Dr Fyfe on the Evaporative Power of Coal. 267 



its construction. I may here state, however, that with the ex- 

 ception of a slight deficiency in draught, the furnace, which 

 had from the commencement of the experiment undergone 

 numerous alterations and improvements, was considered hy 

 competent judges as built on the most approved principles ; 

 but though there is a vast loss of heat in this instance, we 

 shall find that the result, so far from being a bad one, is ra- 

 ther beyond what has been stated by others. When coal is 

 used for steam-engines, of course the quantity used must de- 

 pend very much on the power of the engine, its construction, 

 and the use to which it is applied. It has been stated, that 

 taking the average of many trials, from 10 to 15 lb. of coal are 

 required for each horse-power. Now, it is generally allowed 

 that for each horse-power a cubic foot of water must be passed 

 oft* in steam, the weight of which is 6.22 lb. Accordingly, 

 taking the smallest quantity above given, then each pound of 

 fuel will evaporate 6.22 of water. It must be allowed, that 

 the mode of testing the power of a coal by the quantity used 

 in reference to the power of the engine, is a very fallacious one ; 

 at the same time, however, as what I have stated is a practi- 

 cal result, deduced from numerous trials, I bring it forward to 

 shew, that that obtained in my experiment is not, as some 

 may at first sight be inclined to suppose it, below what usually 

 occurs. 



Anthracite. — The analysis of several specimens of Anthra- 

 cite is given by Professor Johnson in the Journal of the Frank- 

 lin Institute, Pennsylvania, of which the following is a tabu- 

 lar view : — 



Of 12 specimens analysed by Berthier, the mean per cent- 

 age of ingredients was — 



