REPORT 
 
 OP THE 
 
 SECRETARY OF THE NAVY, 
 
 Communicating, in Compliance with a Resolution of the Senate, 
 
 A Report of the Engineer-in-Chief of the Navy, on the 
 Comparative Value of Anthracite & Bituminous Coals. 
 
 MAY, 1852. 
 
R3BPORT 
 
 OF. THE 
 
 SECRETARY OF THE NAVY, 
 
 COMMUNICATING, IN COMPLIANCE WITH A RESOLUTION OF THE SENATE, 
 
 A Report of the Engineer-in-Chief of the Navy, on the Com- 
 parative Value of Anthracite and Bituminous Coals. 
 
 May 24, 1852 — Ordered to lie on the table. 
 
 May 27, 1852 — Referred to the Committee on Naval Affairs, and 
 ordered to he printed. 
 
 Navy Department, May 21, 1852. 
 
 Sir : I have the honor to submit the enclosed report of the Engineer- 
 in-chief of the Navy, on the comparative value of anthracite and bitu- 
 minous coals, called for by a resolution of the Seuate, passed on the 17th 
 instant. 
 
 I have the honor to be, sir, with high respect, your obedient servant, 
 
 C. M. CONRAD, 
 
 , Acting Secretary of the JSTavy. 
 
 Hon. Wm. R. King, President of the Senate. 
 
 Office of Engineer-in-Chief, U. S. N., ) 
 February 24, 1852. ] 
 
 Sir : In compliance with your instructions, made in conformity to the 
 orders of the Navy Department in June last, to test the comparative value 
 of Anthracite and Bituminous Coals for the purpose of generating steam, 
 I have the honor to report : 
 
 That on the completion of the pumping engine of the dry dock of the 
 New York Navy Yard, I caused experiments to be made with bituminous 
 (Cumberland) and Anthracite (white ash) Coals; and also on the oomple- 
 tion of the United States steamer “Fulton,” in January last, I made a 
 
2 
 
 series of experiments with the same varieties of coals : the condensed 
 results of all which are herein given. In addition, I would also state, 
 that the United States steamer “ Fulton” has been on constant duty 
 several days since the experiments were made, burning constantly White 
 j^sh Anthracite. 
 
 From a letter from her chief engineer, H. Hunt, Esq., detailing her 
 performance for the first four days, I extract the following : The engine 
 worked as well as any I ever saw, but the boilers exceeded my calcula- 
 tions ; with clean fires very easily keeping forty pounds, cutting off at 
 half stroke without blowers. I will here predict that she (the ‘‘Fulton”) 
 will do more service at less expense, than any steamer government will 
 have in five years. Whilst she was out on the first four days I was in her, 
 we were frequently shut off or cutting off to run slow, and turning around, 
 running from one vessel to another, so no calculations could be made of 
 her speed or slip of wheel. The furnace doors were open full half the 
 time, to keep steam down, so much more fuel was used than necessary, but 
 the nature of our service was such, that it could not be avoided.” 
 
 In consequence of the ill health of the chief engineer, he was not able 
 to return in her second trip ; the results of her consumption of coal on 
 that occasion, are therefore extracted from a letter written by the assistant 
 engineer, S. McElroy, showing the following ; “Running time with White 
 Ash Anthracite, January 25 to 28, seventy-one hours. Total coal used, 
 69,480 pounds, average 992 pounds per hour.” The above extracts are 
 made, not because they are the most favorable which occur in the log, but 
 as they show the action of the engine and boilers for several consecutive 
 hours. Nothing can be smoother than the motion of the engine under 
 ordinary running circumstances ; and in relation to the generative power 
 of the boilers, it is more difficult to keep steam down than up. 
 
 It is unnecessary to use the blowers for ordinary work, as the natural 
 draught proves abundantly sufficient for twenty to twenty-five pounds of 
 steam, with sixteen to eighteen turns ; although they are undoubtedly of 
 great value in cases of emergency, and necessary to the prompt and proper 
 management of the fire room, with Anthracite Coal. The “ Fulton” will 
 have no difficulty whatever in making twelve knots in ordinary sea weather 
 as long as the bunkers hold out. 
 
 A more extended series of experiments would undoubtedly be more 
 favorable to the anthracite, owing to the fact that small quantities were 
 put in the furnaces and almost entirely consumed while the engine was 
 working ; it being well known that a small body of bituminous coal will 
 burn longer than the same amount of anthracite spread thinly over the 
 grates. 
 
 The cost of the two kinds of coals used in the experiments were as 
 follows, at the New York-Navy Yard : anthracite |3 90 per ton, bitumi- 
 nous ^5 65 per ton. 
 
 I have made no comparison of the relative costs of the two kinds of 
 coal, as it may vary according to different localities and periods of delivery, 
 and cannot therefore be considered a fixed element ; but have confined the 
 results entirely to their generating powers, deduced from the following 
 experiments. 
 
3 
 
 1. Experiments with bituminous coal, made with the boilers of the United 
 
 States steamer Fulton, at the J^ew York Jfavy Yard, January, 1852. 
 
 The temperature of the water in the boilers being at 38^ F., and the 
 temperature of the boiler room 18°, the fires were lighted at ten hours 
 thirty minutes, A. M. 
 
 At eleven hours forty minutes, A. M., the temperature of the water was 
 212° F., and steam began to be generated at the atmospheric pressure.- 
 Time raising steam, seventy minutes. The temperature of the boiler-room 
 had now increased from 18° to 32° F. At eleven hours fifty-four minutes 
 A. M. the steam pressure in the boilers was thirty pounds per square inch 
 above the atmosphere. Time of obtaining thirty pounds of steam, one hour 
 twenty-four minutes from a temperature of 32° F. Up to this time there 
 had been fed into the furnaces one thousand pounds of dry pine wood, equal 
 to five hundred pounds of coal, and two thousand eight hundred and twenty- 
 six pounds of (Cumberland) bituminous coal. Total, three thousand three 
 hundred and twenty-six pounds. 
 
 The engine was now set in operation to work off all the steam, which 
 the above amount of coal would generate, no more being fed to the furnaces. 
 In fifty-three minutes the steam pressure was reduced from forty pounds to 
 five pounds, and the number of double strokes of piston made from forty-one 
 to seven, when the engine was stopped. During the time the engine was 
 in operation, the steam was cut off at half stroke. 
 
 The engine consisted of one cylinder, fifty inches diameter, and ten feet 
 four inches stroke. The space between cut off valve and piston, including 
 clearance, to be filled with steam per stroke is 3.094 cubic feet. The cal- 
 culation of the amount of water evaporated is made from the quantities of 
 steam measured out by the cylinder, divided by the relative bulks of steam 
 of the experimental pressures and the water from which it is generated. 
 
 The initial pressure of the steam in the cylinder is taken at one pound 
 less than in the boilers. The space displacement of piston filled with steam, 
 per stroke is 70.448 cubic feet, to which must be added the above 3.094 
 cubic feet, making a total of 73.542 cubic feet. 
 
 Time. 
 
 Mean pressure above at- 
 mosphere, per square 
 inch, in cylinder. 
 
 Number of double strokes 
 of piston made. 
 
 Cubic feet of water 
 evaporated. 
 
 MINUTES. 
 
 POUNDS. 
 
 
 
 6 
 
 32^ 
 
 41 
 
 10.326 
 
 5 
 
 25 
 
 34 
 
 7.311 
 
 5 
 
 22i 
 
 32 
 
 6.483 
 
 6 
 
 19 i 
 
 3U 
 
 5.879 
 
 5 
 
 16^ 
 
 31 
 
 5.352 
 
 5 
 
 14 
 
 30 
 
 4.796 
 
 5 
 
 Hi 
 
 26 
 
 3.797 
 
 5 
 
 9 
 
 23 
 
 3.075 
 
 5 
 
 7i 
 
 21 
 
 2.631 
 
 6 
 
 5i 
 
 12 
 
 1.393 
 
 2 
 
 4i 
 
 7 
 
 0.868 
 
 
 
 
 51.911 
 
4 
 
 Taking the weight of a cubic foot of sea water at 64.3 pounds, the total 
 weight evaporated is (51.911 X 64. 3)=:3337. 877 pounds. The boilers of 
 the Fulton contained 82.000 pounds of water at the initial temperature of 
 32° F., which was raised to 212° F., and 3337.877 pounds of it evaporated 
 by three thousand three hundred and twenty-six pounds of coal. 
 
 Now it requires five times and a half as much caloric to evaporate a given 
 •bulk of water from a temperature 212° F. as to raise it to that temperature 
 from 32° F. The quantity of fuel, therefore, expended in raising the water 
 from the initial temperature to that of 212° F., compared to that expended 
 in evaporating the 3337.877 pounds from that temperature, will be as 
 (82.000xl80°)=14,760,000 to (3337.877x990°)=3,304, 498.23, or as 
 4.4666 to 1.000; consequently pounds of coal were con- 
 
 sumed in evaporating 3337.877 pounds of sea-water, or 4.483 pounds of 
 water per pound of coal. It was intended to have made, on the following 
 day, an experiment, under precisely the same circumstances as above, with 
 anthracite ; but it was found impossible from the presence of ice to work 
 the engine, the experiment was therefore only made so far as regards the 
 time of getting up steam, with the following results, viz : 
 
 The fires were lighted with the same quantity and kind of wood, and 
 the same quantity of coal that had been used the day previous. At seven 
 hours and twenty minutes A. M. the temperature of the water in the boiler 
 being 38° F., and that of the boiler room 32° F., with the natural draft, 
 the temperature of the water at eight hours and five minutes was 212° 
 (steam,) and the boiler room 43° F. Time to generate steam forty-five 
 minutes. At eight hours and twenty minutes the steam pressure in the 
 boiler was thirty pounds per square inch. Time of obtaining thirty pounds 
 of steam from water at 38° F. was one hour. 
 
 With the bituminous coal it will be seen that it required seventy minutes 
 to obtain steam from water at the temperature of 32° F., while it only 
 required forty-five minutes with the anthracite ; being a difference of time 
 in this respect of about thirty-six per cent, of the bituminous time. 
 
 The data for a comparison of the evaporative values of the coals was 
 obtained by another experiment as follows : 
 
 Experiments with White Ash Anthracite made with the boilers of the 
 United States Steamer Fulton, in JYew York Bay, January 1, 1852. 
 
 This experiment was made with the steamer under way, while steaming 
 with steady pressure of steam and revolutions of the wheel, as follows ; 
 
 Steam pressure {initial) in cylinder per square inch above the atmos- 
 phere, twenty-five pounds ; double strokes of piston per minute, twenty- 
 one and one-third ; cutting off at from commencement of stroke, three- 
 eighths ; consumption of coal per hour, eighteen hundred pounds. 
 
 From the above data, there was filled per stroke 52.837 cubic feet of 
 the space displacement of the piston, to which add 3.094 cubic feet of 
 space comprised between cut off valve and piston, making a total of 55.931 
 cubic feet of steam of twenty-five pounds pressure, which would be per 
 minute 55.931 X42|=2386. 39 cubic feet, and per hour 143,183.40 cubic 
 feet. Dividing this last number by the relative bulks of steam of the 
 
5 
 
 pressure generated, and the water from which it was generated, we obtain 
 209.332 cubic feet of sea- water, which at 64.3 pounds per cubic 
 foot, amounts to 13,460.047 pounds, evaporated by 1800 pounds of coal, 
 or 7.478 pounds of sea- water per pound of coal. 
 
 3. Experiment with white ash anthracite coal made with the boilers of the 
 pumping engine at the United States Dry Dock, JSTew York JYavy Yard. 
 
 A comparative experiment was made with the boilers of the pumping 
 engine at the New York Navy-Yard, in October, 1851, on the comparative 
 advantages of anthracite and bituminous coals ; all the conditions were as 
 nearly alike as practicable. With the anthracite coal a combustion of nine 
 hundred and eighty pounds per hour, evaporated a sufficient quantity of 
 water to supply the engine with steam of twelve pounds pressure above 
 the atmosphere, per square inch, for four hundred and twenty- five double 
 strokes of piston per hour, the steam pressures being alike in both cases ; 
 the economical values of the coals will be represented by the number of 
 double strokes of piston made, divided by the quantity of fuel per given unit 
 
 of time ; or will be, anthracite ^^=0.4337 : bituminous 0.2673, 
 
 or the anthracite is better than the bituminous in the proportion of 
 
 ^^'^=1.623 to 1.000. 
 
 0.2673 
 
 It is proper to remark that these boilers were expressly designed for 
 burning bituminous coal. 
 
 COMPARISON. 
 
 The coals used in these experiments were the kinds furnished by the 
 agents of the government for the use of the United States Navy-Yard 
 and Steamers, and was taken indiscriminately from the piles in the yard 
 without assorting. 
 
 The bituminous was from the Cumberland” mines. The anthracite 
 was the kind known as White Ash Schuylkill.” 
 
 From the preceding data, it appears that in regard to the rapidity of 
 
 getting up” steam, the anthracite exceeds the bituminous thirty-six per 
 cent. 
 
 That in economical evaporation per unit of fuel, the anthracite exceeds 
 the bituminous in the proportion of 7.478 to 4.483 or 66.8 per cent. 
 
 It will also be perceived, that the jesult of the third experiment on the 
 boilers of the pumping engine at the New York Dry Dock, which experi- 
 ment was entirely differently made and calculated from the first and 
 second experiments, gave an economical superiority to the anthracite over 
 the bituminous of 62.3 per cent. 5 a remarkably close approximation to the 
 result obtained by the experiments on the “ Fulton^ s^’ boilers, ( 66.8 per 
 cent.,) particularly when it is stated that the boilers and grates of the 
 pumping engine were made with a view to burning bituminous coal, which 
 
6 
 
 has been used since their completion : while those of the Fulton” were 
 constructed for the use of anthracite. The general characters of the boilers 
 were similar, both having return drop flues. 
 
 Thus it will be seen, from the experiments, that, without allowing for the 
 difference of weight of coal that can be stowed in the same bulk, the en- 
 gine using anthracite could steam about two-thirds longer than with 
 bituminous. 
 
 These are important considerations in favor of anthracite coal for the 
 uses of the Nav}"; without taking into account the additional amount of 
 anthracite more than bituminous that can be placed on board a vessel in 
 the same bunkers, or the advantages of being free from smoke, which in a 
 war-steamer may at times be of the utmost importance in concealing the 
 movements of the vessel, and also the almost, if not altogether, entire free- 
 dom from spontaneous combustion. 
 
 The results of the experiments made last spring on the United States 
 steamer Vixen” were so favorable, that I recommended to the Bureau of 
 Construction, &c., the use of anthracite for all naval steamers at that time 
 having, or to be thereafter fitted with iron boilers ; particularly the steamers 
 
 Fulton,” Princeton,” and Alleghany,” the boilers for all of which 
 were designed with a special view to the use of anthracite, and with the 
 approval of that bureau. 
 
 The “ Fulton’s” bunkers are now filled with anthracite, and the con- 
 sumptions referred to in the engineer’s report on that steamer show, during 
 the short time she has been at sea, that the anticipated economy has been 
 fully realized. 
 
 In view of the results contained in this report, I would respectfully 
 recommend to the Bureau of Yards and Bocks, the use of anthracite in the 
 several Navy-Yards, and especially for the engine of the Bry-Bock at the 
 New York Navy- Yard. 
 
 In conclusion, I desire the approval of the Bureau to make such investi- 
 gations as my duties will permit, with regard to the experience of the dura- 
 bility of copper boilers, when used with bituminous or anthracite coal ) 
 which can be done without any specific expenditure. 
 
 The inquiry may prove highly important to the Navy Bepartment, as 
 the use of anthracite under copper boilers has been heretofore generally 
 considered as more injurious than bituminous coal, and is consequently not 
 used by government in vessels having copper boilers. 
 
 Bespectfully submitted, by your obedient servant, 
 
 CHAB.LES B. STUART, 
 
 Engineer-in-Chief, U. S. JTavy. 
 
 Commodore Joseph Smith, 
 
 Chief of Bureau of Yards and Docks. 
 
LETTER OF THE ENGINEER-IN-CHIEF OF THE NAVY, 
 
 IN RELATION TO COALS, 
 
 Addressed to the Chairman of the Committee on Naval Affairs. 
 
 May 27, 1852. — Referred to the Committee on Naval Affairs, and or- 
 dered to be printed. 
 
 Office Engineer-in-Chief, U. S. Navy, ) 
 
 May 27, 1852. j 
 
 Sir : The Senate, by resolution, having called for my reports to the 
 N avy Department, giving the results of several experiments to test the 
 relative value of anthracite and bituminous coals for generating steam, and 
 referred the same to the Committee on Naval Affairs, I have thought that 
 the results obtained from additional tests and experiments, made in this 
 country and England, would be of service to the committee, and trust that 
 the importance of the subject, both to the interests of the government and 
 of individuals, will be considered a sufficient apology, if any be needed, for 
 the liberty I have taken in addressing you this communication. 
 
 It should be remembered that what is required to be known on this sub- 
 ject, is neither the absolute nor relative evaporation by coals under condi- 
 tions that never occur in practice^ (as too many experiments are conducted,) 
 but the facts to be determined are, the results which can be obtained from 
 them under the ordinary circumstances in which they are used in marine 
 boilers. 
 
 With this view I have prepared the following tabular statement, showing 
 the actual evaporation of water effected by bituminous and anthracite coals 
 in the boilers of several naval steamers, and in those of some transatlantic 
 and river steamers plying to and from New York the past few years. 
 
 This table, therefore, from being prepared with care from the steam logs 
 of the different vessels (those of the navy being on file in this office) is of 
 great value ; more so, undoubtedly, than if the results had been obtained 
 from a series of special experiments made under circumstances not normal 
 to the practice, which results, therefore, must be extensively modified be- 
 fore they could be received for practical guides. 
 
 The table includes all the cases I have been able to obtain at this time, 
 where the data were unexceptionable ; it extends in most instances over a 
 course of several years steaming, and the average evaporation thus obtained, 
 although not equal sometimes to the maximum of special experiments, is, 
 in my judgment, more entitled to confidence than any single experiment 
 made with greater critical accuracy, but on too small a scale for trust- 
 worthy results. 
 
8 
 
 Of the latter character, I should rank those of W. R. Johnson, Esq., 
 made under the directions of the Navy Department, in 1843, in the report 
 of which he states that on each sample of coal were made from one to six 
 trials, according to the quantity furnished. The coal consumed in one trial 
 never exceeded 1567 pounds — this being the greatest quantity which the 
 apparatus could receive in the period allotted to each experiment, including 
 the time required for cleaning out the residue, making the necessary ad- 
 justments and preparing for a new trial. The total weight of coal consumed 
 in the trials of evaporative power has been nearly sixty-two and a half 
 tons ; and the weight used, on an average, nine hundred pounds per trial” 
 — being less, it will be seen, than half a ton per trial, or not three tons for 
 the greatest number of trials made with any one kind of coal, not equal to 
 a two hours’ consumption of an ordinary sea steamer. 
 
 These experiments were not only very limited in their extent, but were 
 made with a boiler entirely different in its construction from those in naval 
 and sea steamers, and not at all adapted for that service, and cannot therefore 
 be compared in value to the following practical tests, deduced from the 
 consumptions of hundreds of tons of coals on each steamer named and in 
 actual service. 
 
 TABLE OF PRACTICAL TESTS OF DIFFERENT VARIETIES OF COAL. 
 
 NAME OP VESSEL, 
 
 TRADE. 
 
 £ c bco 
 
 S 
 
 a 3 o V' 
 
 o) O - oi — 
 
 £ O bco 
 
 w 0) . 
 
 £ (D S 
 0,5 = ’^ • 
 <0 ^ CTo 
 
 o S S'l.s 
 
 ^ - S = S 
 
 fe 5 2 
 
 lilr 
 
 ; oii c5 
 
 REMARKS. 
 
 Michigan 
 
 Mississippi 
 
 Spitfire 
 
 Engineer 
 
 Alleghany .... 
 
 Iris 
 
 Princeton 
 
 Princeton 
 
 Princeton 
 
 Princeton 
 
 McLane 
 
 Bibb 
 
 United States.. 
 
 Herman 
 
 Baltic 
 
 City of Pittsburg 
 New W orld . . 
 Commodore. . 
 Roanoke 
 
 United States Navy 
 
 do 
 
 do 
 
 do 
 
 do 
 
 do 
 
 do 
 
 do 
 
 do 
 
 do 
 
 do 
 
 do . . 
 
 do 
 
 do . . 
 do . . 
 
 do . 
 do . 
 do . 
 do . 
 
 United StatesTreas’y 
 
 , . do do 
 
 Transatlantic packet 
 
 , . do do . 
 
 , . do do . 
 
 do do . 
 
 Hudson River 
 
 Long Island Sound . 
 N . Y ork and N orfolk 
 
 Averages 
 
 POUNDS'. 
 
 *5 000 
 t4.780 
 t4 870 
 t4.531 
 
 fs.eoo 
 
 t5.180 
 
 t6.666 
 
 §5.372 
 
 POUNDS 
 
 7 554 
 6 639 
 
 7.030 
 
 6.030 
 7.480 
 
 t4 487 
 
 8.555 
 
 t4.930 
 
 8 022 
 7.262 
 6.554 
 
 Fresh water. 
 
 Sea water, 
 do 
 do 
 do 
 
 Sea water & old flue boil. 
 Sea water and new boil, 
 do do 
 
 do do 
 
 Sea water and old boilers 
 Sea water, 
 do 
 do 
 
 Sea water and old boilers 
 Sea water, 
 do 
 do 
 do 
 do 
 
 10)51.416 
 5.142 
 
 9)65.116' 
 
 7.235* 
 
 Pittsburg coal. f Cumberland coal. | Virginia coal. § Scotch coal. 
 
9 
 
 From the averages of the above table it will be seen that the economical 
 evaporation by the anthracite exceeded that by the bituminous in the pro- 
 portion of 7.235 to 5.142, or about forty-one per centum of the latter. 
 
 In the experiments made on coals by Playfair and De la Beche, by order 
 of the British government, in 1848, I find eleven varieties of Welsh coals 
 having a constitution almost identical with the nine specimens of various 
 Pennsylvania anthracite, experimented on by J ohnson, viz : 
 
 
 Welsh anthra- 
 cite. 
 
 Pennsylvania 
 
 anthracite. 
 
 Fixed carbon 
 
 87.54 
 
 88.54 
 
 Sulphur 
 
 0.79 
 
 0.05 
 
 Other volatile matter 
 
 5 50 
 
 5 17 
 
 T’, art by ma.t.f'fir , 
 
 6.48 
 
 6.51 
 
 
 
 
 
 100.31 
 
 100.27 
 
 The average evaporation of water by the Welsh anthracite and by the 
 Pennsylvania anthracite was as follows : 
 
 Fresh water evaporated from the temperature of 212 deg. F., by one pound of coal 
 
 By Welsh anthracite pounds, . . . 9.263 
 
 By Pennsylvania anthracite do 9.590 
 
 Thus far there is a very close agreement between the results obtained by 
 the different experimenters from substantially the same coal — that coal 
 being anthracite. 
 
 In the experiments of Playfair and Be la Beche, above cited, I find three 
 varieties of Welsh bituminous, three varieties of Scotch bituminous, and 
 one variety of English bituminous, having a constitution almost identical 
 with the five specimens of Maryland (Cumberland) bituminous coal experi- 
 mented on by Johnson. 
 
 
 Welsh, Scotch, 
 and English 
 bituminous. 
 
 Maryland(Cum- 
 berland) bitu- 
 minous. 
 
 r.aTbon 
 
 75.00 
 
 1.47 
 
 14.55 
 
 8.97 
 
 75.05 
 
 Sulphur 
 
 mhpr volatile ma,tter 
 
 15 45 
 
 9.49 
 
 Earthy matters, &c 
 
 
 
 99.99 
 
 99.99 
 
 The average evaporation by the Welsh, Scotch and English bituminous 
 and by the Cumberland bituminous was as follows, viz : 
 
 Fresh water evaporated from a temperature of 212 deg. F., by one pound of coal 
 
 By Welsh, Scotch and English bituminous pounds. . . . 8.02 
 
 By Maryland (Cumberland) bituminous do 9.93 
 
Here is a great discrepancy between the results obtained by the two 
 experimenters on substantially the same coals ; Johnson making the Cum- 
 berland bituminous better than the British bituminous in the proportion of 
 no less than twenty-four and a half per centum of the latter. Had a 
 similar dilference been found in the case of anthracite between the results 
 of the two experiments, it might have been accounted for by a difference 
 of boiler or method of conducting the experiments. 
 
 From an investigation of the two kinds of boilers employed, I am of 
 opinion that though in their proportions separately different, yet in the 
 aggregate they were equivalent ; an opinion justified also by the equality 
 of results obtained with anthracite. 
 
 The results, then, of Johnson’s experiments are that Cumberland bitumi- 
 nous exceeds the Pennsylvania anthracite in economical evaporation, four 
 per centum of the latter ; while the results from the English experiments, 
 on substantially the same coals, make the economical evaporation of the 
 anthracite to exceed that of the bituminons over twenty-four per centum of 
 the latter. 
 
 I would here beg leave to remark that there were several important facts 
 attending the experiments of Professor Johnson, which, rightly understood, 
 would greatly modify his results ; and which facts it is absolutely neces- 
 sary to consider in order to arrive at correct practical information. One 
 of the most important of these is the rapidity of combustion, which is ordi- 
 narily measured by the number of pounds of coal consumed per hour per 
 square foot of grate surface, the average quantity of which in marine boilers 
 may safely be taken at fifteen pounds. 
 
 In Johnson’s experiments, however, the consumption of Cumberland bitu- 
 minous coal was at the rate of only pounds, and of anthracite 
 pounds ; an average of less than half the practical rate of consumption. 
 
 It is obvious, therefore, that the rapidity of combustion being an impor- 
 tant element in determining the evaporative efficiency of different coals, 
 that in any experiments made to ascertain this efficiency for marine boilers, 
 the rapidity of combustion should be about the average of what occurs in 
 actual practice at sea. 
 
 Again : the importance of the rate of combustion in effecting the results 
 to be obtained from anthracite or bituminous coals, are well signalized in 
 the following extract from a paper by chief-engineer Isherwood, U. S. 
 Navy, published in “Appleton’s Mechanic’s Magazine,” etc., for October, 
 1851, page 621, viz : — 
 
 “ In the combustion of bituminous coal, time is the important element, 
 and a slow rate of combustion with low velocity of draught is necessary for 
 obtaining high evaporative results, and for the following reasons, viz : The 
 bituminous portion of the coal is volatilized and separated from the fixed 
 carbon part at a lower temperature than is required for its ignition, that is, 
 than is required for its chemical union with oxygen. In this gaseous state, 
 occupying the furnaces and flues of the boiler, it can only be ignited by 
 being mixed with atmospheric air at a sufficiently high temperature 5 the 
 element of time is, therefore, doubly important ; first, to allow the gases to 
 become intimately mixed with the atmospheric air ; second, to allow them 
 to acquire the necessary high temperature. If now, by means of a power- 
 
11 
 
 ful draught, the gases, having only the low temperature due to their vola- 
 tilization, be driven so quickly through the flues and out of the chimney of 
 the boiler as not to allow them time enough to acquire the proper tempera- 
 ture for combustion, and to have the proper mixing with the atmospheric 
 air, a great loss of effect must inevitably follow. 
 
 For the economical combustion, then, of bituminous coal in generating 
 steam, there should be a slow rate of burning, or a small amount consumed 
 per unit of time per unit of surface.” 
 
 In the combustion of anthracite coal, however, the above general 
 observations do not apply. Considering the principal portions of the an- 
 thracite to be fixed carbon, there will of course be no volatilization of 
 bitumen at a lower temperature than what is required for the ignition of 
 the fixed carbon ; the coal will consequently remain unchanged until the 
 temperature is sufiiciently high for its combustion, that is, for the com- 
 bustion of its fixed carbon ; a forced draught cannot, therefore, carry off 
 the fuel before it is ignited, and in this view velocity of draught is com- 
 paratively unimportant. Again, combustion with the anthracite is effected 
 solely by the contact of the air with their solid surfaces ; there is there- 
 fore no mixing to be done, and consequently no time required to do it in. 
 Here, then, under two important conditions, great velocity of draught, 
 which is highly detrimental to the economical combustion of bituminous, is 
 unimportant in the combustion of anthracite coal.” 
 
 Taking the above views to be correct, which it is believed they are, it 
 will be perceived that the very slow rate of combustion used with the 
 bituminous coal in Johnson’s experiments, (a rate utterly out of question 
 with marine boilers) was in the highest degree favor able for the development 
 of the full heating power of the bituminous coal ; now as this rate of 
 combustion is impracticable in marine engines, a very great correction for 
 inferior results to be obtained by the faster rate of combustion must be 
 made, in order to obtain their practical value. With the anthracite, the 
 very slow rate of combustion used was positively a disadvantage, as it 
 could not keep the whole mass sufiiciently high to enable the fixed carbon 
 to take up the oxygen of the air as fast as the latter entered; consequently 
 it exerted, in a considerable degree, a cooling power. 
 
 Further, it is generally acknowledged that the quantity of carbon in 
 coals is at least an index, if not a full measure of their practical heating 
 power. This idea is entertained by Johnson himself, and is announced in 
 his work on coals, published in 1850, pages 118, 123 and 124, viz : 
 
 The British experimenters continued their analysis of the coals till 
 every sample had been submitted to both proximate and ultimate determi- 
 nation. In the American experiments time was not allowed before the re- 
 port was demanded, for extending the ultimate analyses to more than one- 
 eighth part of the samples. From such trials as were made, the deductions 
 which appeared to be authorized by a careful comparison between the con- 
 stituents of the coals and their evaporative efficiency was, that the latter de- 
 pended upon the total amount of carbon in the coal. If hydrogen had been, 
 as many European chemists had contended, the more efficient element, 
 weight for weight, then all highly bituminous coals ought to have presented 
 a greater heating power than those of lower bituminousness.” 
 
12 
 
 Botli the American and British experiments concur in proving the re- 
 verse of this to he the fact.’’ 
 
 This development finally sets aside the old calculations about the 
 relative heating powe?'s of carbon and of the hydrogen in coals. By the 
 principle of that calculation, any coal having a high degree of bituminous- 
 ness ought, in consequence of the large proportion of hydrogen in its 
 bitumen, to possess a much higher heating power than any coal of lower 
 bituminousness. The reverse of this fs true. The higher the bituminous- 
 ness, or, in other words, the greater the proportion of volatile matter a 
 coal contains, the less is its available heating power. The fact has been 
 pointed out in former publications of the writer, that when solid hydrogen 
 (that being its state in coals) is converted by the effect of heat into 
 gaseous hydrogen, it requires for this change a large amount of heat, as 
 experimentally proved in the manufacture of illuminating gas. The hy- 
 drogen thus brought to the gaseous state, assumes the same bulk at a 
 given temperature, say 212^, as it will retain at the same temperature 
 when converted into vapor of water under the atmospheric pressure ; and 
 consequently, unless we can suppose the capacity for heat of gaseous hy- 
 drogen, bulk for bulk, to be greater than that of the vapor of water, we 
 can conceive no reason why it should give out more heat in combining with 
 oxygen than it had taken up in being converted into gas. The British 
 Commissioners refer to this view of the subject, but do not clearly express 
 an opinion of its validity. 
 
 Fortunately their silence is of less importance, as their own experi- 
 ments furnish abundant proofs of the correctness of the principle. In order 
 more clearly to exhibit the independence of hydrogen efficiency in computing 
 heating powers of analyses, we have placed in the above table the per cent- 
 age of hydrogen found in each sample of coals. From this column the 
 averages are deduced, and a glance will show, that so far as any law or 
 relation is perceptible, the coals of highest heating powers are those which 
 have the lowest per centage of hydrogen.” The table above referred to 
 condensed from Johnson, stands as follows, viz : 
 
 
 Hydrogen. 
 
 Carbon. 
 
 Steam by ex- 
 periment. 
 
 Steam by cal- 
 culation. 
 
 
 
 Per cent. 
 
 Per cent. 
 
 Pounds. 
 
 Potinds. 
 
 Four coals, 
 
 average 
 
 4.13 
 
 74.15 
 
 7.78 
 
 8.03 
 
 Do 
 
 • do 
 
 4.30 
 
 76.63 
 
 8.35 
 
 8.37 
 
 Do 
 
 .do 
 
 4.57 
 
 79.67 
 
 8.65 
 
 8.60 
 
 Do 
 
 .do 
 
 4.88 
 
 81.06 
 
 8.89 
 
 8.75 
 
 Do 
 
 .do 
 
 4.17 
 
 85.68 
 
 9.17 
 
 9.25 
 
 Do 
 
 .do 
 
 4.55 
 
 88.12 
 
 9.50 
 
 9.51 
 
 Do 
 
 .do 
 
 4.47 
 
 88.99 
 
 9.75 
 
 9.75 
 
 “Thus the four coals having a heating power of 7.78, have excess of 
 hydrogen 4.13 ; the four having heating powers of 9.17, have of oxygen in 
 excess 4.17. It will also be noted that an intermediate class of coals 
 having a heating power of 8.65, has a higher per centage of hydrogen than 
 either of the above, viz : 4.57. This is as we might expect to find it, if 
 
13 
 
 the hydrogen he truly without efficiency in the practical use of coal. In- 
 deed, the hydrogen appears from the practical tests thus far adduced, no 
 more to merit the consideration as an element of evaporative effciency in 
 coal, than an equal weight of silicia, alumina, oxide of iron, or other inert 
 substance found in its earthly residuum or ashd’’ 
 
 It appears to be difficult to reconcile the foregoing and well-established 
 fac^s, with the numbers given by Professor Johnson as the results of his 
 experiments on anthracite and Cumberland (bituminous) coals, the former 
 containing per centum of carbon and the latter only 75 , per 
 
 centum, while he makes the XxHqy four per centum better than the former, 
 while it should have been as above demonstrated the reverse in the pro- 
 portion of to 75, or eighteen per centum. 
 
 The results of the British improvements on substantially the same coals, 
 viz : containing relatively 87,^,,^ and 75 per centum of carbon, gave for 
 the former a greater efficiency of twenty-four and a half per centum, 
 making a difference in the results of over twenty-eight per centum. 
 
 A large number of experiments and practical tests might be cited to fur- 
 ther prove the greater efficiency of anthracite over bituminous coals, in 
 proportion very nearly as the element of carbon was found ; but they would 
 swell this paper, now already too extended. I have therefore confined the 
 comparison to a few experiments of admitted correctness, to illustrate the 
 facts, and in conclusion would add, that I agree fully with the views 
 expressed in Professor Johnson’s report, “ that for the purpose of steam 
 navigation, therefore, the rank most important to be considered (in different 
 coals) is in the order of their evaporative power under given bulks. This 
 is obviously true, since, if other things be equal, the length of a voyage 
 must depend on the amount of evaporative power effected by the fuel which 
 can be stowed in the bunkers of a steamer, always of limited capacity. 
 With this scale of value, however, must be combined the relative freedom 
 from clinker, and the maximum rapidity of action ; while the rapidity of 
 ignition is of inferior importance, but may deserve some consideration 
 where short V 03 ^ages, frequent stoppages, and prompt commencement of 
 action are demanded” — all of which qualities I think have been from prac- 
 tical results found to be more fully combined in the white ash anthracite 
 of Pennsylvania than any other known coal. I therefore fully concur in the 
 opinion of Professor Johnson, expressed in his work on coals, published in 
 1850, page 160. 
 
 “ In conclusion I may observe, that while these analyses demonstrate 
 the high density and compactness of this coal (anthracite) fitting it for the 
 purposes of steam navigation, for which these qualities, combined with great 
 heating power, are of primary importance, they also show, that for the va- 
 rious arts and for domestic consumption, its properties are calculated to 
 sustain the high character of the central coal-field of Pennsylvania, for the 
 concentrated and durable heat which it furnishes, and the absence of those 
 ingredients which might interfere with its useful application.” 
 
 I have the honor to be, sir, with great respect, your obedient servant, 
 
 CHARLES B. STEWART, 
 Engineer-in- Chief, U. S. JV. 
 
i