IHRsHH mm .-n_ri_nj REESE LIBRARY OF THE UNIVERSITY OF CALIFORNIA. MAR 23.1894 ..:, -t8 9 . Class No.. STREET RAILWAY MOTORS. STREET RAILWAY MOTORS: WITH DESCRIPTIONS AND COST OF PLANTS AND OPERATION OF THE VARIOUS SYSTEMS IN USE OB PROPOSED FOR MOTIVE POWER ON STREET RAILWAYS. BY HERMAN HAUPT, C. E. CHIEF OP BUREAU OF MILITARY RAILROADS DURING THE LATE WAR ; LATE CHIEF ENGINEER PENNSYLVANIA R. R. ; GENERAL MANAGER NORTHERN PACIFIC R. R. ; PIEDMONT AIR LINE ; CHIEF ENGINEER TIDE WATER PIPE LINE. fc JNJVEKSIT1 PHILADELPHIA: HENRY CAREY BAIRD & CO. INDUSTRIAL PUBLISHERS, BOOKSELLERS AND IMPORTERS, 810 WALNUT STREET. LONDON: E. & F. N. SPON, 125 STRAND. 1893. BY HERMAN HAUPT. 1893. PRINTED AT THE COLLINS PRINTING HOUSE, 705 Jayne Street, PHILADELPHIA, U. S. A. PREFACE. THE present age seems to be peculiarly prolific in the invention of motors for street railways and in new applications of old and recognized motor forces for propulsion of the cars used for urban and suburban transit. Some of these possess decided merits, and present claims for the support of capitalists and of the public that are, at least, worthy of careful examination ; others are advanced by parties who are evidently igno- rant of the ther mo-dynamic, chemical, and mechanical laws upon which some of these operations depend, and schemes are sometimes presented that are visionary and impracticable. A brief review of the plans proposed for street railways, their merits and defects, with the cost of plant and of operation, will probably possess sufficient interest at the present time to excuse the preparation and publication of this volume. The aim of the writer has not been to furnish an elaborate treatise requiring for its comprehension a high degree of technical knowledge, but rather a simple state- ment of principles and their applications that will be VI PREFACE. readily comprehended by persons of limited scientific attainments a treatise for the use and information of investors and of the public. The subjects here considered are horse railroads, steam motors, cable traction, electric roads, com- pressed-air motors, ammonia motors, hot-water motors, gas motors, and carbonic-acid motors. It is not proposed to attempt any details of mechani- cal construction or furnish illustrations. This ground has been fully covered by several volumes already published. The object is simply to give results, with such simple explanations of principles as will be of interest and be intelligible to practical men who may be called upon to contribute capital for construction or use their votes or influence in favor of any proposed system of rapid or local transit in cities. PHILADELPHIA, March 25, 1893. ADDRESS. As frequent inquiries are made for the address of the author, it may be well to state that his permanent summer residence is at St. Paul, Minn. Communications may be addressed as follows : H. HAUPT, 593 Holly Avenue, St. Paul, Minn. or care of L. M. HAUPT, 107 N. 35th St., Philadelphia, Pa. CONTENTS. I. HORSE RAILWAYS. PAGE Cost of plant, Second Avenue Railroad . . . . 1 Expenses of operation . . . . . . . 2 Other expenses ; Car-mile expenses . .' . . ' 3 Operating expenses of sixteen companies; Data given by Charles H. Davis . .' .' .'./. . 4 Data from census bulletin ...... 4. . . 5 Data from West End Company; Statement of Mr. H. H. Windsor 6 Cost of horse-power . . . . ..... 7 II. STEAM MOTORS. Properties and composition of water ..... 8 Thermornetrical and other units ; Specific heat ... 9 Air required for combustion ; Thermal units and evapora- tion 10 Evaporation in locomotives ; Consumption of coal per square foot of grate 11 Consumption of steam per horse-power; Horse-power re- quired to propel a street motor . . . -. .12 Consumption of coal per mile run ; Cost and number of motors required . . . . . . . .13 Repairs and depreciation of motors . . . 15 Plant required for six miles of double track . . .16 Cost of operation of six miles of double track . . .17 Vlll CONTENTS. III. AMMONIA MOTOR. PAGE Properties of ammonia . . . . . . .17 Ammonia motor of Dr. Emile Lamm ; Force dependent on heat, not on element employed . . . . .19 Power from ammonia capable of subdivision ... 20 Boiling-point of fluid unimportant in production of power . 21 Ammonia engine abandoned by Dr. Lamm ; Reasons for abandonment given by General Beauregard . . .22 Description of Lamm's ammonia engine . . . .23 Tests by General Beauregard ; Cost and time of distillation 24 Estimate of cost of operation by committee ; Observations on estimate of committee ...... 25 Second estimate on different basis ; Revival of ammonia motor in New York 26 Dimensions of New York motor ; Claims of New York com- pany . . . . . . . . .27 IV. THE HOT-WATER MOTOR. Otherwise designated fireless locomotive ; Upon what the efficacy depends ........ 28 Table of temperatures and pressures ; Sum of latent and sensible heat not constant . . . . .29 Water cooled by conversion of a portion into steam . . 30 Table of temperatures, pressures, volumes, and thermal units; Illustration of use of table . . . . .31 Description of, dimensions and operation of fireless locomotive 32 Explanation of difficulty in operation ; Test of another hot- water motor ......... 33 The term fireless inappropriate . . . , . .34 Extent to which water is cooled by evaporation ... 35 Possible length of run of motor by hot water alone ; Cost of plant and of operation of ammonia and hot-water motors 36 V. GAS MOTORS. Distinction between gas and other motors . . . .37 Thermal units utilized in steam and gas engines ; Increased efficiency from direct application . . . . .38 CONTENTS. IX PAGE Twenty gas motors ordered in Chicago ; Description of the Connelly gas motor .",..'*._ . . . . 39 Cost of operation of Connelly motor ; Two forms of motor proposed, and cost . ". . . . . .41 Remarks on gas motors ~. '. , , . ^ . . . 42 Consumption and cost of fuel . '.'.. . . . 43 Continuous motion of machinery required .... 44 VI. THE PNEUMATIC on COMPRESSED AIR MOTOR. Reference to investigation in 1879 44 Cost of compressed air one-fourth that of steam in motors ; Air the cheapest power for street railways ; Can be trans- mitted without serious loss . . . . . .45 Properties of air . , . . . . . . 46 Isothermal and adiabatic compression ; Heat lost is less at high than at low pressure . . . . . .47 Increase of temperature with adiabatic compression . . 48 Improvements in air compressors ; Loss of pressure by trans- mission through pipes ; Use of compressed air in France, England, and Germany . . . ... . 49 Percentage of efficiency obtained ; Cubic feet of air per horse-power ; Coal required for reheating in Paris ; Rule by which to estimate loss of pressure in transmission of air 50 Initial density not to be considered ; Cost of hydraulic pipes 51 Quantity of free air required for street motors . . . 52 Capacity of reservoir . . . . . . . 53 High pressures useful only for increase of storage capacity ; Loss in coal from high compression, one mill per mile . 54 Increase of work possible if high pressure could be utilized ; Loss of power by wire drawing ..... 56 Hardie's tests with high pressures . . . . .57 Beaumont's tests with high pressures .... 58 Beaumont's table of experimental data .... 59 Discussion of Beaumont's tests; Advantages of cylinder ex- pansion beyond certain limits only theoretical . . . 60 X CONTENTS. VII. TESTS OF THE HARDIE COMPRESSED AIR MOTOR. PAGE Five motors run on Second Avenue Railroad, New York ; Motors designed by Robert Hardie . . . .61' Observations in regard to air compression . . . .62 No loss in compressing air measured by cost of power . 63 Coal required for one horse-power in air compression ; Cost of compressed air one- fourth that of steam for motors . 64 Pressure of air in car reservoirs ; Pressure at which air is used in motor cylinders ; Air heated before admitted to cylinders ; Increase in volume of dry air by heating . 65 Additional increase in volume from moisture ; Proof that power is doubled by heating air ; Reducing valve . . 66 Cost per mile of heating the air ; Miles run by the pneumatic motor . . ... . . 67 Actual performance in excess of theoretical limits ; Explana- tion found in use of suction valves ; Cylinders acting as air pumps and brakes ........ 68 Quantity of air restored on down grades ; H eat and cold by compression and expansion 70 Description of Delamater air compressors ; Air cooled by water-tanks; Air dried by passing through water . . 71 Frost formed at low pressures only ; Suggestion in regard to use of air for power ....... 72 Effect of rupture of air cylinder ; Grades overcome by motors; Power of motor cylinders .... 73 Traction of trains ........ 75 Traction of motors, twenty-five pounds per ton ; Grades . 76 Power of motor with full cylinder of air ; Small five-ton in- dependent motors 77 Traction of trail cars . . . . . . .78 Reservoirs of air in trail cars ; Application of air motors to elevated railroads ; Power to replace motors when de- railed . . . . . . . . .79 Horse-power of the Hardie motor ; Minor points in favor of air motor ......... 80 Objections considered . . . . . . .81 Location of power plant ; Use and distribution of reservoirs 83 CONTENTS. XI PAGE Location of compressor plant on extended lines ; Use of in- termediate reservoirs ; Operation of ordinary railroads by compressed air . ' ^ * .. .... 8f> Direct experiments with the Hardie, motor ... 86 Discussion of results of tests . ''.-". -' ... 89 Loss of thermal units in tank by heating air ... 92 Suggestion for use of petroleum stove for reheating ; Hardie's estimate of cost of reheating ...... 93 Increase of power by steam from reheating tank . . 94 VIII. ECONOMICAL MODES OF COMPRESSION. Statement of Mr. E. Hill, of Norwalk Iron Company . 94 Horse-power required for compression . . . 96 Frost from expansion of air . . . . . .97 Less frost from high than from low pressure . '. .98 Explanation of observed facts ; General ignorance in regard to the use of compressed air . . . . .99 IX. COST OF OPERATION OF THE COMPRESSED AIR MOTOR FOR ONE DAY Six MILES DOUBLE TRACK. Data given . . . . . . . . .100 Cost of plant for six miles of double track ; Cost of street construction ; Cost of equipment ; Summary of cost of plant 101 Cost of operation; Compressed air for elevated railroads; Elevated railroad motor constructed by the Baldwin Com- pany 102 Report of tests on elevated railroad, by Charles W. Potter . 103 Quantity of free air required 104 Storage pressure and horse-power required . . .105 Average coal consumption in the steam motors used ; Saving in cost of labor ; Saving in cost of fuel .... 106 Cost of compressor plant ; Why compressed air is not in general use ......... 107 Mr. Hardie's explanation of causes 108 New plans prepared Ill XI 1 CONTENTS. X. OTHER AIR MOTORS. PAGE Some of them misnamed not really air motors ; Power communicated by rotating pipe . . . . .111 Atmospheric railway a failure 112 A new motor on similar principle proposed . . .113 XI. CABLE AND ELECTRIC ROADS. Comparisons difficult from unreliable data . . . .114 Data assumed as basis of comparison . . . . .115 Extracts from various sources of cost of operation . .116 Estimates of cost from uniform data . . . . .121 Cost of plant and of operation of horse railroads . .122 Cable roads, notes on, from Fairchild's " Street Railways" 123 Rules for estimating power at central station . . .124 Cost of plant and of operation of cable road . . .125 XII. ELECTRIC LINES. Table of horse-power required at axles . . . .128 Electric traction efficiency ; Cost of items in electric railroad construction and equipment . . . . . .129 Cost of power on electric lines ; Summary of expenses, by Crosby and Hall 130 Expenses of the West End Railroad, Boston ; Cost of plant and of operation of electric railroads .... 131 General summary ; Cost of plant and of operation of six miles by horse-power . . . ;-.-.. . .133 Cost of plant and of operation of six miles by steam ; Cost of plant and of operation of six miles by ammonia . .134 By hot water ; Cost of plant and of operation of six miles by gas motors --.... ,.-.. 135 By compressed air . . . . . ji : .. ... 136 Cost of plant and of operation of six miles by cable and by electric lines . . . ... .... . .137 CONTENTS. Xlll XIII. LOW-PRESSURE AIR MOTORS. PAGE Objection to cable and electric lines ; Carbonic acid motor . 139 XIV. STORAGE BATTERIES. Conditions required in a perfect motor . . . .141 Comparison of motors table of relative cost of operation and of plant ; Remarks on the ammonia motor . . 142 Horse-power; Compressed air ...... 143 Gas motors ......... 144 Steam and hot- water motors ; Electric lines ; Cable lines . 145 The aim in reviewing the various street railway systems . 146 XV. COST OF CARBONIC ACID AS A MOTIVE POWER. Cost of carbonic acid, as stated in an article in the New York World ; Over-estimation of the power of carbonic acid; Cost of sulphuric acid . . .* . . . 147 The highest pressure at which steam, air, or gas can be used to advantage upon the piston of an engine ; Thermal units developed by one pound of coal in combustion . .148 Air the only gas suitable for compression as a motive power 149 XVI. TRANSMISSION OF POWER BY MEANS OF PIPES. Importance of losses in transmission . . . . .149 No loss by condensation in transmitting air ; Law defining the relations between water and any elastic fluid . .150 Discharge of fluids through orifices ; Limitation of the appli- cation of the formula for gravity . . . . .151 Mr. R. D. Napier's experiments on steam ; Velocity of steam escaping from an orifice . . . . .152 Constancy of the velocity and of the weight of steam ; Re- sistance of long pipes to the flow of elastic fluids ; Experi- ments on the friction of air . . . . . .153 Experiments at the Mt. Cenis tunnel . . . . .154 Peculiarity observable in using tables for the friction of elastic fluids through pipes, and its explanation . .155 XIV CONTENTS. PAGE Demonstration of the law of the discharge of elastic fluids through long pipes ; Fundamental law on which the solu- tion of all problems relating to steam transmission must depend . . . . . . . . . .157 Experiments of Mr. Holly and Mr. Gaskill . . .163 Friction of air in pipes, as determined from the experiments at the Mt. Cenis tunnel ; Loss of tension per 1000 metres of pipe 165 Table giving the discharge of steam at the volume of atmos- pheric tension, the corresponding water discharge under same head, diameter and length being taken as unity, and pressures varying by half atmospheres from one to ten . 167 Table of Thomas Box for the friction of air, steam, and gas in long pipes ; Formula of Weisbach for the friction of air through long pipes 168 Fallacious rule of the engineer's pocket-books regarding the discharge of air ; Pipes of equivalent resistances . .169 Formula for calculating tables of loss of head by friction . 1 70 Table of loss by friction for steam in pounds per square inch for one mile of pipe . . . . . . .172 Capacity of mains and velocity of steam ; The limit of velocity . . 173 Table of discharges of steam in cubic feet per second for a length of one hundred feet . . . . . .175 Evaporation of water under pressure ; Difference of evapora- tion under pressure . . . . . . .176 Table of evaporation . . . . . . .177 Steam required per horsepower; Usual charge per horse- power in Philadelphia . . . . . . .178 XVII. GENERAL SUMMARY. Reasons for the small amount of information given by the published reports of street railway companies . . .179 Horse-cars; Cost of feed per horse per day . '". . 181 Steam motors ; Ammonia motor . . . . . 182 CONTENTS. XV PAGE Reasons for the abandonment of the ammonia motor, as given by General Beauregard ; The hot- water motor ; The prominent feature in the hot- water system . .183 Defect of the hot-water system; Gas motors . . .184 Advantages and disadvantages of gas motors . . .185 President Yerkes on the result of experiments with motors ; Pneumatic and compressed air motors ; Advantages of the pneumatic motor . . . . . . . .186 A peculiar feature of the Hardie motor ; Test of the Hardie pneumatic motors on the Second Avenue street railroad, New York, in 1879 . .188 Reasons for the failure of the adoption of the Ilardie system 189 Expiration of the old patents . . . . . .190 Amount of air required to run the Hardie motor . .191 Improvements in compressors ; Facilities of making addi- tions to the plant ; Electric motors ; Objection to the trolley system in cities . . . . . . .192 The electric system of the city of Richmond . . .193 The cable system ; Advantages of independent motors over any cable system .194 Description of a motor examined in 1879, which was evi- dently a fraud 195 The Keely motor 196 APPENDIX. Judson low-pressure air storage system ; Difference of this from other systems . . . . . . .199 Claims of the Judson Company identical with those of the Hardie motor of 1879 ; Estimate of the Judson system . 200 Electric steam motor . . . . . . . 202 INDEX 205 STREET RAILWAY MOTORS. i. HORSE RAILWAYS. HORSE RAILWAYS, as also all other railways operated by independent motors, require merely a surface track, the cost of which may vary from $5000 to $40,000 per mile of single track ; $5000 supposes a light 45-pound rail laid on cross-ties, very light grading, and no paving. Such a track might suit for a suburban extension of a city line in a sparsely-settled district. A more safe general average of cost will be taken at $10,000 per mile as a standard for comparison of cost of plant and operation for the various systems to be considered. It will be understood, as a matter of course, that before commencing construction a competent engineer should be employed to prepare plans, profiles, and estimates upon which the financial arrangements must be based ; but $10,000 may be taken as a fair average for surface roads, and will answer as a basis for comparison of cost of plant in the systems under consideration. COST OF PLANT. One of the reports of the Second Avenue Railroad, of New York, gave number of cars 167, number of 1 '2 STREET RAILWAY MOTORS. horses 1197, cost of cars $92,800, average cost of one car $556. The interest paid on car-shed and stable prop- erty was $24,150, representing a capital of $402,500. The length of road operated 8 miles of double track ; number of horses to one car 10. With these data the cost of plant may be approxi- mately estimated on the Second Avenue Railroad : 16 miles single track, $10,000 .... $160,000 167 cars 92,800 1197 horses, $150 179,550 Real estate, car-sheds, and stables . . . 402,500 Harness, furniture, and incidentals . . . 50,000 Cost of plant for 8 miles, based on cost of Second Avenue Railroad, of New York . $884,850 It was stated that the average cost per car was only $556. This is below the average. A new 16-foot car costs from $750 to $1500 for the body alone, and trucks about $600. In estimating the cost of new plants, there- fore, it will not be safe to allow less than $1000 per horse- car, to which the cost of horses must be added. The number of cars was given in the report as 167, but it was stated that this number included many old and comparatively useless cars, and that the average number in daily use was about 105, or only 60 per cent, of the whole number. Expenses of Operation. Repairs of harness ..*... $1,200 Horse-shoeing 16,593 Horses .42,000 Stable expenses . . . . . . 46,542 Feed 108,785 Interest and depreciation in horses, etc. . . 17,490 Interest, taxes, and insurance on stables . . 12,000 Cost of horse-power one year . . .$244,610 HORSE RAILWAYS. 3 Allowing 72 miles as the average daily run, and 105 cars in average daily use, the annual car-miles would be 2,759,400, and the cost of horse-power per car-mile would be 9 cents, exclusive of conductors, drivers, car expenses, or track repairs. The other expenses of operation were Repairs of cars $29,000 Interest and depreciation of cars . . . 9,200 Conductors and drivers ..... 167,335 Interest and repairs of car-sheds (est.) . . 16,000 Total car expenses . . . . . $221,535 Track expenses : 16 miles single track, $2932 per mile . . . $46,912 The most satisfactory unit for comparison of expenses of different systems is the car-miles, and in the case under consideration, the car-miles being taken at 2,759,400, the results are : Cost of horse-power 9 cents. Car expenses . . . . ... . 8 " Track repairs 1.68" The total expenses, including a dividend of $72,000, were $730,409, which would leave for general and incidental expenses a balance of $145,409, and the total expenses may be thus stated : Power alone . . . $244,610, per car-mile 9 cents. Cars and conductors . 221,535, " " " 8 " Track repairs . . 46,912, " " " 1.68 " General and incidental expenses . . . 145,409, " " " 5.30 " $658,466 23.98 " The total number of passengers carried on the Second Avenue Railroad for the year under consideration was 4 STREET RAILWAY MOTORS. 16,062,560, and the cost per passenger carried was 4.55 cents, which included the dividend of $72,000. Exclu- sive of dividend, the cost was 4.10 cents. From the reports of 16 horse-car companies in the city of New York, operating 102 miles of road, with 1297 cars and 10,301 horses, it appears that the expenses for one year were : Repairs of harness . . $41,861, per horse $4.06 Shoeing horses . . . 234,578, " " 22.77 Feed 1,281,316, " " 124.39 Stable expenses . . 434,014, " " 42.13 Replacing horses . . 227,693, " " 22.10 $2,219,462 $215.45 Cost of one horse one month $18, number of horses to one car 8. If the whole equipment were in daily use, running 72 miles per day for 365 days, the car mileage would amount to 34,075,000 miles, and the cost of horse-power per car-mile would be 6 J cents ; but if the same propor- tion of cars were in daily use as on the Second Avenue Railroad, the car mileage would be 20,445,000, and the cost per car-mile 10.8 cents. Charles H. Davis, C, E., gives some useful data in reference to street railways. For 45 horse railroads in Massachusetts, from 1885 ito 1890, the total average investment, real estate, road, and equipment, is given : HORSE RAILWAYS. 5 Per mile of street . ^'J'- . ' " . " . $33,406.00 " " of track . ^. . * . . $31,093.00 Car-miles per annum per mile of street . 43,345 Passengers carried per annum per mile of street . 251,816 Passengers carried per car-mile . . 5.81 Operating expenses " " . . . 24.32 cents. Interest at 6 per cent, on investments per car-mile 4.62 " Total interest and operating expenses . 28.94 " Cost per passenger carried, interest excluded 4.18 " " included 4.98 " Conditions stated by C. H. Davis, in comparative estimates : Horse-cars, 72 miles per day, running 18 hours, 4 miles per hour. Depreciation of horses, 20 per cent. ; of cars, 5 per cent. Track repairs and de- preciation, 10 per cent. 3 men per car, $1.60 each. Value of car and horses, $1900. 6 horses per car. Keep, 35 cents per day. In Rochester, the earnings of horse railways for June, 1891, were 14.37 cents per car-mile, and expenses 11.06 cents, as reported. Those of the West End Company of Boston for same time were : Earnings, 34.28 cents per car-mile ; expenses, 24.03. The number of rides per capita in cities of population from 20,000 to 30,000 is given as an average of 30, in- creasing regularly to 190 with increase of population to 800,000 or over. A census bulletin issued by Superintendent Porter gives statistics of 30 roads operated by animal power with 552 miles of track. Total cost, with equipment, $22,788,277. Operating expenses, $6,986,019. Pas- sengers carried, 190,434,783. Expenses per car-mile, 18.16 cents. Cost per passenger, 3.67 cents. 6 STREET RAILWAY MOTORS. A report of earnings and expenses of the West End Company of Boston for April, May, and June, 1892, per car-mile for horse-cars, including motive power, car repairs, damages, wages, and other expenses, gives : Cents. Earnings per car-mile . . . . . .34.28 Expenses " " 24.03 Net receipts 10.25 Another report of the West End Company for April, May, June, July, and August, 1891, gives for the horse railroad : Cents. Motive power per car-mile, average of 5 months . 10.60 Car repairs " " 0.56 Damages " " 0.30 Conductors and drivers . . . . .8.22 Other expenses ....... 4.77 Total expenses .24.50 Earnings 35.20 Net earnings per mile 10.71 Mr. H. H. Windsor, editor of Street Railway Re- view, of Chicago, in reply to a private letter, states that there is a difficulty in procuring reliable informa- tion in regard to statistics of horse railway companies, arising from the fact that there is no general, uniform system of accounts such as prevails amongst railroads ; but that for the year 1890 he has his own figures, com- piled while secretary of the Chicago City Eailway, and which show all the expenses except interest and divi- dend, being 21.98 cents per car-mile for horse roads. Since that time the cost of horse-power has increased, owing to increased cost of feed, and for the last year the total expenses have been 24 cents. HORSE RAILWAYS. 7 The most important datum, in comparison of cost of operation of the different systems, is the power required for propulsion ; and its cost per car-mile, from the data furnished, would appear to be, with horses for the power alone, exclusive of conductors, drivers, or other expenses outside the stables, from 9 to 10 cents per car-mile. The total expenses for horse service appear to be nearly uniform at about 24 cents per car-mile. In a comparison of expenses of operation between horse-power and other motors, it will be convenient to ascertain the percentages which the several items bear to the whole motive-power expense. Per cent. Repairs of harness . . . . . . . 0.5 Horse-shoeing . . . ...... . 7.0 New horses . . ..... . 17.0 Stable expenses . . . . . . . 18.0 Feed ; . 50.0 Interest, taxes, insurance, miscellaneous . . 7.5 100.0 If the cost of horse-power per car-mile be taken at an average of 10 cents, then the cost of each of the above items will be : Repairs of harness ...... ^ mill. Horse-shoeing ...... 7 mills. New horses ....... 1.7 cents. Stable expenses 1.8 " Feed 5.0 " Other expenses . . . . . 7 mills. 10 cents. STREET RAILWAY MOTORS. II. STEAM MOTORS. STEAM MOTORS for street railways are now but little used. Wherever tried they have in general been aban- doned and some other mode of propulsion adopted. A brief consideration of steam motors, however, seems to be necessary as one of the steps in the transition to the present more popular systems, and as illustrating prin- ciples applicable to the use of other elastic fluids in other forms of motors. Water is composed of 2 volumes of hydrogen united to 1 volume of oxygen, the union forming 2 volumes of steam ; and the weight of 1 volume of steam, hydrogen being unity, is 8.98, so if air is taken as unity the den- sity of steam at atmospheric pressure will be 0.561. The maximum density of water is at 4 Centigrade, or 39.2 Fahrenheit. Below this point water expands until frozen at C. or 32 F., forming ice, and in freez- ing water expands from 1 to 1.09 of its volume. Ice melts at 32 F., and there can be no rise of tem- perature until all the ice is melted. In passing from the solid to the liquid state a given weight of water takes up, or renders latent, just so much heat as would suffice to raise the same weight of water through 79 C. or 142 F. The latent heat of water is, therefore, said to be 79 thermal units C. or 142 thermal units F. When heated to 100 C. or 212 F., in the open air STEAM MOTORS. 9 at ordinary pressure of the atmosphere at sea-level, water boils and steam is formed. In this second change of form from fluid to vapor -another large portion of heat becomes latent. The thermometer would indicate no change of temperature, but in the transformation 536 thermal Centigrade units, or 967 thermal Fahrenheit units, disappear or become latent. In scientific books and in foreign countries the Cen- tigrade thermometer and the French decimal system of weights and measures are generally used. The Centi- grade graduation makes the freezing-point 0, and the boiling-point 100. The kilogramme is used for weight, which is equivalent to 2.2047 Ibs. avoirdupois. In the Fahrenheit scale, which will hereafter be used to avoid confusion, the freezing-point is 32 and the boiling-point 212. 1 Centigrade is therefore equivalent to 1.8 Fahrenheit. The temperature at which water boils is dependent upon the pressure. Under the exhausted receiver of an air-pump, and on the tops of mountains, the boiling- point is lower, and in steam boilers, under pressure, it may be almost indefinitely increased. Other fluids boil at very different temperatures ; some of them, such as liquid ammonia, boiling at a tempera- ture much below the freezing-point of water. Specific heat is the thermal capacity of a given quan- tity of any substance, and the thermal capacity is the quantity of heat necessary to raise the temperature 1 in the absolute thermodynamic scale which commences at the theoretical zero of 460 Fahrenheit, water being taken as the unit. The specific heat of ice is 0.513, of cast-iron 0.140, of air and approximately of other gases 10 STREET RAILWAY MOTORS. under constant volume and atmospheric pressure 0.250, and of steam 0.475. The fuel required for the conversion of water into steam constitutes the principal item of expense in the conversion of heat into work, and is the most important datum in the comparison of the economical efficiency of different, systems. The fuel usually employed is coal, but in many cases petroleum has been used to great advantage. One pound of pure carbon requires 2f pounds of oxygen for perfect combustion with conversion into car- bonic acid, and this quantity of oxygen would be fur- nished by 12.2 pounds of air, the result being 13.2 pounds of gases heated by 14,544 units of heat, and giving a theoretical absolute temperature of 5150 degrees. Air at 32 F. volume 1 cubic foot, weighs 0.0807 Ib. or 12.39 cubic feet to one pound, and 12.2 Ibs. would require 151.16 cubic feet. The greatest possible evaporation of water from one pound of carbon, if all the heat-units could be utilized, would be 14.87 pounds. In practice it is not possible to introduce and distrib- ute air in the exact proportion required for perfect com- bustion, and a portion of fuel must remain unconsumed, or a portion of the heat-units expended without useful effect in heating a surplus of air. The best quality of coal should yield in combustion about 14,000 units of heat; but 13,000 would probably be nearer the ordinary average. To raise one pound of water from the ordinary tem- perature of 60 to 212 would require 152 thermal STEAM MOTORS. 11 units. To convert 1 pound of water into steam at 212 requires 967 units in addition, and to raise this steam to a pressure of 150 pounds, temperature 360, the specific heat of steam being 0.475, will require 148 x 0.475 = 70 units more, making a total of 1189 units. If 13,000 units could be utilized in 1 pound of coal, the evaporation would be 1 1 pounds of water from 60 F. ; but in ordinary practice in locomotive engines the evaporation is about 6 pounds, and in small motors even less. Steam at 150 Ibs. pressure has 3 cubic feet of volume per pound, and 6 pounds would occupy 18 cubic feet of space in the boiler. The full value of the thermal units contained in the boiler steam cannot be utilized. The exhaust in a loco- motive is always under considerable pressure, which re- duces the mechanical effect. The exhaust steam condens- ing into water loses the 967 thermal units required for its change from fluid to vapor with its 1700-fold increase of volume. There are also other losses between the boiler and the cylinders by radiation and friction, so that to calculate the useful mechanical effect in a small street motor from the number of thermal units in the boiler presents too many elements of uncertainty for the results to be relied upon. Ordinary locomotives on railroads evaporate from 20 to 150 gallons of water per mile run, the average being 40 for passenger engines and 80 for freight. The Read- ing Railroad used per ton-mile 0.31 pound for passen- ger engines and 0.11 for freight. The consumption of coal averages 80 pounds per square foot of grate surface per hour ; the evaporation 12 STREET RAILWAY MOTORS. not more than 6 pounds of water per pound of coal, or about one-half the theoretical possibility. The consumption of steam per horse-power per hour is 25 pounds, the maximum possible evaporation 600 pounds per square foot of grate surface. The evapo- ration at 6 pounds of water to 1 pound of coal and 80 pounds of coal per hour per square foot of grate would be 480 pounds, yielding 19.2 horse-power per square foot of grate surface. The horse-power required to propel an ordinary street motor operated by steam can be determined with a con- siderable degree of accuracy from observations made by the writer in 1879 on the power required to propel street motors by compressed air. In these tests the motor cylinders were 6Jx 13 inches, the number of revolutions of wheels per mile 720, the piston travel per mile in the two motor cylinders 3120 feet, the speed 6 miles per hour, the piston travel 18,120 feet per hour, the mean piston pressure 56.64 pounds per square inch on an area of 33.18 square inches, making total piston pressure 1879 pounds. ,, 18120 x 1879 170 , .. , . I hen, = 17.2, horse-power applied to 33000 x 60 piston. Wellington, in his Economic Theory of Railways, page 451, states that the consumption of steam per horse-power per hour is rarely better than 25 pounds, and often much worse. If, then, the evaporation under the pressure assumed of 150 pounds per square inch be taken at 6 pounds of water to 1 pound of coal, and if it be assumed that 17.2 horse-power in cylinders will require at least 20 horse- STEAM MOTORS. 13 power in boilers, the consumption of coal per hour would 20 x 25 be = 83 pounds, and per mile 14 pounds, which, 6 at 3 mills per pound, or $6 per ton, would be 4.2 cents per mile. For small street motors this result seems to be in excess of the true average. Steam motors should run 100 miles per day, and, allowing for repairs, 300 days in the year, or 30,000 miles. They would cost about $3000; while 10 horses to one car, running the same distance, would cost $1500 ; but as a motor with 50 per cent, increase of capacity could haul two cars and at greater speed, the number of motors required would be less than the number of cars, and the excess in the cost of motors over horses would not be very great. If a road be supposed 6 miles long, requiring a round trip of 12 miles, and a steam motor to run at 8 miles per hour, and 2-minute intervals^ the round trip would require 90 minutes, and the number of motors, without allowance for reserve, would be 45. If operated by horse-power at a speed of 4 miles per hour, and 10 horses to a car, the round trip would re- quire 3 hours ; the cost of horses would be about the same as the cost of motors, but the number of cars would be doubled. If, in consequence of municipal restrictions or other causes, the speed should be limited to 6 miles per hour, the number of motors and cars would be increased 33 per cent. Taking, as a basis of comparison, 2-minute intervals between cars, speed of horses 4 miles per hour and of motors 6 miles, and a reserve of 25 per cent., length of 14 STREET RAILWAY MOTORS. road 6 miles and round trip 12 miles, the number of cars required for horses would be 112 and for motors 75, making a saving of $37,000 in car equipment with steam motors. The reduced number of cars would reduce car repairs about J of a cent per car-mile, and conductors 1 J cents. The cost of horses would nearly balance the cost of motors, taking into consideration reduced time of round trip. Engineers would be more expensive than drivers, but the number would be less. Fuel would cost less than horse-feed. Shoeing would balance repairs. Trautwein gives the amount of coal consumed per ton- mile in ordinary passenger trains as 0.31 Ib. ; but as trac- tion on roads in good order is at least one-half as much as on street railroads per ton, the proportionate consump- tion of coal may be taken at 0.65 Ib. for steam motors. Assuming the weight of the motor at 8 tons and of the car at 5 tons, the total will be 13 tons, and the con- sumption of coal with these data about 9 pounds per mile. No data are accessible for an accurate determination of the coal consumed in a small steam motor for street service, and the foregoing estimates include many ele- ments of uncertainty. Another estimate will be at- tempted on a basis that would seem to be more reliable. The consumption of free dry air in the Hardie motor of 8 tons was found to be 720 cubic feet per mile run. One pound of steam at 212 = 27 cubic feet; 720 cubic feet = 27 pounds of steam, requiring 5 pounds of coal for 8 tons ; 13 tons would therefore require 10.6 pounds STEAM MOTOES. 15 for a train of motor and car. It will probably be safe therefore to estimate the consumption at 10.6 pounds per mile run. The motor not being suitable for carrying passengers, a weight of 13 tons is required as against 8 tons with equal carrying capacity in systems in which car and motor can be combined. The cost for coal in this system will be 2.65 cents per train-mile. The repairs of cars drawn by motors can be taken as the same cost per car-mile as by horses, which is 1J cents, and the cost per day $76.80. COST OF ENGINES. The cost of small engines is much larger in proportion to weight than the cost of large ones. Large engines cost $286 per ton of weight ; small engines from $383 to $400 per ton. An engine weighing 8 tons should cost, at this rate, $3200. The smallest mine engines manufactured at the Baldwin Locomotive Works cost $2500. REPAIR OF MOTORS. The cost of repairs on ordinary passenger engines is about 7 cents per mile run. Small engines will cost much more in proportion to weight. It is possible that the cost of repair of street motors may be covered by 4 cents per mile run. DEPRECIATION. The depreciation of motors will be taken at 15 per cent., of cars 5 per cent., of buildings 3 per cent. 16 STREET RAILWAY MOTORS. PLANT REQUIRED. Double the track-room will be required for cars and motors that would be needed for the cars alone; and repair shops will also be necessary for repairs of engines. Plant Required for 6 Miles of Double Track to be Operated by Steam Motors. Real estate, motor and car-sheds, shops and offices, 40,000 square feet land, $1.50 . . $60,000 Buildings and machinery for repairs . . 100,000 $160,000 Street Construction. 1 mile double track $20,000 9282 sq. yds. paving, $3 27,846 Cost of one mile $47,846 Cost of six miles . . . . 287,076 Rolling Stock. 75 steam motors, $3000 $225,000 75 trail cars, $1000 75,000 $300,000 Summary Cost of 6 Miles. Real estate . . . .. . . . $160,000 Track and paving . . . . ' -. . 287,076 Rolling stock . ... . . 300,000 Miscellaneous expenses . . . . . 20,000 Cost of 6 miles . . " . . . . $767,076 Cost of 1 mile . . . . . .$127,846 AMMONIA MOTOR. 17 Cost of Operation of 6 Miles Double Track For One Day With Steam Motors. 30 tons coal at $5 per ton . . * . . . $150.00 Waste, oil, and grease . - . . . . 25.00 Depreciation of plant and rolling stock . . 127.00 60 conductors, $2 120.00 60 engineers, $3 ...... 180.00 60 firemen, $1.50 90.00 Car and engine house expenses . . 42.00 Motor repairs, 5760 miles, 4 cts. . . ' . < 230.40 Car repairs ....... 76.80 Track service 16.00 Repair of track and buildings .... 60.00 Clearing track, train and shop expenses . . 25.00 Accidents 20.00 Legal and other expenses . ,. . . , 10.00 General and miscellaneous expenses . . . 50.00 5760 train-miles cost . : . . .$1222.20 Cost per car-mile ... . 21.22 cents. III. AMMONIA MOT AMMONIA, at ordinary temperaturesl^^j^ffiajient gas formed by the union of three volumes of hydrogen with one of nitrogen, condensed into two volumes. Its density is 0.596, air being 1.000. When condensed into a liquid the density is 76, water being 100. Ammonia vapor at 60 Fahrenheit gives a pressure of 100 pounds to the square inch, while water, to give an equivalent pressure, must be heated to 325 F. 2 18 STEEET RAILWAY MOTORS. The volume of ammoniacal gas under 100 Ibs. pres- sure is 980 times greater than the space occupied by its liquid, while steam under the same pressure occupies a space only 303 times greater than water. Ammonia liquefies under a pressure of 1 7 atmospheres, 250 Ibs. per square inch, at ordinary temperatures, and by cold alone at 40 below zero. At 103 F. below zero, and a pressure of 20 atmos- pheres, ammonia is condensed into a white, transparent crystalline solid, which melts at 103 F. below zero. The latent heat of ammoniacal gas is 860, that of steam being 967. The solubility of ammoniacal gas in water is remark- able. At a temperature of freezing, water will absorb more than a thousand times its volume ; at 50 F. more than 800 times, and at 70 500 times. Knight's American Mechanical Dictionary states that ammoniacal gas is condensed into a liquid at the pressure of the atmosphere at a temperature of 37.3 F., or 38.5 C. At the boiling- point of water it requires 61 atmospheres. At the freezing-point of water it requires 5 atmospheres at 70 F., a pressure of 9, and at 100 F., a pressure of 14. The same authority states that the economy of fuel to obtain a given pressure is very great, being only about one-fourth the amount required to obtain an equal pres- sure by the use of steam. As ammonia is absorbed the water becomes specifically lighter, while its volume is being augmented about one- third. As the absorption of the gas goes on, the water becomes heated and the latent heat of the gas reappears as sensible heat. It is in this property that water pos- AMMONIA MOTOR. 19 sesses, of absorbiDg so large an amount of the gas and of becoming heated while absorbing it, that the practica- bility of using ammoniacal gas as a motive power con- sists, the only agency for producing motive power being heat. In 1871 an ammoniacal motor was constructed at New Orleans by Dr. Emile Lamm. It was tested and reported upon by a committee of which General G. T. Beauregard was chairman, and the report of this com- mittee, with the accompanying statement of the inventor, Dr. Lamm, is an extremely interesting document from which much of the information here given has been derived. Dr. Lamm does not claim for ammonia the ability, with a given expenditure of heat, to produce a larger initial force than with water, but the chief advantage claimed by him appears to consist in the fact that the production of the force at a low temperature apparently allows a greater portion to be utilized. He remarks : " The experience of nearly a century since the perfection of the steam-engine has left the world in possession of one invaluable fact, that any system of mechanics, how- ever ingenious, not based on a like expenditure of fuel in the heating of liquids, while all obey the same laws of expansion, has invariably proved a failure. It can now be positively asserted that we cannot, with a given quantity of heat, obtain more force with one element than with another. We must look for improvement in the machine and not in the law. "In the various forms that matter assumes the physi- cist sees only one primary cause heat. A unit of heat added to a given weight of any substance will produce 20 STREET RAILWAY MOTORS. a like development of force in all equal weights of matter, however dissimilar in physical appearance or properties. " One holding such views could not be expected to claim for himself a discovery to supersede steam as a general agent of mechanical force. "In that most remarkable quality which water pos- sesses of being converted by heat into a medium which is as yet the cheapest of all mechanical agents, ammonia stands fully the equal of water in economy, with this difference only, that the cost of the necessary quantity of ammonia to run an engine enters as first cost, with a yearly loss of 25 per cent, to be added thereon the price of water being nominal. While ainmoniacal gas is equal in every other respect to steam, except in the first cost of the material generating it, it possesses qualities that will always insure its use as an economical power in all cases where steam, from the very nature of its production, could not be used to the same advantage. For example, the smallest steam engine necessitates a personal attend- ance but little less costly for one-horse power than for one hundred. So it is with the manufacture of ammonia for horse-cars. A still of 100 horse-power to supply 100 cars will cost but little more for attendance than a 1 horse still. But here the resemblance ceases. The large steam-engine does not allow of any division, while an -ammoniacal still of 100 horse-power can be divided into 100 ammoniacal engines without any additional expense. This is owing to the fact that ammoniacal gas can be liquefied in one single large establishment, from which the liquid can be transported at any time thereafter to any distance from the furnace which generated it, and AMMONIA MOTOR. 21 then and there be made to act upon an engine with all the pristine force of tension which was imparted to it by a fire whose ashes have been cold for months or years past. 7 ' Dr. Lamm concedes that the point at which a liquid may boil below the common temperature makes but little difference practically between the heat necessary to evapo- rate into steam a given amount of water which boils at 212 F., and one that boils at 40 minus, such as ammo- nia : the real and only difference being, comparatively, that of radiation in favor of the liquid that boils at 40 minus, and even the above difference would seem to be more apparent than real. " If it was necessary to heat ammonia or a street-car by means of a furnace, ammonia, then, would offer but little advantage over steam.' 7 It appears, therefore, that the principal advantage claimed by the inventor, Dr. Lamm, in the use of am- monia as a substitute for steam, is that only one fire at a central point will be required for all the engines on the road, the power in the shape of liquid anhydrous ammonia being bottled up for use when and as required ; also, some advantage by diminished loss of heat by radi- ation in consequence of the low temperature at which the gas is used. It is not claimed that the natural law by which a unit of heat is the equivalent of 772 foot-pounds of work can be evaded. Work done is always heat lost. The latent heat of the ammonia gas reappears in the water of condensation, less the amount expended in work, and when the aqueous solution is pumped back into the still all the lost heat must be restored by the combustion of coal. In consequence of the superior 22 STREET RAILWAY MOTORS. evaporative power of stationary as compared with small locomotive boilers, the ammonia engine should effect a large saving of fuel, if not counterbalanced by attendant disadvantages, as compared with small steam motors, but as compared with the pneumatic or other systems where the power is also generated by a large central plant, and where there is no loss by radiation or conden- sation, the advantages are not apparent. In fact, Dr. Lamm himself abandoned the ammonia engine after a short trial in favor of hot water, which was used for some years on the street roads at New Orleans, and then the company returned to mule-power. Having written to General Beauregard to ascertain the reasons for the abandonment of ammonia when the report of the committee appointed to test the invention had been so satisfactory, the General replied, under date of December 23, 1892, that no difficulty was encountered in the use of Lamm's Ammoniacal Motor ; but, while experimenting with it, Dr. Lamm discovered the " Heated Steam Motor," which he preferred as being cheaper and less troublesome, and the board of directors, of which General Beauregard was president, agreed with him. After some years a new board of directors came into control, who abandoned the hot-water motor and returned to mule-power. After twenty-one years the subject of ammonia motors appears to be again occupying public attention, and it is therefore proper that a brief description of Lamm's Am- monia Engine, as used in 1871, should be given. AMMONIA MOTOR. 23 LAMM'S AMMONIA ENGINE. The patent bears date July 19, 1870, and describes an addition to a steam-engine of water-chambers in- closing the piston-rods and valve-stem, so as to render it capable of being worked by ammoniacal gas instead of steam, without any loss of the gas, which is returned to the common tank, while the exhaust is re-absorbed by a weak solution of aqua ammonia. The second part of the invention relates to the appli- cation of liquefied ammoniacal gas, contained in a con- siderable number of iron tubes, as the liquid from which, instead of water, the motive power of the engine is de- rived. The third part relates to a weak solution of aqua am- monia, contained in a tank, in which the iron tubes are immersed, and in which, also, the exhaust pipe of the engine is made to dip near the bottom. The gas ex- hausted while the engine is working is re-absorbed by this weak solution of aqua ammonia until the solution becomes saturated. The gradual re-absorption of the gas by the weak solution causes the latent heat of the gas to re-appear. This re-transfer maintains a constant temperature within the tubes, resulting in an undimin- ished pressure from expansion of the liquefied gas, which maintains the motive power at its maximum tension. The process of liquefying the ammoniacal gas is ren- dered continuous by a fresh, concentrated solution pumped back into the boiler to replace the weak solu- tion, which is drawn off from its bottom. It is claimed that 3 pounds of coal will evaporate 3 gallons of water, while 3 pounds of coal will produce 4 24 STREET RAILWAY MOTORS. gallons of liquid gas. One gallon of water under 6J atmospheres at 320 F. = 295 volumes of steam ; one gallon of liquid gas under 6J atmospheres at 50 F. = 983 volumes of gas. In the tests made by General Beauregard 1.44 gallons of liquefied gas were consumed per mile. The weak solution put in at 15 Baume was found to weigh 23 Baume' at end of trip, having been increased by absorption of gas 8. 5 gallons of commercial aqua ammonia of solution 25 Baume can be delivered at New Orleans at 40 cents per gallon. The liquefied gas would therefore cost $2 per gallon. 73 J pounds of bituminous coal liquefied in 38 minutes 18 gallons of gas from the solution of aqua ammonia at 23 Baume. Cost of Distillation. Time, 38 Minutes. Coal, 73| Ibs. at $5 per ton .... $0.18375 One engineer, $5 per day, fireman, $2, (38') . 0.36939 Machinery, $3 per day 0.15831 Cost of liquefying 18 gallons .... 0.71145 Hence, 1 gallon would cost .... 0.039525 or, about 4 cents. 1.44 gals. = 1 mile will cost 5| cents. This estimate, based on time 38 minutes, assumes proportion of continuous operation for the whole day. Any intermission would add to the cost, and the cost, as will be seen, is very largely in excess of the cost of com- pressed air per mile run. AMMONIA MOTOR. 25 ESTIMATE FOR EUNNING 25 CARS 95 MILES EACH PER DAY. MADE BY COMMITTEE. Cost of making 3410 gallons of liquefied ammonia for 25 cars, running 2368 miles per day : Interest on plant, $15,000, at 20 per cent. . Interest on ammonia, $864, at 8 per cent. . Loss of ammonia, $864, at 25 per cent. Coal, 4.64 tons, $5 Labor . One car per day will cost ..... One mile will cost ...... or, nearly 2 cents per mile. Observation. This sum of 2 cents per car will repre- sent the cost of fuel only, and was based on the data furnished by the tests made by the committee, but Dr. Lamm states, on page 1 5 of his report, that the engine used on the car was two horse-power. This was probably an under-estimate, although the motor was no doubt a very small affair. An ordinary street steam motor should develop from 15 to 20 horse-power. 2 cents for 2 horse-power of the motor would be very nearly as ex- pensive as horse-power. If, as stated, it required 1.44 gallons of liquid ammo- nia to run the car one mile, and the cost of distillation was 4 cents per gallon, then the cost of ammonia would be 5.76 cents per mile, instead of 2 cents. The 2 cent estimate was made upon hypothetical data, and the 5.76 cents per mile was for a 2 horse-power engine. These 2G STREET RAILWAY MOTORS. estimates cannot be relied upon as a basis for calculation of expenses on a large plant. These tests must have been made under very unfavor- able conditions in regard to track and machinery, and could not have exhibited the full economic power of ammonia. Another estimate of the cost per mile run will be based upon the actual performance of the Pneumatic Motor, assuming that a cubic foot of ammonia gas, at a given pressure, will produce an equivalent mechanical effect to a cubic foot of air under the same pressure. It has been ascertained that 720 cubic feet of free air compressed to 10 atmospheres will run a motor one mile. 720 cubic feet of free air = 72 cubic feet at 10 atmospheres. 1 cubic foot of liquid ammonia = 7J gallons, at 4 cents per gallon for distillation costs 30 cents, and yields 639 cubic feet of gas under 10 atmospheres pressure. The cost of one mile, 72 cubic feet = 30 x Jfo = 3.4 cents. This allows for no losses. It is possible that 4 cents would cover the expense. This is a little below steam, which was estimated at 4.2 cents per mile run for fuel only. The Ammonia Motor has been revived by a New Jersey company operating under new patents. The writer called at the office of the company in New York, and was very courteously received by the treasurer, who referred him to the draftsman at the power-station for detailed information in regard to plans and principle of operation. The motor was not ready for exhibition, but the plans were shown of a compact, well-arranged ma- AMMONIA MOTOR. 27 chine for an independent motor of capacity sufficient for one or two cars, the dimensions of which were given as follows : Size Height, 5' 6". Length, 9 feet. Width, 6 feet, Weight, 3 tons. Horse-power, 25. Tractive force, 1300 pounds. Capacity for liquid ammonia, 44 gallons. Capacity for water, 180 gallons. Driving-wheels, 2 feet diameter. Outside connections. Motor calculated to run 14 miles with one charge. Speed, 6 miles per hour. Cost of motor as stated at office, $3200 ; at power-station, $2300. To run 1 mile with 8 tons load will require 3 gallons of anhydrous ammonia. The plant to redistill 400 gallons in 10 hours costs $3500. As this apparatus may be considered as still in the experimental stage, no data for estimates have been given. If the cost of redistillation should be as great as in the New Orleans tests the cost per mile run would be excessive, amounting to 12 cents, but it is probable that this would be greatly reduced, and the company claims the ability to redistill the ammonia at a cost of 1 cent per gallon, or J the cost at New Orleans. The claims of the company are: Great economy as compared with horse, trolley, or cable system, both in plant and in operation, which claims are probably well founded ; also, ability to run 1 mile with 3 gallons of anhydrous ammonia. Pressure, 150 pounds per square inch ; wastage, 10 per cent. A 16-foot car can run 25 miles before recharging. Cost of preparing the ammonia, 1 cent per mile. Total of all operating expenses, 7.68 cents per car-mile. The above statements are supported by record of tests 28 STREET RAILWAY MOTORS. made at Jackson Park, Chicago, April, 1892, and are given as the claims of the parties interested. The writer had no time or opportunity for verification of these claims, and no information as to the dimensions and weight of the motor in which the tests were made. From the data given in the foregoing pages in regard to the ammonia motor, and the principles upon which it operates, the reader can form his own opinions as to the probability of results verifying the claims that have been advanced. IV. THE HOT-WATER MOTOR. THIS motor, otherwise known as the fireless locomo- tive, was the successor of the ammonia engine, and was used for some years on the street railroads of New Or- leans under the name of the Angomar Motor. The efficacy of this motor depends upon the great capacity for heat of water, in consequence of which it is claimed that a sufficient quantity of energy can be stored in a reservoir to suffice for a run of ordinary length. Under the normal pressure of the atmosphere, water boils at 212 Fahrenheit; but the boiling-point may be reduced or elevated by a variation of pressure, and where pressure is reduced, the excess above the tem- perature corresponding to the reduced pressure is con- verted into steam at the same temperature with the pressure due thereto. THE HOT-WATER MOTOR. 29 The following table gives the absolute pressures, in- cluding the pressure of the atmosphere and the Fahren- heit temperatures corresponding thereto : p. T. P. T. P. T. 14.7 212 145 356 360 432 15 213 150 358 370 435 20 227 155 362 380 437 25 240 160 365 390 440 30 250 165 367 400 442 35 259 170 370 410 444 40 267 175 372 420 446 45 274 180 374 430 448 50 281 185 376 440 451 55 287 1913 378 450 453 60 293 195 381 460 455 65 298 200 383 470 457 70 303 210 387 480 459 75 307 220 390 490 461 80 312 230 394 500 463 85 316 240 398 525 466 90 320 250 401 550 471 95 324 260 404 575 476 100 328 270 407 600 480 105 331 280 411 650 488 110 335 290 413 700 495 115 338 300 416 750 502 120 341 310 419 800 508 125 344 320 422 850 515 130 347 330 424 900 521 135 350 340 427 950 526 140 353 350 430 1000 532 The latent heat of steam at 212 is 967, making the total thermal units in one pound of steam, above zero, 1179, and above the freezing-point, 1147, of Fahren- heit's scale. From this point the total units increase in a ratio determined by the formula of Regnault ; and the sum of the latent and sensible units is not a con- stant quantity, as Watts supposed it to be, and which 30 STREET RAILWAY MOTORS. opinion was for a long time assumed to be correct. The total units at 212 above zero being 1179, the increase is gradual until, at a temperature of 428, it becomes 1244, an increase of 65 units in 216. The latent heat at 428 is 816 units, instead of 967 at 212. The volume of steam at 212 is 1700 times greater than the water from which it was produced. A pound of steam at 212, under a pressure of 14.7 pounds per square inch, occupies a volume of 26.36 cubic feet. Under any greater pressure the volume will be proportionately reduced. The specific heat of water being unity, steam is 0.475. When a portion of water at a high temperature is converted into steam by reduced pressure, the remain- ing water is cooled to the extent of the thermal units required for the conversion of the water into steam a fact that appears to have been neglected in some com- putations of the length of rim of which the hot water or fireless locomotive is capable. The following table gives pressures, volumes, thermal units above 32, and latent heat corresponding to the temperatures in the first column : THE HOT-WATER MOTOR. 31 Temperature. Pressure. Volume of 1 pound. Total thermal units above 32. Latent thermal units. 212 14.7 26.36 1147 967 221 17.5 22.34 1149 960 230 20.8 19.03 1152 954 239 24.5 16.28 1155 948 248 28.83 14.00 1158 942 257 33.71 12.09 1160 935 266 39.25 10.48 1163 929 275 45.49 9.12 1165 922 284 52.52 7.97 1168 916 293 60.40 6.99 1171 910 302 69.21 6.15 1174 904 311 79.03 5.43 1177 898 320 89.86 4.81 1179 891 329 101.9 4.28 1182 885 338 115.1 3.81 1185 879 347 129.8 3.41 1188 . 873 356 145.8 3.06 1190 866 365 163.3 2.75 1193 860 374 182.4 2.48 1196 8.04 383 203.3 2.24 1199 848 392 225.9 2.03 1201 841 401 250.3 1.84 1204 835 410 276.9 1.67 1207 829 419 305.5 1.53 1210 823 428 336.3 1.39 1212 816 ^'4 As an illustration of the use of this table, suppose 10 pounds of water, at a temperature of 428 and pressure of 336 pounds per square inch, are confined in a tight vessel, and that 2 pounds are permitted to blow off into the atmosphere. The 10 pounds of water contain 4280 thermal units, and the 2 pounds converted into steam and escaping will remove 1934 units, leaving 2346 units in the re- maining 8 pounds of water, or 293 units per pound. The temperature of the 8 pounds of water will there- fore be reduced to 293 from 428, and the pressure from 336 pounds to 60 pounds per square inch. 34 STREET RAILWAY MOTORS. steam. It had sufficient grate surface to develop 18 to 20 horse-power by the combustion of coal alone in the fire-box as in an ordinary locomotive; and as the pressure increased during the run, it is evident that this effect could only be produced by the consumption of coal. The results furnished no satisfactory test of the capacity for service of hot water alone. There can be no question that if the boiler can be filled at the start with hot water under a working pressure, and well protected against radiation, a smaller quantity of coal will be required for a run of moderate length than would be required if feed water were admitted cold, and it is also certain that water can be heated in a station- ary tank more economically than in a locomotive. Another report of tests of this same engine, at another time and in a different locality, gave a run of 23 miles with trailer, using 128 pounds of coal in motor and 180 gallons of water. The pressure at starting was 175 pounds. After running 3J miles it was reduced to 155 pounds, and afterwards, at intervals, the gauge pressure was 150, 145, and 155 pounds, and at the end of the run 105 pounds. 180 gallons of water = 1350 pounds evaporated with 128 pounds of coal gives 10J pounds of water per pound of coal. As the evaporation by consumption of coal in the motor should be 6 pounds per pound of coal, it would leave the equivalent of 4J pounds to be supplied in the hot \vater from the stationary tank. The capacity of the boiler was given as 262J gallons. Many of the statements made in regard to the so- called fireless locomotives are so unreasonable that no attempt will be made to criticise them. Of course, no THE HOT-WATER MOTOR. 35 engine can be called fireless that has a fire-box, with 20 horse-power for the combustion of coal, and in which coal is used to help the run. Neither can a boiler which is of ordinary material and construction, sub- jected to a pressure of 175 pounds or upwards, either of water or steam, be considered as non-explosive. In fact, in case of rupture, a boiler filled with water at a given pressure would cause much more damage than if filled with steam at the same pressure, for the steam liberated from the water would be many times its volume. For the purpose of comparison with other motors, it will be assumed that the run is to be made entirely with hot water; and as no data have been furnished from which to calculate the loss by radiation, these losses will be omitted. The capacity of the boiler will be taken at 300 gallons = 40 cubic feet = 2500 pounds. The pressure will be taken, as given in the test, 175 pounds per square inch effective, or 189.7 absolute. Temperature, 377 F. The engine will be supposed to run until the pressure has been reduced to 60 pounds effective = 74.7 pounds absolute. Temperature, 307. The differences of temperature available for motor work, when converted into steam, would be 377 307 = 70. Let x represent the pounds evaporated to reduce the temperature from 377 to 307 ; then 2500 x will be the quantity remaining at the lower temperature, and x carries off not only the 70 of difference, but also the latent heat of 967 ; then 2500 X 377 = 307 (2500 34 STREET RAILWAY MOTORS. steam. It had sufficient grate surface to develop 18 to 20 horse-power by the combustion of coal alone in the fire-box as in an ordinary locomotive; and as the pressure increased during the run, it is evident that this effect could only be produced by the consumption of coal. The results furnished no satisfactory test of the capacity for service of hot water alone. There can be no question that if the boiler can be filled at the start with hot water under a working pressure, and well protected against radiation, a smaller quantity of coal will be required for a run of moderate length than would be required if feed water were admitted cold, and it is also certain that water can be heated in a station- ary tank more economically than in a locomotive. Another report of tests of this same engine, at another time and in a different locality, gave a run of 23 miles with trailer, using 128 pounds of coal in motor and 180 gallons of water. The pressure at starting was 175 pounds. After running 3J miles it was reduced to 155 pounds, and afterwards, at intervals, the gauge pressure was 150, 145, and 155 pounds, and at the end of the run 105 pounds. 180 gallons of water = 1350 pounds evaporated with 128 pounds of coal gives 10J pounds of water per pound of coal. As the evaporation by consumption of coal in the motor should be 6 pounds per pound of coal, it would leave the equivalent of 4J pounds to be supplied in the hot water from the stationary tank. The capacity of the boiler was given as 262J gallons. Many of the statements made in regard to the so- called fireless locomotives are so unreasonable that no attempt will be made to criticise them. Of course, no THE HOT- WATER MOTOR. 35 engine can be called tireless that has a fire-box, with 20 horse-power for the combustion of coal, and in which coal is used to help the run. Neither can a boiler which is of ordinary material and construction, sub- jected to a pressure of 175 pounds or upwards, either of water or steam, be considered as non-explosive. In fact, in case of rupture, a boiler filled with water at a given pressure would cause much more damage than if filled with steam at the same pressure, for the steam liberated from the water would be many times its volume. For the purpose of comparison with other motors, it will be assumed that the run is to be made entirely with hot water ; and as no data have been furnished from which to calculate the loss by radiation, these losses will be omitted. The capacity of the boiler will be taken at 300 gallons = 40 cubic feet = 2500 pounds. The pressure will be taken, as given in the test, 175 pounds per square inch effective, or 189.7 absolute. Temperature, 377 F. The engine will be supposed to run until the pressure has been reduced to 60 pounds effective = 74.7 pounds absolute. Temperature, 307. The differences of temperature available for motor work, when converted into steam, would be 377 307 = 70. Let x represent the pounds evaporated to reduce the temperature from 377 to 307 ; then 2500 x will be the quantity remaining at the lower temperature, and x carries off not only the 70 of difference, but also the latent heat of 967 ; then 2500 X 377 = 307 (2500 36 STREET RAILWAY MOTORS. x) 4- 1037 #. Consequently x 242 pounds con- verted into steam, and leaving 2258 pounds in boiler at the temperature of 307. 242 pounds of steam at the average effective pressure of 43 pounds per square inch = 7.2 cubic feet per pound, gives 1742 cubic feet avail- able for propulsion. The wheels were 31 inches in diameter or 8 feet in circumference. The number of revolutions per mile would be 660. The cylinders were 9 inches diameter, 10 inches stroke. Capacity of 4 cylinders, 2464 cubic inches, or 1.4 cubic feet for each revolution = 1.4 X 660= 924 cubic feet per mile. It would appear, therefore, that the hot water alone, without the aid of the fire-box, would not run the motor as much as 2 miles, since the number of cubic feet avail- able is only 1742. It is unnecessary to pursue the investigation further. Hot water alone cannot be relied upon to run a motor for a sufficient distance unless supplemented by coal combustion in a fire-box, which makes it, in fact, an ordinary steam locomotive ; and the slight saving effected by heating the water in a stationary tank is more than offset by the inconveniences attending its use. COST OF PLANT AND OF OPERATION BY THE AMMONIA AND THE HOT-WATER MOTORS. No special estimates are required on these motors. The statement made by Dr. Lamm and General Beaure- gard in reference to the ammonia motor shows that it GAS MOTORS. 37 was abandoned by its inventor and by the New Orleans Committee as less economical and more troublesome than the hot-water motor ; and the statement in regard to the hot-water motor shows that if is decidedly inferior to steam, being in fact nothing more nor less than a steam engine in which the use of steam for a short distance is obviated by the substitution of hot water in the boiler taken from a stationary tank at a high temperature. The economy cannot be superior to that of the ordinary steam locomotive, and the manipulation on a large scale would be troublesome and introduce unnecessary com- plications. Y. GAS MOTORS. IN all the ordinary forms of motors, as steam, air, electricity, cable, ammonia, or hot water, the original source of power is heat developed by the combustion of fuel, usually coal or wood, and transmitted by various agencies to the motor machinery. In this transmission losses are sustained to a greater or less extent. Steam loses by radiation and condensa- tion ; cable lines lose sixty per cent, by friction and other resistances, and utilize not more than forty per cent, in car propulsion ; electricity loses an equally large per- centage of the original power by resistance of conduc- tors and machinery ; air by the heat generated in com- pression, which cannot be utilized, but the equivalent in motive energy may be restored by reheating. There is 38 STREET RAILWAY MOTORS. also a loss to a small extent by friction of pipes in trans- mission to long distances, so that in all these cases only a portion of the thermal units developed in the com- bustion of the fuel can be actually utilized in the work accomplished. In gas engines there is no transmission of heat from a furnace to the motor cylinder with its attendant losses. The combustion is effected and the power generated in the motor cylinder itself, and the power is applied directly to the piston ; in addition to which, if the air is properly regulated so as to admit the proper proportion, the combustion can be perfect, the temperature a maxi- mum, as also the expansive force due thereto. Coal develops in perfect combustion about 14,000 thermal units ; but in a locomotive only about one-half, or 7000 units, can be utilized. The cost of coal is, at 4 dollars per ton, 2 mills per pound. Gas engines are run with gas or naphtha vapor, yield- ing in combustion about 28,000 thermal units per pound. The cost of naphtha is 5 cents per gallon. The specific gravity is 0.848, so that a gallon weighs 6.3 pounds, and the cost per pound is 8 mills. As the cost per pound of naphtha is four times as great as the cost of coal, \vhile the calorific power is also four times as great, the cost for equal units will be equal. But naphtha, with regulated admissions of air to secure perfect combustion, has another advantage. The ther- mometrical temperature is higher than with coal, and as combustion is effected inside the motor cylinder, the force of expansion and the impact upon the piston are greater than could be secured by an equal expenditure of thermal units in any other fuel, hydrogen alone ex- cepted ; but the use of hydrogen is not practicable. GAS MOTORS. 39 Gas motors have been in process of development for 6 or 8 years, and have now reached a point where the inventors claim that difficulties have been overcome, and that their efforts and expenditures have been crowned with success. Certain it is that an order has been given for 20 Connelly gas motors for street railroad use in Chicago, and one of them was nearly ready to be tested in December, 1892. The writer had the privilege of examining this machine, which appeared to be simple in construction, compact, well built, and promising satis- factory results, but without the test of experience in actual daily use for a considerable period of time, it is always unsafe to predict unqualified success in any new mechanical device. It is not to be expected that the present gas motors will be found in practice entirely perfect ; but if defects are found, remedies may be applied. There seems to be a sound principle that will in time, if not immediately, be utilized, and there can be no question that no system now in general use can compare favorably with the gas motor in the economy of fuel required for propulsion of a given weight for a given distance, within the limits of street car service. Compressed air is the only power that can secure equal or superior economy ; but this power is not in use for motor purposes except in Europe, where the results are very satisfactory, even with a motor that admits of considerable improvement in mechanical details. DESCRIPTION OF THE CONNELLY GAS MOTOR. This is a gas motor carrying its own store of fuel for a day's run, and the fuel used is the heaviest grade of 40 STREET RAILWAY MOTORS. naphtha, which will not vaporize at the temperature of the atmosphere. It is carried in a closed tank, which is again inclosed in a radiator filled with hot water con- stantly furnished by the engine cylinder. The radiator performs important double service, cooling the cylinders of the engine and warming the carburetter. The circu- lation of the water from the cylinder to the radiator and return is continuous. The inner vessel or carburetter is filled with an absorbent material, which absorbs the charge and leaves no liquid to be lost should a leak occur. Air is drawn automatically through the ab- sorbent material, thoroughly carburetted, and supplied to the engine in exact proportion to the power required. There is not the least element of danger attending the operation of this system. The gas is ignited by an electric spark. The principle of all gas engines is speed ; their speed cannot be varied like the steam engine, but they must run at a nearly uniform rate ; therefore special mechanism w'as required for transmitting power to the axle at any desired rate of speed. It was absolutely essential to complete success that this should be accomplished, and in such a manner that the speed of the car could be varied at will of the driver by moving a single lever. The mechanism employed for this important service is positive in action, noiseless, and durable. The wear- ing parts are easily, quickly, and cheaply replaced. It prevents giving shock or jar to the car w r hen starting, and, above all other advantages, transmits maximum power when driving a car at minimum rate of speed. In the transmission of power by friction, it is neces- sary that the contact pressure should vary in proportion GAS MOTORS. 41 with the power transmitted. This is accomplished auto- matically by means of a right and left screw nut, ope- rated by an eccentric extension of the hand lever, so that any movement of the lever in either direction, to vary the speed, changes the pressure of contact correspond- ingly, thus securing maximum pressure on grades or curves, and minimum when running at full speed. This is one of the most important features of the de- vice, as it would be impracticable to run at full speed with the same contact pressure that is required when starting on grades or curves. The above brief description has been furnished by the inventor. COST OF OPERATION. It is claimed by parties interested that the cost of operating this motor per day (14 hours), ninety miles each, is as follows : Cents. Fuel, 14 gallons naphtha, 5 cts. . . ... . .70 Lubrication .' . . . . . . .10 Care (one engineer to 10 motors) .... .30 Repairs ......... .30 Total cost per day ... . . . 1.40 Or 1 T 5 ^- cents per car-mile, not including driver or conductor. The motors are proposed of two forms. One an in- dependent motor designed for use on city roads where conductors are employed. These are independent motors, eight feet long, the driver standing in the centre and ope- rating the motor in either direction without changing his position. The weight is 5800 pounds, and it is said to be 42 STREET RAILWAY MOTORS. capable of hauling one standard 16-foot car heavily loaded up grades of 5 per cent. On grades not ex- ceeding 2 per cent, it can easily handle 2 cars. The maximum speed attainable is 12 miles per hour, but the gearing can be changed to secure a speed of 16 miles per hour where such speed would be allowed by the authorities. The cost of this motor is given at $2500. The combination motor has an upper deck, and can be operated with or without conductor; designed for suburban roads. The machinery occupies 6 feet of the forward end, leaving room inside for 14 passengers and for 20 on the outside. The combination motor can haul a trailer in addition on roads of 2 per cent, grades. As the gas motor has not yet passed the experimental stage, it would be rash to assert that all expectations and promises can at once be realized. That there is a future for this system seems probable, but difficulties will no doubt be experienced. The charge of air in proportion to naphtha vapor must be accurately determined and automatically regulated to admit the proper quantity ; the electrical apparatus must produce the spark for ignition at the proper moment ; the circulation from the cylinders to the carburetter must be constant, regu- lar, and of the proper temperature for vaporization. If the engine should stop for a time and the water cool, there will be delay in starting, unless the water can be discharged and the space occupied by it refilled with hot water from a stationary tank so as to secure without serious delay the temperature necessary for the evapo- ration of the naphtha. If stopped on the track by blockades or other causes, the machinery must be GAS MOTORS. 43 thrown out of gear, but the engine kept running to maintain the circulation and prevent cooling, and this will add to the consumption of fuel, the estimate having been made on the supposition of constant movement. The friction of contact with the driving disk must be sufficient to overcome resistances without stopping. Where a very large plant is required, it may possibly be found advantageous to erect apparatus to manu- facture gas and use it compressed in iron cylinders in- stead of the carburetter, in order to reduce the delays at starting to a minimum. The best that can be said of gas motors at the present time is that they promise well in the future ; but actual use on a scale of considerable magnitude will be required to de- velop defects, inconveniences, and objections, if any exist, and to inspire confidence in their economy and efficiency. Taking the data furnished by the patentee, which is 14 gallons of naphtha for a run of 14 hours in an inde- pendent motor of 5800 pounds, and assuming that the consumption of fuel must be in proportion to the weight of the train carried, and also that a trail-car of 5 tons or 10,000 pounds must be carried in addition to the motor, the weight of the train would be nearly 3 times as much as the motor itself, and the consumption of naphtha for 14 miles = 42 gallons, if the 14 gallons were required for the motor alone. It is claimed, in the description of the Connelly gas motor, that it is capable of haul- ing a passenger car in addition ; but it is not stated that this work can be done without an additional consump- tion of fuel ; but even assuming that the 1 4 gallons of naphtha will carry both the motor and car a distance of 84 miles at 6 miles per hour, the cost of fuel would be 44 STREET RAILWAY MOTORS. 8J mills per mile, which is more than the cost of fuel alone for the compressed air motor. In addition to this, it must be observed that the gas engine must continue to run, with the machinery out of gear, when the motor is standing and making no mile- age ; also that house-room must be provided for both motors and cars, as in the case of steam, which will in- crease the investment in real estate and the interest on plant. VI. THE PNEUMATIC OR COMPRESSED AIR MOTOR. AFTER an extended investigation, commenced in 1879 and continued recently, with a long interval for observa- tion of other systems, the writer is confirmed in his orig- inal conclusion that, for the operation of city and sub- urban roads whether surface, elevated, or underground no other motive power can compare favorably with compressed air, either in cost of plant, economy of ope- ration, freedom from all objections, or the possession of incidental advantages. Those who have not examined the subject almost in- variably object that double the power is required to compress air that can be utilized in actual work from the air where compressed, and assume a necessary serious loss. It may be true that double the power may be re- quired ; but suppose the air is compressed by a water- power, otherwise unemployed, that costs nothing except the first outlay for the machinery for its utilization : PNEUMATIC OR COMPRESSED AIR MOTOR. 45 might not the power be cheaper than steam, even if only 10 per cent, could be utilized ? The actual facts are that air can be compressed by the use of the best compound expansion stationary engines in which double the useful effect can be secured per pound of coal as compared with steam motors. This alone would at once place air on a par with steam ; but in stationary engines a quality of coal can be used that costs less than half as much as the coal required for locomotives, and this raises the economy of air to double that of steam in small motors. But this is not all. It has been proven by repeated tests, both in Europe and America, that the simple de- vice of passing the air through a small tank of hot water before admission to the motor cylinders again doubles the useful effect, and at the same time prevents all in- convenience from the production of frost at the exhaust, and this makes the economy 4 to 1 as compared with steam, the cost of reheating being merely nominal. In fact, air is the cheapest power that can be used for the operation of street railways, and it is one against which none of the objections that apply to other sys- tems can be urged. Why capitalists and engineers have neglected it so long is beyond comprehension. It can only be explained upon the ground of ignorance of facts from failure to investigate. Air can be transmitted to long distances without any loss by condensation or radiation, as with steam ; and the loss by friction, in pipes of proper diameter, is in- considerable, even at a distance of miles. The importance of air as a motive power for city rail- roads demands a careful consideration of its claims. 46 STEEET RAILWAY MOTORS. PROPERTIES OF AIR. Air is composed of about 23 parts by weight of oxygen and 77 parts of nitrogen. By volume the proportions are 21 of oxygen to 79 of nitrogen. At a temperature of 60 F., its weight is -g-j^- that of water ess 0.0765 Ib. per cubic foot. At a temperature of 32 12.433 cubic feet = 1 pound. The specific heat of air at constant pressure and with increasing volume is 0.23/7, water being 1. In doubling the volume of air the units of heat ex- pended are, as given by Clark, 117.18 (other authorities, 115.8). If the temperature be doubled without adding to the volume, the units expended will be 83.22. To double the volume in addition requires 33.96. Total, 117.18. The specific heat of air in raising temperature without increase of volume is 0.1688. In compressing air from a tempe^ture of 60 to one- half its volume under an effective pressure of 15 Ibs. to the square inch the temperature will be raised to 177, and the increment of temperature will be 117. But in continued compression to 30, 45, 60, 75, 90, 105, and 120 pounds the temperatures are successively 255, 317, 369, 416, 455, 490, and 524, and the suc- cessive increments 77, 62, 52, 47, 39, 35, 34. The capacity of air for holding moisture is affected by its volume and temperature., but apparently not by its density. It appears from observations made by manu- facturers of compressed plant that air compressed to 50 atmospheres contains no more water than air at the same PNEUMATIC OR COMPRESSED AIR MOTOR. 47 temperature under one atmosphere, consequently f | of the water is removed during compression, and the air becomes so dry that no frost can be formed in the ex- haust. Even when air is cooled by passing through water no additional quantity of moisture can be taken up. The compressor used on the Second Avenue Rail- road in 1879 cooled the air by passing it through a tank of water under pressure, yet no frost was formed at the exhaust. It is now considered preferable, in the most improved construction, to cool the air without direct con- tact with water. As every thermal unit is equivalent to 772 pounds* raised one foot, it is evident that if air could be c pressed without elevation of temperature and loss heat in cooling much would be gained. Something has been accomplished in this direction, but complete iso- thermal compression is unattainable. Adiabatic compres- sion, or compression attended by evolution of heat, is alone possible ; but at high pressures the loss is propor- tionately less, as has been shown, and the storage capacity of reservoirs is, by increased pressure, increased for longer runs. It was observed by Mr. G. H. Reynolds, of the Dela- mater Works, that the heat liberated in proportion to the power secured was much less at high than at low pressures. Satisfactory explanation can perhaps be given. Imagine a vessel containing one pound of air at ordinary tension 13 cubic feet, the base one square foot and height 13 feet. If, by means of a piston, this air should be forced into one-half the space, or 6J feet, the pressure would be increased to 30 pounds, and the work done would be 21,528 foot-pounds. One pound 48 STREET RAILWAY MOTORS. of water raised 1 is equivalent to 772 foot-pounds, and as the specific heat of air is 0.238, 772 x 0.238 = 184, the foot-pounds expended in heating 1 pound of air 1. Then 21,528 -*- 184 = 1 16 = the heat liberated in com- pressing one pound of air into half its volume. Now suppose the 6J cubic feet of air should be again compressed one-half, or to 3J, the final pressure would be 60 pounds, and the space 3J feet, and the work 21,528 foot-pounds as before, representing 116 of heat. But with these 116 of heat the pressure has been in- creased from 2 atmospheres to 4, and in like manner from 4 to 8, from 8 to 16, and from 16 to 32, would each require but 116, and at the end 16 atmospheres of additional pressure have liberated only as much heat as one atmosphere at the commencement; assuming that the heat when liberated has been absorbed so as to secure isothermal contraction of volume. It must be remembered, however, that if the pressure should be increased to 16 atmospheres, the volume would be diminished to y 1 ^, and if the air should be used at full pressure throughout the stroke of a piston no advantage would be gained. Very high pressures are, however, always used expansively, and if air at 500 pounds should be cut off at T *g of the stroke, the gain over an equal weight of air at 250 pounds cut off at J- would be 32 per cent. Where temperature is considered, the results are quite different. The tables for adiabatic compression give from one atmosphere to two, an increase per one atmos- phere of 115.8. At 8 atmospheres the increase is 36.1, at 10 atmospheres 30, at 15 atmospheres 25.4, and at 25 atmospheres 16.7 per atmosphere: showing PNEUMATIC OR COMPRESSED AIR MOTOR. 49 that the increase of temperature daring compression is greatest at low pressures. The largely extended use of compressed air for engi- neering purposes has led to great improvements in air compressors, and responsible parties can now be found to furnish plant and guarantee results at a very mode- rate cost, thus removing any element of uncertainty. It is claimed that the best compressors now constructed give a result about midway between the isothermal and the adiabatic, and the net loss of power due to clearance is so small as to be practically unworthy of consideration. The losses by transmission of air through pipes are comparatively slight. It has been stated by competent authority that there is not a properly designed com- pressed air installation to-day that loses over 5 per cent, by transmission alone. The largest compressed air power plant in America is that at the Chapin mines in Michigan, where the power is generated at the Quin- nesec Falls, and transmitted 3 miles. The loss of pres- sure as shown by the gauge is only 2 pounds. At the Jeddo Tunnel near Hazelton, air under 60 pounds pres- sure was conveyed 860 feet, and the gauges indicated no difference of pressure. The pipe in this case being 5f inches in diameter, was very large for the quantity of air used. The losses in compressed air, it is said, may be reduced to 20 per cent, of the power used by combining the best system of reheating with the best air compressors. In France, England, and Germany there have been erected during recent years large compressed air instal- lations. In Paris about 25,000 horse-power is trans- mitted over the city, and is used to drive engines and 4 50 STKEET RAILWAY MOTORS. for many other purposes. A small motor 4 miles from the central station can indicate in round numbers 10 H. P. for 20 H. P. at the station itself, and by combin- ing the American Compound Condensing Corliss Air Compressor with an efficient and economical reheating apparatus, and Corliss or other economical engines, an increase of efficiency of 50 per cent, may reasonably be expected. The air used in Paris is about 11 cubic feet of free air per minute per indicated horse-power. The ordinary practice in America with cold air is from 15 to 25 cubic feet per minute per indicated H. P. The engines in France were found to consume about 15 cubic feet of air per minute per H. P. without reheating. The amount of coal consumed in Paris during reheat- ing is trifling. With the reheaters commonly em- ployed, it amounts to from one to two cents per horse- power per day, and these figures, it is said, can be reduced considerably by a more economical system of reheating. In the transmission of air through pipes, the loss of pressure can be very conveniently and accurately calcu- lated by taking the loss for a given length and diameter of pipe and initial velocity, and determining the loss for any other velocity, diameter, and length, by a simple proportion, observing that the loss of pressure is Directly as the length of pipe and square of the initial velocity. The friction in 1 mile of 6-inch pipe, with an initial velocity of 20 feet per second, is 5.1 pounds per square inch. Suppose 1500 cubic feet of free air per minute, under 500 pounds pressure or 34 atmospheres, are to be carried 1 mile. What will be the loss by friction ? PNEUMATIC OR COMPRESSED AIR MOTOR. 51 1500 In this case, the initial volume will be = 44 34 cubic feet. 44 cubic feet per minute = 0.74 cubic foot per second. A pipe 6 inches in diameter has an area in square feet of 0.127. 0.74 -f- 0.127 = 6 feet per second, nearly. 6 2 Then 5.1 x - = 0.457 pound, a very inconsider- able loss in a distance of 1 mile, and the loss in 10 miles would be only 4J pounds. In this calculation the initial density of the air is not taken into consideration, and it does not affect the result with an elastic fluid of uniform density ; but a general formula, applicable to all elastic fluids, must recognize density, and the loss of pressure in elastic fluids of dif- ferent densities, other conditions the same, will be directly as the densities. The loss of pressure, for example, in the transmission of steam through pipes will be about half as great as with air, other conditions, except density, being the same. The cost of hydraulic pipes to resist high pressures has, January, 1893, been obtained from manufacturers. Cents. 3-inch pipe per lineal foot . . * -. > . 20.82 . . . . 24.61 29.26 35.25 43.51 54.87 64.84 84.90 115.78 52 STREET RAILWAY MOTORS. The quantity of air required for running an ordinary street motor of about 18 or 20 horse-power capacity, for a distance of 1 mile upon an ordinary street railway, has been positively and accurately determined by several months' service of the Hardie Motor on the Second Avenue Railroad in New York in 1879, and also by the experience in France and England. On this im- portant point there can be no mistake, and ample evi- dence can be furnished. The Hardie combined motor and car, weighing 8J tons, including passengers, ran 9f miles on a bad track on the Second Avenue Railroad. The pressure at start- ing was 360 pounds; at finish, 100 pounds and reser- voir capacity 160 cubic feet, giving the quantity of free air at atmospheric pressure expended 2.773 cubic feet = 284 cubic feet per motor-mile, or 33 J cubic feet per ton-mile. The Mekarski (French) combined motor and car, weighing 8 tons, including passengers, ran 7f miles on a street tramway with an expenditure of 36J cubic feet per ton per mile, or 292 cubic feet per car-mile. The Beaumont (English) locomotive, weighing 7 tons, is claimed by the inventor to be capable of draw- ing a 5-ton car 10 miles on a street tramway. Ca- pacity of reservoir, 100 cubic feet. Pressure at starting, 1000 pounds per square inch ; at finish, not stated, but presumably 80 pounds. This gives a total expenditure of 6.100 cubic feet of free air, or 50 cubic feet per ton per mile, or 500 cubic feet per train-mile of motor and car. The Beaumont locomotive, of same capacity and pressure, but said to be 10 tons, ran 15 miles light, PNEUMATIC OR COMPRESSED AIR MOTOR. 53 and without stopping, on a clean steam railway, using 6.100 cubic feet of free air, or 40 cubic feet per ton per mile. The Scott-Moncrieff combined motor and car, weigh- ing 7J tons, is claimed to have run 7 miles on a street tramway. Reservoir capacity, 150 cubic feet. Pressure at starting, 390 pounds (26 atmospheres); at finish, not stated, but presumably about 50 pounds, thus using 3450 cubic feet, or 67J cubic feet per ton per mile, 472 cubic feet per car-mile. It is thus seen that Hardie and Mekarski produce the best results, ow r ing to the more efficient method of heat- ing. Beaumont heats a little, and Scott-Moncrieff not at all. It thus appears from all these statements that the Hardie motor gave better results than any other, although the mechanical work was defective owing to cheap construction without the usual facilities for locomo- tive work, and the runs were over a very bad track. It is certain therefore that a consumption of 300 cubic feet of free air used in the cylinders at a pressure of 56 pounds per square inch will suffice to run the motor one mile. The reservoir in the Hardie motor had a capacity of 160 cubic feet ; but even at 130 cubic feet, and a pressure of 34 atmospheres, 500 Ibs. per square inch, the motor could run 12 miles and retain over 60 Ibs. pressure at the end of the trip. The Hardie motor when towing two cars used 480 cubic feet of air per mile. It has been found that whatever may be the pressure of air in the motor tanks beyond a certain very mode- rate excess above the working pressure, the additional 54 STREET RAILWAY MOTORS. power expended in compression cannot be made avail- able in propulsion, but is lost in wire drawing the air through the reducing valve to a lower pressure. Conse- quently all the power expended to secure high pressures in the reservoirs serves only to increase the tank capacity and the length of run. To avoid this loss, compound engines have been tried, but they are not only unsuited for small motors in con- sequence of complication, but they have failed to accom- plish the object. Another plan of utilizing the high pressure has been proposed by allowing it to escape through an injector, and thus forcing an additional volume of fresh air into the motor cylinders, reducing to that extent the draft upon the reservoir. It is not known that this plan has be^n tried, or, if tried, what has been the percentage of gain. It is, therefore, an interesting question to determine what is the actual loss in high compression measured by coal consumption per mile run. Assume as data, therefore, that a motor reservoir of 130 cubic feet capacity is to be charged once in two minutes to a pressure of 500 pounds, and determine the value of the coal consumed in raising the pressure from 250 to 500 Ibs. per square inch, which coal consumption cannot be again reproduced in work, but represents a loss. To obtain 130 cubic feet at 500 Ibs. or 34 atmos- pheres, 260 cubic feet at 17 atmospheres must be reduced in volume one-half in two minutes of time. In effecting this compression a piston with an area of one square foot, or 144 square inches, must travel 130 feet in two PNEUMATIC OR COMPRESSED AIR MOTOR. 55 minutes, with a pressure at the start of 250 pounds per square inch, at the end of 500 pounds and mean of 0.846 X 500 423 Ibs. The amount of work done in one minute is 423 X 144 130 X = 3,959,280 foot-pounds per minute = 120 2i horse-power. At 2J pounds of coal per horse-power per hour, the consumption in 2 minutes for 120 horse-power would be 10 pounds, and as this volume of air at 500 pounds will run the motor 12 miles, with a reserve in the tank at the end of the trip of 20 per cent., the actual consump- tion for the trip of the coal required for double com- pression would be but 8 pounds, costing, at $3 per ton for the cheap coal used, 1J mills per pound, or 12 mills for 12 miles, or one mill per mile run of motor. It appears, therefore, that notwithstanding the fact that high pressures cannot be directly utilized in propul- sion, the cost of producing them is so small, and the ad- vantage of increased storage capacity and increased length of run so great, that it secures great economy to use them, and it is useless to attempt to employ cumber- some mechanical devices to save so inconsiderable a loss, even if there was a prospect of success, which there is not. If air at 500 pounds could be applied directly to the piston of the motor-cylinders, and cut off at one-sixteenth of the stroke, the weight of air, or the quantity at at- mospheric tension, would be the same as if used at 250 pounds and cut off at one-eighth ; but there would be a considerable difference in the work done, as will be seen. 56 STREET RAILWAY MOTORS. The initial pressure being unity, the average at y 1 ^- is 0.236. The initial pressure being unity, the average at ^ is 0.355. Then, 500 X 0.236 = 1.180. And, 250 x 0.355 -. 0.888. These figures are in proportion to work done, and the difference is 0.292, or 32 per cent, in favor of the higher pressure if it could be utilized. But the important practical question is: What does this difference cost in money measured by coal consumed ? The data are, air per mile 300 cubic feet, 12 miles = 3600 cubic feet. Two-minute intervals = 1800 cubic feet per minute. To compress this volume requires 500 horse-power per hour, or 500 x 2J = 1250 Ibs. coal per hour. 42 pounds in 2 minutes for a run of 12 mills = 5J mills per mile, and the loss by wire draw 1.31 mills per mile. But by having 500 pounds pressure in the reservoir instead of 250, the motor can run 12 miles instead of 6, and the cost of compression from 250 pounds to 500 pounds is only one mill per mile, as shown elsewhere : therefore it is great economy to use high pressure, even if there is a loss at the reducing valve. It may be interesting to give this subject further con- sideration, and in this connection a quotation from the pamphlet of Mr. Potter becomes pertinent as an intro- duction. Referring to losses, he remarks : By far the greatest loss of all is accounted for by the " wire drawing," which takes place in reducing the storage pressure to a practicable working pressure. Let it be supposed, for illustration, that this storage PNEUMATIC OR COMPRESSED AIR MOTOR. 57 pressure is 1000 pounds to the square inch, and that it is reduced to 100 pounds in the locomotive cylinders. It may easily be computed by experts that there will be a loss in this case of over two-thirds of the power orig- inally contained in the air in its high pressure state. Experiments have been made with a view to recovering this loss by direct expansion in the locomotive cylinders, but they have utterly failed, as will now be made apparent. It seems reasonable and rational to suppose that this would be the proper way to overcome the difficulty, pro- vided that it did not entail too much complication of machinery, and it was accordingly in this manner that Hardie originally attempted it. Discarding the idea of compounding the cylinders as impracticable, owing to the complication necessarily in- volved, and other considerations, which will be referred to further on, he designed an experimental engine having two cylinders of equal dimensions and slide-valves as usual, adding cut-oif valves and other simple devices which experience had shown to be essential to the eco- nomical use of compressed air. The slide-valves were specially designed to balance the high pressure, all parts were proportioned to bear the excessive strains, and the lowest possible storage pressure for the air adopted (360 Ibs. per square inch). Upon trial this engine, which was in the form of a combined motor and car, was found to work exceedingly well, running ten miles on a street tramway with one charge of air. Indicated diagrams, taken at all initial pressures, showed the most beautiful and perfect expansion curves ; and indeed, the experiment was regarded as eminently 58 STREET RAILWAY MOTORS. satisfactory. Mr. Hardie, however, being curious to know how much greater was the efficiency by this method than by the use of a reducing valve, had one applied, and found to his great astonishment that the engine worked just as well; that is to say, that it ran as great a distance as before. The engine was carefully examined, but no defects were found, and the experi- ments were repeated with the same results. Experts were consulted to ascertain, if possible, the reason, and the only conclusion arrived at was that possibly the use of such high pressures in the engine cylinders entailed loss by excessive friction and leakage, which in practice neutralized the theoretical gain. Be that as it may, there was no disputing the facts, and Mr. Hardie, therefore, gave it up and adopted the reducing valve, there being no advantage in straining the machinery with high pressures. It appears that Colonel Beaumont, in England, has been laboring diligently to effect the same object by com- pounding the engine cylinders; but as will be seen, his experiments led to the same practical conclusions as those of Mr. Hardie. He begins by presuming that the energy stored in the high pressure air is all, or nearly all, recoverable by expansion in the motor cylinders, and hence argues that the only consideration in fixing the initial pressure is that of conveniently storing the amount of power in a given space. This, he says, is 1 00 Ibs. per square inch in a 7-ton motor having a capacity of 100 cubic feet and of hauling a 5-ton car 10 miles on a street tramway. Here follows a statement of the practical disadvan- PNEUMATIC OR COMPRESSED AIR MOTOR. 59 tage of using compound cylinders upon a street motor which it is not necessary for present purposes to repeat. Proceeding to investigate the results of the experi- ment obtained by Beaumont with such an engine, reference is made to a paper read by him on the subject before the Society of Arts and published in the journal of the Society March 18, 1881. On page 389 there is a tabular statement of experimental data, which is here reproduced. Table of Experimental Data. Air Pressure. Minutes. Pounds. 925 Ibs. run 1000 yards in 9 reduced pressure to 805 805 " " " 9 " " 730 730 " " " 9 " " 660 660 " " " 13 " " 595 595 " " " 10 " " 520 5000 yards run. Loss 405 Ibs. in 50 minutes = 3 miles 73 yards per hour. 520 Ibs. run 1000 yards in 10 reduced pressure to 435 435 " " " 10 " " 360 360 " " " 10 " " 288 288 " " " 10 " " 205 4000 yards run. Loss 315 Ibs. If instead of expanding this air freely, it were made to do useful work, from 1000 Ibs. down to 200 Ibs., and then from 200 Ibs. to atmospheric pressure, the work done, upon the whole, would reasonably be ex- pected to be greater than in the latter case alone. Hence, Beaumont's claim to having accomplished great results is readily believed, both by practical and scientific men. That no such perfection is actually obtained in practice, however, will be seen from a careful study of the table. Here let it be observed the pressures are given at the beginning and end of each 1000 yards run, 60 STREET RAILWAY MOTORS. the difference in each case being an exact measure of the quantity of air, and also, when the pressure is taken into account, a measure of the energy expended. Now let these differences be noted : - First 1000 yards Second Third Fourth Fifth Sixth Seventh Eighth Ninth used 120 Ib 75 70 65 75 85 75 72 83 From what has been said it would have been expected that as more energy is stored in the higher pressures, these figures should have shown a gradual increase, until the last was about double the first. Neglecting the first as excessive and probably due to some special cause, it is seen that the remaining 8 trips were accom- plished on practically the same quantity of air (viz. : an average of 75 Ibs. to the square inch, or 5 volumes of the reservoir capacity at atmospheric pressure), but by no means on the same expenditure of energy ; and it is particularly noticeable that the eighth trip (or last but one) was accomplished on an expenditure which was less than the average. Hence the inevitable conclusion, that if the higher pressures had been reduced to the average pressure of the eighth trip, at least as good economy would have been attained, showing clearly that Colonel Beaumont's experiments go for nothing more than to confirm Mr. Hardie's experience, and that the advan- tages claimed for cylinder expansion beyond certain limits are mostly theoretical. TESTS OF HAEDIE COMPRESSED AIR MOTOR. 61 VII. TESTS OF THE HARDIE COMPRESSED AIR MOTOR. IN 1879 the writer was called upon to investigate and report, as consulting engineer, upon the practicability and relative economy of compressed air as a motive power upon street railways. At that time five motors had been constructed for the Pneumatic Tramway Engine Company and were in daily use upon the Second Avenue Railroad in New York, by consent of its officers, but at the expense of the Pneumatic Tramway Company, which desired an opportunity of giving the invention a practical test. The motors were constructed upon plans prepared by Mr. Robert Hardie, a Scotch engineer of remarkable ability, who had been engaged with Scott Moncrieff, of Glasgow, in very successful experiments in that city. Lewis Mekarski, of Paris, had also made successful ex- periments in the same direction. The motors and also the compressor plant were con- structed at the Delamater Works in New York, but as this establishment did not make a specialty of locomo- tives and had not at that time the appliances that were necessary to secure the best results, some of the wearing parts were found to be rather soft, a fact which to some extent increased the cost of repairs, but did not discredit the plans of construction. There can, of course, be no more wear on the rubbing surfaces of a pneumatic motor, 62 STREET RAILWAY MOTORS. when properly case-hardened, than on an ordinary locomotive. The consideration of the applicability of compressed air as a motive power for street engines was taken up with no bias in its favor, and the following extracts from the report, made February 20, 1879, will give the conclusions reached after careful investigation of the motors in actual daily use. In 1856, while engaged in devising plans for the con- struction of the Hoosac Tunnel, the writer had, after careful consideration, rejected compressed air, and decided in favor of steam in connection with a vacuum system of ventilation, as more simple, economical, and effectual under the conditions then and there existing in regard to its use, limited financial resources for the purchase of plant being an important consideration. In any mode of compressing air in which the direct pressure of steam is employed, as in reciprocating pumps, a cylinder of steam unexpanded and at maximum pressure must be expended to secure under high ten- sions a small fraction of a cylinder of air at the same tension. If a number of small compressors be connected with one shaft by cranks, at such angles as to divide the cir- cumference equally, the loss of power would be reduced, or the percentage of useful effect would be increased. Suppose, for the sake of illustration, that there were ten compressors connected with one shaft, and that it was proposed to compress the air to ten atmospheres. There would be ten discharges into the receiver at each revolution, each discharge being one-tenth of a cylinder, TESTS OF HAKDIE COMPRESSED AIR MOTOR. 63 and the sum of the whole equal to one full cylinder at the proposed maximum tension. The power exerted in effecting the compression in each cylinder would be in proportion to the mean pres- sure throughout the stroke, if the air cut off at one-tenth were allowed to expand, which is 3.302 ; and if the air was not used expansively the theoretical loss without" allowance for friction would be as 3.3 to 1, and wijfh, friction fully as 5 to 1. But the air can be and is used expansively, and simple device of a fly-wheel, by which momentum can be stored up and maintain uniformity during a revolu- tion, secures equally favorable results with a small as with a large number of compressors connected with a shaft. There is no reason whatever to question the results claimed for the compressors manufactured at the Dela- mater works, and used on the Second Avenue Railroad, of 50 horse-power of compressed air, capable of being fully utilized for every 100 horse-power expended in the engine which works the compressors. But it will be said there is still a loss of one-half as compared with steam applied directly. The answer is, not in cost of power ; and in this fact is found the key to the solution of the problem. The minimum of weight is essential in a locomo- tive engine. Heavy apparatus for securing economy of fuel cannot by any possibility be applied to it. Com- pound and condensing engines are entirely inadmissible on wheels of small motors adapted to street service, but all the known economies in engines, regardless of weight, can be introduced in stationary plant, and Corliss, Dela- 64 STREET RAILWAY MOTORS. mater and others, now secure as an ordinary result a duty of one horse-power from 2J pounds of coal. At the Holly Works at Lockport, which claim an ex- ceptionally high average duty; the daily evaporation is nine pounds of water to one pound of coal under 25 pounds pressure, or seven pounds of coal to one cubic foot of water evaporated ; and in small boilers, such as are used for heating purposes, the average evaporation under ten pounds pressure is only four pounds of water per one pound of coal, or 15.7 pounds of coal per cubic foot of water evaporated. With no very reliable data to determine the consump- tion of coal and evaporation of water in ordinary street motors, it will, no doubt, be greatly in their favor to credit them with developing a horse-power with ten pounds of coal ; and the conclusion, therefore, is that although one- half the power of the stationary engine is lost in compressing air, yet the economy of fuel can be made so great that a given amount of power in com- pressed air is secured at one-half the cost of the direct application of steam to street motors. But this is not all. By the simple device of heating the air by passing it through a tank of water, it has been clearly demonstrated as the result of constant prac- tice in Paris, confirmed by recent experiments on the Second Avenue Railroad, that capacity for work is doubled, or the gain 100 per cent., making the economy of power as compared with the direct application of steam to street motors, measured as it should be, by coal consumed, four to one in favor of compressed air. Air is compressed into the car reservoirs under a pres- TESTS OF HARDIE COMPRESSED AIR MOTOR. 65 sure of 350 pounds per square inch, or 24 atmospheres, nearly. It is not applied directly to the motor cylinders at this pressure, experience having shown that the best practical results are secured at 16 atmospheres, about 240 pounds. But the air is not applied cold ; it is admitted to a tank of water placed on the front platform of the car, containing 5 cubic feet of water, drawn from a station- ary boiler, tinder 80 pounds pressure and having a tem- perature of 328. If air is admitted to the tank at 60, and leaves it at 328, the increase of temperature will be (32860) 268. To raise one pound of water from 32 to 212, or 180, requires as much heat as would raise 4.27 pounds of air through the same range. The specific heat of air as compared with water being as 0.2377 to 1, one pound of air increases in volume by heat from 12.387 cubic feet at 32 to 19.323 cubic feet at 328=6.936 cubic feet increase. The volume of air at 24 atmospheres being 1, the volume at 1 6 atmospheres would be 1.5. If the volume of air at 32 be 1, the volume at 60 will be 1.061, and at 328 =1.59. It appears, therefore, that in heating a given quantity of dry air to 328, it will be increased in volume under constant pressure over 50 per cent. This expansion is due simply to dry air; when mois- ture is present to the point of saturation the pressures are greatly increased. If the air at 30 be taken as unity, dry air at 212 5 66 STREET RAILWAY MOTORS. will occupy a volume of 1.375, and saturated air at the same temperature 2.672, or about double. Conceding that only a small part of the theoretical expansion can be realized in practice, as the air when ex- panded in the motor cylinders is cooled very rapidly and there are other losses, there is still a wide margin to justify the claim of double power from heating the air. This declaration was fully sustained by actual work on the Second Avenue Railroad, where double runs of 6J miles had been accomplished with the same expenditure of moist and heated air as single runs of 3| miles with dry air. The inevitable conclusion that results therefrom is that the power secured and utilized in air compressed with the best engines and compressors now in use costs, as compared with ordinary steam street motors, only one-fourth as much per horse-power measured by the coal actually consumed. The air is not admitted to the motor cylinder at 350 pounds pressure, but at a much lower pressure, so that after passing the tanks and becoming heated and charged with vapor, it enters the cylinders at 250 pounds, requiring but a comparatively small volume of the dry air from the reservoirs to do the work. This uniformity of pressure is secured by means of a reducing valve placed in the pipe, which acts automati- cally until the pressure is reduced below the pressure of admission. When the air has become so exhausted as to fall below 7 this pressure, the reducing valve remains fully open. If the water should be cooled down 100 degrees, the power of the heated air would be reduced, but would still retain great efficiency. TESTS OF HARDIE COMPRESSED AIR MOTOR. 67 It can, therefore, readily be understood that a very important gain results from heating the air, and the economy of the arrangement is so great that it should never be omitted. The use of a small petroleum lamp to retain a high temperature in the water would add to the efficiency. COST OF HEATING THE AIR PER MILE. To raise 5 cubic feet of water from 212 to 328 requires, as we have seen, 36,192 units, or 1251 units per mile. Allowing 8000 nnits of heat per pound of coal consumed, the coal required to heat the 5 cubic feet of water would be 36,192 8000 = 4.5 pounds, at a cost of one cent, and this is less than average duty. It would seem from the result of this calculation that fully 100 per cent, had been added to the power of the engine and to the miles run, at a cost of one cent in coal for heating the water. How MANY MILES WILL THE PNEUMATIC MOTOR RUN? The air reservoirs contain 160 cubic feet at 24 atmos- pheres. The equivalent at one atmosphere is 3840 cubic feet. Allowing one-third to be retained as reserve, there will be left to be utilized 2560 cubic feet. But in con- sequence of vapor and expansion by heat, this quantity is practically equivalent to 5120 cubic feet at the escaping tension. The number of cubic feet of air and vapor expended per mile run has already been ascertained to 68 STREET RAILWAY MOTORS. be 720 cubic feet ; and 5120 -=- 720 = 7.1 miles nearly, still leaving a reserve of one-third. But it has been found that the actual performance exceeds this theoretical limit, and that starting with 350 pounds pressure, 9| miles have been run with a reserve of 85 pounds. How can this be accounted for ? Simply by the fact that the estimate of 7.1 miles was based on the supposition that a cylinder of mixed air and vapor at atmospheric tension was expended at each stroke. If nearly 50 per cent, more duty was actually secured, it proves that less than a cylinder of air and vapor did the work. But, it may be asked, How is this possible? How can expansion be carried beyond atmospheric tension without creating a vacuum, and losing power by working against back pressure ? This question was asked of Mr. Hardie, and the explanation brought to light another beautiful feature of this motor. There are valves called suction- valves in the exhaust passages, and whenever the tension of air in the cylinder falls below that of the atmosphere, these valves open and permit the stroke to be completed without back pressure, so that it is not necessary to use more air than will overcome the resist- ances, and this may vary from a full cylinder to a very small fraction, or between limits as extreme as one to thirty. INCREASED POWER FROM MOTOR CYLINDERS ACTING AS AIR PUMPS. The motor cylinders are so arranged that in descend- ing steep grades they act as air pumps, and at the same TESTS OF HARDIE COMPRESSED AIR MOTOR. 69 time as brakes, by which means it is found, as stated by the company's engineer, Mr. Hardie, that in running down grade on the Second Avenue Railroad, pumping back against a pressure of 200 pounds in the receiver, the pressure was increased 7 pounds in a distance of 0.4 mile. As it requires 360 cubic feet to- run one mile, 0.4 mile would require 144 cubic feet. If the pressure were increased 7 pounds in a receiver containing 160 cubic feet at 200 pounds, the air pumped back would have been 5.3 cubic feet at 200 pounds in 0.4 of a mile, equal to 69 cubic feet at atmospheric ten- sion, which is about half the amount of air that would have been expended in running an equal distance with the aid of the heat on a level, with a consumption of one cylinder of air at each stroke, but with actual results 50 per cent, greater. To appreciate the importance of this result, it must be observed that not only is all the air saved in running down hill and not a particle used, but half as much or more as would have been expended with the aid of heat and vapor upon a level is pumped back again, and at the same time the action of pumping back acts as a most efficient brake, the efficacy of which is spoken of by the intelligent mechanical engineer of the Delamater Works in terms of the highest commendation. This is certainly a most extraordinary result, and so large a percentage of gain is only possible in conse- quence of the great expansion in the motor cylinders. The air and vapor escape at the tension of the atmos- phere, without the noise which attends the escape of high- pressure steam. When the air at atmospheric tension is pumped back again, it can readily be perceived that a 70 STREET RAILWAY MOTORS. certain percentage of the power expended will be re- stored, since only half a cylinder of air or less is re- quired to do the work at each stroke. Such a contrivance can only be characterized as admir- able, and, it will be perceived, adds another considerable percentage to gain in coal as compared with steam motors. When a locomotive engine shall, while running, be able to manufacture coal and store it in the tender, it will then be able to rival this performance of the pneu- matic motor. It has been shown that at atmospheric tension the contents of the motor cylinder are just one cubic foot for each revolution of the car wheels and that there are 720 revolutions per mile. There should be pumped back therefore 720 cubic feet if the inclination were steep enough to employ full power, which is found by computation to be 198 feet per mile, and when heated, saturated, and expanded, this air should run the car two miles or more, instead of one. In other words, while running down hill one mile, on a grade of 198 feet, the motor theoretically might store up enough to run it two miles on a level ; and recent experiments have shown that 50 per cent, may be added to this estimate. HEAT AND COLD BY COMPRESSION AND EXPANSION. In some forms of pneumatic apparatus much incon- venience has been experienced from the heat liberated in compression, and again from the intense cold resulting from expansion, which deposited ice in the cylinders and ports when moisture was present, as it always is in air TESTS OF HARDIE COMPRESSED AIR MOTOR. 71 in its ordinary condition. It has been stated by writers on pneumatics that one pound of air at one atmosphere and at 60 compressed to two atmospheres is heated 116, and the units of heat liberated per pound are 0.238 x 116 = 27.6 units. Conversely the expansion of air causes an absorption of heat or production of cold to a corresponding extent. The compressors constructed at the Delarnater Works, in New York, secure comparative exemption from the inconvenience both of heat and cold. The apparatus now in actual use on the Second Avenue Railroad con- sists of an engine with two steam cylinders 12 inches diameter and 36 inches stroke, operating two double- acting compressors of same stroke, one of which has a diameter of 13 inches and the other a diameter of 6J inches. The number of strokes per minute in charging a car are 76 at the commencement, and 70 at the end ; the difference being caused by the difference in work to be performed. The fly-wheel weighs about 4 tons, with a diameter of about 10 feet. The air cylinders are jacketed, and a current of cold water circulates around them continually. The air compressed in the first compressor to about 5 atmospheres, passes into a tank of water in which the water is kept cool, and thence into the second compres- sor, where it is reduced in volume one-fifth a second time, making one-twenty-fifth of its original volume. The water-tanks perform a most important office, not only in cooling the air, but in drying it also. 72 STREET RAILWAY MOTORS. The explanation of this apparent inconsistency is simple. Ordinary atmospheric air contains more or less water, which on reduction of temperature below the dew-point is deposited to a certain extent on cold surfaces. In compressing 25 cubic feet of air into one, and cooling it with water, it is estimated that twenty-four parts out of twenty-five of the water will be absorbed and removed. When this dry air is again expanded by being utilized in the motor, it cannot deposit ice, because there is so little contained water to form ice, and hence the fact, which it is said has excited great surprise amongst observers, that no frost whatever was formed except on the outside of the pipe from the condensation of outside moisture. Mr. Hardie stated that when the pressure ran low and the temperature of the tanks fell below 100 frost began to be formed. This is precisely as should be ex- pected. If air, in being compressed to one-half its volume, liberates 116 degrees of heat, it must absorb an equal amount in expanding, and if the water has cooled so low as not to furnish sufficient heat to compensate for it, the moisture taken from the water-tank must form frost to some extent. A suggestion may here be oifered in regard to the future possibilities of compressed air. Why can it not be compressed to high tensions by cheap power, trans- mitted for considerable distances through pipes, and used expansively in compound engines with heater, without the annoyance and risk of large boilers and coal consump- tion on the premises w^here the pow r er is utilized ? There TESTS OF HARDIE COMPKESSED AIR MOTOR. 73 is no reason to apprehend danger from this increase of pressure. The air receivers, unlike steam boilers, never deteriorate ; the air being perfectly dry, and the receivers coated internally, there can be no rust : and if pressure is increased, the thickness of material can be increased also, and the factor of safety remain the same. Any defect of material or workmanship would be revealed by proper tests; and if a rupture should occur, there would be only an escape of cold air no steam and no fragments of iron. A cylinder, fully charged, was ruptured in France purposely by the fall of a heavy weight. The air escaped simply with a hissing sound ; no fragments were projected as in explosions of steam boilers, and cold, not heat, resulted from the expansion.* WHAT GRADES CAN THE PNEUMATIC MOTOR OVER- COME, AND WHAT LOADS CAN IT CARRY ? These are pertinent questions, and can be readily answered. Ordinary locomotives are so proportioned in their boiler and cylinder capacity as to be able to slip their wheels on a dry rail if the engine should be chained fast, so that it could not advance upon the track. In that case the adhesion, which is, at a maximum, about one-fifth of the weight upon the drivers, measures the power of the engine, and not the pressure in the cylinders. The power varies, and is greatly reduced in bad conditions of the track. Power of Motor Cylinders. Assume that the air is used under 16 atmospheres, cut off at one-sixteenth, and * This was written in 1879. At the present time, 1893, more than 25,000 horse-power are employed in this way in Paris alone. 74 STREET RAILWAY MOTORS. expanded to fill a cylinder at atmospheric tension, giving mean pressure at 0.236. The initial pressure being 16 atmospheres, the mean pressure is 16 x 0.236 = 3.776 atmospheres, and 3.776 x 1 5 = 56.64 pounds per square inch. The diameter being 6J inches, the area is 33.18, and the piston pressure 33.18 X 56.64 = 1879 pounds. If the air should be cut off at -J, instead of y 1 ^-, the mean pressure would be 6.158, and the crank pressure 3064. There are 2 cylinders, cranks at right angles, one at full stroke when the other is on its centre. The weight of the car loaded is 8 tons. There are four wheels con- nected. Weight on drivers 16,000, adhesion one-fifth a 3200 pounds. The radius of the wheel is 14 inches, and of the crank 6 J inches, then 3200 X . = 6880 pounds to be exerted on the crank, not allowing for fric- tion of machinery, if it be required to slip the wheels on a dry rail. Or, stated in other terms, the power of 1879 pounds at the crank is quivalent to 871 at the rail, and 3064 at crank to 1422 at rail. The power of the motor cylinders with ordinary consumption of air is therefore insufficient to slip the wheels on a dry rail, but with street motors so large an amount of cylinder power as would be required for that purpose is unnecessary ; owing to the frequent bad con- dition of the track, a large surplus of adhesion is re- quired. The cylinder power can be increased four-fold by admitting a full cylinder of air ; but this would be objectionable, as causing waste of air and noise from exhaust, except in overcoming great resistances of short duration, as in pulling the motor over cobble-stones when derailed. With a small motor of 6 tons the adhesion would be TESTS OF HARDIE COMPRESSED AIR MOTOR. 75 reduced to 2400 Ibs., and the crank pressure required to slip the wheels to 5160 Ibs. The adhesion in ordinary conditions of the rail is therefore, as it should be, in excess of the cylinder power, and the wheels can slip only in consequence of ice and snow. It remains to de- termine the power for propulsion on a straight and level track and the power required on grades. The traction of ordinary railroad trains is 9.2 pounds per ton on a straight and level road, based on the regu- lar business of the Pennsylvania Railroad ; but with a street motor it is said to require about 25 pounds per ton, eight tons require 200 pounds, and this resistance acting on a lever of 14 inches from the axle, while the propel- ling power acts with 6J inches, will increase the power on the crank to 200 X if =430 pounds. As the power on the crank with the 8 ton motor is 1879 Ibs., it would be sufficient to move 4 such cars, or 32 tons, on a straight and level road, not allowing for friction of machinery and losses in transmission of power from the crank, if, as has been stated, the traction does not exceed 25 pounds per .ton, upon which this estimate is based. It was found that when dry air was used and the machinery was cold, the pressure of the air by gauge indications being 20 Ibs., it required the full head to propel the car, while, where warm air was used, the car moved when the gauge indicated considerably less pressure. Twenty pounds pressure is 1J atmospheres. The average mean working pressure is 3.776 atmospheres. Twenty pounds produces 625 Ibs. crank pressure, or 300 at rail, and if this amount was required to overcome friction and move the motor, it would be equivalent to 76 STKEET RAILWAY MOTORS. 37J pounds per ton, instead of 25 pounds, and absorb 50 per cent, more power than has been allowed ; but it is stated that there was a back pressure at the time of several pounds per square inch, in consequence of the small size of the exhaust ports, which would cover a considerable part of this difference. It is possible, therefore, that, with the air heated, the traction may not exceed 25 pounds per ton ; but it would be well to test both the traction of the motors and of ordinary cars by a dynamometer. GRADES. It has been shown that if air is admitted into the working cylinder at a pressure of 16 atmospheres, cut off at one-sixteenth of the stroke and expanded to atmospheric tension, the mean pressure on the crank would be 1879 pounds and the equivalent to overcome resistance at the rail 871 pounds, capable of moving on a straight and level road, if all could be utilized, 4 cars of 8 tons with traction of 25 pounds per ton, and certainly 2 cars. Also if the air should be cut off at ^, the mean crank pressure would be 3064 pounds and the equivalent at the rail 1422 pounds, capable of moving 4 such cars upon a level. As the angle of friction with traction of 25 Ibs. per ton is 66 feet to the mile, the eight ton motor should be able to haul twice its own weight on a . grade of 66 feet or 2 cars, on a grade of 132 feet 1 car ; but 2 cars could be hauled by increasing the amount of air and cutting off say one-sixth, instead of one-eighth. The eight ton motor without extra cars attached TESTS OF HARD IE COMPRESSED AIR MOTOR. 77 should be able to overcome the steepest grades usually found on horse railroads. The steepest grade on the Second Avenue Kailroad is said to be 230 feet to the mile, or one in twenty-three. The power with a full cylinder of air would be about 8 times the average power expended in working, and consequently the reserve is large enough to overcome great resistances of limited duration. SMALL MOTORS or 5 TONS WITH CARS ATTACHED. It would be a most serious disadvantage if the gen- eral introduction of pneumatic motors should require the abandonment of the old plant. Fortunately such abandonment is not only unnecessary, but the best possible system for the economical operation of a line and for the accommodation of the public consists in the use of small motors, or of combination car and motor capable of carrying from one to three additional cars in a train under one conductor, at hours when the travel requires it. Suburban residents desire frequently k) make social visits or to attend lectures or places of amusement in the neighboring cities, and can testify to the discomfort, not to say danger, of riding home late at night with one foot on the platform and the other in space. The ordinary horse car, loaded, weighs about five tons, the motor would weigh about the same, or with six tons would admit a large increase of reservoir capacity ; there would then be no pretext for objection on the ground of injury to track. It could run with 78 STREET RAILWAY MOTORS. one car in the middle of the day, and morning and evening with 2 or 3 under one conductor. It could make the trip in half the time, certainly in two-thirds, of the horse-car and take the place of horses, the sale of which would nearly or quite pay for the motor, so that there would be but little, if any, increase of capital for street motors, and nothing except for engines and com- pressors at the station. The small motors, weighing 6 tons, would have the same cylinder power as the 8-ton motors previously de- scribed, which gives 871 or 1422 pounds at the rail, as the air is cut off at ^g- or J of the stroke. The adhesion with dry rail is 2500 Ibs., and the traction of the motor at 25 Ibs. per ton (3 x 25 = 150 Ibs. If these small motors should be used to haul ordinary horse-cars, it becomes necessary, in estimating the per- formance of the motor, to know the traction of such cars. For obvious reasons this traction must be less per ton than that of the motor, and yet more than that of ordinary railroad cars, which is 9 pounds per ton. Probably 15 pounds per ton would be a full allowance for the traction of ordinary horse railroad cars, and a train of one 6- ton motor and two ordinary cars of 5 tons each, loaded, would make the weight of the train 16 tons, and the traction 300 pounds an average for the train of 18.8 pounds per ton. And 18.8 pounds per ton traction would give the angle of friction at which the train would descend by gravity = 44J feet to the mile. The train of one small motor and two cars could ascend grades of 178 feet to the mile, and with one car TESTS OF HARDIE COMPRESSED AIR MOTOR. 79 grades of 240 feet to the mile, and steeper grades could be overcome by using more air,* The separate motor, not intended to carry passengers, except, perhaps, on top, would permit an increase of reservoir capacity from 160 to 225 cubic feet; and if reservoirs be placed also under the seats of each car, the^_ capacity of a two-car train with motor would be ex-, ' tended to 325 cubic feet, or doubled, and the run to ^.2 ; miles. If, in addition, in speculating upon the possi^ bilities of the future, the reservoir pressure should bcN increased to 500 pounds, instead of 350, the run would be extended 43 per cent., or to 17 miles, and with one car attached to motor instead of two, still further. For working elevated railroads, as a substitute for steam, the pneumatic motor is the perfection of a propelling power. The motor itself could be filled with air reser- voirs, giving, with the addition of reservoirs under the seats of the cars, almost unlimited capacity, and there is no run within suburban limits that would be beyond the power of the motor, with a single station in the middle of the road to reinforce the pressure. The cost of fuel would be reduced fully 66 per cent., and noise, dust, steam, and sparks from motor avoided. If a motor should run off the track, it has power to run itself on the street pavements, and can be readily replaced by the aid of crowbars. If the machinery should become deranged, another motor could push it, * Since the above was written further experiments have shown that the increased consumption of air by attaching horse-cars to the motor is about the amount that could be supplied by reser- voirs under the seats, and, consequently, that the distance run need not be diminished by attaching additional cars if so provided. 80 STREET RAILWAY MOTORS. and by a simple hose attachment the air in the disabled engine could work the machinery of the helper. HORSE-POWER OF THE HARDIE MOTOR. With cylinders on motor 6J inches diameter and 13 inches stroke, pressure of air 16 atmospheres, cut off at one sixteenth of stroke, giving average pressure 56.64 Ibs. per square inch, and speed of motor six miles per hour, the horse-power applied to pistons will be found to be 17.7, or, if the speed is four miles per hour, 11.8 horse- power. Area of piston 33.18 square inches. Travel of each piston 22 inches to each revolution. 720 revolutions per mile =3120 feet for both pistons per mile. * 3120 x 33.18 x 56.64= 5,862,480 foot-pounds per mile = 586,248 foot-pounds per minute, and 586,248 -*- 33,000 = 17.7 horse-power. This assumes that the air operates upon the piston to the full limit of the stroke, but with less resistance much less air is used, and the horse-power will be reduced ; on the other hand, there may be occasions when a temporary increase becomes necessary. By letting in a full pres- sure of air more than three times the normal pressure can be applied immediately. A few minor points in favor of the motor will be stated. Skilled engineers are not required to run them ; a man of ordinary intelligence can learn to run these motors in a single trip. What is a most remarkable and beautiful feature of the contrivance is that a driver, however ignorant or careless he may be, cannot fail to use exactly the proper amount of air for the resistance TESTS OF HARDTE COMPRESSED AIR MOTOR. 81 to be overcome, and cannot waste it. If he admits too little, the car slackens speed or stops ; if too much, he must apply the brake. All is done by the movement of a lever, back or forward ; no other brake is needed, and the motion of the car is a perfect governor. Another advantage of the motors is that the view of the track is unobstructed and can be seen from the plat- form on which the driver sits, while horses obstruct the view of the track for 30 feet. On a level track the car can be stopped within its length when running at a speed of 12 miles per hour, and on grades in a time longer or shorter in proportion. The brake can never be out of order so long as the car has the ability to move at all. The brake consists in a full or partial reversion by moving a lever. If the lever should get out of order, which is scarcely within the bounds of possibility, the car could not move at all, therefore the brake cannot fail. It was noticed also in running along the Second Avenue Railroad on the motor that horses on the opposite track meeting the motor would sometimes shy, but other horses not on the track did not notice it. The car horses would, no doubt, soon become accustomed to the motor, but as its general use would supersede horses altogether, this fact is of little consequence. OBJECTIONS. A criticism of the motor has been made by a mechan- ical engineer of some prominence, which can only be accounted for on the supposition that the letter which recites the objections was written without consideration. 6 82 STREET RAILWAY MOTORS. It is desirable, however, to have objections stated ; when they can be shown to be groundless they serve to inspire and increase confidence. The objections were : 1. The air car requires 50 horse-power in compressors to keep it in operation. True ! But if dry air be used the same engine will charge 7 cars per hour, and if moist and heated air be used 14 cars, if the run should not be increased and only half the air should be required, which is only 4 horse- power to a car, and each horse-power costs in coal con- sumed one-fourth to one-third as much as in a street motor. Second objection. The cost of repairs for the steam cars would be less than for the air car. Arts. No reasons are given, and the fallacy of the assertion is self-evident. There is no fire-box to burn out, and no boiler to rust, burn out, or explode. The reservoirs, filled with air absolutely dry, are as nearly im- perishable as anything on this mundane sphere can be. The parts liable to wear by friction are the same as on other engines, neither more nor less expensive to repair, but the heaviest expenses of fire-box, boilers, and flues are all saved. Third objection. The air car is not so reliable as a steam car, as it has not the same surplus for emergencies. Ans. Why not ? A surplus is provided of 33 per cent. Does a locomotive finish its trip with as much reserve power in coal and water in its tender ? Besides, all the cars of a train can have air cylinders under the seats, the whole of which can be held in reserve. The above are the only objections advanced. TESTS OF HARDIE COMPRESSED AIR MOTOR. 83 LOCATION OF POWER PLANT. . Considerations of economy would lead to the location of the power plant at or near the middle of the section of the road to be operated, for the reason that the power could be readily renewed by a simple hose attachment while passing the central station, whereas if located at one end a supply for a run of double the length would be required ; but it may be, and in a majority of cases probably will be, found most economical to locate the compressed plant back of the main thoroughfare, where land is of comparatively little value, and trans- mit the compressed air through pipes to any number of reservoirs conveniently located along the route. These reservoirs would occupy but little space, and would not require a front location upon the thorough- fare traversed by the cars. They could be placed one hundred feet or more in the rear, or even under ground, and from them strong wrought-iron pipes could lead to the track, where an air plug with hose attachments covered by a manhole plate would afford facilities for replenishing the air charge of the motors at any intervals however short that might be considered desirable. Underground pipes could be carried to the car sheds to supply motors with full charges while standing on the tracks. As all the reservoirs upon the line would be connected with each other, and with the central plant the pressure would have a constant tendency to equalize itself throughout the whole system, and a large reservoir ca- pacity thus created would be of great advantage in insur- ing an ample supply of air under nearly uniform pressure. Oil is frequently transmitted in pipe lines under a 84 STREET RAILWAY MOTORS. pressure of 1500 pounds per square inch, so that a pres- sure of even 600 pounds would not require pipes of ex- traordinary thickness. In the transmission of elastic fluids through pipes for long distances there is a loss of power due to friction dependent upon the length and diameter of the pipe, but more upon the velocity of transmission. This subject was very fully investigated by the writer in 1879 in connection with the Holly system for the transmission of steam for heat and power. If, for the present, it be assumed that air is compressed to 40 atmospheres at a central point, and transmitted by pipes of six inches diameter for utilization in distant reservoirs and in quantity sufficient to charge one car cylinder of 160 cubic feet capacity per minute, the initial velocity of the air in the pipe would be twelve feet per second as a maximum, and the loss of head by friction, based on the tables deduced from experiments at the Mt. Cenis Tunnel, would be but 1.83 pounds in a distance of one mile, assuming that the car cylinders should be returned entirely empty and require 160 cubic feet as the initial pressure. But in the trips on the Second Avenue Railroad the cars returned to the station with one-third of their charge remaining, or with 8 atmospheres, after expending 16 atmospheres in the run ; consequently a charge of 40 atmospheres would have permitted just double the dis- tance to have been operated with a single charge, which would be 18 miles. One car per minute could be required on any city line only at the hours of maximum business, and even at such hours, if the cars returned with partial charges, the TESTS OF HARDIE COMPRESSED AIR MOTOR. 85 quantity of air required for re-charging would be less than the maximum, the velocity of transmission would be re- duced, and the loss by friction, which is as the square of the velocity, would be reduced also. Instead of dis- patching one car per minute, the same capacity can be more economically aiforded by one motor car in 2 min- utes with one trailer, and still more with 2 or 3. It would seem to be practicable, therefore, on extended lines to locate compressor plants at intervals of 20 or 25 miles, and transmit power in pipes to intermediate stations 10 or 12 miles distant, with additional interme- diate reservoirs at stated intervals to be used in case of accident, such reservoirs consisting simply of a number of small cylinders of steel two feet, more or less, in diame- ter, connected with each other by pipes. The cylinders of small diameter would be necessary to secure strength. Whether the pneumatic system could be extended to supersede steam motors on ordinary railroads is a ques- tion that can be reserved for future consideration. It may be observed, however, that the traction on straight and level steam railroads is only 9 pounds per ton for the train, while on ordinary street railroads it has been estimated for the motor at 25 pounds. Also, that in passenger cars reservoirs of air cylinders can be placed below the seats, and the floor of the car may rest upon two longitudinal cylinders supporting in the middle of the car a number of transverse cylinders. The frame could be of hollow pipes, and thus a very considerable reservoir capacity could be provided in each car. A tender filled with air reservoirs could take the place of the ordinary tender with coal and water. How far such a train could be made to run with ordinary cars without 86 STREET RAILWAY MOTORS. reinforcement of power, and what the cost of power as compared with steam, would be interesting inquiries, for the determination of which all the necessary data have not yet been fully presented, and it is moreover foreign to the present inquiry. There can be no doubt, how- ever, and conclusive evidence can be and has been pre- sented, that for street, elevated, and underground rail- roads steam cannot favorably compare with air, either in economy, convenience, or freedom from dirt, smoke, noise, and other nuisances. In fact, it can justly be claimed that it fulfils every condition that could possibly be desired, and is free from any objection that can be urged. RECORD OF DIRECT EXPERIMENTS WITH THE HARDIE MOTOR. For several days previous to March 12, 1879,' experi- ments were made with the motor on the Second Avenue Eailroad, the results of which it is proper to note. March 9th, started from depot at 127th Street, and made three round trips, with the following record : 1st trip started with pressure . . . 360 pounds. Consumed 95 " Returned with 265 " 2d trip started with 265 " Consumed . . . . . 95 " Returned with . . . . 170 " 3d trip started with 170 " Consumed . . . . . 75 " Returned with 95 " This result was so remarkable, that the President of the Company, Mr. F. Henriques, requested the writer to superintend some further experiments, to ascertain if TESTS OF HARDIE COMPRESSED AIR MOTOR. 87 increased duty would be secured by running at reduced pressures. Accordingly, on March 10th, three more trips were made, with the following record : 1st trip started with 360 pounds. Temperature of water .... 324 Mean working pressure while running . 120 pounds. Water absorbed . . . . 31 " Pressure on return .... 290 " Consumed 70 " 2d trip started with 286 pounds. Mean working pressure . . . 120 " Consumed water . . . . 11.3 u Temperature of water on return . . 198 Pressure at end of trip . . . 195 pounds. Consumed 91 " 3d trip started with 195 pounds. Mean working pressure until pressure fell below . . . . . 120 " Water absorbed 19.8 " Temperature on return . . . 180 Pressure at end of trip ... 95 pounds. Consumed 100 " The comparison of these two tests exhibits very remark- able results. The total consumption of air in the three round trips, starting with 360 pounds and finishing with 95, was 265 pounds, or an average of 88.33 each trip. The last trip of the first series was run with 75 pounds. This fact it is difficult to explain, as the water was cer- tainly much cooler than at the start, and it could not have contributed so large a proportion of vapor. In the first run of the second series the air consumed was 70 pounds pressure, equivalent to 747 cubic feet, or 57J pounds at atmospheric tension, and this air ab- sorbed the very extraordinary amount of 31 pounds of 88 STREET RAILWAY MOTORS. water, or more than half a pound of water for each pound of air, which is double the average consumption and four times the capacity of ordinary air for moisture. It will be observed, also, that a great reduction of temperature from 324 to 190 or 126 was found in the two runs. The large quantity of vapor and heat abstracted from the water in the first run will fully and satisfactorily ac- count for the small quantity of air consumed, and would serve to indicate the possibility of increasing the distance run by burning gas or petroleum to replace the heat which the air absorbs. In the last run of the second series 100 pounds were con- sumed. This was to have been expected, as the water at the end of the run was 32 below the boiling-point, and water instead of steam was probably carried out. On Tuesday, March llth, further experiments were made to determine the effect of attaching additional cars to the motor. The following is the record taken by Mr. Harley : 1st trip started from 127th street, with . 300 pounds. At depot, 97th Street, air pressure . 250 " Consumed in half trip . . 50 " Coupled on 2 ordinary street cars, pres- sure at end of trip, 127th Street . 170 " Consumed with the 2 cars and motor . 80 " Temperature of water .... 205 2d trip, started with ..... 335 pounds. Run at mean pressure .... 150 " Cars in tow ...... 2 Pressure at 97th Street . . . 275 pounds. Consumed 60 " Water used 14.2 " Reduced pressure in heater to . . 130 " TESTS OF HARDIE COMPRESSED AIR MOTOR. 89 2d trip return, 2 cars in tow, started from 97th Street, pressure . . . 275 pounds. Pressure at 127th Street . . . 190 " Consumed pressure . . . . 85 " Water used 14.2 " 3d trip, heated water again, 2 cars, started from 127th Street with a pressure of 330 pounds. At 97th Street, pressure . . . 265 " Consumed 65 " Water used 16 " Return, no cars in tow, started from 97th Street 250 " At 127th Street 200 " Consumed 50 " Water used 11 " OBSERVATIONS. It appears that the two up trips consumed 80 and 85 pounds of pressure, and the two down trips 60 and 65 pounds, and the up trips required 33 per cent, more than the down trips. This may be due to the very bad condi- tion of the up track. The average round trip required 145 pounds with two cars attached to motor, as against 90 pounds with motor alone, an increase of 60 per cent., or 30 per cent, for each car hauled. The two cars probably weighed as much as the motor, and, if so, the traction of the cars would be 15 pounds per ton, assuming the motor at 25. The data furnished by observations on the motor will serve to indicate the loss of power and of work in trans- mission from the piston to the rail. Starting at 350 pounds pressure, the run of 9f miles was made with 270 pounds pressure, or 90 pounds per average run, or 298 cubic feet of air, at atmospheric density, per mile. As- 90 STREET RAILWAY MOTORS. suming for the present that the effect of heating and moistening the air is chiefly to compensate for the reduced temperature in expanding, and to secure the full benefit of isothermal expansion, the foot-pounds of work per mile will be computed on this basis. The volume required per mile to fill the capacity of the working cylinders is 720 cubic feet ; the 298 cubic feet therefore filling 40 per cent, of the cylinder capacity, leaving 60 per cent, to be replaced by air from the ex- haust passages, by the opening of the suction valves. If used under an average pressure of 170 pounds = 11.33 atmospheres indicated, or 12.33 atmospheres actual, the atmospheric pressure would be reached in 13 x 0.4 = 5.2 inches of stroke in cylinders, and the mean piston pressure during the 5.2-inch stroke would be 1732 pounds. As there are 4 cylinder discharges to each revolution, and 720 revolutions to a mile, the travel of piston per mile run under pressure will be 720 x 4 X 5.2 =14,976 inches = 1250 feet, and 1250 x 1732 2,165,000 foot- pounds of work done at piston per mile of actual run. If now it requires a tractive force of 25 pounds per ton on a level road to move the motor, and the weight be 8 tons, then 8 X 25 X 5280 = 1,056,000 foot-pounds per mile, which, if the road was level, would represent the actual work utilized from an expenditure of 2,165,000 foot-pounds upon the piston, which is 50 per cent, nearly. It would appear, therefore, that only half the power applied to the piston is actually utilized in propulsion on the track, and the balance must be expended in overcoming friction of motor and other resistances and TESTS OF HARDIE COMPRESSED AIR MOTOR. 91 losses. The power required to move the motor, if ap- plied externally, and also the traction of the ordinary horse-cars, is not known, and should be determined. The computation of average run has been based on an expansion of 12, and reaching atmospheric tension at 0.4 of the length of the cylinder, using only one-thirtieth part of a cylinder of air at each stroke. If a full cylinder of air should be used, the power on the piston would be increased nearly nine times, but the consump- tion of air thirty times. This great reserve of power over the average for ordinary work is an advantage of no small importance. The reserve of power can be drawn upon to overcome great resistances, if of short duration. As an illustration of this fact, and since the above para- graph was written, Mr. James, who was associate engineer with Mr. Hardie, states that on one occasion the motor got off the track at a sharp curve and switch at the 127th Street depot ; a ditch had been dug for gas pipes and filled in, but not paved. The hind wheels sunk in the ditch until the frame of the motor rested on the pave- ment. A high pressure was let on and the machine pulled itself out without further assistance. This power of overcoming great resistances of short duration is of great value. In the consideration of the question of hot water motors, the position was taken that in the conversion of hot water into vapor or steam nearly a thousand degrees became latent, and this latent heat so rapidly cooled the remaining water from which it was abstracted that it was not possible, without the use of a fire, to restore the 92 STREET RAILWAY MOTORS. heat, and that the motor could not possibly run the dis- tance claimed for it. The observations just reported on the Hardie motor fully sustain these conclusions. The first trip in the second series started with full tank, 5 cubic feet or 310 pounds of water, at a tempera- ture of 324, and used 31 Ibs. water. The second run used 11.3 Ibs., and the third 19.8 Ibs., in all 62.1 Ibs., and the temperature in return was 180 with 248 pounds of water. The differences there were : 310 pounds water at 324 = 100,440 units. 248 " " 180 = 44,640 " Units lost with 62 Ibs. 5.5,800 But 62 Ibs. water with a difference of temperature of 144 would remove only 8928 units, leaving 46,972 units to be accounted for as latent heat. This is equiva- lent to 758 units per pound of water evaporated. As this is less than the amount of latent heat required for the conversion of water into steam, it follows that after the temperature of the water fell below 212, water and not steam must have been carried over with the air. If figures are made upon the first two runs where the temperature was maintained above or near the boiling- point, the data are : Temperature at starting, 324 ; on return, 198 ; loss, 126. Water evaporated, 42.3 Ibs. Units at 126 = 5330. Weight of water at starting, 310 pounds ; on return, 267.7 pounds. TESTS OF HARDIE COMPRESSED AIR MOTOR. 93 Thermal units at start, 310 x 324=100,440 Thermal units on return, 267.7 X 198= 53,004 Loss of thermal units . . 47,436 Accounted for by sensible heat-units as above 5,330 Leaves unaccounted for . . 42,106 If 1000 units per pound be allowed latent for water, 42,300, the difference is therefore fully accounted for, and proves that where air is passed through hot water the water removed carries off not only the units of sen- sible heat due to the difference in temperature, but also cools the remaining water to the extent of 1000 for every pound of water removed. Another important observation may here be made. In the 3 round trips of 9| miles the loss of heat-units in the tank was 55,800. If the heat had been maintained at 324 by means of a small naphtha or petroleum stove yielding more than 20,000 units in combustion, it is reasonable to assume that 15,000 units could be utilized, and consequently 4 pounds, costing not more than 3 cents, would supply the units for more efficient reheating at a cost of 3 mills per mile run of motor. This re- heating, it will be remembered, doubles the run with a given volume of air; in other words, 5 miles would be added to the run of the motor at a cost of 3 cents, which is a maximum cost. Small as this is, it is still higher than Mr. Hardie's estimate for hot water drawn from stationary tanks. He allows J of the coal used in compression. In this case 6 pounds of coal should furnish the 55,800 units, at a cost 94 STREET RAILWAY MOTORS. of one cent ; but by referring to the record, it appears that where the temperature of the water was 324 at the start, the run was made with 70 pounds pressure, and could probably have been made at 65 pounds if the tem- perature during the run had been maintained at 324. At this rate the air evaporated per mile would have been reduced from 300 cubic feet to 240. Another observation on this very important subject of reheating should be made. The air was not only expanded by the heat, so as to exert a higher pressure from that cause, but there were carried over 62.1 pounds of water in the form of steam, which would be equiva- lent to 1700 cubic feet of air at atmospheric tension, with the additional advantage of a warm exhaust and no possibility of frost. This accession of motive power in addition to the elevation of temperature will account for the fact that double runs were secured by the simple expedient of passing the dry air through a small tank containing only 5 cubic feet of hot water. VIII. ECONOMICAL MODES OF COMPKESSIOX. IN reference to the most economical method of furn- ishing supplies of air to the motor tanks, Mr. E. Hill, of the Norwalk Iron Co., who has had very extended experience, gives the following information : There are four methods in all of charging air tanks. First. A reservoir capacity two, three, or four times the size of the tanks and containing a pressure of air ECONOMICAL MODES OF COMPRESSION. 95 much greater than the pressure in the tank, so that when the valve between tank and stationary reservoir is opened and. the pressures equalized, the Resulting pressure in the tank will be the pressure desired. Next. Stationary reservoirs charged to a pressure somewhat higher than the pressure desired in the tank and said stationary reservoirs brought in connection successively with the tank to be charged. Third. A reservoir of very great size in comparison with the size of tank to be charged, so that for practical purposes the air can be considered as being drawn .from a reservoir of infinite size. Fourth. Direct pumping into the tank itself. Referring to plan No. 1, we have considered that a reservoir three times the capacity of the locomotive tank is employed. This reservoir must be charged to a pressure of 53.33 atmos. in order that the pressure in reservoir and tank shall be 42 atmos. after the reservoir and tank have equalized their pressures. The duty then for a compressor will be to pump up that tank from 42 atmos. to 53J atmos. at each charging of the locomotive. If this work is done in one minute, it will require 2380 H. P. Referring to plan No. 2, it will be assumed that three stationary reservoirs are used, and that each reservoir is of a size equal to the size of the tank on the locomotive. If these three reservoirs are charged to 47 atmos., and reservoir No. ] is brought into connection with the tank of the locomotive, the pressure will equalize between the two and become 27J atmos. If now No. 2 tank is brought in connection, the pressure will become 37.25. If the third reservoir is now connected, the pressure will 96 STREET RAILWAY MOTORS. become 42.12 atmos. Therefore, the duty required of the compressor is to pump up tank No. 1 from 27J atmos. to 47 atmos., tank No. 2 from 37.25 tq 47 atmos., and tank No. 3 from 42.12 to 47 atmos. This will require 2119 H. P. if done in one minute. Referring to the third plan, in which the reservoir is of very great size, so that practically when the locomo- tive is charged there is no fall of pressure, the duty then of the compressor is to compress all of its air to 42 atmos. To supply the locomotive under these circumstances, each minute will require 1828 H. P. The fourth plan, for direct pumping, presumes that absolutely no reservoir at all is used. Here the duty is simply to raise the pressure in the locomotive by direct pumping from eight atmos. to forty-two atmos- pheres. This will require 1706 H. P. if the work is done in one minute. It will, of course, be noticed from the above compari- sons that the fourth plan as regards power is by all means the one to be preferred ; but it is not presumed that such a large quantity of air can be compressed so quickly and cooled so rapidly in one minute. Therefore calculation should be made, if a locomotive is to be dispatched every minute, to have a number of locomo- tives at the charging station at the same time, so that each of those locomotives could be under treatment from ten to fifteen minutes, in order that the air may have time to cool during the process of compression, but the total power will be such as to dispatch one locomotive every minute. Answering other questions regarding the power to do the above work in 2J, 5, and 10 minutes, it may be said ECONOMICAL MODES OF COMPRESSION. 97 that follows in inverse proportion. The above calcu- lations are taken at a mean between isothermal and adia- batic compression, and are as near as possible what will be actually found to be the result in practice. As regards the expense of running compressors, it is proper to state that the above calculations give the power in H. P. The expense of a H. P. is a well-settled matter according to the style of engine which is employed to produce it. FROST FROM EXPANSION OF AIR. It is a common, but very erroneous, opinion that serious difficulty is experienced in compressed-air engines from the intense cold produced by expansion and the closing of the exhaust passages by frost. No difficulty of the kind has ever been experienced in the use of the Hardie motor, even with cold air; but the practice of reheating, which should never be omitted, since it doubles the power at nominal cost, raises the temperature of the exhaust air above the freezing-point. In the tests made on the Second Avenue Railroad in 1879, it was found that, although the air from the compressor was cooled by passing it through water, there was no deposit of frost. The writer explained the fact on the theory that the capacity of air for moisture was not increased by density, and that the escaping air was too dry to deposit moisture even at a very low temperature. Mr. Hill, of Norwalk, confirms this opinion, and has given the following very satisfactory explanation : " Your statement regarding the water left in compressed air agrees exactly with the authorities on this question 7 98 STREET RAILWAY MOTORS. as we understand them. The density of the air does not have an appreciable effect on the amount of moisture within a given space. The temperature, however, aifects it according to well-settled results. It has been observed that the higher that air pressures have been the less lia- bility there is to freezing at the exhaust. This result is in opposition to the preconceived opinions regarding the use of compressed air. Air of 15 to 30 Ibs. pressure when expanded in an engine almost uniformly gives trouble at the exhaust. Therefore it has been argued that air at very high pressure several hundred pounds would give a proportionate amount of trouble there, freezing because its exhaust could be expected to be so very much colder than the exhaust of air of lighter pressure ; but, as I have stated above, it has been found that the air at high pressure does not give this antici- pated trouble, and in fact does not give as much trouble as does air at lower pressure. The reason for this is readily explained. Air at the low pressure, when it is exhausted, will be cold enough to freeze whatever moisture there may be in it. Air at the high pressure will, of course, be cold enough on exhaust to freeze the moisture that may be in it. But to get the same power from low- pressure air as we can get from high-pressure air, we must use of the low-pressure air very many more cubic feet. As when temperatures are equal the moisture in the air depends upon the volume, it follows that for a given power when obtained from low-pressure air we have passed through our engine much more moisture, and, as it all freezes in any event, we run a greater risk of being stopped at the exhaust. Taking another case where air at 600 Ibs. pressure is stored in the reservoir ECONOMICAL MODES OF COMPRESSION. 99 of a pneumatic locomotive and is then, through a re- ducing valve, drawn down to 100 Ibs. pressure for use jn the cylinders, we would find that the air at 100 Ibs. pressure would be only J saturated with moisture. The air at 600 Ibs. pressure would be fully saturated. The moisture in one cub. ft. of 600 Ibs. air being by the process of reduction distributed through six cub. ft. of 100 Ibs. pressure, the result is that the air of 100 Ibs. pressure is, as stated above, only ^ saturated. Or, stating the case in another way, a cubic foot of air at 100 Ibs. pressure which has been obtained from a tank holding 600 Ibs. of air would contain only ^ the moisture which would be found in a cub. ft. of air at 100 Ibs. pressure, which had been obtained by compressing atmospheric air to 100 Ibs. pressure. " The above statements would all hold true without regard to the method of cooling. The question only would be, what is the temperature of the air, and has it been quiescent long enough to allow the moisture to be dropped ? The statement which I have heard made, that blowing air through water dried it by reason of the affinity of the water for the moisture in the air, is, in my opinion, a lame explanation. The process dries the air simply because it cools it, and any other method of cool- ing would accomplish exactly the same result." Considerable space has here been given to the subject of compressed air as a propelling power on street railroads, for the reason that writers who treat upon the subject of street motors almost invariably pass it over with a few disparaging remarks as something that has been tried and found wanting. It is really amazing to find so vast an amount of ignorance accumulated on this subject. The 100 STREET RAILWAY MOTORS. reasoning seems to be : "Well, this thing has been tried ; if it had any merit, why was it abandoned ? And no trouble is taken to inquire into the merits of the motor, or the causes which prevented its general use, causes having no connection whatever with the merit or the practicability of the invention. If the facts that have been stated will lead intelligent engineers and capitalists to investigate, there will soon be a change of public opin- ion upon this subject, and the best of all modes of pro- pulsion for street service will not be cast aside for other systems far more expensive in plant and operation, and far less satisfactory in results, both to the public and to capitalists. IX. COST OF OPERATION OF THE COMPRESSED AIR MOTOR FOR ONE DAY SIX MILES DOUBLE TRACK. FOR the determination of this question the data can be relied upon with more confidence than in any of the other cases under consideration. It has been demonstrated that the motor can be run with 300 cubic feet of free air per mile, and that the compressor plant to furnish this volume of air for each of 60 motors will require not more than 600 horse- power, or 10 horse-power at the central station for each motor. Each horse-power requires 2} Ibs. per hour of $3 coal, so that the coal per motor per hour will be 25 COST OF COMPRESSED AIE MOTOR. 101 pounds, to which the equivalent of 3 pounds must be added for reheating, making 28 Ibs. per hour for a run of 6 miles. The consumption per mile run will, there- fore, be 4f pounds, and the cost 7 mills per mile run. This is the whole cost of fuel, not including interest and repairs, which are less than in other systems. Cost of Plant and of Operation for the Pneumatic Motor. Land, 22,000 square feet of ground, at $1.50 . $33,000 Building 80,000 Engine, boiler, setting, etc., for 600 H. P. . 30,000 Reservoirs, pipes, etc. ..... 5,000 Cost for six miles double track . . . $148,000 Street Construction One Mile, Double Track. Track $20,000 Paving, 9282 square yards, at $3 . . . 27,846 Total street construction .... 47,846 Cost for six miles $287,076 Equipment. 75 combination cars and motors, at $3500 . $262,500 Summary. Power-house and plant $148,000 Street construction 287,076 Equipment . . . . . . . 262,500 Engineering, legal and miscellaneous expenses 20,000 $717,576 102 STREET RAILWAY MOTORS. Cost of Operation of Six Miles Double Track for One Day with the Pneumatic Motor. Coal, 5760 miles run at 4 pounds per mile 131 tons, at $3 per ton .... $40.50 Water, oil, and grease ..... 6.50 Depreciation of plant and rolling-stock . . 78.00 60 Conductors, at $2 120.00 60 Drivers, at $1.75 105.00 Engineers and firemen at station . . . 25.00 Car-house and other service .... 28.00 Repair of motors and cars ..... 200.00 Repair of engines and compressors . . . 15.00 Repair of track and buildings .... 50.00 Track cleaning, train, and shop expenses . . 25.00 Accidents . 20.00 Legal and other expenses ..... 10.00 General and miscellaneous expenses . . . 50.00 $773.00 Cost per mile . . . 13.42 cents. Of this amount the fuel alone costs 7 mills. COMPRESSED AIR FOR ELEVATED RAILROADS. The practicability of using compressed air instead of steam on elevated railroads and its superior economy were fully demonstrated, in 1880, on the Second Avenue Railroad, in New York. A motor was constructed at the Baldwin Locomotive Works, upon the plans and under the immediate super- vision of Robert Hard ie, and was tested upon the Second Avenue Railroad ; certificates of these tests by prominent officers and machinists of the road are in possession of the writer. The section of the road upon which the experiments COST OF COMPRESSED AIR MOTOR. 103 were conducted is-8J miles long, and there are 22 stations in this distance. The road is undulating and circuitous ; an elevation of 80 feet has to be overcome in a part of the distance, and 6 quarter- circle curves of 90 feet radius. Intervals between trains, 3 minutes. A report by Charles W. Potter, in 1883, gives a very full account of the test of the Hardie motor on the ele- vated road and its economic results. An extract is here given : "The Hardie engine, weighing 18f tons, was found capable, with a single charge of air, of hauling the regu- lation five car trains, full of passengers (weighing approximately 60 tons, or about 78 -tons including the engine), the entire distance of the road, making all regulation stops to deliver and receive passengers, ac- complishing the trips in the schedule time, and with sufficient surplus of air remaining to enable it to return light to the engine depot, a distance of 5J miles, the greater part up hill. The quantity of air expended in making these trips with trains was equal to 12,600 cubic feet at atmospheric pressure, and in returning light, 4600 cubic feet ; making a total expenditure of 17,200 cubic feet. It may be mentioned that this dis- tance is the utmost which the present steam locomotives travel without a fresh supply of water. " The efficiency, and still more the economy, of an air locomotive increases with the magnitude of the scale on which it is constructed : and therefore, as the engine whose performances are given was built for experiments on the elevated railroad, and was necessarily limited in weight, it is clear that were it possible to increase the weight to 30 or 35 tons, as would probably be the case 104 STREET RAILWAY MOTORS. in an underground railway, the storage capacity for air would be increased and a proportionately longer distance would be possible with a single change. " Moreover, the weight of the London underground trains, in proportion to the weight of the engines that draw them, is less than in the case of the elevated trains in New York, and, as the stations are farther apart, still better results may be expected. In fact, it is urged that in point of efficiency air engines of the Hardie type can be constructed to meet all the requirements of every portion of an underground as well as of an elevated rail- way even better than steam, for the pure air discharged at each revolution will also aid in ventilation. "The next and most important consideration is the cost, first of equipping the road, and secondly of operat- ing it, and as in this particular it would be well to have all estimates on actual experiment, it is desirable to again revert to the results attained upon the elevated railroads in order to make a comparison with the steam engines there in use. "As the storage reservoirs used in air locomotives are cheaper to construct than the boilers of steam locomo- tives, and as the machinery in the one case entails prac- tically no more complication than in the other, it is clear that in point of first cost the balance is in favor of the compressed air locomotive ; but the margin of saving is rather more than counterbalanced by the compressing plant necessary for furnishing the air. The builders of compressing machinery in the United States estimate that to furnish 12,600 cubic feet of free air (the quantity expended by the Hardie engine in a single trip) com- pressed to 600 pounds per square inch, which was the COST OF COMPRESSED AIR MOTOE. 105 storage pressure adopted in the engine now under con- sideration, and to furnish this supply every three minutes, the amount of horse-power required is 1285, and they are willing to guarantee the correctness of this estimate, and contract for the supply of the necessary plant. "As the locomotives used have to be supplied with air at each end of the road, this amount of power must be duplicated ; hence a total is necessary of 2570 horse- power, or say roundly 2600, to operate the particular section of the road referred to. On the whole, therefore, the first cost of equipping the road might be somewhat greater for air than for steam locomotives ; but this, as will be shown later, would be more than counterbalanced by the reduced cost of operating. As it requires at least 36 locomotives to carry on this traffic, at three minute intervals, including switching and relays, each locomo- tive would be represented by about 72 horse-power of stationary plant, and this is the maximum that would be needed, as it is only during a few hours morning and evening that the interval between trains is so short as three minutes, and as it is obviously expedient to divide up the power into, say, four complete sets at each terminus, it would only be necessary to operate the whole of it during those few hours, and thus ample opportunity would be afforded for inspection and repairs. " Strange as it may seem at first sight, considering that the power is used second-hand, so to speak, yet a very large saving is effected in point of fuel, and it is this saving, with that of the fireman on the locomotive, that turns the balance of economy greatly in favor of com- pressed air. The cost of operating is computable as follows : 106 STREET RAILWAY MOTORS. " The average rate of consumption in these steam loco- motives is one ton per 60 train-miles, or about 45 pounds per mile. This is necessarily high, owing to the frequent stoppages. As previously stated, 2600 horse-power will charge a locomotive with compressed air every 1J minutes, or 40 locomotives per hour, and each locomo- tive will haul a train 8J miles, being 340 train-miles per hour. The stationary compressing engines need not consume more than 2 Ibs. of coal per horse-power per hour, or say 2 J Ibs. to make allowances and be on the safe side. Hence the consumption of fuel for 2600 H. P. will be 6500 Ibs. per hour, and 6500 Ibs. over 340 miles equals less than 20 Ibs. per train-mile, not half the con- sumption of the steam locomotives, and only one-fourth the cost, as cheaper fuel may be used. Again, as the air locomotives require only one man to drive them, a considerable saving in the cost of labor is effected, even allowing for the comparatively small attendance neces- sary to work the stationary plant." In the figures given by Mr. Potter, he estimated a saving of 17 pounds of coal per train-mile and 340 train- miles per hour. If this average should be maintained for only 12 hours, allowing for longer intervals at mid- night and in the middle of the day, the saving of fuel would be 5780 Ibs., or 2.89 tons per hour, 34J tons per day, and 22,592 tons per annum, costing in the tender of engine probably $5 per ton, or $112,960 per year, the interest at 5 per cent, on $2,259,200. But this is not all. The 36 engines require firemen, and deducting 11 to offset labor at the compressor plant, there will remain 25 men at $1.75 per day. This small COST OF COMPRESSED AIR MOTOR. 107 item amounts to $16,000 a year, the interest on $320,000 at 5 per cent. What would be the cost of the compressor plant to furnish 1 2,600 cubic feet of free air in 1 J minutes = 8400 cubic feet per minute? The compressors, boilers, and engines can all be covered by $115,000, so that the saving in firemen alone would represent nearly three times the cost of the compressor plant. How can there be any question, therefore, as to the great superiority of compressed air over steam for the operation of city railroads, whether surface, elevated, or underground ? WHY COMPRESSED AIR is NOT IN GENERAL USE. If, as stated, it has been demonstrated by actual results, both on surface and elevated railroads, that com- pressed air furnishes a mode of propulsion far superior to steam or horse- power and at the same time far more economical, affording superior public accommodation and larger dividends to the companies, requiring no trolley wires overhead, or cables beneath the surface, with not a single objectionable feature of any description, but many in its favor, why is not the system universally used ? The question is pertinent, and the answer can be briefly given. In 1879 public opinion was not sufficiently educated to regard this improvement with favor. Absurd as the objection then made may now appear, presidents of horse railroad companies declared that any car moving along a street without horses in front would frighten other horses even if there was no noise, and that many acci- 108 STREET RAILWAY MOTORS. dents would occur and suits for damages be instituted ; that the system could not be used without stuffing the skins of dead horses and running them on a low truck in front. This was the reason given to the writer by the president of a city railroad in Philadelphia, who declined to consider the question of the advantages of a change of system, and attempts to induce others to examine into the merits of compressed air proved equally unsuccessful, so that efforts were discontinued. When it is considered that both cable and electric roads run without horses and cause far more noise than the pneumatic engine, the objections made in 1879 ap- pear very absurd. But this was not the only cause of failure to secure the adoption of the improvement. Mr. Hardie unfortu- nately fell into the hands of irresponsible parties and parted with the control of his patents to a straw com- pany, the collapse of which put an end to further efforts. Mr. Hardie afterwards accepted a position as superin- tendent of a locomotive works, and has recently filled the position of mechanical engineer of the Columbian Exposition at Chicago. The following is his own story of the causes of failure in the introduction of the pneu- matic motors : " The proper way to have met all objections was not by discussion and argument, but by a practical demon- stration. Railroad men were not satisfied with a few exhibition trips of the motors, although, as a general rule, the performance was considered very satisfactory so far as it went ; but they all wanted to see a railroad operated exclusively and successfully; and until then no railroad would adopt the system. As it required COST OF COMPRESSED AIR MOTOR. 109 capital to do this, and as the motor company had prac- tically none, the enterprise was never carried beyond the experimental stage. It is true that this company was capitalized at $1,000,000, but that needs explana- tions. Those who organized the company were men of no financial standing, and the stock was all issued to them, without payment or consideration, except the ex- penses of organization and a few preliminary tests. In order to evade the law which required that the stock should be paid for at its full par value, a valuation of $1,000,000 was put upon some patents which one of their number held in trust; and the stock was issued to him in con- sideration of said $1,000,000 worth of patents: said trustee then divided the stock, as previously understood and agreed on, including a small percentage to the patentees. In order to provide i working capital/ the stockholders assessed themselves in a percentage of their stock, which was set aside as ' treasury stock/ to be dis- posed of at whatever price it could be sold for. In this way some money was raised, but not enough to do any real business, and consequently nothing was done beyond making exhibition runs of the motors, and getting flour- ishing accounts into the newspapers, on the strength of which the individual members ' peddled ' their stocks. " Among those who bought stock was a gentleman of means, as well as culture and refinement, and strict integrity. In some way he was induced to loan the company money from time to time on its notes, and this kept it alive a while longer. Indeed it began to look as if some real business might be done after all. A com- pressed-air locomotive was built and tested on the 110 STEEET RAILWAY MOTORS. elevated railroad, which succeeded in hauling their four- car trains, loaded with passengers, the whole length of the road ; making all the stops to receive and deliver passengers, making the schedule time, and, in fact, doing practically everything which the steam locomotives were required to do. At the end of the trip it was found that a sufficient surplus of compressed air remained in the reservoirs to insure against possible failure ; and, as will be shown later, the economy was beyond question. For some unexplained reason, however, this success was not followed up, and eventually a sudden and complete col- lapse was brought about by the sudden and sad death of the gentleman referred to, in whose estate the com- pany's overdue notes were found. " The inside workings and manipulations of this straw company, with paper capital, would make interesting reading ; but I trust enough has been said in the brief space allowable here to show that it was not an organi- zation well calculated to make a commercial success of such an undertaking, and is my explanation for the project being abandoned. Needless to say, it was a great disappointment to me. Those desiring to investigate further can be furnished with plenty of evidence as to the practical utility of the system, and the mechanical success of the experimental motors." Notwithstanding the success of the air motor on the Second Avenue Elevated Railroad and the favorable in- dorsement of the officers who made the tests, the directors were not inclined to incur at that time the expense of a change of plant, and the death of the capitalist who had advanced the money for the construction of the motor caused the abandonment of further efforts. It was in OTHER AIR MOTORS. Ill fact impossible for Mr. Hardie to take another step, as he had parted with his patents for a stock consideration which proved to be worthless, and the company had hy- pothecated these patents, which were its only assets, for loans that they were unable to pay. Mr. Hardie has prepared new plans with valuable im- provements, the old patents have nearly all expired, and the way is open for the introduction of air motors with- out fear of annoyance by hostile litigation. X. OTHER AIR MOTORS. THE newspapers from time to time publish notices of new motors which have a very brief existence and never pass the experimental stage. Some of these have been misnamed compressed air motors, but the air, instead of being applied to operate a piston in a metal cylinder, is used to communicate motion to some intermediate machinery, and the action depends upon the application of principles essentially different from those that have been utilized in the com- pressed air motors of Hardie and Mekarski. In one of these proposed systems a line of pipes about 6 inches in diameter was laid under ground in the middle of the track and rotated by steam, compressed air, or other power. An arm like the arm of a cable- grip car passed through a slot, like the slot of a cable- line, and carried small wheels which could be changed 112 STREET RAILWAY MOTORS. in position at the pleasure of the motor-man, and the rotation of which by contact with the revolving pipe communicated motion to the car. The speed was regu- lated by varying the angle at which the small revolving wheels were set. After an expenditure, it is said, of many thousands of dollars, this device proved a failure, and has been abandoned. Nearly half a century ago the engineering profession was entertained with occasional notices of a so-called atmospheric railway, which consisted of a pipe 36 inches, more or less, in diameter, laid under ground. On the top was a continuous slot, 2 inches wide, covered by a flap-valve of leather, rubber, or other elastic material. Inside the pipe was a piston carrying an arm through the slot like the arm of the grip in a cable-car. By exhausting the air in front, the atmospheric pressure behind would communicate motion to the piston, and as it moved the arm would open the flap-valve, which would close again behind it as it passed. A trial of this plan was made about 1840, on the West London Rail- way, and also on one or two other railways, but all were soon abandoned as unsatisfactory. The result of these trials clearly proved that the atmospheric railway system could not stand in competi- tion with that of the locomotive engine, unless in some peculiar situations. Chambers's Encyclopedia refers to this contrivance, and states that the expense and care necessary to keep the tube with its valve in good work- ing order led to the removal of the atmospheric me- chanism from the various railways on which it was established, so that the history of atmospheric railways may be ranked under the chapter of failures. They CABLE AND ELECTRIC ROADS. 113 survive only in the form of pneumatic dispatch tubes for the conveyance of parcels, many of which are used in London. After fifty years, and in the face of this experience, it is calculated to promote a smile to read a notice in the papers of "A New Motor" and of the existence of a pneumatic power and motor company, which has re- vived the old atmospheric railway scheme, with the difference that, instead of the continuous slot and elastic flap-valve, the slot is covered by a continuous row of rigid slide-valves, which are opened by a projection in the power-bar as the piston passes along the tube, and closed by a similar device after its passage. There is no reason to believe that this device can be more effective than the old flap- valve ; but, on the contrary, must be more difficult and expensive to construct and maintain, and the loss by leakage in a continuous line of valves must be excessive. XT. CABLE AND ELECTRIC ROADS. CABLE and electric roads are too well known to re- quire any description. Many publications have been made, giving details of construction and explanation of principles, which would be entirely out of place in this volume, the object of which is chiefly to institute a com- parison between the different systems now in use, or proposed to be introduced, as to cost of plant and of 114 STREET RAILWAY MOTORS. operation, and the general results that would follow their adoption, as regards dividends upon capital and public accommodation. In the attempt to institute such comparisons, great difficulties are experienced from the unreliable character of the data furnished in public reports. There has been no uniform system of keeping accounts. Items of ex- pense are sometimes included in one report and omitted in another ; in some, interest will be included and in others excluded. The cost of plant varies greatly in different localities, and includes items, some of which are independent of, and others, in part, at least, propor- tioned to the length of road operated. Comparative estimates, to be of any value, or inspire any confidence in the results, must be based upon similar conditions as to the character of the work, the length of line operated, and the volume of traffic. As the data furnished by census, State, and other reports apply to roads of diverse lengths, characters, and conditions, an attempt will be made to take differences into consideration and make comparisons as fairly as pos- sible on a basis of uniformity. For this purpose a num- ber of miscellaneous results and data will be given, and an estimate then attempted of the cost of plant and working of a road of given length and given volume of business operated by each of the systems proposed to be compared. When it is considered that the reported cost of plant per mile on one road may be three or four times as much as on another, and that reported earnings and expenses vary as one to two or more, the necessity of some uniform basis of comparison will be obvious. CABLE AND ELECTRIC ROADS. 115 It is proper, therefore, to assume uniform conditions, and a road will be taken six miles long in a paved city, laid in substantial manner, with double track, heavy rails, a volume of business sufficient to require one 16- foot standard car every two minutes for an average of 16 hours. Horse-cars making 4 miles per hour, and motors 6 miles, and a reserve of 20 per cent, of horses, cars, and motors for extra service and contin- gencies. This will require 72 cars for the motor lines and 108 for horse lines, and, for the sake of uniformity, the equipments will be supposed to be combinations of car and motor in one, and having the usual seating capacity for 20 passengers. Such cars can be used with all motors, except steam and gas, where separate motors will be required. The daily car mileage with the data given will be 5760 miles, and the annual mileage 2,102,400. The combination motor should have power sufficient to haul on ordinary roads one, and on level roads two, trailers to meet the requirements of maximum business. To realize how little information can be derived from reports as to actual cost and expenses, where dissimilar conditions are not recognized, the following extract will be given : From Chicago Street Railway Journal, November, 1892, article by Mr. M. Eamsay, chairman of com- mittee, after correspondence with every cable road in the United States, and with the representative electric and horse railroads : 116 STREET RAILWAY MOTORS. Operating Statistics of Eight Gable Roads. Maximum. Minimum. Average. No. of grip cars daily . . 193 5 50 " trail " . 298 5 74 Daily mileage grip cars, each . 127 70 98 trail " " . 123 70 95 Receipts per car-mile, includ- ing mileage of trail cars . 29.84 15.10 20.20 Gross operating expenses per car mile, exclusive of fixed charges . . . .41.00 6.75 16.70 Net earnings per car-mile . 8.4 4.9 6.97 For Seven Electric Roads. Maximum. Minimum. Average. Motor cars daily . . .280 5 57 Trail " ... 5 4 41 Daily mileage, motor . . 127 70 101 " " trail . . .120 56 88 Receipt per car-mile, including mileage of trail cars . . 40.28 13.5 24. Gross operating expenses per car-mile .... 25.44 9.0 12.5 Net earnings per car-mile . 14.34 0.0 6.04 Notes from Street Railway Journal of July , 1892. Ten Cable Roads. Maximum. Minimum. Average. Length of line . . . 11.69 2.70 7.32 Length of all tracks . . 23.38 5.44 14.29 Number of grip cars . . 116 12 60 trail " 380 8 102 Indicated horse-power of en- gines 3400 200 1329 Cost per mile of line .. $683,840 $159,227 $290,940 CABLE AND ELECTRIC ROADS. 117 Ten Electric Roads. Maximum. Minimum. Average. Length of line . . . 11.71 2.80 5.56 " all tracks . . 16.35 2.80 6.72 Number of motor cars 47 2 12 " tow cars 15 2 4 Indicated horse-power . . 1050 35 237 Cost per mile of line . .$98,749 $8,807 $36,145 Ten Cable Roads Twelve Months' 1 Operation. Maximum. Minimum. Average. Car mileage .... 6,290,172 310,331 2,327,625 Passengers carried . . 36,218,807 1,340,820 10,199,569 Passengers per mile operated 4,261,036 437,628 1,355,965 Operating expenses per car mile 21.91 cts. 9.39 cts. 14.12 cts. " " per passenger 4.28 " 2.43 " 3.22 " 1242 standard car-miles per mile of line is an average of daily operation of cable lines. A comparative estimate of cable and electric roads, of equal capacity, gives nearly equal cost per mile. The cables are generally metropolitan and the electric sub- urban. Ten Electric Roads. Maximum. Minimum. Average. Car mileage . . ." 702,770 19,754 244,210 Passengers carried . . . 2,752,382 60,217 803,121 " " per mile . 470,090 14,795 222,645 Operating expenses per car mile 36.04 cts. 8.34 cts. 13.21 cts. " " per passenger 11.82 " 2.71 " 3.82 " EXTRACTS FROM CENSUS BULLETIN OF APRIL 24, 1892. The bulletin was prepared by Mr. C. H. Cooley, under the supervision of Mr. Henry C. Adams, of the Inter- state Commerce Commission, and covers statistics of 50 118 STREET RAILWAY MOTORS. lines of street railway, 10 operated by cable, 10 by elec- tricity, and 30 by animal power. The total cost of the 10 cable roads, including equipment, is given as $26,- 351,416. The total number of passengers carried was 101,995,695, at a total cost of $3,286,461. The operating expenses per car-mile were 14.13 cents, and the operating expenses per passenger carried 3.22 cents. The length of all tracks, including sidings, was nearly 143 miles. The total cost of the 10 electric roads, including equip- ment, is given as $2,426,285. Total track mileage of 67.22 miles. Passengers carried, 8,031,214, at a cost of $326,961, or 13.21 cents per car-mile and 3.82 cents per passenger. The expenses per car-mile on cable roads varies from 9.39 cents to 21.91 cents; on electric roads from 8.34 cents to 36.04 cents. The density of passenger traffic is about six times as great upon the cable as upon the electric railways. The editor of the Street Railway Journal, of Chicago, gives, from his own figures as secretary of the Chicago City Railway for 1890, cost of operation of cable cars, 9.65 cents per car-mile. The Philadelphia, Record gives, for three months on the West End Railway, of Boston : Expenses per Car -Mile. April . Electric, 21.75 cts. . Horse, 24.54 May . " 22.36 " . " 24.04 June . " 20.37 " . " 23.52 The Earnings were April . Electric, 34.05 cts. . Horse, 31.77 May . " 33.43 " . " 34.22 June " 42.71 " " 36.85 CABLE AND ELECTRIC ROADS. 119 Charles H. Davis, C. E., in a printed circular, gives some interesting facts and figures in regard to electric roads : Cost, including all Plant except Real Estate. A road of 2 miles with. 8 cars costs 3 4 5 6 8 10 12 10 12 15 20 25 30 40 $70,000 92,000 110,000 128,000 165,000 199,000 248,000 318,000 Investment and Operating Expenses Compiled from Edison Co. Electric. Horse. Cable. Real estate, road, and equipments per mile of street $38,500 $33,406 $350,325 track 27,780 31,093 184,275 Car-miles per annum per mile of street 76,158 43,345 309,395 Passengers carried per annum per mile of street 237,038 251,816 1,355,965 " per car-mile 3.10 5.80 4.38 Operating expenses per car-mile, cents 11.02 24.32 14.12 Interest at 6 per cent, on investment per car-mile, cts. 3.03 4.62 6.97 Total interest and expenses per car-mile, cents . . 14.05 28.94 20.91 Cost per passenger carried, interest excluded . . . 3.55 4.18 3.22 " " " " " included . . . 4.53 4.98 4.77 The cost of power on horse railroads has averaged as follows : New York City Philadelphia Chicago 8 to 9 cents per car-mile. 9 to 10 " " " 10 to 11 " " " 120 STREET RAILWAY MOTORS. CONDITIONS, AS PER DAVIS CIRCULAR. Day of 18 Hours. Speed. Electricity, 6| miles per hour, 120 miles per day. Horses, 4 miles per hour, 72 miles per day. Depreciation. Electricity (of power), 15 per cent. Horses, 20 per cent. Car repairs : Electricity of motors, 20 per cent. ; of cars, 10 per cent. Horse-cars, 5 per cent. Repairs. Track and line repairs : Electricity, 15 per cent. Horses, 10 per cent. Service. Three men per car: Electricity, $1.87 each. Horse, $1.60 each. Cost of Track and Line per Mile. Electricity, $10,000. Horse, $5000. Value of Car. Electricity, $3000, with motor. Horse, $1900, with 6 horses. Coal, 4 pounds per H. P., $4 per ton. Average Operating Expenses of 22 Electric Roads per car -mile. Highest. Lowest. Average. Maintenance of road-bed and track (cents) 1.80 0.10 .54 line .95 .01 .12 power plant .86 .05 .36 Cost of power 4.95 .48 1.96 Repairs on cars and motors 5.24 .59 1.80 Transportation expenses 9.47 2.74 4.98 General expenses 2.95 .79 1.26 Total 22.99 7.80 11.02 Another statement, including 7 electric roads, gives an average for Operating expenses, per car-mile Cost per passenger carried 9.83 cents. 3.28 " CABLE AND ELECTRIC ROADS. 121 ESTIMATES OF COST. The comparative estimates of cost by the different systems will be made, as previously stated, by assuming similar conditions in all cases, viz. : Length of road, 6 miles; of single track, 12 miles. Cars in use on motor lines, 60 ; reserve, 20 per cent. ; total, 75. Horse lines, 90, regular ; 112, total. Speed, motor lines, 6 miles per hour ; horse, 4 miles. Time, 16 hours per day. Daily motor mileage, 96 miles each ; daily motor mileage total, 5760 miles. Daily car mileage of horse-cars, 64 miles each ; daily car mileage total, 5760. Number of horses to a car, 8 ; total horses, with reserve, 900. On many roads the speed is greater and the car mile- age proportionately increased ; but for a comparative estimate these figures will answer as well as others. Conductors, engineers, motormen, and gripmen will be allowed $2 per day ; fireman and drivers, $1.50. For horse-stalls it will be proper to allow stalls 5 by 9 and 5 feet to middle of passage ; total per horse, 70 square feet. For each car, 250 square feet, to allow for passages and for price of lots, $1.50 per square foot. To utilize space, cars can be placed on the ground floor, and horses partly on first and partly on second floor. The space required for cars on the horse line will be 28,000 square feet, and for horses, 63,000 ; in addition to this, about 2000 square feet must be allowed for offices, making a total of 93,000, or 100,000 square feet of floor space. Of this, 20,000 feet of first floor can be used for stalls, and all of the second floor, so that the whole ground area will be 50,000 square feet. 122 STREET RAILWAY MOTORS. HORSE RAILROADS. Cost of Plant. Track, 1 mile of double track, laid with 65-pound rail, including ties, spikes, etc. $20,000 Paving, 9282 sq. yds. granite paving, 14 feet wide, 4 feet between track, and 1^ feet on each side, at $3 per square yard Cost of one mile ...... Cost of six miles ...... Car-sJieds, Stables, and Offices. Land, 50, 000 square feet, at $1.50 . . $75,000 Buildings, offices, car-sheds, and stables . 80,000 Total for land and buildings . . . $155,000 Cars and Horses. 900 horses, with harness, wagons, etc., $150 . $135,000 112 cars, $1000 . 112,000 $247,000 Total cost of plant for six miles . . $689,076 Expenses of Operation. Feed for 900 horses, at 34 cents per day . . $306.00 Repairs of harness, l T 2 ff mills " " . . J0.80 Shoeing horses, 6 T 8 ^ mills " " . . 56.70 Stable expenses, 1.15 cents " " . . 103.50 Replacing horses, 6 T 3 o mills " " . . 56.70 $533.70 Per horse per day, 60 cents ; per year, $219. Per car-mile for stable expenses, W& 9 - 26 cents. CABLE AND ELECTRIC ROADS. 123 OTHER EXPENSES. The other expenses of operation can be taken from the former estimate based on the Second Avenue Rail- road data by Cars, repairs, conductors, and drivers, per car-mile 8.00 cents. Track repairs 1 68 " General and incidental expenses . . . 5.30 " 14.98 Add expenses of power, as above . . . 9.26 " Total expense of horse-car service per car-mile 24.24 cents. CABLE ROADS. Notes from Fairohild on Street Railways. The average horse-power to 1000 feet of cable is 4.6. The power to move cable alone is from 35 to 75 per cent, of indicated horse-power of engines at station. To determine approximately the amount of steam horse-power required for a line less than 10 miles of rope, allow 4-horse power to each 1000 feet of rope, each 90 bend equal to 1500 feet straight, with addition of 3-horse power for each car and 60 horse-power for ma- chinery. If the power required for propulsion of cars be taken at 3 H. P. per car, on line including reserve, the power required for 75 cars would be 225 on the line; and as this is generally estimated at 40 per cent, of the steam horse-power at the central station, 60 per cent, being absorbed by friction and other resistances of rope and machinery, the power to be provided in engines and 124 STREET RAILWAY MOTORS. boilers would be 562 H. P., or, in round figures, 600 H. P. If the second rule be applied, 12 miles of cable = 63360 feet, and at 4 H. P. per 1000 feet = 252 H. P. Allow 4 right-angled turns in the 6 miles; thus 4 x 1500 = 6000, and 6 X 4 =24 H. P. to be added for turns. 75 cars at 3 H. P. per car 225 H. P., and the allow- ance of 60 H. P. for machinery makes the total 561 H. P., or almost the same as before. For electrical lines the actual percentage of the steam- power utilized at the motor car is said to be from 30 to 40 per cent., so that the loss in transmission may be as- sumed as the same as in cable lines, 60 per cent., and the power required for propulsion is also nearly the same. This will make the steam-power required for cable and electric lines at the central station about the same. For a pneumatic or compressed air line, running 75 cars at intervals of 2 minutes, the quantity of free air required per minute is 1800 cubic feet, and the horse- power required about 550, so that in all these systems the power required at the central station is practically the same for equal work on the track ; but while 60 per cent, of the power on cable and electric lines is lost in transmission, on the compressed air line the power lost in compressing the air is fully restored in reheating, as has been shown, and there is no loss in transmission ; but it requires much more power to operate a motor than to move a given weight by direct application of the power of a rope through a grip. This equalizes the power re- quired at the central station. In computing the cost of plant and of operation of cable roads, the large area occupied by stables will be dispensed with, but the car-sheds must be retained and CABLE AND ELECTRIC ROADS. 125 a separate building is required for power-house. The number of cars being 75, will require 18,000 square feet and the offices 2000 square feet. The power-house and plant will require about 100 X 200 = 20,000 square feet ; in all, 40,000 square feet. The track, so far as rails and paving are concerned, will be the same as estimated for horse roads ; but the special constructions required for the use of the cable add very largely to the expense. Power-house, Car-house, and Machinery. Real estate, 40,000 sq. ft. ground, $1.50 . . $60,000 Buildings 80,000 Engines and boilers, settings, etc., 600 H. P. 30,000 Driving machinery ..... 40,000 Foundation, heaters, pumps, and sundries . 10,000 Cost for 6 miles . . , $220,000 Average cost for one mile .... 36,666 Estimate for Street Construction on One Mile of Double Track. Track per mile . . . ... . $20,000 9282 square yards paving, $3 .. . . 27,846 6600 cubic yards track excavation, 75 cts. . 4,950 2640 cast-iron yokes, 350 Ibs. = 2,755,000 Ibs., 1 cts. . .. 13,860 293 carrying sheaves, $3.75 ... 1,100 7040 yards, 50 Ibs. per yard, steel slot-rails, 2 cts. per ]b 8,800 51333 Ibs. manhole covers and frames, If . 898 3323 cubic yards Portland cement concrete, $8.50 . . . . - . . 28,333 5280 feet double-track laying, $1 . . . 5,280 Sewer connections . . . . . 3,000 10727 lineal feet steel- wire cable, at 33 cts. . 3,576 Cost of one mile double track . . $117,643 Cost of six miles double track . . 705,858 126 STREET RAILWAY MOTORS. Special Construction. Main vault at engine-house and fixtures . $8,000 Two end vaults with fixtures .... 5,000 Special sheaves, crossing curves, etc., curve . 18,000 Total for 6 miles $31,000 Rolling-stock. 75 Combination grip and pasjfenger cars at $2200 each $165,000 Summary of Cost of 6 Miles of Cable Line, Double Track. Power-house, real estate, and buildings . . $220,000 General street construction .... 705,000 Special street construction .... 31,000 Rolling-stock 165,000 Engineering, legal, and miscellaneous . . 20,000 $1,141,000 Cost of plant, one mile .... 190,166 In the attempt to estimate the cost of operation of a cable road based on the cost of one of shorter length, it does not seem reasonable to assume that the depreciation of cable will be simply in proportion to length, but in a much higher ratio. If length is doubled, the strain for any given length will also be doubled, and the friction and wear should be at least quadrupled. The wear of sheaves and pullies will also be increased to a great extent. It would seem reasonable, in the absence of positive data, to estimate the expenses of repairs and removals of rope, sheaves, pulleys, and other street construction, including grips, as fully equal to the cost of repairs of motors in other systems ; and if this be conceded, there will be a close approximation to identity of cost of power under similar conditions of the systems in general use. ELECTEIC LINES. 127 Cost of Operation of 6 Miles of Double-track Cable Road, per Day of 16 Hours. 13| Tons of coal for 600 H. P., $3 ... $40.50 Water and grease ...... 6.50 Depreciation of rope ..... 140.00 Depreciation of plant and rolling-stock . 78.00 120 Gripmeu and conductors, $2 . . . . 240.00 Engineers and firemen . . . . . 25.00 Car-house service, cleaning, inspecting, etc. . 20.00 Power-house expenses ..... 40.00 Track services 16.00 Repairs of engines and machinery . . 26.00 Repairs of cars, trucks, and grips . .. . 100.00 Repairs of track and buildings . . . 60.00 Train, shop, and miscellaneous expenses . 25.00 Accidents 20.00 Legal, secret service, and insurance . . 10.50 General and miscellaneous .... 50.00 5760 car-miles, cost $897.50 Cost per car-mile, $13.94 cents. This estimate, based upon prices given by various authorities, may be, in some items, in excess ; but as the same prices will be retained for other systems, the effect will be to increase slightly the daily total without mate- rially affecting the comparative estimates, which in this investigation are of most importance. XII. ELECTRIC LINES. (FROM VARIOUS AUTHORITIES.) THE cost of steam power-house plant complete, in- cluding building and smoke-stack, is rated, for high- speed and non-condensing engines, at from $45 to $60 128 STREET RAILWAY MOTORS. per horse-power ; for compound engines, from $60 to $75 ; and for electrical equipments, $35 to $45 per horse-power. The usual unit of horse-power is 8 square feet of heating surface, evaporating 30 Ibs. water per hour for sectional or water-tube boilers, and 15 square feet for tubular. The following table gives, approximately, the horse- power at axles required to propel a 16-foot car, weigh- ing, with its equipments and a moderate load of pas- sengers, 5 tons, up grades of from 1 to 10 per cent., at the uniform rate of 8 miles per hour. On ordinary street-car tracks the traction is said to average about 20 Ibs. per ton, but is sometimes more, and the commer- cial efficiency of the motors must be taken at 60 per cent. Thus, for a level track, the power required will be -| f\r\ 5280 X8n-60x20x5^- 33,000 x = 3.5 horse- power at axles ; and for grades, as follows, from 1 to 10 per cent.: = 3.5 H. P. 6 = 22.5 H. P. 1 = 6.5 2= 9.5 3 = 13.0 4= 16.0 5 = 19.0 7 = 25.5 8 = 28.5 9 == 32.0 10=35.0 It is very important, in the management of an elec- trical plant, that the number of power units should be such that the disabling of one of them will not interfere with the success of the system, and the same remark is also applicable to other systems. On the East Cleveland Electrical Road, 70 motor cars and 70 trailers are in daily use. One electrical horse- power is obtained for every five pounds of slack or four ELECTRIC LINES. 129 pounds of nut coal. Evaporation, 7J pounds of water per pound of slack. ELECTRIC TRACTION EFFICIENCY. Of the total indicated horse-power developed by ordinary engines, 10 per cent, is consumed by the friction of the running parts. The loss at the dynamo is from 10 to 15 per cent., being about 75 per cent, of the indicated horse-power as the station efficiency. The line efficiency is generally about 90 per cent. In the average of roads now in operation, the propor- tion of the indicated horse-power of the engines trans- mitted to the motor for propulsion of cars is between 55 and 60 per cent. The average efficiency of the car motors themselves may be taken at 75 per cent., so that the propulsion of the horse-power of engines actually applied to propulsion of cars is 60 X 75 per cent. = 45 per cent. In a ma- jority of cases it is stated that the actual commercial efficiency does not rise above 40 per cent. (Crosby & Hall, p. 228), which is about the same as in cable lines. Cost of Items entering into the Construction of Electrical fiailroads and Equipments, from Various Sources of Information. Single-track railroad, average per mile . . $10,000 No. copper wire to make track a good conduc- tor, per mile . . . .... . 400 Labor in laying wire and binding to rail, per mile 200 Wooden poles, 90 to the mile, placed, per mile . 600 Iron poles, 90 to the mile, placed, per mile . 2,500 Trolley wire, span wires, and insulators, per mile 700 Feed wire in place, per mile .... 1,000 9 130 STREET RAILWAY MOTORS. 1 mile single track, with wooden poles . . $13,000 1 " " " wire poles . . . 15,000 Car bodies, ready for motors, 750 to 1500 dollars, average each ....... 1,000 Long bodies, $1250 to $2000, each average . 1,625 Trucks for long cars ...... 600 Two 15-horse motors, from 1800 to 2500 dollars. If one motor is used, from 1100 to 1800 dollars. Car ready to operate (electrical equipment, $2250) 3,500 For station power-plant complete, allow per horse- power ........ 50 For station electrical plant .... 40 For both plants 90 Investment in station machinery, per car operated 1,350 Keal estate may be generally covered by $50 per H. P. of station, or by $750 per car operated, but is extremely variable. Average of 22 electric lines gives cost of power, as reported, 2.32 cents per car-mile ; but published reports are usually unreliable. Cents. Maintenance of line is covered by 5 per cent, of cost, say per car-mile ..... 0.4 Maintenance of track is covered by, per car-mile 1.08 Maintenance of car bodies and trucks, per car- mile 0.72 Conductors and motor men . . . . 4.50 Summary of Expenses as given by Crosby & Hall, page 320 of Electric Railway. Cents. Power delivered on line per car-mile . . . 1.35 Repairs 011 electric machinery of car . . . 1.00 Repairs on line 0.43 Conductors and motor men . . . . .4.50 Repair on cars and track . . . . .0.72 Maintenance of roadway ..... 1.08 General expense 2.00 Accidents 0.25 11.33 ELECTRIC LINES. 131 The cost of a trail car would be covered by 5 to 6 cents per mile. The expenses of the West End Rail- way of Boston for an average of 5 months were per car- mile operated by electricity : Cents. Motor power ....... 7.44 Car repairs 1.33 Damages 0.43 Conductors and drivers ..... 7.14 Other expenses s . . . . . .4.78 Total expenses 21.12 From which it appears that the actual cost on the West End Railway was nearly twice as great as the sup- posed average estimate above given by Crosby & Hall. An estimate will now be made of the cost per car- mile of electrical railway service based on the conditions stated, viz : Line 6 miles double track, service two-minute inter- vals, cars 60, reserve 15, horse-power at station 600, daily mileage 5760 miles. Power-house, Car-house, and Machinery. Real estate, 40,000 sq. ft. ground at $1.50 . $60,000 Buildings 80,000 Engines, boilers, settings, etc., for 600 H. P. . 30,000 Station machinery 25,000 Foundations, heaters, pumps, and sundries . 10,000 Cost for 6 miles $205,000 Proportion for one mile .... 34,166 132 STREET RAILWAY MOTORS. Estimate of Street Construction for One Mile of Double Track. Track, one mile $20,000 9282 square yds. paving, $3 . . . . 27,846 Track wire laid 1,200 180 iron poles 5,000 Trolley wires, span wires, and insulators . . 1,400 Feed wires in place ...... 2,000 Total street construction .... $57,446 Cost for 6 miles $344,676 Equipment. 75 car bodies, trucks, and motors, $3500 . . $262,500 Summary for 6 Miles. Power-house and plant $205,000 Street construction 344,676 Equipment 262,500 Auxiliary appliances 15,000 Special construction ...... 5,000 Engineering, legal, and miscellaneous . . 20,000 Total cost for 6 miles $852,176 Cost of Operation of Six Miles Double-track Electric Line per Day of 16 Hours. 13 tons of coal for 600 H. P., $3 . . . $40.50 Water, oil, and grease ..... 6.50 Depreciation of plant and rolling-stock . . 78.00 120 motor men and conductors, $2 . . 240.00 Engineers, firemen, and dynamo tenders . 35.00 Car-house service, cleaning, inspecting, etc. . 30.00 Power and car-house expenses . . . 12.00 Track service 16.00 Repairs, engines, working of line, miscel- laneous ....... 26.00 Repairs of cars, trucks, and motors . . 140.00 ELECTRIC LINES. 133 Repairs of track, overhead construction, buildings $80.00 Track cleaning, train, and shop expenses . 25.00 Accidents 20.00 Legal, secret service, insurance . . . 10.00 General and miscellaneous .... 50.00 5760 miles $809.00 Cost per car mile, 14.04 cents. It appears that with equal length of road and equal car mileage the cost of operation of cable and electric lines is nearly the same on both. The depreciation of cable is about offset by the repairs of overhead wires, and dynamo tenders, other items the same. GENERAL SUMMARY. Cost of Plant and of Operation, for Six Miles of Double Track Operated by Horse-power 2-minute Intervals. Land $75,000 Buildings 80,000 . Track and paving ...... 287,076 Horses 135,000 Cars 112,000 Cost of plant $689,076 Interest at 6 per cent. ..... 41,345 Car-miles per annum . . . . . 2,102,400 Interest per car-mile ..... 2 cents. Cost of operation, without interest ... 24 cents. Cost of operation, with interest on plant . 26 cents. Cost of horse-power, not including drivers . 9 cents. 134 STREET RAILWAY MOTORS. Cost of Plant and of Operation of Six Miles of Double Track Operated by Steam Motors 2-minute Intervals. Land $60,000 Buildings and machinery of shops . . 100,000 Track and paving 287.076 Rolling-stock 300,000 Miscellaneous 20,000 Cost of plant $767,076 Interest at 6 per cent 46,025 Car-miles per annum ..... 2,102,400 Interest per car-mile ..... 2.09 cents. Cost of operation, without interest, per car-mile 21.22 cents. Cost of operation, with interest, on plant per car-mile ...... 23.31 cents. Cost of steam-power alone, without engineer or fireman per car-mile ..... 9.50 cents. Cost of fuel alone . . . . . . 2.65 cents. Cost of Plant and of Operation of 6 Miles of Double Track Operated by the Ammonia Motor Intervals between Cars, two Minuter. Although the data furnished by the actual operations at New Orleans do not exhibit any economy as compared with steam, yet when it is considered that the principal work in generating power is done in a stationary instead of a locomotive boiler, in which fuel can be used at half price, with at least 50 per cent, more evaporation, it is reasonable to assume that in a properly constructed and operated plant there should be a saving, as compared with steam motors, of at least $75 per day in fuel. If separate motors are used, there will be no reduction in the cost of plant ; but if the motors and cars are com- bined, less ground will be required, making a saving of $18,000. ELECTRIC LINES. 135 Assuming minimum expenditures, the estimate will be: Land, 22,000 sq. ft., $1.50 .... $33,000 Building and apparatus . 80,000 Track and paving 287,076 Rolling-stock, 75 cars and motors, $3500 . 262,500 Miscellaneous 20,000 Cost of plant $682,576 Interest at 6 per cent. .... 40,954 Car-miles per annum 2,102,400 > Interest per car-mile ..... 1.95 cents. Cost of operation per car-mile, without interest 19.92 cents. Cost of operation, with interest on plant . 21.87 cents. Cost of power alone, without engineer or fire- man ....... 8.20 cents. Cost of fuel alone 1.30 cents. HOT-WATER MOTOR. No separate estimate is required. The cost in every particular may be taken as the same as steam, both as regards plant and operation. Any slight saving by the first charge of hot water is fully offset by disadvantages and expenses in pumping back the water for reheating on return-trip. If not pumped back, the loss will be still greater. Cost of Plant and Operation of 6 Miles of Double Track Operated by Gas Motors 2-minute Intervals. As it is proposed in cities to use independent motors, the cost of plant will be taken as the same as steam, with a deduction of $500 each in the cost of motors, making them $2500. The fuel for motor and car will be taken at 1^ cents per mile run for the train. No fireman re- quired. 336 STREET RAILWAY MOTORS. Estimate. Land $60,000 Building and shop machinery . . . 100,000 Track and paving 287,076 Rolling stock . 262,500 Miscellaneous ...... 20 000 Cost of plant ...... Interest at 6 per cent. .... Car miles per annum .... 2,102,400 Interest per car mile .... 2.08 cents. Cost of operation per car-mile, without interest 17.62 cents. Cost of operation per car-mile, with interest . 19.70 cents. Cost of power alone, without motor man, per car-mile . 7.30 cents. Cost of fuel alone per car-mile . . . 1.30 cents. 'Cost of Plant and of Operation of 6 Miles of Doable Track Operated by Compressed Air Motors Z-minute Intervals. Land $33,000 Buildings and machinery, for repairs . . 80,000 Engines, boilers, setting .... 30,000 Pipes and reservoir ..... 5,000 Track and paving ..... 287 076 Rolling-stock 262,500 Miscellaneous . . . . . . 20,000 Cost of plant ...... $717,576 Interest at 6 per cent 43,055 Car mileage per annum .... 2,102,400 Interest per car-mile 2.05 cents. Cost of operation per car-mile, without inte- rest on plant 13.16 cents. Cost of operation per car-mile, inclusive of interest on plant 15.21 cents. Cost of power alone per car-mile, including repairs 4.10 cents. Cost of fuel alone per car-mile ... 7 mills. ELECTRIC LINES. 137 Cost of Plant and of Operation of 6 Miles of Double Track Operated by Cable %-minute Intervals Land .... V ">*. . . $60,000 Buildings . 80,000 Engines, boilers, setting, and machinery . 80,000 Track and paving 287,076 Rolling-stock 165,000 Street construction 448,924 Miscellaneous 20,000 Cost of plant $1,141,000 Interest at 6 per cent 68,460 Car-miles per annum 2,102,400 Interest per car-mile ..... 3.25 cents. Cost of operation per car-mile, without inte- rest 13.94 cents. Cost of operation per car-mile, with interest 17.19 cents. Cost of power alone per car-mile . . 5.85 cents. Cost of fuel alone per car-mile ... 7 mills. Cost of Plant and of Operation of 6 Miles of Double Track Operated by Electric Lines %-minute Inter- vals. Land . . .*" " $60,000 Buildings . . . . . ... 80,000 Engines, boilers, setting, and machinery . 65,000 Track and paving 287,076 Trolley wires, connections, etc., in street . 56,600 Rolling-stock / 262,500 Miscellaneous . . . . 20,000 Cost of plant . . . .-.'.' $831,176 Interest at 6 per cent 49,870 Car-miles per annum . . . . 2,102.400 Interest per car-mile 2.37 cents. Cost of operation per car-mile, without inte- rest 14.04 cents. Cost of operation per car-mile, with interest 16.41 cents. Cost of power alone per car-mile . . . 4.25 cents. Cost of fuel alone per car-mile ... 7 mills. 138 STREET RAILWAY MOTORS. XIII. LOW-PRESSURE AIR MOTORS. A METHOD of propelling street cars by the use of compressed air, at a low pressure of 100 Ibs. per square inch, was proposed in San Francisco. The car reser- voirs were to be of about 50 cubic feet capacity and placed overhead or under the seats, where they would be out of the way and would not interfere with the seating capa- city. An underground pipe was to be carried between the tracks, the diameter of pipe 4 to 6 inches, and at intervals of 500 feet a nozzle was to be provided, to which attachment could be made to renew the supply of air in the reservoirs when necessary. This system seems to have been proposed to remedy a purely imaginary difficulty. It was assumed that there was great loss of power and great expense in compressing air to high tension and that great economy would result from the use of lower pressure. It has been shown that the cost of fuel in compressing air to 500 pounds is only 7 mills per car-mile, which constitutes but about 5 per cent, of the whole expense of operation and even if some economy should result from lower compression, which is doubtful, it would not compensate for the very serious objection of frequent stoppage to replenish the supply. In the pamphlet which advocates the merits of the low-pressure system, objections to the high-pressure are stated ; but there are none that have not been fully con- LOW-PRESSURE AIR MOTORS. 139 sidered and answered. There is, however, an objection to the cable urged by the writer that has much force, and that is, that the power of the cable must be sufficient for the maximum business at the most busy hours of the day, and that this same power must be expended when the travel is a minimum, if there is only a single car upon the line. To avoid this great waste of power it is stated that some cable lines have stopped the machinery at night and substituted horse-power. Cables are eco- nomical only with a very large volume of business, and similar objections, although not to so great an extent, apply to electric lines. A current must traverse the whole line or section of line wire for a single car. There is always a serious loss in the transmission of power to long distances from the generating plant, and for this reason, as for others named, independent motors which carry their own power are far preferable. CARBONIC ACID MOTOR. The New York World, of July, 1892, contained a long article presenting the claims of a new motor to be operated by carbon dioxide, usually called carbonic acid. It was claimed that 10 horse-power could be obtained from 6 T 7 Q- pounds of the gas, at a cost of 20 cents for 24 hours ; that pressures of from 1000 to 5000 pounds per square inch could be produced, and that this " wonderful motive fluid" was to be used even for road vehicles and for agricultural purposes. The absurdity of such claims is self-evident. Car- bonic acid condenses into a liquid at 570 pounds per square inch, and there can be no further condensation. 140 STREET RAILWAY MOTORS. It is impossible to secure more power from the expan- sion of a gas than was expended in its compression ; and even if a pressure of 5000 pounds were attainable, it could not be utilized, as was shown in the Beaumont tests, until reduced to a working pressure of about 200 pounds. Further comment is unnecessary. XIV. STORAGE BATTERIES. No estimates have been made upon a line operated by the use of storage batteries, for the reason that no data are at present available. Up to the present time it is understood that the cost exceeds that of the cable and trolley lines; but it is claimed that greater economy has already been secured than by the use of horse-power, and that improvements are constantly reducing the ex- pense. It may be that there is a future to the storage battery that will in time enable it to supplant the trolley, which would be a most devoutly to-be-wished-for con- summation. The trolley is not only unsightly by its poles and overhead wires, and annoying by its loud humming noise, but it has proved destructive to life by contact with live wires ; and the obstruction to the free use of the fire apparatus by overhead wires has caused losses greater than the cost of the lines themselves, of which a recent fire in Boston is an illustration, if the newspaper accounts can be relied upon. In addition to this, lines are liable to be deranged by electrical storms in summer and in winter by snow and ice on rails and STORAGE BATTERIES. 141 feed wires, which break the electrical connections. The latter evil might not be entirely remedied by the storage battery, but it would give an independent motor and avoid blockades all along the line from any trouble at the power-house. The position will probably not be controverted that the motor and system of transportation that commends itself most highly to the approval of the public and of capitalists is the one which best fulfils the following conditions : 1. Minimum cost of plant. 2. Minimum cost of operation, including interest on plant. 3. Independent motors not liable to stoppage in transit by derangement of station machinery. 4. Minimum disturbance of streets, pipes, and sewers. 5. Avoidance of unsightly structures, danger from shocks, or impediments to the free use of fire apparatus. 6. Surplus power in motor for attachment of trail cars at hours when increased capacity is demanded. 7. Freedom from liability to delay in transit from storms, ice, or sleet. The several systems will be compared with reference to the above conditions. Comparing the different systems that have been under consideration, by including in the operating expenses per car-mile the interest on the cost of plant, which is obvi- ously the only true basis of comparison, the following results are presented in the order of relative economy. The first column gives the cost of operation per car-mile, including interest on plant ; the second the cost of power 142 STREET RAILWAY MOTORS. per car-mile, and the third the cost of fuel alone per car- mile in cents : Comparison of Motors. Cents. Cents. Cents. Compressed air motors . 15.21 4.10 0.7 Electric trolley lines . 16.41 4.25 0.7 Cable lines . . . 17.19 5.85 0.7 Gas motors . . . 19.70 7.30 1.30 Ammonia motors . . 21.87 8.20 1.30 Steam motors . . . 23.31 9.50 2.65 Hot-water motors . . 23.31 9.50 2.65 Horse-power . . . 26.00 9.00 0.00 The relative economy in regard to cost of plant is as follows : 1. Ammonia motor $682,576 2. Horse-power 689,076 3. Compressed air 717,576 4. Gas motor . 729,576 5. Steam and hot-water motors . . . 767,076 6. Electric lines 831,176 7. Cable lines 1,141,000 Ammonia being the lowest in cost of plant, the other systems increase in the following percentages : Horse- power, 1 per cent. ; compressed air, 5 per cent. ; gas, 7 per cent. ; steam or hot water, 12 T 3 ^ per cent. ; electric, 18 per cent. ; cable, 40 per cent. Ammonia Motor. This system is independent, requires no overhead obstructions or disturbance of streets, carries its own power, and is not liable to interruption from trouble at the central station. It ranks fifth in economy of operation. There seem to be difficulties connected with its use, as it was abandoned after a short period of STORAGE BATTERIES. 143 use in New Orleans in favor of the hot-water motor as being "cheaper and less troublesome" Horse-power. Horse-power needs no explanation. It is independent and generally reliable, but too slow for any approach to rapid transit. It requires no special construction in and causes no obstruction to streets, but in economy of operation it is at the foot of the list. It also creates nuisances by requiring stables and causing deposits in streets which, when dry, are blown into houses. Compressed Air. Compressed air seems to fulfil every condition as a perfect motive power. It stands at the head of the list in economy. In cost of plant it is only 5 per cent, above the minimum, but in cost of operation it is 8 per cent, below the next on the list. These motors are independent, there can be no losses by radiation or con- densation. The charge of motors can remain for hours until used. The plant should always consist of a number of units, and the derangement of one will not affect the rest or disturb the operation of the line. If considered desir- able, air can be transmitted, without sensible loss, to dis- tant points to reinforce motors, if, from any cause, such supplies should become necessary. The speed is unlimited, except by municipal regulations. The track is a surface line requiring no disturbance of streets except to lay the track. There is no possibility of explosions, as with steam ; no shocks, as with electricity ; no stoppage by break of circuit from ice on rail or wires ; no collisions from inability to detach grip, as in cable lines ; and no occupation of valuable space by motor machinery, as all such machinery is under the floor of the car or beneath the seats, and entirely out of view ; no skilled engineer 144 STREET RAILWAY MOTORS. is required, as an ordinary car driver can learn to ma- nipulate the lever in a single trip. The motor can have any amount of surplus power to allow one or more trail cars to be attached under one conductor, when business is at a maximum, and thus secure public accommodation at a minimum of expense ; and the ability to use increased power when needed does not cause a waste at other times, as no more air can be used at any time than is required for propulsion, and in running down grade the motor cylinders act as brakes and also as pumps to pump back air into the reservoirs. It will thus be seen that there is not one of the con- ditions enumerated as desirable in a perfect motor that this does not fulfil ; and, on the other hand, it is not known that a valid objection has ever been found, or, in fact, any objection, that has not originated in the igno- rance of the maker. The system is not only adapted to surface roads, but is also the best possible for elevated and underground roads. An explanation has been given of the causes which prevented its introduction after the satisfactory test of 1879 and 1880. Gas Motors. The Connelly Gas Motor, which is the only gas motor known to the writer, has been in process of development for six years, and seems to be a triumph of mechanical skill, combining strength with simplicity and compactness. It promises to be successful, but has not as yet the test of actual experience to inspire confi- dence. This is an independent motor, free from all the defects of the horse, cable, and electric systems, and very eco- nomical in cost of fuel, although in several of the sys- STORAGE BATTERIES. 145 terns fuel forms a very inconsiderable portion of the total expense. Steam and Hot Water. These motors are classed together as equivalents. They are independent motors not liable to stoppage from derangement of any central plant ; require no special construction or changes in sur- face roads. The disadvantages are that they must carry a supply of fuel, require a fireman and engineer, must use separate motors, are liable to accidents from explo- sions, and are objectionable from exhaust steam with its noise, and from smoke, cinders, ashes, and coals. In economy it stands fifth on the list, horse-power alone being more expensive. It is true that these motors may be run without firemen ; but if the engineer is required to attend to firing, accidents and collisions may occur while his attention is diverted from the lookout, especi- ally in crowded thoroughfares. Electric Lines require ground connection below the rails and posts and trolley wires overhead. The motors are not independent, but must receive power from the central station, and are liable to be burned out by elec- tric storms in summer or impeded by break of circuit from ice on track or feed wires in winter. Perhaps the most serious objection arises from the impediment to the free use of apparatus for extinguishment in case of fires, and the obstructive and unsightly appearance of poles and trolley wires. Electric lines stand second to com- pressed air in cost of operation, and sixth in cost of plant. Cable Lines have the same disadvantage as the elec- tric in being entirely dependent upon the central plant for the power of propulsion. Any stoppage there, or 10 146 STREET RAILWAY MOTORS. break of cable, stops every car on the line, and repairs are difficult and cause very serious delays. A broken strand has sometimes prevented the detachment of the grip and caused most serious accidents, one of which occurred recently in Chicago. The plant is much more expensive than in any other system, but in economy of operation its place is third. Many of the reports show greater economy of operation for cable than for trolley lines; but cable lines are generally metropolitan, and have a much larger patronage than the electric ; under similar conditions the superior economy disappears. For a light traffic the cable is not adapted. In this review of the various street railway systems it has been the aim of the writer to state facts, so far as he has been able to procure them from the sources of information within his reach, and to make comparisons without bias. If he has appeared to lean favorably towards compressed air, it has been from a conviction of its superior merit, and from the fact that he was called upon professionally to devote much time and attention to the investigation of this subject, and therefore claims the right to give opinions with confidence. He is aware that there is a very general impression that compressed air has been tried and has been found wanting. This is a grave error ; it has been tried and proved a great success. That it has not been generally used is the result of causes that have been here explained having no relation to its results. It is now in successful use in France, and has been for many years, although in mechanical construction the Mekarski motor is inferior to those constructed in New York and tested on the Second Avenue horse and elevated roads in 1879 and COST OF CARBONIC ACID AS A MOTIVE POWER. 147 1880, and the plans upon which these motors were con- structed have been much improved upon by the inventor since that date. XV. COST OF CARBONIC ACID AS A MOTIVE POWER. THAT carbonic acid is entirely too expensive to be used as a motive power can be readily demonstrated. It was stated in the article from the New York World, referred to on page 139, that the cost of the gas is never more than three cents per pound, and the following figures are given, viz. : 98 Ibs. sulphuric acid, at $8 per ton . . .15 cents. 100 Ibs. limestone, at $3 per ton . . . .784 Labor and compressing ..... .30 $1.24 Producing 44 pounds of gas, at a total cost of $1.24, which is 2.8 cents per pound. These figures are not far from the truth, but the power of the carbonic acid when produced is greatly overestimated. Using the exact chemical equivalents, 99.75 pounds of pure carbonate of lime unite with 97.82 pounds of pure sulphuric acid and liberate 43.89 pounds of car- bonic acid. Sulphuric acid is generally sold at one cent per pound, but in large quantities it may be less, and the assertion that it can be purchased by the ton at $8 will be assumed, for the purposes of this estimate, as correct, 148 STREET RAILWAY MOTORS. making the cost of carbonic acid, as stated, 2.8 cents per pound. The density of this gas at atmospheric pressure is 1.524, air being 1 ; and 8.5 cubic feet therefore will make one pound, and 43.89 pounds will give a volume of 375 cubic feet. The highest pressure at which steam, air, or gas can be used to advantage upon the piston of an engine is about 14 atmospheres. If higher pressures are devel- oped, they must be reduced to about 210 pounds before admission to the cylinders, as has been shown. 375 cubic feet condensed to 14 atmospheres = 27 cubic feet. Now, if 27 cubic feet of gas were admitted to a cyl- inder 27 feet long, to act on a piston of 1 square foot area and cut off at T * T of the stroke, the gas would be used in the most economical manner to secure foot- pounds of work, and the number of foot-pounds, at each stroke, would be found by multiplying the area of the piston by the average pressure (210 x .260) and by the length of stroke, 27. Thus, 144 x 210 x 0.260 X 27 = 212,274 foot-pounds. But 1 thermal unit = 772 foot-pounds, and 212,274 -f- 772 = 275 thermal units of work developed in each stroke. 27 cubic feet cut off at -^ will be sufficient for 14 strokes, and the 43.89 pounds of carbonic acid will therefore develop 275 x 14 = 3850 units, at a cost of $1.24. But 1 pound of coal will develop in combustion over 13,000 units, at a cost of 2J mills per pound, at $5 per ton; therefore, 1 pound of coal will produce a mechanical effect, at a cost of 2J mills, 3.37 times greater than the TRANSMISSION OF POWER BY MEANS OF PIPES. 149 44 pounds of carbonic acid, at a cost of $1.24. In other words, it would require 148.28 pounds of carbonic acid gas, costing $4.18, to produce the same mechanical effect in foot-pounds as could be obtained from the combus- tion of 1 pound of coal, costing 2J mills. Instead of being an economical source of power, the gas would cost nearly 1700 times as much as the coal, measured by the mechanical effect produced. The same article stated that the gas could be collected, compressed, and used over again. It would be practi- cally impossible to collect it, and if it could be collected no advantage could be gained, as it would be impossible to obtain from the gas, when compressed, an amount of units equal to more than half that expended in the com- pression. Air is the only gas that is suitable for com- pression as a motive power, and air costs nothing. Such schemes for producing power as that which has been considered would be unworthy of notice were it not that many persons are deceived by plausible repre- sentations and induced to contribute money for develop- ment, resulting in serious losses through ignorance of the natural laws upon which such operations are de- pendent. XVI. TRANSMISSION OF POWER BY MEANS OF PIPES. THE use of compressed air as a substitute for steam in the production of power requires -its transmission often to very considerable distances, and the losses in transmission become an important subject for determina- 150 STEEET RAILWAY MOTORS. tion. Unlike steam,, there is no loss by condensation whatever may be the distance to which the air is carried ; or if pipes and reservoirs are tight there is no loss, how- ever long the air may remain unused. Having been employed professionally to investigate and report upon the practicability of the transmission of steam for heating purposes by the system of Bird sell Holly, of Lockport, N. Y., the writer discovered, in the course of experiments and observations, that a relation existed between the discharges of elastic and inelastic fluids, such that the discharges of any elastic fluid, as air or steam, could be readily determined from the discharge of water under like conditions, and the law which defines the relations between water and any elastic- fluid may be thus enunciated : The discharge of elastic fluids through long pipes is equal to the corresponding water discharge under like conditions multiplied by the square root of the number which expresses the relative density as compared with water, and the product multiplied again by the square root of the initial density in atmospheres. The result will give the volume of discharge under atmospheric pressure. As the subject of the transmission of elastic fluids through pipes is of interest and importance in connection with the use of compressed air for power, and especially for the transmission of power to operate motors on ex- tended lines, a few pages devoted to the consideration of this subject and to the demonstration of the law that has been enunciated will not be considered inap- propriate. TRANSMISSION OF POWER BY MEANS OF PIPES. 1 51 DISCHARGE OF FLUIDS THROUGH ORIFICES. The velocity acquired by a body falling freely in vacuo is eight times the square root of the height, both the velocity and height expressed in feet and time in seconds. The velocity of fluids escaping through an orifice fol- lows the law of falling bodies, and is expressed by eight times the square root of the height in feet. This result is not practically correct, as the discharge is less than would be due to the full area of the orifice. The particles in escaping reduce the diameter by con- traction of vein to 0.8, and the area to about 0.64 of the full area of the orifice. In the case of elastic fluids the density of a vertical column would diminish from the bottom to the top, and the height, in estimating the volume of discharge, must be taken as that of a column of uniform density, the height of which would be equal to the pressure at the orifice. Where the discharge is made into a receiver contain- ing the same fluid at a reduced pressure, the differences in pressure must be taken in determining the height and velocity. A remarkable exception to this law has been an- nounced in a work on steam, published in London, 1875, by D. K. Clark, in which it is stated that the applica- tion of the formula for gravity is limited to cases in which the resisting pressure does not exceed about 58 per cent, of pressure which causes the flow. The flow is neither increased nor diminished by reducing the resisting pressure below about 58 per cent, of the abso- 152 STEEET RAILWAY MOTORS. lute pressure in the boiler. For example, the same weight of steam would flow from a boiler under a total pressure of 100 pounds to the square inch, into steam of 58 pounds total pressure, as into the atmo- sphere. The author states that for this remarkable discovery he is chiefly indebted to the experiments made by Mr. R. D. Napier, and refers to a report on safety-valves made to the Institution of Engineers and Ship-builders in Scotland in 1874. Desiring to obtain further information on this subject, I requested Prof. Geo. W. Plympton, former editor of Van Nostrand's Engineering Magazine, to see if he could find, in the libraries in New York, the report on safety-valves referred to. In a letter received in reply, he stated that he found the report at the rooms of the Society of Civil Engineers, but that it merely quoted the deductions of the experimenter, Napier, in the same form as previously given. Prof. Plympton also stated that Rankine discussed the same subject, and that Napier contributed articles to Engineering on this topic in 1872. If the conclusions of Napier be accepted as correct, it would appear that steam escaping from an orifice into the air at a pressure of 25 pounds, acquires a velocity of about 800 feet per second, and attains a maximum of 875 feet, after which the velocity remains constant, how- ever great the pressure. Some direct experiments on the velocity of steam escaping from an orifice, just completed by Messrs. Holly and Gaskill, of Lockport, give, in one case, 951 feet per second, and in another 1023 feet per second. TRANSMISSION OF POWER BY MEANS OF PIPES. 153 It is not difficult to understand that the velocity might be constant, for the velocity is that due to the height of a column of uniform density whose weight is equal to the pressure. Now, if the pressure should be doubled, the density and weight of a uniform column would also be doubled, and the height which determines the velocity would remain constant ; but the declaration that the weight of steam discharged remains constant requires confirmation. The efflux of steam through an orifice fortunately has but little influence on the discharge through long pipes where the velocities are comparatively low, and the results will not be aifected by any uncertainties in regard to the velocity of flow through orifices. RESISTANCE OF LONG PIPES TO* THE FLOW OF ELASTIC FLUIDS. This was one of the most important subjects connected with the practical and extended application of the Holly system, and one upon which comparatively little infor- mation could at that time be obtained from books. Mr. Holly stated that he had searched in vain for any reliable information on the subject, and the only table found published was headed, " friction of air, steam, and gas in long pipes/' without any recognition of the influence of density, which would cause, the results to vary in the wide range of from 4 to 10. It is proposed, therefore, to give this subject careful consideration. When engaged in maturing plans for tunnelling the Hoosac mountain, the writer made a series of experi- ments on the friction of air in a tunnel at Wiconisco. 154 STREET RAILWAY MOTORS. A pipe of wood was constructed about 1400 feet long and 110 square inches in area. The current of air was produced by a vacuum fan, driven by a steam engine, the velocities determined by an electrical apparatus, and the results demonstrated : 1. That the resistance was in proportion to the square of the velocity. 2. That the resistance was inversely as the diameter. 3. That the power required to pass a given quantity of air through pipes of different diameters was inversely as the fifth powers of the diameters. As a consequence, it was found that it would require a million times more power to pass the same quantity of air through a pipe one foot in diameter than would be required if the pipe were 10 feet. At the Mt. Cenig tunnel it was decided to use com- pressed air as a motor, and the preparatory experiments were made at government expense by a commission of gentlemen of eminent scientific attainments, consisting of Messrs. DeNerache, Giulio, Menebrea, Rura, and Sella. Special experiments were instituted on long lines of metallic pipe, continued by rubber hose, and observations made on pressure and velocity. The elastic force of the fluid was ascertained at the commencement and end of the pipe, and a curve traced for the interpretation of the results, from which a table was prepared, giving initial velocities in metres per second, diameters of pipes in decimals of a metre, and friction, or loss of tension in millimetres of a column of mercury. A copy of the report of this commission was procured through the kindness of Professor Gillespie ; from it a TRANSMISSION OF POWER BY MEANS OF PIPES. 155 table was calculated in which pressures were expressed in pounds, velocities in feet per second, and lengths in miles. In using tables for the friction of elastic fluids through pipes, one peculiarity is observable. With dense fluids, such as water, the head is an important element in calculating the loss by friction, but with elastic fluids the initial velocity is given and the head is not a neces- sary datum in the calculations where there is a free dis- charge ; but when there is back pressure it would seem that the initial density, as also the initial velocity, must be considered. The explanation is this : Suppose pressure should be quadrupled, the fluid being supposed perfectly elastic would be quadrupled in density, and the power required to move it at a given velocity which* measures the re- sistance would be quadrupled also, or would be as 1 to 4; but the velocity, being as the square root of the head or pressure, would be doubled also by quadrupling the head or pressure, and would be as 1 to 2, and the re- sistance would be (I) 2 : (J) 2 , or J. Hence, while the increase of density would quadruple the resistance, the reduction of velocity due to that pressure would reduce it to one-fourth, or the resistance of a given length with a given velocity would be constant. This conclusion may be reached by another process of reasoning : Where a fluid is discharged through a long pipe the pressure at the commencement is the head in the reservoir ; at the end where it discharges it is noth- ing, or simply the head due to the velocity. The hypothentise of a triangle, of which the base represents the length and the perpendicular the head, will be the 156 STREET RAILWAY MOTORS. hydraulic gradient ; and so long as head divided by length or hydraulic gradient is constant, the velocity is constant and the discharge also. Now, if head should be quadrupled, velocity remaining constant, length must be quadrupled also, and head divided by length, which represents the friction per unit of length, will be con- stant also, and will vary in the same pipe with the square of the velocity. In determining the resistance of different elastic fluids, density is an important element, which appears some- times to have been overlooked. That it is important will be obvious from the consideration that the power required to move a body is in proportion to the weight of the body moved, and the weight is in proportion to density ; if density should be doubled the resistance will be doubled, and if reduced the resistance will be reduced proportionately. Let us imagine two elastic fluids of equal height, but whose densities compare as 1 to 2. As the heights are equal, the velocities of discharge will be equal. On a line as above, representing a unit of length, draw a per- pendicular, 1, and complete the triangle ; draw a second perpendicular, 2, and complete the second triangle. The perpendiculars at any point will represent the pressure at that point, and the areas of the triangles will be proportioned to the total resistance. As these areas compare as 1 to 2, so will the loss by friction be as 1 to 2, or as the densities. The following are extracts from the report on the Holly system : TRANSMISSION OF POWER BY MEANS OF PIPES. 1 57 DEMONSTRATION OF THE LAW OF THE DISCHARGE OF ELASTIC FLUIDS THROUGH LONG PIPES. The quantity of steam discharged through a pipe of a given length and diameter under a given pressure, and the losses by friction and radiation, are questions which lie at the very foundation of the successful application of the Holly system, and without which it will be im- possible to form plans and prepare estimates for the supply of any given district, with confidence that mis- takes will not be committed, that the plans provided will not prove insufficient, and that mains will not re- quire to be torn up or duplicated after the lesson has been learned from dearly-bought experience that sound theory should have taught in advance. As it has been found impossible to procure from any known authors on hydraulics or pneumatics just that practical information that will meet the requirements of the present investigations, and as the writer has ven- tured to enunciate a fundamental law on which the solution of all problems relating to steam transmission must depend, and which is not only not contained in books, but is in conflict with rules given by some popular authors, no apology will be necessary for the time and space devoted to a demonstration of the law in question. This law may be thus enunciated : The discharge of steam, air, or any elastic fluid, under pressure through long pipes and at the volume due to atmospheric tension, is equal to the water discharged under like conditions multiplied by the square root of the number which expresses the relative density at atmospheric tension, as compared with water, multiplied 158 STREET RAILWAY MOTORS. also by the square root of the initial pressure in atmo- spheres. For example, air is 836 times lighter than water under ordinary atmospheric tension, and if n = number of atmospheres of initial pressure, then the water dis- charged, as determined by the usual formula, multiplied 1/836 = 29 multiplied byj/w, will give the discharge of air ; and if the discharge of steam is required the mul- tiplier will be |/1712 = 42| x yV. If, then, n should be 4 atmospheres total, including atmospheric pressure, the difference of head to be used in the determination of the water discharge would be 3 atmospheres, and water discharge X 42 x "|/4 = water- discharge x 84 = discharge of steam. In like manner, if the total pressure should be 9 atmospheres = 120 pounds indicated pressure, the dis- charge of steam would be = water discharge X 42 -j/9 = 126 times the water discharge under an equal head. And, in general, if w = the water discharge under any given head, length, and diameter of pipes, d = ratio of density of any elastic fluid, as compared with water and at the volume due to atmospheric tension, and n = number of atmospheres of initial pressure, then will the discharge, as compared with water, and ^ the volume due to atmospheric tension, be =* w X \/nd. TRANSMISSION OF POWER BY MEANS OF PIPES. Let A B represent a pipe of any given length, say one mile, and A C represent the pressure, say 60 pounds. The discharge of water at B, in cubic feet per second, is given by the formula : (i = .0762 i/T 6 1/| \\ *<7 "^ **& d = diameter in inches, H = head in feet, or the dififer^ ence in head when discharging against a lower pressure, ^ and L = length in feet. If A C =s 60 pounds, the head of water would be 60 x 2.31 = 138.6 feet, and_the discharge with a con- stant length would be as 1/H, or as "1/138.6, and the area of a triangle of which A B is the base and 1/T38.6 as the altitude, would be proportionate to the water discharge or A B x "1/138.6. Now suppose that the fluid discharging at B should be steam instead of water under 60 pounds indicated pressure, the actual pressure would be 75 pounds, the number of atmospheres 5. The initial density five times 1712 that of steam under atmospheric pressure, or = 342, and the head due to a pressure of 60 pounds = 138.6 X 342 = 47,401 feet. The discharge being proportioned to the square root of the head, would be as 1/138.6 X 342, or as -[/ 138.6 I/ 1Z1? and if A B as before = base of a triangle, and 47,401 = altitude, the discharges being as the square root of the altitude, will be as the area of a triangle whose base is A B and altitude = |/47401== -j/138.6 * -J/1712 -i/ 5 - The water discharges and steam discharges being as the areas of these triangles having the common base A B, 160 STREET RAILWAY MOTORS. will compare, as 1/138.6 is to 1/138.6 1/7712 -*- 1/5^ or if the water discharge be taken as unity, then as 1 is to 1/1712 -f- 1/^5. But this expression gives the discharge under initial density, and if the discharge is required at atmospheric tension, which is always desirable for the sake of uni- formity, the result must be multiplied by 5, and the ex- pression becomes 1/1712 x 5.-*- 1/5 = 1/1712 x 1/5, as previously stated, or generally as ~\/ n d. The head due to velocity has not been considered, as in questions relating to discharges through long pipes it is so insignificant as compared with the head due to fric- tion, that it may safely be neglected. It would not ex- ceed, generally, a small fraction of a pound ; but if great accuracy is desired the head, in feet, is readily deter- mined, and is in which v initial velocity, and the head divided by the number of feet at initial density required to make one pound, will give the pressure in pounds required for this velocity v, which is in addi- tion to friction. Suppose the length of the pipe should be increased, and draw a line from D to the end of the pipe, intersecting the line n B at P. The triangle D n P will be cut off, the perpendiculars of which will repre- sent the loss of head by friction, and the square root of the area, the discharge in cubic feet, and the same rule holds good if the length should be less than A B. Important Observation. Although almost self-evident yet, as very erroneous ideas seem to have been enter- tained in regard to the friction of pipes, it is necessary to state, emphatically, that in the discharge of fluids TRANSMISSION OF POWER BY MEANS OF PIPES. 161 through pipes whether the fluids be elastic or non- elastic the whole of the head, less that due to velocity, is absorbed by friction ; and where there is a free dis- charge there is no pressure whatever at the open end of the pipe. Referring again to the diagram, if A B is a pipe a mile long and discharges water, steam, or air freely at B under an initial pressure at A = 60 pounds, there will be no indicated pressure whatever at B unless the dis- charge be throttled, and the reduction of pressure from A to B will follow the line of the hypothenuse, and the pressure at any point will be represented by the perpen- dicular. If, for example, the initial pressure be repre- sented by A D, the pressure at B will be o, the total loss of pressure by friction in the distance A B will be 60 pounds. At any point P the pressure will be repre- sented by the perpendicular O P, and the loss of pres- sure by O m. But if the pipe is not discharging freely at B, the conditions will be very materially changed, and a large percentage of the fluid may be drawn off at intermediate points without affecting very seriously the pressure at B, due to the initial head if the pipe were closed. It has been asserted as the result of observation that at Detroit a mile of pipe 6 inches in diameter was laid, and notwithstanding the fact that a large number of consumers were using steam at intermediate points, the pressure at the boiler and at the end was precisely the same ; and the inference deduced therefrom was that steam can be carried almost any distance with a loss of power that is scarcely appreciable. This is a great mistake, and it would be a fatal error 11 162 STREET RAILWAY MOTORS. if works were planned and constructed with any such ideas. If the observed pressures at the two ends of the pipe at Detroit were the same, it resulted from two causes: First, a want of sensitiveness in the gauges, which often do not indicate within ten pounds of the correct pressure ; and second, the intermediate consumers were drawing off a small percentage of the capacity of the pipe. I will endeavor to elucidate this subject by a simple and practical illustration : Suppose a pipe be taken 6 inches diameter, one mile long, and 60 pounds initial pressure. The water dis- charge will be 1.1 cubic feet and the steam discharge = l.ll/1712xi/5 =102 cubic feet of steam per second. A horse-power for steam heating purposes has been taken as one cubic foot of water evaporated per hour, and one cubic foot of water =1712 cubic feet of steam. Therefore, 1712 H- 3600 =0.472 cubic feet per second = one horse-power. And 102-j-0.472=216 horse-power = maximum capa- city of 1 mile of 6-inch pipe under 60 pounds pressure. But suppose the end B of the pipe is closed, and at the point P = J of a mile from A, one-fourth of the whole capacity of the pipe is drawn off, how will the pressure at B be affected ? If discharging freely at B, the pressure at P, at J A B will be f of 60 pounds, or 45 pounds, and the loss of pressure will be represented by Om=15 pounds. But if the end B is closed, and the discharge at P is J capacity of pipe, then the velocity from A to P will be reduced to J, and the friction, which is as the square of the velocity to (J) 2 =tV, and the loss of head from TRANSMISSION OF POWER BY MEANS OF PIPES. 163 taking off 25 per cent, of the whole capacity of the pipe at P would be 15 x tV^rf f one P ounc l> an ^ the pres- sure at B would be 59 T ^ pounds as compared with an initial pressure of 60 pounds. If one-half the whole capacity of the pipe should be drawn off at the middle point, or if there should be an equivalent thereto discharged the reduction of pressure at the extreme end, instead of being 30 pounds, or one- half, would be ^ x(J) 2 = 7J pounds, and the pressure remaining would be 52 J pounds. These results, deduced from purely theoretical con- siderations, seem to be entirely consistent and reasonable ; but it is important to test them by actual and careful experiments. The experiments of Mr. Holly and Mr. Gaskill at Lockport were made under circumstances peculiarly favorable to accuracy. A large engine cylinder was used as a meter ; the contents, including clearance, were 8.64 cubic feet ; the number of cylinders discharged per minute, 66 ; cubic feet per minute, 570 ; distance from boiler equivalent to 168 feet of 2-inch pipe in frictional resistance; boiler pressure, 50 pounds; cylinder pressure, 30 pounds ; loss by friction, 20 pounds. From these data let us determine the friction in one mile of 6-inch pipe under a head or pressure of 60 pounds. If Mr. Holly gets a discharge of 570 cubic feet per minute in a pipe 2 inches diameter and 168 feet long, the discharge per second will be 570 -+- 60 =9.5, under total initial pressure of 50 + 15=65 pounds; as the discharge is in proportion to the square root of the length, the discharge in one mile = 9.5 X T/F2 6 A = 1-78 cubic feet. 164 STREET RAILWAY MOTORS. If the discharge is 1.78 cubic feet in a 2-inch pipe, the discharge being as the square root of the fifth power of the diameter, it will be in a 6-inch pipe 1.78 X 15.6 = 27.76. If the discharge be 27.76, under 30 pounds, and under initial pressure of 50 pounds, the discharge at atmospheric tension under initial pressure of 60 pounds, would be 27.46 x ^x 1/f = 91.6 cubic feet per second, as deduced from experiment of Messrs. Holly and Gaskill through a pipe obstructed by several bends. We will now examine what should have been the dis- charge through a pipe one mile long, six inches diameter, under 60 pounds head, as deduced from the theoretical law heretofore enunciated. The water discharge is 1.1 cubic feet per second, and 1.1 X 1712x 1/^=102, the theoretical discharge, and. the difference, 10.6, is fully explained by the eight bends in the pipe through which the steam was trans- mitted in the experiment. This result, giving a greater theoretical than actual discharge, is the more gratifying because it has generally been believed that theory was unreliable, and that the actual results as deduced from observation and experi- ment were far in excess of the capacity and pressure as given by the books. This is true, because in stating a rule the books did not always state the conditions under which it was ap- plicable, as, for example, the rule that the discharge of air is equal to 30J times the discharge of water under like conditions, is true only at one initial pressure, and that a very low one, while under high pressures the TRANSMISSION OF POWER BY MEANS OF PIPES. 165 error from its application may be several hundred per cent. If theory is not sustained by observation and experi- ment, it only proves that the theory is defective, and that the true law has not been discovered ; but that there are natural laws is unquevStionable, and these laws, as applicable to pneumatics, are as immutable as those of gravity. Practical men, proceeding without a knowledge of these laws, are like mariners at sea without chart or compass. I propose to show that the law of discharge that has been here given is further verified by the careful and elaborate experiments made at the Mt. Cenis tunnel. FRICTION OF AIR IN PIPES AS DETERMINED FROM THE EXPERIMENTS AT THE MT. CENIS TUNNEL. The scientific commission, appointed to conduct these experiments, reported the following table as a condensa- tion of their results : Loss of Tension per 1000 metres of Pipe, expressed in Millimetres of a Column of Mercury. Velocity of air at the en- Diameter of pipes in the clear, in decimals of a m'etre. trance of the pipe, in metres, per second. 0.10 0.15 0.20 0.25 0.30 0.35 1 6 4 3 3 2 2. 2 26 18 13 11 ! 9 8 3 62 42 31 25 21 18 4 108 72 54 44 36 31 5 167 112 84 67 56 48 6 233 156 117 94 78 67 166 STREET RAILWAY MOTORS. An inspection verifies these laws : 1. Friction inversely as diameters. 2. Friction directly as squares of velocities. To which may be added two other la\vs : 3. Friction directly as the length. 4. Friction directly as the density. In comparison with other results the friction of 1 mile of 6-inch pipe with initial velocity, 20 feet will be de- duced from this table. Assume any number, say a pipe 0.2 of a metre diam- eter and 5 metres velocity, the loss in millimetres of mercury is 84.2 of a metre = 7.874 inches ; 5 metres per second= 16.4 feet; 1000 metres =3281 feet; 1 milli- metre =0.03937 inches. 7.874 20 2 .03937 5280 _, Then 84 x -- x x x - 5.1 pounds, as the resistance of air, and for steam 2.5 pounds per mile, assuming loss of tension to be in proportion to density. We will now apply the law as deduced from the hy- draulic discharge : The discharge of water under a head of 60 pounds, length 1 mile and diameter 6 inches, is 1.1 cubic feet per second. Air is 836 times lighter than water. 60 pounds 5^55 atmospheres; 1.1 X j/836x 1/5 = 67.87 cu _ bic feet per second, and at initial density =67. 87 -*-5 = 13.57 cubic feet, and initial velocity 68 feet per sec- ond, nearly. Now, if the loss of tension with initial velocity of 68 feet be 60 pounds, the loss with velocity of 20 feet will 20 2 be 60 X = 5.1 pounds. TRANSMISSION OF POWER BY MEANS OF PIPES. 167 This is precisely the loss of tension in one mile of 6-iuch pipe discharging air under an initial velocity of 20 feet per second, as deduced from the experiments of the Mt. Cenis Tunnel Commissioners. The law of discharge, above stated, seems to be com- pletely verified and established, both by the experiments in Europe and those made by Mr. Holly, at Lockport, with the engine metre, and I think can be safely relied upon as a basis of calculation of capacity of mains and losses by friction in transmission. The following table will be convenient, giving the discharge of steam at the volume of atmospheric tension, the corresponding water discharge under same head, diameter and length being taken as unity, and pressures varying by half atmospheres from 1 to 10 : Volume of Discharge. .... 41.4 .... 50.7 .... 58.6 .... 65.5 .... 71,7 .... 77.3 .... 82.8 .... 88.2 .... 92.5 .... 97.3 .... 101.4 .... 105.9 .... 109.6 .... 113.2 .... 117.0 .... 120.5 .... 124.1 .... 127.7 130.8 Pressure in Initial Atmospheres. Densities. 1 ... . . 1712 IT . . 1141 2 ... . . 856 2* ... . . 685 3 ... 571 31 ... . . 489 4 ... . . 428 41 ... . . 381 5 ... 342 5* . . . . . 311 6 ... . . 285 6^ ... . . 263 7 ... . . 245 7^ ... . . 228 8 ... . . 214 8J . . 201 9 ... . . 190 9* ... . . 180 10 . . . . . 171 168 STREET RAILWAY MOTORS. TABLE OF THOMAS Box. In the valuable work on heat by Thomas Box, is given a table for the friction of air, steam, and gas in long pipes. The difference in density is not recognized in this table, but it was probably intended for air, as this fluid was more particularly under discussion. Under this hypothesis, the results will be compared with our assumed standard of velocity, 20 feet, length one mile, diameter six inches. The table gives the head to overcome friction with velocity of 10 cubic feet per minute through a two-inch pipe for a distance of one yard =0.000162 pound. Area of 2-inch pipe = 3.1416 and 10 X^^^O.77 = velocity in feet per second. 0.000162 x 1760 = 0.285120 = friction per mile in 2-inch pipe. 0.285120 X f = 0.09504= pounds per mile friction in 6-inch pipe, velocity 0.77. 20 2 0.09504 X ^ = 6.3 = friction of air in a 6-inch pipe for a distance of one mile and velocity 20 feet per second. The friction of steam at atmospheric density should by the same rule be 3.15 pounds, which is in excess of the results deduced from formula, from the Mt. Cenis experiments, and from other experiments. FORMULA OF WEISBACH. Weisbach gives the following formula for the friction of air through long pipes : /= 0.0256 x ^ X ~ in which TRANSMISSION OF POWER BY MEANS OF PIPES. 169 I = length in feet ; d = diameter in feet ; v = velocity in feet per second ; /= height of a column of air equal to the resistance by friction. To test this formula, assume length = 1 mile, diam- eter 6 inches or 0.5 of a foot, and v = 20 feet. Then friction of one mile represented by a column of air equals 0.0256 x | x fj= 1700 feet. But 1 700 feet of air, if at atmospheric tension, would be equivalent to about two feet of water, weighing less than one pound, while from other data, both theoretical and experimental, it is known that the friction is five pounds. If the initial, instead of the terminal, density is intended to be used, the difficulty is that there is no way given for the determination of this density, and the formula, even if correct, is practically useless. So also the rule of the engineer's pocket-books, that the discharge of air is 30| times the discharge of water under like conditions, is entirely fallacious. It can be true only at one pressure, and that a very low one, and it fails to recognize the varying densities of different elastic fluids tinder varying pressures, without which no rule can be reliable. PIPES OF EQUIVALENT RESISTANCES. When a line of pipe consists of portions whose diame- ters are not uniform, it is necessary to make a correction by substituting the length of pipe of uniform diameter that would give an equivalent resistance. 170 STREET RAILWAY MOTORS. It has been stated that where quantity is constant and diameter variable the friction is inversely as the fifth power of the diameter. If the friction in one mile or one unit of length of one-inch pipe be taken as unity, the number of miles of pipe of any other diameter will be given by the follow- ing table, giving equal resistance : 1 inch pipe 1* " 2 " 2| " 3 4 " 5 6 7 " 8 9 10 11 " 12 " 1. 7.5 32. 97.65 243. . 1024. . 3125. . 7776. . 16807. . 32768. . 59049. . 100000. . 161051. . 248832. FORMULA FOR CALCULATING TABLES OF Loss HEAD. BY FRICTION. OF It has been seen that in the transmission of steam through a pipe six inches in diameter and one mile long the loss by friction was 2.5 pounds, with an initial velocity of 20 feet per second. For any other length we have these laws : 1. The friction is as the length. 2. The friction is inversely as the diameter. 3. The friction is as the square of the velocity. 4. The friction with different fluids is as the density. TRANSMISSION OF POWER BY MEANS OF PIPES. ] 71 As a basis of calculation, it will be convenient to determine the friction of steam in 1 mile of 1-inch pipe, with an initial velocity of one foot per second. The friction in one mile of 6-inch pipe, and initial velocity 20, being 2.5 pounds with steam, the friction in a pipe 1 inch in diameter will be 2.5 X 6 = 15 pounds under the same velocity ; and the friction with a velocity of 20 feet per second being 15 pounds, the friction with a velocity of one foot per second will be 15 x - 2 = 0.0375. 2\) For any other diameter or velocity the expression becomes : Friction per mile 0.0375 x V - The initial velocity must be determined from the dis- charge, and the terminal discharge, as previously stated, is = water discharge X %/1712x \/n, in which n =* the atmospheres of pressure. This discharge divided by n gives discharge at initial density, and the discharge at initial density in cubic feet divided by the area in square feet will be initial velocity. 172 STREET RAILWAY MOTORS. 1 fc II ^H r3 OC FAIRBAIRN. The Principles of Mechanism and Machinery of Transmission Comprising the Principles of Mechanism, Wheels, and Pullevs, Strength and Proportions of Shafts, Coupling of Shafts, and Engag- ing and Disengaging Gear. By SIR WILLIAM FAIRBAIRN, Bait C. E. Beautifully Illustrated by over 150 wood-cuts. In one volume. I2mo #2.50 FLEMING. Narrow Gauge Railways in America. A Sketch of their Rise, Progress, and Success. Valuable Statistics as to Grades, Curves, Weight of Rail, Locomotives, Cars, etc. By HOWARD FLEMING. Illustrated, 8vo $1 oo FORSYTH. Book of Designs for Headstones, Mural, and other Monuments: Containing 78 Designs. By JAMES FORSYTH. With an Introduction Vy CHARLES BOUTELL, M. A. 4 to., cloth . . - $5 w HENRY CAREY BAIRD & CO.'S CATALOGUE. FRANKEL HUTTER. A Practical Treatise on the Manu- facture of Starch, Glucose, Starch-Sugar, and Dextrine: Based on the German of LADISLAUS VON WAGNER, Professor in the Royal Technical High School, Buda-Pest, Hungary, and other authorities. By JULIUS FRANKEL, .Graduate of the Polytechnic School of Hanover. Edited by ROBERT HUTTER, Chemist, Practical Manufacturer of Starch-Sugar. Illustrated by 58 engravings, cover- ing every branch of the subject, including examples of the most Recent and Best American Machinery. 8vo., 344 pp. . $3 .50 GARDNER. The Painter's Encyclopaedia: Containing Definitions of all Important Words in the Art of Plain and Artistic Painting, with Details of Practice in Coach, Carriage, Railway Car, House, Sign, and Ornamental Painting, including Graining, Marbling, Staining, Varnishing, Polishing, Lettering, Stenciling, Gilding, Bronzing, etc. By FRANKLIN B. GARDNER. 158 Illustrations. I2ino. 427 pp $2.00 GARDNER. Everybody's Paint Book: A Complete Guide to the Art of Outdoor and Indoor Painting, De- signed for the Special Use of those who wish to do their own work, and consisting of Practical Lessons in Plain Painting, Varnishing, Polishing, Staining, P?prr Hanging, Kalsomining, etc., as well as Directions for Renovating Furniture, and Hints on Artistic Work for Home Decoration. 38 Illustrations. I2mo., 183 pp. . $1.00 GEE. The Goldsmith's Handbook : Containing full instructions for the Alloying and Working of Gold, including the Art of Alloying, Melting, Reducing, Coloring, Col- lecting, and Refining; the Processes of Manipulation, Recovery of Waste; Chemical and Physical Properties of Gold; with a New System of Mixing its Alloys ; Solders, Enamels, and other Useful Rules and Recipes. By GEORGE E. GEE. I2mo. . . $1*7$ GEE. The Silversmith's Handbook : Containing full instructions for the Alloying and Working of Silver, including the different modes of Refining and Melting the Metal ; its Solders ; the Preparation of Imitation Alloys ; Methods of Manipula- tion ; Prevention of Waste ; Instructions for Improving and Finishing the Surface of the Work ; together with other Useful Information and Memoranda. By GEORGE E. GEE. Illustrated. I2mo. $1-75 GOTHIC ALBUM FOR CABINET-MAKERS: Designs for Gothic Furniture. Twenty-three plates. Oblong $2.OO GRANT. A Handbook on the Teeth of Gears : Their Curves, Properties, and Practical Construction. By GEORGE B. GRANT. Illustrated. Third Edition, enlarged. 8vo. $1.00 GREENWOOD. Steel and Iron: Comprising the Practice and Theory of the Several Methods Pur- sued in their Manufacture, and of their Treatment in the Rolling- Mills, the Forge, and the Foundry. By WILLIAM HENRY GREEN- WOOD, F. C. S. With 97 Diagrams, 536 pages. 12010. $2.00 14 HENRY CAREY BAIRD & CO.'S CATALOGUE. GREGORY. Mathematics for Practical Men : Adapted to the Pursuits of Surveyors, Architects, Mechanics, and Civil Engineers. By OLINTHUS GREGORY. 8vo., plates $3.00 GRISWOLD. Railroad Engineer's Pocket Companion for UK Field: Comprising Rules for Calculating Deflection Distances and Angles, Tangential Distances and Angles, and all Necessary Tables for En gineers; also the Art of Levelling from Preliminary Survey to the Construction of Railroads, intended Expressly for the Young En- gineer, together with Numerous Valuable Rules and Examples. By W. GRISWOLD. i2mo., tucks * $*-75 GRUNER. Studies of Blast Furnace Phenomena: By M. L. GRUNER, President of the General Council of Mines o! France, and lately Professor of Metallurgy at the Ecole des Mines. Translated, with the author's sanction, with an Appendix, by L. D. B. GORDON, F. R. S. E., F. G. S. 8vo. . . . $2.50 Hand-Book of Useful Tables for the Lumberman, Farmer and Mechanic : Containing Accurate Tables of Logs Reduced to Inch Board Meas* ure, Plank, Scantling and Timber Measure; Wages and Rent, by Week or Month ; Capacity of Granaries, Bins and Cisterns ; Land Measure, Interest Tables, with Directions for Finding the Interest on any sum at 4, 5, 6, 7 and 8 per cent., and many other Useful Tables. 32 mo., boards. 186 pages .25 HASERICK. The Secrets of the Art of Dyeing Wool, Cotton, and Linen, Including Bleaching and Coloring Wool and Cotton Hosiery and Random Yarns. A Treatise based on Economy and Practice. By E. C. HASERICK. Illustrated by 323 Dyed Patterns of the Yarn* or Fabrics. 8vo $7-5o HATS AND FELTING: A Practical Treatise on their Manufacture. By a Practical Hatter. Illustrated by Drawings of Machinery, etc. 8vo. . . #1.25 HOFFER. A Practical Treatise on Caoutchouc and Gutta Percha, Comprising the Properties of the Raw Materials, and the manner or" Mixing and Working them ; with the Fabrication of Vulcanized and Hard Rubbers, Caoutchouc and Gutta Pescha Compositions, Water* proof Substances, Elastic Tissues, the Utilization of Waste, etc., etc, From the German of RAIMUND HFFER. By W. T. BRANNT. Illustrated I2mo $2.50 HAUPT. Street Railway Motors: With Descriptions and Cost of Plants and Operation of the Various Systems now in Use. I2mo. , .... $1-75 HENRY CAREY BAIRD & CO.'S CATALOGUE. 15 HAUPT RHAWN. A Move for Better Roads : Essays on Road-making and Maintenance and Road Laws, for which Prizes or Honorable Mention were Awarded through the University of Pennsylvania by a Committee of Citizens of Philadel- phia, with a Synopsis of other Contributions and a Review by the Secretary, LEWIS M. HAUPT, A. M., C. E. ; also an Introduction by WILLIAM H. RHAWN, Chairman of the Committee. 319 pages. 8vo. $2.00 HUGHES. American Miller and Millwright's Assistant: By WILLIAM CARTER HUGHES. i2mo $1.50 HULME. Worked Examination Questions in Plane Geomet- rical Drawing : For the Use of Candidates for the Royal Military Academy, Wool- wich ; the Royal Military College, Sandhurst ; the Indian Civil En- gineering College, Cooper's Hill ; Indian Public Works and Tele- graph Departments ; Royal Marine Light Infantry ; the Oxford and Cambridge Local Examinations, etc. By F. EDWARD HULME, F. L. S., F. S. A., Art-Master Marlborough College. Illustrated by 300 examples. Small quarto $2.50 JERVIS. Railroad Property: A Treatise on the Construction and Management of Railways; designed to afford useful knowledge, in the popular style, to the holders of this class of property ; as well as Railway Manage*, Offi- cers, ar.d Agents. By JOHN B. JERVIS, late Civil Engineer of the Hudson River Railroad, Croton Aqueduct, etc. i2mo., cloth $2.oc KEENE. A Hand-Book of Practical Gauging: For the Use of Beginners, to which is added a Chapter on Distilla- tion, describing the process in operation at the Custom-House for ascertaining the Strength of Wines. By JAMES B. KEENE, of H. M. Customs. 8vo. $1^25 KELLEY. Speeches, Addresses, and Letters on Industrial and Financial Questions : By HON. WILLIAM D. KELLEY, M. C. 544 pages, 8vo. . $2.50 KELLOGG. A New Monetary System : The only means of Securing the respective Rights of Labor and Property, and of Protecting the Public from Financial Revulsions, By EDWARD KELLOGG. Revised from his work on "Labor and other Capital." With numerous additions from his mnnuscript. Edited by MARY KELLOGG PUTNAM. Fifth edition. To which in added a Biographical Sketch of the Author. One rolume, izmo. Paper cover $l.oo Bound in cloth 1.50 KEMLO. Watch-Repairer's Hand-Book : Being a Complete Guide to the Young Beginner, in Taking Apart, Putting Together, and Thoroughly Cleaning the English Lever and other Foreign Watches, and all American Watches. By F. KEMLO, Practical Watchmaker. With Illustrations. I2tno. . $1.25 16 HENRY CAREY BAIRD & CO.'S CATALOGUE. XENTISH. A Treatise on a Box of Instruments, And the Slide Rule ; with the Theory of Trigonometry and Log* rithms, including Practical Geometry, Surveying, Measuring of Tim- ber, Cask and Malt Gauging, Heights, and Distances. By THOMAJ KENTISH. In one volume. I2mo. .... $1.2 KERL. The Assayer's Manual: An Abridged Treatise on the Docimastic Examination of Ores, and Furnace and other Artificial Products. By BRUNO KERL, Professor in the Royal School of Mines. Translated from the German by WILLIAM T. BRANNT. Second American edition, edited with Ex- tensive Additions by F. LYNWOOD GARRISON, Member of the American Institute of Mining Engineers, etc. Illustrated by 87 en- gravings. 8vo #3-OO KICK. Flour Manufacture . A Treatise on Milling Science and Practice. By FREDERICK KICK, Imperial Regierungsrath, Professor of Mechanical Technology in the Imperial German Polytechnic Institute, Prague. Translated from the second enlarged and revised edition with supplement by H. H. P. POWLES, Assoc. Memb. Institution of Civil Engineers. Illustrated with 28 Platens, and 167 Wood-cuts. 367 pages. 8vo. . $10.00 KINGZETT. The History, Products, and Processes of the Alkali Trade : Including the most Recent Improvements. By CHARLES THOMAS KINGZETT, Consulting Chemist. With 23 illustrations. 8vo. $2.50 KIRK. The Founding of Metals : A Practical Treatise on the Melting of Iron, with a Description of the Founding of Alloys ; also, of all the Metals and Mineral Substancei used in the Art of Founding. Collected from original sources. B> EDWARD KIRK, Practical Foundryman and Chemist. Illustrated. Third edition. 8vo. $2.50 LANDRIN. A Treatise on Steel : Comprising its Theory, Metallurgy, Properties, Practical Working, and Use. By M. H. C. LANDRIN, JR., Civil Engineer. Translated from the French, with Notes, by A. A. FESQUET, Chemist and En gineer. With an Appendix on the Bessemer and the Martin Pro- cesses for Manufacturing Steel, from the Report of Abram S. Hawitt, United States Commissioner to the Universal Exposition, Paris, 1867] I2mo fo- 00 LANGBEIN. A Complete Treatise on the Electro-Deposition of Metals : Translated from the German, with Additions, by WM. T. BRANNT. 125 illustrations. 8vo $4.00 LARD NER. The Steam-Engine : For the Use of Beginners. Illustrated. I2rno. ... 75 LEHNER. The Manufacture of Ink: Comprising the Raw Materials, and the Preparation of Writing, Copying and Hektograph Inks, Safety Inks, Ink Extracts and Pow- ders, etc. Translated from the German of SlGMUND LEHNER, with additions by WILLIAM T. BRANNT. Illustrated. I2mo. $2.00 HENRY CAREY BAIRD & CO.'S CATALOGUE. 17 LARKIN. The Practical Brass and Iron Founder's Guide: A Concise Treatise on Brass Founding, Moulding, the Metals and their Alloys, etc. ; to which are added Recent Improvements in the Manufacture of Iron, Steel by the Bessemer Process, etc., etc. Bf JAMES LARKIN, late Conductor of the Brass Foundry Department U Reany, Neafie & Co.'s Penn Works, Philadelphia. New edition, revised, with extensive additions. I2mo. . . . #2.50 LEROUX. A Practical Treatise on the Manufacture of Worsteds and Carded Yarns : Comprising Practical Mechanics, with Rules and Calculations applied to Spinning; Sorting, Cleaning, and Scouring Wools; the English and French Methods of Combing, Drawing, and Spinning Worsteds, and Manufacturing Carded Yarns. Translated from the French of CHARLES LEROUX, Mechanical Engineer and Superintendent of a Spinning-Mill, by HORATIO PAINE, M. D., and A. A. FESQUET, Chemist and Engineer. Illustrated by twelve large Plates. To which is added an Appendix, containing Extracts from the Reports of the International Jury, and of the Artisans selected by the Commtttes appointed by the Council of the Society of Arts, London, on Woolen and Worsted Machinery and Fabrics, as exhibited in the Paris Uni- versal Exposition, 1867. 8vo. $5.00 LEFFEL. The Construction of Mill-Dams : Comprising also the Building of Race and Reservoir Embankments and Head-Gates, the Measurement of Streams, Gauging of Water Supply, etc. By JAMES LEFFEL & Co. Illustrated by 58 engravings. 8vo. $2.50 LESLIE. Complete Cookery: Directions for Cookery in its Various Branches. By Miss LESLIE. Sixtieth thomsand. Thoroughly revised, with the addition of New Receipts. I2mo 1.50 LE VAN. The Steam Engine and the Indicator : Their Origin and Progressive Development; including the Most Recent Examples of Steam and Gas Motors, together with the Indi- cator, its Principles, its Utility, and its Application. By WILLIAM BARNET LE VAN. Illustrated by 205 Engravings, chiefly of Indi- cator-Cards. 469 pp. 8vo $4-o LIEBER. Assayer's Guide : Or, Practical Directions to Assayers, Miners, and Smelters, for the Tests and Assays, by Heat and by Wet Processes, for the Ores of all the principal Metals, of Gold and Silver Coins and Alloys, and of Coal, etc. By OSCAR M. LIEBER. Revised. 283 pp. I2mo. $1.50 JLockwood's Dictionary of Terms : Used in the Practice of Mechanical Engineering, embracing those Current in the Drawing Office, Pattern Shop, Foundry, Fitting, Turn- ing, Smith's and Boiler Shops, etc., etc., comprising upwards of Six' Thousand Definitions. Edited by a Foreman Pattern Maker, author f " Pattern Making." 417 pp. I2tno. . . ^ Ifl.oo i8 HENRY CAREY BAIRD & CO.'S CATALOGUE. LUKIN. Amongst Machines ; Embracing Descriptions of the various Mechanical Appliances used in the Manufacture of Wood, Metal, and other Substances. I2mo. JM-75 LUKIN. The Boy Engineers : What They Did, and How They Did It. With 30 plates. l8mo. #1-75 LUKIN. The Young Mechanic t Practical Carpentry. Containing Directions for the Use of all kinds t>f Tools, and for Construction of Steam- Engines and Mechanical Models, including the Art of Turning in Wood and Metal. By JOHN LUKIN, Author of "The Lathe and Its Uses," etc. Illustrated. I2mo $1-75 MAIN and BROWN. Questions on Subjects Connected with the Marine Steam-Engine : And Examination Papers; with Hints for their Solution. By THOMAS J. MAIN, Professor of Mathematics, Royal ""tfaval College, and THOMAS BROWN, Chief Engineer, R. N. I2mo., cloth . #1.00 MAIN and BROWN. The Indicator and Dynamometer: With their Practical Applications to the Steam-Engine. By THOMAS J. MAIN, M. A. F. R., Ass't S. Professor Royal Naval College, Portsmouth, and THOMAS BROWN, Assoc. Inst. C. E., Chief Engineer R. N., attached to the R. N. College. Illustrated. 8vo. . #I.OO MAIN and BROWN. The Marine Steam-Engine. By THOMAS J. MAIN, F. R. Ass't S. Mathematical Professor at the Royal Naval College, Portsmouth, and THOMAS BROWN, Assoc. Inst. C. E., Chief Engineer R. N. Attached to the Royal Naval College. With numerous illustrations. 8vo. MAKINS. A Manual of Metallurgy: By GEORGE HOGARTH MAKINS. 100 engravings. Second edition rewritten and much enlarged. I2mo., 592 pages . . $3-oo MARTIN. Screw-Cutting Tables, for the Use of Mechanica) Engineers : Showing the Proper Arrangement of Wheels for Cutting the Threads of Screws of any Required Pitch ; with a Table for Making the Uni- versal Gas-Pipe Thread and Taps. By W. A. MARTIN, Engineer. 8vo. 50 MICHELL. Mine Drainage: Being a Complete and Practical Treatise on Direct-Acting Under* ground Steam Pumping Machinery. With a Description of a larg nuuaber of the best known Engines, their General Utility and ih Special Sphere of their Action, the Mode of their Application, and their Merits compared with other Pumping Machinery. By STEPHEN MICHELL. Illustrated by 137 engravings. 8vo., 277 pages . $6.00 MOLESWORTH. Pocket-Book of Useful Formulae and Memoranda for Civil and Mechanical Engineers. By GUILFORD L. MOLESWORTH, Member of the Institution of Civil Engineers, Chief Resident Engineer of the Ceylon Railway. Full- bound in Pocket-book form . . . J>I.Ol HENRY CAREY BAIRD & CO.-ff CATALOGUE. 19 MOORE. The Universal Assistant and the Complete Me- chanic : Containing over one million Industrial Facts, Calculations, Receipts, Processes, Trades Secrets, Rules, Business Forms, Legal Items, Etc., in every occupation, from the Household to the Manufactory. By R. MOORE. Illustrated by 500 Engravings. I2mo. . $2.50 MORRIS. Easy Rules for the Measurement of Earthworks : By means of the Prismoidal Formula. Illustrated with Numerom Wood- Cuts, Problems, and Examples, and concluded by an Exten- sive Table for finding the Solidity in cubic yards from Mean Areas. The whole being adapted for convenient use by Engineers, Surveyors, Contractors, and others needing Correct Measurements of Earthwork. By ELWOOD MORRIS, C. E. 8vo $1.50 MAUCHLINE. The Mine Foreman's Hand-Book: Of Practical and Theoretical Information on the Opening, Ventilat- ing, and Working of Collieries. Questions and Answers on Practi- cal and Theoretical Coal Mining. Designed to Assist Students and others in Passing Examinations for Mine Foremanships. A New, Revised and Enlarged Edition. 114 illustrations. 8vo. $3-73 NAPIER. A System of Chemistry Applied to Dyeing. By JAMES NAPIER, F. C. S. A New and Thoroughly Revised Edi- tion. Completely brought up to the present state of the Science, including the Chemistry of Coal Tar Colors, by A. A. FESQUET, Chemist and Engineer. With an Appendix on Dyeing and Calica Printing, as shown at the Universal Exposition, Paris, 1867. Illus- trated. 8vo. 422 pages $3-5 NEVILLE. Hydraulic Tables, Coefficients, and Formulae, for finding the Discharge of Water from Orifices, Notches, Weirs, Pipes, and Rivers : Third Edition, with Additions, consisting of New Formulas for the Discharge from Tidal and Flood Sluices and Siphons ; general infor- mation on Rainfall, Catchment-Basins, Drainage, Sewerage, Water Supply for Towns and Mill Power. By TOHN NEVILLE, C. E. M R I. A. ; Fellow of the Royal Geological Society of Ireland. Thick I2ino 15-50 NEWBERY. Gleanings from Ornamental Art of every style ; Drawn from Examples in the British, South Kensington, Indian, Crystal Palace, and other Museums, the Exhibitions of 1851 and 1862, and the best English and Foreign works. In a series of loo exquisitely drawn Plates, containing many hundred examples. By ROBERT NEWBERY. 410. $12.53 NICHOLLS. The Theoretical and Practical Boiler-Maker and Engineer's Reference Book: Containing a variety of Useful Information for Employers of Labor. Foremen and Working Boiler-Makers, Iron, Copper, and Tinsmith* 20 HENRY CAREY BAIRD & CO.'S CATALOGUE. Ikaughismen, Engineers, the General Steam-using Public, and for tho Use of Science Schools and Classes. By SAMUEL NICHOLLS. Illus- trated by sixteen plates, I2mo. ..... $2.50 NICHOLSON. A Manual of the Art of Bookbinding : Containing full instructions in the different Branches of Forwarding, Gilding, and Finishing. Also, the Art of Marbling Book-edges and Paper. By JAMES B. NICHOLSON. Illustrated. I2mo., cloth $2.2$ NICOLLS. The Railway Builder: A Hand-Book for Estimating the Probable Cost of American Rail* way Construction and Equipment. By WILLIAM J. NICOLLS, Civil Engineer. Illustrated, full bound, pocket-book form . $2.00 NORMANDY. The Commercial Handbook of Chemical An- alysis : , Or Practical Instructions for the Determination of the Intrinsic ot Commercial Value of Substances used in Manufactures, in Trades, and in the Arts. By A. NORMANDY. New Edition, Enlarged, and to a great extent rewritten. By HENRY M. NOAD, Ph.D., F.R.S., thick I2mo $5.00 NORRIS. A Handbook for Locomotive Engineers and Ma- chinists : Comprising the Proportions and Calculations for Constructing Loco- motives; Manner of Setting Valves; Tables of Squares, Cubes, Areas, etc., etc. By SEPTIMUS NORRIS, M. E. New edition. Illustrated, I2mo |i.50 NYSTROM. A New Treatise on Elements of Mechanics : Establishing Strict Precision in the Meaning of Dynamical Terms : accompanied with an Appendix on Duodenal Arithmetic and Me- trology. By JOHN W. NYSTROM, C. E. Illustrated. 8vo. $2.00 NYSTROM. On Technological Education and the Construc- tion of Ships and Screw Propellers : For Naval and Marine Engineers. By JOHN W. NYSTROM, late Acting Chief Engineer, U. S. N. Second edition, revised, with addi- tional matter. Illustrated by seven engravings. I2mo. . $1.50 O'NEILL. A Dictionary of Dyeing and Calico Printing: Containing a brief account of all the Substances and Processes in use in the Art of Dyeing and Printing Textile Fabrics ; with Practical Receipts and Scientific Information. By CHARLES O'NEILL, Analy- tical Chemist. To which is added an Essay on Coal Tar Colors and their application to Dyeing and Calico Printing. By A. A. FESQUET, Chemist and Engineer. With an appendix on Dyeing and Calico Printing, as shown at the Universal Exposition, Paris, 1867- 8vo., 491 pages |3.50 ORTON. Underground Treasures'. How and Where to Find Them. A Key for the Ready Determination of all the Useful Minerals within the United States. By JAMES ORTON, A.M., Late Professor of Natural History in Vassar College^ /J. Y.; Cor. Mem. of the Academy of Natural Sciences, Philadelphia, and of the Lyceum of Natural History, New York ; author of the " Andes and the Amazon," etc. A New Edition, with Additions. Illustrated * -^ HENRY CAREY BAiRD & CO.'S CATALOGUE. 21 OSBORN. The Prospector's Field Book and Guide: In the Search for and the Easy Determination of Ores and Other Useful Minerals. By Prof. H. S. OSBORN, LL. D., Author of "The Metallurgy of Iron and Steel;" "A Practical Manual of Minerals, Mines, and Mining." Illustrated by 44 Engravings. I2mo $1.50 OSBORN. A Practical Manual of Minerals, Mines and Min- ing: Comprising the Physical Properties, Geologic Positions, Local Occur- rence and Associations of the Useful Minerals; their Methods of Chemical Analysis and Assay : together with Various Systems of Excavating and Timbering, Brick and Masonry Work, during Driv- ing, Lining, Bracing and other Operations, etc. By Prof. H. S. OSBORN, LL. D., Author of the " Metallurgy of Iron and Steel." Illustrated by 171 engravings from original drawings. 8vo. $4.50 OVERMAN. Thti Manufacture of Steel : Containing the Practice and Principles of Working and Making Steel. A Handbook for Blacksmiths and Workers in Steel and Iron, Wagon Makers, Die Sinkers, Cutlers, and Manufacturers of Files and Hard- ware, of Steel and Iron, and for Men of Science and Art. By FREDERICK OVERMAN, Mining Engineer, Author of the " Manu- facture of lion," etc. A new, enlarged, and revised Edition. By A. A. FESQUET, Chemist and Engineer. I2mo. . . $1.50 OVERMAN. The Moulder's and Founder's Pocket Guide : A Treatise or* Moulding and Founding in Green-sand, Dry-sand, Loam, and Cement; the Moulding of Machine Frames, Mill-gear, Hollow* ware, Ornaments, Trinkets, Bells, and Statues ; Description of Moulds for Iron, Bronze, Brass, and other Metals ; Plaster of Paris, Sulphur, Wax, etc. ; the Construction of Melting Furnaces, the Melting and Founding of Metals ; the Composition of Alloys and their Nature, etc., etc. By FREDERICK OVERMAN, M. E. A new Edition, to which is added a Supplement on Statuary and Ornamental Moulding, Ordnance, Malleable Iron Castings, etc. By A. A. FESQUET, Chem- ist and Engineer. Illustrated by 44 engravings. I2mo. . $2.OQ PAINTER, GILDER, AND VARNISHER'S COMPANIONS Containing Rules and Regulations in everything relating to the AriS of Painting, Gilding, Varnishing, Glass-Staining, Graining, Marbling, Sign- Writing, Gilding on Glass, and Coach Painting and Varnishing; Tests for the Detection of Adulterations in Oils, Colors, etc. ; and a Statement of the Diseases to which Painters are peculiarly liable, with the Simplest and Best Remedies. Sixteenth Edition. Revised, with an Appendix. Containing Colors and Coloring Theoretical and Practical. Comprising descriptions of a great variety of Additional Pigments, their Qualities and Uses, to which are added, Dryers, and Modes and Operations of Painting, etc. Together with ChevreuFs Principles of Harmony and Contrast of Colors. I2mo. Cloth $1.50 5PALLETT. The Miller's, Millwright's, and Engineer's Guide. : By HKNRY PALLETT. Illustrated. I2mo. . . $2.00 22 HENRY CAREY BAIRD & CO.'S CATALOGUE. PERCY. The Manufacture of Russian Sheet-Iron. By JOHN PERCY, M. D., F. R. S., Lecturer on Metallurgy at tht Royal School of Mines, and to The Advance Class of Artillery Officers at the Royal Artillery Institution, Woolwich; Author of " Metallurgy." With Illustrations. 8vo., paper . . 50 cts. PERKINS. Gas and Ventilation : Practical Treatise on Gas and Ventilation. With Special Relation to Illuminating, Heating, and Cooking by Gas. Including Scientific Helps to Engineer-students and others. With Illustrated Diagrams, By E. E. PERKINS. I2mo., cloth $1.25 PERKINS AND STOWE. A New Guide to the Sheet-iron and Boiler Plate Roller : Containing a Series of Tables showing the Weight of Slabs and Pile* to Produce Boiler Plates, and of the Weight of Piles and the Sizes of Bars to produce Sheet-iron; the Thickness of the Bar Gauga in decimals ; the Weight per foot, and the Thickness on the Bar or Wire Gauge of the fractional parts of an inch; the Weight per sheet, and the Thickness on the Wire Gauge of Sheet-iron of various dimensions to weigh 112 ibs. per bundle; and the conversion of Short Weight into Long Weight, and Long Weight into Short. Estimated and collected by G. H. PERKINS and J. G. STOWE. $2.50 POWELI CHANCE HARRISc The Principles of Glass Making. By HARRY J. POWELL, B. A. Together with Treatises on Crown and Sheet Glass; by HENRY CHANCE, M. A. And Plate Glass, by H. G. HARRIS, Asso. M. Inst. C. E. Illustrated i8mo. . $1.50 PROCTOR. A Pocket-Book of Useful Tables and Formulae for Marine Engineers : By FRANK PROCTOR. Second Edition, Revised and Enlarged. Full -bound pocket-book form $1.50 REGNAULT. Elements of Chemistry: By M. V. REGNAULT. Translated from the French by T. FORREST BETTON, M. D., and edited, with Notes, by JAMES C. BOOTH, Melter and Refiner U. S. Mint, and WILLIAM L. FABER, Metallurgist and Mining Engineer. Illustrated by nearly 700 wood-engravings. Com- prising nearly 1,500 pages. In two volumes, 8vo., cloth . $7.50 RICHARDS. Aluminium : Its History, Occurrence, Properties, Metallurgy and Applications, including its Alloys. By JOSEPH W. RICHARDS, A. C., Chemist and Practical Metallurgist, Member of the Deutsche Chemische Gesell- schaft. Illustrated $5 .00 RIFFAULT, VERGNAUD, and TOUSSAINT. A Practical Treatise on the Manufacture of Colors for Painting : Comprising the Origin, Definition, and Classification of Colors; the Treatment of the Raw Materials ; the best Formulae and the Newest Processes for the Preparation of every description of Pigment, and the Necessary Apparatus and Directions for its Use ; Dryers ; tho Testing. Application, and Qualities of Paints, etc., etc. By MM. RIFFAULT, VERGNAUD, and TOUSSAINT. Revised and Edited by M. HENRY CAREY BAIRD & CO.'S CATALOGUE. 23 F. MALEPEYRE. Translated from the French, by A. A. FESQUW; Chemist and Engineer. Illustrated by Eighty engravings. In one vol., 8vo., 659 pages $7-S& ROPER. A Catechism of High-Pressure, or Non- Condensing. Steam -Engines : Including the Modelling, Constructing, and Management of Steam* Engines and Steam Boilers. With valuable illustrations. By STE- PHEN ROPER, Engineer. Sixteenth edition, revised and enlarged. i8mo., tucks, gilt edge $2.OQ ROPER. Engineer's Handy-Book: Containing a full Explanation of the Steam-Engine Indicator, and its Use and Advantages to Engineers and Steam Users. With Formula for Estimating the Power of all Classes of Steam-Engines ; also, Facts, Figures, Questions, and Tables for Engineers who wish to qualify themselves for the United States Navy, the Revenue Service, the Mercantile Marine, or to take charge of the Better Class of Sta- tionary Steam-Engines. Sixth edition. i6mo., 690 pages, tucks, gilt edge . #3.50 ROPER. Hand-Book of Land and Marine Engines : Including the Modelling, Construction, Running, and Management of Lane 1 and Marine Engines and Boilers. With illustrations. By STEPHEN ROPER, Engineer. Sixth edition. I2mo.,tvcks, gilt edge. #3-50 ROPER. Hand-Book of the Locomotive : Including the Construction of Engines and Boilers, and the Construc- tion, Management, and Running of Locomotives. By STEPHEN ROPER. Eleventh edition. i8mo., tucks, gilt edge . $2.50 ROPER. Hand-Book of Modern Steam Fire-Engines. With illustrations. By STEPHEN ROPER, Engineer. Fourth edition, I2mo., tucks, gilt edge $3-S ROPER. Questions and Answers for Engineers. This little book contains all the Questions that Engineers will be asked when undergoing an Examination for the purpose of procuring Licenses, and they are so plain that any Engineer or Fireman of or dinary intelligence may commit them to memory in a short time. By STEPHEN ROPER, Engineer. Third edition . . . $3.00 HOPER. Use and Abuse of the Steam Boiler. By STEPHEN ROPER, Engineer. Eighth edition, with illustrations. l8mo., tucks, gilt edge $2.00 ROSE. The Complete Practical Machinist : Embracing Lathe Work, Vise Work, Drills and Drilling, Taps and Dies, Hardening and Tempering, the Making and Use of Tools, Tool Grinding, Marking out Work, etc. By JOSHUA ROSE. Illus* trated by 356 engravings. Thirteenth edition, thoroughly revisee Experiments in Science. By T. O'CoNOR SLCANE, E. M., A. M., Fh. D. Illustrated by 91 engravings. I2mo. $1.50 SMEATON. Builder's Pockt^ Companion : Containing the Elements of Building, Surveying, and Architecture ; with Practical Rules and Instructions connected with the subject. ' By A. C. SMEATON, Civil Engineer, etc. I2mo. . . $1.50 SMITH. A Manual of Political Economy. By E. PESHINE SMITH. A New Edition, to which is added a full Index. I2mo $i 25 HENRY CAREY EAIRD & CO.'S CATALOGUE. 25 SMITH. Parks and Pleasure - Grounds : Or Practical Notes on Country Residences, Villas, Public Parks, and Gardens. By CHARLES H. J. SMITH, Landscape Gardener and Garden Architect, etc., etc. I2mo. .... $2.00 SMITH. The Dyer's Instructor: Comprising Practical Instructions in the Art of Dyeing Silk, Cotton, Wool, and Worsted, and Woolen Goods ; containing nearly 800 Receipts. To which is added a Treatise on the Art of Padding; ancj the Printing of Silk Warps, Skeins, and Handkerchiefs, and th various Mordants and Colors for the different styles of such work.- By DAVID SMITH, Pattern Dyer. I2mo. . . . $2.00 SMYTH. A Rudimentary Treatise on Coal and Coal- Mining. By WARRINGTON W. SMYTH, M. A., F. R. G., President R. G. S, of Cornwall. Fifth edition, revised and corrected. With numer- ous illustrations. I2mo. #l75 SNIVELY. Tables for Systematic Qualitative Chemical AnaK ysis. By JOHN H. SNIVELY, Phr. D. 8vo. . . . . $1.00 SNIVELY. The Elements of Systematic Qualitative Chemical Analysis : A Hand-book for Beginners. By JOHN H. SNIVELY, Phr. D. i6mo. $2.00 STOKES. The Cabinet- Maker and Upholsterer's Companion : Comprising the Art of Drawing, as applicable to Cabinet Work; Veneering, Inlaying, and Buhl- Work ; the Art of Dyeing and Stain- ing Wood, Ivory, Bone, Tortoise-Shell, etc. Directions for Lacker- ing, Japanning, and Varnishing; to make French Polish, Glues, Cements, and Compos-la' ns; with numerous Receipts, useful to work men generally. Bv STOKES. Illustrated. A New Edition, with an Appendix upor vench Polishing, Staining, Imitating, Varnishing, etc., etc. I2mo $1.25 STRENGTH AND OTHER PROPERTIES OF METALS^: Reports of Experiments on the Strength and other Properties of Metals for Cannon. With a Description of the Machines for Testing Metals, and of the Classification of Cannon in service. By Officers of the Ordnance Department, U. S. Army. By authority of the Secrc. taryofWar. Illustrated by 25 large steel plates. Quarto . $10.00 SULLIVAN. Protection to Native Industry. By Sir EDWARD SULLIVAN, Baronet, author of " Ten Chapters en Social Reforms." 8vo 1.00 SULZ. A Treatise on Beverages : Or the Complete Practical Bottler. Full instructions for Laboratory Work, with Original Practical Recipes for all kinds of Carbonated Drinks, Mineral Waters, Flavorings, Extracts, Syrups, etc. By CHAS. HERMAN SULZ, Technical Chemist and Practical Bottler. Illustrated by 428 Engravings. 818 pp. Jivo. . . $10.00 26 HENRY CAREY BAIRt? & CO.'S CATALOGUE. BYME. Outlines of an Industrial Science. By DAVID SYME. I2mo. . . j$2.ot TABLES SHOWING THE WEIGHT OF ROUND, SQUARE, AND FLAT BAR IRON, STEEL, ETC., By Measurement. Cloth ....... 63 TAYLOR. Statistics of Coal : Including Mineral Bituminous Substances employed in Arts and Manufactures; with their Geographical, Geological, and Commercial Distribution and Amount of Production and Consumption on the American Continent. With Incidental Statistics of the Iron Manu- facture. By R. C. TAYLOR. Second edition, revised by S. S. HALDE* MAN. Illustrated by five Maps and many wood engravings. 8vo., cloth $10.00 TEMPLETON. The Practical Examinator on Steam and the Steam -Engine : With Instructive References relative thereto, arranged for the Use of Engineers, Students, and others. By WILLIAM TEMPLETON, En. gineer. I2mo. ........ $1.00 THAUSING. The Theory and Practice of the Preparation of Malt and the Fabrication of Beer : With especial reference to the Vienna Process of Brewing. Elab- orated from personal experience by JULIUS E. THAUSING, Professor at the School for Brewers, and at the Agricultural Institute, Modling, near Vienna. Translated from the German by WILLIAM T. BRANNT, Thoroughly and elaborately edited, with much American matter, and according to the latest and most Scientific Practice, by A. SCHWAKZ and DR. A. H. BAUER. Illustrated by 140 Engravings. 8vo., 815 pages . . . . . . ... . . $10.00 THOMAS. The Modern Practice of Photography: By R. W. THOMAS, F. C. S. 8vo. .... 25 THOMPSON. Political Economy. With Especial Reference to the Industrial History of Nations : By ROBERT E. THOMPSON, M. A., Professor of Social Science in the University of Pennsylvania. I2mo. .... $1.50 THOMSON. Freight Charges Calculator: By ANDREW THOMSON, Freight Agent. 2*jmo. . . $1.25 TURNER'S (THE) COMPANION: Containing Instructions in Concentric, Elliptic, and Eccentric Turn, ing; also various Plates of Chucks, Tools, and Instruments; and Directions for using the Eccentric Cutter, Drill, Vertical Cutter, and Circular Rest; with Patterns and Instructions for working them. I2mo $1.25 TURNING : Specimens of Fancy Turning Executed on the Hand or Foot- Lathe : With Geometric, Oval, and Eccentric Chucks, and Elliptical Cutting Frame. By an Amateur. Illustrated by 30 exquisite Photographs. 4*o. $3.00 HENRY CAREY BAIRD & CO.'S CATALOGUE. 27 VAILE. Galvanized- Iron Cornice-Worker's Manual: Containing Instructions in Laying out the Different Mitres, and Making Patterns for all kinds of Plain and Circular Work. Also, 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 engravings. 8vo., 450 pages $6.00 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- gineer. With Illustrations. I2mo. . . . . $1.2$ VOQDES. The Architect's and Builder's Pocket- Companion and Price-Book : Consisting of a Shoit but Comprehensive Epitome of Decimals, Duo- decimals, Geometry and Mensuration ; with Tables of United States Measures, Sizes, Weights, Strengths, etc., of Iron, Wood, Stone, .Brick, Cement and Concretes, Quantities of Materials in given Sizes and Dimensions of Wood, Brick and Stone; and full and complete Bills of Prices for Carpenter's Work and Painting; also, Rules for Computing and Valuing Brick and Brick Work, Stone Work, Paint- ' ing, Plastering, with a Vocabulary of Technical Terms, etc. By FRANK W. VOGDES, Architect, Indianapolis, Ind. Enlarged, revised, and corrected. In one volume, 368 pages, full-bound, pocket-book form, gilt edges 2.00 Cloth . l.SQ VAN CLEVE. The English and American Mechanic : Comprising a Collection of Over Three Thousand Receipts, Rules, and Tables, designed for the Use of every Mechanic and Manufac- turer. By B. FRANK VAN CLEVE. Illustrated. 500 pp. I2mo. $2.00 WAHNSCHAFFE. A Guide to the Scientific Examination of Soils: Comprising Select Methods of Mechanical and Chemical Analysis and Physical Investigation. Translated from the German of Dr. F. WAHNSCHAFFE. With additions by WILLIAM T. BRANNT. Illus- trated by 25 engravings. I2mo. 177 pages . . . #1.50 WALL. Practical Graining : With Descriptions of Colors Employed and Tools Used. Illustrated by 47 Colored Plates, Representing the Various Woods Used E Interior Finishing. By WILLIAM E. WALL. 8vo. . $2.5? WALTON. Coal-Mining Described and Illustrated: By THOMAS H. WALTON, Mining Engineer. Illustrated by 24 large and elaborate Plates, after Actual Workings and Apparatus. $5.00, 28 HENRY CAREY BAIRD & CO.'S CATALOGUE. WARE. The Sugar Beet. Including a History of the Beet Sugar Industry in Europe, Varietiei of the Sugar Sect, Examination, Soils, Tillage, Seeds and Sowing^ Yield and Cost of Cultivation, Harvesting, Transportation, Conserve tion, Feeding Qualities of the Beet and of the Pulp, etc. By LEWII S. WARE, C. E., M. E. Illustrated by ninety engravings. 8vo. WARN. The Sheet-Metal Worker's Instructor: For Zinc, Sheet-Iron, Copper, and Tin-Plate Workers, etc. Contain- ing a selection of Geometrical Problems ; also, Practical and Simple Rules for Describing the various Patterns required in the different branches of the above Trades. By REUBEN H. WARN, Practical Tin-Plate Worker. To which is added an Appendix, containing Instructions for Boiler-Making, Mensuration of Surfaces and Solids, Rules for Calculating the Weights of different Figures of Iron and Steel, Tables of the Weights of Iron, Steel, etc. Illustrated by thirty- two Plates and thirty-seven Wood Engravings. 8vo. . $3.00 WARNER. New Theorems, Tables, and Diagrams, for the Computation of Earth-work : Designed for the use of Engineers in Preliminary and Final Estimates, of Students in Engineering, and of Contractors and other non-profesi sional Computers. In two parts, with an Appendix. Part I. A Prac- tical Treatise; Part II. A Theoretical Treatise, and the Appendix, , Containing Notes to the Rules and Examples of Part I. ; Explana- tions of the Construction of Scales, Tables, and Diagrams, and a Treatise upon Equivalent Square Bases and Equivalent Level Heights. The whole illustrated by numerous original engravings, comprising explanatory cuts for Definitions and Problems, Stereometric Scales and Diagrams, and a series of Lithographic Drawings from Models i Showing all the Combinations of Solid Forms which occur in Railroad Excavations and Embankments. By JOHN WARNER, A. M., Mining and Mechanical Engineer. Illustrated by 14 Plates. A new, revised and improved edition. 8vo. ...... $4.00 WATSON. A Manual of the Hand-Lathe : Comprising Concise Directions for Working Metals of all kinds, Ivory, Bone and Precious Woods; Dyeing, Coloring, and French Polishing; Inlaying by Veneers, and various methods practised to produce Elaborate work with Dispatch, and at Small Expense. By EGBERT P. WATSON, Author of " The Modern Practice of American Machinists and Engineers." Illustrated by 78 engravings. $1.50 WATSON. The Modern Practice of American Machinists and Engineers : Including the Construction, Application, and Use of Drills, Lathe Tools, Cutters for Boring Cylinders, and Hollow-work generally, with the most Economical Speed for the same ; the Results verified by Actual Practice at the Lathe, the Vise, and on the Floor. Together HENRY CAREY BAIRD & CO.'S CATALOGUE. 29 with Work*top Management, Economy of Manufacture, the Steam Engine, Boilers, Gears, Belting, etc., etc. By EGBERT P. WATSON, Illustrated by eighty-six engravings. I2mo. . . . jJte-50 WATSON. The Theory and Practice of the Art of Weaving by Hand and Power With Calculations and Tables for the Use of those connected with the Trade. By JOHN WATSON, Manufacturer and Practical Machine- Maker. Illustrated by large Drawings of the best Power Looms. 8vo. ...* . $6.00 , WATT. The Art of Soap Making: A Practical Hand-book of the Manufacture of Hard and Soft Soaps, Toilet Soaps, etc., including many New Processes, and a Chapter on the Recovery of Glycerine from Waste Leys. By ALEXANDER WATT. 111. i2mo #3.00 WEATHERLY. Treatise on the Art of Boiling Sugar, Crys- tallizing, Lozenge-making, Comfits, Gum Goods, And other processes for Confectionery, etc., in which are explained. in an easy and familiar manner, the various Methods of Manufacture ig every Description of Raw and Refined Sugar Goods, as aold by Confectioners and others. I2mo $I5 WIGHTWICK. Hints to Young Architects: Comprising Advice to those who, while yet at school, are destined to the Profession ; to such as, having passed their pupilage, are about to travel ; and to those who, having completed their education, are about to practise. Together with a Model Specification involving a great variety of instructive and suggestive matter. By GEORGB WIGHTWICK, Architect. A new edition, revised and considerably enlarged; comprising Treatises on the Principles of Construction and Design. By G. HUSKISSON GUILLAUME, Architect. Numerous Illustrations. One vol. I2mo #2.00 WILL. Tables of Qualitative Chemical Analysis. With an Introductory Chapter on the Course of Analysis. By Pro- fessor HEINRICH WILL, of Giessen, Germany. Third American, from the eleventh German edition. Edited by CHARLES F. HIMES, Ph. D., Professor of Natural Science, Dickinson College, Carlisle, Pa- 8vo. ' . #1-50 WILLIAMS. On Heat and Steam : Embracing New Views of Vaporization, Condensation, and ExpV> sion. By CHARLES WYE WILLIAMS, A. I. C. E. Illustrated 8vo. $2.50 WILSON. A Treatise on Steam Boilers : Their Strength, Construction, and Economical Working. By RoBERt WILSON. Illustrated I2mo #2.50 WILSON. First Principles of Political Economy: With Reference to Statesmanship and the Progress of Civilization, tty Professor W. D. WILSON, of the Cornell University. A new and revised edition. I2mo. . . . , . . . $i-S a 30 HENRY CAREY BAIRD & CO.'S CATALOGUE. WOHLER. A Hand-Bookof Mineral Analysis: By F. WOHLER, Professor of Chemistry in the University of GSttin- gen. Edited by HENRY B. NASON, Professor of Chemistry in the Renssalaer Polytechnic Institute, Troy, New York. Illustrated. I2mo. . *? en . pz.^u WORSSAM. On Mechanical Saws : From the Transactions of the Society of Engineers, 1869. By S. W. WORSSAM, JR. Illustrated by eighteen large plates. 8vo. #2.50 RECENT ADDITIONS. BRANNT. Varnishes, Lacquers, Printing Inks, and Sealing Waxes : Their Raw Materials and their Manufacture. 39 Illustrations. I2mo. 338 pages. $3.00 BRANNT The Practical Scourer and Garment Dyer: Comprising Dry or Chemical Cleaning ; the Art of Removing Stains ; Fine Washing ; Bleaching and Dyeing of Straw Hats, Gloves, and Feathers of all kinds; Dyeing of Worn Clothes of all fabrics, in- cluding Mixed Goods, by One Dip; and the Manufacture of Soaps and Fluids for Cleansing Purposes. Edited by WILLIAM T. BRANNT, Editor of "The Techno-Chemical Receipt Book." Illustrated. 203 pages. I2mo. $2.00 BRANNT. The Metallic Alloys : A Practical Guide for the Manufacture of all kinds of Alloys, Amal- gams and Solders used by Metal Workers, especially by Bell Founders, Bronze Workers, Tinsmiths, Gold and Silver Workers, Dentists, etc., etc., as well as their Chemical and Physical Properties. Edited chiefly from the German of A. Krupp and Andreas Wildberger, with additions by WM. T. BRANNT. Illustrated. I2mo. $3.00 BRANNT. A Practical Treatise on the Manufacture of Vine- gar and Acetates, Cider, and Fruit- Wines : Preservation of Fruits and Vegetables by Canning and Evaporation ; Preparation of Fruit-Butters, Jellies, Marmalades, Catchups, Pickles, Mustards, etc. Edited from various sources. By WILLIAM T. BRANNT. Illustrated by 79 Engravings. 479 pp. 8vo. $5.00 BRANNT. The Metal Worker's Handy-Book of Receipts and Processes : Being a Collection of Chemical Formulas and Practical Manipula- tions for the working of all Metals; including the Decoration and Beautifying of Articles Manufactured therefrom, as well as their Preservation. Edited from various sources. By WILLIAM T. BRANNT. Illustrated. iamo. $2.50 HENRY CAREY BAIRD & CO.'S CATALOGUE. 3I DEITE. A Practical Treatise on the Manufacture of Per- fumery : Comprising directions for making all kinds of Perfumes, Sachet Powders, Fumigating Materials, Dentifrices, Cosmetics, etc., with a full account of the Volatile Oils, Balsams, Resins, and other Natural and Artificial Perfume-substances, including the Manufacture of Fruit Ethers, and tests of their purity. By Dr. C. DEITE, assisted by L. BORCHERT, F. EICHBAUM, E. KUGLER, H. TOEFFNER, and other experts. From the German, by WM. T. BRANNT. 28 Engrav- ings. 358 pages. 8vo. $3.00 EDWARDS. American Marine Engineer, Theoretical and Practical : With Examples of the latest and most approved American Practice. By EMORY EDWARDS. 85 illustrations. 12010. . . $2.50 EDWARDS. 900 Examination Questions and Answers : For Engineers and Firemen (Land and Marine) who desire to ob- tain a United States Government or State License. Pocket-book form, gilt edge , . . . $1.5 POSSELT. Technology of Textile Design : Being a Practical Treatise on the Construction and Application of Weaves for all Textile Fabrics, with minute reference to the latest Inventions for Weaving. Containing also an Appendix, showing the Analysis and giving the Calculations necessary for the Manufac- tuie of the various Textile Fabrics. By . A. POSSELT, Head Master Textile Department, Pennsylvania Museum and School of Industrial Art, Philadelphia, with over 1000 illustrations. 293 pages. 410. . $5- POSSELT. The Jacquard Machine Analysed and Explained: With an Appendix on the Preparation of Jacquard Cards, and Practical Hints to Learners of Jacquard Designing. By E. A. POSSELT. With 230 illustrations and numerous diagrams. 127 pp. 4to $3.00 POSSELT. The Structure of Fibres, Yarns and Fabrics : Being a Practical Treatise for the Use of all Persons Employed in the Manufacture of Textile Fabrics, containing a Description of the Growth and Manipulation of Cotton, Wool, Worsted, Silk, Flax, Jute, Ramie, China Grass and Hemp, and Dealing with all Manu- facturers' Calculations for Every Class of Material, also Giving Minute Details for the Structure of all kinds of Textile Fabrics, and an Appendix of Arithmetic, specially adapted for Textile Purposes. By E. A. POSSELT. Over 400 Illustrations, quarto. . $10.00 RICH. Artistic Horse-Shoeing: A Practical and Scientific Treatise, giving Improved Methods of Shoeing, with Special Directions for Shaping Shoes to Cure Different Diseases of the Foot, and for the Correction of Faulty Action in Trotters. By GEORGE E. RICH. 62 Illustrations. 153 pages. I2ino $1.00 32 HENRY CAREY BAIRD & CO.'S CATALOGUE. RICH ARDSON. Practical Blacksmithing : A Collection of Articles Contributed at Different Times by Skilled Workmen to the columns of " The Blacksmith and Wheelwright," and Covering nearly the Whole Range of Blacksmithing, from the Simplest Job of Work to some of the Most Complex Forgings. Compiled and Edited by M. T. RICHARDSON. Vol.1. 210 Illustrations. 224 pages. I2mo. . . $1.00 Vol. II. 230 Illustrations. 262 pages. I2mo. . . $1.00 Vol. III. 390 Illustrations. 307 pages. I2mo. . . #1.00 Vol. IV. 226 Illustrations. 276 pages. I2mo. , . $1.00 RICHARDSON. The Practical Horseshocr: Being a Collection of Articles on Horseshoeing in all its Branchet which have appeared from time to time in the columns of " 1 he Blacksmith and Wheelwright," etc. Compiled and edited by M, T. RICHARDSON. 174 illustrations $1.00 ROPER. Instructions and Suggestions for Engineers and Firemen : By STEPHEN ROPER, Engineer. i8mo. Morocco . #2.00 ROPER. The Steam Boiler: Its Care and Management: By STEPHEN ROPER, Engineer. I2mo., tuck, gilt edges. $2.00 ROPER. The Young Engineer's Own Book: Containing an Explanation of the Principle and Theories on which the Steam Engine as a Prime Mover is Based. By STEPHEN ROPER, Engineer. 160 illustrations, 363 pages. i8mo., tuck . $3.00 ROSE. Modern Steam -Engines: An Elementary Treatise upon the Steam-Engine, written in Plain language ; for Use in the Workshop as well as in the Drawing Office. Giving Full Explanations of the Construction of Modern Steam. Engines : Including Diagrams showing their Actual operation. To- gether with Complete but Simple Explanations of the operations of Various Kinds of Valves, Valve Motions, and Link Motions, etc., thereby Enabling the Ordinary Engineer to clearly Understand the Principles Involved in their Construction and Use, and to Plot out their Movements upon the Drawing Board. By JOSHUA ROSE. M. E. Illustrated by 422 engravings. Revised. 358 pp. . . $6.00 ROSE. Steam Boilers: A Practical Treatise on Boiler Construction and Examination, for the Use of Practical Boiler Makers, Boiler Users, and Inspectors; and embracing in plain figures all the calculations necessary in Designing or Classifying Steam Boilers. By JOSHUA ROSE, M. E. Illustrated by 73 engravings. 250 pages. 8vo $2.^0 SCHRIBER. The Complete Carriage and Wagon Painter: A Concise Compendium of the Art of Painting Carriages, Wagons, and Sleighs, embracing Full Directions in all the Various Branches, including Lettering, Scrolling, Ornamenting, Striping, Varnishing, and Coloring, with numerous Recipes for Mixing Colors. 73 Illus- trations. 177 pp. I2mo. . . . . . $1.00 RETURN CIRCULATION DEPARTMENT 202 Main Library 642-3403 LOAN PERIOD T 2 3 4 5 6 LIBRARY USE This book is due before closing time on the last date stamped below DUE AS STAMPED BELOW 'APR 9fi86 fiECCIRC 85 LIBRARY USE AUG 25 198 RECEIVE! AUG d. 5 CULATION DEPT. UNIVERSITY OF CAL.. FORM NO. DD6A, 20m, 1 1/78 BERKELEY CA -*.*-i 20 VR 10894 GENERAL LIBRARY -U.C. BERKELEY BOOD771B75 DIVERSITY OF CALIFORNIA LIBRARY