This is actuated 
 by the pressure of the air and gas in the displacer, but this 
 pressure is very low, all that is required being sufficient to raise 
 the valve and help to displace the residual gases left by the 
 previous explosion in the motor cylinder. The ignition of the 
 mixture at each stroke is effected by a small slide at the back 
 of the engine, worked by an eccentric on the main shaft, and 
 the same slide cuts off the supply of gas to the displacing cylin- 
 der at half stroke. The igniting device is very perfect, and as 
 it is required to operate more frequently than in gas-engines, 
 where explosions take place every second revolution, it also 
 forms a novelty in detail. In the ignition slide is a cavity, from 
 each end of which is a small port leading to opposite ends of the 
 slide. At one end of the cavity is a perforated plate, through 
 which the explosive mixture passes from the motor cylinder, 
 communication being made by a small hole in the slide and a 
 groove in the face of the slide, which is always in a passage in 
 the engine face leading to the combustion chamber at the end 
 of the motor cylinder. After passing through this perforated 
 plate, the mixture is lighted by a Bunsen burner, the flame fill-
 
 336 
 
 THE STEAM-ENGINE AND THE INDICATOR. 
 
 ing the cavity and discharging at the port in the face of the slide. 
 The movement of this latter opens this port into a port on the 
 side of the combustion chamber, causing ignition at each stroke. 
 So efficient is this arrangement that it will operate successfully 
 at a speed of 300 explosions a minute, a far higher rate than 
 can be obtained, or is indeed required, by the ordinary gas- 
 engines. Before the ignition slide is open to the combustion 
 chamber, it is of course closed to the atmosphere. The ignition 
 port is very small, 0.5 inch by 0.25 inch, so that a very moder- 
 ate pressure keeps the slide to its face, even against the 250 
 pounds per square inch caused by the explosion. The slide be- 
 ing so small, there is no necessity for ventilating the port, as the 
 mixture from the cylinder requires no exterior air to support its 
 
 FIG. 141. 
 
 250 
 
 combustion. It may be mentioned that the admission valve to 
 the displacer chamber, and that between this latter and the 
 driving cylinder, are prevented from rattling by a very simple 
 arrangement of air cushion. 
 
 It will be seen by the indicator diagram, Fig. 141, that in this 
 engine the expansion is only continued until the volume of the 
 hot gases becomes equal to the volume before compression. 
 
 Diagram, Fig. 142 was taken from a 12 horse-power engine 
 running with full load. Diameter of cylinder, 9 inches; length 
 of stroke, 20 inches; revolutions, 132 per minute; mean pressure, 
 66.1 pounds per square inch; maximum pressure, 177 + 55 
 232 pounds; pressure before ignition, 55 pounds; indicated 
 horse-power, 28.01; consumption of gas per indicated horse-
 
 GAS-ENGINES. 
 
 327 
 
 power, 23.21 cubic feet; consumption of gas per brake horse- 
 power, 24.12 cubic feet. 
 
 Fig. 143 is from Clerk's gas-engine; diameter of motor-cylin- 
 der, 6 inches; stroke, 12 inches; and rated by the makers as 6 
 horse-power. The indicated horse-power is 9.15, while the 
 effective power given out on the brake was 6.56 horse-power; 
 
 FIG. 142. 
 
 225 
 
 71.2 
 
 42 Lbe. 
 
 the consumption of gas being at the rate of 21.8 cubic feet per 
 indicated horse-power, or 30.2 cubic feet per hour per brake 
 horse-power. It will be seen from the diagram that a very 
 rapid ignition is obtained, in fact, the inventor endeavors to 
 make this ignition as rapid as possible. 
 
 FIG. 143. 
 
 177 Lbe, 
 
 55 Lbs. 
 
 The "Stoekport" Gas-Engine. 
 
 This gas-engine was exhibited for the first time in this coun- 
 try at the Novelties Exhibition, Philadelphia, and attracted 
 considerable attention. As it possesses very many points of 
 interest, a short description may prove of interest. 
 
 The Stockport gas-engine is of the type (3) of those which
 
 328 THE STEAM-ENGINE AND THE INDICATOR. 
 
 compress the charge, and have an explosion at every revolution, 
 whether the engine be lightly or heavily loaded. It consists of 
 two cylinders, arranged on the same axial line; one draws in 
 the combustible mixture of gas and air, the other acts as the 
 working cylinder in which the charge is exploded to produce 
 power. The pistons of these two cylinders are connected by a 
 trunk, so that they are in rigid union, moving simultaneously 
 in the same direction. The central part of this trunk, in the 
 free space between the two cylinders, is partly cut away, so 
 that for a portion of its length it is no longer cylindrical, but 
 rather less than half a cylinder. This is for the purpose of 
 accommodating the connecting rod, which is pivoted at one end 
 in the center of the trunk, and at the other end to the crank-pin, 
 which works in the reduced portion of the trunk. The whole 
 arrangement is similar to some form of steam pumps, with the 
 crank-shaft midway between the steam and water cylinder. 
 
 This engine differs from the Otto, from the fact that there is 
 an explosion at every revolution. The operation is simple and 
 is easy to follow. Commencing with the explosion, the work- 
 ing piston is driven forward by the force of the expanding gases, 
 which follow it almost to the termination of its stroke. Just 
 before it reaches the end, however, it passes an open exhaust 
 port, communicating through a pipe with the outer air. At 
 this point the gases have, in the normal conditions of working, 
 a pressure of about 30 pounds per square inch, and they in- 
 stantly discharge themselves until the cylinder and combustion 
 chamber are filled only with products of combustion at atmos- 
 pheric pressure. At this moment the slide-valve opens com- 
 munication between the cylinder and a reservoir filled with 
 combustible mixture under moderate pressure. This sweeps 
 out whatever remains of the exploded charge, driving it be- 
 fore it without sensibily mixing with it, and completely filling 
 the cylinder before the piston (which has now commenced its 
 return stroke) covers the port. All this occupies but a very 
 slight portion of the piston-stroke, but as it travels very slowly 
 for a considerable angle of the crank on each side of the center, 
 there is ample time for the evacuation of the spent charge and 
 the introduction of the new one. The piston now moves in 
 wards, driven by the work stored in the fly-wheel, and com-
 
 GAS-ENGINES. 329 
 
 presses the mixture in the combustion chamber at the end of 
 the cylinder until the crank again passes the center, when the 
 ignition port is opened, and the revolution is complete. 
 
 Commencing now with the supply cylinder, also at the 
 moment when the explosion occurs, we find the cylinder filled 
 with an intimate mixture of gas and air. These two fluids are 
 intentionally blended as completely as possible, stratification, or 
 the introduction of air cushions, being purposely avoided, as 
 the thorough ventilation of the working cylinder at each revo- 
 lution keeps the temperature of the metal and the residual gases 
 below the point at which they will ignite the incoming charge. 
 As the piston moves backward it forces the mixture into a 
 reservoir in the bedplate of the engine, where it is momentarily 
 retained, and then, on its outward stroke, it draws in a fresh 
 supply. Thus it will be seen that when the working piston is 
 driven by an explosion, the supply piston forces a charge into 
 the reservoir ready to sweep out the products of combustion, and 
 to take its place ready for compression; and when the working 
 piston is compressing this charge, the supply cylinder is being 
 filled afresh. 
 
 As there is an explosion at every revolution, it follows that 
 the strength of the charge must be varied to suit the load on the 
 engine. This is done by a governor which controls a small 
 equilibrium valve in the gas passage, raising and lowering it as 
 the speed increases and decreases. There is, however, a limit 
 beyond which this method of regulation cannot be carried, for 
 if the mixture be made too dilute it will not ignite. If an 
 engine were running absolutely empty it might easily happen 
 that the lowest ignitible mixture would provide too much 
 power, and the result would be an excess of speed. To prevent 
 this the governor, besides controlling the throttle valve, de- 
 termines the position of a stud on a lever connected with a valve 
 on the cylinder. At a given speed the stud is moved into the 
 path of a tappet, and opens the valve when the compression is 
 taking place in the working cylinder. The result of this is that 
 a part of the charge is driven out of the cylinder through a pipe 
 which ends in the air inlet pipe to the supply cylinder, from 
 which the rejected charge is drawn at the next stroke and 
 delivered again to the reservoir.
 
 330 THE STEAM-ENGINE AND THE INDICATOR. 
 
 Besides the above mentioned tappet valve, which is usually 
 out of action, there are only two valves in the engine, both ol 
 them slide valves, and both operated from the same eccentric. 
 The working cylinder valve is driven direct, as in a steam- 
 engine. The supply cylinder valve is worked by an arm at the 
 end of a small weighted shaft, the. other end of which carries a 
 slotted lever gearing with a pin projecting from the strap of the 
 eccentric. This pin follows a curved path, moving backwards 
 and forwards in the slot, the result being that the angular 
 velocity of the lever, and consequently the speed of travel of the 
 valve, varies very greatly at different parts of the stroke. The 
 valve of the supply cylinder is a flat plate working between the 
 face on the cylinder and a back plate, in which there is a cavity 
 in constant communication with the gas pipe after it has passed 
 the throttle valve. There are three ports in the cylinder face, 
 one opening into the air, one to the cylinder, and one to the 
 reservoir, and there is a cavity in the face of the valve with a 
 number of small passages leading from it to meet the cavity in 
 the back -plate. During the indrawing stroke the gas enters the 
 valve in fine streams, and the air sweeps across it at right 
 angles as it is drawn to the inlet port of the cylinder. At the 
 end of the stroke the movement of the valve cuts off the gas and 
 air, and puts the cylinder port in communication with the pipe 
 leading to the reservoir. The whole arrangement is exceed- 
 ingly simple, and resembles the valve of a single acting steam 
 engine. 
 
 The valve of the working cylinder is likewise a flat plate- 
 valve. It slides on the side of the cylinder, not the end, in the 
 same way as the valve of a steam-engine. Its function is to put 
 the cylinder in communication with the reservoir when the 
 piston passes the exhaust-port, and to break the communication 
 when the piston again closes the port. In addition to this very 
 simple operation, it has to effect the ignition of the charge. The 
 master-light burns in a recess or chimney formed in the end of 
 the cylinder, or more correctly, in the combustion chamber. It 
 has an opening through the valve face, and past this opening 
 there travels a cavity in the valve. This is supplied by gas, 
 which becomes ignited, and in this condition is carried to the 
 main port of the cylinder, the whole width of the cavity being
 
 GAS-ENGINES. 
 
 331 
 
 presented to the port at once, insuring the certainty of an ex- 
 plosion. The valve is cored out for the circulation of water, 
 which enters and leaves through flexible connections. By this 
 means its temperature is kept at a point where there is little fear 
 of seizing or cutting. It is held up to its place by a back-plate 
 with springs under the nuts which secure it, and is further re- 
 tained by clamps on the studs. These give way as the valve 
 expands, and allow it to obtain just the amount of room which 
 it requires. 
 
 The gas consumption of these engines is 35 cubic feet per 
 actual horse-power per hour, or 20 cubic feet per indicated 
 horse-power per hour, when running at their full capacity. The 
 average pressure in the cylinder is about 74 pounds per square 
 inch, the initial and terminal pressures being 210 pounds and 
 30 pounds. The motion is regular, since there is an explosion 
 at each revolution, whether the load be light or heavy, and any 
 sudden increase of work cannot stop the engine. 
 
 Its regularity will commend it to those who require steady 
 power, while its general simplicity and its compact design will 
 attract users who do not understand complicated machinery. 
 
 The Atkinson Gas-Engine. 
 
 Diagrams Figs. 144, 145 and 146 were taken from a six horse- 
 power Atkinson u cycle" gas-engine combined with a pump. 
 By means of the link work the piston has imparted to it four 
 strokes for each revolution of the crank shaft. These strokes 
 all vary in length, being as follows: 
 
 Suction stroke 6^5 inches. 
 
 Compression stroke 5 inches. 
 
 Working stroke UTS inches. 
 
 Exhaust stroke 12! inches. 
 
 The cycle commences, say at the end of the exhaust stroke, 
 the piston at this time being as close to the end of the cylinder 
 as is compatible with safety, thus driving out practically all the 
 residuum, which is still further cleared out by the momentum 
 of the exhaust gases in the exhaust pipe dragging a little air 
 through the passages and small clearance space left. From an 
 economical point of view it is now pretty well understood that 
 the total elimination of the burnt gases is a desirable feature;
 
 332 THE STEAM-ENGINE AND THE INDICATOR. 
 
 in fact, engines have recently been made which sacrifice an 
 entire revolution for the purpose of obtaining this desirable 
 object. 
 
 A short suction stroke is now made, followed by a slightly 
 shorter compression stroke, the difference in the lengths of these 
 strokes leaving a chamber into which, together with the clear- 
 ance spaces, the charge is compressed. At this time ignition 
 takes place and a long working stroke is made, followed by a 
 slightly longer exhausting stroke, when we arrive at the com- 
 pletion of the cycle, the whole being performed during one 
 revolution of the crank shaft. 
 
 The arrangement of this engine is very simple of construction 
 and very economical in running. There are only three valves 
 in the engine: the exhaust- valve, which is similar to that 
 commonly used in most gas-engines, the suction valve, which 
 is practically a duplicate of the exhaust valve, and the gas gov- 
 ernor valve, which is also similar to those commonly used for 
 the same purpose. The exhaust valve is opened by a cam on 
 the main shaft, the cam rod working a lever which opens the 
 valve. The suction valve is operated in a similar manner. 
 Both these valves open inwards, so that any pressure in the cyl- 
 inder tends to keep them closed. They are also closed by one 
 spring which is arranged between them operating through a 
 yoke which presses against the ends of bridles on each of them. 
 The gas governor valve is opened by the suction valve cam 
 whenever the governor permits of its being so opened. The 
 ignition is caused by the compression forcing a portion of the 
 charge into a small tube which is closed at the outer end and 
 kept red-hot by means of an external " Bunsen " burner. There 
 is no valve in connection with this ignition arrangement, the 
 timing of the ignition being caused by the chimney being raised 
 or lowered. As the charge is always uniform throughout its 
 volume, this gives a sufficiently regular ignition for practical 
 purposes, and doing without a valve in this position gets rid of 
 what has hitherto been the greatest source of trouble with gas- 
 engines. We are informed that several of these engines have 
 worked for six months ten hours every day without a valve be- 
 ing removed for cleaning, without the piston being taken out, 
 and without a single bearing being adjusted. This seems com-
 
 GAS-ENGINES. 333 
 
 ing within measurable distance of the simplicity and certainty 
 of a steam-engine. t ' 
 
 The great economy of these engines is obtained mainly from 
 two causes. In the first place, it will be seen that unlike any 
 other gas-engine, the expansion of the ignited charge does not 
 end when it has reached the original volume of the charge, but 
 is continued to any desired extent, generally about twice the 
 original volume. This continued expansion adds about a third 
 more work for the same consumption of gas; its value is very 
 much increased from the second main source of economy, which 
 is the rapidity with which the expansion takes place. Other 
 gas-engines expand to original volume during one-half of a 
 revolution, this one expands to original volume during one- 
 eighth of a revolution, so that work is done four times as fast. 
 When it is understood that one of the greatest sources of loss is 
 the passage of heat through the walls of the cylinder to the 
 water jacket, it will be seen how necessary it is to do the work 
 rapidly. From this cause the expansion line of the diagram, 
 when the expansion has taken place as far as original volume, 
 will be found to be from five to ten pounds higher (it is gener- 
 ally about forty-five pounds); this leaves a considerable pressure 
 with which to continue the expansion. The terminal pressure 
 is generally about fourteen pounds, which gives a quiet exhaust 
 and a better opportunity for the gas to be thoroughly consumed 
 during the working stroke. 
 
 In all gas-engines there is a heavy initial pressure which in 
 every other instance is transmitted to the crank-pin and main 
 bearing. Here, however, this heavy pressure is transmitted 
 directly to the long bearing of the vibrating link. This bear- 
 ing is made the whole width of the engine, is lined with white 
 metal, and thus takes this heavy shock without any straining 
 and with very little friction or wear. 
 
 Taking an ordinary diagram from one of these engines, the 
 pressure on the crank-pin and main bearings never exceeds 
 about thirty-five per cent, of the maximum pressure on the 
 piston. The work done in the cylinder during the early part 
 of the expansion is also transmitted more gradually to the 
 crank-pin, so there is not the jerkiness in running so commonly 
 associated with gas-engines; combining this with the ignition at
 
 334 
 
 THE STEAM-ENGINE AND THE INDICATOR. 
 
 every revolution controlled by a wonderfully sensitive governor, 
 the running of these engines is remarkably steady and regular. 
 The makers assert that when everything is in first-rate order 
 they will not vary more than from one to two per cent, between 
 maximum and minimum loads, and- that it is perfectly im- 
 material how suddenly changes in the working load are made. 
 
 Governor cutting out 20 per cent, of ignitions. 
 
 Stroke Suction 6 T \ inches. 
 
 Stroke Compression 5 inches. 
 
 Stroke Working II T \ inches. 
 
 Stroke Exhaust I2f inches. 
 
 The pressures being as follows: 
 
 50 + 78 -f 58 4- 45 +35 4- 28 4- 24 4- 1 8 + 14 + 8 = 358. 
 
 358 
 Mean average pressure = ~^~ 35-8 pounds. 
 
 A trial was made for five hours of a six horse-power nominal 
 Atkinson patent "Cycle" gas-engine working a double-acting
 
 GAS-ENGINES. 
 
 335 
 
 pump direct, the engine being driven by "Dowson" gas. The 
 pump being four inches in diameter, and the stroke can be 
 adjusted from eight to twelve inches. The water was taken 
 from a reservoir under the engine-room floor, and delivered 
 through a six-inch rising main into a storage reservoir 2043 feet 
 distant, and elevated 171 feet high, revolutions of engine 120 
 
 per minute. 
 
 FIG. 145. 
 
 Pump 4 inches diameter. 
 
 Stroke adjusted to 8 A inches. 
 
 Revolutions 120 per minute. 
 
 Diagram from bottom of pump. 
 
 Diagram Fig. 145 was taken from the pump, from which it 
 will be seen that its full capacity was delivered. Diagram 
 Fig. 144 was taken at the same time from the engine, the gas 
 consumption being also taken by observing how long it took 
 for a gas-holder six feet in diameter to fall four feet. The 
 engine diagram is by no means as full as can be taken with 
 "Dowson" gas, but as the engine was only taking ninety-six 
 ignitions per minute the gas was reduced so as to give diagram 
 Fig. 144.
 
 336 THE STEAM-ENGINE AND THE INDICATOR. 
 
 The following is the result of this trial: 
 
 Indicated horse-power in engine, 6.951 
 
 Indicated horse-power in pump, . . . 4-538 
 
 Actual horse-power in water lifted 4.5 
 
 Dowson gas per hour in cubic feet, 54 2 - 
 
 Equivalent in coal, coal consumption in pounds 7.74 
 
 Dowson gas per indicated horse-power in engine in cubic feet, . 78.0 
 
 Equivalent coal consumption in pounds, i.n 
 
 Dowson gas per actual horse-power in water lifted in cubic 
 
 feet, 120.0 
 
 Equivalent coal consumption in pounds, 1.706 
 
 Combined efficiency of engine and pump, . . .63.46 
 
 When it is understood that this plant was only started for a 
 couple of hours the previous day, the above figures are aston- 
 ishing, and as the makers state that rapid improvements will 
 take place in the working of the engine and pump, they assert 
 that it is the most economical pumping plant ever erected, and 
 though slightly better figures have been obtained from first-class 
 compound condensing engines of large size, we feel inclined to 
 agree with them, as the saving in first cost of machinery and 
 buildings must also be very great. 
 
 Although the pump was running at 120 revolutions per min- 
 ute, the valves closed without the slightest shock. They are 
 very large diameter, are guided top and bottom, and have strong 
 springs fitted to them. The loss by friction in valves and rising 
 main was only 0.038 of a horse-power, so it is evident that the 
 pump must have worked in a very satisfactory manner. We 
 doubt also whether it would be possible to attain such a high 
 efficiency by using any system of geared pumps. It is needless 
 to state that a plant of this description can be erected for very 
 much less outlay than if geared pumps had been used: not only 
 would the engine and pumps have cost more, but also the found- 
 ations and buildings; the cost for maintenance would also be 
 very much increased. 
 
 To enable the engine to be started without the load of the 
 pump, there is a bye pass from the delivery to the suction: a 
 reflux valve in the delivery valve just beyond keeps the delivery 
 main charged.
 
 GAS-ENGINES. 337 
 
 There are no doubt numerous instances in which a plant 
 which is so economical in first cost and working, could be 
 adopted with advantage where the cost of enormous engines, 
 geared pumps, and high buildings, have been prohibitory. 
 
 105 Ibs 
 
 FIG. 146. 
 
 456 
 
 10 
 
 30 D 
 V 
 
 Coal gas. Speed 130 revolutions per minute. 
 
 Total pressure P = 195 pounds. 
 
 Total compression, 57 pounds. 
 
 Total terminal pressure, 30 pounds. 
 
 A six hours' continuous brake trial was made of the Atkinson 
 gas-engine, brake loaded for 9.5 horse-power, revolutions 130 
 per minute. Indicator diagrams were taken every quarter of an 
 hour, a,nd worked out with the number of revolutions made in 
 that interval as read on the counter. The two meters were 
 read every quarter of an hour, and the gas pressure and tem- 
 perature noted at the same time. The water meter was also 
 read every quarter of an hour. The spring balances on the 
 brakes were read every five minutes. The work taken up by- 
 each of the two fly-wheels was kept as nearly equal as possible. 
 The rope brakes were worked perfectly dry, without any lubri- 
 cant whatever. 
 
 The mean speed of the engine was 131.1 revolutions per 
 
 22 

 
 338 THE STEAM-ENGINE AND THE INDICATOR. 
 
 minute. The maximum speed for any quarter-hour was 132.7 
 revolutions per minute, minimum for any similar period 129.2 
 revolutions per minute. The number of explosions per minute 
 was 1 2 1. 6, so that 7.2 per cent, of the explosions were cut off 
 by the governor. 
 
 The mean initial pressure was 166 pounds per square inch 
 above the atmosphere, but the mean effective pressure, owing 
 to the great ratio of expansion employed, was only 46.1, the 
 indicated horse-power was thus n. 15. This power is calculated 
 from the revolutions per quarter-hour after deducting the actual 
 number of misses during that time. A record of the actual 
 misses was kept throughout the whole of this and all other 
 trials, by two observers, who relieved one another at hourly (or 
 shorter) intervals. 
 
 The brake horse-power was 9.48, so the mechanical efficiency 
 of the engine reached 85 per cent. The horse-power expended 
 in driving the engine (difference between indicated horse-power 
 and brake horse-power) was 1.67. 
 
 The gas per hour through the main meter was 209.8 cubic 
 feet, which is at the rate of 18.8 cubic feet per indicated horse- 
 power per hour, and 22. i per brake horse-power per hour. The 
 additions of the gas used for ignition, 4.5 cubic feet per hour, 
 raises these figures to 19.2 and 22.6 cubic feet respectively. 
 
 Diagrams were taken with a light indicator spring to enable 
 some estimate to be made of the power expended by the engine 
 in what have been called the "pumping strokes." The work 
 done during the pumping strokes was equivalent to a mean 
 pressure during the working stroke of about one pound per 
 square inch, and this corresponds to an indicated horse-power 
 of o. 26. 
 
 The calorific value of gas used per explosion was: 
 
 0.000896 X 19200 X 772 = 13,280 foot pounds per explosion. 
 
 The following Table No. 7 gives the actual percentages of 
 heat actually turned into work, etc., the heat per explosion 
 being taken as above at 13,280 foot-pounds: f 
 
 The actual expenditure of heat was at the rate of 11.250 units 
 of heat per indicated horse-power per hour, which corresponds 
 to the absolute efficiency of 22.8 per cent, above given.
 
 GAS-ENGINES. 339 
 
 The efficiency of this engine, as compared with a perfect en- 
 gine working between the same limits of temperature, and re 
 ceiving the same amount of heat, is 28.2 per cent. 
 
 It has been found, by observation extending over a period of 
 five years, that the average cost of a gas-engine is $60.00 per 
 annum per horse-power, whilst a steam-engine costs about $50.00. 
 
 TABLE 7. 
 
 Items. 
 
 per cent. 
 
 Heat turned into work as shown by indicator diagrams 
 
 22.8 
 
 Heat rejected in exhaust, lost by imperfect combustion, and other- 
 wise unaccounted for 
 
 SO 2 
 
 
 100.0 
 
 The "Forward" Gas-Engine. 
 
 The latest and one of the best gas-engines in the market is 
 the ''Forward:" its mechanical simplicity is a great recommend- 
 ation. 
 
 The distinguishing feature of the Forward is a rotating valve 
 by which the ignition of the combustible charge in the cylinder 
 is effected. In this valve there are eight ignition ports which 
 come into action successively. Each port after having fulfilled 
 its office has to make a revolution through an entire circle before 
 it comes into action again, and in the mean time it is exposed 
 to the air, by which the greater part of the heat which it has 
 absorbed is carried away. It thus follows that the valve al- 
 ways works cool, and runs scarcely any risk of cutting, while 
 the constant motion in one direction affords another element of 
 safety. Every time the cylinder takes in a charge the valve 
 gives a partial revolution, but when the gas is cut off completely 
 the valve ceases to move, and the small firing charge which 
 would otherwise be wasted is saved. The number of missed 
 explosions is not, however, great in this engine, as the strength 
 of the charge is reduced as the work falls off until it approaches 
 the point at which it would cease to explode; the gas is then 
 cut off entirely, and the valve left stationary until the governor 
 arm again falls.
 
 340 THE STEAM-ENGINE AND THE INDICATOR. 
 
 A trial of this engine was had at full working load, at half 
 load, and unloaded, the latter test being divided into three parts, 
 at fast, medium and slow speeds. The full working load trial 
 lasted 85 minutes, the speed being 176.86 revolutions per minute. 
 The indicated horse-power was 5.54, and the brake horse-power 
 4.807, giving a mechanical efficiency of 0.8677. The gas con- 
 sumed in driving the engine was 163.2 feet, or 20.79 cubic feet 
 per hour per indicated horse-power, and 23.97 f e t P er brake 
 horse-power. At half power the brake horse-power was 3.084, 
 equal to a gas consumption of 31.86 feet per hour per horse- 
 power. The lighting jet burned about two feet per hour. 
 When the engine was running empty it burned 53 feet of gas 
 per hour at the high speed, 44 feet at the medium speed, and 
 34 feet at low speed. 
 
 Self-starting Gas-Engine. 
 
 The usual method of starting a gas-engine by pulling it 
 around until a charge of gas and air had been compressed and ex- 
 ploded was quite practical when confined to small sizes; but 
 now that gas-engines are so much larger, it is a matter of con- 
 siderable difficulty to start them. Mr. Clerk has devised an 
 arrangement whereby his engine may be started like an or- 
 dinary steam-engine. By means of a valve in the pipe between 
 the displacer cylinder and the working cylinder, the compressed 
 inflammable mixture, instead of entering the latter cylinder, 
 can be directed into a receiver, where it is stored at a pressure 
 of 70 pounds per square inch, the engine running meanwhile 
 by the stored work in the fly-wheel. As the valve is easily 
 manipulated, the charge is delivered alternately to the engine 
 and the receiver, two or three minutes sufficing to raise the 
 pressure to the required amount. To start the engine the crank 
 is left just over the center, as in a steam-engine, in which posi- 
 tion the crank of the displacer cylinder is almost vertical, and 
 then the compressed mixture is admitted from the receiver into 
 the displacer, where, acting upon its piston, it starts the engine. 
 At the same time the valve between the displacer cylinder and 
 the main cylinder is raised, and the pressure acts on the main 
 piston through its outward stroke. On the back stroke the 
 charge is compressed, part of it escaping through a valve opened
 
 GAS-ENGINES. 341 
 
 for the purpose; at the end of the instroke the inflammable 
 mixture is ignited and the engine is fairly started. The com- 
 munication with the reservoir is then cut off, and the displacer 
 cylinder resumes its usual functions. An engine may be stopped 
 and started many times in succession by one charging of the 
 receiver, and each time without any difficulty; the operation, 
 when the crank is in the right position, being within the 
 capacity of a boy. It has often been proposed to make a self- 
 starting gas-engine, and there are many patents for the purpose, 
 but this is the first time it has come into practical use. 
 
 Otto's Twin-Cylinder Gas-Engine. 
 
 The new twin-cylinder gas-engines are fitted with their self- 
 starting arrangement. These engines are so arranged that when 
 running full power an impulse is given every revolution, instead 
 of every alternate revolution as in the ordinary Otto engine. 
 The two cylinders are placed side by side, and their pistons are 
 coupled to the same crank, so that they move together, while a 
 single valve passes across their back ends and affects the gas 
 and air distribution of both. The ignition arrangements are both 
 such that when the engine is running at its full power the ex- 
 plosion takes place in the two cylinders alternately, one cylin- 
 der taking in a charge while an explosion occurs in the other. 
 As the power required is reduced, the governor first reduces the 
 number of explosions made per minute in one cylinder, eventu- 
 ally shutting off the gas supply from that cylinder altogether, 
 and then reduces the number of explosions in the second cylin- 
 der, so that at very low powers the engine is driven by explosions 
 in one cylinder only. 
 
 The self-starting arrangement consists of a strong cylindrical 
 chamber, or accumulator, placed by the side of the engine, 
 communicating with the adjacent cylinder by a connecting 
 pipe and loaded valve. The arrangement is such that at each 
 explosion, as soon as a certain pressure is reached, a small quan- 
 tity of the gaseous products passes over into the accumulator. 
 This goes on until the pressure in the accumulator reaches that 
 attained in the cylinder. When the engine has to be started, 
 the gases under pressure stored in the accumulator are admitted 
 to the cylinders by a hand-moved valve, and act on the pistons
 
 342 THE STEAM-ENGINE AND THE INDICATOR. 
 
 just as steam or compressed air would. It is only necessarj' to 
 give a single impulse in this way to start the engine. We may 
 mention that the valve through which the gases pass to the ac- 
 cumulator is fitted with an arrangement of oil-trap, which rend- 
 ers it necessary that it should only be oil-tight and not gas-tight. 
 This, of course, greatly facilitates the retention of the pressure 
 in the accumulator for long periods. The accumulator has suf- 
 ficient storage to enable the engine to be started a dozen times, 
 or even more, with one charge, if care be taken in the manipu- 
 lation of the admission valve. 
 
 Spiel's Petroleum-Engine. 
 
 This petroleum-engine was invented by Johannes Spiel, of 
 Berlin, Germany. It is a very neat and successful form, and in 
 general appearance very much resembles the well-known Otto 
 motor, the points of difference relating mainly to the devices by 
 which the motive fluid is measured and delivered to the cylin- 
 der, in admixture with the proper proportions of air. The 
 operation is as follows: 
 
 The piston on its outstroke draws in a charge of air and 
 petroleum; it then returns, compressing this mixture, which is 
 exploded as the crank passes the back center. On the next 
 stroke the combustion and expansion of the charge occurs, 
 while the fourth and last stroke drives out the products of com- 
 bustion. There is thus one working stroke in every four, the 
 motion being continued through the other three by the work 
 stored in the fly-wheel. 
 
 The source of power is petroleum spirit, otherwise known as 
 benzoline, or naphtha. This has a specific gravity of 0.7 or 
 0.71, and a very low flashing point, so that it will not pass the 
 fire test; consequently it cannot be stored and used without 
 special precautions. If the proper conditions are observed, the 
 use of this spirit does not involve any extraordinary risk, for it 
 is employed in large quantities in the dry cleaning process, and 
 also in the manufacture of india rubber. When used with this 
 engine it is stored in a closed receptacle connected by a pipe to 
 the reservoir attached to the cylinder of the engine. From this 
 reservoir a pipe runs to the pump, by which measured quanti- 
 ties are injected to the cylinder. At the bottom of the pump
 
 GAS-ENGINES. 343 
 
 there is, in place of a foot- valve, a plug worked by a link from 
 a tappet, as will be presently explained. During the induction 
 stroke of the piston, the cock is turned so as to force the liquid 
 in the pump into the space above the inlet valve, whilst at the 
 same time the admission of liquid through the pipe from the 
 reservoir is cut off. During the remaining strokes the cock cuts 
 off the communication with the valve, whilst the pump is again 
 in communication with the reservoir. The petroleum does not 
 pass through the plug, but along a channel cut round it. The 
 passage of the oil, or spirit, from the pump to the cylinder is 
 past the valve, and through the pipe leading into the cylinder. 
 This enters by a pipe, and in passing the valve it drives forward 
 the spirit, breaking it into spray, and carrying it into the cylin- 
 der in admixture with itself. The curved gutter formed round 
 the mouth of the pipe (entering the cylinder) serves to arrest 
 any liquid that may be imperfectly mixed, and as the explosive 
 mixture flows over it, and beneath the valve, the gutter tends to 
 direct the current upwards, so as to break up and still further 
 mix the air with the liquid. The valve, the pump, and plug, 
 are operated by a cam on a shaft running parallel with the cyl- 
 inder, which is driven by bevel gear, and revolves at half the 
 speed of the crank-shaft. A crosshead is connected to a rock- 
 ing beam, which at its other extremity carries a rod ending in 
 a roller, which runs in contact with a cam, and is raised at the 
 appropriate times. A spring draws down the roller when the 
 projection on the cam has passed. Another portion of the cam 
 opens the exhaust valve. The firing valve consists of a plate 
 operated by a tappet on the end of the parallel shaft. The 
 valve spindle is prolonged and provided with a spring by which 
 the valve is shot back when the tappet ceases to act on the 
 friction bowl. The force of the recoil is moderated by the 
 spring stops which run between the rollers, and must be com- 
 pressed as the valve nears the end of its stroke. 
 
 The firing light is the flame of a lamp which is kept con- 
 stantly burning. At a suitable moment it ignites the burner in 
 the valve, and by the quick return movement a flash is trans- 
 ported to the firing apparatus in the cylinder. The combustible 
 mixture finds its way into the burner during the compression 
 stroke. In front and surrounding the burner is a chamber
 
 344 TH E STEAM-ENGINE AND THE INDICATOR. 
 
 which serves to convey a flame from the outer jet to the charge 
 in the cylinder. The chamber forms an annular space round 
 the burner, and a passage opens into this space, and maintains 
 a communication for the supply of the combustible gas or vapor 
 during the times when the main passage is closed. The gas 
 passing through flows round the burner, and thus becomes 
 heated and ignites more readily. When the chamber is filled 
 with gas the valve is moved by a ram until the burner is oppo- 
 site the port in the cover. The gas is then ignited by the outer 
 flame, and continues to burn during the return stroke of the 
 firing valve until the chamber comes opposite the passage, when 
 the charge in the combustion chamber of the cylinder is 
 ignited. The maintenance of the firing flame is effected by the 
 flow of gas through the passage. 
 
 Engines of 3^ brake horse-power will work with a consump- 
 tion of about one quart of benzoline per hour per horse-power. 
 This motor works satisfactorily, does not clog in the valves or 
 cylinders, and bids fair to find a good field where gas is unat- 
 tainable, and the local rules concerning the storage for petroleum 
 spirit are not too stringent. 
 
 Dowson's Water-Gas. 
 
 In England it has been found that the use of "Dowson gas," 
 after careful trials, has shown a fuel consumption of only 1.2 
 pounds per hour per indicated horse-power, this amount being 
 equal to the best steam-engine running with steam of a very 
 high pressure. Thus we see that after twenty-five years of im- 
 provement the gas-engine has equaled the best steam-engine in 
 economy. 
 
 This gas is made in the following described apparatus: The 
 retort or generator consists of a vertical cylindrical iron casing 
 which encloses a thick lining of ganister to prevent loss of heat 
 and oxidation of the metal. At the bottom of this cylinder is a 
 grate on which a fire is built up. Under the grate is a closed 
 chamber, and a jet of superheated steam plays into this and 
 carries with it (by induction) a continuous current of air. The 
 pressure of the steam forces the mixture of steam and air up- 
 wards through the fire, so that the combustion of the fuel is 
 maintained while a continuous current of steam is decomposed.
 
 GAS-ENGINES. 345 
 
 In this way the working of the generator is constant, and the 
 gas is produced without fluctuation in quality. The well-known 
 re-actions occur; the steam is decomposed, and the oxygen from 
 the steam and air combines with the carbon of the fuel to form 
 carbon dioxide (CO 2 ), which is reduced to the monoxide (CO) on 
 ascending the fuel column. In this way the resulting gases 
 form a mixture of hydrogen, carbon monoxide, and nitrogen, 
 with a small percentage of carbon dioxide, which usually escapes 
 without reduction. The steam should have a pressure of 24 to 
 30 pounds' per square inch, and is produced and super-heated in 
 a zig-zag coil, fed with water from a neighboring boiler. The 
 quantity of water required is very small, being only about one 
 gallon for each 1,000 cubic feet of gas, and, except on the first 
 occasion when the apparatus is started, the coil is heated by 
 some of the gas drawn from the holder, so that after gas is 
 lighted under the coil the superheater requires no attention. 
 
 For boiler and furnace work the gas can be used direct from the 
 generator, but where uniformity of pressure is essential, as for 
 gas-engines, gas-burners, etc., the gas should pass into a holder. 
 The latter somewhat retards the production, but the steam- 
 injector causes gas to be made so rapidly that a holder is easily 
 filled against a back pressure of i inch to i^ inches of water, 
 and at this pressure the generator can pass gas continuously 
 into the holder, while at the same time it is being drawn off for 
 consumption. 
 
 The nature of the fuel required depends on the purpose for 
 which the gas is used. If for heating boilers, furnaces, etc., 
 coke or any kind of coal may be used; but for gas-engines or 
 any application of the gas requiring great cleanliness and free- 
 dom from sulphur and ammonia, it is best to use anthracite, as 
 this does not yield condensable vapors, and is very free from 
 impurities. Good qualities of this fuel contain over 90 per cent, 
 of carbon, and so little sulphur, that for some purposes purifica- 
 tion is not necessary. For gas-engines, etc., it is, however, 
 better to pass the gas through some hydrated oxide of iron to 
 remove the sulphuretted hydrogen. The oxide can be used 
 over and over again after exposure to the air, and the purifying 
 is thus effected without smell or appreciable expense. Gas 
 made by this process, and with anthracite coal, has no tar and
 
 346 THE STEAM-ENGINE AND THE INDICATOR. 
 
 no ammonia, and the small percentage of carbon dioxide present 
 does not sensibly affect the heating power. A further advantage 
 of this gas is that it cannot burn with a smoky flame, and there 
 is no deposition of soot, even when the object to be heated is 
 placed over or in the flame; this is of importance for the cylin- 
 der and valves of a gas-engine. 
 
 To produce 1,000 cubic feet, only 12 pounds of anthracite are 
 required, allowing 8 to 10 per cent, for impurities and waste; 
 thus a generator which produces 1000 cubic feet per hour, needs 
 only 12 pounds at that time, and this can be added once in an 
 hour or at longer intervals. No skilled labor is necessary. 
 
 The comparative explosive force of coal-gas and the Dowson 
 gas, calculated in the usual way, is as 3.4: i; that is to say, coal- 
 gas has 3.4 times more work than Dowson gas. Messrs. 
 Crossly, of Manchester, England, have made several careful 
 trials of this gas with some of their 3^ horse-power (nominal) 
 engines, and in one trial they took diagrams every half hour for 
 nine consecutive days. These practical trials have shown that, 
 without altering the cylinder of the engine, it is possible to ad- 
 mit enough of the Dowson gas to give the same power as with 
 ordinary coal-gas. It has been seen that the comparative ex- 
 plosive force of the two gases is as 3.4: i, but, as is well known 
 the combustion of carbon monoxide proceeds at a comparatively 
 slow rate; and for this reason and because of the diluents present 
 in the cylinder, which affect the weaker gas more than coal-gas, 
 experience has shown that it is best to allow five volumes of the 
 Dowson for one volume of coal-gas, and then the same uniform 
 power is obtained as with the latter. 
 
 This gives very important economical results; for if the cost 
 of the Dowson gas, as per experiment made, be 10 cents per 
 1,000 cubic feet, is multiplied by five, the cost will be 50 cents 
 per 1,000 cubic feet. Taking the cost of coal-gas to consumers 
 in Philadelphia, which is $1.50 per 1,000 cubic feet, this will 
 represent an actual saving of sixty-six per cent, in running 
 cost. Another practical consideration is that coal-gas requires 
 224 pounds to 250 pounds of coal per 1,000 cubic feet of gas. 
 Dowson gas requires only twelve pounds per 1,000 cubic feet, 
 and multiplying this by five to give the equivalent of 1,000 cubic 
 feet of coal-gas for engine work, there are 60 pounds instead of
 
 GAS-ENGINES. 347 
 
 224 to 250 pounds. This is only 24 to 27 per cent, of the weight 
 of coal required for coal-gas; and in many outlying districts 
 this will effect an appreciable saving in the cost of freight. 
 
 The modern gas-engine does not use slow inflammation, but, 
 when working as it is intended to do, completely inflames its 
 gaseous mixture under compression at the beginning of the 
 stroke. By complete inflammation is meant complete spread of 
 the flame throughout the mass, not complete burning or com- 
 bustion. If, by some fault in the engine or igniting arrange- 
 ment, the inflammation is a gradual one, then the maximum 
 pressure is attained at the wrong end of the cylinder, and great 
 loss of power results. 
 
 Compression is the great advance on the old system; the 
 greater the compression, the more rapid will be the transforma- 
 tion of heat into work by a given movement of the piston after 
 ignition, and, consequently, the less will be the proportional 
 loss of heat through the sides of the cylinder. The amount of 
 compression is, of course, limited by the practical consideration 
 of strength of the engine and leakage of piston, but it is certain 
 that compression will be carried advantageously to a much 
 greater extent than at present. The greatest loss in the gas- 
 engine is that of heat through the sides of the cylinder, and this 
 is not astonishing when the high temperature of the flame in 
 the cylinder is considered. In larger engines, using greater 
 compression and greater expansion, it will be much reduced. 
 As an engine increases in size, the volume of gaseous mixture 
 increases as the cube, while the surface exposed only increases 
 as the square, so that the proportion of volume of gaseous mix- 
 ture used to surface cooling is less the larger the engine be- 
 comes. Taking this into consideration, it may be accepted as 
 probable that an engine of about 50 indicated horse-power could 
 be made to work on 12 cubic feet of coal-gas per indicated 
 horse-power per hour, or a duty of about 32 per cent. 
 
 The gas-engine is as yet in its infancy, and many long years 
 of work are necessary before it can rank with the steam-engine 
 in capacity for all manner of uses; but it can and will be made 
 as manageable as the steam-engine in by no means a remote 
 future. The time will come when factories, railways, and ships 
 will be driven by gas-engines as efficiently as any steam-engine,
 
 348 THE STEAM-ENGINE AND THE INDICATOR. 
 
 and with much more safety and economy of fuel. Gas genera- 
 tors will replace steam boilers, and power will not be stored up 
 in enormous reservoirs, but generated from coal direct, as re- 
 quired by the engine. 
 
 Gas and Steam-Engine Heat Efficiency. 
 
 The heat efficiency of the steam engine is ten per cent, which 
 is probably very nearly as much as can be ever attained; it may 
 be exceeded by using high steam pressures and great expansion, 
 but it will never be possible to attain anything like twenty per 
 cent. The limits of temperature are such that if the steam 
 cycle were perfect, only thirty per cent, of the whole heat could 
 be converted into work; at the boiler pressures and condenser 
 temperatures used, the theoretical efficiency of the steam engine 
 cycle is within eighty per cent, of the cycle of a perfect engine, 
 that is, the efficiency theoretically possible is: 
 
 30 x o. 8 = 24 per cent. 
 
 From experiments made on compound engines, the best 
 results are as follows: 
 
 Absolute efficiency n.i per cent. 
 
 Efficiency of a perfect engine 28.4 per cent. 
 
 Relative efficiency 39. i per cent. 
 
 The engines under test received TOO units of heat from the 
 boiler as dry steam, and gave n.i unites as indicated work in 
 the cylinder. 
 
 With the pressure and temperature given the steam engine 
 cycle, if perfectly carried out, falls short of the cycle of a perfect 
 heat engine between the limits, so that 22.7 per cent, is the 
 maximum efficiency which could be obtained, supposing no 
 other loss than that due to imperfection of the cycle. The cyl- 
 inder losses, condensation, incomplete expansion and misappli- 
 cation of heat, make the actual indicated efficiency n.i per 
 cent, so that half has gone. The furnace loss diminishes the 
 absolute efficiency to 9.2 per cent, and it is extremely improb- 
 able that improvement can ever increase this to twenty per 
 cent, whereas in the best indicated efficiency of the modern 
 gas-engine is as high as twenty-eight per cent. 
 
 A possible efficiency of forty per cent, is probable with the 
 gas-engine.
 
 CHAPTER XV. 
 
 AUTOMATIC CUT-OFF VS. POSITIVE CUT-OFF. 
 
 THE writer deems it highly essential, in order that the me- 
 chanics who build stationary engines, and the engineers in 
 charge, and the manufacturers who buy engines, should have a 
 complete knowledge of their value. 
 
 The superiority of the automatic cut-off engine, over the 
 positive located cut-off engine, is generally conceded by engi- 
 neers, and engine builders; and it now remains to be shown ex- 
 actly what that superiority amounts to that is, with the con- 
 sumption of a given amount of fuel, what will be the useful 
 effect produced by either type of engine? or in other words, to 
 do a given amount of work, what will be the cost of fuel? 
 
 This is a very important matter, not alone to the user of the 
 engine, but to the builder. When a manufacturer or user of an 
 engine is shown that it requires five or six pounds of coal per 
 horse-power per hour, and that substituting an automatic engine, 
 or making a change in his present engine, but three pounds of 
 coal per hour per horse-power will be required, he will not be 
 long in investigating the causes, and making the required 
 change, to accomplish the latter result. 
 
 To arrive at the above, we must have recourse to the Indi- 
 cator; by its application it will register at any instant of time, 
 and under any given circumstances, what is the actual condi- 
 tion and power of the engine, and knowing the coal consump- 
 tion per hour, the comparison can be readily made. 
 
 To illustrate, the writer was called upon to consult in regard 
 to the amount of power developed by two plain slide valve en- 
 gines, fitted with throttling governor. The engines had just 
 been overhauled, by one of the best engineering firms in Phila- 
 delphia. 
 
 The owners of the flouring mill, in which these engines were 
 located found that the coal consumption was large for the num- 
 
 (349)
 
 35O THE STEAM-ENGINE AND THE INDICATOR. 
 
 her of barrels of flour manufactured, and they wished to know 
 whether it was the engines or boilers that were at fault. 
 
 On making a careful survey, I found that the heating and 
 grate surface of each boiler (four in number), was sufficient to 
 generate seventy horse-power each, or a total of 280 horse-power, 
 based on fifteen square feet of heating surface, per horse-power, 
 and was, therefore, satisfied that the trouble lay in the form and 
 condition of the engines. On the report of these facts to the 
 owners, they agreed to make a commercial test of the amount 
 of coal consumed, as well as the quantity of flour that could be 
 made in a period of two weeks, the engines to be indicated once 
 a day, and an account of the coal burnt during the test. 
 
 FIG. 147. 
 
 H.P. 69. 
 
 Mill run day and night, number of hours 144. 
 
 Pounds of coal consumed 100,000. 
 
 Duty in barrels of flour 2250. 
 
 Engines 2. 
 
 Boilers 4. 
 
 Horse-power developed by each engine 69 x 2 = . . . 138. 
 
 Revolutions per minute 55. 
 
 Pressure of steam in pounds per square inch, per gage. 100. 
 
 Diameter of cylinders, in inches 16. 
 
 Length of stroke, in inches 30. 
 
 Coal per hour, per horse-power, in pounds 5. 
 
 The engines ran continuously, day and night, commencing 
 Monday morning at 12, and continued until Saturday night, 
 up to 12 o'clock, for two weeks. With hard firing, and a steam 
 pressure of 100 pounds per square inch, it was all the four 
 boilers could do to run the engines at 55 revolutions per minute, 
 the speed required.
 
 AUTOMATIC CUT-OFF VS. POSITIVE CUT-OFF. 351 
 
 Diagram Fig. 147 is a fair average card taken from the 
 engines during the two weeks' run, and represents the horse- 
 power developed by each engine. 
 
 The above shows that 2,000 pounds of coal was required to 
 make 45 barrels of flour: or, in other words, to manufacture one 
 barrel of flour, 44.45 pounds of coal were required, with the 
 usual connected arrangements. 
 
 FIG. 148. 
 
 n 
 
 H.P. 142. 
 
 Mill runs each day, in hours 13. 
 
 Pounds of coal consumed in 13 hours. . 5400. 
 
 Duty in barrels of flour per day 216. 
 
 Engine, Corliss r. 
 
 Boilers (horizontal flue) 4. 
 
 Horse-power as per indicator diagrams 142. 
 
 Revolutions per minute 55. 
 
 Pressure on boilers per gage in pounds 88. 
 
 Scale of indicator per inch 40. 
 
 Diameter of cylinder, in inches .23. 
 
 Length of stroke, in feet 4. 
 
 Coal per hour, per horse-power, in pounds 2.92. 
 
 About this time there was great competition amongst the 
 flouring mills, and I was instructed to see what, if any, change 
 could be made to produce a barrel of flour with a less amount 
 of coal. 
 
 With the data obtained from Fig. 147, I communicated with 
 the builder of an automatic cut-off engine, who finally went 
 over the premises with me, and agreed to put in one of his 

 
 352 THE STEAM-ENGINE AND THE INDICATOR. 
 
 improved engines, in the place of the two throttling engines, 
 and guarantee forty-Jive per cent, more work, with the same 
 amount of fuel, for a stated sum, and in case his engine failed to 
 perform as above, he would accept a less price than called for in 
 his agreement the reduction to be pro rata. 
 
 Diagram Fig. 148 was taken from the engine erected under 
 the above stipulation boilers and machinery the same. In- 
 stead of running day and night, the time run was 13 hours; 
 during the remaining n hours, the fires were "banked," and 
 engine and machinery allowed to stand. The average result, 
 
 FIG. 149. 
 
 Diameter of cylinder, in inches 32. 
 
 Length of stroke, in inches . . . 84. 
 
 Revolutions per minute 33. 
 
 Piston speed in feet per minute 462. 
 
 Scale of indicator 30 = i". 
 
 under these circumstances, was 80 barrels of flour to the ton of 
 coal (2000 pounds), which is twenty-five pounds to the barrel. 
 
 The above result shows a saving of eighty-two per cent. Had 
 a compound condensing engine been substituted the saving 
 would have been still further increased, as shown in Fig. 125, 
 page 290, where the coal per horse-power was only 1.3 pounds.
 
 AUTOMATIC CUT-OFF VS. POSITIVE CUT-OFF. 353 
 
 Indicator diagram Fig. 149, was taken by the writer from a 
 condensing engine of same make as Fig. 148. 
 
 Coal consumption per hour, per horse-power, two and one- 
 half pounds. 
 
 Diagram, Fig. 150, was also taken from same make of engine, 
 the boiler pressure being 115 pounds per square inch, the dimen- 
 sions of engine being as follows: 
 
 FIG. 150. 
 
 Diameter of cylinder in inches 16. 
 
 Length of stroke in inches 36. 
 
 Revolutions per minute 80. 
 
 Piston speed in feet per minute ........... 480. 
 
 Boiler pressure per square inch 115. 
 
 This diagram shows nearly the whole of the boiler pressure in 
 the cylinder, or 114^ pounds is shown upon the piston, up to 
 point of cut-off, or deducting for back pressure, 113 pounds re- 
 mained effective throughout the whole period of admission, 
 which was for hardly more than one-ninth, we four inches of the 
 stroke. The terminal pressure is 15 pounds above the atmo- 
 sphere, of course very much higher than would correspond to 
 the application of Boyle's law. The back pressure, including a 
 slight amount of compression, hardly amounting to two pounds. 
 The point of cut-off is very sharply marked, although a slight 
 amount of wire-drawing, not worth considering, is to be seen. 
 The exhaust is perfect, expansion being carried to the very end 
 23
 
 354 
 
 THE STEAM-ENGINE AND THE INDICATOR. 
 
 of the stroke before exhausting. The waving appearance of the 
 steam line is, as every engineer will be aware, due merely to 
 the vibration of the indicator pencil, aggravated, it is just pos- 
 sible, by a slight amount of water in the steam. 
 
 Relative Economy of Different Engines. 
 
 The following diagrams, Fig. 151 and Fig. 152, will illustrate 
 the relative engine economy. 
 
 FIG. 151. 
 
 Scale, 40 pounds equal one inch in height. 
 
 Diagram 151 is composed of two indicator cards. Card A is 
 a superior throttling engine diagram, and card B may be re- 
 garded as a medium automatic cut-off engine diagram; it shows 
 excellent engine performance, but the load is rather too heavy 
 for the highest economy, for a non-condensing engine. 
 
 Diagram, Fig. 152, is also a duplex card; A shows a throttling 
 engine card, the average economy of which is better than the 
 general run of this class of engines. 
 
 Diagram B is from an automatic cut-off condensing engine, 
 showing about the highest attainable economy with any engine. 
 
 The mean effective pressure of card A, Fig. 151, is 40.23 
 pounds, and its absolute terminal pressure is 36 pounds. 
 
 The mean effective pressure of card B, Fig. 151, is 41.94 
 pounds, and its absolute terminal pressure is 28 pounds.
 
 AUTOMATIC CUT-OFF VS. POSITIVE CUT-OFF. 
 
 355 
 
 The mean effective pressure of card A, Fig. 152, is 32.34 
 pounds, and its absolute terminal pressure is 30 pounds. 
 
 The mean effective pressure of card B, Fig. 152, is 33.14 
 pounds, and its absolute terminal pressure is 12 pounds. 
 
 I have before called special attention to the fact that the mean 
 effective pressure of any engine diagram is the exact measure of 
 the power developed, and that the absolute terminal pressure is 
 the corresponding measure of the consumption or cost of fuel. 
 Hence, the relative economy of different engines may be thus 
 illustrated. Let each pound of mean effective pressure be called 
 one horse-power; and each pound of absolute terminal pressure 
 represent one dollar ($1.00) paid for fuel. 
 
 FIG. 152. 
 
 Scale, 40 pounds equal one inch. 
 
 Card A, Fig. 151, gives us 40.23 horse-power for $36.00, thus 
 costing $89.37 P er horse-power. 
 
 Card B, Fig. 151, gives us 41.94 horse-powee for $28.00, thus 
 costing $65.38 per horse-power. 
 
 Card A, Fig. 152, gives us 32.34 horse-power for $30.00, thus 
 costing $92.76 per horse-power. 
 
 Card B, Fig. 152, gives us 33.14 horse-power for $12.00, thu. 
 costing $36.21 per horse-power.
 
 356 
 
 THE STEAM-ENGINE AND THE INDICATOR. 
 
 In general, the absolute terminal pressure of throttling engine 
 diagrams will exceed the mean effective pressure, or continuing 
 trie cost illustration, the cost will be more than $1.00 per horse- 
 power, as is the case with diagram, Fig. 184, page 382, which 
 is from a new, carefully made engine. Its mean effective pres- 
 sure is 38.26 pounds, and its absolute terminal pressure is 52 
 pounds, giving a comparative cost of over $1.35 per horse- 
 power. Comparing this with diagram, Fig. 154, which repre- 
 sents 36.73 pounds mean effective pressure, and 22 pounds 
 terminal pressure, a cost of $0.55 cents per horse-power, it will 
 be seen that by substituting the latter engine for the former, a 
 
 FIG. 153. 
 
 3 4 
 
 V 
 
 i. 
 
 Scale, 40 pounds equal one inch. 
 
 saving of 59 per cent, would be effected, and though Fig. 184 
 represents a trifle worse than the average practice with such 
 engines, it is not an exceptionally extreme case. Thousands of 
 engines, new and old, are in use, which, on an average, give no 
 better results. 
 
 Those who use or contemplate using steam-power in loca- 
 tions where sufficient water can be obtained to operate a con- 
 denser, will be interested in diagram Fig. 152, card B. It is a 
 case in which a throttling engine was taken out of a flouring 
 mill and a first-class automatic cut-off condensing engine substi-
 
 AUTOMATIC CUT-OFF VS. POSITIVE CUT-OFF. 357 
 
 tuted. A is a card from the throttling engine, and B was taken 
 from the engine substituted. The saving in fuel is over sixty 
 per cent. 
 
 The above method of illustration is valuable for comparison 
 only. It gives no clue to the actual cost due to a given power 
 (as the preceding article) for the element of time is not con- 
 sidered. 
 
 Diagram Fig. 154 is from an automatic non-condensing engine. 
 
 FIG. 154. 
 
 Scale of diagram on pounds 40. 
 
 Diameter of cylinder in inches 12. 
 
 Stroke of piston in inches 20. 
 
 Revolutions per minute - 150. 
 
 Initial pressure in pounds 80. 
 
 Absolute terminal pressure in pounds 22. 
 
 Mean effective pressure in pounds 36.73. 
 
 Mean effective pressure measured to the adiabatic 
 
 curve in pounds 37-8. 
 
 Percentage of the latter realized 97. 1 7. 
 
 Dry steam per hour per house-power in pounds . . . 19. 18. 
 
 Diagram, Fig. 155, was taken from an automatic condens-
 
 358 THE STEAM-ENGINE AND THE INDICATOR. 
 
 ing engine running light at 108 revolutions per minute, and of 
 the following dimensions: 
 
 FIG. 155. 
 
 Diameter of cylinder in inches 18 
 
 lyength of stroke in inches 30 
 
 Revolutions per minute 108 
 
 Vacuum in inches . 28 
 
 It will be seen by above diagram that the load on this engine 
 FIG. 156. 
 
 was too light for economy, but the diagram is a good one; the 
 admission line and steam line are good; the expansion line coin- 
 cides very closely with the theoretical curve, and there is a free
 
 AUTOMATIC CUT-OFF VS. POSITIVE CUT-OFF. 
 
 359 
 
 exhaust and excellent line of counter pressure. The compres- 
 sion might begin a little earlier with advantage. 
 
 Diagram Fig. 156 was taken from a pair of automatic con- 
 densing engines, n/^ inches diameter by 16 inches stroke, 
 running at 350 revolutions per minute, and developing from 200 
 to 250 horse-power. The vacuum is maintained by a "siphon" 
 condenser. 
 
 The following diagram, Fig. 157, was taken from a condens- 
 ing automatic cut-off engine, dimensions as follows: 
 
 FIG. 157. 
 
 Scale of indicator, 30 pounds equal i inch. 
 
 Diameter of cylinder in inches 20 
 
 Length of stroke in inches 46 
 
 Revolutions per minute 73 
 
 Boiler steam pressure in pounds 65 
 
 Diagram, Fig. 158, is from an automatic condensing engine, 
 revolutions 200 per minute. This is also taken with a light 
 load. The point of cut-off is well defined, and expansion and 
 exhaust lines are good. The line of counter pressure runs 
 nearly parallel with atmospheric line. 
 
 Diagram, Fig. 159, is from a non-condensing engine, revolu- 
 tions, 90; steam pressure, 90 pounds per square inch. The load 
 on this engine is such as we consider a good one for ordinary 
 economical running; the point of cut-off is at about one-fourth 
 stroke. The steam line is good and parallel to that of the 
 boiler pressure, and only a few pounds below it. At the point 
 of cut-off the corner is but slightly rounded, and the expansion
 
 360 THE STEAM-ENGINE AND THE INDICATOR. 
 
 curve follows closely the theoretical line. The exhaust is ex- 
 cellent, as is also the line of back pressure, which comes close 
 to the atmospheric line, and there is a good compression line. 
 
 Fie. 158. 
 
 Diagram, Fig. 160, is from a pumping engine. The cylinder 
 4 feet diameter, with a stroke of 9 feet, the steam and exhaust 
 
 FIG. 159. 
 
 o 
 
 valves are of the double beat class, and making 13 double 
 strokes per minute, the steam being at cut off 13 inches. The 
 maximum steam pressure in the diagram is 29^ pounds, and
 
 AUTOMATIC CUT-OFF VS. POSITIVE CUT-OFF. 
 
 361 
 
 the maximum vacuum is a little over 12 pounds, whilst the 
 average vacuum is n pounds, and the average effective pressure 
 on piston throughout the stroke 13.6 pounds, indicating 201 
 horses, and the duty averages 87,000,000 foot pounds. 
 
 FIG. i 60. 
 
 Diagrams, Fig. 161 and 162, were taken from a passenger 
 locomotive, and both at the same point of cut-off. The larger 
 shaded diagram A, was taken at 40 revolutions per minute, 
 while the other was taken at 260 revolutions per- minute, or 
 about 66 miles an hour. The point of cut-off is one-sixth the 
 stroke, the initial pressure on the piston being 106 pounds, and 
 the slower speed 120 pounds at full speed. 
 
 FIG. 161. 
 
 Diagram, Fig. 162, was taken from the same locomotive in 
 a different notch, the larger diagram B, at 50 revolutions giv- 
 ing 105 pounds initial pressure, the smaller one at 200 revolu- 
 tions with 102 pounds initial pressure. Here the point of
 
 362 THE STEAM-ENGINE AND THE INDICATOR. 
 
 cut-off is between one-fifth and one-sixth the stroke, or exactly 
 22.5 per cent. the locomotive running for a long distance at 
 the same cut-off. 
 
 FIG. 162. 
 
 Diagram, Fig. 163, was taken at 180 revolutions, and the 
 steam appears to have been cut off at about Aths of the stroke. 
 The initial cylinder pressure is 120 pounds. 
 
 The following pair of diagrams, Fig. 164, are from a freight 
 locomotive. The larger one in shaded lines, card C, was taken 
 with a heavy train on an up grade; the other one was taken in 
 running on a level part of the road. 
 
 FIG. 163. 
 
 The diagram, C, was taken at nearly full travel, and the 
 piston received the full boiler pressure of 120 pounds. The 
 smaller one shows an initial pressure of 100 pounds, consider- 
 ably throttled. A remarkable feature of these diagrams is the
 
 AUTOMATIC CUT-OFF VS. POSITIVE CUT-OFF. 363 
 
 trifling back pressure exhibited, which is accounted for by the 
 ample ports, and the size of the blast orifice, five inches diam- 
 eter. 
 
 Diagrams from locomotives, on account of the great variety 
 
 FIG. 164. 
 
 of speeds and point of cut-off at which they are taken, and the 
 variations which they exhibit in the power exerted, are of 
 higher general interest, in some respects, than those obtained 
 
 FIG. 165. 
 
 from either stationary or marine engines; and a careful study of 
 them may confidently be expected to throw light on some ques-
 
 364 THE STEAM-ENGINE AND THE INDICATOR. 
 
 tions about which engineers now differ in opinion. They show 
 at once, for example, at what speed of piston a certain area of 
 port ceases to be sufficient for a given diameter of cylinder, and 
 precisely how velocity of piston, in different degrees, affects the 
 pressure obtained. 
 
 In diagrams Fig. 165, this is illustrated in a remarkable man- 
 ner. This diagram was taken by Mr. Charles Porter, when the 
 boiler was carrying the same pressure of steam, and running in 
 the same notch of the quadrant, and of course, therefore, cut- 
 ting off the steam at the same point of the stroke. The dia- 
 gram, Z>, shown in shaded lines, was taken at a speed not 
 exceeding 50 revolutions per minute, and the one not shaded 
 was taken with the same instrument five minutes later, at the 
 
 FIG. 1 66. 
 
 e 
 
 extreme velocity of 260 revolutions, or 1040 feet travel of pis- 
 ton per minute; the steam pressure in the boiler being 120 
 pounds per square inch, which the more excessive compression 
 made at the higher velocity caused for an instant to be nearly 
 reached in the cylinder. 
 
 Much may be learned from these diagrams from locomotives, 
 upon that most important and vexed question, in what degree 
 the cylinder acts as a condenser of the entering steam, and by 
 what means, and in what degree in non-condensing engines, 
 this vicious action may be corrected; and what, on the other 
 hand, tends to aggravate it?
 
 AUTOMATIC CUT-OFF VS. POSITIVE CUT-OFF. 365 
 
 Diagram Fig. 166 was taken from locomotive No. 51, South- 
 ern Pacific Railroad, with independent cut-off (variable by lever 
 arm and quadrant in cab, under the control of the engineer), 
 built by the Danforth Locomotive Works, Paterson, New Jersey, 
 from designs of Mr. A. J. Stevens, General Master Mechanic of 
 the Central Pacific Railroad, at Sacramento, Cal., with cylinders 
 20 inches diameter and 30 inches stroke, when hauling 496.25 
 tons, on 105 foot grade (inclusive of weight of locomotive and 
 tender of 93 tons), and running 40 revolutions per minute, or 
 at the rate of 6^ miles an hour, cutting off the steam at about 
 
 FIG. 167. 
 
 V 
 
 A- 
 
 one-sixth of the stroke with a pressure of 135 pounds per square 
 inch, and developing (110.92 4- 120.32) 229.36 horse-power, and 
 showing a utilization of eighty-nine per cent, of theoretical dia- 
 gram. 
 
 Diagram Fig. 167 was taken when running at about 10 miles 
 an hour (60 revolutions per minute), cutting off at about one- 
 third of the stroke, and developing 
 
 248.16 + 268.44 507.6 horse-power, 
 
 and shows an effect equal to ninety-seven per cent, of the theo- 
 retical diagram. 
 
 These diagrams show a well maintained steam line up to the 
 point of cut-off, and show a marked contrast in the mean effec-
 
 3 66 
 
 THE STEAM-ENGINE AND THE INDICATOR. 
 
 live cylinder pressure of 59 and 88 pounds per square inch, 
 respectively, as compared with diagram Fig. 168 taken from the 
 Shaw locomotive, cutting off at half stroke under practically 
 similar conditions, and should set at rest any doubts as to the 
 value of an independent variable cut-off valve for locomotives. 
 
 Diagram, Fig. 168, card P\ in outline, was taken at 27 revo- 
 lutions per minute. It will be seen that at this slow speed the 
 steam attained very nearly the mean effective pressure of that 
 of the boiler, namely 120 pounds per square inch on the piston 
 following very nearly full stroke, and developing 130 horse- 
 power running at the rate of 5^ miles per hour up a grade of 
 63 feet per mile. 
 
 Let us now compare this diagram with card f, in shaded lines, 
 
 FIG. 168. 
 
 taken on a level at a speed of 24 miles an hour, pulling the same 
 load as indicated in diagram F, with a boiler pressure of 130 
 pounds per square inch, and a mean effective cylinder pressure 
 of 42.6 pounds per square inch, steam being cut off at half 
 stroke; throttle valve partially closed and developing 211.29 
 horse-power. The low initial steam pressure of 58 pounds per 
 square inch, is due to the partial closure of the throttle valve, 
 but is well maintained without expansion up to point of cut-off. 
 Diagram, Fig. 169, was also taken from this locomotive when 
 running at the rate of 65 miles an hour, corresponding to 315 
 revolutions per minute, or a piston speed of 1,260 feet, and a
 
 AUTOMATIC CUT-OFF VS. POSITIVE CUT-OFF. 
 
 367 
 
 boiler pressure of 120 pounds per square inch, cutting off at 
 9. 75 inches of the stroke. 
 
 The load consisted of two passenger cars of 40,000 pounds 
 each. 
 
 The initial steam pressure being only 84 pounds, expanding 
 on the steam line down to about 56 pounds at the point of cut- 
 off, the line of admission pressure should be parallel with the 
 atmospheric line in a properly arranged valve motion up to the 
 point of cut-off, or nearly so. The fall in pressure as the piston 
 advances, as shown in this diagram, is the best evidence that 
 the opening for admission of steam is insufficient, and the steam 
 is wire drawn. 
 
 The point of cut-off should be sharp and well defined, see 
 
 FIG. 169. 
 
 Figs. 166 and 167; otherwise, as in this case, it shows that the 
 valve does not close fast enough. 
 
 Diagrams Figs. 170 and 171 were taken by the writer, who 
 was a member of a commission appointed by the Select and 
 Common Councils of the city of Philadelphia, to test the 
 Worthington Pumping Engine at Belmont, in May, 1872. 
 
 Diagram Fig. 170, is an exact reduced copy of a water card 
 taken at 4:10 p. m. from one of the five million gallon pump 
 cylinders. This diagram shows no rounded corners, nor wavy
 
 368 
 
 THE STEAM-ENGINE AND THE INDICATOR. 
 
 or jagged lines whatever. This shows conclusively, that the 
 water valves seat themselves perfectly, due to the practical uni- 
 formity of motion of the water column, therefore, causing no 
 shock or jar. The mean water pressure was 86. 724 pounds per 
 square inch, and the height due to this pressure, the water being 
 
 FIG. 170. 
 
 66, was 200.46 feet, and the lift from center of gage to water 
 in pump well, was 17.28 feet. Total height, including frictional 
 resistance, 217.74 feet. 
 
 FIG. 171. 
 
 Hi*h Pressure Cylinder 
 
 46.40 H> 
 
 78.14 H 
 
 Low Pressure Cylinder. 
 
 Diagrams, Fig. 171, represents the steam cylinders, there 
 being two non-condensing, and two condensing cylinders. The 
 boilers evaporated about 30 pounds of water per hour, per horse- 
 power, showing a consumption of about four pounds of coal 
 per hour, per horse-power,
 
 AUTOMATIC CUT-OFF VS. POSITIVE CUT-OFF. 
 
 369 
 
 The diagram Fig. 172, was taken from a plain slide valve 
 engine, fitted with an independent cut-off valve and governor, 
 similar to a "Tremper." 
 
 The boiler pressure was 75 pounds, and the engine was run- 
 ning 58 revolutions per minute. 
 
 The valves were fairly set. The cut-off valve closed promptly 
 
 PIG. 172. 
 
 enough, and the steam in the cylinder by expansion fell in 
 pressure to about 23 pounds above the atmosphere, at about $ of 
 the stroke, at which point of the stroke more steam through 
 
 FIG. 173. 
 
 some leak, not at the time discovered, was admitted to the 
 cylinder, the result being that the pressure in the cylinder rose 
 to 26 pounds at one end and to 33 pounds at the other end of 
 24
 
 370 THE STEAM-ENGINE AND THE INDICATOR. 
 
 the cylinder, causing the distortion as shown at the terminal 
 end of the diagram. 
 
 This engine, as will be seen from the diagram, had no com- 
 pression whatever. 
 
 Compression also serves to overcome the momentum of the re- 
 ciprocating parts, and to reduce the strain upon the connections, 
 
 FIG. 174. 
 
 caused by the sudden application of the steam pressure at ad- 
 mission. 
 
 In the second place, compression is desirable on the ground 
 of economy in the consumption of steam. It fills the wasteful 
 clearance spaces pf the cylinder with exhaust steam, and in 
 
 FIG. 175. 
 
 the case last cited the clearance was large, from the fact that 
 the cut-off valve set on top of the steam chest, all of which had 
 to be filled with steam from the boiler. True, compression pro- 
 duces a loss by this increased back pressure which it occasions, 
 but the loss is more than covered by the gain resulting from the 
 reduction of clearance waste.
 
 AUTOMATIC CUT-OFF VS. POSITIVE CUT-OFF. 371 
 
 Theoretically, the greater the amount of exhaust that is 
 utilized by compression, the less the consumption of steam. 
 Practically, it is not advisable to compress above the boilei 
 pressure, as shown in diagram, Fig. 173. 
 
 Diagram, Fig. 174, is from the same engine that produced 
 Fig. 173, and was taken after resetting the valves. 
 
 In non-condensing, automatic cut-off engines with three per 
 cent, clearance, with a boiler pressure of 80 pounds per square 
 inch, and cutting off at about one-fifth of the stroke, and ex- 
 hausting under a minimum back pressure, the gain produced 
 by compressing up to boiler pressure over working under the 
 same conditions without compression, as shown by diagram, 
 Fig. 175, will not be less than about six per cent. In a con- 
 densing engine, running under similar conditions, the gain 
 should be larger, also with an earlier cut-off. 
 
 The steam line in automatic cut-off engines should be par- 
 allel with the atmospheric line (see Figs. 88, 153, 159 and 167), 
 and should not be more than three pounds less than the boiler 
 pressure; the point of cut-off is where the expansion line com- 
 mences to fall abruptly and shows during what part of the stroke 
 the steam is admitted; through the remainder of the stroke the 
 steam expands gradually, reducing the pressure as shown by 
 the dotted lines. Just before the end of the stroke the exhaust 
 should commence, open as shown at g in Fig. 166 and 167. 
 
 The back pressure should not in any engine exceed one pound 
 when exhausting into the atmosphere. 
 
 The dotted line in Figs. 166 and 167 represents the theoreti- 
 cal power of the amount of steam exhausted from the cylinder 
 of the same size, with no losses from friction in the passages, 
 back pressure or clearances. The proportion of the area of the 
 actual, the one in outline, to the theoretical, the one in dotted 
 line, represents the relative efficiency of the several diagrams as 
 stated on page 365, showing eighty-nine and ninety-seven per 
 cent, efficiency due to a properly proportioned cut-off engine.
 
 CHAPTER XVI. 
 
 MISCELLANEOUS. 
 Leakage of Steam-Engines as shown by the Diagram. 
 
 The following diagram, Fig. 176, was taken from an auto- 
 matic cut-off engine, of the following dimensions: 
 
 The clearance, or waste, room between the cut-off valve and 
 piston, when the latter is at the end of its stroke, amounts to 
 seven per cent, of the piston displacement. 
 
 FIG. 176. 
 
 Diameter of cylinder in inches 8 
 
 Length of stroke in inches 16 
 
 Revolutions per minute 287 
 
 Diameter of rod in inches 1.5 
 
 Boiler pressure in pounds per square inch 103 
 
 The above diagram, Fig. 176, is from the back, or follower 
 
 end of cylinder, and shows that the admittance of steam was 
 
 cut off when the piston moved only about 0.2 of the stroke, 
 
 whilst the terminal pressure shows the steam to have been cut 
 
 (372)
 
 LEAKAGE OF PISTON AND VALVES. 373 
 
 off" at e, or 0.275 f tne stroke, and the difference is the leakage 
 of steam through the distribution valve after the steam was cut 
 off. 
 
 Adiabatic curves of expansion have been constructed on the 
 diagrams, Fig. 176, both for the terminal pressure and for the 
 apparent point of cut-off. 
 
 The adiabatic curve e,f,g\s for the terminal pressure, and 
 b, x, D that for the apparent point of cut-off. 
 
 The clearance of the piston, amounting to seven per cent., has 
 been added to the stroke on the card B V. Then the percent- 
 age of leakage is found in the following way: 
 
 Percentage = *> (*.*-*.*) . , l 
 
 a, c. 
 
 For the use of this formula the vacuum line V Fis extended 
 one-tenth beyond V and divided into ten equal parts, which 
 forms a scale for measuring k b and k e. 
 
 By this scale it is found that k b = 12, and k e = 27. 
 
 Leakage of steam % = 100 ( 2 7 I2 ) 55<5 per cent. 
 
 It is assumed in this formula that the exhaust valves are per- 
 fectly tight, which is probably not the case, and the full leakage 
 can therefore not be determined by the indicator cards. 
 
 That is to say, that 55.5 per cent, of all the steam in the 
 cylinder, when the piston reaches the end of the stroke, had 
 leaked through the valve face during expansion, or after the valve 
 had cut off the steam. Had all the steam been admitted from 
 the beginning of the stroke and cut off at <?, it would have pro- 
 duced the adiabatic curve e, f, g, and the useful effect would 
 then have been represented by the area C = e, f, g, D, h and , 
 instead of the area D = k, b, x, g, D and ^, which was actually 
 produced. The loss of effect is represented by the enclosed 
 area E = e, f, g, and b. 
 
 Loss of effect % l E = per cent 2 
 
 By actual measurements of these areas we find E = o. 49 and
 
 374 DISTORTED ENGINE DIAGRAMS. 
 
 C= 3. 1 7 square inches. Then the loss of effect by leakage 
 will be: 
 
 % = 100 x 0.49 = I5 . 45 per cent. 
 
 As before stated, the leakages of the exhaust valves are not 
 included in this calculation, which therefore does not represent 
 the full leakage. 
 
 The natural effect of the steam is represented by the whole 
 area F = V, B, b, e, / g, V, which divided into the realized 
 effect Z>, gives the fraction of the natural effect or duty obtained 
 from the steam. 
 
 Duty % = IO D = percentage. 
 r 
 
 Distorted Indicator Diagrams. 
 FIG. 177. 
 
 The above rather antique looking diagram, Fig. 177, is from 
 a modern built automatic cut-off engine. The size of this 
 engine is 16 inches diameter, 48 inches stroke, running 40 revo- 
 lutions per minute, boiler pressure 70 pounds per square inch, 
 scale of indicator 40 pounds per inch. 
 
 The steam admission does not commence until the piston has 
 traveled about one-sixtn of the stroke. The exhaust valve had 
 no lead, not opening until the piston had reached the end of its 
 stroke; the piston being retarded at the commencement of its 
 return stroke, by about 30 pounds per square inch back pres- 
 sure, and did not reach the atmospheric line, A D, at all, until 
 on the next stroke, as shown by the loop which was caused by
 
 MISCELLANEOUS. 
 
 375 
 
 the lost motion in the connections of exhaust valve, at the 
 moment of the piston changing its motion. 
 
 The maximum pressure, before cut-off, was comparatively 
 low, the average back pressure was high, and there was entire 
 absence of compression. 
 
 The valves were re-set, and the result was, the engine con- 
 sumed one-half the steam, and developed more power than 
 shown above. 
 
 The following diagrams, Figs. 178 and 179, were taken from 
 an upright automatic cut-off engine, 42 inches diameter, and 42 
 inches stroke. The engine was located in a rolling mill making 
 steel rails. At times the engine came very nearly to a stand 
 still with an ignot in the rolls and it was with difficulty that 
 sufficient steam could be generated in the boilers to run the 
 
 FIG. 178. 
 
 mill at proper speed. The writer was called on to locate the 
 trouble. On applying the indicator, diagrams Figs. 178 and 
 179, were the result. 
 
 The valves were reset and the piston packing also set out, 
 and the result was the diagrams, Figs. 180 and 181. 
 
 The engine was running at full speed and steam constantly 
 blowing off at the safety valves on the boilers. 
 
 Diagrams, Fig. 180, A, a, represent the power when train of 
 rolls was running empty. Diagrams B C and C when ignot 
 was passing through the rolls. Cards C, Fig. 180, and C, Fig. 
 181, show that no cut-off took place, the steam following the 
 piston its full stroke. This engine being a Corliss does not cut 
 off if its full load is maintained beyond half stroke.
 
 376 THE STEAM-ENGINE AND THE INDICATOR. 
 
 The Economy of a Steam-Engine. 
 
 The economy of a steam-engine is expressed in terms of the 
 number of pounds of water consumed per horse-power per hour. 
 The rate of water consumption is the only intelligible expression 
 for the engine alone, as the amount of fuel used must depend 
 largely upon the kind of boiler and its conditions, the manner 
 in which it is set and fired, the quality of the fuel, the draft, and 
 numerous other factors, for which the engine is in no way 
 responsible. 
 
 How to Calculate the Amount of Steam (Water) Con- 
 sumed from an Indicator Diagram. 
 
 It is not claimed that the theoretical rate of water consump- 
 tion as deduced from the diagrams can ever be realized in prac- 
 tice. A certain amount will always be lost from condensation, 
 
 FIG. 179. 
 
 leakage and unevaporated foam in the steam, which no process 
 of calculation makes allowance for. This loss may amount in 
 some cases to nearly one-half, and 25 to 30 per cent, is not above 
 the average under ordinary conditions. But for the purpose of 
 comparing the economy of different engines, or the relative 
 economy of different pressures and loads on the same engine, it 
 possesses great value, as whatever uncertainty may exist as to 
 the amount of unindicated loss, it is safe to assume an equal per 
 cent, of loss in each case, and hence the comparison would not 
 be affected. 
 
 As the mean pressure during the stroke measures the work 
 done, so the pressure at the end of the stroke measuies the steam 
 consumed in doing it. 
 
 The useful evaporation of a boiler may through the steam- 
 engine be approximately calculated from the indicator diagrams
 
 MISCELLANEOUS. 
 
 377 
 
 by ascertaining the weight of the water existing in the form of 
 steam in the cylinder at every point in the stroke; not absolutely 
 since we do not know exactly the weight of steam at different 
 temperatures but without doubt, very nearly. This, when 
 measured just before the opening of the exhaust, is the weight 
 of water accounted for by the indicator. 
 
 From a variety of causes, the weight of water so accounted for 
 can never be the full weight required to supply the boiler, as it 
 is not possible to estimate the total amount, except by measur- 
 ing the feed water, for the following reasons: 
 
 FIG. 1 80. 
 
 First. A certain amount of water always disappears from a 
 boiler in ways which cannot be accounted for. If a boiler is 
 shut perfectly tight, without visible outlet for any steam what- 
 ever, and a steam pressure is maintained in it, the water will 
 gradually subside. When experiments are to be conducted, the 
 rate of this disappearance from the boiler, under the pressure to 
 be employed, ought to be ascertained. 
 
 Second. Unless the steam is superheated, more or less water 
 is carried over to the engine mechanically. This is especially 
 the case with boilers which show a great evaporative capacity. 
 
 Third. As soon as the steam leaves the boiler it begins to be 
 condensed. It can receive no more heat from any source, but 
 it must impart heat to everything and supply all loss from 
 radiation.
 
 378 THE STEAM-ENGINE AND THE INDICATOR. 
 
 Fourth. A certain amount of condensation is produced by the 
 conversion during the expansion of heat into mechanical work. 
 
 Fifth. A portion of the steam is always condensed as it enters 
 the cylinder from coming in contact with the surfaces which 
 have just been cooled by being exposed to the colder vapor of 
 the exhaust, and especially by the evaporation, at the same time, 
 of moisture from them, abstracting the heat necessary to supply 
 to such moisture the heat of vaporization. 
 
 FIG. 181. 
 
 To ascertain the weight of the steam, of which the indicator 
 shows the pressure, we have first to determine the volume of the 
 steam or the capacity of the chamber which it fills. 
 
 If a piston one inch square moves twelve inches, it will do work 
 equal to one foot pound for every pound per square inch pres- 
 sure of steam. That is to say, every twelve cubic inches of cyl- 
 inder area represents one foot pound of mean effective pressure. 
 
 Twelve cubic inches equal T?T of a cubic foot. The piston 
 then must sweep a volume of 33 ' x 13749.9, or say 13,750 
 cubic feet per hour per horse-power, if mean pressure equals 
 unity. 
 
 The volume of steam used per horse-power varies inversely as 
 the effective pressure, and if we call the weight of a cubic foot 
 of steam at the pressure of release W, and the mean effective 
 
 pressure (m e p^) we have the formula 
 
 13.750 
 
 m e p 
 
 X W= pounds of
 
 MISCELLANEOUS. 
 
 379 
 
 water evaporated per indicated horse-power, exclusive of waste 
 by condensation and leakage. 
 
 This formula is not quite correct, as it does not allow for the 
 effects of clearance and compression. 
 
 To Compute the Economy of Water Consumption. 
 
 The following method is in geneial use for finding the rate of 
 water consumption for the engine alone: 
 
 Rule. Divide the constant number 859,375 by the volume of 
 steam at the terminal pressure, and by the mean effective pres- 
 sure (m e p\ The quotient will be the desired rate. 
 
 FIG. 182. 
 
 \ 
 
 This constant is the number of pounds of water that would be 
 used in one hour by an engine developing one horse-power, if 
 run by water (instead of steam) at one pound pressure per square 
 inch. Then, with pressure of more than one pound the amount 
 required would be as many times less as the pressure was greater 
 than one pound, and when steam is used, the amount would be 
 as much less as the volume of the steam at the pressure at which 
 it is released is greater than an equal weight of water. Hence 
 the above rule. The constant is found as follows: The standard 
 horse-power being 33,003 foot pounds, or 33,000 pounds lifted 
 one foot per minute, would be equivalent to 33,000 X 12 =
 
 380 THE STEAM-ENGINE AND THE INDICATOR. 
 
 396,000 pounds lifted one inch per minute. Hence an engine 
 whose piston displacement was 396,000 cubic inches per minute 
 would develop one horse-power with one pound mean effective 
 pressure on the piston. This for one hour would be 396,000 x 
 60 minutes = 23,760,000 cubic inches per hour. Then suppose 
 the engine to be run by water at one pound pressure per square 
 inch, instead of steam, and taking the number of cubic inches 
 
 of water per pound at 27,648, this 23 ^ 7 ^'^ 859,375, which 
 
 is the desired constant. 
 
 Example. Diagram Fig. 182, was taken from an improved 
 automatic cut-off engine. 
 
 Applying the rule of analysis, we find first that the combined 
 length of the 20 lines, i, 2, 3, 4, &c., is 2i T V inches, showing 
 that we have 42 T 2 o pounds mean effective pressure. 
 
 The terminal pressure (T. V.) is 27 Ibs. ; the volume at that 
 pressure is given at 926; that is, one cubic inch of water at a 
 temperature of 60, makes 926 cubic inches of steam at 27 Ibs. 
 pressure per square inch. Hence by the rule the rate of water 
 
 consumption becomes 6 5 ?? = 2 1.74 Ibs. of water per in- 
 dicated horse-power per hour. 
 
 But early exhaust closure saves some steam, while exhausting 
 from the clearance at a pressure greater than the back pressure 
 wastes some, and the process, so far, makes no allowance for 
 either. When the maximum compression equals the terminal, 
 the loss and gain are equal, but when the compression exceeds 
 the terminal, there is a balance of gain from compression, equal 
 to the excess of steam compressed into the clearance space over 
 that exhausted from it, and when the terminal exceeds the 
 compression, there is a balance of loss due to exhausting from 
 the clearance space, hence the following rule: 
 
 To Make Allowance for Compression and Clearance. 
 
 ist. Fix the terminal pressure at point 7^(Fig. 182 and other 
 diagrams) where it would have been if the steam had not been 
 released till the end of the stroke was reached. 
 
 2d. Draw the line T 2 parallel with the atmospheric line, 
 which will cut the compression line at 1, at which point the 
 quantity of steam exhausted from the clearance has been re-
 
 MISCELLANEOUS. 
 
 381 
 
 stored, and the consumption will be as much less than the rule 
 shows, as the line T 1 is shorter than the line T%, or the length 
 of the diagram. 
 
 3d. Multiply the result obtained by the rule by the length of 
 the line T 1, and divide the product by the length of the line 
 T%. The result will be the rate of consumption corrected for 
 both clearance and compression. 
 
 Example. The result obtained from the rule is 21.74 Ibs., 
 the length of line T 1 is 3.17 inches, and the length of line T% 
 is 3^ inches, hence 21.74 X 3.17 -+- 3.5 = 19.69 Ibs. per indi- 
 cated horse-power per hour, the corrected rate. It should be 
 understood that this rate is theoretical, and assumes perfect con- 
 ditions, such as dry steam, entire absence of loss from leakage, 
 condensation, &c. 
 
 FIG. 183. 
 
 Diagram, Fig. 183, illustrates a method of finding the point 
 1 (X 1} in the terminal line, when that line is located below the 
 atmospheric line, and consequently below any part of the com- 
 pression curve defined on the diagram. 
 
 Select any point in the actual curve, as at L. From that 
 point draw a line at right angles to atmospheric line, to terminal 
 line, as at O. Then from V, where the clearance line cuts the 
 vacuum line, draw a diagonal line through point O to point f\ 
 (same height as point L\ then a line at right angles to atmo- 
 spheric line, from F, will cut the terminal line at the proper 
 place for point 1. The process will be recognized as the same
 
 THE STEAM-ENGINE AND THE INDICATOR. 
 
 in principle as that used for finding a point in the isothermal 
 expansion curve. 
 
 The consumption for diagram, Fig. 183, is as follows: 
 The mean effective pressure is 2 Ibs., and the terminal pres- 
 sure D. V. is 6^ pounds. The volume for 6^ pounds is given as 
 
 3427 (the mean for 6% and 7 Ibs.), hence ^ 59375 2 = 125.4 Ibs. 
 
 Line XI is 2^ inches long, and line X2 (or whole length of 
 card) is 3^ inches, hence 125.4 X 2. 75 -*- 3.5 = 98.53 Ibs. per 
 indicated horse-power, per hour, the correct rate. This will 
 serve to show the utter absurdity of very light loads. 
 
 PIG. 184. 
 
 When the compression pressure does not equal the terminal, 
 as in diagram Fig. 20, page 116, the curve may be continued 
 upward and beyond the end of diagram until it reaches the 
 height of terminal line. The extension may be made by the 
 eye with sufficient accuracy. In this case distance g 1 becomes 
 the longer one, and the result obtained from the rule is in- 
 creased, as distance g 1 is always the multiplier, and g 2 the 
 divisor in the corrections. 
 
 Diagram, Fig. 184, illustrates a method of locating the clear- 
 ance line from the conformation of compression curve, as 
 follows: First select two points in the curve and form a paral-
 
 MISCELLANEOUS. 
 
 383 
 
 lelogram through said points as illustrated. Then draw a 
 diagonal line through points O P, till it intersects the vacuum 
 line, the clearance line will be a vertical one drawn from said 
 point of intersection, as V. D. The degree of accuracy will 
 depend upon the perfection or tightness of piston and valve, 
 leakage generally having the effect of showing too much clear- 
 ance. 
 
 Computation Table. Thus far the constant number 859,- 
 375 in connection with the volumes of steam, has been used for 
 computing the rate of water consumption. To make the pro- 
 cess available, a table of volumes must always be present, and 
 to render our instructions complete we should publish such a 
 table, but in lieu of that, we submit herewith a Computation 
 Table. 
 
 COMPUTATION TABLE NO. 8. 
 
 w 
 
 P 
 
 W 
 
 P 
 
 W 
 
 P 
 
 W 
 
 P 
 
 W 
 
 P 
 
 W 
 
 P 
 
 W 
 
 39.10 
 
 38.47 
 
 20 
 
 21 
 
 34-99 
 34.89 
 
 37 
 38 
 
 33-72 
 33-67 
 
 54 
 
 55 
 
 32.98 
 32.94 
 
 7i 
 72 
 
 32.46 
 32.43 
 
 88 
 89 
 
 32.07 
 32-05 
 
 105 
 106 
 
 31-73 
 31.71 
 
 37-95 
 
 22 1 34.79 
 
 39 
 
 33-62 
 
 56 
 
 32.91 
 
 73 
 
 32.40 
 
 90 
 
 32.03 
 
 107 
 
 31.69 
 
 37-54 
 
 23 
 
 34-70 
 
 40 
 
 33-57 
 
 57 
 
 32-88 
 
 74 
 
 32.38 
 
 91 
 
 32.00 
 
 108 
 
 31-67 
 
 37-22 
 
 24 
 
 34.61 
 
 4' 
 
 33-52 
 
 58 
 
 32-85 
 
 75 
 
 32.36 
 
 92 
 
 31.98 
 
 109 
 
 31.65 
 
 36.93 
 
 25 
 
 34-53 
 
 42 
 
 33-47 
 
 59 
 
 32-82 
 
 76 
 
 32-34 
 
 93 
 
 3L96 
 
 no 
 
 31-63 
 
 36.67 
 
 26 
 
 3445 
 
 43 
 
 33-42 
 
 60 
 
 32-79 
 
 77 
 
 32.32 
 
 94 
 
 31-94 
 
 III 
 
 31.61 
 
 36.44 
 
 27 
 
 34-37 
 
 44 
 
 33-38 
 
 61 
 
 32.76 
 
 78 
 
 32-30 
 
 95 
 
 31.92 
 
 112 
 
 31-59 
 
 36.24 
 
 28 
 
 3429 
 
 -45 
 
 33-34 
 
 62 
 
 32.73 
 
 79 
 
 32-27 
 
 96 
 
 31.90 
 
 "3 
 
 31-57 
 
 36.06 
 
 29 
 
 34-22 
 
 46 
 
 33-30 
 
 63 
 
 32.70 
 
 80 
 
 32-25 
 
 97 
 
 31.88 
 
 114 
 
 31-55 
 
 35.89 
 
 30 
 
 34-15 
 
 47 
 
 33-26 
 
 64 
 
 32.67 
 
 8 1 
 
 32.23 
 
 98 
 
 31.86 
 
 115 
 
 31-54 
 
 35-73 
 
 31 
 
 34.08 
 
 48 
 
 33-22 
 
 65 
 
 32.64 
 
 82 
 
 32.20 
 
 99 
 
 31.84 
 
 116 
 
 31-53 
 
 35-59 
 
 32 
 
 34-01 
 
 49 
 
 33-18 
 
 66 
 
 32.61 
 
 83 
 
 32.18 
 
 TOO 
 
 31.82 
 
 117 
 
 31-52 
 
 35.46 
 
 33 
 
 33-95 
 
 5<> 
 
 33- H 
 
 67 
 
 32-58 
 
 84 
 
 32.16 
 
 IOI 
 
 31.80 
 
 118 
 
 31-51 
 
 35-34 
 
 34 
 
 33-89 
 
 51 
 
 33-io 
 
 68 
 
 32.55 
 
 85 
 
 32-14 
 
 102 
 
 3I-78 
 
 119 
 
 31-50 
 
 35-22 
 
 35 
 
 33-83 
 
 52 
 
 33- 6 
 
 69 
 
 32-52 
 
 86 
 
 32.12 
 
 103 
 
 31-77 
 
 120 
 
 3M9 
 
 35-10 
 
 36 
 
 33-77 
 
 53 
 
 33-02 
 
 70 
 
 32.49 
 
 87 
 
 32.09 
 
 104 
 
 31-75 
 
 121 
 
 31-43 
 
 It has been stated in our definitions of mean effective and 
 terminal pressures, that the former is the meastire of the power 
 developed, and the latter the corresponding measure of the 
 consumption or cost of the power. Hence we should be enabled 
 to find a number which, if multiplied by the terminal pressure, 
 and divided by the mean effective pressure, would give us the 
 rate of water consumption at once, excepting the required cor- 
 rection for compression and clearance.
 
 384 THE STEAM-ENGINE AND THE INDICATOR. 
 
 Explanation of Table No. 8. 
 
 The numbers in columns P stand for so many different total 
 terminal pressures, and the numbers in columns Fare the num- 
 bers sought, as referred to above. Each of the numbers under 
 W \s found by dividing our constant number 859,375, by the 
 numbers to the left of it under P, representing terminal pres- 
 sure, and that quotient by the volume of steam at that pressure. 
 Each number under W will therefore represent the rate of water 
 consumption, for a diagram having both mean effective and 
 total terminal pressures, the same as the number to the left of it 
 under P; and when any given diagram has a mean effective 
 pressure greater than its total terminal pressure, its rate of con- 
 sumption will be proportionately less than if they were the 
 same, and if the mean effective is less, the rate will be propor- 
 tionately higher. 
 
 Hence the rule: Find in column P the total terminal pres- 
 sure of the diagram or the number nearest it. For fractions of 
 a pound in the terminal, an approximate average of or mean of 
 two numbers, should be found, to insure accurate results. Then 
 multiply the number under ^opposite the number so found by 
 the total terminal pressure of the diagram, and divide the pro- 
 duct by its mean effective pressure; the quotient will be the rate 
 in pounds of water per I. HP. per hour, subject, however, to the 
 correction for compression and clearance, as previously ex- 
 plained. 
 
 Example for Use of Table No. 8. 
 
 Referring to diagram, Fig. 182, we have total terminal pres- 
 sure T V= 27 pounds, mean effective pressure 42.2 pounds, 
 number in table under Wior 27 pounds: is 34. 37. Line T 1 = 
 3.17 inches and line T% = 3.5 inches. 
 
 Then 
 
 34-37 X 27 __ 2I>99 pounds of water, 
 
 Correction : 
 
 21-99 X 3-17 = I9>91 pounds of water, 
 3o 
 
 per indicated horse-power per hour, corrected rate. 
 
 By reference to Fig. 182 it will be seen that the point T is
 
 MISCELLANEOUS. 385 
 
 where the terminal pressure would have been if the steam had 
 not been released until the end of the stroke was reached; the 
 dotted line T 1 is parallel with the atmospheric line, and cuts 
 the compression curve at a point where compression has restored 
 the amount of steam exhausted from the clearance. 
 
 The above Table No. 8 is best illustrated by the following 
 comparison of different types of engines. We would further ex- 
 plain by the double diagram Figure 185, which graphically illus- 
 trates the comparative steam economy between "throttling" and 
 "automatic cut-off' 1 ' 1 regulation. The diagram is engraved from 
 actual cards. Both represent very favorable loads, and each 
 
 FIG. 185. 
 
 shows excellent results for its type of engine. The "throt- 
 tling" card C C develops 40.25 pounds mean effective pressure, 
 with 36 pounds terminal pressure (TV\ while the cut-off card 
 BB develops 42 pounds mean effective pressure, with only 28 
 pounds total terminal pressure (T'V\ Thus the cut-off engine 
 was developing 42 pounds of work with an expenditure of its 
 cylinder full of steam at 28 pounds pressure, while the "throt- 
 ling" engine developed but 40.25 pounds of work with its cylin- 
 der full of steam at 36 pounds pressure per square inch. 
 
 The comparison in percentages is very nearly as follows, bear- 
 25
 
 386 THE STEAM-ENGINE AND THE INDICATOR. 
 
 ing in mind that the total pressure (viz: pressure above vacuum 
 line), is the measure of the consumption of steam, and the mean 
 effective pressure is the corresponding measure of the power 
 developed. Assuming the constant number 34 (which, while 
 not precisely correct for either terminal, is the mean between 
 the two, dropping fractions, in favor of the throttling card), 
 then for the cut-off engine the result is as follows: 
 
 34 x 2 = 22.7 pounds of dry steam per indicated horse-power 
 
 per hour. 
 
 For the throttling engine card : 
 
 = 30.4 pounds of dry steam per indicated horse-power 
 
 Comparison : 
 
 30 ' 4 ~^' 7XIOO== 34 P er cent of steam, 
 
 used by the throttling engine more than by the cut-off engine 
 for the same amount of work. This shows the advantage in the 
 use of an automatic cut-off engine over that of the throttling 
 engine. This difference can always be relied upon whenever 
 the cut-off engine is given a fair load. 
 
 Evil of Light Loads. 
 
 No other condition is so destructive to good economy, as an 
 engine over-large for its work: this fact should be well under- 
 stood by purchasers of steam-engines. 
 
 With a too light load, internal condensation conies in to the 
 fullest extent. The cut-off is early, hence the expansion and 
 consequent fall of temperature are excessive. It admits of no 
 denial that the immediate surfaces, at least of the interior of the 
 cylinder, share in this fall of temperature, which still further 
 continues during the exhaust, and experiment has also shown 
 that a deposit of water like dew takes place on them. All these 
 surfaces have got to be reheated, and all this water re-evaporated, 
 at the expense of the next admission of steam, which being
 
 MISCELLANEOUS. 387 
 
 necessarily small, from the light load, suffers severely from con- 
 densation. With a substantial load, the expansion and cooling 
 are much less, and the amount of steam admitted to restore the 
 heat is much larger. 
 
 We must not be misunderstood as advocating overloading. 
 We do wish, however, to correct the fatal idea, arising partly 
 from the manufacturer's fear of insufficient power, and partly 
 from the impression that economy increases definitely with in- 
 crease of expansion, that "it is no mistake to get an engine too 
 large." Moreover, in non-condensing engines, a direct loss 
 occurs by expansion below atmosphere, thus creating a vacuum 
 resistance on the impelling side of the piston, at the expense of 
 the fly-wheel; also see Fig. 25, and Figs. 183 and 186. 
 
 FIG. 186. 
 
 Efficiency or Duty of Pumping Engines. 
 
 The term "duty" is a measure of the efficiency of a pump- 
 ing engine, and is based upon the delivery of water into the 
 reservoir (with the friction of the water pipes) per hundred 
 pounds of coal. Duty is usually expressed in foot pounds. 
 
 The method usually employed neglects the actual delivery of 
 water and head, against which the pump works, but assumes
 
 388 THE STEAM-ENGINE AND THE INDICATOR. 
 
 that the area of the pump piston multipling the average pres- 
 sure or head pumped against measured to level of water in the 
 pumping well (and the pressure due friction), and multiplying 
 the lineal travel of the piston, represents the work done, and this 
 divided by one pound of coal for each hundred burned, represents 
 the duty; or, by formula: 
 
 Where 
 
 A = area of pump piston. 
 
 P = load in pounds pressure per square inch. 
 
 S = stroke of piston in feet. 
 
 C = coal consumed. 
 
 The above method is employed in estimating the duty when 
 the engines pump directly into the mains or into a stand-pipe. 
 When the delivery of water is into a reservoir, the following 
 method is employed : The delivery of water into the reservoir 
 is noted by weir measurement, which is the most exact method; 
 if this is not convenient it is done by calculating the cubic con- 
 tents of reservoir at the commencement and end of trial, or by 
 estimating the theoretical delivery of pumps, and allowing a 
 percentage of leakage, which is determined by experiment in the 
 following manner: The engine is run at so slow a speed that 
 the leakage would be equal to the pumpage, that is, when the 
 ascending main is kept full, but no water enters the reservoir. 
 
 The late Mr. Nystrom suggested a simple way of measuring 
 the water delivered into a reservoir by the use of an instrument 
 constructed upon the same principle as the marine log, only 
 that the propeller is much larger in diameter, and the clock- 
 work geared to indicate feet instead of miles. Nystrom 's log 
 consists principally of a propeller, which is set in rotation by 
 the current of water in which it is immersed. An endless screw, 
 on the end of the propeller shaft, sets the clock-work in motion 
 in the casing, and the number of feet of current passing the 
 propeller represents 10 feet, on the second 100, on the third 
 i,opo and on the fourth 10,000 feet. 
 
 Thus with the four dials, 100,000 feet can be indicated. A 
 sleeve covers the dials when the log is in operation, to prevent
 
 
 MISCELLANEOUS. 389 
 
 solid matter in the water from interfering with the hands and 
 settling in the instrument. 
 
 Two of these instruments were constructed expressly for 
 measuring the water at Fairmount, and other Steam Pumping 
 Works of Philadelphia, by a Commission appointed to measure 
 the duty of the different works, of which Commission the writer 
 had the honor to be a member, and cannot speak too highly of 
 their operation. 
 
 The number on the dials, multiplied by 1. 14, is the space in 
 feet, which multiplied by the area of cross-section in square feet 
 of the current, gives the cubic feet of water that have passed the 
 log. 
 
 When the actual delivery of water is made the basis for 
 estimating the duty, the lift is taken, either by differences of 
 levels of water in pump well and reservoir, or by taking the 
 pressure in the rising main in the pump house, and adding the 
 difference of level between the gage and water in the well; to 
 this is added the allowance for friction, and necessary resistances 
 between gage and well. The delivery is usually reduced to 
 gallons, and the weight of water at mean observed temperature 
 accurately determined. 
 
 /-A -CTT TT 
 
 Duty = X ico. 
 
 G = gallons delivered into reservoir. 
 
 W = weight per gallon. 
 
 H = constant head in feet to which the water is delivered. 
 
 C = coal consumed during trial. 
 
 The following data are from the contract trial of H. R. 
 Worthington, of N. Y., with Belmont Water Works: 
 
 Discharged by weir measurement 11,744,320 
 
 Weight per gallon in pounds 8.38 
 
 Lift, including allowance for friction in feet 217.74 
 
 Coal consumed in pounds 28,890 
 
 Duty = 1 1744.320 X^Sx 217.74 x I00 = 54,4x6,694 
 pounds raised one foot high with 100 pounds of coal.
 
 390 
 
 THE STEAM-ENGINE AND THE INDICATOR. 
 
 Reducing Motion. 
 
 In order that the diagram shall be correct, it is essential 
 
 First. That the motion of the paper drum shall coincide ex- 
 actly with that of the engine piston. 
 
 Second. That the position of the pencil shall precisely indi- 
 cate the pressure of steam in the cylinder. 
 
 The first condition is frequently somewhat difficult to bring 
 about, because it is not only necessary that the beginning and 
 end of motions shall be coincident, but that these and all inter- 
 mediate points shall be so. Owing to the irregular motion of 
 
 FIG. 187. 
 
 the engine piston, consequent upon the varying angularity of 
 the connecting-rod, it is, therefore, generally advisable to con- 
 nect the cord in some way to the piston cross-head. If any 
 other point be chosen, it must be carefully seen that the motion 
 given does not vitiate the diagram. 
 
 As the motion of the parts mentioned exceeds in length the 
 motion of the indicator paper drum, it must be reduced in length 
 by levers of such proportions as may be required for that pur- 
 pose. For example, if the stroke of the engine is forty-eight
 
 MISCELLANEOUS. 
 
 391 
 
 inches, and the length of the diagram is to be four inches, then 
 the lengths of levers are as one is to twelve; or, if only one 
 lever is used, then the indicator motion must be taken from a 
 point on the lever sufficiently far from its fixed end to obtain 
 the reduced travel required. 
 
 One of the simplest ways of reducing the motion is by a 
 swinging lever, with a pin working in a slot of an arm secured 
 to the cross-head of the engine, and transmitting the motion by 
 a cord to the indicator, as shown in Fig. 187. 
 
 FIG. 188. 
 
 I 
 
 The above Fig. 188, also shows a simple plan which can 
 be made of hard wood, or what is known as the "Brumbo" 
 pulley, as illustrated in Fig. 189. 
 
 It is simply a narrow bar of wood, at least one and a half 
 times as long as the stroke of the engine, connected by a link 
 of a convenient length to the cross-head. The cord runs over 
 an arc, the centre of which is the pin on which the bar swings. 
 The radius of the arc necessary to give the desired length of the 
 diagram can be readily found by dividing the length of the bar
 
 392 
 
 THE STEAM-ENGINE AND THE INDICATOR. 
 
 by the stroke and multiplying the quotient by the length of the 
 diagram desired. The product will be the required radius. 
 For example, if the bar is 30 inches long and the stroke 20 
 inches, and we wish to obtain a 3-inch diagram, we have 30 
 inches -- 20 inches = i^\i% X 3 inches = 4^ inches, the 
 radius required to give a diagram 3 inches in length. When 
 the cross-head is in the middle of the stroke, the swinging bar 
 must be in the middle of its path. To prevent errors caused by 
 the angularity of the swinging bar in different positions, the pin 
 
 FIG. 189. 
 
 which connects the end of the bar with the link should be the 
 same distance below the line of motion of the bolt connecting 
 the link with the cross-head when the bar is in its middle posi- 
 tion, as it is above that line of motion when the bar is in its ex- 
 treme positions. 
 
 The Brumbo pulley can be cheaply and quickly made, has 
 but few joints, and can be used on almost any engine. The bar 
 does not have to swing in a vertical plane, but may swing at 
 any angle by using a little ingenuity in connecting the link
 
 MISCELLANEOUS. 393 
 
 with the cross-head. A link made of a thin strip of steel that 
 will bend and twist a little is very convenient. Care must 
 always be taken that, in whatever position the bar may be, the 
 cord will run straight off the arc. When well put up this de- 
 vice is accurate and reliable. Some engines are furnished with 
 a permanent drum motion of this kind, made of steel with nice 
 joints, which, of course, is more satisfactory than any tem- 
 porary arrangement. 
 
 The methods of attaching the various devices to the cross- 
 head are so numerous that it will be impossible to give any 
 rule for universal application. If there are no projections of the 
 engine frame, the device may be attached direct to the cross- 
 head by a bolt tapped in for the purpose, and which will furnish 
 a pivot upon which the device is to act. For the Brumbo 
 pulley and other levers of that stamp, there must be a connect- 
 ing rod between the cross-head and the lever. This may usually 
 be quite short, and attached either directly to the cross-head or 
 to a bar or strap bolted to it. Usually there is some projecting 
 part of the engine, like the rocker stands, portions of the frame 
 or rods, that prevent the parallel motion devices from being di- 
 rectly attached to the cross-head. In such cases each engineer 
 must make his own device. However, there is one method that 
 the writer has most frequently used, that may be of service to 
 others. On an ordinary engine the bolts that are used for ad- 
 justing the cross-head gibs usually have a jamb-nut to hold 
 them in position, and there is, or should be, at least a quarter 
 of an inch between this nut and the head of the bolt. By 
 loosening this nut there will be room to put a bar of quarter- 
 inch iron underneath, and it will be firmly held in position by 
 screwing the nut down upon it. This bar may be made of 
 suitable shape and length to project beyond the frame of the 
 engine, and the device for reducing the motion may be pivoted 
 near the end of the bar instead of the cross-head. 
 
 In making use of any of these contrivances, great care should 
 be taken that there be no lost motion at the joints, and that the 
 parts move easily when connected. 
 
 Most indicators are now made so that the cord may lead off in 
 any direction, and it is unnecessary to have the instrument in a 
 direct line with the reducing motion; but it is absolutely essen-
 
 394 THE STEAM-ENGINE AND THE INDICATOR. 
 
 tial to accuracy that the cord should lead from the parallel or 
 other motion device directly in the line of this motion. To 
 accomplish this, an idle pulley as shown in Fig. 188 is so placed 
 that it receives the cord in a direct line from the device and 
 delivers it to the indicator. This cord should be strong, 
 flexible and inelastic. A hook should be provided on the cord 
 from the indicator and an eye at the proper place on the cord 
 from reducing device, so that the connection may be made 
 easily while the engine is in motion, and disconnected after the 
 cord is taken. Fasten the cord securely to the reducing device 
 and adjust the eye to such a length that when holding it in one 
 hand when the engine is in motion, it will not quite catch the 
 hook on the cord from the paper drum when the drum is at rest, 
 with the least tension on the spring, and so that it will pass 
 beyond the hook when the drum cord is pulled out and the 
 greatest tension is on the spring. Then by pulling this drum 
 cord out as far as possible, the eye may be hooked on very 
 easily and quietly, without jerking the instrument in the 
 slightest. The indicator is now in position and the drum ready 
 to oscillate with the corresponding motion of the piston. 
 
 Engine Tests at Electrical Exhibition, Philadelphia, 1884. 
 Test of Porter-Allen engine : 
 
 Test began, i.io p. m., October 23, 1884. 
 
 Test ended, n.iop. m., October 23, 1884. 
 
 The engines was stopped 2.9 minutes at 6.15 p. m., to change in- 
 dicators. 
 
 Diameter cylinder, n^ inches. 
 
 Stroke, 20 inches. 
 
 Diameter piston rod, i ^ inches. 
 
 Diameter steam pipe, 5 inches. 
 
 Diameter exhaust pipe, 5 inches. 
 
 Area steam ports, 6.75 square inches. 
 
 Area exhaust ports, . . , 10.94 square inches. 
 
 Diameter fly wheel (belt drum), ... 66 inches. 
 
 Face of fly wheel, 15 inches. 
 
 Weight of fly wheel, 1,000 pounds. 
 
 Weight of engine complete, 8,500 pounds. 
 
 Displacement (measured) 
 
 Crank end of cylinder, 2018.3 cubic inches.
 
 ENGINE TESTS AT ELECTRICAL EXHIBITION. 395 
 
 Head end of cylinder, 2070.14 cubic inches. 
 
 Clearance (measured) 
 
 Crank end, 127.87 cubic inches. 
 
 Crank end, 6.33 % displacement. 
 
 Head end, 136.94 cubic inches. 
 
 Head end, 6.61 % displacement. 
 
 Water used in engine, 27849.07 pounds. 
 
 Total time engine in operation, ... 9 hours 57. i min. 
 
 Mean revolutions per minute, .... 227.51 
 
 Maximum revolutions per minute, . . 230. 2 
 
 Minimum revolutions per minute, . . 221.8 
 
 Variation from mean speed, -f 1.18 per cent. 
 
 Variation from mean speed, 2.51 per cent. 
 
 Mean horse-power (indicated) of en- 
 gines, 69.34 
 
 Maximum horse-power (indicated) of 
 
 engines, 76.16 
 
 Minimum horse-power (indicated) of 
 
 engines, 63.16 
 
 Mean temperature of steam at engine, 329.33 
 
 Maximum temperature of steam at en- 
 gine, 338. 
 
 Minimum temperature of steam at en- 
 gine, 306.5 
 
 Mean pressure of steam at engine, . . 90.5 pounds. 
 
 Maximum pressure of steam at engine, 101.6 pounds. 
 
 Minimum pressure of steam at engine, 59.0 pounds. 
 
 Mean pressure of steam at boiler, . . 92.8 pounds. 
 
 Maximum pressure of steam at boiler, 104.3 pounds. 
 
 Minimum pressure of steam at boiler, 61.0 pounds. 
 
 Mean barometer, 30.059 inches. 
 
 Mean temperature of air, 47.4 Fahr. 
 
 Mean power required to run engine 
 
 with load off, 5.16 HP. 
 
 The diagram, Fig. 190, shows the mean of all the indicator 
 cards taken during the test: the clearance line is drawn at each 
 end of diagram, and the theoretical (hyperbola) expansion and 
 compression lines have been drawn. The scale to which the 
 diagrams are drawn is twenty-five pounds to one inch. 
 
 Diagram, Fig. 191, is a reproduction of the card taken at
 
 396 
 
 THE STEAM-ENGINE AND THE INDICATOR. 
 
 8.45 p. m., October 23d, showing 69.38 horse-power. This card 
 represents more nearly the mean horse-power developed than 
 any other that was taken. 
 
 FIG. 190. 
 
 The pressures corresponding to the different parts of the stroke 
 on the mean indicator card, are given in Table 9. The first 
 
 FIG. 191. 
 
 column A shows the points of the stroke. The columns headed 
 B show the pressure in the end of the cylinder away from the
 
 MISCELLANEOUS. 
 
 397 
 
 shaft, while making the stroke towards the shaft and returning; 
 and the column headed C, shows the pressures in the opposite 
 end. The column headed Z>, shows the quantity of dry sat- 
 urated steam used in the cylinder per horse-power per hour from 
 the indicator cards, using the mean number of revolutions and 
 the mean horse-power, and allowing for the amount of steam 
 compressed in the clearance. Re-evaporation after initial con- 
 densation is clearly shown by this: 
 
 The amount of water used by actual weight is 44.307 pounds 
 per horse-power per hour. 
 
 TABLE NO. 9. 
 
 A. 
 
 B. 
 
 C. 
 
 D. 
 
 Part of 
 
 Head End Cylinder. 
 
 Crank End Cylinder. 
 
 Steam Ac- 
 counted 
 
 Stroke. 
 
 Advancing. 
 
 Returning. 
 
 Advancing. 
 
 Returning. 
 
 for in both 
 Ends of 
 Cylinder. 
 
 Beginning. 
 
 86.28 
 
 70.00 
 
 87.82 
 
 81.63 
 
 Clearance, 
 
 
 
 
 
 
 6.3107 pds. 
 
 05 
 
 86.22 
 
 38.00 
 
 87.72 
 
 59-86 
 
 
 .1 
 
 83.88 
 
 20.79 
 
 85-30 
 
 36.42 
 
 
 .2 
 
 69.62 
 
 5-47 
 
 77.10 
 
 II. 12 
 
 
 3 
 
 46.60 
 
 2.0O 
 
 5472 
 
 3-18 
 
 I9.8733 
 
 4 
 
 32.80 
 
 1.64 
 
 39-70 
 
 2.58 
 
 20.0799 
 
 .5 
 
 24.04 
 
 1.40 
 
 30.42 
 
 2.38 
 
 20.3880 
 
 .6 
 
 i8.ii 
 
 1.22 
 
 24.40 
 
 2.40 
 
 20.8786 
 
 7 
 
 14.03 
 
 1.05 
 
 20.18 
 
 2.42 
 
 21.5601 
 
 .8 
 
 10.92 
 
 9 .6 
 
 17.06 
 
 2.63 
 
 22.2940 
 
 9 
 
 8.92 
 
 1. 21 
 
 14.84 
 
 3-18 
 
 23.3827 
 
 95 
 
 6.82 
 
 1. 60 
 
 12.74 
 
 3.36 
 
 
 End. 
 
 1.88 
 
 1.85 
 
 6.82 
 
 432 
 
 
 
 I 
 
 
 
 
 Fig. 192, shows the amount of dry saturated steam which 
 should have been present in the cylinder at the different points 
 of each stroke, together with their sum, the upper line being 
 simply a graphic representation of column Z>, of Table 9. 
 
 Test of the Buckeye Engine. 
 
 Test began, 6 p. m., October 31, 1884. 
 
 Test ended, 4 a. m., November i, 1884. 
 
 Diameter cylinder 10 inches. 
 
 Stroke, 20 inches. 
 
 Diameter piston-rod, i% inches.
 
 THE STEAM-ENGINE AND THE INDICATOR. 
 
 Diameter steam pipe, 3^ inches. 
 
 Diameter exhaust pipe, 4 inches. 
 
 Area steam ports, f x 8^ inches. 
 
 Area exhaust ports, ^x8^ inches. 
 
 Diameter fly wheel, 84 inches. 
 
 Face of fly wheel, 19 inches. 
 
 Weight of fly wheel, 3200 pounds. 
 
 Weight of engine complete, 9800 pounds. 
 
 Displacement (measured), 
 
 Crank end, 1464.48 cubic inches. 
 
 Head end, 1 557. 36 cubic inches. 
 
 FIG. 192. 
 
 Water in Cylinder. (Porter- Allen.) 
 
 Clearance (measured) to face of cut-off, 
 
 Crank end, 47-95 cubic inches. 
 
 Crank end, 3.27 % displacement. 
 
 Head end, 53-57 inches. 
 
 Head end, 3.44 % displacement. 
 
 Water used in engine, 16803.30 pounds. 
 
 Total time engine in operation, ... 10 hours. 
 
 Mean revolutions per minute, , . . . 201.11. 
 
 Maximum revolutions per minute, . . 205.6. 
 
 Minimum revolutions per minute, . . 194.4. 
 
 Variation from mean speed, +2.23 per cent.
 
 MISCELLANEOUS. 
 
 Variation from mean speed, 3.33 per cent. 
 
 Mean indicated horse-power, 54-32 
 
 Maximum indicated horse-power, . . 56.27. 
 
 Minimum indicated horse-power, . . 52.35. 
 
 Mean temperature of steam at engine, . 332.83. 
 
 Maximum temperature of steam at 
 
 engine, 390. 
 
 Minimum temperature of steam at en- 
 gine, 304.5. 
 
 Mean pressure of steam at engine, . . 98.04 pounds. 
 
 Maximum pressure of steam at engine, 107.30 pounds. 
 
 Minimum pressure of steam at engine, 89.80 pounds. 
 
 FIG. 193. 
 
 399 
 
 Mean Card Buckeye Engine. 
 
 Mean barometer, 30.012. 
 
 Mean temperature of air, 46. 
 
 Mean power required to run the engine 
 with the load off, 5.26 H. P. 
 
 Mean Card (Buckeye Engine.) 
 
 Diagram Fig. 193 shows the mean of all the indicator cards 
 taken during the test, the mean being determined as before de- 
 scribed. 
 
 Diagram, Fig. 194, is a reproduction of the cards taken at
 
 400 
 
 THE STEAM-ENGINE AND THE INDICATOR. 
 
 1 1. 20 P. M., October 31, 1884, showing 54.34 horse-power. 
 This card was chosen because it conies more nearly to the mean 
 horse-power than any other that was taken. 
 
 The pressures corresponding to the different parts of the 
 stroke, which would give the mean indicator card, are given in 
 Table 10. 
 
 The first column A shows the point of the stroke, B is the 
 pressure in the end of the cylinder away from the shaft, while 
 the piston is making the stroke towards the shaft and returning. 
 C is the pressure in the opposite end. D is the quantity of dry 
 saturated steam in the cylinder per horse-power per hour from 
 the indicator card, using the mean number of revolutions and 
 
 FIG. 194. 
 
 the mean horse-power, and allowing for the amount of steam, 
 compressed in the clearance. 
 
 Amount of water used by actual weight = ^A- = 30.93 
 
 10 X 54.32 
 pounds. 
 
 Diagram Fig. 195, shows the relative weights of dry saturated 
 steam that should be present (theoretically) in the cylinder at 
 different points of the stroke, together with the amount per 
 horse-power per hour, as shown in Table TO.
 
 MISCELLANEOUS. 
 
 401 
 
 Trial of the Southwark Engine. 
 
 Test began, i p. m., Novembers, 1884. 
 
 Test ended, 12:02 a. m., November 9, 1884. 
 
 TABLE NO. 10. 
 
 A. 
 
 B. 
 
 c 
 
 D. 
 
 Part of 
 
 Head End Cylinder. 
 
 Crank End Cylinder. 
 
 Steam A c- 
 coun ted 
 
 Stroke. 
 
 Advancing. 
 
 Returning. 
 
 Advancing. 
 
 Returning. 
 
 for in Both 
 Ends of 
 Cylinder. 
 
 Beginning. 
 
 90.58 
 
 78.72 
 
 90.95 
 
 76.52 
 
 
 05 
 
 90.49 
 
 21.82 
 
 90-95 
 
 20.34 
 
 
 .1 
 
 89.46 
 
 6.94 
 
 89.86 
 
 6.40 
 
 
 .2 
 
 76.76 
 
 1.79 
 
 80.42 
 
 i-39 
 
 
 3 
 
 49-25 
 
 1.62 
 
 52.94 
 
 1.14 
 
 17.310 
 
 4 
 5 
 
 35-04 
 26.32 
 
 1-50 
 1.38 
 
 37-40 
 28.18 
 
 1.08 
 94 
 
 17-743 
 18.270 
 
 .6 
 
 20.40 
 
 I.OO 
 
 21.64 
 
 .90 
 
 18.713 
 
 7 
 
 16.29 
 
 56 
 
 16.98 
 
 .92 
 
 19.226 
 
 .8 
 
 13.12 
 
 .42 
 
 13.40 
 
 1.04 
 
 19.689 
 
 9 
 
 10.39 
 
 52 
 
 
 1.22 
 
 20.062 
 
 95 
 
 8.28 
 
 .68 
 
 9 26 
 
 1.49 
 
 
 End. 
 
 i-95 
 
 i-95 
 
 3-76 
 
 2.40 
 
 
 FIG. 195. 
 
 HEAD 
 
 Parts of Stroke. 
 Steam in Cylinder. (Buckeye Engine.) 
 
 Diameter cylinder, 
 
 Stroke, 
 
 26 
 
 inches, 
 inches.
 
 4O2 THE STEAM-ENGINE AND THE INDICATOR. 
 
 Diameter piston rod, i^ inches. 
 
 Diameter steam pipe, 3 inches. 
 
 Diameter exhaust, 3^ inches. 
 
 Area steam port, 5.7 square inches. 
 
 Area exhaust port, 5.7 square inches. 
 
 Diameter fly-wheel (belt drum), ... 40 inches. 
 
 Face of fly-wheel, 8^ inches. 
 
 Weight of fly-wheel, 400 pounds. 
 
 Weight of engine, complete, 2,600 pounds. 
 
 Displacement (measured) 
 
 Crank end, 606.03 cubic inches. 
 
 Head end, 633.31 cubic inches. 
 
 Clearance (measured) 
 
 Crank end, 66. i cubic inches. 
 
 Crank end, 10.91 % displacement. 
 
 Head end, 70.42 cubic inches. 
 
 Headend, 11.12 $> displacement. 
 
 Water used in engine, 14792.07 pounds. 
 
 Total time engine in operation, . . . . n hours, 2 minutes. 
 
 Mean revolutions per minute, .... 305.06 
 
 Maximum revolutions per minute, . . 309.87 
 
 Minimum revolutions per minute, . . 301. 
 
 Variation from mean speed, + 1.57 per cent. 
 
 Variation from mean speed, 1.33 per cent. 
 
 Mean horse-power of engine, 29. 1 1 
 
 Maximum horse-power of engine, .. . 46.82 
 
 Minimum horse-power of engine, . . . 14.97 
 
 Mean temperature of steam at engine, . 329. 1 6. 
 
 Maximum temperature of steam at en- 
 gine, 335. 
 
 Minimum temperature of steam at en- 
 gine, 315. 
 
 Mean pressure of steam at engine, . . 87.58 pounds. 
 
 Maximum pressure of steam at engine, 96.0 pounds. 
 
 Minimum pressure of steam at engine, 68.5 pounds. 
 
 Mean pressure of steam at boiler, . . . 92.97 pounds. 
 
 Maximum pressure of steam at boiler, . 101.3 pounds. 
 
 Minimum pressure of steam at boiler, . 73.0 pounds. 
 
 Mean barometer, 30.256 
 
 Mean horse-power delivered, as shown 
 
 by Tatham's dynamometer, .... 23.44 
 
 Maximum horse-power delivered, as 
 
 shown by Tatham's dynamometer, . 43-15
 
 MISCELLANEOUS. 403 
 
 Minimum horse-power delivered, as 
 
 shown by Tatham's dynamometer. . 9.13 
 
 Mean horse-power required to run en- 
 gine with belt off, 4.68 
 
 Diagram, Fig. 196, shows the mean of all the indicator cards 
 taken during the test, the mean being determined as before de- 
 scribed. 
 
 Diagram, Fig. 197, is a reproduction of the cards taken at 
 7:15 P. M., November 8, 1884, showing 29.21 horse-power. 
 This card was chosen, because it comes more nearly to the mean 
 horse-power than any other that was taken during the test. 
 
 FIG. 196. 
 
 LI' 
 
 \ 
 
 \ 
 
 The pressures corresponding to the different parts of the 
 stroke, which would give the mean indicator card, are given in 
 Table n. 
 
 The first column A shows the points of the stroke. B is the 
 pressure in the end of the cylinder away from the shaft, while 
 the piston is making the stroke towards the shaft and returning. 
 C is the pressure in the opposite end. D is the quantity of dry 
 saturated steam in the cylinder per horse-power per hour from 
 the indicator card, using the mean number of revolutions and 
 the mean horse-power, and allowing for the amount of steam 
 compressed in the clearance. 
 
 The amount of water used by actual weight per horse-power 
 per hour = 
 
 H792.Q7 = 4 6. 05 pounds. 
 iiA x 29.11
 
 404 
 
 THE STEAM ENGINE AND THE INDICATOR. 
 
 Diagram Fig. 198 shows the relative weights of dry saturated 
 steam that should be present (theoretically) in the cylinder at 
 
 FIG. 197. 
 
 \ 
 
 \ 
 
 \ 
 
 different points of the stroke, together with the amount for 
 horse-power per hour, as shown in Table n. 
 
 TABLE NO. ii. 
 
 A. 
 
 B. 
 
 c 
 
 D. 
 
 
 Head End Cylinder. 
 
 Crank Eud Cylinder. 
 
 Steam Ac- 
 
 Part of 
 
 
 
 counted 
 
 
 
 
 
 
 for in both 
 
 Stroke. 
 
 Advancing. 
 
 Returning. 
 
 Advancing. 
 
 Returning. 
 
 Ends of 
 Cylinder. 
 
 Beginning. 
 
 86.80 
 
 87.56 
 
 84.99 
 
 67.14 
 
 
 05 
 
 86.08 
 
 66.21 
 
 84.99 
 
 50.55 
 
 
 .1 
 
 .2 
 
 83.90 
 76.69 
 
 47.38 
 25-56 
 
 84.32 
 71-05 
 
 35-02 
 16.92 
 
 
 3 
 
 62.58 
 
 14-25 
 
 52.62 
 
 7.00 
 
 20.781 
 
 4 
 
 47-51 
 
 6.36 
 
 39-40 
 
 2.44 
 
 21.201 
 
 5 
 
 37-97 
 
 2.17 
 
 31.84 
 
 1.36 
 
 22.155 
 
 .6 
 
 32.06 
 
 0.44 
 
 25.60 
 
 1.08 
 
 23.107 
 
 7 
 
 26.75 
 
 0.07 
 
 20.90 
 
 -69 
 
 23-676 
 
 .8 
 
 22.38 
 
 O.I I 
 
 17.08 
 
 .42 
 
 24.045 
 
 9 
 
 18.24 
 
 0.49 
 
 9-74 
 
 58 
 
 
 95 
 
 1 1. 20 
 
 1.46 
 
 3-27 
 
 1.16 
 
 
 End. 
 
 3-47 
 
 2.77 
 
 1.98 
 
 i. 80 
 
 
 The indicated horse-power of the engines were taken with a 
 "Crosby" and a "Tabor" indicator on each cylinder, and a
 
 MISCELLANEOUS. 
 
 405 
 
 Crosby was used on the valve chest. The indicator reducing 
 motions used were practically exact. 
 
 On the Porter-Allen engine test, the indicators were changed 
 when the test was half concluded, and as the cards taken by the 
 two indicators from the same end were as nearly identical as 
 possible, the indicators were not changed during the other tests. 
 
 The indicator springs were tested against a Crosby steam 
 guage, and were found to be practically correct both in ascend- 
 ing and descending. 
 
 FIG. 198. 
 
 Parts of Stroke. 
 Steam in Cylinder. (Southwark Engine.) 
 
 Horse-Power. 
 
 The areas of the cards were taken by a Crosby plani meter. 
 The length of the cards were measured to T ff of an inch. The 
 mean effective pressure was determined from this data. The 
 constant for each end of the cylinder was found by dividing the 
 displacement in cubic inches (found by experiment) by twelve 
 times 33,000. This result, multiplied by the mean effective 
 pressure and by the number of revolutions, gives the horse- 
 power developed in one end of the cylinder. The sum of these 
 results is the total indicated horse-power of the engine.
 
 406 THE STEAM-ENGINE AND THE INDICATOR. 
 
 Mean Indicator Card. 
 
 On each indicator card lines were drawn at right angles to 
 the atmospheric line at the ends of the card, and also at .05, . i, 
 .2 .8, .9, .95, the length of the card. The distance from the 
 atmospheric line to both the top and bottom of the card was 
 measured in TPJT of an inch and tabulated. 
 
 A mean of these tabulated results is taken as the mean in- 
 dicator card from which the amount of water accounted for by 
 the indicator card is calculated. 
 
 Water Accounted for by Indicator Cards. 
 
 In determining the amount of water accounted for on the in- 
 dicator card, the volume of the cylinder to .3, .4, etc., of the 
 stroke, including clearance, has been multiplied by the weight 
 of one cubic foot of steam at the pressure corresponding to that 
 point of the stroke, and from this has been subtracted the vol- 
 ume of the clearance multiplied by the weight of one cubic foot 
 of steam, at the pressure to which the steam has been raised by 
 compression. 
 
 This amount being calculated separately for each end of the 
 cylinder, gives the weight of steam accounted for on the card 
 for each stroke. Adding these results together and multiplying 
 by sixty times the mean number of revolutions per minute, 
 gives the total weight of steam accounted for per hour, and 
 dividing by the mean horse-power, gives the water used per 
 horse- power per hour. // must be remembered that this is on 
 the supposition that the steam in the cylinder was dry and sat- 
 urated. 
 
 As none of the exhibitors made application for a competitive 
 test as prescribed under the code, all tests are quantitative. And 
 the fact that the engines were placed at very different distances 
 from the boiler feeding them, caused the Committee to submit 
 their results without an expression of opinion. 
 
 W. D. MARKS, Chairman, 
 CHAS. E. RONALDSON, 
 WM. BARNET LE VAN, 
 H. W. SPANGLER, Secretary.
 
 MISCELLANEOUS. 
 
 407 
 
 An Approximation to the Effective Mean Pressure. 
 
 The process of finding the mean effective pressure by ordinates 
 or the planimeter requires generally a little time. A simple 
 and quick way of making a close approximation of the mean 
 pressure of a diagram is as follows: 
 
 Draw the line a b, in Fig. 199, touching at , and so that the 
 space d will equal in area the spaces c and e taken together, as 
 nearly as can be estimated by the eye. 
 
 Then measure distance J\ taken at the middle of the diagram ; 
 this distance, measured by the scale of the indicator, will be the 
 mean effective pressure throughout the stroke. 
 
 FIG. 199. 
 
 With a little practice, verifying the results in the usual way, 
 the ability can soon be acquired to make estimates in this way 
 with only a fraction of a pound of error, with diagrams represent- 
 ing some degree of load. With very high initial pressure and 
 early cut-off, it is not so available. 
 
 Of diagram Fig. 9, I have already made a detailed explana- 
 tion, but I wish to call the student's attention to a frequent 
 mistake, namely in measuring on the ordinate lines, the meas- 
 urements should be taken in the centre of the ordinates, or 
 better still erect the ordinates as shown in dotted lines on Fig. 
 19, on page 113. The end spaces should be half the width of 
 the others, as in this example the ordinates stand for the centres 
 of equal spaces.
 
 408 THE STEAM-ENGINE AND THE INDICATOR. 
 
 Ten is the most convenient and usual number of ordinates, 
 though more would give more accurate results. 
 
 Conclusion. 
 
 It is hoped that enough has been said to present a general 
 view of the application and use of the indicator, and before 
 closing, it may be useful to append a few general remarks. 
 
 Rankine, Bourne, Northcott, Graham, Colburn, Salter, 
 Nystrom, and Porter, in their books on the steam-engine and 
 the indicator, discuss a large number of causes which influence 
 the form of the indicator diagram. 
 
 First. The steam pressure undergoes some fall during the 
 passage from the boiler to the cylinder. The amount of such 
 fall varies greatly in different engines; but the general result is, 
 that the highest average indicated steam pressure, before ex- 
 pansion begins, is some two or three pounds less than the boiler 
 pressure. 
 
 The most important points to be noticed are: 
 
 (a) The resistance of the steam-pipe through which the steam 
 passes. 
 
 () The resistance of the throttle-valve. 
 
 (c) The resistance due to the ports and steam passages; and 
 here, also, the bends or sharp angles, as well as the imperfect 
 covering of the steam pipe, must be taken into account. 
 
 All authorities agree that in the present state of our knowl- 
 edge it is impossible to calculate, separately, the losses of pres- 
 sure due to these causes; and, if it were possible, the resulting 
 formulae would be too complicated to be of much use. An ob- 
 servation of this kind has a wide application. It may be 
 pointed out, that steam which has been lowered in pressure by 
 the resistance of passages (or has been wire-drawn, as we have 
 termed it), is, to some extent, superheated by the friction of its 
 molecules, the tendency of all friction being to produce heat. 
 
 Second. There is in practice a rounding of the angle at e see 
 diagrams, Figs. 18, 24, 35, 39, 68 and 90, at which the expan- 
 sion curve begins. This is called wire drawing cut-off. It is 
 always to be seen where the steam valve closes gradually, as in 
 diagram Figs. 169 and 174; but is reduced to a minimum in 
 the improved form of cut-off valves, in general use, such as the
 
 MISCELLANEOUS. 409 
 
 Buckeye, Porter- Allen, and other engines. Speaking generally 
 it may be said that the steam begins, as it were, to work ex- 
 pansively a little before the valve is completely closed, or that 
 the power exerted is nearly the same as if the valve had closed 
 instantaneously at a somewhat earlier point of the stroke, 
 which point may be termed the "effective cut-off." Such a 
 point is easily obtained by carrying the expansion curve a little 
 higher, and by prolonging the probable steam line to meet it. 
 
 Third. The rounding of the expansion curve commences (see 
 diagrams, Figs. 28, 39, 45, 61 and 62 at f to D\ when the ex- 
 haust begins, before the end of the stroke, and it is recommended 
 that the point of exhaust release should be so adjusted that one- 
 half of the fall of pressures shall take place at the end of the 
 forward stroke, and the other half at the beginning of the return 
 stroke (see D d}. Where the release is small, the expansion 
 curve is continued to the end of the diagram (see Fig. 62). 
 
 Fourth. 'The general effect of water in the cylinder, from 
 whatever cause produced, but which we will suppose to be 
 present in some degree throughout the stroke, is to lower the 
 steam line in the first portion of the stroke, and to raise it in 
 the latter portion. 
 
 Fifth. There is also the conduction of heat to or from the 
 walls of the cylinder, the general effect of which is the same as 
 in the last case. 
 
 Sixth. Clearance will modify the form of the expansion 
 curve of steam by removing backwards through a small space 
 the zero line of volumes (see diagrams, Figs. 20, 24, 26 and 57,) 
 and as we have seen, if the steam be completely exhausted from 
 the cylinder during the return stroke, the effect of clearance is 
 to waste a quantity of steam during the double stroke (see dia- 
 grams, Figs. 17 and 21). But inasmuch as it is possible to 
 compress a portion of the exhaust steam in the cylinder during 
 the return stroke (see diagrams, Figs. 9, 18, 24, 28 and 68, and 
 90), the loss above referred to may be greatly reduced, or per- 
 haps wholly eliminated. The best authorities on this subject 
 recommend that the point of compression should be adjusted in 
 such a manner that the quantity of steam confined or cushioned 
 should be just sufficient to fill the clearance spaces with steam, 
 at the initial pressure, when the piston comes to rest. In such
 
 4 10 THE STEAM-ENGINE AND THE INDICATOR. 
 
 a case the work expended in compression is restored again dur- 
 ing expansion, and the steam spring is continually reproduced 
 without waste. 
 
 Seventh. It will be seen by Diagrams Figs. 28, 162, 163, 165, 
 that throttling and wire-drawing are accompanied by direct loss, 
 due to the reduction of the initial pressure which takes place 
 during the process, and by indirect waste, owing to the in- 
 creased proportion of work expended in overcoming the back- 
 pressure. 
 
 Eighth. There is a great necessity for a delicate steam-en- 
 gine indicator, giving continuous diagrams on a roll of paper, 
 similar to the stock-quotation indicators.
 
 APPENDIX. 
 
 The Indicator. 
 
 THE indicator has been of incalculable service in developing 
 the steam-engine up to its present state of perfection, as without 
 it many of the most valuable refinements in engine construction 
 could not have been reached at all. To the erecting mechanic 
 it is now regarded as indispensable in first attaining correct 
 adjustments of valves and regulator, and it is also equally valua- 
 ble to the engineer in charge in maintaining those adjustments. 
 It is thus valuable because its indications are obtained during 
 the regular working of the engine, and directly from the im- 
 pelling pressure, a proper admission and release of which is the 
 prime object, and adjustments thus made are not subject to the 
 uncertain allowances . for expansion and elasticity of parts, 
 which are necessary with the primitive methods. After a most 
 careful adjustment by measurements and allowance for expan- 
 sion and elasticity of parts, the indicator is sure to detect and 
 locate surprisingly small imperfections. 
 
 Every engine should be indicated occasionally, and preferably 
 by the engineer himself, so that he may be well informed as to 
 the condition of its adjustments, which is so liable to be neg- 
 lected in case of unindicated engines. 
 
 The indicator shows only the pressure at each point of the 
 stroke: to represent this faithfully is its sole office. It tells 
 nothing about the causes which have determined the form of the 
 figure which it describes. The engineer concludes what these 
 are, as the result of a process of reasoning, and this is the point 
 where errors are liable to be committed. Conclusions which 
 seem obvious sometimes turn out to have been wrong, and the 
 ability to form an accurate judgment, as to the causes of the 
 peculiarities present in the diagram, is one of the highest at- 
 tainments of an engineer.
 
 412 APPENDIX. 
 
 The variety of diagrams as illustrated in this work from 
 different engines and by some of the same engines under differ- 
 ent circumstances, is endless, and there is perhaps nothing more 
 instructive to the student of engineering, as there is nothing 
 more interesting to the accomplished engineer, than their care- 
 ful and comprehensive study, with a knowledge of the modify- 
 ing circumstances under which each one was taken. Lines 
 which at first appeared meaningless become full of meaning; 
 that, which then, scarcely arrested his attention comes to possess 
 an absorbing interest. He becomes acquainted with the innum- 
 erable variety of vicious forms, and learns the points and degrees 
 as well as the causes of their departure from the single perfect 
 
 FIG. 200. 
 
 Thompson Indicator, Exterior View. 
 
 form ; he becomes familiar with the effects produced by different 
 construction and movements of parts, and competent to judge 
 correctly as to the performance of an engine, and to advise con- 
 cerning changes by which it may be improved. He ceases to be 
 a mere imitator of material shapes, and learns to strive after the 
 highest excellence, and at the same time to comprehend its 
 conditions. No one at the present day can claim to be a 
 mechanical engineer who has not become familiar with the use 
 of the indicator, and skillful in turning to practical advantage 
 the varied information which it furnishes.
 
 INDICATORS. 413 
 
 Indicators in General Use. 
 
 The Thompson Indicator. 
 
 The claims for this indicator (Figs. 200 and 201) are that the 
 parallel motion is the most accurate of any in use in such in- 
 struments, and that errors, said to exist in drawing correct ver- 
 tical lines, do not appear in the limited movement of the pencil 
 in taking diagrams from steam engine and other cylinders with 
 this instrument. 
 
 FIG. 201. 
 
 Thompson Indicator, Sectional View. 
 
 The paper cylinder movement is so constructed that the 
 tension of the coiled drum spring within the paper cylinder can 
 be increased or decreased for different speeds of engine. 
 
 The diameter of the piston is 0.798 inch, equal to one-half 
 inch area. These indicators are fitted with a "detent motion" 
 consisting of a pawl and spring stop, by the use of which the 
 paper drum cylinder can be stopped and a change of cards 
 made, without unhooking or disconnecting the driving cord. 
 
 The advantage of this arrangement is that the cord being 
 entirely free, runs loosely with the motion of the engine, and 
 the paper drum being stationary, cards can be changed without 
 the least disturbance of adjustments. Again it obviates the 
 change of adjustments, and is particularly valuable to amateurs 
 and others not familiar with the use of the indicator.
 
 APPENDIX. 
 
 Tabor Indicator. 
 
 The improvement claimed in this instrument (Figs. 202 and 
 203) is to produce a straight line movement of the pencil. 
 
 A 
 
 FIG. 202. 
 
 Tabor Indicator, Front View of Pencil Mechanism. 
 
 stationary plate containing a curved slot is firmly secured to 
 the cover of the steam cylinder, in an upright position. This 
 
 FIG. 203. 
 
 Tabor Indicator, Sectional View. 
 
 slot serves as a guide and controls the motion of the pencil bar. 
 The side of the pencil bar carries a roller which turns on a pin,
 
 INDICATORS. 415 
 
 and this is fitted so as to roll freely from end to end of the slot 
 with little lost motion. The curve of the slot is so adjusted and 
 the pin attached to such a point, that the end of the pencil bar, 
 which carries the pencil, moves up and down in a straight line 
 when the roller is moved from one end of the slot to the other. 
 The curve of the slot just compensates the tendency of the pencil 
 point to move in a circular arc, and a straight line motion re- 
 sults. The outside of the curve is nearly a true circle with a 
 radius of one inch. 
 
 The improvements above described are shown in Fig. 203. 
 This instrument is also fitted with a "detent motion" as de- 
 scribed in the former indicator. 
 
 The springs used are of the duplex type, being made of two 
 spiral coils of wire. The springs are so mounted that the points 
 of connection of the two coils lie on opposite sides of the con- 
 nections. 
 
 The coupling has but one thread, therefore it is operated by 
 simply turning it in the proper direction. 
 
 The Crosby Steam-Engine Indicator. 
 
 The improvement in this instrument (Figs. 204 and 205) is 
 a short spiral paper drum spring. This form of spring gives, 
 at the beginning of the stroke in one direction, a comparatively 
 slight resistance, which gradually increases until it reaches the 
 maximum at the end of the stroke. In the other direction the 
 strength of the recoil is greatest at the beginning of the stroke, 
 and gradually decreases until the end of the stroke is reached. 
 The levers for the pencil movement are made as light as pos- 
 sible to avoid all errors from momentum. 
 
 Each point is formed by a hardened steel pin running in a 
 hardened steel bearing. The piston is made as light as possible, 
 and is provided with steam chambers in the outer surface, on 
 which the pressure of the steam acts and prevents the piston 
 from touching the sides of the cylinder. The springs are of a 
 imique and ingenious design, which enables the strains to which 
 they are subjected to be transmitted from the centre of the pis- 
 ton. Each spring is made of a single piece of wire wound from 
 the middle into a double coil. This construction gives it all the 
 advantages of a double spring. Every spring is carefully tested
 
 416 
 
 APPENDIX. 
 
 and rated under steam pressure in the indicator, so that it will 
 be accurate when in actual use on the cylinder of the steam- 
 engine. 
 
 Boilers. 
 
 Steam boilers being the source of the motive force to run 
 engines, a passing word ma}' not be amiss in regard to their 
 proper form and construction. The steam-engine as we have 
 
 FIG. 204. 
 
 Crosby Indicator, Exterior View. 
 
 shown has been the subject of constant and unremitting im- 
 provement, ever since its introduction. The "flue" boilei 
 introduced at the beginning of this century, with its internal 
 flues very nearly similar in construction and dimensions to 
 those now in use, has given by far the best results, performing 
 a duty of nearly one hundred million pounds, raised one foot 
 high, with a consumption of less than one hundred pounds of 
 coal, or over one million pounds duty with one pound of coal.
 
 BOILERS. 
 
 417 
 
 This remarkable result was due as much to the boiler as to the 
 
 engine itself. 
 
 High Pressure Steam. 
 
 The demand of to-day is high pressure steam for the improved 
 form of engines. To economically generate high pressure steam 
 is the great problem of the age. 
 
 FIG. 205. 
 
 Crosby Indicator, Sectional View. 
 
 Steel vs. Iron. 
 
 The superiority of steel as compared with wrought iron for 
 boilers has now been so fully proven, and is so widely admitted, 
 that it cannot be understood why boilers are not made exclu- 
 sively from steel. 
 
 The best boilers of to-day have all the horizontal seams double 
 welt butt-joints, triple riveted. Thus the shearing of the rivets 
 must occur in three places; and on this account their resistance 
 27
 
 418 APPENDIX. 
 
 is very nearly twice as great as in other joints. This joint is 
 free from the distortion on account of the oblique action of the 
 stress on the rivets, to which the lap-joints and single-welt butt- 
 joints are subjected. 
 
 These butt-joints distribute the strain at the joint uniformly 
 over the whole section of the metal; whereas, with an ordinary 
 lap-joint the strain is concentrated at the edges of the over- 
 lapping plates. 
 
 The rivet-holes are punched less in diameter than the rivet, 
 and when all the plates are brought well together by temporary 
 bolts, the holes are reamed fair to receive the rivets and counter- 
 sunk slightly, so as to form a fillet to rivet heads. 
 
 All the shell-plates average about 58,000 pounds per square 
 inch tensile strength, with an elongation of thirty to fifty per 
 cent. 
 
 At the present time it is universally admitted that plates made 
 from a metal in a state of fusion, poured into an ingot while 
 fluid, compressed, and then hammered and rolled, are much 
 more likely to be mechanically homogeneous than iron plates 
 made up of a number of pieces welded together by hammering 
 and rolling. 
 
 This is why mild steel plates are preferred in the place of the 
 best iron plates. Steel plates are not only more homogeneous, 
 but are free from lamination and blister, and have more equal 
 tenacity and ductility lengthwise and crosswise, will bear cold 
 flanging and bending in all directions, will also stand drawing 
 like copper or lead, and will stand the most severe cold punching. 
 
 Steel plates have, from experiments made, yielded very much 
 before rupture if the tensile strain is applied fairly over the 
 whole section. 
 
 Punching the holes small in diameter, and reaming them 
 out to rivet size after the boiler is in proper shape, dispenses 
 with the complex strains by the usual mode caused by varying 
 strengths of joints, as well as the improper distribution of the 
 heat. 
 
 Superheated Steam. 
 
 For some time past engineers have abandoned superheating, 
 although its value is well understood, but with the increased 
 steam pressures and greater rates of expansion, all engineers
 
 INCRUSTATION. 419 
 
 who are anxious for the economical performance of their steam 
 engines find it desirable to superheat the steam, the result? 
 being identical with that of the steam-jacket See Figs. 71, 
 72, 73, 74, 75 and 76. 
 
 The advantages to be gained in the use of superheated steam 
 cannot be over-estimated. The use of wet steam augments 
 cylinder condensation, whereas by the use of superheated steam 
 cylinder condensation will be reduced to a minimum, from the 
 fact that the latter conducts heat very slowly. 
 
 Priming or Boiler Disturbance. 
 
 The worst defect a boiler can have is a disposition to prime; 
 in other words, to send water as well as steam to the engine. 
 Whether a boiler primes much or little, the defect is serious. 
 Priming is, in conventional terms, nothing more than a boiling- 
 over. The steam as it is generated, instead of escaping freely 
 from the water, is entangled with it, and carries over in its 
 grasp a certain portion of the fluid, therefore producing wet 
 steam. 
 
 Horizontal Flue Boiler. 
 
 The horizontal flue boiler, with a steam drum connected by 
 a single neck, and having the products of combustion passing 
 all around it, is no doubt the best boiler that can be erected, 
 considering all conditions. At the present time, the desire of 
 the principal boiler-makers is to secure accuracy and solidity of 
 workmanship, which will defy for a long period the continual 
 strain due to the high steam pressures now carried to produce 
 economy in fuel. 
 
 Incrustation of Boilers. 
 
 Every engineer and boiler owner doubtless knows what is con- 
 veyed in the term ^incrii station " of boilers the loss of fuel and 
 damage to the plates, and the risk of explosion and loss con- 
 sequent therefrom, and they know also of the numerous schemes 
 which have been promulgated for its prevention, and the still 
 more numerous schemes brought forward for its cure. To 
 many the term conveys no other idea but that of inconvenience 
 of a certain character not deemed likely to be serious furthei 
 than that it may cause an extra expenditure of fuel no great
 
 420 APPENDIX. 
 
 matter to many in these days of cheap fuel, who care nothing 
 for speculation as to the time when it will not be cheap but 
 this restricted view of incrustation is by no means a correct one. 
 I have no hesitation, indeed, in saying that through incrustation 
 many most serious explosions have taken place, and the risk of 
 many more taking place in future is daily incurred. 
 
 The scale covers the plates, causes them to be overheated, and 
 from the unequal .expansion and contraction to which they are 
 subjected from its presence, the wear and tear of the boiler is 
 much increased; it prevents proper examination of the plates so 
 as to ascertain their condition, and frequently a corrosive action 
 proceeds to a highly dangerous extent under it; and yet its 
 existence is not known, or, if conjectured, cannot be properly 
 ascertained until all the scale is taken off, a matter which 
 involves more trouble and expense than is sometimes thought 
 of, in some cases the scale being so welded, so to speak, to the 
 surface of the plates, that even with the aid of the hammer and 
 chisel, the greatest difficulty is experienced in getting it off. 
 Further and for the present finally water which causes in- 
 crustation in the boiler also causes certain wear and tear to the 
 working parts of the steam-engine which it runs, the earthy 
 matter in it being frequently carried over by the steam, especi- 
 ally where the boiler is "priming" or "foaming" that is, 
 carrying over steam saturated or partly so with water and 
 cutting the valve-faces, piston-rings and the cylinder itself, 
 causing leaks which are plainly shown on steam-engine indi- 
 cator diagrams. From the above it will be seen that very 
 great drawbacks arise from the incrustation of boilers and hence 
 the importance of any mode by which it can be prevented. The 
 most obvious way is, of course, to use good water. It does 
 not imply that the water is good because it may happen to be 
 pure and clean, for what might, compared with pure water, be 
 called almost a dirty one, may, and often does, yield less deposit. 
 The carbonate of lime, if present in water, yields a soft deposit 
 or loose powder, which may be and in practice is got rid of by 
 the process of "blowing out," that is, allowing a certain quantity 
 of the contents of the boiler to be blown out of or through a 
 cock and pipe placed at the lowest part of the boiler for that 
 purpose. If the water contains a sulphate of lime, the deposit
 
 BOILER POWER. 42 1 
 
 is formed as a hard crust, cake or scale, and if both the carbonate 
 and the sulphate of lime are present in the water used for boiler 
 purposes, then a crust is formed more or less dense or hard in 
 proportion to the percentage of the carbonate or the sulphate 
 present. It is not always, indeed not often, that a choice of 
 waters is presented to the users of steam power; but where it is, 
 it is assuredly the wisest plan to have them analyzed, so that the 
 best amongst them may be taken. 
 
 But when one kind of water only is available (such as is the 
 case of towns and cities) and that kind bad, the next plan open 
 to the users of steam-power is to employ a mode of preventing 
 the scale or deposit; and here the difficulty comes in play, how 
 to choose amongst so many plans. 
 
 The acids which cause "pitting "' "channeling," "furrow- 
 ing," "grooving," etc., held in solution in the water fed to the 
 boiler and set free by heat, are beyond the reach of any mechan- 
 ical devices, and can only be neutralized by a chemical combi- 
 nation, which is known to the trade as boiler solvents. 
 
 Boiler incrustation remedies are exceedingly numerous; and 
 so few out of the many are thoroughly good, that it is not the 
 embarrassment of riches, as the French say, but that of poverty, 
 which is the puzzle to those who are choosing. 
 
 The boiler compound of George W. Lord, of Philadelphia, 
 Pa., has a high reputation as a scale preventer and acid neutral- 
 izer, and is recommended by a large number of manufacturers 
 and others using it. 
 
 Messrs. Booth & Garrett, chemists, of Philadelphia, who stand 
 at the head of their profession, make the statement over their 
 signature that "it is free from any substance that could prove 
 injurious to the boiler." 
 
 The advantage of Lord's compound is that it is in the form 
 of a dry granulated powder. It readily dissolves in water, and 
 can therefore be applied in a dry state through the man-hole, 
 or in a liquid state by the feed-pump. 
 
 The quantity introduced will depend upon the nature and 
 amount of water evaporated, as well as the amount of scale at- 
 tached, also upon the construction of the boilers, etc.
 
 422 APPENDIX. 
 
 Power of a Boiler. 
 
 The steaming capacity or power of a boiler is usually ex- 
 pressed in horse-power, as with the engine itself, and the horse- 
 power is taken to be equal to the evaporation of thirty (30) 
 pounds of water at and from 212 degrees. 
 
 Thirty pounds of water converted into steam, although a 
 convenient unit of measurement so far as the boiler is concerned, 
 does not indicate the power of the engine. The best modern 
 engines exert an indicated horse-power per hour with less than 
 twenty (20) pounds of water, whereas some engines largely sold 
 have been found to use over sixty (60) pounds per hour per 
 horse-power. 
 
 Square feet of heating surface is no criterion as between dif- 
 ferent styles of boilers a square foot under some circumstances 
 being many times as efficient as in others. In the tests at the 
 Brush Electric Light Company, at Philadelphia, the horizontal- 
 flue boilers developed a horse-power for each 9.4 square feet of 
 heating surface, whereas the water-tube boilers required 14.1 
 square feet, a difference of 33 per cent. ; or, in other words, the 
 water-tube boilers require 33 per cent, more heating surface to 
 develop the same power that the horizontal-flue boilers require. 
 
 Fahrenheit, and Centigrade Thermometers. 
 The Reaumur thermometer is gradually being abolished, and 
 now used only in Peru. 
 
 Fahrenheit in Centigrade in 
 
 Degrees. Degrees. 
 
 Boiling point of water means atmo- ~\ 
 
 spheric pressure 01.14.7 pounds > 212 100 
 
 per square inch. j 
 
 Melting point of ice under atmo- ) 
 spheric pressure. j 3 2 
 
 To convert any number of degrees Fahrenheit into degrees 
 Centigrade, or vice versa : 
 
 Degrees Fahrenheit 32x1= degrees of Centigrade. 
 Degrees Centigrade x f + 32 degrees of Fahrenheit. 
 
 Falling Bodies. 
 
 The following formulae apply to bodies acted upon by gravity 
 
 in vacuo. Although near enough for almost all practical pur-
 
 FALLING BODIES. 423 
 
 poses to be exact, the formula should vary with the latitude 
 and elevation. 
 
 In vacuum a heavy body does not fall faster than a light one, 
 because the weight of each body is equal to the force of gravity 
 acting upon it; but when a body falls in air or liquid, its force 
 of gravity is diminished by an amount equal to the weight of 
 the air or liquid displaced by the body, and whilst the mass is 
 constant, a smaller force has a heavier body to move, and the 
 body will fall slower. A pound of lead displaces less weight of 
 air than does a pound of cork, for which reason the lead will 
 fall faster than the cork in air. 
 
 The force of gravity must also overcome the resistance of the 
 air to the motion of the falling body, which is independent of 
 the weight of air the body displaces. This resistance increases 
 as the square of the velocity and as the surface exposed to the 
 motion. A pound of cork exposes more surface to the motion 
 than does a pound of lead, for which reason the cork falls more 
 slowly. 
 
 ,5* = space in feet. 
 
 V=. velocity in feet per second. 
 
 T= time in seconds of the fall. 
 
 g = 32* a constant representing gravity. 
 
 First. The height or vertical distance through which a body 
 will fall in a given time is: 
 
 Space 5 = . 
 Second. The velocity acquired at the end of a given time: 
 
 Velocity V = gT 
 Third. The velocity due to a given space of fall: 
 
 Velocity V= 8.025 V~S 
 
 Fourth. The space of fall due to a given velocity is: 
 Space 5* =
 
 424 APPENDIX. 
 
 Fifth. The time of fall from a given space: 
 
 ,- Time T V 
 
 g 
 
 Example: A body is dropped from a height of S = 100; re- 
 quired the time of fall, and with what velocity it reaches the 
 ground? 
 
 Formula 5: 
 
 = V 
 
 2XIOO 
 32.17 
 
 = 7 .8 seconds.
 
 APPENDIX. 
 
 425 
 
 HORSE-POWER CONSTANTS FOR SINGLE CYLINDER ENGINES. 
 TABLE NO. 12. 
 
 Effective Horse-Power per Iiidicator exerted for each Pound Average 
 Pressure upon the pistons of engines, varying in diameter from 4 to 60 
 inches, when moving with a speed in feet corresponding with the fig- 
 ures at the head of the several columns. Calculated as explained on 
 pages 103 and 104. 
 
 DlAMB- 
 
 CTLDI- 
 
 DU. 
 
 Inched 
 
 ! 
 
 5 
 5| 
 
 Speed of Piston in Feet per Minute. 
 
 240 
 
 300 
 
 350 
 
 400 
 
 450 
 
 500 
 
 550 
 
 600 
 
 65O 
 
 750 
 
 0.091 
 0.115 
 0.144 
 0.173 
 
 0.114 
 0.144 
 0.180 
 0.216 
 
 0-133 
 o.i 68 
 
 O.2IO 
 0.252 
 
 0.152 
 0.192 
 0.240 
 0.288 
 
 0.171 
 0.216 
 0.270 
 0.324 
 
 0.385 
 0.461 
 0.524 
 0.602 
 
 0.190 
 0.240 
 0.300 
 0.360 
 
 0.209 
 0.264 
 
 0.330 
 0.396 
 
 0.228 
 0.288 
 0.360 
 0.432 
 
 0.247 
 0.312 
 0.390 
 0.468 
 
 0.285 
 0.360 
 0.450 
 0.540 
 
 6 
 6J 
 
 Ji_ 
 8 
 8^ 
 9 
 _9i. 
 10 
 
 I0| 
 
 II 
 
 Eli 
 
 0.205 
 0.245 
 0.279 
 0.321 
 
 0.256 
 0.307 
 0.348 
 0.401 
 
 0.299 
 0.391 
 0.408 
 0.468 
 
 0.342 
 0.409 
 0.466 
 0-534 
 
 0.428 
 0.512 
 0.583 
 0.669 
 
 0.471 
 0.563 
 
 0.641 
 
 0.735 
 
 0-513 
 0.614 
 0.699 
 0.802 
 
 0-555 
 0.698 
 0-756 
 0.869 
 
 0.641 
 0.800 
 0.874 
 i. 002 
 
 0.365 
 0.413 
 0.462 
 0.515 
 
 0.456 
 0.516 
 0-577 
 0.644 
 
 0.532 
 0.602 
 0.674 
 0.751 
 
 0.608 
 0.688 
 0.770 
 0.859 
 
 0.685 
 0.774 
 0.866 
 0.966 
 
 0.761 
 0.860 
 0.963 
 1.074 
 
 0.837 
 0.946 
 1.059 
 
 1.181 
 
 0.912 
 1-032 
 154 
 .288 
 
 ^428 
 575 
 
 0.989 
 .118 
 251 
 _^95 
 
 547 
 .706 
 .872 
 2.043 
 
 .121 
 .29 
 
 -444 
 .610 
 
 o.57i 
 0.630 
 0.691 
 0-754 
 
 0.714 
 0.787 
 0.864 
 0-943 
 
 0-833 
 0.919 
 I.OOS 
 I.IOO 
 
 0.952 
 1.050 
 1.152 
 1-257 
 
 1.071 
 .181 
 .296 
 .414 
 
 1.190 
 
 I.3I3 
 1.440 
 1-572 
 
 1.309 
 1.444 
 
 1.584 
 
 1.729 
 
 .785 
 969 
 .160 
 2-357 
 
 12 
 13 
 14 
 15 
 
 0.820 
 0.964 
 1.119 
 1.285 
 
 1.025 
 1.206 
 I.398 
 i. 606 
 
 1-195 
 1.407 
 1.631 
 
 1.873 
 
 1.366 
 i. 608 
 1.864 
 2-131 
 2.436 
 2-739 
 3-083 
 3-436 
 
 540 
 .809 
 2.097 
 2.404 
 
 1.708 
 
 2.OIO 
 
 2.331 
 2.677 
 
 1.880 
 
 2.211 
 
 2.564 
 2-945 
 
 2.050 
 2.412 
 2.797 
 3.112 
 
 2.222 
 2.613 
 3.029 
 
 3-479 
 
 2.564 
 3-oi5 
 3-495 
 4.004 
 
 16 
 
 17 
 18 
 
 19 
 
 20 
 21 
 22 
 
 23 
 24 
 
 $ 
 
 27 
 
 1.461 
 1.643 
 1.849 
 2.064 
 
 1.827 
 2.054 
 2.312 
 2-577 
 
 2.131 
 2.396 
 2.697 
 3.006 
 
 2.741 
 3.081 
 3.468 
 3-865 
 
 3-045 
 3-424 
 3-854 
 4-295 
 
 3-349 
 3.766 
 4-239 
 4-724 
 
 3-654 
 4.108 
 4.624 
 5-154 
 
 3-958 
 4-450 
 5.009 
 5.583 
 6.186 
 6.820 
 7.486 
 8.181 
 8.908 
 9.566 
 10.456 
 11.265 
 
 4.567 
 
 5.78o 
 6.442 
 
 2.292 
 
 2.518 
 2.764 
 3-021 
 
 2.855 
 3.148 
 3-455 
 3-776 
 
 3.331 
 3.672 
 4.031 
 
 4.405 
 
 3.807 
 4-197 
 4.607 
 5-035 
 
 4-285 
 4.722 
 5-183 
 5.664 
 
 4-759 
 5-247 
 5-759 
 6.294 
 
 6.853 
 7.436 
 8.044 
 8.666 
 
 5-234 
 5-771 
 6-334 
 6.923 
 
 5-731 
 6.296 
 6.911 
 7-552 
 
 7.138 
 7.869 
 8.638 
 9.440 
 
 3.289 
 3.569 
 3.861 
 4.159 
 
 4.111 
 4.461 
 4.826 
 5-199 
 
 4-797 
 5-105 
 5-630 
 6.066 
 
 5.482 
 5.948 
 6-435 
 6.932 
 
 6.167 
 6.692 
 7-239 
 7-799 
 
 7-538 
 8.179 
 8.848 
 9-532 
 
 8.223 
 8.923 
 9-652 
 10.399 
 
 10.279 
 
 11-053 
 12.065 
 12.998 
 
 28 
 29 
 3 
 
 V 
 
 32 
 
 33 
 34 
 35 
 
 4-477 
 4-805 
 S.MI 
 5-486 
 
 5-596 
 6.006 
 6.426 
 6.865 
 
 6.529 
 7.007 
 
 7-497 
 8.001 
 
 7.462 
 8.008 
 8.568 
 9.148 
 
 8-395 
 9.009 
 
 9-639 
 10.287 
 
 9.328 
 
 10.010 
 
 10.710 
 
 11.43. 
 
 12.180 
 
 12.959 
 13.730 
 14.570 
 
 10.261 
 
 II. Oil 
 
 11.781 
 12-573 
 I3-398 
 14-245 
 15-103 
 16.027 
 
 H.I93 
 
 I2.OI2 
 12.852 
 I3.7I6 
 I4.6l6 
 I5.540 
 16.476 
 17.484 
 
 12.125 
 13-013 
 13-923 
 14.866 
 
 I3.99I 
 15-015 
 16.065 
 I7-I45 
 
 5-846 
 6.216 
 6.590 
 6-993 
 
 7-308 
 7.770 
 8.238 
 8.742 
 
 8.526 
 9.065 
 9.611 
 10.199 
 10.794 
 11.403 
 12.026 
 12.670 
 
 9-744 
 10.360 
 10.984 
 11.656 
 
 10.962 
 H.655 
 12-357 
 i3-"3 
 
 I5.834 
 16.835 
 17-849 
 18.941 
 
 18.270 
 19425 
 20.595 
 
 36 
 37 
 38 
 39 
 
 7.401 
 7-819 
 8.246 
 8.648 
 
 9.252 
 
 9-774 
 10.308 
 10.86 
 
 12.336 13.878 15.420 
 13.032 ,14.861 16.290 
 13.744 15.462:17.180 
 14.480 16.290 18.100 
 
 16.962 
 17.919 
 18.898 
 19.910 
 
 18.504 
 I9-548 
 20.6l6 
 21.620 
 
 20.046 
 
 21.177 
 22-334 
 23-530 
 
 23- 13 
 
 24-435 
 25.770 
 27.15
 
 426 
 
 APPENDIX. 
 TABI.E No. 12 Continued. 
 
 DIAMI- 
 
 OF 
 
 CYLIH- 
 
 IM^. 
 40 
 41 
 42 
 
 J_ 
 44 
 45 
 46 
 47 
 48 
 49 
 50 
 5i 
 
 Speed of Piston in Feet per Minute. 
 
 240 
 
 300 
 
 350 : 400 450 
 
 500 
 
 550 
 
 600 
 
 650 
 
 750 
 
 9-139 
 9.604 
 10.065 
 10.560 
 
 11.424 
 12.006 
 12-594 
 13.200 
 
 13.818 
 14-454 
 15.128 
 15-768 
 
 13-328 
 
 14.007 
 
 14-693 
 15.400 
 
 15.232 
 16.008 
 16.792 
 
 17.600 
 
 17.136 
 
 18.009 
 18.901 
 19.800 
 
 19.040 
 20.000 
 20.990 
 22.000 
 
 20.944 
 
 22.011 
 23.089 
 24.200 
 
 22.848 
 24.012 
 25.188 
 26.400 
 
 24-752 
 26.013 
 27.287 
 28.600 
 
 28.560 
 30-015 
 31-485 
 33-ooo 
 
 11.046 
 "563 
 12.086 
 12.614 
 
 16.121 
 
 16.863 
 17.626 
 18.396 
 
 18.424 
 19.272 
 20.144 
 21.024 
 
 20.727 
 
 21.681 
 22.662 
 23.652 
 
 23.030 
 24.090 
 25.180 
 26.280 
 
 25-333 
 26.399 
 27.6 9 8 
 28.908 
 
 27.636 
 28.908 
 30.216 
 3L536 
 
 29-939 
 3I-3I7 
 32.754 
 34.164 
 
 34-545 
 36.135 
 37.770 
 39.420 
 
 12.846 
 12.913 
 14.280 
 14.832 
 
 16.446 
 
 17.142 
 17.850 
 18.540 
 
 19.187 
 19.999 
 20.825 
 
 21.665 
 
 21.928 
 
 22.856 
 23.800 
 24.760 
 
 24.669 
 
 25.713 
 26.775 
 27.855 
 
 27.410 
 28.570 
 29.750 
 30.950 
 
 30.151 
 
 3L427 
 32.725 
 34-045 
 
 32.152 35.633 
 34.284 37.141 
 SS.? 00 38.675 
 37.080 J40. 205 
 
 41.115 
 42.855 
 44.625 
 46.425 
 
 52 
 53 
 54 
 55 
 56 
 57 
 58 
 59 
 60 
 
 15-437 
 16.041 
 16.656 
 I7-275 
 
 19.296 
 20.052 
 20.820 
 21-594 
 
 22.512 
 23.394 
 24.290 
 
 25.193 
 
 25.728 
 
 26.736 
 27.760 
 28.792 
 
 28.944 
 30.078 
 
 31.230 
 32.391 
 
 32. 160 
 33-420 
 34.700 
 35-990 
 
 35.376 
 36.762 
 38.170 
 39-589 
 
 38.592 
 40. 104 
 41.640 
 43-188 
 
 41.808 
 43.446 
 45-Uo 
 46.787 
 
 48.240 
 50.130 
 52-050 
 53.985 
 
 17.909 
 18.557 
 19.214 
 19.902 
 20.558 
 
 22.386 
 23.196 
 24.018 
 24-852 
 25.698 
 
 26.117 
 27.062 
 28.021 
 
 28.994 
 29.981 
 
 29.848 
 30.928 
 32.024 
 33.136 
 34.264 
 
 33-579 
 34-794 
 36.027 
 37.278 
 38-547 
 
 37-310 
 38.660 
 40.030 
 41.420 
 42.83 
 
 41.041 
 42.526 
 44-033 
 45.562 
 47-113 
 
 44.772 48.503 
 46.392 50.258 
 48.036 152.039 
 49.704 53-846 
 51.396 S55.679 
 
 55.965 
 57-990 
 60.045 
 62.130 
 64.245 
 
 Horse-Power Constants. 
 
 The above table, No. 12, gives the horse-power constants for 
 engine cylinders from 4 inch to 60 inches, at speeds of 240, 350, 
 400, 450, 500, 550, 600, 650 and 750 feet of piston travel per 
 minute. 
 
 This constant is the number of horse-powers which would 
 be exerted by one pound of mean pressure; this being multiplied 
 by the mean pressure as calculated from the indicator diagram 
 will give the number of horse-powers developed. 
 
 Table, No. 12, does not take into account the area of the 
 piston rod, as there is no standard for diameter of piston rods 
 accepted by engine builders; but the table is near enough cor- 
 rect where great accuracy is not called for. 
 
 In case of great accuracy, knowing the piston's area, we take 
 the area from tabte 13, page 427; from this is to be deducted one- 
 half the area of the rod, the remainder is the average area of the 
 two faces of the piston. We multiply this by the mean pres- 
 sure on the square inch, and the product is the total constant 
 force under which the piston is moving, or which is acting
 
 HORSE-POWER CONSTANTS. 427 
 
 through the distance traveled by the piston. This being mul- 
 tiplied into the distance, in feet, through which the piston 
 travels, or through which the force acts, in one minute, gives 
 the foot-pounds of power developed, or of work done, in that 
 time, and this sum, divided by 33,000, gives the number of 
 horse-powers developed. 
 
 It is interesting to consider the variety of the conditions out 
 of which this result is derived. We have, first, every variation 
 of pressure, from the highest to the lowest; and second, in com- 
 bination with this, every different speed of piston, from infi- 
 nitely slow up to the velocity of the crank. The latter varia- 
 tion is not regarded. Forces different in amount are separate 
 forces. The diagram tells us what each separate force was, and 
 through what distance it acted; and this is all we require for 
 the computation of power. Each force being multiplied into 
 the distance through which it acted, and the product divided 
 by the length of the cylinder in units of such distance, the sum 
 of all is the pounds of force acting through the length of the 
 stroke. That some forces were exerted for a longer time than 
 others, in acting through an equal distance, is nothing. Static 
 forces, though exerted forever, have no dynamical value. 
 Force acquires this value only as it acts through distance. 
 
 Therefore the better method of computing power is, first, to 
 obtain for any engine a constant, which, being multiplied by 
 the mean pressure, will give the horse-power developed. This 
 constant is the number of horse-powers which would be devel- 
 oped by one pound mean pressure. 
 
 An illustration of this will be found on pages 103 and 104, Fig. 
 ii. The different velocities of piston given in the foregoing 
 table embrace those most in general use. In case of the power of 
 an engine having a speed not stated, it may be found by adding 
 together the numbers opposite to the diameter of piston, in any 
 two of the columns that will equal the desired speed, or by ad- 
 ding to the one such portion of another as would make it. Thus, 
 if a number is sought for a speed of 200 feet per minute, it is 
 found by dividing the number under 400 by two; or if 1000 feet 
 is wanted, it will be found by multiplying the appropriate num- 
 ber under 500 feet per minute by two.
 
 428 
 
 APPENDIX. 
 TABLE NO. 13. 
 
 : 
 
 Areas and Circumferences of Circles from ^ to 4 inches in diameter 
 
 varying by sixteenths; and from 4 inches to 100 inches diameter vary- 
 
 ing by one-eighth inch. 
 
 Diam. 
 
 Area 
 
 Circum. 
 
 Diam. 
 
 Area 
 
 Circum. 
 
 Diam. 
 
 Area 
 
 Circum. 
 
 in 
 
 in Square 
 
 in 
 
 
 in Square 
 
 
 in 
 
 in Square 
 
 in 
 
 Inches. 
 
 Inches. 
 
 Inches. 
 
 Inches. 
 
 Inches. 
 
 Inches. 
 
 Inches 
 
 Inches. 
 
 Inches. 
 
 ^T 
 
 O.OOOig 
 
 0.0490 
 
 3-A 
 
 7.3662 
 
 9.6211 
 
 8-f 
 
 55-088 
 
 26.31 
 
 S 
 
 0.00076 
 
 0.0951 
 
 i 
 
 7.6699 
 
 9-8175 
 
 i 
 
 56.745 
 
 26.70 
 
 A 
 
 0.00306 
 
 0.1963 
 
 
 7.9798 
 
 10.0138 
 
 i 
 
 58.426 
 
 27.10 
 
 1 
 
 0.0122 
 
 0.0276 
 
 0.3927 
 0.5890 
 
 i 
 
 8.2957 
 8.6179 
 
 I0.2IO2 
 10.4065 
 
 ;| 
 
 60.132 
 61.862 
 
 27.49 
 27-88 
 
 1 
 
 0.0490 
 
 0.7854 
 
 I* 1 
 
 8.9462 
 
 10.6029 
 
 9- 
 
 63.617 
 
 28.27 
 
 A 
 
 0.0767 
 
 0.9817 
 
 Tff 
 
 9.2806 
 
 10.7992 
 
 .J 
 
 65.396 
 
 28.66 
 
 1 
 
 0.1104 
 
 .1781 
 
 
 9.6211 
 
 10.9956 
 
 
 
 67.200 
 
 29.06 
 
 J 
 
 0.1503 
 0.1963 
 
 3744 
 .5708 
 
 1 
 
 9.9678 
 10.3210 
 
 II.I9I9 
 
 11.3883 
 
 
 
 69.029 
 
 70.882 
 
 29-45 
 29-85 
 
 
 9 ,j 
 
 0.2485 
 
 .7671 
 
 . 
 
 10.6796 
 
 11.5846 
 
 
 
 72.759 
 
 30.24 
 
 
 
 0.3067 
 
 .9630 
 
 -f 
 
 10.9446 
 
 II.78IO 
 
 
 
 74.662 
 
 30.63 
 
 
 i 
 
 0.3712 
 
 2.1590 
 
 II 
 
 II4I59 
 
 11.9773 
 
 
 
 76.588 
 
 31.02 
 
 
 
 0.4417 
 
 2.3565 
 
 
 11.7932 
 
 12.1737 
 
 10. 
 
 78.540 
 
 31.42 
 
 
 i 
 
 0.5174 
 
 2.5512 
 
 If 
 
 12.1768 
 
 12.3700 
 
 .* 
 
 80.515 
 
 31.81 
 
 
 
 0.6013 
 
 2.7490 
 
 4- 
 
 12.566 
 
 12-57 
 
 
 
 82.516 
 
 32.20 
 
 
 f 
 
 0.6902 
 
 2-9453 
 
 
 I3.364 
 
 12.96 
 
 
 
 84.540 
 
 32-59 
 
 i. 
 
 0.7854 
 
 3.1416 
 
 _-L 
 
 14.186 
 
 I 3-35 
 
 
 
 86.590 
 
 
 A 
 
 0.8861 
 
 3-3379 
 
 t 
 
 I5.033 
 
 13-74 
 
 
 
 88.664 
 
 33'38 
 
 .* 
 
 0.9940 
 
 3-5343 
 
 J 
 
 .15.904 
 
 14.14 
 
 
 
 90.762 
 
 33-77 
 
 A 
 
 1.1075 
 
 3-7306 
 
 1 
 
 16.800 
 
 14-53 
 
 1 
 
 92.885 
 
 34.16 
 
 .4 
 
 1.2271 
 
 3.9270 
 
 s 
 
 17.720 
 
 14.92 
 
 ii. 
 
 95-033 
 
 34-56 
 
 A 
 
 L3529 
 
 4-1233 
 
 8 
 
 18.665 
 
 15-32 
 
 
 97.205 
 
 34-95 
 
 1 
 
 1.4848 
 
 4.3197 
 
 5- 
 
 19-635 
 
 15-71 
 
 
 99.402 
 
 35-34 
 
 A 
 
 1.6229 
 
 4-5160 
 
 
 20.629 
 
 16.10 
 
 
 101.62 
 
 35-74 
 
 1 
 
 1.7671 
 
 4.7124 
 
 .1 
 
 21.648 
 
 16.49 
 
 
 103.87 
 
 36-13 
 
 A 
 
 L9I75 
 
 4.9087 
 
 1 
 
 22.690 
 
 16.89 
 
 
 106.14 
 
 36-52 
 
 
 
 2.0739 
 
 5-1051 
 
 .A 
 
 23.758 
 
 17.28 
 
 
 108.43 
 
 36.91 
 
 
 J 
 
 2.2365 
 
 5-3014 
 
 8 
 
 24.850 
 
 17.67 
 
 
 110.75 
 
 37-31 
 
 
 
 2.4052 
 
 54978 
 
 Z 
 
 25.967 
 
 1 8. 06 
 
 12. 
 
 113.10 
 
 37-70 
 
 
 | 
 
 2.5801 
 
 5-6941 
 
 1 
 
 27.108 
 
 18.46 
 
 
 
 H5-47 
 
 38.09 
 
 
 
 2.7611 
 
 5-8905 
 
 6. 
 
 28.274 
 
 18.85 
 
 
 
 117.86 
 
 38.48 
 
 
 i 
 
 2.9483 
 
 6.0868 
 
 & 
 
 29.464 
 
 19.24 
 
 
 
 120.28 
 
 38.88 
 
 2. 
 
 3.1416 
 
 6.2832 
 
 .^ 
 
 30.680 
 
 19-64 
 
 
 
 122.72 
 
 39-27 
 
 A 
 
 3-34H 
 
 6-4795 
 
 f 
 
 31.919 
 
 20.03 
 
 
 
 125.18 
 
 39-66 
 
 . 
 
 3-5468 
 
 6-6759 
 
 1 
 
 33.183 
 
 20.42 
 
 
 
 127.68 
 
 40.06 
 
 A 
 
 
 6.8722 
 
 
 34-47 1 
 
 20.81 
 
 
 
 130.19 
 
 40-45 
 
 'f 
 
 3.9760 
 
 7.0686 
 
 
 35.785 
 
 21.21 
 
 13- 
 
 
 132.73 
 
 40.84 
 
 A 
 
 4.2001 
 
 7.2649 
 
 
 37.122 
 
 21. 6O 
 
 
 
 135-30 
 
 41-23 
 
 1 
 
 4.4302 
 
 7.4618 
 
 7- 
 
 38.484 
 
 21-99 
 
 
 
 137.89 
 
 41.63 
 
 A 
 
 4.6664 
 
 7.6576 
 
 
 39-87I 
 
 22.38 
 
 
 
 140.50 
 
 42.02 
 
 4 
 
 4-9087 
 
 7.8540 
 
 
 41.282 
 
 22.78 
 
 
 
 I43-I4 
 
 42.41 
 
 -A 
 
 5-1573 
 
 8.0503 
 
 
 42.718 
 
 23.17 
 
 
 
 14580 
 
 42.80 
 
 
 
 5-4I19 
 
 8.2467 
 
 
 44.179 
 
 
 .j 
 
 
 148.49 
 
 43-20 
 
 .- 
 
 I 
 
 
 8.4430 
 
 
 45-663 
 
 23-95 
 
 ,| 
 
 
 151.20 
 
 43-59 
 
 ! 
 
 f 
 
 5-9395 
 6.2126 
 
 8.6394 
 8.8357 
 
 
 47-173 
 48.707 
 
 24-35 
 24.74 
 
 14. 
 
 153-94 
 156.70 
 
 43.98 
 44.38 
 
 
 
 6.4918 
 
 9.0321 
 
 8. 
 
 50-265 
 
 25.13 
 
 .A 
 
 I59-48 
 
 44-77 
 
 
 5 
 
 i 
 
 6.7772 
 
 9.2284 
 
 1 
 
 51.848 
 
 25-52 
 
 i 
 
 162.29 
 
 45.16 
 
 3- 
 
 7.0686 
 
 9.4248 
 
 4 
 
 53-456 
 
 25.92 
 
 * 
 
 165.13 
 
 45-55
 
 AREAS AND CIRCUMFERENCES OF CIRCLES. 
 
 429 
 
 TABLE No. 13 Continued. 
 
 Diam. 
 in 
 
 Inches. 
 
 Area 
 in Square 
 Inches. 
 
 Circum. 
 in 
 Inches. 
 
 Diam. 
 in 
 Inches. 
 
 Area 
 in Square 
 Inches. 
 
 Circum. 
 Inches. 
 
 Diam. 
 in 
 Inches. 
 
 Area 
 in Square 
 Inches. 
 
 Circum. 
 in 
 Inches. 
 
 14- 1 
 
 167.99 
 
 45-95 
 
 21. | 
 
 358.8 4 
 
 67-I5 
 
 28.^ 
 
 621.26 
 
 88.36 
 
 I 
 
 170.87 
 
 46-34 
 
 \ 
 
 363-05 
 
 67-54 
 
 .J 
 
 626.80 
 
 88.75 
 
 t 
 
 173.78 
 
 46.73 
 
 1 
 
 367-28 
 
 67-94 
 
 8 
 
 632.36 
 
 89.14 
 
 15- 
 
 176.71 
 
 47.12 
 
 .| 
 
 371-54 
 
 68-33 
 
 .A 
 
 637.94 
 
 8 9 .54 
 
 '\ 
 
 179.67 
 
 47-52 
 
 I 
 
 375.83 
 
 68.72 
 
 f 
 
 643-55 
 
 89-93 
 
 
 
 182.65 
 
 47.91 
 
 22. 
 
 380.13 
 
 69.12 
 
 .1 
 
 649.18 
 
 90.32 
 
 
 
 185.66 
 
 48.30 
 
 
 384.46 
 
 69.51 
 
 I 
 
 654.84 
 
 90.71 
 
 
 
 188.69 
 
 48.69 
 
 
 388.82 
 
 69.90 
 
 2 9 . 
 
 660.52 
 
 91.11 
 
 
 
 I9I-75 
 
 49.09 
 
 
 393-20 
 
 70.29 
 
 i 
 
 666.23 
 
 91.50 
 
 
 
 194-83 
 
 49.48 
 
 
 397-6i 
 
 70.69 
 
 
 
 671.96 
 
 91.89 
 
 
 
 197-93 
 
 49.87 
 
 
 402.04 
 
 71.08 
 
 
 
 
 92-28 
 
 i6. B 
 
 201.06 
 
 50.27 
 
 
 406.49 
 
 71-47 
 
 
 
 683.49 
 
 92.68 
 
 '\ 
 
 204.22 
 
 50.66 
 
 
 410.97 
 
 71.86 
 
 
 
 689.30 
 
 93-07 
 
 
 
 207.39 
 
 5I-05 
 
 23- 
 
 415.48 
 
 72.26 
 
 
 
 695.13 
 
 93-46 
 
 
 
 210.60 
 
 5 T -44 
 
 
 420. 
 
 72.65 
 
 c 
 
 
 700.98 
 
 93-85 
 
 
 
 213.82 
 
 51.84 
 
 i 
 
 424-56 
 
 73-04 
 
 30. 
 
 706.86 
 
 94-25 
 
 
 
 217.08 
 
 52-23 
 
 F 
 
 429-13 
 
 73-43 
 
 4 
 
 712.76 
 
 94.64 
 
 
 
 220.35 
 
 52.62 
 
 I 
 
 433-74 
 
 73-83 
 
 i 
 
 718.69 
 
 95-03 
 
 
 
 223.65 
 
 53-0 1 
 
 f 
 
 438-36 
 
 74.22 
 
 
 724.64 
 
 95-43 
 
 17- 
 
 226.98 
 
 53-41 
 
 .| 
 
 443.01 
 
 74-6i 
 
 'k 
 
 730.62 
 
 95.82 
 
 
 
 230.33 
 
 53-So 
 
 8 
 
 447.70 
 
 75. 
 
 i 
 
 736.62 
 
 9 ^ 
 
 
 
 233-70 
 
 54-19 
 
 24. 
 
 452.39 
 
 75-40 
 
 .| 
 
 742.64 
 
 96.60 
 
 
 
 237.10 
 
 54-59 
 
 \ 
 
 457-H 
 
 75-79 
 
 1 
 
 748.69 
 
 97- 
 
 
 
 240-53 
 
 54-98 
 
 
 461.86 
 
 76.18 
 
 3i- 
 
 754-77 
 
 97-39 
 
 
 
 243-98 
 
 55-37 
 
 I 
 
 466.64 
 
 76.58 
 
 J 
 
 760.87 
 
 97.78 
 
 
 
 247-45 
 
 55-76 
 
 1 
 
 471-44 
 
 76.97 
 
 
 
 766.99 
 
 98.17 
 
 
 
 250.95 
 
 56.16 
 
 1 
 
 476.26 
 
 77.36 
 
 
 
 
 773-H 
 
 98.57 
 
 I& 
 
 254-47 
 
 56.55 
 
 a 
 
 481.11 
 
 77.75 
 
 . 
 
 
 779-31 
 
 98.97 
 
 4 
 
 258.02 
 
 56.94 
 
 1 
 
 485.98 
 
 78.15 
 
 
 
 
 785-51 
 
 99-35 
 
 
 
 261.59 
 
 57-33 
 
 25- 
 
 490.87 
 
 78.54 
 
 . 
 
 
 791-73 
 
 99-75 
 
 
 
 26-. 18 
 
 57-73 
 
 * 
 
 495-So 
 
 78.93 
 
 : 
 
 
 797.98 
 
 100.14 
 
 
 
 26.x So 
 
 58.12 
 
 
 
 500.74 
 
 79-33 
 
 32- 
 
 804.25 
 
 100.53 
 
 
 
 2/2-45 
 
 58.51 
 
 
 
 505.71 
 
 79.72 
 
 i 
 
 810.54 
 
 100.92 
 
 19. 
 
 
 276.12 
 
 279.81 
 
 283.53 
 287.27 
 
 58.90 
 59-30 
 59-69 
 60.08 
 
 
 
 510.71 
 515.72 
 520.77 
 525.84 
 
 80. ii 
 80.50 
 80.90 
 81.29 
 
 
 
 816.86 
 823.21 
 829.58 
 835.97 
 
 101.32 
 101.71 
 
 102. 10 
 102.49 
 
 20. 
 
 21. 
 
 .' 
 
 i 
 
 291.04 
 294.83 
 
 298.65 
 
 302.49 
 306.35 
 310.25 
 314.16 
 318.10 
 322.06 
 326.05 
 330.06 
 
 334-10 
 338.16 
 342.25 
 346.36 
 350-50 
 354-66 
 
 60.48 
 60.87 
 61.26 
 61.65 
 62.05 
 62.44 
 62.83 
 63.22 
 63.62 
 64.01 
 64.40 
 64.79 
 65-19 
 65-58 
 65-97 
 66.37 
 66.76 
 
 26. 
 
 
 
 27. 
 
 - 
 
 2 s'. 
 
 1 
 
 \ 
 
 530.93 
 536.05 
 541-19 
 546.36 
 551-55 
 556.76 
 562. 
 567.27 
 572.56 
 577-87 
 583-21 
 588.57 
 593.96 
 599-37 
 604.81 
 610.27 
 615-75 
 
 81.68 
 82.07 
 82.47- 
 82.86 
 83.25 
 83.64 
 84.04 
 
 84.43 
 84.82 
 85.21 
 85.61 
 86. 
 86.39 
 86.79 
 87.18 
 87-57 
 87.96 
 
 33- 
 
 3**, 
 
 \ 
 
 '! 
 
 
 842.39 
 848.83 
 855-30 
 861.79 
 868.30 
 874.84 
 881.41 
 888. 
 894.62 
 901.25 
 907.92 
 914.61 
 921.32 
 928.06 
 934.82 
 941.60 
 948.42 
 
 102.89 
 103.28 
 103.67 
 104.06 
 104.46 
 104.85 
 105.24 
 105.64 
 106.03 
 106.42 
 
 106.81 
 107.21 
 107.60 
 107.99 
 108.39 
 108.78 
 109.17
 
 430 
 
 APPENDIX. 
 TABI.E No. 13 Continued. 
 
 Diam. 
 in 
 Inches. 
 
 Area 
 in Square 
 Inches. 
 
 Circum. 
 in 
 Inches. 
 
 Diam. 
 in 
 
 Inches. 
 
 Area 
 in Square 
 Inches. 
 
 Circum. 
 in 
 Inches. 
 
 Diam. 
 in 
 Inches 
 
 Area 
 
 in Square 
 Inches. 
 
 Circum. 
 in 
 Inches. 
 
 344 
 
 955-25 
 
 109.56 
 
 41-1 
 
 1360.8 
 
 130.8 
 
 48-f 
 
 1837.9 
 
 152. 
 
 35- 
 
 962.11 
 
 109.96 
 
 .| 
 
 1369. 
 
 I3I.2 
 
 
 1847.5 
 
 152.4 
 
 4 
 
 968.99 
 
 110.35 
 
 1 
 
 1377.2 
 
 131.6 
 
 4 
 
 1857. 
 
 152.8 
 
 J. 
 
 *4 
 
 975-91 
 
 110.74 
 
 42. 
 
 1385.4 
 
 I3I-9 
 
 a 
 
 1866.5 
 
 153-2 
 
 4 
 
 982.84 
 
 III.I3 
 
 4 
 
 1393-7 
 
 132.3 
 
 ! 
 
 1876.1 
 
 153-5 
 
 
 989.80 
 
 HI.53 
 
 -i 
 
 1402. 
 
 132.7 
 
 49- 
 
 1885-7 
 
 153-9 
 
 4 
 
 996.78 
 
 111.92 
 
 4 
 
 HI0.3 
 
 I33-I 
 
 4 
 
 1895.4 
 
 154-3 
 
 .1 
 
 1003.79 
 
 112.31 
 
 
 1418.6 
 
 133-5 
 
 
 1905. 
 
 154-7 
 
 8 
 
 1010.80 
 
 112.70 
 
 4 
 
 1427. 
 
 133-9 
 
 
 
 1914.7 
 
 I55-I 
 
 36- 
 
 1017.88 
 
 II3.IO 
 
 .| 
 
 1435-4 
 
 134-3 
 
 
 
 1924.4 
 
 155-5 
 
 4 
 
 1024.95 
 
 "3-49 
 
 I 
 
 1443.8 
 
 134-7 
 
 . 
 
 
 I934-I 
 
 155-9 
 
 
 1032.06 
 
 113.88 
 
 43- 
 
 1452.2 
 
 I35-I 
 
 
 
 1943-9 
 
 156.3 
 
 .] 
 
 1039.19 
 
 114.28 
 
 4 
 
 1460.6 
 
 135-5 
 
 
 
 1953-7 
 
 156.7 
 
 
 1046.35 
 
 114.67 
 
 . 
 
 1469.1 
 
 135-9 
 
 50. 
 
 I963-5 
 
 I57-I 
 
 
 I053.52 
 
 115.06 
 
 4 
 
 1477.6 
 
 136.3 
 
 4 
 
 1973-3 
 
 157-4 
 
 
 1060.73 
 
 115-45 
 
 1 
 
 1486.2 
 
 136.7 
 
 -| 
 
 1983.2 
 
 157-9 
 
 - f 
 
 1067.95 
 
 115-85 
 
 4 
 
 1494.7 
 
 I37-I 
 
 
 1993- 
 
 158.2 
 
 37- 
 
 1075.2 
 
 116.2 
 
 a 
 
 I503-3 
 
 137-4 
 
 I 
 
 2003. 
 
 158.7 
 
 
 1082.5 
 
 116.6 
 
 .1 
 
 I5II-9 
 
 137-8 
 
 1 
 
 2012.8 
 
 J 59- 
 
 
 1089.8 
 
 117- 
 
 44. 
 
 1520.5 
 
 138.2 
 
 .a 
 
 2022.8 
 
 159-4 
 
 
 1097.1 
 
 117.4 
 
 
 I529.2 
 
 138.6 
 
 8 
 
 2032.8 
 
 159-8 
 
 
 II04-5 
 
 117.8 
 
 .A 
 
 1537-9 
 
 139- 
 
 SI- 
 
 2042.8 
 
 160.2 
 
 
 IIH.8 
 
 118.2 
 
 4 
 
 1546.5 
 
 139-4 
 
 
 2052.8 
 
 160.6 
 
 
 1119.2 
 
 118.6 
 
 .-j 
 
 1555-3 
 
 139.8 
 
 
 
 2062.9 
 
 161. 
 
 
 1126.7 
 
 119. 
 
 4 
 
 1564. 
 
 140.2 
 
 
 
 2072.9 
 
 161.3 
 
 38^ 
 
 1134.1 
 
 119.4 
 
 a 
 
 1572.8 
 
 140.6 
 
 
 
 2083.1 
 
 161.8 
 
 4 
 
 1141.6 
 
 119.8 
 
 8 
 
 1581.6 
 
 141. 
 
 
 
 2093.2 
 
 162.1 
 
 ! 
 
 1149.1 
 
 120.2 
 
 45- 
 
 1590.4 
 
 141.4 
 
 
 
 2103.3 
 
 162.6 
 
 
 1156.6 
 
 1 20. 6 
 
 4 
 
 1599-3 
 
 141.8 
 
 
 
 2II3-5 
 
 162.9 
 
 
 1164.2 
 
 121. 
 
 4 
 
 1 608. 2 
 
 142.2 
 
 52. 
 
 2123.7 
 
 163-4 
 
 
 1171.7 
 
 I2I.3 
 
 4 
 
 1617. 
 
 142.6 
 
 4 
 
 2133-9 
 
 163-7 
 
 
 "79-3 
 
 121.7 
 
 i 
 
 1626. 
 
 142.9 
 
 i 
 
 2144.2 
 
 164.1 
 
 
 1186.9 
 
 I22.I 
 
 4 
 
 1634-9 
 
 143-3 
 
 1 
 
 2154-4 
 
 164.5 
 
 39- 
 
 1194.6 
 
 122.5 
 
 . 
 
 1643.9 
 
 143-7 
 
 
 
 2164.8 
 
 164-9 
 
 4 
 
 1202.3 
 
 122.9 
 
 4 
 
 1652.9 
 
 I44.I 
 
 i 
 
 2175- 
 
 165-3 
 
 j. 
 
 1 2 10. 
 
 123.3 
 
 46. 
 
 1661.9 
 
 144-5 
 
 a 
 
 2185.4 
 
 165-7 
 
 4 
 
 I2I7.7 
 
 123.7 
 
 4 
 
 1671. 
 
 144.9 
 
 i 
 
 2195-7 
 
 166.1 
 
 I 
 
 1225.4 
 
 I24.I 
 
 J 
 
 I680. 
 
 145-3 
 
 53- 
 
 2206.2 
 
 166.5 
 
 8 
 
 1233.2 
 
 124.5 
 
 4 
 
 I689.I 
 
 H5-7 
 
 
 2216.6 
 
 1 66. 8 
 
 .| 
 
 1241. 
 
 124.9 
 
 
 1698.2 
 
 146.1 
 
 .J. 
 
 2227. 
 
 167.3 
 
 I 
 
 1248.8 
 
 125.3 
 
 4 
 
 1707.4 
 
 146.5 
 
 4 
 
 2237.5 
 
 167.6 
 
 40. 
 
 1256.6 
 
 125.6 
 
 .| 
 
 I7I6.5 
 
 146.9 
 
 i 
 
 2248. 
 
 168.1 
 
 
 1264.5 
 
 126. 
 
 8 
 
 1725.7 
 
 147.3 
 
 f 
 
 2258.5 
 
 168.4 
 
 
 1272.4 
 
 126.4 
 
 47- 
 
 1734-9 
 
 H7.7 
 
 .a 
 
 2269. 
 
 168.9 
 
 
 1280.3 
 
 126.8 
 
 f 
 
 1744.2 
 
 148. 
 
 8 
 
 2279.6 
 
 169.2 
 
 
 1288.2 
 
 127.2 
 
 J 
 
 1 753-5 
 
 148.4 
 
 54. 
 
 2290.2 
 
 169.6 
 
 
 1 296. 2 
 
 127.6 
 
 
 1762.7 
 
 148.8 
 
 
 
 2300.8 
 
 170. 
 
 
 1304.2 
 
 128. 
 
 
 1772.1 
 
 149-2 
 
 
 
 2311.5 
 
 170.4 
 
 
 I3I2.2 
 
 128.4 
 
 
 1781.4 
 
 149-6 
 
 
 
 2322.1 
 
 170.8 
 
 41. 
 
 1320.3 
 
 128.8 
 
 
 1790.8 
 
 150. 
 
 
 
 2332.8 
 
 171.2 
 
 4 
 
 1328.3 
 
 129.2 
 
 
 1 800. i 
 
 150.4 
 
 
 
 2343-5 
 
 171.6 
 
 I 
 
 1336.4 
 
 129.6 
 
 48'. 
 
 1809.6 
 
 150.8 
 
 .] 
 
 
 2354-3 
 
 172. 
 
 4 
 
 1344-5 
 
 I 3 0. 
 
 
 1819. 
 
 I5L2 
 
 8 
 
 236.5. 
 
 "72.3 
 
 
 1352.7 
 
 130.4 
 
 i 
 
 1828.5 
 
 I5I.6 
 
 55- 
 
 2375-8 
 
 172.8
 
 AREAS AND CIRCUMFERENCES OF CIRCLES. 
 TABLE No. 13 Continued. 
 
 43* 
 
 Diam. 
 in 
 Inches. 
 
 Area 
 in Square 
 Inches. 
 
 Circum. 
 Inches. 
 
 Diam. 
 in 
 Inches. 
 
 Area 
 in Square 
 Inches. 
 
 Circum. 
 in 
 Inches. 
 
 Diam. 
 Inches. 
 
 Area 
 in Square 
 Inches. 
 
 Circum. 
 Inches. 
 
 55- 
 
 
 2386.6 
 
 I73-I 
 
 61* 
 
 3006.9 
 
 194-3 
 
 68.1 
 
 3698.7 
 
 215-5 
 
 
 
 2397-5 
 
 173-6 
 
 62! 
 
 3019.1 
 
 194.8 
 
 .| 
 
 3712.2 
 
 215-9 
 
 . 
 
 
 2408.3 
 
 173-9 
 
 i 
 
 303L2 
 
 I95-I 
 
 ff 
 
 3725.7 
 
 216.3 
 
 . 
 
 
 2419.2 
 
 174.4 
 
 . 
 
 3043.5 
 
 195-6 
 
 69. 
 
 3739-3 
 
 216.7 
 
 . 
 
 
 2430.1 
 
 174.7 
 
 1 
 
 3055.7 
 
 195.9 
 
 .4 
 
 3752.8 
 
 2I7.I 
 
 . 
 
 
 2441. 
 
 I75-I 
 
 i 
 
 3068. 
 
 196.3 
 
 
 3766.4 
 
 217-5 
 
 . 
 
 
 2452. 
 
 175-5 
 
 1 
 
 3080.2 
 
 196.7 
 
 
 3780. 
 
 217.9 
 
 56. 
 
 2463- 
 
 175-9 
 
 4 
 
 3092.6 
 
 I97.I 
 
 
 3793-7 
 
 218.3 
 
 
 2474. 
 
 
 f 
 
 3104.8 
 
 197-5 
 
 
 3807.3 
 
 218.7 
 
 .1 
 
 2485. 
 
 176.7 
 
 63. 
 
 3117.2 
 
 197.9 
 
 
 3821. 
 
 219.1 
 
 1 
 
 2496.1 
 
 I77.I 
 
 t 
 
 3129.6 
 
 198.3 
 
 
 3834.7 
 
 219-5 
 
 i 
 
 2507.2 
 
 177-5 
 
 
 
 3142. 
 
 198.7 
 
 70. 
 
 3848.5 
 
 219.9 
 
 f 
 
 2518.2 
 
 177.8 
 
 
 
 3I54.4 
 
 199. 
 
 .i 
 
 3862.2 
 
 220.3 
 
 .| 
 
 2529.4 
 
 178-3 
 
 
 
 3166.9 
 
 199-5 
 
 
 3876. 
 
 220.7 
 
 1 
 
 2540.5 
 
 178.6 
 
 
 
 3I79.4 
 
 199.8 
 
 
 3889-8 
 
 221. 
 
 57- 
 
 255I-8 
 
 179.1 
 
 
 
 
 200.3 
 
 i 
 
 3903.6 
 
 221.5 
 
 
 
 2562.9 
 
 179.4 
 
 
 
 3204.4 
 
 20O.6 
 
 .% 
 
 3917.4 
 
 221.8 
 
 .. 
 
 
 2574-2 
 
 179.9 
 
 6 4 '.' 
 
 32I7. 
 
 2OI.I 
 
 f 
 
 3931-4 
 
 222.2 
 
 . 
 
 
 2585.4 
 
 180.2 
 
 
 3229.5 
 
 2OI.4 
 
 i 
 
 3945-2 
 
 222.6 
 
 .. 
 
 
 2596.7 
 
 180.6 
 
 .; 
 
 
 3242.2 
 
 201.8 
 
 71- 
 
 3959-2 
 
 223. 
 
 . 
 
 
 2608. 
 
 181. 
 
 
 
 72S4-8 
 
 202.2 
 
 8 
 
 3973-1 
 
 223-4 
 
 . 
 
 
 2619.4 
 
 181.4 
 
 .; 
 
 
 3267-5 
 
 202.6 
 
 .J 
 
 3987.1 
 
 223.8 
 
 . 
 
 
 2630.7 
 
 181.8 
 
 J 
 
 
 3280.1 
 
 20 3 . 
 
 I 
 
 4001.1 
 
 224.2 
 
 58. 
 
 2642. 1 
 
 182.2 
 
 
 
 3292.8 
 
 203.4 
 
 .i 
 
 4015-2 
 
 224.6 
 
 4 
 
 2653.4 
 
 182.6 
 
 | 
 
 
 3305-5 
 
 203.8 
 
 .1 
 
 4029.2 
 
 225. 
 
 
 
 2664.9 
 
 183. 
 
 65. 
 
 3318.3 
 
 204.2 
 
 f 
 
 4043-3 
 
 225.4 
 
 ,j 
 
 
 2676.3 
 
 183.3 
 
 
 
 3331- 
 
 204.5 
 
 1 
 
 4057. 
 
 225.8 
 
 
 
 2687.8 
 
 183.8 
 
 ,. 
 
 
 3343-9 
 
 205. 
 
 72. 
 
 407L5 
 
 226.2 
 
 
 
 2699.3 
 
 184.1 
 
 J 
 
 
 3356.7 
 
 205.3 
 
 i 
 
 4085-6 
 
 226.5 
 
 
 
 2710.9 
 
 184.6 
 
 ,'. 
 
 
 3369.6 
 
 205.8 
 
 .i 
 
 4099.8 
 
 227. 
 
 
 
 2722.4 
 
 184.9 
 
 
 
 3382.4 
 
 206. 1 
 
 -1 
 
 4114. 
 
 227-3 
 
 59- 
 
 
 2734- 
 
 185.4 
 
 
 
 3395-3 
 
 206.6 
 
 -i 
 
 4128.2 
 
 227-7 
 
 
 
 2745-5 
 
 185.7 
 
 -I 
 
 
 
 3408.2 
 
 206.9 
 
 -1 
 
 4142.5 
 
 228.1 
 
 
 
 2757-2 
 
 1 86. 1 
 
 66. 
 
 3421.2 
 
 207.3 
 
 . J 
 
 4156.8 
 
 228.5 
 
 
 
 2768.8 
 
 186.5 
 
 .4 
 
 3434-1 
 
 207.7 
 
 i 
 
 4171. 
 
 228.9 
 
 
 
 2780.5 
 
 186.9 
 
 
 
 3447-2 
 
 208. 1 
 
 73- 
 
 4185.4 
 
 229.3 
 
 
 
 2792.2 
 
 187.3 
 
 ,\ 
 
 
 3460.1 
 
 208.5 
 
 .4 
 
 4199.7 
 
 229.7 
 
 
 
 2803.9 
 
 187.7 
 
 
 
 3473-2 
 
 208.9 
 
 .4 
 
 4214.1 
 
 230.1 
 
 
 
 2815.6 
 
 188.1 
 
 . 
 
 
 3486.3 
 
 209.3 
 
 .1 
 
 4228.5 
 
 230.5 
 
 60! 
 
 2827.4 
 
 188.5 
 
 
 
 3499-4 
 
 209.7 
 
 1 
 
 4242-9 
 
 230.9 
 
 i 
 
 2839.2 
 
 188.8 
 
 j 
 
 
 3512.5 
 
 210. 
 
 .1 
 
 4257.3 
 
 23I.3 
 
 
 
 2851. 
 
 189.3 
 
 67. 
 
 3525-6 
 
 210.5 
 
 .j 
 
 4271-8 
 
 231.7 
 
 
 
 2862.8 
 
 189.6 
 
 '^ 
 
 3538.8 
 
 210.8 
 
 . 
 
 4286.3 
 
 232. 
 
 
 
 2874.8 
 2886.6 
 
 190.1 
 190.4 
 
 : 
 
 3552. 
 3565.2 
 
 2II.3 
 211. 6 
 
 74 : 
 
 4300.8 
 43I5.3 
 
 232.5 
 232.8 
 
 
 
 2898.5 
 2910.6 
 
 190.9 
 191.2 
 
 
 3578.5 
 3591-7 
 
 212. 1 
 212.4 
 
 .i 
 .1 
 
 4344-5 
 
 233-2 
 233-6 
 
 61! 
 
 
 2922.5 
 2934-4 
 2946.5 
 
 191.6 
 192. 
 192.4 
 
 68. 
 
 3605- 
 363I-7 
 
 212.8 
 213.2 
 213.6 
 
 .-i 
 
 4359-2 
 4373-8 
 4388.5 
 
 234. 
 234-4 
 234-8 
 
 
 
 2958.5 
 2970.6 
 2982.6 
 2994-8 
 
 192.8 
 193.2 
 193-6 
 194. 
 
 .4 
 
 3658*4 
 3671.8 
 3685-3 
 
 214- 
 214-4 
 214.8 
 215-2 
 
 "l 
 
 4403.1 
 
 4417.9 
 4432.6 
 4447-4 
 
 235-2 
 235-6 
 236. 
 236.4
 
 432 
 
 APPENDIX. 
 
 TABLE No. 13 Continued. 
 
 Diam. 
 in 
 Inches. 
 
 Area 
 in Square 
 Inches. 
 
 Circum. 
 in 
 Inches. 
 
 Diam. 
 in 
 Inches. 
 
 Area 
 
 in Square 
 Inches. 
 
 Circum. 
 Inches. 
 
 Diam. 
 in 
 Inches. 
 
 Area 
 
 in Square 
 Inches. 
 
 Circum. 
 in 
 Inches. 
 
 75-1 
 
 4462.1 
 
 236.7 
 
 82. 
 
 
 5297.I 
 
 2 5 8. 
 
 88 i 
 
 6203.6 
 
 279.2 
 
 4 
 
 4477- 
 
 237-2 
 
 
 
 5313.3 
 
 258.4 
 
 8 9 : 8 
 
 6221.1 
 
 279.6 
 
 f 
 
 4491.8 
 
 237-5 
 
 
 
 53294 
 
 258.8 
 
 4 
 
 6238.6 
 
 280. 
 
 .| 
 
 4506.7 
 
 238- 
 
 
 
 5345-6 
 
 259.2 
 
 
 
 6256. 1 
 
 280.4 
 
 1 
 
 4521-5 
 
 238.3 
 
 
 
 5361.8 
 
 259.6 
 
 
 
 
 6273.6 
 
 280.8 
 
 76 
 
 4536.5 
 
 238.8 
 
 
 
 5378.1 
 
 260. 
 
 
 
 6291.2 
 
 281.2 
 
 4 
 
 4551-4 
 
 239.1 
 
 
 
 5394-3 
 
 260.4 
 
 . 
 
 
 6308.8 
 
 281.6 
 
 _i 
 
 4566.4 
 
 239-5 
 
 83. 
 
 
 5410.6 
 
 260.8 
 
 .. 
 
 
 6326.4 
 
 282. 
 
 t 
 
 458i.3 
 
 239-9 
 
 
 
 5426.9 
 
 26l.I 
 
 .1 
 
 
 6344- 
 
 282.3 
 
 4 
 
 
 240.3 
 
 
 
 5443-3 
 
 261.5 
 
 90.' 
 
 
 6361.7 
 
 282.7 
 
 t 
 
 4611.3 
 
 240.7 
 
 
 
 5459-6 
 
 261.9 
 
 ; 
 
 
 6379-4 
 
 283.1 
 
 .| 
 
 4626.4 
 
 24I.I 
 
 
 
 5476. 
 
 262.3 
 
 
 
 6397-I 
 
 283.5 
 
 8 
 
 4641-5 
 
 24L5 
 
 
 
 5492-4 
 
 262.7 
 
 . 
 
 
 6414.8 
 
 283.9 
 
 77- 
 
 4656.6 
 
 241.9 
 
 
 
 5508.8 
 
 263.1 
 
 ., 
 
 
 6432.6 
 
 284-3 
 
 4 
 
 4671.7 
 
 242.2 
 
 
 
 
 263-5 
 
 
 
 6450.4 
 
 284-7 
 
 .; 
 
 
 4686.9 
 
 242.7 
 
 84': 
 
 554^8 
 
 263.9 
 
 
 6468.2 
 
 285.1 
 
 ,j 
 
 
 4702. i 
 
 243- 
 
 
 5558.3 
 
 264.3 
 
 
 6486. 
 
 285.5 
 
 .1 
 
 
 4717-3 
 
 243-5 
 
 .\ 
 
 5574-8 
 
 264.7 
 
 91. 
 
 6503-9 
 
 285.9 
 
 . 
 
 
 4732.5 
 
 243-8 
 
 8 
 
 5591-3 
 
 265. 
 
 4 
 
 6521.7 
 
 286.3 
 
 
 
 4747-8 
 
 244-3 
 
 4 
 
 5607.9 
 
 265.5 
 
 
 
 6539-7 
 
 286.7 
 
 
 
 4763. 
 
 244-6 
 
 f 
 
 5624.5 
 
 265.8 
 
 
 
 6557-6 
 
 287.1 
 
 7 s! 
 
 4778.4 
 
 245- 
 
 a 
 
 5641.2 
 
 266.2 
 
 
 
 6575.5 
 
 287.5 
 
 ., 
 
 
 4793-7 
 
 245-4 
 
 8 
 
 5657-8 
 
 266.6 
 
 
 
 6593^ 
 
 287.8 
 
 .; 
 
 
 4809. 
 
 245-8 
 
 85. 
 
 
 267. 
 
 
 
 6611.5 
 
 288.2 
 
 
 
 4824.4 
 
 246.2 
 
 
 5691.2 
 
 267.4 
 
 
 
 6629.5 
 
 288.6 
 
 ,| 
 
 
 4839-8 
 
 246.6 
 
 . 
 
 5707.9 
 
 267.8 
 
 92. 
 
 6647-6 
 
 289. 
 
 
 
 4855-2 
 
 247- 
 
 f 
 
 5724-6 
 
 268.2 
 
 4 
 
 6665.7 
 
 289.4 
 
 
 
 4870.8 
 
 247-4 
 
 4 
 
 5741-5 
 
 268.6 
 
 
 
 6683.8 
 
 289.8 
 
 \ 
 
 
 4886.1 
 
 247-7 
 
 1 
 
 5758.2 
 
 268.9 
 
 
 
 6701.9 
 
 290.2 
 
 79- 
 
 4901.7 
 
 248.2 
 
 .| 
 
 5775-1 
 
 269.4 
 
 
 
 6720. 1 
 
 290.6 
 
 
 49I7. 2 
 
 248.5 
 
 1 
 
 5791-9 
 
 269.7 
 
 
 
 6738.2 
 
 291. 
 
 4 
 
 4932.7 
 
 249- 
 
 86. 
 
 5808.8 
 
 270.2 
 
 
 
 6756.4 
 
 291.4 
 
 8 
 
 4948.3 
 
 249-3 
 
 4 
 
 5825.7 
 
 270.5 
 
 
 
 6774.7 
 
 291.8 
 
 4 
 
 4963.9 
 
 249-8 
 
 1 
 
 5842.6 
 
 271. 
 
 93- 
 
 
 6792.9 
 
 292.2 
 
 1 
 
 4979-5 
 
 250.1 
 
 I 
 
 5859.5 
 
 271.3 
 
 
 
 68II.I 
 
 292.6 
 
 .| 
 
 4995-2 
 
 250.5 
 
 4 
 
 5876.5 
 
 271.7 
 
 
 
 6829.5 
 
 293- 
 
 I 
 
 5010.8 
 
 250.9 
 
 t 
 
 5893.5 
 
 272.1 
 
 
 
 6847.8 
 
 293-4 
 
 80. 
 
 5026.5 
 
 251-3 
 
 .| 
 
 5910.6 
 
 272.5 
 
 
 
 6866.1 
 
 293-7 
 
 . 
 
 
 5042.2 
 
 25T-7 
 
 1 
 
 5927.6 
 
 272.9 
 
 
 
 6884.5 
 
 294.1 
 
 
 
 5058. 
 
 252.1 
 
 87- 
 
 5944-7 
 
 273-3 
 
 
 
 6902.9 
 
 294-5 
 
 
 
 5073-7 
 
 252.5 
 
 4 
 
 5961.7 
 
 273-7 
 
 
 
 6921.3 
 
 294.9 
 
 
 
 5089.6 
 
 252.9 
 
 
 5978.9 
 
 274.1 
 
 94- 
 
 6939.8 
 
 295-3 
 
 
 
 5105.4 
 
 253-3 
 
 
 5996. 
 
 274.4 
 
 
 6958.2 
 
 295-7 
 
 
 
 5121.2 
 
 253-7 
 
 
 6013.2 
 
 274.9 
 
 
 
 6976.7 
 
 296.1 
 
 
 ' 
 
 5I37-I 
 
 254.1 
 
 
 6030.4 
 
 275.2 
 
 
 
 6995.2 
 
 296.5 
 
 81! 
 
 5I53- 
 
 254-5 
 
 
 6047.6 
 
 275-7 
 
 
 
 7013.8 
 
 296.9 
 
 4 
 
 5168.9 
 
 254-9 
 
 
 6064.8 
 
 276. 
 
 
 
 7032.3 
 
 297-3 
 
 .^ 
 
 5184.9 
 
 255-3 
 
 88. 
 
 6082.1 
 
 276.5 
 
 
 
 7051- 
 
 297-7 
 
 f 
 
 5200.8 
 
 255-6 
 
 
 6099.4 
 
 276.8 
 
 
 
 7069.5 
 
 298.1 
 
 4 
 
 5216.8 
 
 256. 
 
 
 6116.7 
 
 277.2 
 
 95- 
 
 7088.2 
 
 298.5 
 
 1 
 
 5232.8 
 
 256.4 
 
 
 6134. 
 
 277.6 
 
 
 7106.9 
 
 298.8 
 
 a 
 
 4 
 
 5248.9 
 
 256.8 
 
 
 6151.4 
 
 2 7 8. 
 
 . 
 
 7125-6 
 
 299.2 
 
 -1 
 
 5264.9 
 
 257.2 
 
 
 6168. 8 
 
 278.4 
 
 8 
 
 7I44-3 
 
 299.6 
 
 82. 
 
 5281. 
 
 257-6 
 
 
 6186.2 
 
 278.8 
 
 4 
 
 7163. 
 
 300.
 
 AREAS AND CIRCUMFERENCES OF CIRCLES. 
 TABLE No. 13 Continued. 
 
 433 
 
 Diam. 
 in 
 
 Inches. 
 
 Area 
 in Square 
 Inches. 
 
 Circum. 
 in 
 Inches. 
 
 Diam. 
 in 
 Inches. 
 
 Area 
 in Square 
 Inches. 
 
 Circum. 
 in 
 Inches. 
 
 Diam. 
 in 
 Inches 
 
 Area 
 in Square 
 Inches. 
 
 Circum. 
 in 
 Inches. 
 
 95- 1 
 
 7l8l.8 
 
 300.4 
 
 974 
 
 7408.8 
 
 305-I 
 
 98.| 
 
 7639.4 
 
 309.8 
 
 
 7200.6 
 
 300.8 
 
 
 7428. 
 
 305-5 
 
 
 7658.9 
 
 310.2 
 
 8 
 
 7219.4 
 
 3OI.2 
 
 
 7447- 
 
 305-9 
 
 1 
 
 7678.2 
 
 310.6 
 
 96. 
 
 7238.2 
 
 301.6 
 
 
 7466.2 
 
 306-3 
 
 99- 
 
 7697.7 
 
 311- 
 
 
 
 7257.1 
 
 3 02. 
 
 
 7485.3 
 
 306.7 
 
 
 77I7.I 
 
 3"-4 
 
 
 
 7276. 
 
 302.4 
 
 
 7504.5 
 
 307.I 
 
 
 7736.6 
 
 3II.8 
 
 
 
 7294.9 
 
 302.8 
 
 
 7523.7 
 
 307.5 
 
 
 7756.1 
 
 312.2 
 
 
 
 7313.8 
 
 303-2 
 
 98. 
 
 7543- 
 
 307.9 
 
 
 7775-6 
 
 312.6 
 
 
 
 7332-8 
 
 303.5 
 
 
 7562.2 
 
 308.3 
 
 
 7795-2 
 
 3I3- 
 
 
 
 7351-8 
 
 303.9 
 
 .i 
 
 7581.5 
 
 308.7 
 
 
 7814.8 
 
 3134 
 
 
 
 7370-7 
 
 304.3 
 
 8 
 
 7600.8 
 
 309. 
 
 
 7834.3 
 
 3I3.8 
 
 97- 
 
 7389.8 
 
 304.7 
 
 1 
 
 7620. i 
 
 309.4 
 
 100. 
 
 7854- 
 
 314.2 
 
 If the areas of larger circles are required, they will be found by the fol- 
 lowing: 
 
 Rule. Multiply the square of the diameter in inches, by the decimal 0.7854, 
 and the product will be the area in square inches; or, multiply half the cir- 
 cumference by half the diameter. 
 
 If the circumference of a larger circle is wanted, and having the diameter, 
 the rule is as follows: 
 
 Rule.hs> 7 is to 22, so is the diameter to the circumference, or diameter 
 multiplied by 3.1416 equal circumference. 
 
 Properties of Water and Steam. 
 
 In Relation to Heat. 
 
 The following tables for water and steam were calculated by 
 the late John William Nystrom, C. E. M. E., and furnished the 
 writer prior to his publication of them in his new treatise on 
 "Steam Engineering." The relation between temperature and 
 pressure of steam conforms to a uniform curve or law. 
 
 Volume of Water. 
 
 Water, like other liquids, expands in heating and contracts 
 in cooling, with the exception that in heating it from 32 degrees 
 to 40 degrees it contracts, and expands in heating from 40 de- 
 grees upwards. The greatest density or smallest volume of 
 water is therefore at 40 degrees Fahrenheit. 
 
 The most reliable experiments made on this subject are prob- 
 ably those of Kopp, by which the greatest density of water is 
 indicated to be between 39 and 40 degrees, or nearer 39 degrees; 
 but however accurately these experiments might have been made, 
 28
 
 434 APPENDIX. 
 
 it is impossible without the aid of mathematics to determine 
 correctly the temperature of the greatest density, because the 
 curve tangents the abscissa at that point. 
 
 Mr. Nystrom treated Kopp's experiments with very careful 
 mathematical and graphical analysis, resulting in locating 
 the greatest density of water at 40 degrees. 
 
 Properties of Water. 
 
 Column t contains the temperature of the steam and water 
 Centigrade scale. 
 
 Column T contains the temperature of the steam and water, 
 Fahrenheit scale. 
 
 Column V contains the volume of water of temperature 7 , 
 that at 40 degrees being unit. 
 
 This column is calculated from the formula i, deduced from 
 Kopp's experiments, as follows: 
 
 _ (/ ~ 4 )2 
 1400 r + 398500 
 
 The volume deduced from the same experiment, but with the 
 assertion that the greatest density of water is at 39 degrees, 
 will be: 
 
 $ = 1 + _ ('I" 39) 2 
 
 _ 
 
 I4OO T 4- 40540O 
 
 Formula i is the more correct. 
 
 Column ^ contains the weight in pounds per cubic foot of 
 water of temperature 7 . Water of the maximum density at 40 
 degrees weighs 62. 383 pounds per cubic foot. 
 
 Column ( contains the fractional cubic feet per pound of 
 water of temperature 7 . 
 
 Column h contains the units of heat required to raise each 
 pound of water from 32 degrees to T '. 
 
 Column h' contains the units of heat required to raise each 
 cubic foot of distilled water from 32 degrees to temperature 7 
 under the pressure P. 
 
 Column + P denotes the absolute pressure of vapor above 
 vacuum. 
 
 Column p denotes the pressure of vapor tinder that of the 
 atmosphere, which is the vacuum.
 
 AREAS AND CIRCUMFERENCES OF CIRCLES. 435 
 
 Column / contains the units of heat latent in water from 32 
 to T per pound. 
 
 Column /' contains the units of heat latent in water from 32 
 to TO per cubic foot. 
 
 + means pressure above the atmosphere. 
 
 means vacuum under the atmosphere. 
 
 Latent and Total Heat in Water from 32 Degrees. 
 
 When water expands it absorbs heat, which is not indicated 
 as temperature, but remains latent. 
 
 / = latent heat per pound of water heated from 32 degrees. 
 
 W = volume per formula 1, 
 
 t = temperature of the water. 
 
 h = total units of heat per pound of water heated from 32 degrees. 
 
 Latent heat, l = o.it*(V i) . . . .3 
 
 Total heat, h = o. i '/ (W + 9 ) 32 4 
 
 Pounds Per Cubic Foot. 
 _ 62.388 
 
 Cubic Feet Per Pound. 
 
 e = 
 
 62.388 
 
 i 
 
 8 
 
 The latent heat in water heated from 32 to 40 degrees is neg- 
 ative; that is, the water indicates more temperature than units 
 of heat imparted to it The volume at 32 degrees is 1.000156, 
 and the heat required to raise the temperature of one pound of 
 water from 32 to 40 degrees or 8 degrees, is as follows: 
 
 0.999844 x 8 = 7.99875 units. 
 
 The heat required to raise the temperature of one pound of 
 water from 32 to 212 degrees, or 180 degrees, are 181 units of 
 heat. The heat required to raise water from 32 to 350 degrees, 
 or 318 degrees, are 322 units of heat, or 4 units of heat more 
 than the increase of temperature.
 
 436 
 
 APPENDIX. 
 
 TABI,E No. 14 PROPERTIES OF WATER. 
 
 Tempe 
 Centig. 
 
 rature. 
 Fahr. 
 
 Volume. 
 Wat. = i 
 at 40. 
 
 Weight 
 per cubic 
 foot. 
 
 Bulk, 
 cubic feet 
 per Ib. 
 
 Units o 
 per Ib. 
 
 f heat, 
 pr. c. ft. 
 
 Pressur 
 Absol. 
 
 e of vapor, 
 under at. 
 
 P 
 
 0. 
 0-55 
 I. II 
 1.66 
 
 2.22 
 
 T" 
 
 32 
 
 33 
 
 34 
 
 | 
 
 tf 
 
 1.000109 
 1.000077 
 1.000055 
 1.000035 
 
 I.OOO020 
 
 P 
 
 62.3871 
 62.3830 
 62.3842 
 
 62.3859 
 62.3868 
 
 e 
 
 0.0160304 
 0.0160299 
 0.0160295 
 0.0160292 
 0.0160290 
 
 h. 
 o.ooooo 
 
 I.OOOOO 
 2.000OO 
 
 3.00001 
 4.00003 
 
 *'. 
 
 o.oooo 
 
 62.383 
 124.77 
 187.16 
 249.55 
 
 +P. 
 
 0.0864 
 0.0904 
 0.0945 
 0.0988 
 0.1033 
 
 P- 
 
 14.614 
 14.610 
 14.606 
 14.601 
 14-597 
 
 2.77 
 
 3-33 
 3-88 
 4-44 
 S-oo 
 
 37 
 38 
 39 
 40 
 
 4i 
 
 .000009 
 .000003 
 .OOOOOI 
 
 .000000 
 .000003 
 
 62.3875 
 62.3876 
 62.3879 
 62.3880 
 62-3878 
 
 0.0160288 
 0.0160288 
 0.0160287 
 0.0160287 
 0.0160288 
 
 5.00006 
 6.00010 
 
 7.00015 
 
 8.00022 
 
 9.00030 
 
 3"-99 
 
 374-33 
 436-72 
 499.12 
 561.51 
 
 o. 1079 
 o. 1 1 27 
 0.1176 
 0.1228 
 0.1281 
 
 14.592 
 14-587 
 14.582 
 14-577 
 14.571. 
 
 5-55 
 6.ii 
 6.66 
 7.22 
 
 7-77 
 
 42 
 43 
 44 
 45 
 46 
 
 .000016 
 .000034 
 .000053 
 .000077 
 
 .OOOIOI 
 
 62.3873 
 62.3859 
 62.3847 
 62.3832 
 62.3815 
 
 0.0160290 
 0.0160292 
 0.0160295 
 0.0160299 
 0.0160304 
 
 10.00040 
 11.00051 
 12.00065 
 13.00081 
 14.00098 
 
 623.89 
 686.28 
 748.66 
 811.03 
 879.40 
 
 0.1336 
 0.1393 
 0.1452 
 
 0.1513 
 
 o. 1576 
 
 14-566 
 14.561 
 14-555 
 14-549 
 14.542 
 
 9-44 
 
 IO.OO 
 
 10.55 
 
 % 
 
 49 
 50 
 5i 
 
 .000136 
 .000171 
 
 I.0002II 
 
 1.000254 
 1.000302 
 
 62.3797 
 62.3774 
 
 62.3749 
 62.3722 
 62.3692 
 
 0.0160308 
 0.0160314 
 0.0160321 
 0.0160328 
 0.0160335 
 
 15.00132 
 16.00140 
 17.00165 
 18.00192 
 19.00222 
 
 935-70 
 997-77 
 1060. o 
 
 II22.8 
 II85.I 
 
 0.1642 
 
 0.1709 
 0.1780 
 0.1852 
 
 0.1927 
 
 I4.536 
 I4-529 
 14.522 
 I4-5I5 
 14.507 
 
 II. II 
 11.66 
 
 12.22 
 12.77 
 
 13-33 
 
 52 
 53 
 54 
 55 
 56 
 
 1.000353 
 
 1.000408 
 1.000468 
 1.000531 
 1.000597 
 
 62.3660 
 62.3626 
 62.3589 
 62.3549 
 62.3508 
 
 62.3464 
 62.3419 
 62.3370 
 62.3319 
 62.3266 
 
 0.0160344 
 0.0160352 
 0.0160362 
 0.0160372 
 0.0160383 
 
 20.00255 
 21.00292 
 22.00329 
 23.00370 
 24.00415 
 
 I248.O 
 I3IO.I 
 1372.3 
 H34-3 
 1496.4 
 
 0. 2CX >4 
 
 0.2084 
 0.2166 
 0.2252 
 0.2339 
 
 14.499 
 14.491 
 -14.483 
 14-475 
 14.466 
 
 13-88 
 14.44 
 15.00 
 
 15-55 
 
 16.11 
 
 58 
 59 
 60 
 61 
 
 1.000668 
 
 1.000740 
 1.000819 
 1.000901 
 
 1.000986 
 
 0.0160394 
 0.0160405 
 0.0160418 
 0.0160431 
 0.0160445 
 
 25.00462 
 26.00513 
 27.00568 
 28.00626 
 29.00687 
 
 1558.6 
 1620.9 
 1683.2 
 
 !745-5 
 1807.8 
 
 0.2430 
 0.2524 
 0.2621 
 0.2720 
 0.2824 
 
 14-457 
 14.448 
 14.438 
 14.428 
 14.418 
 
 16.66 
 17.22 
 17.77 
 
 18.33 
 18.88 
 
 62 
 
 63 
 64 
 65 
 66 
 
 1.001075 
 1.001167 
 1.001262 
 1.001362 
 1.001464 
 
 62.3211 
 
 62.3153 
 62.3094 
 62.3032 
 62.2968 
 
 0.0160459 
 0.0160474 
 0.0160489 
 0.0160505 
 0.0160522 
 
 30.00752 
 
 31.00821 
 
 32.00894 
 33.00970 
 34.01051 
 
 1870.1 
 1932.4 
 1994.4 
 2056.6 
 2118.7 
 
 0.2930 
 0.3040 
 
 0.3153 
 0.3269 
 
 0.3389 
 
 14.407 
 14.396 
 14.385 
 14-373 
 14.361 
 
 19.44 
 20.00 
 20.55 
 
 2I.II 
 
 21.66 
 
 67 
 68 
 69 
 70 
 7i 
 
 1.001570 
 1.001680 
 
 1.001793 
 
 1.001909 
 1.002028 
 
 62.2902 
 62.2834 
 62.2763 
 62.2692 
 62.2618 
 
 0.0160539 
 0.0160556 
 0.0160575 
 0.0160592 
 0.0160612 
 
 35.011362180.8 
 36.012242242.9 
 37.01377 2305.0 
 38.014152367.1 
 39.015162429.2 
 
 0.3513 
 
 0.3640 
 0.3771 
 0.3906 
 0.4045 
 
 14-349 
 I4-336 
 14323 
 I4.309 
 14.296 
 
 22.22 
 22.77 
 
 23-33 
 23-88 
 24-44 
 
 72 
 73 
 74 
 75 
 76 
 
 1.002151 
 1.002277 
 
 1.002406 
 
 1.002539 
 1.002675 
 
 62.2541 
 62. 2463 
 62.2383 
 62.2300 
 62.2216 
 
 0.0160632 
 0.0160652 
 0.0160673 
 0.0160694 
 0.0160716 
 
 40.01622 2491.2 
 
 41.01733 2553.2 
 
 42.01848:2615.2 
 43.0196812677.1 
 44.02092(2739.2 
 
 0.4188 
 0.4336 
 0.4487 
 0.4644 
 0.4804 
 
 14.281 
 14.266 
 14.251 
 14.236 
 14.220 
 
 25.00 
 25-55 
 26.11 
 26.66 
 27.22 
 
 11 
 
 
 81 
 
 1.002814 
 1.002956 
 1.003101 
 1.003249 
 1.003400 
 
 62.2130 
 62.2042 
 62.1952 
 62.1860 
 62.1766 
 
 0.0160738 
 0.0160761 
 0.0160784 
 0.0160808 
 0.0160832 
 
 45.02222 
 46.02356 
 47.02495 
 
 48.02640 
 
 49.02789 
 
 2801.0 
 2862.8 
 2924.6 
 2985-4 
 3048.2 
 
 0.4970 
 0.5139 
 0.5314 
 0.5493 
 0.5677 
 
 14.203 
 14.186 
 -14-169 
 14.151 
 14.132
 
 APPENDIX. 437 
 
 TABLE No. 14 PROPERTIES OF WATER Continued. 
 
 Tempt 
 Ctntig. 
 
 rature. 
 Fahr. 
 
 Volume. 
 Wat. = i 
 at 40. 
 
 Weight 
 uer cubic 
 foot. 
 
 Bulk, 
 cubic feet 
 per Ib. 
 
 Units o 
 per Ib. 
 
 f heat, 
 pr. c. ft. 
 
 Pressur 
 Absol. 
 
 e of vapor, 
 under at. 
 
 f 
 
 27.77 
 
 28.33 
 28.88 
 29.44 
 30.00 
 
 30.55 
 31-11 
 31.66 
 
 T< 
 
 82 
 83 
 84 
 85 
 86 
 
 87 
 88 
 89 
 
 If 
 
 1-003554 
 1.003711 
 1.003872 
 1.004035 
 1.004199 
 1.004370 
 1.004542 
 1.004717 
 
 V 
 
 62.1671 
 
 62.1574 
 62.1474 
 62.1373 
 
 62.1272 
 
 62.1166 
 62.1059 
 62.0951 
 
 e 
 
 0.0160857 
 0.0160882 
 0.0160908 
 0.0160934 
 0.0160960 
 0.0160987 
 0.0161015 
 0.0161043 
 
 h 
 
 50.02944 
 51.03104 
 52.03269 
 
 53-03439 
 54.03615 
 
 55-03797 
 56.03984 
 57.04177 
 
 h' 
 
 3III.O 
 3172.8 
 3234.4 
 3296-2 
 3358.2 
 
 3418.7 
 3480.4 
 3542.1 
 
 + P. 
 
 0.5868 
 0.6063 
 0.6264 
 0.6470 
 0.6681 
 0.6898 
 0.7121 
 0.7351 
 
 P- 
 
 I4.II3 
 14-093 
 14.074 
 
 14-053 
 14-032 
 14.010 
 -13.988 
 I3-965 
 
 32.22 
 
 32-77 
 33-33 
 33-88 
 34-44 
 
 90 
 
 9i 
 92 
 93 
 94 
 
 1.004894 
 1.005094 
 1.005258 
 1.005444 
 1.005633 
 
 62.0840 
 62.0718 
 62.0617 
 62.0502 
 
 62.0386 
 
 0.016107 
 
 0.016110 
 0.016113 
 0.016116 
 0.016119 
 
 58.0437 
 59-0458 
 60.0479 
 61.0501 
 62.0523 
 
 3603.8 
 3665.0 
 3726.6 
 3788.2 
 3849.8 
 
 0.7586 
 0.7827 
 0.8075 
 0.8329 
 0.8590 
 
 13-94 
 I3-9I 
 I3-89 
 -13-86 
 -13.84 
 
 35-00 
 35-55 
 36.11 
 36.66 
 
 37-22 
 
 9 i 
 
 96 
 97 
 98 
 99 
 
 1.005825 
 1.006019 
 1.006216 
 1.006415 
 1.006618 
 
 62.0267 
 62.0148 
 62.0026 
 
 61.9904 
 61.9779 
 
 0.016122 
 0.016125 
 0.016128 
 0.016131 
 0.016135 
 
 63-0546 
 64.0569 
 
 65.0593 
 66.0618 
 67-0643 
 
 39II.2 
 3972.6 
 
 4033-9 
 4095.2 
 4156.5 
 
 0.8858 
 0.9132 
 0.9609 
 0.9704 
 1.000 
 
 13.81 
 13-79 
 13-74 
 13-73 
 13.70 
 
 &* 
 
 38.88 
 39-44 
 40.00 
 
 IOO 
 101 
 102 
 I0 3 
 104 
 
 1.006822 
 1.007030 
 1.007240 
 1-007553 
 1.007668 
 
 61.9653 
 
 61.9525 
 
 61.9396 
 61.9204 
 61.9133 
 
 0.016138 
 0.016141 
 0.016145 
 0.016150 
 0.016152 
 
 68.0669 
 69.0696 
 70.0723 
 71.0751 
 72.0779 
 
 4217.7 
 4278.9 
 4340.1 
 4401.3 
 4462.5 
 
 1.030 
 1.061 
 .093 
 .126 
 
 159 
 
 I3-67 
 13.64 
 13.61 
 13-57 
 13-54 
 I3-50 
 13-47 
 13-43 
 13.40 
 I3-36 
 
 40.55 
 41.11 
 41.66 
 42.22 
 
 42.77 
 
 105 
 
 106 
 107 
 108 
 109 
 
 .007905 
 .008106 
 .008328 
 .008554 
 .008781 
 
 61.8987 
 1.8728 
 
 61.8589 
 
 61.8450 
 
 0.016155 
 0.016159 
 0.016162 
 0.016166 
 0.016169 
 
 73.0809 
 74.0838 
 75-0869 
 76.0900 
 77.0932 
 
 4523-0 
 4585.0 
 4645.9 
 4706.8 
 4767.7 
 
 .194 
 .229 
 .265 
 .302 
 340 
 
 43-33 
 43-88 
 44-44 
 45-00 
 45-55 
 
 no 
 
 in 
 
 112 
 "3 
 114 
 
 1.009032 
 1.009244 
 1.009479 
 1.009718 
 1.009956 
 
 61.8296 
 
 61.8166 
 1.8022 
 61.7876 
 61.7730 
 
 0.016173 
 0.016177 
 0.016180 
 0.016184 
 0.016188 
 
 78-0965 
 79.0998 
 80.1032 
 81.1067 
 82.1103 
 
 4828.6 
 4889.5 
 4950.4 
 50H.3 
 5072.2 
 
 -378 
 1.418 
 1-459 
 1.500 
 J-543 
 
 13-32 
 -13-28 
 I3-24 
 13.20 
 13.16 
 
 46.11 
 46.66 
 
 47-22 
 
 47-77 
 48-33 
 
 H5 
 
 116 
 117 
 118 
 119 
 
 1.010197 
 1.010442 
 1.010688 
 1.010938 
 1.011189 
 
 61.7583 
 61.7433 
 1.7283 
 61.7130 
 61.6977 
 
 0.016192 
 0.016196 
 0.016200 
 0.016204 
 0.016208 
 
 83-"39 
 84.1176 
 85.1214 
 86.1252 
 87.1292 
 88.1332 
 89.1373 
 90.1414 
 91.1456 
 92.1500 
 
 5I33-0 
 5I93-7 
 5254-3 
 53I4-9 
 5375-5 
 
 1-587 
 1.631 
 1.677 
 1-723 
 1.771 
 
 13." 
 I3-07 
 13.02 
 12.98 
 12.93 
 
 48.88 
 49-44 
 50.00 
 
 50.55 
 
 5T.II 
 
 1 20 
 
 121 
 122 
 I2 3 
 124 
 
 1.011442 
 1.011698 
 1.011956 
 1.012216 
 1.012478 
 
 6i7823 
 61.6666 
 61.6509 
 61.6351 
 f 1. 6192 
 
 0.016212 
 0.016216 
 0.016220 
 0.016224 
 0.016229 
 
 5436.1 
 5496.6 
 5557-1 
 5617-6 
 5678.1 
 
 1.820 
 1.870 
 1.921 
 1-974 
 2.026 
 
 12.88 
 12.83 
 -12.78 
 -12.73 
 12.67 
 
 51.66 
 
 52-22 
 52-77 
 
 53-33 
 53-88 
 
 125 
 126 
 127 
 128 
 129 
 
 1.012743 
 i.onoio 
 1.013278 
 1-013550 
 1.013823 
 
 61.6030 
 61.5868 
 61.5805 
 61.5540 
 61.5374 
 
 0.016233 
 0.016237 
 0.016241 
 0.016246 
 
 0.016250 
 
 93-1543 
 94.1588 
 95-1634 
 96.1680 
 97.1727 
 
 5738.6 
 
 5798.9 
 5859-2 
 59I9-5 
 5979-7 
 
 2.082 
 2-137 
 2.195 
 2.253 
 2.312 
 
 12.62 
 12.56 
 12.50 
 12.45 
 12.39 
 
 54-44 
 
 57-22 
 
 I 3 
 
 135 
 
 1.014098 
 1.015505 
 
 61.5207 
 61.4355 
 
 0.016255 
 0.016277 
 
 98.1775 
 103.2027 
 
 6040.0 
 6340-3 
 
 2-374 
 2.699 
 
 12.33 
 
 12.00
 
 438 APPENDIX. 
 
 TABLE No. 14 PROPERTIES OF WATER Continued. 
 
 Tempe 
 Centig. 
 
 rature. 
 Fahr. 
 
 Volume. 
 Wat. = i 
 at 40. 
 
 Weight 
 >er cubic 
 foot. 
 
 Bulk, 
 cubic feet 
 per Ib. 
 
 Units o 
 perlb. 
 
 f heat, 
 pr. c. ft. 
 
 Pressure 
 Absol. 
 
 of vapor, 
 under at. 
 
 *> 
 
 60.00 
 62.77 
 65.55 
 
 T 
 
 140 
 145 
 ISO 
 
 # 
 
 1.016962 
 1.018468 
 1. 02002 1 
 
 61.3473 
 61.2567 
 61.1635 
 
 e 
 
 0.016301 
 0.016325 
 0.016350 
 
 h 
 
 108.230 
 113.260 
 118.291 
 
 h' 
 
 6639.6 
 
 6937.9 
 7215.1 
 
 +P- 
 
 3-058 
 3.462 
 3.907 
 
 -p. 
 
 11.64 
 11.24 
 10.79 
 
 68.33 
 71.11 
 73.88 
 76.66 
 79-44 
 
 155 
 160 
 165 
 170 
 175 
 
 I.O2l6l9 
 1.023262 
 .024947 
 .026672 
 .028438 
 
 61.0678 
 60.9697 
 60.8695 
 60.7673 
 60.6620 
 
 0.016375 
 0.016401 
 0.016429 
 0.016456 
 0.016485 
 
 123.326 
 128.362 
 I33-40I 
 138.443 
 143.487 
 
 7531-2 
 7826.2 
 8098.1 
 8412.8 
 8704.2 
 
 4-397 
 4-939 
 5-534 
 6.188 
 6.906 
 
 10.30 
 9.761 
 9.166 
 8.512 
 7-794 
 
 82.22 
 85.00 
 87.77 
 90-55 
 93-33 
 96.11 
 98.88 
 
 IOO.OO 
 
 180 
 185 
 190 
 195 
 
 200 
 205 
 2IO 
 212 
 
 .030242 
 .032083 
 .033960 
 1.035873 
 I.0378I9 
 
 1.039798 
 1.041809 
 I.O42622 
 
 60.5567 
 60.4487 
 60.3389 
 60.2275 
 60.1146 
 6o.OO02 
 59-8843 
 59-8376 
 
 0.016513 
 0.016543 
 0.016573 
 0.016604 
 0.016635 
 0.016667 
 0.016799 
 
 0.016811 
 
 148.537 
 I53-583 
 158.635 
 163.691 
 168.749 
 173.809 
 178.873 
 180.900 
 
 8994. 
 9281. 
 
 9571- 
 9858. 
 10318. 
 10428. 
 10712. 
 18824. 
 
 7.693 
 8-550 
 9.488 
 10.51 
 11.62 
 12.83 
 I4.I3 
 14.70 
 
 7.007 
 6.150 
 5.212 
 4.19 
 -3.08 
 -1.87 
 0-57 
 o.ooo
 
 PROPERTIES OF WATER. 
 TABLE NO. 15 WATER. 
 
 439 
 
 Tempe 
 of the i 
 
 Cent. 
 
 rature 
 water. 
 
 Fahr. 
 
 Volume, 
 water = i 
 at 40. 
 
 Weight. 
 Ibs. per 
 cubic ft. 
 
 Bulk, 
 cubic feet 
 >er pound. 
 
 Units of h 
 Tola 
 pound. 
 
 eat in watc 
 per 
 cubic ft. 
 
 r from 32 to TV, 
 Intent per 
 pound, cubic ft. 
 
 f 
 
 100. 
 
 100.5 
 102.4 
 104.2 
 106. 
 107.6 
 
 T 
 
 212. 
 213. 
 216.4 
 219.6 
 222.8 
 225.7 
 
 9 
 
 1.04262 
 1.04296 
 1.04436 
 1.04534 
 1.04638 
 1.04785 
 
 * 
 
 59.838 
 59-8I9 
 59-743 
 59-668 
 59-594 
 59-520 
 
 e 
 
 0.01671 
 0.01671 
 0.01674 
 0.01676 
 0.01678 
 0.01680 
 
 h. 
 
 180.90 
 181.91 
 185.36 
 
 188.59 
 191.83 
 194.78 
 
 h'. 
 
 10825 
 10882 
 11063 
 11241 
 11414 
 U583 
 
 /. 
 
 0.903 
 0.915 
 0-957 
 0.994 
 
 1-033 
 1.082 
 
 /' 
 54-03 
 
 54-73 
 56.73 
 
 59-31 
 61.56 
 64.40 
 
 109.1 
 no. 6 
 
 112. 1 
 
 113.6 
 114.8 
 
 228.5 
 231.2 
 
 233-8 
 236.3 
 
 238.7 
 
 1.04946 
 1.05062 
 
 1.05175 
 1 .05284 
 1.05389 
 
 59-447 
 59.384 
 59-322 
 59-26i 
 59-201 
 
 0.01682 
 0.01684 
 0.01685 
 0.01687 
 0.01689 
 
 197.63 
 200.37 
 
 203.01 
 
 205.55 
 207.98 
 
 II749 
 11895 
 12037 
 12175 
 12309 
 
 I.I30 
 I.I7O 
 1.209 
 1.248 
 I.28I 
 
 67.17 
 69.48 
 
 71.72 
 73.96 
 75-71 
 
 116.1 
 
 117.7 
 118.5 
 119.7 
 120.7 
 
 24I.O 
 
 243-3 
 245-4 
 
 247-5 
 249.4 
 
 1.05490 
 1.05588 
 1.05683 
 1.05776 
 1.05867 
 
 59-I42 
 59-o86 
 
 59-032 
 58.980 
 58-930 
 
 0.01690 
 0.01692 
 0.01694 
 0.01695 
 0.01697 
 
 210.32 
 212.66 
 
 214.79 
 216.84 
 218.86 
 
 12439 
 12561 
 
 12678 
 12791 
 12901 
 
 1.322 
 1-359 
 1-394 
 
 1-437 
 1.462 
 
 78.19 
 80.38 
 82.42 
 84.42 
 86.32 
 
 121. 8 
 
 123.0 
 124.0 
 
 125.1 
 126.1 
 
 251.4 
 253-4 
 255-3 
 257.2 
 259.0 
 
 1-05955 
 1.06042 
 
 1.06128 
 1.06213 
 1.06297 
 
 58.881 
 58.832 
 58.784 
 
 58.737 
 58-690 
 
 0.01698 
 0.01700 
 0.01701 
 0.01702 
 0.01704 
 
 220.90 
 222.93 
 224.86 
 226.80 
 228.63 
 
 13007 
 I3H3 
 I32I7 
 I33I8 
 13416 
 
 I35IO 
 13602 
 
 13692 
 13780 
 13866 
 
 1.496 
 1-532 
 1.565 
 1.598 
 1.630 
 
 88.09 
 90.02 
 91.92 
 93.78 
 95.65 
 
 127.0 
 128.0 
 128.9 
 129.8 
 130.7 
 
 260.7 
 262.4 
 264.1 
 265-7 
 267.3 
 
 1.06380 
 1.06460 
 1.065,38 
 1.06614 
 1.06689 
 
 58.646 
 58-603 
 58.561 
 58.519 
 
 58.477 
 
 0.01705 
 0.01706 
 0.01707 
 0.01709 
 0.01710 
 
 230.36 
 232.09 
 
 233-83 
 
 235-45 
 237.09 
 
 1.664 
 1-695 
 1.726 
 
 I.756 
 1.790 
 
 97-59 
 99-37 
 
 IOI.I 
 102.8 
 
 104.5 
 
 131.6 
 132.5 
 
 133-4 
 134.0 
 134-9 
 
 268.9 
 270.4 
 271.9 
 
 273-3 
 274.8 
 
 1.06761 
 1.06832 
 1.06902 
 1.06971 
 1.07039 
 
 58.437 
 58.398 
 58.359 
 58-321 
 58.284 
 
 0.01711 
 0.01712 
 0.01713 
 0.01714 
 0.01716 
 
 238.72 
 240.25 
 241.78 
 243.20 
 244-73 
 
 13950 
 14036 
 
 I4"5 
 14192 
 14267 
 
 1.816 
 1.846 
 1.879 
 
 1.905 
 1-935 
 
 106.1 
 107.9 
 109.6 
 
 III. 2 
 112.7 
 
 135-6 
 136.4 
 
 137-2 
 
 137-9 
 138.6 
 
 276.2 
 277.6 
 279.0 
 280.3 
 231.6 
 
 1.07105 
 1.07170 
 1.07234 
 1.07297 
 1-07359 
 
 58.250 
 58-214 
 58.179 
 
 58.145 
 
 5<S. 1 1 2 
 
 0.01717 
 0.01718 
 0.01719 
 0.01720 
 0.01721 
 
 246.16 
 247-59 
 249.02 
 
 250.34 
 251.67 
 
 14339 
 I44II 
 
 14482 
 
 I455I 
 14620 
 
 1.961 
 1.990 
 2.018 
 2.045 
 2.075 
 
 II4.2 
 115-8 
 II7.4 
 II8.9 
 120.3 
 
 139.3 282.8 
 40.0 284. i 
 140.8 285.4 
 141.4 286.6 
 142.0 287.8 
 
 1.07421 
 1.07483 
 
 1-07534 
 1-07594 
 I.07653 
 
 58.078 
 58-045 
 58.012 
 57.98o 
 57.948 
 
 0.01722 
 0.01723 
 0.01724 
 0.01725 
 0.01726 
 
 252.90 
 254-22 
 255-66 
 
 256.77 
 258.00 
 
 14688 
 14755 
 14821 
 14886 
 I495I 
 
 2.098 
 2.126 
 
 2.150 
 
 2.175 
 
 2.202 
 
 121-7 
 123-2 
 124-7 
 126.2 
 127.7
 
 440 
 
 PROPERTIES OF WATER. 
 TABLE NO. 16 WATER. 
 
 Tempe 
 of the 
 
 Cent. 
 
 rature 
 water. 
 
 Fahr. 
 
 Volume, 
 water = 
 i at 40. 
 
 Weight. 
 Ibs. per 
 cubic ft. 
 
 Bulk, 
 cubic feet 
 ser pound. 
 
 Units of h( 
 Tota 
 pound. 
 
 :at in wate 
 I per 
 cubic foot, 
 
 r from 32 to To. 
 patent per 
 pound, cubic it. 
 
 ft 
 
 142.8 
 143-4 
 
 144.0 
 144.6 
 145-2 
 
 T* 
 
 289.0 
 290.2 
 291.3 
 292.4 
 293.6 
 
 V 
 
 1.07720 
 1.07778 
 
 1.07835 
 
 1.07892 
 
 1.07943 
 
 9 
 
 57-9 I 7 
 57-886 
 
 57-857 
 57-823 
 57-795 
 
 e 
 
 0.01726 
 0.01727 
 0.01728 
 0.01729 
 0.01730 
 
 h. 
 
 259-23 
 260.46 
 
 261.58 
 262.71 
 263-93 
 
 h'. 
 
 15014 
 15075 
 I5I35 
 I5I95 
 15254 
 
 /. 
 
 2.230 
 2.260 
 2.286 
 2.310 
 2-335 
 
 I'. 
 
 129.2 
 130.8 1 
 132.2 
 
 133-5 
 134-7 
 
 145-9 
 146.6 
 
 147.1 
 
 147-7 
 148.3 
 
 294.7 
 295-8 
 296.9 
 298.0 
 299.0 
 
 300.0 
 301.0 
 302.0 
 
 303.0 
 304.0 
 
 305.0 
 306.0 
 307.0 
 
 307.9 
 308.9 
 
 1.07998 
 1.08051 
 1.08104 
 
 1.08157 
 
 1.08209 
 
 57-768 
 57-739 
 57-7" 
 57.683 
 57.655 
 
 0.01731 
 0.01732 
 0.01733 
 0.01734 
 0.01735 
 
 265.05 
 266.18 
 267.30 
 268.43 
 269.45 
 
 153" 
 15368 
 
 15424 
 15480 
 15535 
 
 2-354 
 2.382 
 
 2.406 
 2.430 
 
 2-454 
 
 136.0 
 137.4 
 138.8 
 140.2 
 141.6 
 
 148.8 
 149-3 
 150.0 
 
 150.5 
 I5I-I 
 
 1.08259 
 1.08311 
 1.08362 
 1.08411 
 1.08460 
 
 57-629 
 57.604 
 
 57-579 
 57-546 
 57-522 
 
 0.01736 
 0.01737 
 0.01738 
 0.01738 
 0.01739 
 
 270.48 
 271.50 
 272.52 
 
 273-55 
 274-58 
 
 15588 
 15641 
 
 15693 
 15746 
 15797 
 
 2.480 
 2-503 
 2-525 
 2.548 
 2.5/2 
 
 142.9 
 144.2 
 
 145-5 
 146.7 
 147.8 
 
 I5I.6 
 152.2 
 152.8 
 
 153-3 
 153-8 
 
 1.08507 
 1.08556 
 1.08604 
 
 1.08653 
 
 1.08700 
 
 57-497 
 57-472 
 57-447 
 57-420 
 57-395 
 
 0.01740 
 0.01740 
 0.01741 
 0.01741 
 0.01742 
 
 275.60 
 276.62 
 277.64 
 278.56 
 279-58 
 
 15846 
 15896 
 15945 
 
 15995 
 16044 
 
 2-595 
 2.618 
 
 2.640 
 2.658 
 
 2.707 
 2.728 
 
 2-755 
 2.776 
 2-795 
 
 149.2 
 150.4 
 151.6 
 152.8 
 I54-I 
 
 154-3 
 154-8 
 
 I55-I 
 155-9 
 156.3 
 
 156.8 
 157-3 
 157-7 
 I58.I 
 158.6 
 
 309.8 
 310.7 
 3II.6 
 312.5 
 313-4 
 
 1.08747 
 
 1.08792 
 
 1.08838 
 1.08883 
 1.08928 
 
 57-370 
 57-346 
 57-322 
 57-298 
 57-275 
 
 0.01743 
 0.01743 
 0.01744 
 0.01745 
 0.01745 
 
 280.51 
 281.43 
 282.35 
 283.27 
 284.19 
 
 16093 
 16140 
 16187 
 16233 
 16278 
 
 155-3 
 156.6 
 
 157.9 
 159-2 
 160.4 
 
 314.3 
 3I5.I 
 315-9 
 316.7 
 317.5 
 
 1.08971 
 1.09014 
 1.09057 
 
 1.09100 
 
 1.09138 
 
 57-252 
 57-230 
 57-208 
 57-186 
 57-164 
 
 0.01746 
 0.01747 
 0.01747 
 0.01748 
 0.01749 
 
 285.12 
 285.94 
 286.76 
 287.58 
 288.40 
 
 16324 
 16368 
 16411 
 
 16453 
 16493 
 
 2.822 
 2.840 
 2.860 
 2.881 
 2.900 
 
 161.6 
 162.7 
 165.8 
 164.8 
 165-9 
 
 I59-I 
 159-6 
 160.0 
 160.4 
 160.8 
 
 318.4 
 319.2 
 320.0 
 320.8 
 321.6 
 
 1.09180 
 I 09222 
 1.09264 
 
 1.09305 
 1.09346 
 
 57.142 
 57.121 
 57-100 
 57-078 
 57-057 
 
 0.01750 
 0.01750 
 0.01751 
 0.01752 
 0.01752 
 
 289.32 
 290.14 
 290.96 
 291.78 
 292.60 
 
 16533 
 16574 
 16614 
 16654 
 16695 
 
 2.920 
 2.940 
 2.960 
 2.980 
 3.000 
 
 166.9 
 168.0 
 169.1 
 170.2 
 I7I-3 
 
 161.2 
 161.6 
 162.2 
 162.6 
 163.0 
 
 322.4 
 323-2 
 
 324.0 
 
 324.7 
 325.4 
 
 1.09384 
 1.09425 
 1.09465 
 1.09506 
 1.09546 
 
 57-036 
 57-015 
 56.994 
 56.973 
 56.953 
 
 0.01753 
 0.01754 
 0.01754 
 0.01755 
 0.01755 
 
 293-42 
 294.25 
 
 295-07 
 
 295.79 
 296.5 
 
 16735 
 16774 
 
 16813 
 16852 
 16890 
 
 3.022 
 3-047 
 3.068 
 3.089 
 3.100 
 
 172.4' 
 173-5 
 174.6 
 
 175-7 
 176.7
 
 PROPERTIES OF WATER. 
 TABLE NO. 17 WATER. 
 
 441 
 
 Tempe 
 of the 
 
 Cent. 
 
 rature 
 jyater. 
 
 Fahr. 
 
 Volume, 
 water = i 
 at 40. 
 
 Weight. 
 Ibs. per 
 cubic ft. 
 
 Bulk, 
 cubic foot 
 >er pound. 
 
 Units of heat in wat 
 Total per 
 pound, cubic ft. 
 
 ;r from 3 
 Latei 
 pound. 
 
 2 to TV 
 
 t per 
 cubic ft. 
 
 P 
 
 163.4 
 163.8 
 164.2 
 164.6 
 165.0 
 
 T 
 
 326.2 
 327.0 
 
 327.7 
 
 328.5 
 329.2 
 
 
 
 1.09578 
 1.09617 
 
 I.09655 
 1.09692 
 1.09730 
 
 fl 
 
 56.934 
 56.9H 
 56.894 
 
 56.875 
 56.855 
 
 
 
 0.01756 
 0.01756 
 0.01757 
 0.01758 
 0.01758 
 
 h. 
 
 297.32 
 298.14 
 
 298.86 
 299.68 
 300.40 
 
 h'. 
 
 16928 
 16966 
 17004 
 17046 
 17078 
 
 /. 
 
 3.121 
 3.I42 
 3-163 
 
 3-183 
 3.204 
 
 I' 
 
 177-7 
 178.8 
 179.9 
 iSl.O 
 182.1 
 
 165.4 
 165.9 
 166.3 
 166.7 
 167.0 
 
 329.9 
 330-7 
 331-3 
 
 331-9 
 332-6 
 
 1.09768 
 1.09804 
 1.09840 
 1.09876 
 1.09911 
 
 56.836 
 56.818 
 56.804 
 56.786 
 56.769 
 
 0.01759 
 0.01759 
 0.01760 
 0.01760 
 0.01761 
 
 301.12 
 301.94 
 302.56 
 303.I7 
 303-89 
 
 17114 
 17149 
 17183 
 
 17217 
 17251 
 
 3-222 
 3.240 
 3.258 
 3.276 
 3-294 
 
 183.1 
 184.1 
 185.1 
 186.0 
 186.9 
 
 167.3 
 167.7 
 168.0 
 168.4 
 168.8 
 
 333-3 
 334-0 
 
 334-7 
 335-4 
 336-I 
 
 1.09949 
 1.09984 
 I.IOOig 
 1.10055 
 1.10091 
 
 56.743 
 56.725 
 56.706 
 56.688 
 56.670 
 
 0.01761 
 0.01762 
 0.01763 
 0.01763 
 0.01764 
 
 304.61 
 305-33 
 306.05 
 306.77 
 307.49 
 
 308.21 
 308.82 
 
 309.44 
 310.16 
 310.88 
 
 17284 
 17318 
 17350 
 
 17384 
 17427 
 
 3-312 
 3-330 
 
 3-349 
 3-368 
 3.387 
 
 187.9 
 189.0 
 190.0 
 191.0 
 192.0 
 
 193-0 
 194.0 
 
 195-0 
 196.0 
 197.0 
 
 169.2 
 169.6 
 170.0 
 170.4 
 170.8 
 
 336.8 
 337-4 
 338.0 
 338.7 
 339-4 
 
 I.IOI25 
 I.IOI59 
 1.10193 
 I.I0226 
 1.10260 
 
 56.652 
 56-635 
 56.618 
 56.600 
 56.583 
 
 0.01764 
 0.01765 
 0.01766 
 0.01766 
 0.01767 
 
 17461 
 17493 
 17525 
 17557 
 17589 
 
 3-406 
 3.425 
 3-444 
 3.462 
 3.481 
 
 I7I.I 
 172.9 
 
 174-5 
 176.2 
 
 177.7 
 
 340.0 
 343-2 
 346.2 
 
 349-2 
 352.0 
 
 1.10292 
 1.10459 
 1.10627 
 1.10787 
 1.10940 
 
 56.566 
 56.483 
 56.403 
 56.326 
 56.236 
 
 0.01768 
 0.01770 
 0.01773 
 0.01775 
 0.01778 
 
 3IL50 
 3H.79 
 317.88 
 320.96 
 323.85 
 
 17621 
 17772 
 17921 
 18068 
 18212 
 
 3-500 
 3-590 
 3.678 
 
 3-763 
 3-850 
 
 198.0 
 202.8 
 
 207-5 
 2I2.I 
 210-5 
 
 179.2 
 180.7 
 182.2 
 
 183.7 
 185.0 
 
 354-8 
 357-4 
 360.0 
 
 362.5 
 365-0 
 
 I.II070 
 I.II208 
 I.II344 
 
 I.I1478 
 1.11613 
 
 56.166 
 56.098 
 56.031 
 
 55.965 
 55-900 
 
 0.01780 
 0.01782 
 0.01784 
 0.01787 
 0.01789 
 
 326.73 
 329.4I 
 332.09 
 334.67 
 337-24 
 
 18349 
 18481 
 
 18607 
 18730 
 18850 
 
 3.927 
 4.010 
 
 4.090 
 4.168 
 4-244 
 
 220.8 
 225.0 
 229.O 
 
 233-3 
 237.2 
 
 186.5 
 188.0 
 188.5 
 190.0 
 191.2 
 
 367.4 
 369.8 
 
 372.0 
 374-2 
 376.4 
 
 I.II742 
 1.11869 
 I.II993 
 I.12I09 
 I.I2227 
 
 55.834 
 55-770 
 55-708 
 55-648 
 55-591 
 
 0.01791 
 0.01793 
 0.01795 
 0.01797 
 0.01799 
 
 339-72 
 342.19 
 344.46 
 
 346.73 
 349.00 
 
 18966 
 19080 
 19190 
 19296 
 19399 
 
 4.318 
 4-390 
 4.460 
 4.530 
 4.598 
 
 24I.O 
 244.6 
 248.5 
 252.1 
 255-7 
 
 192.5 
 193-7 
 194.4 
 197.0 
 199.1 
 
 3/8.5 
 380.6 
 
 382.6 
 386.6 
 390.4 
 
 I-I2343 
 1.12456 
 
 1.12561 
 1.12783 
 1.13000 
 
 55-534 
 55-477 
 55.426 
 
 55.3I7 
 55-211 
 
 0.01800 
 0.01802 
 0.01804 
 0.01807 
 0.0181 1 
 
 35I-I6 
 353-33 
 355-39 
 359-54 
 363-48 
 
 19501 
 19602 
 19698 
 
 19885 
 20068 
 
 4.666 
 
 4-731 
 4-794 
 4-940 
 5.082 
 
 259-1 
 262.5 
 
 265.7 
 272.8 
 279-8
 
 442 
 
 PROPERTIES OF WATER. 
 TABLE No. 18 WATER Continued. 
 
 Temperature 
 
 Volume. 
 
 Weight. 
 
 Bulk. 
 
 Units of heat in water from 32 to T 
 
 * 
 
 water = i 
 
 Ibs. per 
 
 cubic feet 
 
 Total per 
 
 Latent per 
 
 Cent. 
 
 Fahr. 
 
 at 40. 
 
 cubic foot. 
 
 per pound 
 
 pound. 
 
 cubic foot 
 
 pound 
 
 cubic ft 
 
 /. 
 
 To 
 
 V 
 
 V 
 
 6 
 
 h. 
 
 h'. 
 
 /. 
 
 /'. 
 
 2OI.I 
 
 394-0 
 
 1.13210 
 
 55-108 
 
 0.01814 
 
 367.20 
 
 20236 
 
 5-200 
 
 286.6 
 
 203.5 
 
 397-6 
 
 1.13301 
 
 55.017 
 
 0.01817 
 
 370.92 
 
 20402 
 
 5.318 
 
 292.9 
 
 205.0 
 
 401.0 
 
 1.13577 
 
 54.926 
 
 0.01821 
 
 374-44 
 
 20561 
 
 5-437 
 
 299.1 
 
 206.8 
 
 404-3 
 
 1.13760 
 
 54.838 
 
 0.01824 
 
 357-86 
 
 20720 
 
 5-558 
 
 305.2 
 
 208.7 
 
 407.5 
 
 1.13944 
 
 54.752 
 
 0.01826 
 
 381.18 
 
 20870 
 
 5-679 
 
 3II-2 
 
 2IO.2 
 
 410.6 
 
 1.14119 
 
 54.670 
 
 0.01829 
 
 384.40 
 
 21015 
 
 5.800 
 
 3I7-I 
 
 2II.9 
 
 4I3-5 
 
 1.14285 
 
 54.590 
 
 0.01832 
 
 387.40 
 
 21147 
 
 5.903; 324-6 
 
 213.6 
 
 416.5 
 
 1.14441 
 
 54.514 
 
 0.01834 
 
 390.50 
 
 21273 
 
 6.006 
 
 332.0 
 
 2I5.I 
 
 419.2 
 
 1.14589 
 
 54.440 
 
 0.01837 
 
 393-31 
 
 21394 
 
 6.109 
 
 339-5 
 
 216.7 
 
 422.1 
 
 1.14743 
 
 54.367 
 
 0.01839 
 
 396.31 
 
 21510 
 
 6.212 
 
 346.7 
 
 218.2 
 
 424.8 
 
 1.14897 
 
 54.299 
 
 0.01841 
 
 399-H 
 
 21625 
 
 6.315 
 
 353-8 
 
 219.6 
 
 427.4 
 
 1.15050 
 
 54-230 
 
 0.01844 
 
 401.82 
 
 21751 
 
 6.418 
 
 356.9 
 
 221. 1 
 
 430.0 
 
 1.15202 
 
 54.161 
 
 0.01846 
 
 404.52 
 
 21876 
 
 6.521 
 
 359-9 
 
 222.4 
 
 432-4 
 
 1.15339 
 
 54-093 
 
 0.01849 
 
 407.02 
 
 21997 
 
 6.624 
 
 362.8 
 
 223.6 
 
 434-9 
 
 1.15481 
 
 54.024 
 
 0.01851 
 
 409.63 
 
 22114 
 
 6.727 
 
 365.6 
 
 225.1 
 
 437-3 
 
 1.15621 
 
 53-959 
 
 0.01853 
 
 412.13 
 
 22238 
 
 6.830 
 
 368.5 
 
 226.4 
 
 439-6 
 
 1.15764 
 
 
 0.01856 
 
 4I4-53 
 
 22347 
 
 6.926 
 
 373-2 
 
 227.7 
 
 441.9 
 
 1.15880 
 
 53.834 
 
 0.01858 
 
 416.92 
 
 22452 
 
 7-O2O 
 
 377-9 
 
 228.9 
 
 444.1 
 
 1.16003 
 
 53-777 
 
 0.01859 
 
 419.21 
 
 22553 
 
 7.111 
 
 382.5 
 
 230.2 
 
 446.4 
 
 1.16127 
 
 53-721 
 
 0.01861 
 
 421.60 
 
 22650 
 
 7.200 
 
 386.9 
 
 23I-4 
 
 448.5 
 
 1.16250 
 
 53.667 
 
 0.01863 
 
 423-79 
 
 22744 
 
 7.288 
 
 39'-i 
 
 232.5 
 
 450.6 
 
 1.16372 
 
 53-6I4 
 
 0.01865 
 
 425-97 
 
 22843 
 
 7-374 
 
 395-3 
 
 233-6 
 
 452-6 
 
 1.16494 
 
 53-563 
 
 0.01867 
 
 428.06 
 
 22938 
 
 7-459 
 
 399-4 
 
 234-7 
 
 454-6 
 
 1.16571 
 
 53-5I3 
 
 0.01869 
 
 430.14 
 
 23029 
 
 7-542 
 
 403-6 
 
 235-9 
 
 456.7 
 
 1.16695 
 
 53-455 
 
 0.01871 
 
 43232 
 
 23116 
 
 7.623 
 
 407.3 
 
 237.0 
 
 458.7 
 
 1.16818 
 
 53-406 
 
 0.01872 
 
 434.40 
 
 23200 
 
 7.700 
 
 411.2 
 
 238.0 
 
 460.6 
 
 1.16942 
 
 53-352 
 
 0.01874 
 
 436.38 
 
 23282 
 
 7.787 
 
 4I5.5 
 
 23 9 .0 
 
 462.5 
 
 1.17066 
 
 53-293 
 
 0.01876 
 
 438.39 
 
 23363 
 
 7.893 
 
 423,3 
 
 24I.I 
 
 466.1 
 
 I.I7274 
 
 53.158 
 
 0.01881 
 
 442.21 
 
 23555 
 
 8.113 
 
 433-2 
 
 244.1 
 
 471-5 
 
 1.17598 
 
 53-027 
 
 0.01886 
 
 447.83 
 
 23741 
 
 8-329 
 
 442-9 
 
 246.5 
 
 475-7 
 
 1.17917 
 
 52.900 
 
 0.01890 
 
 452.24 
 
 23923 
 
 8.541 
 
 452-4 
 
 248.8 
 
 479.8 
 
 1.18231 
 
 52.768 
 
 0.01895 
 
 456.55 
 
 24091 
 
 8.747] 461.6 
 
 253-1 
 
 487.6 
 
 1-18531 
 
 52.588 
 
 0.01901 
 
 464.66 
 
 24436 
 
 9.060 
 
 476.5 
 
 257.2 
 
 494-9 
 
 1.18961 
 
 52.430 
 
 0.01907 
 
 472.28 
 
 24762 
 
 9.38i 
 
 491.8 
 
 26l.O 
 
 501.8 
 
 I-I9343 
 
 52.264 
 
 0.01913 
 
 479-51 
 
 25061 
 
 9.710 
 
 507.5 
 
 263.5 
 
 508.4 
 
 1.19742 
 
 52.102 
 
 0.01919 
 
 486.40 
 
 25577 
 
 IO.OO 
 
 521.0 
 
 268.1 
 
 514.6 
 
 1.20131 
 
 51-943 
 
 0.01925 
 
 492.97 
 
 25606 
 
 10.37 
 
 538.7 
 
 271.9 
 
 521.4 
 
 i . 20562 
 
 51-787 
 
 0.01931 
 
 500.14 
 
 25901 
 
 o-74 
 
 556.2 
 
 273-3 
 
 526.0 
 
 1.20812 
 
 51-642 
 
 0.01936 
 
 505.00 
 
 26079 
 
 II.OO 
 
 568.1 
 
 277-5 
 
 531-6 
 
 1.21147 
 
 51.498 
 
 0.01942 
 
 510.84 
 
 26307 
 
 11.242 
 
 578.8
 
 APPENDIX. 443 
 
 Steam or Aqueous Vapor. 
 
 Water under atmospheric pressure at ordinary temperature 
 under the boiling point; but that evaporation takes place only 
 on the surface in contact with the air. 
 
 When the temperature of the water is elevated to or above 
 that of the boiling point, then evaporation takes place in any 
 part of the water where the temperature is so elevated. 
 
 The temperature of the boiling point depends upon the pres- 
 sure on the surface of the water. 
 
 P = pressure in pounds per square inch above vacuum on the sur- 
 face of the water. 
 
 T = temperature Fahrenheit of the boiling point. 
 
 6 _ 
 
 To = 200 ^ P 101 ................ i 
 
 p = 
 
 4- loi 
 200 
 
 Example i. At what temperature will water boil under a 
 pressure P = 8 pounds to the square inch ? 
 
 This is under a vacuum of 14.7 8 = 6.7 pounds to the 
 square inch. 
 
 6 
 
 Temperature T = 200 ^8 101 = 181.8 degrees. 
 
 Example 2. What pressure is required to elevate the temper- 
 ature of the boiling point of water 7 = 330 degrees? 
 
 Pressure P= (33 + IOI )'= IOO pounds. 
 
 V 200 ' 
 
 The temperature of the boiling point is the same as that of 
 the steam evaporated under the same pressure. 
 
 Supposing the above formulas to be correct, the ideal zero of 
 aqueous vapor should be at 101 degrees Fahrenheit, or at the 
 temperature 101 degrees below Fahrenheit zero, there is no 
 pressure of the vapor ; that is, the force of attraction between 
 the atoms is equal to the force of expansion by heat. 
 
 Steam exists only as saturated and as superheated steam. 
 The number of units of heat contained in the former is given in 
 the following Tables. The additional number contained in the
 
 444 PROPERTIES OF STEAM. 
 
 latter is found by multiplying the degrees of superheat by 
 which the temperature exceeds that of saturated steam under 
 the same pressure by the decimal 0.48061. Experiments have 
 proved that all the heat abandoned by steam, when condensed, 
 is thus accounted for. 
 
 Properties of Steam. 
 
 Column P contains the total steam pressure in pounds per 
 square inch, including the pressure of the atmosphere. 
 
 Column / is the same pressure in inches of mercury. The 
 specific gravity of mercury at 32 degrees is 13.5959, compared 
 with water of maximum density at 40 degrees. One cubic inch 
 of mercury weighs 0.49086 pounds, of which a column of 29.9218 
 inches is a mean balance of the atmosphere, or 14.68757 pounds 
 per square inch. 
 
 Column 7 contains the temperature of the steam or Fahren- 
 heit scale, deduced from Regnault's experiments. 
 
 Column if contains the volume of steam of the corresponding 
 temperature 7% compared with that of water of maximum den- 
 sity at 40 degrees Fahrenheit. 
 
 Column ^ contains the weight per cubic foot in fractions of 
 a pound. 
 
 Column Q contains the cubic feet per pound of saturated 
 steam under the pressure Pand the temperature 7\ 
 
 Column H contains the units of heat (calorics) per pound of 
 steam from 32 degrees to temperature T and pressure />, calcu- 
 lated from the formula : 
 
 H =. 1082.91 +0.305 T 3 
 
 Column H' contains the units of heat (calorics) per cubic foot 
 of steam from 32 degrees temperature T: 
 
 The above columns H and H' give the calorics required to 
 heat the water from 32 degrees to boiling-point, and evaporate 
 the same to steam under the pressure /'and of temperature T-. 
 
 Column L contains the latent units of heat per pound in 
 steam of temperature To and pressure P. The latent heat ex- 
 presses the work done in the evaporation, or the difference 
 between the calorics per pound in the steam and in the watei 
 of the same temperature.
 
 APPENDIX. 445 
 
 Column L' contains the latent heat per cubic foot of steam. 
 Column^ contains the steam piessure above the atmosphere, 
 as shown on the steam-gage. 
 
 Latent Heat of Steam. 
 
 One pound of water heated under atmospheric pressure, from 
 32 to 212 degrees, requires 180.9 units of heat. If more heat is 
 supplied, steam will be generated without elevating the temper- 
 ature until all the water is evaporated, which requires 1146.6 
 units of heat, and the steam volume will be 1740 times that oc- 
 cupied by the water at 32 degrees. Then, 1146.6 180.9 = 
 965.7 units of heat in the steam which have not increased its 
 temperature. This is what is called latent heat, because it does 
 not show as temperature, but is the heat consumed in perform- 
 ing the work of steam. 
 
 One cubic foot of water at 32 degrees weighs 62.387 pounds; 
 if heated to the boiling point 212 degrees, requires: 
 
 ff= 62.387 x 180.9 = 11285.8 units of heat, 
 and if evaporated to steam under atmospheric pressure, requires: 
 
 ff= 62.387 x 1146.6 = 71532.9 units of heat, 
 of which : 
 
 71532.9 11285.8 = 60247.1, will be latent. 
 
 It is this latent heat which generated 1740 cubic feet of steam 
 from the cubic foot of water. 
 
 The work accomplished by the latent units of heat against 
 the atmospheric pressure will be: 
 
 Work K= 144 x 14.7 X (1740 i) = 3681115 foot pounds. 
 Foot-pounds per unit of heat, /= ^ "y = 6l - J - 
 
 The heat expended in elevating the temperature of the water 
 from 32 to 212 degrees is not realized as work.
 
 446 
 
 PROPERTIES OF STEAM. 
 TABLE NO. I 9 .-STEAM. 
 
 Total 
 
 Ibs. 
 persq 
 inch. 
 
 pressure 
 
 Inches 
 mercur. 
 
 Tem- 
 perat're 
 Fahr. 
 
 Volume 
 water = 
 i at 40. 
 
 Weight 
 Ibs. per 
 cubic fit. 
 
 Bulk 
 cubic ft. 
 per Ib. 
 
 Units o 
 Tota 
 pound. 
 
 r heat fro 
 Iper 
 cubic ft. 
 
 m 32 to T. 
 
 Latent per 
 po'nd cub.ft 
 
 Pres- 
 sure 
 ab've 
 at- 
 mos- 
 ph're 
 
 P 
 
 14.7 
 15 
 16 
 
 17 
 18 
 19 
 
 / 
 
 29.92 
 30.55 
 32-59 
 
 34.63 
 36.67 
 38.71 
 
 T 
 
 212 
 213 
 216.4 
 219.6 
 
 222.8 
 225.7 
 
 t 
 
 1740 
 1706 
 1601 
 
 1509 
 1426 
 
 1353 
 
 P 
 
 0.0358 
 0.0365 
 0.0389 
 0.0413 
 0.0437 
 0.0461 
 
 e 
 
 27.897 
 27.347 
 25.674 
 24.186 
 22.865 
 21.693 
 
 H 
 
 1146.6 
 1147.0 
 1148.0 
 1149.0 
 1149.9 
 1150.8 
 
 H' 
 
 41.100 
 41.920 
 44.700 
 
 47-478 
 50.255 
 53-030 
 
 L 
 
 965-7 
 965-1 
 962.7 
 960.4 
 958.1 
 956.o 
 
 Z' 
 
 34.61 
 35-29 
 37-50 
 39-68 
 41.86 
 44-05 
 
 P 
 .OO 
 3 
 i 
 
 2 
 
 3 
 
 4 
 
 20 
 21 
 22 
 
 23 
 
 24 
 
 40.74 
 42.78 
 44.82 
 46.85 
 48.89 
 
 228.5 
 231.2 
 233-8 
 236.3 
 
 238.7 
 
 1288 
 1228 
 
 H73 
 1123 
 1078 
 
 0.0484 
 0.0508 
 0.0532 
 0-0555 
 0.0579 
 
 20.690 
 19.678 
 18.804 
 18.005 
 17.272 
 
 1151-7 
 1152.6 
 
 II53-4 
 1154.2 
 II55-0 
 
 55-802 
 58.572 
 61.340 
 64.106 
 66.870 
 
 954-1 
 952.2 
 
 950-7 
 
 948.7 
 946.0 
 
 46.23 
 48.41 
 50.48 
 52.65 
 54-82 
 
 5 
 6 
 
 7 
 8 
 9 
 
 25 
 26 
 
 27 
 28 
 29 
 
 50.93 
 52.97 
 55-00 
 
 57-04 
 59.08 
 
 241.0 
 243-3 
 245-4 
 
 247.5 
 249.4 
 
 1035 
 995-1 
 958.2 
 926.4 
 895.6 
 
 0.0602 
 0.0625 
 0.0648 
 0.0672 
 0.0696 
 
 16.597 
 15.994 
 15.422 
 14.881 
 14-371 
 
 "55-7 
 1156.4 
 "57-1 
 
 "57-7 
 1158.2 
 
 69.632 
 72.392 
 
 75-159 
 
 77.9I4 
 80.667 
 
 945-4 ! 56.96 
 943.8,59.09 
 942.361.21 
 940.963.31 
 939-6 65.41 
 
 10 
 
 ii 
 
 12 
 
 13 
 
 14 
 
 30 
 31 
 32 
 
 33 
 34 
 
 35 
 36 
 
 37 
 38 
 39 
 
 6i.n 
 63-15 
 65-19 
 67.23 
 69.26 
 
 251,4 
 253-4 
 255-3 
 257.2 
 259-0 
 
 866.7 
 838.3 
 812.0 
 787.8 
 765.7 
 
 0.0720* 
 0.0743 
 0.0766 
 0.0789 
 O.oSl 2 
 
 13-892 
 13-456 
 13-059 
 12.669 
 12.313 
 
 1158.7 
 1 159-3 
 "59-9 
 1160.5 
 1161.0 
 
 83.410 
 86.162 
 88.913 
 91.662 
 94.411 
 
 937.867-51 
 93 6. 4 '6 9 .6o 
 
 935.171.68 
 
 933-773-75 
 932.4 75-83 
 
 15 
 
 16 
 
 17 
 18 
 19 
 
 71.36 
 73-34 
 75-38 
 77-41 
 79-45 
 
 260.7 
 262.4 
 264.1 
 265.7 
 267.3 
 
 745-8 
 726.9 
 708.8 
 691.7 
 675-4 
 
 0.0834 
 0.0860 
 0.0884 
 0.0908 
 0.0930 
 
 H-955 
 11.624 
 
 11.309 
 11.013 
 10.745 
 
 1161.5 
 1162.0 
 "62.5 
 1163.0 
 "63.5 
 
 97.I56 
 99.901 
 
 102.65 
 105.40 
 108.15 
 
 931.2 
 929.9 
 
 928.7 
 927.6 
 926.4 
 
 925.3 
 924.3 
 923.1 
 922.1 
 921.1 
 
 920.1 
 919.1 
 918.0 
 917.1 
 916.2 
 
 77.89 
 79-95 
 82.01 
 84.06 
 86.10 
 
 20 
 
 21 
 
 22 
 
 23 
 24 
 
 40 
 4i 
 42 
 43 
 44 
 
 * 
 
 47 
 48 
 49 
 
 81.49 
 83-52 
 85-56 
 87.60 
 89.64 
 
 268.9 
 270.4 
 271.9 
 
 273-3 
 
 274.8 
 
 654.9 
 640.0 
 
 625.4 
 611.2 
 
 597-4 
 
 0.0952 
 0.0974 
 0.0997 
 O. I02O 
 0.1044 
 
 10.498 
 10.262 
 10.031 
 9.8030 
 9.5801 
 
 1164.0 
 1164.5 
 1164.9 
 1165.4 
 1165.8 
 
 110.87 
 113.61 
 116.35 
 119.09 
 121.83 
 
 88.14 
 90.18 
 92.21 
 94.24 
 96.26 
 
 25 
 26 
 
 27 
 28 
 29 
 
 3 
 
 3i 
 32 
 33 
 34 
 
 91.67 
 93-71 
 95-75 
 97.78 
 99.82 
 
 276.2 
 277.6 
 279.0 
 280.3 
 281.6 
 
 584.1 
 571-9 
 560.1 
 548.8 
 537-8 
 
 0.1068 
 0.1093 
 O.III7 
 O.II4I 
 O.II66 
 
 9-36I7 
 9-I465 
 8.9486 
 
 8.7596 
 8.5776 
 
 1166.2 
 1166.7 
 1167.2 
 1167.6 
 1168.0 
 
 124.57 
 127.31 
 
 130.05 
 132.79 
 
 135-53 
 
 98.28 
 100.3 
 102.3 
 104.3 
 106.3 
 
 So 
 5i 
 52 
 53 
 54 
 
 101.86 
 103.90 
 
 105-93 
 107.97 
 
 IIO.OI 
 
 282.8 
 284.1 
 285.4 
 286.6 
 287.8 
 
 527.2 
 317.5 
 507-1 
 498.0 
 489.2 
 
 O.II83 
 0. 1 206 
 
 0.1230 
 
 0.1254 
 0.1278 
 
 8 4504 
 8.2899 
 8.1284 
 
 79724 
 7.8249 
 
 1168.4 138.27 
 1168.8 141.00 
 1169.2143.73 
 
 1169.5 146.46 
 1169.8 149.18 
 
 915.4 
 
 9I4.5 
 9 T 3- 6 
 912.7 
 911.8 
 
 108.3 
 110.3 
 112.3 
 
 II4-3 
 116.3 
 
 37 
 38 
 39
 
 PROPERTIES OF STEAM. 
 TABLE No. 20 STEAM. 
 
 447 
 
 Total pressure. 
 
 Tern- 1 Volume 
 
 Weight 
 
 Bulk. 
 
 Units of heat from 32 to T>. 
 
 Pres- 
 sure 
 
 Ibs. 
 persq 
 
 Inches 
 niercur. 
 
 perat're water = 
 Fahr. 1 1 at 40. 
 
 Ibs. per 
 cubic ft. 
 
 cubic ft. 
 per Ib. 
 
 Total per 
 
 Latent per 
 
 at- 
 
 mch 
 
 
 
 
 
 
 pound. 
 
 cubic ft 
 
 po'nd 
 
 cub.ft 
 
 ph're 
 
 P 
 
 / 
 
 7 
 
 t 
 
 9 
 
 e 
 
 H 
 
 H f 
 
 L 
 
 L' 
 
 P 
 
 55 
 
 112.04 
 
 289.0 
 
 480.6 
 
 0.1298 
 
 7.7028 
 
 1170.1 
 
 151.91 
 
 910.9 
 
 118.3 
 
 40 
 
 56 
 
 114.08 
 
 290.2 
 
 472.1 
 
 0.1302 
 
 7.6774 
 
 1170.5 
 
 154.64 
 
 9IO.I 
 
 120.3 
 
 41 
 
 57 
 
 II6.I2 
 
 291.3 
 
 464.0 
 
 0.13247.5524 
 
 1170.9 
 
 157-37 
 
 909.9 
 
 122.2 
 
 42 
 
 58 
 
 118.16 
 
 292.4 
 
 456.2 
 
 0.134617.4277 
 
 1171.3 
 
 160.10 
 
 908.6 
 
 124.2 
 
 43 
 
 59 
 
 120.19 
 
 293.6 
 
 448.8 
 
 0.1388 
 
 7.2034 
 
 1171.6 
 
 162.83 
 
 907.7 
 
 I26.I 
 
 44 
 
 60 
 61 
 
 122.23 
 
 124.27 
 
 294.7 
 295.8 
 
 441.6 
 434-6 
 
 0.1422 
 0.1434 
 
 7.0786 
 6.9709 
 
 1171.9 
 1172.3 
 
 165.56 
 168.28 
 
 906.9 
 906.1 
 
 I28.I 
 130.0 
 
 45 
 46 
 
 62 
 
 126.30 
 
 296.9 
 
 427.8 
 
 0.14566.8643 
 
 1172.6 
 
 171.00 
 
 905.3 
 
 I3I-9 
 
 47 
 
 63 
 
 128.34 
 
 298.0 
 
 421.2 
 
 0.14796.7588 
 
 1172.9 
 
 I73-7I 
 
 904.5 
 
 133-9 
 
 48 
 
 64 
 
 130.38 
 
 299.0 
 
 414.9 
 
 0.15026.6543 
 
 1173.2 
 
 176.41 
 
 903.8 
 
 135-8 
 
 49 
 
 65 
 
 132.42 
 
 300.0 
 
 408.7 
 
 0.15266.5510 
 
 "73-5 
 
 I79-I3 
 
 903.0 
 
 137-8 
 
 50 
 
 66 
 
 134-45 
 
 301.0 
 
 402.6 
 
 0.15486.4570 
 
 1173.8 
 
 181.84 
 
 902.3 
 
 139-7 
 
 51 
 
 67 
 
 136-49 
 
 302.0 
 
 396.7 
 
 0.1571 
 
 6.3660 
 
 1174.1 
 
 184-53 
 
 901.6 
 
 I4I-7 
 
 52 
 
 68 
 
 138.53 
 
 303-0 
 
 39I-I 
 
 0.1593 
 
 6.2750 
 
 1174.4 
 
 187.24 
 
 900.9 
 
 143-6 
 
 53 
 
 69 
 
 140.36 
 
 304.0 
 
 385-6 
 
 0.16166.1852 
 
 1174.7 
 
 190.00 
 
 900.1 
 
 145-6 
 
 54 
 
 70 
 
 142.60 
 
 305-0 
 
 380.4 
 
 0.1640 
 
 6.0972 
 
 1175.0 
 
 192.71 
 
 899.4 
 
 147-5 
 
 55 
 
 71 
 
 144.64 
 
 306.0 
 
 374-7 
 
 0.1662 
 
 6.0162 
 
 II75-3 
 
 19542 
 
 898.7149-5 
 
 56 
 
 72 
 
 146.68 
 
 307.0 
 
 369-5 
 
 0.168415.9363 
 
 1175.6 
 
 198.14 
 
 898.0151-4 
 
 57 
 
 73 
 74 
 
 148.72 
 150.75 
 
 307-9 
 308.9 
 
 364-7 
 360.2 
 
 0.17075.8576 
 0.17305-7799 
 
 1175.9200.85 
 1176.21203.58 
 
 896.6 155.2 
 
 58 
 59 
 
 75 
 
 152.79 
 
 309.8 
 
 355-8 
 
 0.17535-7033 
 
 1176.5 
 
 206. 29 
 
 896.0 I57.I 
 
 60 
 
 76 
 
 154-83 
 
 310.7 
 
 35I-I 
 
 0.17755-6324 
 
 1176.8209.00 
 
 895-4*59-0 
 
 61 
 
 77 
 
 156.86 
 
 311.6 
 
 346.6 
 
 0.1798 
 
 5.5624 
 
 1177.1211.71 
 
 895.8 160.9 
 
 62 
 
 78 
 
 158.90 
 
 312.5 
 
 342.3 
 
 0.1820 
 
 5-4933 
 
 1177.4 214.42 
 
 894.1 162.8 
 
 63 
 
 79 
 
 160.94 
 
 313-4 
 
 338.1 
 
 0.18435.4251 
 
 1177.6217.13 
 
 893.4 164.7 
 
 64 
 
 80 
 
 162.98 
 
 3I4-3 
 
 334-3 
 
 0.18665.3576 
 
 1177.8219.84 
 
 892.7 
 
 166.6 
 
 65 
 
 81 
 
 165.01 
 
 
 330.3 
 
 0.18885-2947 
 
 1178.1 222.55 
 
 892.2 
 
 168.5 
 
 66 
 
 82 
 
 167.05 
 
 3I5-9 
 
 326.4 
 
 0.19115-2327 
 
 1178.41225.25 
 
 891.7 
 
 170.4 
 
 67 
 
 83 
 
 169.09 
 
 3 l6 -7 
 
 322.6 
 
 
 5.1916 
 
 -1178.7 
 
 227.96 
 
 891.1 
 
 172.3 
 
 68 
 
 84 
 
 171.12 
 
 3I7-5 
 
 318.8 
 
 0.19565.1114 
 
 1178.9 
 
 230.68 
 
 890.5 
 
 174.2 
 
 69 
 
 1 
 
 173.16 
 175-20 
 
 318.4 
 319.2 
 
 315-2 
 
 0.197915-0522 
 0.20024.9955 
 
 1179.1 
 1179.4 
 
 233-38 
 236.09 
 
 889.8176.1 
 889.31178.0 
 
 70 
 71 
 
 87 
 
 177.24 
 
 320.0 
 
 308.2 
 
 o.2024 ! 4-9399 
 
 1179.7 
 
 238.79 
 
 888.8 179.9 
 
 72 
 
 88 
 89 
 
 179.27 
 181.31 
 
 320.8 
 321.6 
 
 304.8 
 301-5 
 
 0.2047:4-8855 
 o.2o69'4.8322 
 
 i 
 
 1179.9 
 1 180.1 
 
 241-50 
 244.21 
 
 888.1 181.8 
 887.5! 183.6 
 
 73 
 74 
 
 90 
 
 183.35 
 
 185-38 
 
 322.4 
 323-2 
 
 298.2 
 295.0 
 
 0.20924.7803 
 0.21144.7293 
 
 1180.3 
 1 180.6 
 
 246.91 
 249.62 
 
 886.9 185.4 
 886.4:187-3 
 
 75 
 76 
 
 92 
 
 187.32 
 
 324.0 
 
 291.9 
 
 0.21374-6794 
 
 1180.9 
 
 252.33 
 
 885-9 
 
 189.2 
 
 77 
 
 93 
 94 
 
 189.46 
 191.50 
 
 324.7 
 
 288.9 
 285.9 
 
 0.2159 
 0.2182 
 
 4-6305 
 4-5827 
 
 1181.1 
 1181.3 
 
 255-04 
 257-75 
 
 885.3 
 884.8 
 
 191.0 
 193-2 
 
 7 
 79
 
 PROPERTIES OF STEAM. 
 
 TABI.E No. 21 STEAM. 
 
 Total 
 Ibs. 
 ?nci? 
 
 jressure. 
 
 Inches 
 mercur. 
 
 Tem- 
 
 perat're 
 Fahr. 
 
 Volume, 
 water = 
 i at 40. 
 
 Weight 
 Ibs. per 
 cub ic ft. 
 
 Bulk, 
 cubic ft. 
 per Ib. 
 
 Units of 
 Tota 
 pound. 
 
 heat fro) 
 [per 
 cubic ft. 
 
 n 32 to T". 
 Latent per 
 po'ndlcub.ft 
 
 Pressure 
 above at- 
 mosphere. 
 
 P 
 
 95 
 96 
 
 97 
 98 
 99 
 
 IOO 
 IOI 
 102 
 I0 3 
 104 
 
 105 
 
 106 
 
 107 
 
 108 
 109 
 
 / 
 
 193-53 
 195-57 
 197.61 
 
 I99-65 
 201.68 
 
 T 
 
 326.2 
 327.0 
 
 327.7 
 328.5 
 329.2 
 
 if 
 
 283.0 
 280.2 
 277.4 
 274.7 
 272.0 
 
 . 
 
 O.22O4 
 0.2227 
 0.2249 
 0.2271 
 0.2294 
 
 e 
 
 4.5361 
 4.4902 
 
 4-4454 
 4.4017 
 4-3591 
 
 4-3I76 
 4-2769 
 4-2367 
 4.1970 
 
 4-1577 
 
 H 
 
 1181.5 
 1181.8 
 1182.1 
 1182.3 
 1182.5 
 
 H> 
 
 260.46 
 263.16 
 265.86 
 
 268.55 
 271.23 
 
 88 4 .2 
 883.8 
 
 883-3 
 882.6 
 882.1 
 
 L, 
 
 194.9 
 196.7 
 198.6 
 200.4 
 202.3 
 
 P 
 
 80 
 81 
 82 
 83 
 Jl 
 
 85 
 86 
 
 87 
 88 
 89 
 
 203.72 
 205.76 
 207.79 
 209.83 
 211.87 
 
 329.9 
 330.7 
 331-3 
 
 331-9 
 332.6 
 
 269.4 
 266.8 
 264.3 
 261.8 
 259-4 
 
 0.2316 
 0.2338 
 0.2360 
 0.2382 
 0.2405 
 
 1182.7 273.93 
 1182.9276.63 
 1183.1279.32 
 1183.3:282.62 
 1183.5 284.70 
 
 881.6204.2 
 88i.ol2o6.i 
 880.6208.0 
 880. i 209.8 
 879.6211.6 
 
 213.91 
 215-94 
 217.98 
 
 220.02 
 222.06 
 
 333-3 
 334-0 
 
 334-7 
 335-4 
 336.1 
 
 257.0 
 254.6 
 
 252.3 
 250.1 
 247.9 
 
 0.2428 
 0.2450 
 0.2472 
 0.2495 
 0.2517 
 
 4.1187 
 4.0813 
 4.0444 
 4.0081 
 3.9723 
 
 1183.7287.40 
 1183.9290.09 
 1184.1 292.78 
 1184.3295.48 
 1184.5 298.18 
 
 879.1 
 879.6 
 878.1 
 
 877.5 
 877-0 
 
 876^5 
 876.1 
 
 875.7 
 
 875-1 
 874.6 
 
 213-4 
 215-2 
 217.0 
 218.9 
 220.7 
 
 222.6 
 224.4 
 226.3 
 228.1 
 22 9 .9 
 
 90 
 
 9i 
 92 
 
 93 
 
 94 
 
 9 I 
 96 
 
 97 
 98 
 99 
 
 no 
 III 
 
 112 
 
 "3 
 
 114 
 115 
 
 1 20 
 
 125 
 
 130 
 135 
 
 140 
 
 145 
 150 
 
 155 
 160 
 
 224. 10 
 
 226.13 
 228.17 
 230.20 
 232.24 
 
 336.8 
 337-4 
 338-0 
 338.7 
 339-4 
 
 245.7 
 243.5 
 241.4 
 
 239-3 
 237.3 
 
 0.25403.9376 
 0.256113.9036 
 0.258413.8701 
 0.26033.8411 
 0.262813.8047 
 
 1184.7300.87 
 1184.9303.56 
 1185.1 306.26 
 "85.3308.94 
 1185.5311.65 
 
 234.28 
 244.4 
 254.6 
 264.8 
 275.0 
 
 340.0 
 343-2 
 346.2 
 
 349-2 
 352-0 
 
 235-3 
 226.0 
 
 217.2 
 209.1 
 201.4 
 
 0.2651 3.7722 
 0-275913.6244 
 0.28673.4875 
 0.298413.3516 
 0.30983.2278 
 
 Ii8 5 -7 l 3i4.33 
 1186.6327.89 
 
 1187.51341. 44 
 ii88.4! 3 5 5 .oo 
 1189.31368.55 
 
 874.2 231.8 
 873.81241.0 
 869.6250.1 
 867.41259.0 
 865. 5| 268.i 
 
 IOO 
 
 105 
 no 
 
 "5 
 1 20 
 
 285.2 
 295-4 
 305-6 
 310.8 
 325.9 
 
 354-8 
 357-4 
 360.0 
 
 362.5 
 365-0 
 
 194.3 
 187.8 
 
 181.8 
 
 176.5" 
 
 I7L5 
 
 0.32123.1139 
 0.33223.0105 
 0.3432 2.9136 
 0.35342.8289 
 0.36462.7432 
 
 1190.1 
 1190.9 
 1191.7 
 1192.5 
 II93.3 
 
 381.88 
 395-16 
 408.38 
 
 421.54 
 435-08 
 
 863-5 ! 277.o 
 861.5 285.8 
 859.6 294.5 
 
 857.8303-2 
 856.1312.1 
 
 125 
 130 
 135 
 140 
 H5 
 
 165 
 170 
 
 J75 
 180 
 185 
 
 190 
 195 
 
 200 
 2IO 
 220 
 
 336.0 
 346.3 
 356.5 
 366.7 
 376.9 
 
 367-4 
 369-8 
 372.0 
 374-2 
 376.4 
 
 166.6 
 161.1 
 157-0 
 152-8 
 148.8 
 
 0-3756J2.66I7 
 0.38712.5831 
 0-39732.5171 
 0.4075 2.4541 
 0.4182 2.3916 
 
 1194.0 
 1194.7 
 
 II95-4 
 1196.1 
 1196.8 
 
 448.64 
 462.22 
 475.80 
 488.96 
 502.IO 
 
 854.3 
 852.5 
 851.0 
 849.4 
 847.8 
 
 846.2 
 844.8 
 
 843-3 
 840.3 
 837.5 
 
 32I.O 
 329.9 
 
 338.7 
 
 347-1 
 355-5 
 
 363-9 
 372-4 
 381.0 
 398.0 
 414-8 
 
 150 
 155 
 160 
 
 165 
 170 
 
 175 
 180 
 
 185 
 
 195 
 205 
 
 378.1 
 387.3 
 407.4 
 427.8 
 448.2 
 
 378.5 
 380.6 
 
 382.6 
 386.6 
 390.4 
 
 145.0 
 Hi-S 
 138.1 
 132.0 
 126.3 
 
 0.4292 
 0.4409 
 
 0.4517 
 0.4719 
 
 0-4935 
 
 2.3299 
 2.2684 
 2.2137 
 2.1192 
 2.0265 
 
 1197.4 
 1198.1 
 1198.7 
 1199.8 
 
 I20I.O 
 
 515.20 
 528.27 
 542.07 
 568.40 
 574-70
 
 PROPERTIES OF STEAM. 
 
 449 
 
 TABLE NO. 22.-STEAM. 
 
 Total 
 
 Ibs. 
 persq 
 inch. 
 
 pressure. 
 
 Inches 
 mercur. 
 
 Tem- 
 perat're 
 Fahr. 
 
 Volume 
 water = 
 i at 40. 
 
 Weight 
 Ibs. per 
 cubic ft. 
 
 Bulk 
 cubic ft. 
 per Ib. 
 
 Units ol 
 Tota 
 pound. 
 
 heat fro 
 Iper 
 cubic ft. 
 
 mj^l 
 Later 
 po'nd 
 
 o 7X 
 tper 
 cub. ft 
 
 Pres- 
 sure 
 ab've 
 at- 
 mos- 
 ph're 
 
 P 
 
 230 
 
 240 
 250 
 260 
 270 
 
 / 
 
 468.5 
 
 488.9 
 
 509.3 
 
 529-7 
 550.0 
 
 To 
 
 394-0 
 397-6 
 401.0 
 
 404-3 
 
 407-5 
 
 * 
 
 120.8 
 
 116.1 
 in. 7 
 
 107.5 
 103.7 
 
 9 
 
 0.5165 
 0.5364 
 
 0-5595 
 0.5803 
 0.6016 
 
 e 
 
 .9360 
 .8646 
 
 .7874 
 .7230 
 .6621 
 
 H 
 
 1202.2 
 1203.2 
 1204.2 
 1205.2 
 I2O6.2 
 
 IP 
 
 620.96 
 647.41 
 
 673.85 
 700.28 
 726.66 
 
 L 
 
 835.0 
 832.3 
 829.8 
 827.4 
 825.0 
 
 822.8 
 820.7 
 818.6 
 816.5 
 814.4 
 
 8^4 
 810.5 
 
 808.6 
 806.9 
 805.1 
 
 803.4 
 801.7 
 800.0 
 
 799-4 
 797-7 
 
 L' 
 
 431-3 
 447-9 
 464-4 
 480.8 
 497-1 
 
 513.3 
 529.4 
 545-4 
 561.4 
 577-3 
 
 P 
 
 215 
 22 5 
 
 235 
 245 
 255 
 
 280 
 290 
 300 
 310 
 320 
 
 570.4 
 590.8 
 
 611.1 
 
 631-5 
 65I-9 
 
 4J0.6 
 413.5 
 416.5 
 419.2 
 422.1 
 
 IOO.2 
 
 97-Qi 
 
 94-22 
 
 91-13 
 88.21 
 
 0.6238 
 0.6459 
 0.6681 
 0.6896 
 0.7107 
 
 .6031 
 .5481 
 .4967 
 
 -4499 
 .4071 
 
 I2O7.2 
 I208.I 
 I2O9.O 
 1209.8 
 I2I0.6 
 
 753-04 
 779.40 
 
 805.74 
 832.96 
 858.36 
 
 265 
 275 
 285 
 295 
 305 
 
 315 
 325 
 335 
 345 
 355 
 
 330 
 340 
 350 
 360 
 370 
 
 672.3 
 692.6 
 713.0 
 
 733-4 
 753-8 
 
 424.8 
 427.4 
 430.0 
 
 432-4 
 434-9 
 
 85.44 
 83-19 
 80.99 
 
 78.84 
 76.74 
 
 0.7302 
 0-7547 
 0-7745 
 
 0-7943 
 0.8146 
 
 3695 
 3250 
 
 -2915 
 .2590 
 2275 
 
 1211.5 
 1212.3 
 1213.1 
 1213.9 
 1214.7 
 
 884.63 
 910.89 
 
 937-13 
 963.34 
 989-5I 
 
 593-2 
 608.9 
 624.5 
 640.2 
 655-8 
 
 380 
 39 
 400 
 410 
 420 
 
 774-1 
 794-5 
 814.9 
 835-2 
 855-6 
 
 437-3 
 439-6 
 441.9 
 444.1 
 446.4 
 
 74-66 
 72.90 
 71.19 
 69.52 
 67.90 
 
 0-8353 
 0.8626 
 0.8745 
 0.8952 
 0.9142 
 
 .1968 
 1597 
 1434 
 .1170 
 1-0938 
 
 1215.5 
 
 I2I6.2 
 I2I6.9 
 I2I7.6 
 I2I8.3 
 
 1015.7 
 1041.8 
 1067.9 
 1094.0 
 II2O.2 
 
 671-3 
 686.7 
 
 702.0 
 717.2 
 732-4 
 
 365 
 375 
 385 
 395 
 405 
 
 415 
 425 
 435 
 445 
 455 
 
 430 
 440 
 
 450 
 460 
 470 
 
 480 
 490 
 500 
 
 525 
 550 
 
 876.0 
 896.4 
 916.7 
 
 937-1 
 957-5 
 
 448.5 
 450.6 
 
 452.6 
 454-6 
 456.7 
 
 66.34 
 64.91 
 
 63-55 
 62.22 
 60.94 
 
 0.9400 
 0-9599 
 0.9804 
 1.0007 
 
 I.02II 
 
 1.0634 
 1.0417 
 
 I.O2OI 
 0.9993 
 0.9793 
 
 I2I8.9 
 I2I9.5 
 I220.I 
 I22O.7 
 I22I.3 
 
 1146.3 
 II72.3 
 1198.3 
 1224.3 
 1250.4 
 
 795-o 
 793-5 
 792.0 
 
 790-5 
 789.0 
 
 787-5 
 786.1 
 
 784.7 
 782.3 
 778.0 
 
 747-6 
 762.8 
 
 777-9 
 792.9 
 807.8 
 
 H22.7 
 
 837.4 
 852.1 
 
 881.8 
 921.3 
 
 977-8 
 998.2 
 1018.6 
 1069.5 
 1120.4 
 
 458.7 
 460.6 
 
 462.5 
 466.1 
 471-5 
 
 59-72 
 58.54 
 57-45 
 54.81 
 52.47 
 
 1.0446 
 1.0652 
 1-0859 
 I.I38I 
 1.1890 
 
 0-9573 
 0.9388 
 
 0.9209 
 0.8786 
 O.S^IO 
 
 I22I.9 
 1222.5 
 1223.0 
 1224.5 
 1225.8 
 
 1276.5 
 1302.3 
 I328.I 
 1392.6 
 1456.9 
 
 465 
 475 
 485 
 5io 
 535 
 
 575 
 600 
 
 650 
 700 
 
 750 
 
 1171.4 
 1222.3 
 1324.2 
 1426.0 
 1527-9 
 
 475-7 
 479-8 
 487.6 
 
 494-9 
 501.8 
 
 50.32 
 48.35 
 44-75 
 41.70 
 39-05 
 
 1-2397 
 1.2901 
 
 1-3943 
 1.4964 
 1-5977 
 
 08066 
 0.7751 
 0.7172 
 0.6684 
 O.6259 
 
 1227.2 
 1228.3 
 1230.6 
 1232.7 
 1-J34.9 
 
 I52I.O 
 1584.8 
 17095 
 1933-8 
 2057.7 
 
 775-0 
 771-8 
 766.0 
 760.4 
 755-4 
 
 960.4 
 
 IOOO 
 
 1082 
 
 "57 
 .234 
 
 56o 
 
 585 
 635 
 685 
 735 
 
 800 
 850 
 900 
 950 
 
 IUOO 
 
 1629.8 
 1731.6 
 
 1833.5 
 
 1935-5 
 2037.2 
 
 508.4 
 
 514.6 
 
 521.4 
 526.0 
 531-6 
 
 36.73 
 34-68 
 32.87 
 31-21 
 29-73 
 
 1.6986 
 1.7989 
 1.8979 
 1.9992 
 2.0986 
 
 0.5887 
 
 0-5554 
 0.5269 
 0.5002 
 0.4765 
 
 1237.0 
 1238.9 
 I24I.O 
 1242.4 
 1243-5 
 
 2IOI.2 
 2228.3 
 
 2355-4 
 2482.5 
 2609.6 
 
 750.6 
 745-9 
 740.0 
 
 737-4 
 732-3 
 
 1307 
 1374 
 1435 
 1490 
 1538 
 
 785 
 835 
 885 
 
 
 
 29
 
 450 
 
 MEAN PRESSURE. 
 NO. 23 MEAN PRESSURE OP EXPANDING STEAM. 
 
 Abso- 
 lute 
 steam 
 pres- 
 sure. 
 
 P 
 
 1-333 
 I 
 
 i-5 
 1 
 
 Grade of 
 1.6 ' 
 Steam cut 
 
 * 
 
 expansion 
 
 off at I, fr 
 
 * 
 
 f steam, denoted by^ 
 2.666 3 
 mi beginning of stro 
 
 f * 
 
 r. 
 ;e. 
 
 i 
 
 8 
 
 1 
 
 o-5 
 i 
 
 2 
 
 3 
 4 
 
 5 
 6 
 
 7 
 8 
 9 
 
 0.4826 
 0.9652 
 
 I-9304 
 2.8956 
 3.8608 
 
 0.4683 
 0.9367 
 
 1.8734 
 2.8100 
 3.7468 
 
 0.4587 
 0.9175 
 1.8350 
 
 2.7524 
 3.6700 
 
 0.4232 
 0.8465 
 1.6931 
 
 2.5396 
 3-3862 
 
 0.3713 
 0.7426 
 
 1.4482 
 2.2280 
 2.8964 
 
 0-3497 
 0.6995 
 
 I-399I 
 2.0986 
 2.7982 
 
 0.2982 
 0.5965 
 1.1931 
 
 1.7897 
 2.3862 
 
 0.1924 
 0.3849 
 
 0.7698 
 
 1.1548 
 1-5396 
 
 4.8262 
 5-79I4 
 6.7566 
 7.7216 
 8.6866 
 
 4-6835 
 5.6202 
 
 6.5569 
 7-4936 
 8.5303 
 
 4.5875 
 5.5050 
 6.4225 
 7.3400 
 8.2574 
 
 4.2328 
 5-0794 
 5.9260 
 6.7726 
 7.6192 
 
 3.7133 
 4-4559 
 5-1966 
 
 5.94I3 
 6.6840 
 
 3-4977 
 4.1972 
 
 4.8967 
 
 5-5963 
 6.2958 
 
 2.9828 
 
 3-5794 
 4.1760 
 4.7726 
 5-3692 
 
 1.9246 
 
 2.3095 
 2.6944 
 
 3.0794 
 3.4643 
 
 10 
 ii 
 
 12 
 
 13 
 14 
 
 9-6524 
 10.617 
 
 11-583 
 12.548 
 I3-5I3 
 
 9.3670 
 10.304 
 11.240 
 12.177 
 13-113 
 
 9.I750 
 10.092 
 
 II.OIO 
 
 11.927 
 12.845 
 
 8.4657 
 9-3123 
 10.159 
 11.005 
 11.852 
 
 7.4267 
 8.1694 
 8.9121 
 9.6548 
 10.397 
 
 6-9954 
 7.6949 
 
 8-3944 
 9.0940 
 9-7935 
 
 5-9657 
 6.5622 
 
 7-I589 
 
 7.7555 
 8.3520 
 
 3.8493 
 4.2342 
 
 4.6191 
 5.0041 
 5-3890 
 
 15 
 
 16 
 
 17 
 
 18 
 19 
 
 14.478 
 15-443 
 16.408 
 
 17-373 
 18-339 
 
 14.050 
 14.987 
 
 15-923 
 16.860 
 17.797 
 
 13.762 
 14.679 
 
 15.597 
 16.514 
 17-432 
 
 12.698 
 13-545 
 14.392 
 15-238 
 16.085 
 
 11.140 
 11.882 
 12.625 
 13-368 
 14.110 
 
 10.493 
 11.192 
 
 11.892 
 12.591 
 13-291 
 
 8.9485 
 9-5451 
 10.141 
 10.738 
 "335 
 
 5-7739 
 6.1588 
 
 6-5437 
 6.9287 
 7-3136 
 
 20 
 
 21 
 22 
 
 23 
 24 
 
 19-304 
 20.269 
 21.234 
 22.199 
 23-165 
 
 18.734 
 19.671 
 
 20.508 
 
 21-545 
 22.481 
 
 18.350 
 
 19.268 
 
 20.185 
 21.103 
 22.020 
 
 16.931 
 17.778 
 18.625 
 19.471 
 20.318 
 
 14.853 
 I5-596 
 
 16-339 
 17.082 
 17.823 
 
 I3.99I 
 14.690 
 
 15.390 
 16.089 
 16.789 
 
 11.931 
 12.527 
 13.124 
 13.720 
 14.317 
 
 7.6986 
 8.0835 
 8.4684 
 
 8.8534 
 9-2383 
 
 % 
 
 27 
 28 
 2 9 
 
 24.130 
 25.096 
 26.061 
 27.026 
 27.991 
 
 23.481 
 24-355 
 25.291 
 26.228 
 27.165 
 
 22.938 
 23.855 
 
 24.773 
 25.690 
 
 26.607 
 
 21.164 
 22.011 
 22.857 
 23.704 
 24.55I 
 
 18.567 
 19.318 
 20.052 
 20.795 
 21.538 
 
 17.488 
 18.188 
 18.887 
 
 19-587 
 20.287 
 
 14-9*3 
 I5.5H 
 16.107 
 16.704 
 17.300 
 
 9.6232 
 10.008 
 
 10.393 
 10.778 
 11.162 
 
 3 
 31 
 
 32 
 
 33 
 34 
 
 28.956 
 29.920 
 30.886 
 
 31-852 
 32.816 
 
 28.100 
 29.036 
 29.974 
 30.910 
 31.846 
 
 27.524 
 28.440 
 
 29.358 
 30.276 
 31.194 
 
 25.396 
 26.244 
 
 27.090 
 27.936 
 28.784 
 
 22.280 
 23.022 
 
 23-764 
 24.508 
 25-250 
 
 20.986 
 21.684 
 22.384 
 23.084 
 23-784 
 
 17.897 
 18.493 
 19.090 
 19.687 
 20.282 
 
 11.548 
 11.932 
 12.317 
 12.702 
 13-087 
 
 P 
 
 37 
 38 
 39 
 
 33.782 32.784 
 34.746 ( 33.720 
 35.712 34.656 
 36.678 35-594 
 37.642 36.530 
 
 32.110 
 33.028 
 33.946 
 
 34.864 
 35.780 
 
 29.630 
 30.476 
 31.322 
 32.170 
 33-016 
 
 25.992 
 26.736 
 
 27.478 
 28.220 
 28.964 
 
 24.484 
 25.182 
 25.882 
 26.582 
 27.282 
 
 20.880 
 21.476 
 22.072 
 
 22.6/0 
 23.266 
 
 I3-472 
 13.857 
 14.242 
 14.627 
 15.012
 
 MEAN PRESSURE. 
 TABLE NO. 24 MEAN PRESSURE of EXPANDING STEAM. 
 
 451 
 
 Abso- 
 lute 
 
 Grade of expansion of steam, denoted by g. 
 
 steam 
 pres- 
 
 1-333 
 
 1-5 
 
 1.6 
 
 2 
 
 2.666 
 
 3 I 4 8 
 
 sure. 
 
 Strain cnt off at I, from beginning of stroke. 
 
 P 
 
 * 
 
 
 
 t 
 
 * 
 
 1 
 
 i 
 
 * 
 
 * 
 
 50 
 
 48.262 
 
 46.835 
 
 45.875 
 
 42.328 
 
 37-133 
 
 34-977 
 
 29.828 
 
 19.246 
 
 55 
 
 53-088 
 
 51-518 
 
 50.462 
 
 46.561 
 
 40.846 
 
 38-474 
 
 32.811 
 
 21.170 
 
 60 
 
 57.914 
 
 56.202 
 
 55.050 
 
 50-794 
 
 44-559 
 
 41.972 
 
 35-794 
 
 23-095 
 
 65 
 
 62.740 
 
 60.885 
 
 59.637 
 
 55-027 
 
 48.273 
 
 45-470 
 
 38.777 
 
 25.020 
 
 70 
 
 67.566 
 
 65-569 
 
 64.225 
 
 59.260 
 
 51-986 
 
 48967 
 
 41.760 
 
 26.944 
 
 75 
 
 72.393 
 
 70.252 
 
 68.812 
 
 63493 
 
 55.700 
 
 52-465 
 
 44-743 
 
 28.869 
 
 80 
 
 77.216 
 
 74-936 
 
 73.400 
 
 67.726 
 
 59-4I3 
 
 55.963 
 
 
 30.794 
 
 85 
 
 82.042 
 
 79.619 
 
 77.987 
 
 71-959 
 
 63.126 
 
 59.461 
 
 50.709 
 
 32.718 
 
 90 
 
 86.866 
 
 85-303 
 
 82.574 
 
 76.192 
 
 66.840 
 
 62.958 
 
 53-692 
 
 34-643 
 
 95 
 
 91.699 
 
 89.986 
 
 87.163 
 
 80.425 
 
 70.553 
 
 66.456 
 
 56-675 
 
 36.568 
 
 jico 
 
 96.524 
 
 93.670 
 
 9I-750 
 
 84.657 
 
 74.267 
 
 69-954 
 
 59-657 
 
 38.493 
 
 105 
 
 101.35 
 
 98.353 
 
 96.337 
 
 88.890 
 
 77.981 
 
 73-451 
 
 62.640 
 
 40.417 
 
 no 
 
 106.17 
 
 103.04 
 
 100.92 
 
 93-123 
 
 81.694 
 
 76.949 
 
 65.622 
 
 42.342 
 
 "5 
 
 III.OO 
 
 107.72 
 
 I0 5-5i 
 
 97.356 
 
 85.407 
 
 80.447 
 
 68.606 
 
 44.267 
 
 120 
 
 115-83 
 
 112.40 
 
 IIO.IO 
 
 101.59 
 
 89.121 
 
 83.944 
 
 71-589 
 
 46.191 
 
 125 
 
 120.65 
 
 117.08 
 
 114.68 
 
 105.82 
 
 92-834 
 
 87.442 
 
 74-572 
 
 48.116 
 
 130 
 
 125.48 
 
 121.77 
 
 119.27 
 
 110.05 
 
 96.548 
 
 90.940 
 
 77-555 
 
 50.041 
 
 135 
 
 130.30 
 
 126.45 
 
 123.86 
 
 114.28 
 
 100.26 
 
 94-437 
 
 80.538 
 
 51-966 
 
 140 
 145 
 
 135.13 
 139.96 
 
 131-13 
 
 135-82 
 
 128.45 
 133-03 
 
 II8.52 
 122.75 
 
 103.97 
 107.68 
 
 97-935 
 101.43 
 
 83-520 
 86.502 
 
 53-890 
 55.815 
 
 150 
 155 
 
 144.78 
 149.60 
 
 140.50 
 145.18 
 
 137.62 
 142.20 
 
 126.98 
 131.22 
 
 111.40 
 115.11 
 
 104-93 
 108.42 
 
 89.485 
 92.468 
 
 57-739 
 59-663 
 
 160 
 
 154-43 
 
 149.87 
 
 146.79 
 
 135-45 
 
 118.82 
 
 111.92 
 
 95-451 
 
 61.588 
 
 165 
 170 
 
 159-26 
 164.08 
 
 154-55 
 I59-23 
 
 151-38 
 155-97 
 
 139.68 
 I43.92 
 
 122.54 
 126.25 
 
 115.42 
 118.92 
 
 98.434 
 101.41 
 
 63-513 
 65.437 
 
 175 
 180 
 
 168.91 
 173-73 
 
 163.92 
 168.60 
 
 160.55 
 165.14 
 
 148.15 
 152.38 
 
 129.96 
 133-68 
 
 122.42 
 125.91 
 
 104.40 
 107.38 
 
 67-362 
 69.287 
 
 185 
 
 178.56 
 
 173-28 
 
 169.73 
 
 156.61 
 
 137-39 
 
 129.41 
 
 110.36 
 
 71.212 
 
 190 
 195 
 
 183-39 
 188.21 
 
 177.97 
 182.65 
 
 174.32 
 178.90 
 
 160.85 
 165.08 
 
 141.10 
 144.82 
 
 132.91 
 136.41 
 
 "3-35 
 116.33 
 
 73.136 
 75-o6i 
 
 200 
 
 2IO 
 
 193-04 
 202.69 
 
 187.34 
 196.71 
 
 183.50 
 192.68 
 
 169.31 
 
 177.78 
 
 148.53 
 I55-96 
 
 I39.9I 
 146.90 
 
 119.31 
 125.27 
 
 76.986 
 80.835 
 
 220 
 
 212.34 
 
 205.08 
 
 201.85 
 
 186.25 
 
 163.39 
 
 I53.90 
 
 131.24 
 
 84.684 
 
 230 
 240 
 
 221.99 
 2 3 I - 6 5 
 
 215-45 
 224.81 
 
 211.03 
 220.20 
 
 194.71 
 203.18 
 
 170.82 
 178.23 
 
 160.89 
 167.89 
 
 137.20 
 I43.I7 
 
 88.534 
 92-383 
 
 250 
 260 
 
 241.30 
 250.96 
 
 234.18 
 
 243-55 
 
 229.38 
 
 238.55 
 
 211.64 
 220.11 
 
 185-67 
 193.18 
 
 174.88 
 181.88 
 
 I49.I3 
 I55-" 
 
 96.232 
 100.08 
 
 270 
 280 
 300 
 
 260.61 
 270.26 
 289.56 
 
 252.91 
 262.28 
 281.00 
 
 247-73 
 256.90 
 275-24 
 
 228.57 
 237.04 
 253-96 
 
 200.52 
 
 207.95 
 222.80 
 
 188.87 
 
 I95-87 
 209.86 
 
 161.07 
 167.04 
 178.97 
 
 103-93 
 107.78 
 115-48
 
 INDEX. 
 
 A BSOLUTE pressure, 54-56 
 1\ definition of, 55, 56 
 
 of steam, how meas- 
 ured, 55 
 
 Accidental inventions, 30 
 Action and work of expanding steam, 
 
 63-67 
 of steam in the cylinder, 124 
 
 in the cylinder as shown by the 
 indicator diagrams, with illus- 
 tration, 88-90 
 in the cylinder of an engine, 
 
 i? 5 " 93 ., ., 
 when expanded, 72, 73 
 
 Actual horse-power, definition of, 97 
 Adiabatic cards, 167 
 
 curve, 167, 168 
 Admission line, 128 
 Advantage of variable automatic ex- 
 pansion, 194, 195 
 Advantages of the compound steam 
 
 engine, 291-294 
 Aeolipile, the, described and illustrated, 
 
 22 
 Air, how removed from water for steam 
 
 engine purposes, 117 
 the possible chief motive power of 
 
 the future, 312 
 weight of a cubic foot of, 48 
 Air-pump, 231, 232 
 capacity of, 231 
 invention of the, 28 
 
 Alexander, Emperor of Russia, present 
 
 to Capt. Rogers by, 40 
 Allowance for compression and clear- 
 ance, to make, 379-384 
 America, first attempt to propel boats 
 
 by steam in, 31 
 
 American Academy of Arts and Sci- 
 ences, recommendation from a 
 select committee of, for granting 
 a patent to Nathan Read, 32 
 locomotives, fair average of the 
 
 performance of, 260-262 
 Ancients, loss of knowledge and pro- 
 gress by reason of the false meth- 
 ods and philosophy of the, 21 
 the true nature of steam not known 
 
 by the, 21 
 Aneroid, necessity for a, 119 
 
 Apparatus for making Dowson's gas, 
 
 344, 345 
 used by the early English miners 
 
 for raising ore, 94 
 Approximation, an, to the effective 
 
 mean pressure, 407, 408 
 Aqueous vapor, ideal zero of, 51 
 
 vapor or steam, 50, 51, 443, 444 
 Areas and circumferences of circles, 
 
 table of, 428-433 
 Athemius, experiment by, 25 
 Atkinson gas-engine, 331-339 
 
 "cycle" gas-engine, diagrams from 
 
 the, 331 
 patent " cycle " gas-engine, trial of, 
 
 334-339 
 
 Atmosphere, an, definition of, 45, 46 
 momentous importance of the dis- 
 covery of the pressure of the, 28 
 object of knowing the exact pres- 
 sure of the, 118, 119 
 the weight and pressure of the, 
 
 proved by Torncelli. 26 
 "Atmospheric engine," 29 
 
 engine of Newcomen, with illus- 
 tration, 234-236 
 gas-engine, Otto and Langen, 319, 
 
 320 
 line, 125 
 
 the, how drawn on diagrams, 
 
 119 
 
 pressure, 49 
 Automatic condensing engine, diagram 
 
 from, 357-359.. 
 cut-off engine, diagrams from, 203, 
 
 372-375 
 
 superiority of the, exem- 
 plified, 349-354 
 engines, 249-252 
 saving by, 196 
 vs. positive cut-off, 349-371 
 engines, varieties of, 251 
 expansion engines, 247-249 
 non-condensing engine, diagram 
 
 from, 357 
 
 steam-engine, 242, 243 
 steam-engines, the most prominent 
 
 in general use, 242 
 
 Avoidance of intermediate expansion, 
 285-287 
 
 (453)
 
 454 
 
 INDEX. 
 
 B 
 
 ACK-PRESSURE, 160, 161 
 cause of increased, 134 
 diminution of, how effected, 117 
 
 in non-condensing and condensing 
 engines, with illustration, 115,116 
 line, 135 
 
 or line of counter-pressure, 133-135 
 principal cause of increased, 160,161 
 variation in the excess of, in non- 
 condensing engines, 134, 135 
 Baldwin locomotive, No. 81, diagrams 
 
 from, 259, 260 
 Works, lead allowed by 
 
 the, 140 
 Barber, John, patent for the production 
 
 of force taken out by, 317 
 Barcelona, Spain, early exhibition of a 
 
 steamboat in, 25 
 
 Bayonne and Biarritz Railway, intro- 
 duction of compound locomotives 
 on, 302 
 
 Belmont Water Works, Philadelphia, 
 data from the contract trial of H. R. 
 Worthington, with, 389 
 "Blowing out," 420 
 Blow-through valves, 228 
 Boiler, calculation of the useful evap- 
 oration of a, 376, 377 
 compound of George W. Lord, of 
 
 Philadelphia, advantage of, 421 
 disturbance, or priming, 419 
 foaming of, 420 
 horizontal flue, 419 
 incrustation remedies, 421 
 portable furnace tubular, invented 
 
 by Nathan Read, 32 
 power of a, 422 
 pressure, line of, 126 
 
 how drawn on diagrams 
 for non - condensing 
 engines, 121 
 solvents, 421 
 Boilers, 416, 417 
 
 incrustation of, 419-421 
 joints of, 417, 418 
 rivet holes of, 418 
 strength of shell-plates ot, 418 
 superiority of steel for, 417 
 Boiling, 45-47 
 
 liquid, temperature of, 53 
 point, definition of, 45 
 
 of water, on what it depends, 51 
 temperature of, 443 
 Bonouville, essay by, 36 
 Booth & Garrett of Philadelphia, en- 
 dorsement of Lord's boiler compound 
 by, 421 
 Boston and Albany Railroad, trial of 
 
 compound locomotives by, 309 
 Boyle's law, 162 
 Boyle and Mariotte's law, 129 
 
 Boyle and Mariotte's law as usually ex- 
 pressed, 164 
 
 conditions under which it 
 holds good with all 
 gases, 164, 165 
 deviation from, 177 
 Brown, Samuel, gas-engine invented 
 
 by, 317 
 
 "Brumbo" pulley, illustrated, 391-393 
 Brush Electric Light Station, Philadel- 
 phia, diagram from an engine at the, 
 146 
 
 Bucket valves, 232 
 Buckeye automatic engine, indicator 
 
 diagrams from a, 254 
 engine, 253-258 
 
 diagrams from, 399, 400 
 mean card of, 399, 400 
 table of pressures of, 400, 401 
 test of, 397-399 
 
 /CAMERA obscura, invention of, 23 
 \^, Carbon, heating power of one 
 
 jxmnd of, 204 
 units of heat generated by a 
 
 pound of, 43 
 Card, best way of finding the mean 
 
 pressure of a, 105 
 Cavendish and Lavoisier, investigation 
 
 of water by, 43 
 
 Cawley and Newcomen's engine, 29, 30 
 Centigrade and Fahrenheit thermom- 
 eters, 422 
 
 Chart of relative economy, under vary- 
 ing loads, 299. 300 
 
 Cheverton, letter on gas-engines by, 317 
 Circles, table of circumferences and 
 
 areas of, 428-433 
 Circumferences and areas of circles, 
 
 table of, 428-433 
 
 Classification of steam-engines, 224, 225 
 Clearance, 181 
 
 and compression, to make allow- 
 ance for, 379-384 
 effect of, 181-185 
 
 too much on the diagram, 
 
 illustrated, 185, 186 
 how to calculate the, 189, 190 
 impossibility of avoiding, 184 
 in the ordinary steam-engine, 189 
 line, 126, 127 
 
 how to fix when not known, il- 
 lustrated, 200 
 
 method of locating the, with dia- 
 gram, 382, 383 
 principles relating to, 185 
 proportion of loss by, 181-184 
 " Clermont," the launching of, 37 
 Clerk gas-engine, 324-327 
 
 diagrams from, 326, 327
 
 INDEX. 
 
 455 
 
 Clerk, M. Dugald, theory of the gas- 
 engine by, 312-316 
 Coal, amount of, required per hour per 
 
 horse-power, 80, 81 
 anthracite, average content of car- 
 bon of, 42, 43 
 gas and Dowson gas, comparative 
 
 explosive force of, 346 
 progress in the economy of fuel by 
 improvements in the steam en- 
 gine traced by the number of 
 pounds burnt per hour per horse- 
 power, 101 
 
 quantity of heat obtained from the 
 combustion of three pounds 
 of, 205 
 
 of, required to produce an indi- 
 cated horse power, 101 
 reason why only a small percent- 
 age of the power contained in 
 each pound is realized, 229, 230 
 units of heat developed by one 
 
 pound of, 101 
 Co-efficient of expansion of superheated 
 
 steam, 50 
 
 Commercial horse-power, 97 
 Comparative efficiency of different en- 
 
 fines, 234-236 
 icator diagrams, 189207 
 Compound and simple system, 270, 271 
 condensing engine, diagrams from, 
 
 289 
 theoretical diagram of a, 
 
 286, 287 
 
 engines, 287-290 
 
 engine, condemned by many en- 
 gineers, 292 
 
 points of superiority of, 281, 282 
 engines, action and arrangement 
 of the principal varieties of, 
 illustrated, 272-276 
 best results of, 348 
 early, 290, 291 
 objection to, 283 
 with intermediate reservoir or 
 
 receiver, 277-281 
 
 locomotive, improved by Francis 
 W. Webb, 303, 304 
 
 patented by T. W. Worsdell, 
 
 305-309 
 locomotives, 300-309 
 
 ecomomy of fuel of, 303 
 failure in this country as 
 
 economizers of fuel, 309 
 steam engine, advantages of, 291- 
 
 294 
 engines, 266-276 
 
 historical data referring 
 
 to, 269, 270 
 
 system, advantage claimed for, 
 279, 280 
 
 Compound system, disadvantages of, 
 
 280, 281 
 
 versus simple engines, 281-284 
 Compounding, what it is, 266 
 Compression, actual curve of, as shown 
 
 by the indicator, 138, 139 
 and clearance, to make allowance 
 
 for, 379-384 
 
 curve, termination of, 138 
 desirability of, with diagrams, 370, 
 
 371 
 
 indication of an excess of, 136, 137 
 line of, 136-139 
 most advantageous adjustment of, 
 
 136 
 
 useful effect of, 137, 138 
 Computation of the economy of water 
 consumption, 379, 380 
 table, 383 
 
 example for use of the, with 
 
 illustration, 384-386 
 explanation of, 384 
 Conclusion, 408-410 
 Condensation in cylinders clothed with 
 
 non-conducting material, 213 
 in steam engine cylinders, 204-007 
 of steam, 53 
 
 necessity of preventing the, 
 
 221 
 
 pressure of, 133, 160 
 Condenser, 225, 226 
 
 actual pressure in the best, 160 
 
 capacity of, 226 
 
 cause of the pressure in the, 133, 
 
 134 
 
 jet, 226-230 
 
 saving effected by a good, 228 
 temperature of the, 226, 227 
 vacuum in the, 226 
 Condensers, cause of their efficiency, 
 
 228 
 
 "jet," 33 
 
 removal of water from, 227, 228 
 "surface," 33 
 
 Condensing and non-condensing en- 
 gine, difference between a, 87 
 and non-condensing engines, dif- 
 ference between, 1 16 
 
 variable expansion, further ad- 
 vantage of, 195-197 
 automatic cut-off engine, diagram 
 
 from, 359 
 
 engine, theoretical indicator dia- 
 grams from, 65-67 
 engines, 225 
 
 back-pressure in, 115, 116 
 water, lifting of, 230, 231 
 Construction of the indicator, 82-84 
 Continuous expanding compound en- 
 gine, curious form of, 273-275 
 expansion engine, 278,279
 
 456 
 
 INDEX. 
 
 Corliss compound engine, diagram il- 
 lustrated, 290 
 
 engine, diagram from a, 155, 156 
 horse-power of a, by the indi- 
 cator, with illustration, 102- 
 104 
 
 Corliss, George H. , introduction of the 
 modern cut-off engine by, 249, 250 
 reduction in the consumption of 
 
 coal, by, 101 
 Cornish engines, pressure of steam in, 
 
 233 
 
 pumping engine, as invented by 
 Watt, 236 
 
 engines, consumption of coal 
 by, 101 
 duty of, 35 
 history of, 35 
 indicator diagram from, 
 
 238 
 
 Cornwall, remarkable examples of the 
 application of the single-acting en- 
 gines to pumping in, 237 
 Correct indicator diagrams, 148-161 
 Counter pressure, line of, 133-135 
 Cowper C., diagram published by, with 
 
 illustrations, 178, 179 
 Crosby, Messrs., trial of Dowson gas, 
 
 by, 346 
 
 steam engine indicator, with illus- 
 trations, 415, 416 
 Curve, adiabatic, 167, 168 
 isothermal, 198 
 isothermic, 167 
 
 of expansion, 129-131, 187, 188 
 Cushioning, 136-139 
 Cut-off, automatic vs. positive, 349- 
 
 37i 
 
 most economical point of, 62, 63 
 point of, 129 
 
 valve arrangements, modern auto- 
 matic, 144 
 Cylinder, action of the, towards the 
 
 steam, 214 
 
 action of steam in the, 124 
 action of steam in the, as shown by j 
 the indicator diagrams, with il- 
 lustration, 88-90 
 condensation, 34 
 " distribution " for the, 88 
 higher terminal pressure in, 166 
 how to take a diagram from each 
 
 end of the, 156 
 maintenance of a proper steam 
 
 pressure in the, 128, 129 
 mean temperature of, how in- 
 fluenced, 130 
 offices the steam has to perform 
 
 upon entering the, 292, 293 
 variation in the temperature of, 
 205, 206 
 
 D ALTON'S experimental results on 
 evaporation below the boiling 
 temperature, 44 
 law, 44, 45 
 De Caus, Salomon, machine for raising 
 
 water described by, 25 
 Descartes, Kepler and Galileo, 26 
 Diagram, best way of finding the mean 
 
 pressure of a, 105 
 essentials for the correctness of 
 
 the, 390 
 
 exhibiting improvement in modern 
 engines in the valve motion, 246 
 from a compound engine, 282 
 
 vertical engine with inter- 
 mediate receiver, 277 
 condensing automatic cut-off 
 
 engine, 359 
 
 Corliss engine, 155, 156 
 double-acting engine, 240-242 
 locomotive engine, when run- 
 ning slow, 259 
 modern built automatic cut-off 
 
 engine, 374, 375 
 non-condensing engine, 359. 
 Corliss engine, 250 
 throttling engine, 245 
 plain slide valve engine, 369, 
 
 370 
 
 Porter-Allen engine, 253 
 pumping engine, 360 
 simple compound Westing- 
 house engine, 287 
 Westinghouse compound con- 
 densing engine, 287 
 an automatic condensing engine, 
 
 357-359 
 
 cut-off engine, 203, 372-374 
 non-condensing engine, 357 
 engine with a steam jacket 
 over the ends and sides, 221 
 at the Brush electric light 
 station, Philadelphia, Pa., 
 146 
 how taken from each end of the 
 
 cylinder, 156 
 
 ideal, with illustration, 124, 125 
 illustrating a method of locating 
 
 the clearance Hue, 382, 383 
 low pressure, values of, 283, 284 
 of the action of the steam in an 
 automatic condensing en- 
 gine, 254 
 
 action of steam in an expan- 
 sive engine, 209 
 expansion curve of steam in an 
 imperfectly protected cylin- 
 der, 212, 213 
 real, how drawn, 175 
 showing steam used expansively, 
 154, 155
 
 INDEX. 
 
 457 
 
 Diagram, the causes of different form j Diagrams, showing a fair average of the 
 of engine, 79 performance of American loco- 
 
 theoretical, with illustrations, 169-! motives, 260-262 
 
 the action of steam in a steam 
 
 Diagrams, facts to which they will tes- 
 tify, 151 
 
 frictional, power shown by, how 
 calculate i on stationary engines, 
 with illustrations, 121, 122 
 from a Clerk gas engine, 326, 327 
 compound-condensing engine, 
 
 289 
 
 triple-expansion en- 
 gine, 297, 298 
 an upright automatic cut-off 
 
 engine, 375 
 Baldwin locomotive, No. 81, 
 
 259, 260 
 continuous-expansion engines, 
 
 281 
 five horse Otto engine, 321, 
 
 322 
 
 freight locomotive, 362, 363 
 horizontal compound-condens- 
 ing, triple-expansive engine, 
 298, 299 
 
 Lenoir gas engine, 318, 319 
 locomotive No. 51, Southern 
 
 Pacific Railroad, 365-367 
 locomotives, general interest 
 of, 363 
 
 what may be learned from, 
 
 364 
 'M. Mallet's locomotive, 302, 
 
 33 
 
 one of the best build of Eng- 
 lish locomotives, 262-266 
 pair of engines connected at 
 
 right angles, 290 
 passenger locomotive, 361, 362 
 Porter Allen engine, 395, 396 
 single acting engines, interpre- 
 tation of, 238-240 
 single valve straight line en- 
 gine, 255, 256 
 
 the Atkinson "cycle" gas en- 
 gine, 331 
 
 the Buckeye engine, 399, 400 
 the engines of a flouring mill, 
 
 350-354 
 the Southwark engine, 403 
 
 404 
 
 the Worthington pumping en- 
 gine at Belmont, Philadel- 
 phia, 367, 368 
 illustrating the relative engine 
 
 economy, 354-357 
 instructiveness of, 412 
 
 engine cylinder, 124-147 
 Directions for using the planimeter, 
 
 with illustrations, 108-114 
 Disadvantages of too large an engine, 
 
 200-203 
 
 Discovery of jet condensation, 30 
 Distorted indicator diagrams, 374, 375 
 " Distribution " for the cylinder, 88 
 
 "periods of," 88 
 
 Division of the outline drawn by the 
 instrument during a revolution of the 
 engine, 127 
 
 Double-acting engines, 240- 242 
 Dowson's water gas, 335, 344- -348 
 Drake, Alfred, construction of a gas 
 
 motor by, 317 
 
 gas engines exhibited by, 310, 311 
 " Drop," or intermediate expansion, 283 
 
 cut-off," 251 
 Dry and wet steam, 53 
 Duty, TOO, 101 
 
 definition of, 100, 387 
 
 estimation of, 388 
 
 extraordinary, from a gas pumping 
 
 engine, 336 
 of a modern engine, how deduced, 
 
 100 
 
 or efficiency of pumping engines, 
 
 387-389 
 the best recorded, of the best types 
 
 of engines, 300 
 
 Dynamical branch of mechanics, ele- 
 ments and functions of, 18 
 problems, how solved, 18 
 Dynamics, 18 
 
 principles of, 18 
 
 CARLY gas engines, 316-323 
 JC/ Economy in using steam expan- 
 sively, 244-247 
 of a steam engine, 376 
 relative chart of under, varying 
 
 loads, 299, 300 
 Effect of clearance, 181-185 
 
 too much clearance on the dia- 
 gram, illustrated, 185, 186 
 Effective horse-power, 114 
 
 motive power, reduction of gross 
 
 power to, 115 
 Efficiency or duty of pumping engines, 
 
 387-3.89 
 Elasticity, unit of, 57 
 
 --,,_ Electrical exhibition, Philadelphia, 
 
 presenting a summary of successive 1884, engine tests at, 394-4O& 
 
 improvements in the steam en- I Elements of the dynamical branch of 
 glue, 179, 180 i mechanics, 18
 
 458 
 
 INDEX. 
 
 Emery, C. E., experiments by, 293, 
 
 294 
 
 ' ' Energy, ' ' use of the term of, in engi- 
 neering works, 18, 19 
 Engine, atmospheric, 29 
 
 compound-condensing, triple-ex- 
 pansion, diagrams from, 297, 298 
 
 condensing, theoretical indicator, 
 diagrams from, 65-67 
 
 constructed by Hallette, of Arras, 
 291 
 
 continuous-expansion, 278, 279 
 
 expanding compound, curi- 
 ous form of, 273-275 
 
 difference between a condensing 
 and non-condensing, 87 
 
 disadvantages of too large an, 200- 
 203 
 
 division of the outline drawn by 
 the instrument during a revolu- 
 tion of the, 127 
 
 economy, relative, illustrated by 
 diagrams, 354~357 
 
 efficiency of the, how tested, 124 
 
 events taking place in supplying it 
 with steam, 87 
 
 friction of, 114-118 
 
 horizontal, compound-condensing, 
 triple-expansion, diagrams from, 
 298, 299 
 
 how to deduce the duty of a mod- 
 ern, 100 
 
 manner of ascertaining the abso- 
 lute horse-power of an, 99, 100 
 
 method for finding the rate of 
 
 water consumption for the, 379 
 
 of ascertaining the increase of 
 
 economy which can be gained 
 
 in an, illustrated, 194, 195 
 
 new, designed by John E. Sweet, 
 256-258 
 
 Newcomen and Cawley's, 29, 30 
 
 plain slide valve, diagram from, 
 369, 370 
 
 Porter- Allen, test of, 394-397 
 
 power, 90-93 
 
 rule for finding foot pounds raised 
 per minute by an, 92, 93 
 
 Savery's, defects of, 29 
 
 simple compound Westinghouse, 
 diagram from, 287 
 
 single valve cut-off, objection to, 
 255 
 
 standard by which to judge its 
 economy, So 
 
 straight line, 255 
 
 tests at Electrical Exhibition, 
 Philadelphia, 1884, 394-406 
 
 the Buckeye, 253 
 
 test of, 397-399 
 
 the Southward trial of, 4OI.-4O5 
 
 Engine, throttling, explanation of the 
 diminished efficiency of the, 197 
 use of the indicator for showing 
 the condition of the, with illus- 
 tration, 156-159 
 useful effect of compression in the 
 
 working of an, 137, 138 
 what its work for economical use 
 
 should be, 203 
 
 Westinghouse single valve, 258 
 Engines, automatic cut-off, 249-252 
 
 saving by, 196 
 expansion, 247-249 
 best recorded duty of the best types 
 
 of, 300 
 comparative efficiency of different, 
 
 234-236 
 
 comparison of, 189 
 compound-condensing, 287-290 
 versus simple, 281-284 
 with intermediate reservoir, or 
 
 receiver, 277-281 
 
 difference between a non-condens- 
 ing and a condensing, 116 
 double acting, 240-242 
 early compound, 290, 291 
 high-speeded, application of the 
 
 indicator in, 150, 151 
 length of cards from, 152 
 locomotive, 259, 260 
 marine and stationary, average 
 consumption of coal by, prior to 
 1860, and in 1872, 101 
 of a flouring mill, diagrams from, 
 
 350-354 
 performance of, with diagram, 
 
 299 
 
 proper terms for, 54 
 relative economy of different, 354- 
 
 37i 
 
 single acting, 236-240 
 triple-expansion, 294-299 
 
 superior economy of, 265- 
 
 297 
 English locomotives, diagrams from 
 
 one of the best build, 262-266 
 Evans, Oliver, 36 
 
 and the high-pressure steam 
 
 engine, 232 
 
 Evil of light loads, 386, 387 
 Example for use of the computation 
 
 table, with illustration, 384-386 
 Exhaust-closure, point of, 136 
 line, 132, 133 
 port, opening of, 131, 132 
 steam, communication of the, into 
 
 the condenser, 226 
 Expanding steam, exemplification of 
 
 the action of, 60-62 
 loss from, in an unjack- 
 eted cylinder, 222
 
 INDEX. 
 
 459 
 
 Expanding steam, work and action of, 
 
 with illustrations. 63-67 
 Expansion, 59-79 
 advantages of, 72 
 curve, 129-131, 187, 188 
 of indicator diagrams, 147 
 
 the steam in an imperfectly 
 protected cylinder, diagram 
 of, 212, 213 
 
 curves of indicator diagrams, 79 
 diagram of steam in a cylinder, 
 
 73-75 
 initial, 142 
 intermediate, 283 
 
 avoidance of, 285-287 
 law of, 59 
 line, undulations or waviness of 
 
 the, with illustrations, 145, 146 
 of steam, 59^-62 
 
 and its effects with equal 
 
 volumes of steam, 69-72 
 ratio or grade of, 67, 68 
 
 with the steam cut off at cer- 
 tain points of the stroke, 75 
 saving in fuel by, 76, 77 
 variable, distribution of the steam, 
 
 in working by, 248 
 and condensing, further advan- 
 tage of, 195-197 
 
 Expansive engine, especial use of the 
 steam jacket in the, 
 215, 216 
 
 non - jacketed cylinder, 
 indicator diagram 
 from, 216, 217 
 with a jacketed cylinder, 
 diagram from, 217-223 
 Explanation of .he computation table, 
 384 
 
 FACTS to which the diagrams will 
 testify, 151 
 
 Fahrenheit and Centigrade thermom- 
 eters, 422 
 
 Falling bodies, 422-424 
 First steamship to cross the ocean, 
 
 37-4 1 
 Fitch, John, attempt to propel boats by 
 
 steam by, 31 
 "Flue" boiler, 416 
 Fly-ball governor, 34 
 Foot-pound, definition of, 98 
 
 pounds raised per minute by an en- 
 gine, rule for finding, 92, 93 
 valves, 232 
 
 Force, elastic, of steam, mode of ex- 
 pressing, 54 
 how expressed, 18 
 what it is, 17 
 
 Foreign terms and units for horse- 
 power, 99 
 
 Formulae applying to bodies acted 
 upon by gravity in vacuo, 422-424 
 
 "Forward" gas engine, 339, 340 
 
 Friction in engines, 1 14-1 18 
 percentage of, 114 
 
 Fuel, computation of gain in, 77 
 saving in, by expansion, 76, 77 
 
 "Full stroke," 60 
 
 Fulton and the "Clermont," 37 
 
 Functions of the dynamical branch of 
 mechanics, 18 
 
 Further advantage of variable expan- 
 sion and condensing, 195-197 
 
 GAGE, vacuum, 119-123 
 Gages, vacuum, 55 
 
 different construction of, 
 
 119 
 Gain in fuel, computation of, 77 
 
 of expanding steam by cutting off 
 its supply after the piston has 
 travelled a portion of the stroke, 
 
 77 
 
 Galileo, Descartes and Kepler, 26 
 Galileo's sarcasm on Toricelli's dis- 
 covery, 27 
 
 Gas and steam engine efficiency, 348 
 vapor, difference between, 162 
 calculation of amounts of, required 
 by gas engines, 314 
 relationship between the pressure 
 and the volume of a, with illus- 
 tration, 163, 164 
 
 Gases, conditions under which Boyle's 
 and Mariotte's law holds good with 
 all, 164, 165 
 Gas engine, diagrams from a five horse 
 
 Otto, 321, 322 
 error in calculating the efficiency 
 
 of the, 315, 316 
 future of the, 347, 348 
 Otto's "silent," 320-323 
 twin-cylinder, 341, 342 
 self-starting, 340, 341 
 the Atkinson, 331-339 
 
 patent "Cycle," trial of, 
 
 334-339 
 
 "Clerk," 324-327 
 "Forward," 339, 340 
 "Stockport," 327-331 
 theory of the, 312-316 
 engines, 310-348 
 
 advantages of, 312 
 
 calculation of the amounts of 
 gas required by, 314 
 
 early, 316-323 
 recognition of the value of, 317 
 
 history of, 310-312 
 
 types of, 313 
 motors, early, classification of, 316, 
 
 317
 
 460 
 
 INDEX. 
 
 Genevois, experiment by, 36 
 
 Geometry of the indicator diagram, 
 159, 160 
 
 Glasco de Garoy, exhibition of a steam- 
 boat by, 25 
 
 Grade or ratio of expansion, 67, 68 
 
 "Great Western" and the "Sirius," 
 37,38 
 
 Greene, Noble T., engine invented by, 
 251 
 
 Gross power, reduction of effective 
 motive power to, 115 
 
 Guericke, Otto von, invention of the 
 air pump by, 28 
 
 HALLETTE, of Arras, engine con- 
 structed by, 291 
 Heat and work, 42-58 
 
 equivalency of one unit of, 43 
 latent, definition of, 51 
 
 of liquefaction, 44 
 materiality of, 42 
 of chemical combination and latent 
 
 heat, 56 
 percentage of, converted into work, 
 
 by modern engines, 63 
 quantities of, required to convert 
 equal quantities of water into 
 steam, 48 
 
 specific, definition of, 58 
 unit of, 57, 58 
 units of, generated by a pound of 
 
 carbon, 43 
 required for heating one pound 
 
 of water, 5 1 
 what is the product of, 17 
 
 the space occupied by it repre- 
 sents, 17 
 
 Hero, apparatus described by, 20, 22, 23 
 Hero's book of 200 B. C., translated 
 
 edition of, 20 
 "Fountain," 20 
 " Spiritalia, " translated by Giv- 
 
 vanni Batista Porta, 23. 
 High and low pressure steam, 54 
 
 pressure engine, loss occurring in, 
 illustrated, 201 
 steam, 232-234, 417 
 Him, G. A., 36 
 
 Historical data referring to compound 
 steam engines, 269, 270 
 
 relating to the steam en- 
 engine, 33-37 
 History and adventures of the S. S. 
 
 "Savannah," 38-40 
 of gas engines, 310-312 
 Horizontal flue boiler, 419 
 Hornblower, Jonathan, patent obtained 
 by, for using two cylinders, 268, 
 
 Hornblower, the inventor of the dou- 
 ble or compound cylinder engine, 
 232 
 Horse-power, 94-123, 405 
 
 absolute, of an engine, how as- 
 certained, 99, ico 
 by the indicator, 102-105 
 commercial, 97 
 constant, rule for finding, 70, 
 
 constants, 425-427 
 
 for single cylinder engines, 
 
 table of, 425, 426 
 definition of, 94 
 effective, 114 
 
 foreign terms and units for, 99 
 gross indicated, how found, 120 
 indicated, 114 
 
 how to calculate the, 103, 104 
 most convenient way of calcu- 
 lating the, 70 
 nominal and actual, definition 
 
 of, 97 
 
 of a Corliss engine by the in- 
 dicator, with illustration, 
 102-104 
 
 of a steam engine, 9498 
 meaning of an indicated, 43 
 real, 94 
 Watt's practical experiments 
 
 relating to a, 95 
 rule for, 99 
 what it meant in Watt's time, 
 
 96, 97 
 Hot well, 232 
 
 delivery valves, 232 
 How to calculate the amount of steam 
 (water) consumed from an indi- 
 cator diagram, 376-379 
 to divide a line into a number of 
 equal spaces, with illustration, 
 105-107 
 to fix the clearance line when not 
 
 known, illustrated, 200 
 to lay out the hyperbolic curve 
 from the point of cut-off, illus- 
 trated, 199 
 Hugon, priority of invention of 
 Lenoir's gas engine claimed by, 
 
 Hulls, Jonathan, idea of steam navi- 
 gation set forth by, 33 
 Huyghens, motor designed by, 317 
 Hyperbola, application of a, to a dia- 
 gram, 1 88 
 
 Hyperbolic curve, how to lay it out 
 from the point of cut-off, illus- 
 trated, 199 
 logarithms, 68, 69 
 table of, 68, 69 
 or isothermic cards, 167
 
 INDEX. 
 
 461 
 
 ICE, melting point of, 422 
 specific gravity of, 44 
 Ideal diagram, an, with illustration, 
 
 124, 125 
 
 Incrustation of boilers, 419-421 
 Indicated horse-power, 114 
 
 how to calculate the, 103, 
 
 104 
 
 Indicating an engine, precautions in, 79 
 Indicator, the, 80-84, 4 1 1-413 
 best forms of, 83 
 co-efficient, 72 
 construction of the, 82-84 
 diagram, causes which influence 
 
 the form of, 408-410 
 from a Cornish pumping en- 
 
 gine, 238 
 
 from an expansive engine with 
 
 a jacketed cylinder, 217-223 
 
 with a non-jacketed 
 
 cylinder, 216, 217 
 from a Tandem engine, 272 
 from a unique compound en- 
 
 gine, 299 
 
 the geometry of the, 159, 160 
 uses of the, 81 
 
 diagrams, comparative, 189-207 
 correct, 148-161 
 distorted, 374, 375 
 essentials for their correctness, 
 
 148 
 expansion curve of, 147 
 
 curves of, 79 
 
 from a Buckeye automatic en- 
 gine, 254 
 
 Webb compound locomo- 
 tive, 304, 305 
 
 Worsdell compound locomo- 
 tive, 308 
 
 length of, 151, 152 
 theoretical, from a condensing 
 
 engine, 65-67 
 with illustrations, 152-156 
 functions of the, 78 
 the proper place to attach the, 149- 
 
 151 
 
 use of the, for showing the con- 
 dition of the engine, with 
 illustration, 156-159 
 in discovering defects in the 
 
 machinery, 81 
 
 Indicators in general use, 413-416 
 Initial and mean effective pressure in 
 
 the cylinder, table of, 73 
 expansion, 142 
 pressure, 141 
 Injection orifice, area of, 226 
 
 water, amount of, required, 229 
 Intermediate expansion, avoidance of, 
 
 285-287 
 receiver, effect of, 277, 278 
 
 Inventions made by accident, 30 
 Isothermal curve, 198 
 Isothermic or hyperbolic cards, 167 
 curve, 167 
 
 JACKETING with exhaust steam, 220 
 Jet condensation, how discovered, 
 
 30 
 
 condenser, 33, 226-230 
 Johnson, gas engine patented by, 317 
 Jouffrey, Marquis de, 36 
 Joule and Mayer, labors of, 42 
 
 effects of surface condensation ob- 
 tained by, 227 
 
 17 EITHMANN, priority of invention 
 1\ of Lenoir's gas engine claimed 
 
 by, 318 
 
 Kepler, Galileo and Descartes, 26 
 Kopp's experiments on the density of 
 water, 433, 434 
 
 [ AMINATION of steam, 143 
 L/ Latent heat and the heat of chem- 
 ical combination, 56 
 and total heat in water from 32 
 
 degrees, 52, 435 
 heat, definition of, 51 
 of liquefaction, 44 
 of steam, 51, 52, 445 
 units of heat, work accom- 
 plished by, 52 
 
 Lavoisier and Cavendish's investiga- 
 tions of water, 43 
 Law of Boyle and Mariotte, 129 
 
 as usually expressed, 164 
 conditions under which 
 it holds good with all 
 gases, 164, 165 
 of expansion, 59 
 
 Laws which are the key to the problem 
 of converting the work of combustion, 
 into power, 35 
 Lead, 139, 140 
 inside, 139 
 
 of a value, definition of, 139 
 outside, 139 
 
 Leakage, effect of, how detected, 130 
 of steam engines as shown by dia- 
 gram, 372, 374 
 
 the change of form of the expan- 
 sion curve due to, 79 
 Leavitt, E. D. Jr., consumption of coal 
 per indicated horse-power per hour 
 by, 101 
 
 Lebon, Franzose, gas engine invented 
 by, 317
 
 INDEX. 
 
 Length of indicator diagrams, 151, 152 
 unit of, 57 
 
 Lenoir and Hugon gas engines, 311 
 gas engine.diagrams from a, 318,319 
 gas-motor, unscrupulous claims 
 
 made for the, 317, 318 
 
 of 
 tested, 318 
 
 Lenoir's priority 
 
 invention con- 
 
 Leupold, high-pressure engine with two 
 
 cylinders, proposed by, 33 
 Lever, swinging, illustrated, 391 
 Liberating valve gear, 248 
 
 the reasoning of the ad- 
 
 vocates of, 248 
 
 Lifting condensing water, 230, 231 
 Line, atmospheric, 125 
 
 how drawn on diagrams, 119 
 clearance, 126, 127 
 how to divide a, into a number of 
 equal spaces, with illustration, 
 105-107 
 
 of admission, 128 
 back pressure, 135 
 boiler pressure, 1 26 
 
 how drawn on diagrams for 
 
 non-condensing engines, 121 
 
 compression or cushioning, 136- 
 
 139 
 
 counter pressure, 133-135 
 exhaust, 132, 133 
 expansion, undulations or wavi- 
 ness of, with illustrations, 145, 
 146 
 perfect vacuum, 125, 126 
 
 how it should be drawn on 
 
 diagrams, 119 
 steam, 128, 129 
 Liquefaction, 282 
 
 of solids, 49 
 Livingston, Chancellor, projects of, 
 
 with steam, 37 
 Load, 260-266 
 
 Loads, light, evils of, 386, 387 
 Locomotive engine, diagram from a, 
 when running, slow, 259 
 wire drawing in the, 143, 
 
 144 
 engines, 259, 260 
 
 lead in. 139 
 
 freight, diagrams from, 362, 363 
 M. Mallet's diagrams from, 302, 303 
 No. 51, Southern Pacific Railroad, 
 
 diagrams from, 365-367 
 passenger, diagrams from, 361, 362 
 steam carriage, model of, by 
 
 Nathan Read, 32 
 Locomotives, American, fair average 
 
 of the performance of, 260-262 
 compound, 300-309 
 general interest of diagrams from, 
 363 
 
 Locomotives, what may be learned 
 from diagrams from, 364 
 
 Logarithms, hyperbolic, 68, 69 
 
 Lord, George W., of Philadelphia, high 
 reputation of the boiler compound 
 of, 421 
 
 Loss from the want of the steam jacket, 
 210-212 
 
 Low and high pressure steam, 54 
 
 pressure diagram, values of, 283, 
 284 
 
 Lynedock, Lord, present to Capt. Rog- 
 ers by, 40 
 
 MACHINE for raising water, de- 
 scribed by De Caus, 25 
 for raising water invented by Porta, 
 
 described and illustrated, 24 
 measurement of power, required 
 by a single, among many run- 
 ning, 104, 105 
 
 Machinery, use of the indicator in dis- 
 covering defects in, 81 
 Magic lantern, invention of, 23 
 Mallet, M. Anatole, system of com- 
 pound locomotives of, 302, 303 
 Man -power, 98-100 
 
 Marine engines, average consumption 
 of coal by, prior to 1860 and in 
 1872, 101 
 
 jacketing of, 208 
 pressure on the boiler of, 234 
 Mariotte and Boyle curve applied to 
 the expansion of 
 steam, with illus- 
 tration, 187, 188 
 Boyle's law, 129, 162 
 as usually expressed, 164 
 condition under which 
 it holds good with all 
 gases, 164, 165 
 deviation from, 177 
 Mayer and Joule, labors of, 42 
 Mean card (Buckeye engine), 399, 400 
 Mean effective and initial pressure in 
 
 the cylinder, table of, 73 
 indicator card, 406 
 pressure, 141 
 
 definition of, 383 
 what it is, 355 
 pressure, 67 
 
 above the atmosphere during 
 
 the stroke, how found, 120 
 of expanding steam, table of, 
 
 450 
 Mercury in pounds, and vacuum in 
 
 inches, table of, 113 
 Meux's brewery, engine erected in, 
 
 in 1806, 233 
 Miller, experiments by, 36
 
 INDEX. 
 
 463 
 
 Miscellaneous, 372-410 
 Momentum, uiiit of, 57 
 Money, unit of, 57 
 
 Morandiere, M. Jules, attempt at com- 
 pounding locomotives by, 301, 302 
 Most economical point of cut-off, 62, 
 
 63 
 Motion, reduction of, 390-394 
 
 \] EWCOMEN and Cawley's engine, 
 
 IN 29, 30 
 
 the first steam engine in Eng- 
 land made by, 33 
 Newcomen's atmospheric engine, with 
 
 illustration, 234-236 
 Nicholson, John, system of compound 
 
 locomotives due to, 300, 301 
 Nominal horse-power, definition of, 97 
 Non-condensing and condensing en- 
 gine, difference between a, 87 
 
 engines, difference 
 
 between, 116 
 
 automatic cut-off engines, 24 7 
 Corliss engine, diagram from, 250 
 engine, diagram from, 359 
 engines, back-pressure in, 115, 116 
 loss in, 252 
 variation in the excess of the 
 
 back-pressure in, 134, 135 
 throt'ling engine, diagram from, 
 
 245 
 
 Nystrom, J. W., analysis of Kopp's ex- 
 periments, by, 434 
 method of measuring water de- 
 livered into a reservoir, suggested 
 by, 388, 389 
 
 OBJECTIONS to the compound en- 
 gine by engineers, 292 
 Otto and Langen, atmospheric gas en- 
 gine, 319, 320 
 
 gas engine, 311 
 Otto's improvements in gas engines, 
 
 S" 
 
 " silent " gas engine, 311,312,320- 
 
 3 2 3 
 new, motor, cost of working of, 323 
 
 distinct features of, 323 
 twin-cylinder gas engine, 341, 34 2 
 
 PAINE, Thomas, 36 
 Papin, introduction of steam ma- 
 chine by, 33 
 motor designed by, 317 
 recognition of the advantages of 
 
 steam by, 29 
 
 the condensation of steam for the 
 production of a vacuum first 
 suggested by, 28 
 
 Parallel motion devices, how to attach. 
 
 393 
 Paris and Orleans Railway, alteration 
 
 of express locomotives of, 303 
 Pascal, experiment by, 27 
 
 the truth of Toricelli's position de- 
 monstrated by, 27 
 Pennsylvania Railroad, importation of 
 a Webb compound locomotive by 
 the, 304 
 
 " Periods of distribution," 88 
 Petroleum engine, Spiel's, 342-344 
 "Piston displacement," what it is, 103 
 how to obtain the reducing motion 
 
 of the, 148, 149 
 
 mean effective, indicated pressure 
 acting on the, during one stroke, 
 9 2 
 
 the, of an engine, how it works, 86 
 Planimeter, the, with illustration, 107, 
 
 108 
 
 directions for using the, with il- 
 lustrations, 108-114 
 "Plug frame" and valve gear, origin 
 
 of, 31 
 Point of cut-off, 129 
 
 exhaust closure, 136 
 release, or opening of the ex- 
 haust port, 131, 132 
 Porta, description of inventions by, 23 
 Giovanni Batista, machine for 
 raising water by, described 
 and illustrated, 24 
 translation of Hero's "Spirit- 
 
 alia," by, 23 
 
 Portable furnace, tubular boiler, in- 
 vented by Nathan Read, 32 
 Porter-Allen engine, diagrams from, 
 
 253, 395, 396 
 lead in, 139 
 table of pressures of, 396, 
 
 397 
 
 test of, 394-397 
 Porter, Charles T., diagram taken by, 
 
 364 
 
 tribute to, 253 
 
 Positive motion cut-off engines, 253 
 Potter, Humphrey, improvement to the 
 
 steam engine by, 30, 31 
 Power, effective, motive, reduction of 
 
 gross power to, 115 
 expended in working an air-pump, 
 
 horse-power as a unit of, 98, 99 
 man-power as a unit of, 98 
 method of computing, 427 
 of a boiler, 422 
 
 an engine, exemplified by au in- 
 dicator diagram, 91-93 
 engine, way of ascertaining 
 the, 90
 
 464 
 
 INDEX. 
 
 Power or work, unit of, 57 
 
 required by a single machine 
 among many running in a fac- 
 tory, measurement of, 104, 105 
 simplest example of expenditure 
 
 of, 83 
 standard of, adopted by James 
 
 Watt, 94 
 what it is, 18 
 
 the product of, 98 
 "Precursor" locomotive, diagrams 
 
 from, 262-266 
 Pressure, absolute, 54-56 
 
 or total, definition of, 55, 56 
 atmospheric, 49 
 at the end of the stroke, rule for 
 
 finding the, 78 
 average, per square inch, how 
 
 found, 1 20 
 effective, mean, an approximation 
 
 to, 407, 408 
 initial, 141 
 
 and mean effective, in the 
 
 cylinder, table of, 73 
 in the condenser, cause of, 133, 
 
 134 
 mean, 67 
 
 above the atmosphere during 
 
 the stroke, how found, 120 
 computation of, 75, 76 
 effective, 141 
 
 definition of, 383 
 indicated, acting on the 
 piston during one stroke, 
 92 
 of a card or diagram, best way 
 
 of finding the, 105 
 of condensation, 133, 160 
 steam in cylinder or steam ex- 
 pansion curves, 162-188 
 terminal, 78, 141 
 
 definition of, 383 
 rule for finding, 76 
 Priestley's discovery in relation to 
 
 water, 43 
 
 Priming or boiler disturbance, 419 
 Principles of the dynamical branch of 
 
 mechanics, 18 
 relating to clearance, 185 
 Progress, commencement of, with the 
 appearance of Descartes, Kepler and 
 Galileo, 26 
 Proper place to attach the indicator, 
 
 149-151 
 Properties of steam, 444, 445 
 
 tables of, 446-449 
 of water, 434, 435 
 
 tables of, 436-442 
 and steam, 433-450 
 
 Pulley, the "Brumbo," illustrated, 
 391-393 
 
 Pumping engine, diagram from, 360 
 engines, duty of Cornish, 35 
 
 efficiency or duty of, 387-389 
 history of Cornish, 35 
 remarkable examples of the appli- 
 cation of the single-acting en- 
 gines to, 237 
 
 Puy de Dome, Pascal's experiment on 
 the summit of, 27 
 
 RATIO or grade of expansion, 67, 
 68 
 
 Read, Nathan, invention of a portable 
 furnace tubular boiler, and con- 
 struction of a model of a loco- 
 motive steam carriage, by, 32 
 invention of a steamboat by, 31, 
 
 3 2 
 
 patent to, before the establishment 
 of patent laws in the United 
 States, 32 
 
 Real diagram, how drawn, 176 
 Reaumur thermometer, 422 
 Reducing motion, 390394 
 Regnault, on the law of Mariotte, 162 
 Relation between the pressure and vol- 
 ume of saturated steam, as shown by 
 the indicator diagram, 175-180 
 Relative economy of different engines, 
 
 354-371 
 
 volume, what is meant by, 175 
 Release, point of, 131, 132 
 Resistance, general standard of, 84 
 Rogers, Moses, captain of the "Sa- 
 vannah," 38 
 Rule for finding foot pounds raised per 
 
 minute by an engine, 92, 93 
 the horse-power constant, 70, 71 
 the increase of efficiency arising 
 from using steam expansively, 
 75 
 
 the mean pressure, 67 
 the pressure at the end of the 
 
 stroke, 78 
 
 Rumford, experiments of, 42 
 Rumsay, James, attempt to propel 
 
 boats by steam by, 31 
 Rupert, Prince, attempt to propel a boat 
 by steam by, 32, 33 
 
 ST. CLAIR DEVILLE, experiments 
 on the decomposition of water by. 
 
 3 J 5 
 
 Samuel, J., compound locomotives in- 
 troduced by, 300 
 Saturated space, definition of, 50 
 
 steam, definition of, 46 
 "Savannah," the, the first steamship 
 to cross the ocean, 38
 
 INDEX. 
 
 465 
 
 " Savannah," history and adventures of 
 
 the, 38-40 
 
 Savery's engine, defects of, 29 
 Savery, Thomas, apparatus invented 
 
 by, 26 
 first practical application of steam 
 
 power by, 33 
 
 patents for the first application of 
 the steam engine granted to, 33 
 Saving in fuel by expansion, 76-78 
 Scotch express train, average speed of, 
 
 304 
 
 average weight of, 266 
 Self-starting gas engine, 340, 341 
 Shifting valve, 228 
 Sickles, F. E., and the liberating valve 
 
 gear, 248 
 
 Simple and compound system, 270, 271 
 Single-acting engines, 236-240 
 
 interpretation of dia- 
 grams taken from, 238- 
 240 
 
 cylinder engine, rule for finding the 
 indicated horse-power 
 of a, 102 
 
 table of horse - power 
 
 constants for, 425, 426 
 
 valve cut-off engine, objection to, 
 
 255 
 straight line engine, diagrams 
 
 from, 255, 256 
 "Sirius" and the "Great Western," 
 
 37,38 
 Smeaton's early engines, consumption 
 
 of coal by, 101 
 
 Smeaton, the real horse-power by, 94 
 Solids, liquefaction of, 49 
 Southern Pacific Railroad, diagrams 
 
 from locomotive No. 51, of, 365-367 
 Southwark engine, diagrams from, 403, 
 
 404 
 table of pressures of, 403, 
 
 404 
 
 trial of, 401-405 
 
 Space, what it is the product of, 18 
 Specific gravity, unit of, 58 
 heat, 204 
 
 definition of, 58 
 volume, what is meant by, 176 
 Speed, high rotative, effect of, 252 
 Speeds, high rotative, fundamental 
 
 principle of, 207 
 
 Spiel's petroleum engine, 342-344 
 Stationary engine, development of a 
 
 horse-power by a, 234 
 engines, average consumption of 
 coal by, prior to 1860, and in 
 1872, 101 
 
 power shown by the frictional 
 diagrams, how calculated, with 
 illustrations, 121, 122 
 
 30 
 
 Steam, 47, 48 
 
 absolute pressure of, how meas- 
 ured, 55 
 
 action of the, in an automatic con- 
 densing engine, with di- 
 gram, 254 
 
 in the cylinder of a steam en- 
 gine, 85-93 
 
 as shown by the indica- 
 tor diagrams, with il- 
 lustration, 88-90 
 when expanded, 72, 73 
 admission, regulation of, 140 
 and water, law of temperatures of, 
 
 48. 
 
 properties of, 433-450 
 bubbles, formation of, in a liquid,53 
 computation of the mean pressure 
 
 of, 75. 7 6 
 condensation of, 53 
 
 for the production of a vacuum, 
 
 first suggestion of, 28 
 condition of, used to propel en- 
 
 gines, 59 
 contraction of, under ordinary 
 
 pressure, 28 
 
 criterion of the efficiency of, 1 24 
 definition of, 47 
 density of, 48 
 
 diagram of the action of, in an ex- 
 pansive engine, 209 
 diagrams showing the action of, in 
 a steam-engine cylinder, 124-147 
 distribution of, in working by var- 
 iable expansion, 248 
 dry and wet, 53 
 economy in using expansively, 244- 
 
 247 
 
 elasticity of, 48 
 events taking place in supplying 
 
 an engine with, 87 
 exemplification of the action of 
 
 expanding, 60-62 
 expanding, work and action of, 
 
 with illustrations, 63-67 
 expansion of, 59-62 
 
 and its effects with equal vol- 
 umes of steam, 69-72 
 curves or pressure of steam 
 
 in cylinder, 162-188 
 first notice of the power of, on 
 
 record, 25 
 for the jacket, 220 
 form of, 443 
 high pressure, 417 
 how to ascertain the weight of, 378 
 (water), how to calculate the 
 amount of, consumed, from an 
 indicator diagram, 376-379 
 in a cylinder, expansion diagram 
 of, 73-75
 
 466 
 
 INDEX. 
 
 Steam in the jacket, work done by the, 
 
 222 
 
 lamination of, 143 
 latent heat of, 51, 52, 445 
 low and high-pressure, 54 
 mode of expressing the elastic 
 
 force of, 54 
 
 object of the expansive use of, 242 
 of zero pressure, 54 
 offices to be performed by the, 
 
 upon entering the cylinder, 292, 
 
 293 
 
 or aqueous vapor, 50, 51, 443, 444 
 pressure of, in Cornish engines, 
 
 233 
 
 properties of, 444, 445 
 saturated, definition of, 46 
 
 relation between the pressure 
 and volume of, as shown by 
 the indicator diagram, 175- 
 180 
 
 specific gravity of, 48 
 super-heated, definition of, 46 
 table of mean pressure of expand- 
 ing, 450 
 
 tables of properties of, 446-449 
 theoretical action of, in compound 
 engines, 281 
 
 gain by the expansion of, 75, 
 
 76 
 
 throttled, definition of, 142 
 throttling of, 53, 54 
 true nature of, not known by the 
 
 ancients, 21 
 various losses of, 78 
 volume of, on what it depends, 
 
 48 
 
 weight of a cubic foot of, 48 
 wire drawing of the, 86 
 work done by the, how calculated, 
 
 17 
 Steamboat, exhibition of a, in 1543, 25 
 
 the first ever built, 32 
 Steamboats, attempt at, by Prince 
 
 Rupert, 32, 33 
 
 first attempt at, in America, 31 
 Steam-cylinder, conditions of, in prac- 
 tice, 208, 209 
 engine, action of the steam in the 
 
 cylinder of a, 85-93 
 and gas efficiency, 348 
 automatic, 242, 243 
 commencement of the true 
 
 germ of the, 28 
 cylinder, diagrams showing 
 the action of steam in a, 
 124-147 
 
 condensation in, 204-207 
 diagrams presenting a sum- 
 mary of successive improve- 
 ments in the, 179, 180 
 
 Steam cylinder, economy of a, 376 
 
 principles of, 244 
 first perfect, 36 
 historical data relating to the, 
 
 33-37 
 
 horse-power of a, 94-98 
 the, an invention of the ijth 
 
 century, 25 
 what it is, 17-19 
 who invented the, 20-41 
 engines, classification of, 224, 225 
 compound, 266-276 
 key to the sources of loss in, 
 
 205 
 leakage of, , as shown by the 
 
 diagram, 372-374 
 varieties of, 224-309 
 Steamers, early, plying upon the Gi- 
 
 ronde and Garonne, 290 
 "Steam-fountain," described and illus- 
 trated, 24 
 
 Steam-jacket, diminution of loss on 
 
 the outside of the, 218 
 
 economy secured by the use of 
 
 the, 223 
 
 especial use of, in the expan- 
 sive engine, 215, 216 
 extension in the use of the, 220 
 loss from the want of the, 210- 
 
 212 
 
 real advantage of, 218, 219 
 value of, 207 
 Steam-jackets, 208-223 
 Steam-line, 128, 129 
 Steam-power, first practical application 
 
 of. 33 
 first useful application on a large 
 
 scale of, 25, 26 
 Steamship, the first to cross the ocean, 
 
 37-41 
 Steel vs. iron, 417, 418 
 
 plates, why preferred for boilers, 
 
 418 
 
 Stevens, Col. John, builder of the "Sa- 
 vannah," 38 
 
 General, experiments by, 36, 37 
 "Stockport" gas engine, 327-331 
 Straight line engine, 255 
 Street, Robert, gas engine patented by, 
 
 3 J 7 
 Superheated steam, 418, 419 
 
 co-efficient of expansion 
 
 of, 50 
 
 definition of, 46 
 Surface condensation, 227 
 
 condenser, 33 
 Sweet, John E., new engine designed 
 
 by, 256-258 
 the straight line engine designed 
 
 by, 2 55 
 Swinging lever, illustrated, 391
 
 INDEX. 
 
 467 
 
 System, compound, advantage claimed 
 for, 279, 280 
 
 disadvantages of, 280, 281 
 
 TABLE of areas and circumferences 
 of circles, 428-433 
 of horse-power constants for single 
 
 cylinder engines, 425, 426 
 of hyperbolic logarithms, 68, 69 
 of initial and mean effective pres- 
 sure in the cylinder, 73 
 of mean pressure of expanding 
 
 steam, 450 
 of mercury in pounds, and vacuum 
 
 in inches, 118 
 
 of temperatures with their corre- 
 sponding pressures, 177 
 Tables of properties of steam, 446-449 
 of the properties of water, 436-442 
 Tabor indicator, with illustrations, 414, 
 
 415 
 Tandem engine, indicator diagram 
 
 from, 272 
 Temperature, mean, of the cylinder, 
 
 how influenced, 130 
 of boiling liquid, 53 
 of the boiling point, 443 
 of the condenser, 226, 227 
 unit of, 57 
 
 variation of, in the cylinder, 205,206 
 Temperatures, table of, with their cor- 
 responding pressures, 177 
 Terminal pressure, 78, 141 
 
 definition of, 383 
 rule for finding, 76 
 what it is, 355 
 Test of the Buckeye engine, 397-399 
 
 Porter-Allen engine, 394-397 
 Theoretical diagram, 283, 286 
 
 construction of a, with il- 
 lustration, 191193 
 how to construct it geo- 
 metrically, illustrated, 
 197-199 
 of a compound condensing 
 
 engine, 286, 287 
 with illustrations, 169-175 
 gain by the expansion of steam, 
 
 75, ?6 
 Thermo-dynamics, basis of the science 
 
 of, 42 
 
 Thermometers, conversion of degrees 
 Fahrenheit into degrees Centigrade, 
 or vice versa, 422 
 Thompson indicator, with illustrations, 
 
 J. W., the Buckeye engine designed 
 
 by, 253 
 
 Throttled engine, explanation of di- 
 minished power of, 243 
 
 Throttled steam, definition of, 142 
 Throttling and wire drawing, 142-145 
 engine, explanation of the dimin- 
 ished efficiency of the, 197 
 governor, the ordinary, a nuisance, 
 
 J 43 
 
 loss caused by, 144, 145 
 of steam, 53, 54 
 
 Time, the minute as a unit of, 90 
 unit of, 57 
 what it is, 18 
 
 Toricelli, experiments on the weight 
 and pressure of the atmosphere 
 
 by, 26 
 
 momentous importance of his dis- 
 covery, 28 
 
 opposition to his demonstration of 
 the pressure of the atmosphere, 27 
 Tredgold's error regarding the steam- 
 jacket, 215 
 
 Tremtsuk, C. A., work by, 290 
 Trial of the Southwark engine, 401-405 
 Triple expansion engines, 294-299 
 
 superior economy of, 295-297 
 Tyndall, investigations of aqueous 
 vapor by, 293 
 
 T TNDERHILL, A. B., opinion on 
 
 U compound engines by, 309 
 
 Undulations or wavmess of the expan- 
 sion line, with illustrations, 145, 146 
 
 Unit of heat, equivalency of, 43 
 
 Units, 56-58 
 
 of heat generated by a pound of 
 carbon, 43 
 
 Upright automatic cut-off engine, dia- 
 grams from, 375 
 
 Use of the indicator for showing the 
 condition of the engine, with illus- 
 tration, 156-159 
 
 VACUUM, approximation to a, how 
 effected, 117 
 
 first suggestion for its production 
 by the condensation of steam, 28 
 gages, 119-123 
 
 different constructions of, 119 
 graduation, etc., of, 55 
 how regarded by some people, 54 
 in inches, and mercury in pounds, 
 
 table of, 118 
 in the condenser, 226 
 liability to a double interpretation 
 
 of the term, 86 
 line of perfect, 125, 126 
 
 how it should be drawn on 
 
 diagrams, 119 
 
 Valve, definition of the lead of a, 139 
 gear and "plug frame," origin of, 31
 
 468 
 
 INDEX. 
 
 Valve gear, liberating, the reasoning of 
 
 the advocates of, 248 
 motion, improvement of, in mod- 
 ern engines, with illustration, 246 
 Vapor and gas, difference between, 162 
 Vapors, 49, 50 
 
 use of the pressure of, by the 
 
 Egyptian priests, 23 
 Varieties of steam-engines, 224-509 
 Velocity, what it is, 18 
 Volume of water, 52, 433, 434 
 unit of, 57 
 
 WASTEFUL diagrams due to bad 
 valve setting, illustrated, 109, no 
 Waste-water pipe, 232 
 Water, 43-45 
 
 accounted for by indicator cards, 
 
 406 
 and steam, law of temperatures of, 
 
 48 
 
 properties of, 433-450 
 boiling point of, 45, 422 
 
 on what it depends, 51 
 circumstances on which the weight 
 
 of, evaporated in a given time 
 
 depends, 50 
 constituents of, which cause boiler 
 
 incrustation, 420, 421 
 consumption, computation of the 
 
 economy of, 379, 380 
 Dalton's experimental results on 
 
 the evaporation of, below the 
 
 boiling point, 44 
 decomposition of, 315 
 delivered into a reservoir, measure- 
 ment of, 388, 389 
 density of, 44, 433, 434 
 for steam engine purposes^ how 
 
 freed from air, 117 
 greatest density or smallest volume 
 
 of, 52 
 latent and total heat in, from 32 
 
 degrees, 52, 435 
 loss of, by condensation, 376 
 machine for raising, described and 
 
 illustrated, 24 
 
 by De Caus, 25 
 properties of, 434, 435 
 rate of expansion of, 58 
 removal of, from condensers, 227, 
 
 228 
 
 specific heat of, 45 
 standing in ponds or wells, 230 
 tables of properties of, 436-442 
 temperature of the gaseous state of, 
 
 45 
 
 vaporization of, 44 
 various conditions of, 48 
 volume of, 52, 433, 434 
 
 Water, weight of a cubic foot of, 48 
 
 Water-gas, Dowson's, 344-348 
 
 Watt, James, catalogue of inventions 
 
 and discoveries by, 33-36 
 endeavor to eliminate alternate 
 heating and cooling by, 214 
 mode of calculating the power 
 
 of his engine, of, 96, 97 
 practical experiments relating 
 
 to a horse-power, 95 
 rule for horse-power, of, 99 
 standard of power adopted by, 
 
 tribute to, 41 
 and Boulton's double-action rotary 
 
 engines, 37 
 Waviness of the expansion line, with 
 
 illustrations, 145, 146 
 Webb compound locomotive, indicator 
 
 diagrams from, 304, 305 
 Francis W., improved compound 
 locomotive designed and pat- 
 ented by, 303, 304 
 Weight, unit of, 57 
 
 Westinghouse compound condensing 
 engine, diagram from, 
 287 
 
 engine, table of actual 
 steam consumed per 
 indicated h. p., 288 
 engine, lead in, 139 
 single valve engine, 258 
 Wet and dry steam, 53 
 What the steam engine is, 17-19 
 Who invented the steam engine ? 20-41 
 Wire drawing and throttling, 142-145 
 cause of, 143 
 definition of, 142 
 in the locomotive engine, 143, 144 
 loss caused by, 144, 145 
 of the steam, 86 
 Woodcroft, Bennet, translated edition 
 
 of Hero's book by, 20 
 Woolf, Arthur, patent for improve- 
 ments in steam engines taken 
 out by, 233 
 peculiar theories entertained by, 
 
 233 
 Worcester, Marquis of, application of 
 
 steam-power by, 25, 26 
 experiments on the appli- 
 cation of steam power 
 for propelling vessels, 32 
 Work accomplished by latent units of 
 
 heat, 52 
 and action of expanding steam, 
 
 63-67 
 
 and heat, 42-58 
 
 done by the steam in the jacket, 222 
 greatest quantity of, obtained in 
 practice, 169
 
 INDEX. 
 
 469 
 
 Work, measurement of, 98 
 
 of the steam, how calculated, 17 
 or power, unit of, 57 
 what it is the product of, 18, 98 
 Worsdell compound locomotive, indi- 
 cator diagrams from, 398 
 T. W., compound locomotive 
 patented by. 305-309 
 
 Worthington, H. R., data of, from con- 
 tract trial with Belmont Water 
 Works, 389 
 
 pumping engine at Belmont, Phil- 
 adelphia, diagrams from, 367, 
 368 
 
 Wright. Mr., gas engine invented by, 
 317
 
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 HENRY CAREY BAIRD & CO/S CATALOGUE. 19 
 
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 Illustrated 1.9
 
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 TURNING : Specimens of Fancy Turning Executed on the 
 
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 With Geometric, Oval, and Eccentric Chucks, and Elliptical Cutting 
 
 Frame. By an Amateur. Illustrated by 30 exquisite Photographs.
 
 HENRY CAREY BAIRB & CO.'S CATALOGUE. 27 
 
 VAILE. Galvanized- Iron Cornice-Worker's Manual: 
 Containing Instructions in Laying out the Different Mitres aad 
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 Tables of Weights, Areas and Circumferences of Circles, and other 
 Matter calculated to Benefit the Trade. By CHARLES A. VAILE. 
 Illustrated by twenty-one plates. 4to $5.00 
 
 VILLE. On Artificial Manures : 
 
 Their Chemical Selection and Scientific Application to Agriculture. 
 A series of Lectures given at the Experimental Farm at Vincennes, 
 during 1867 and 1874-75. By M. GEORGES VILLE. Translated and 
 Edited by WILLIAM CROOKES, F. R. S. Illustrated by thirty-one 
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 VILLE. The School of Chemical Manures : 
 Or, Elementary Principles in the Use of Fertilizing Agents. From 
 the French of M. GEO. VILLE, by A. A. FESQUET, Chemist and En- 
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 WAHNSCHAFFE. A Guide to the Scientific Examination 
 
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 WARE. The Sugar Beet. 
 
 , Including a History of the Beet Sugar Industry in Europe, Varietier 
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 WATSON. A Manual of the Hand-Lathe : 
 
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 WATSON. The Modern Practice of American Machinists and 
 
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 HENRY CAREY BAIRD & CO.'S CATALOGUE. 39 
 
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 WATT. The Art of Soap Making: 
 
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 WEATHERLY. Treatise on the Art of Boiling Sugar, Crys- 
 
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 *35 
 
 WILSON. A Treatise on Steam Boilers : 
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 WOHLER. A Hand-Book of Mineral Analysis : 
 
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 HENRY CAREY BAIRD & CO.'S CATALOGUE. 31 
 
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 POSSELT. Technology of Textile Design : 
 
 Being a Practical Treatise on the Construction and Application of 
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 POSSELT. The Jacquard Machine Analysed and Explained: 
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 I2IT10 $1.OO
 
 32 HENRY CAREY BAIRD & CO.'S CATALOGUE. 
 
 RICHARDSON. Practical Blacksmithing : 
 
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