126 THE SCIENTIFIC PAPERS OF 



not nearly approximate to the theoretical ones. He believed that 

 some years hence any engineer who looked at the furnace of one 

 of our present marine boilers would be ashamed of it. The mode 

 of throwing the fuel on a kind of volcano, giving off a large 

 proportion of valuable substance in the form of thick smoke, 

 was very objectionable. As far as he could follow the calculations 

 given, he thought Dr. Paul had rather overstated than otherwise 

 the theoretical evaporating power of liquid fuel as compared with 

 coal. He gave the evaporating power of hydrogen at 64 Ibs., which 

 agreed with the statement laid before the United Service Institu- 

 tion by Professor Macquorn Rankine, but there was a correction 

 to be made in that. Professor Rankine gave the evaporating 

 power of hydrogen at 64*2, and of carbon at 16 '05, but he con- 

 sidered, in this calculation, the hydrogen as existing in a gaseous 

 state, and the carbon in that of a solid. He made an allowance 

 for the chemical affinity between the hydrogen and carbon when 

 in the form of marsh gas, but he did not allow for the hydro- 

 carbon as being in a liquid condition, in which state it was when 

 in the form of oil. There must be a correction made on that 

 account, though he could not precisely say what it should be. 

 There was another correction to be made with regard to the latent 

 heat of the steam resulting from the combustion of hydrogen, by 

 which, no doubt, the results would be very sensibly modified. 

 However, if they went from theory to practice, they had certainly 

 great allowances to make in favour of the oil. For instance, coal 

 contained not only alkaline matters, but also a great deal of water, 

 which oil did not ; then, a certain portion of oxygen was already 

 absorbed by the coal, and there was a great waste by smoke. 

 Further, it was impossible, whilst burning fuel upon a grate, to 

 obtain that regularity of proportion between the air and the 

 material consumed, which was necessary to produce an economical 

 result. All these points were arguments in favour of the liquid 

 fuel. He must say, that he quite agreed with several of the 

 speakers, that volatile liquid fuel was totally inapplicable, and 

 would be one of the most dangerous things imaginable on board 

 ship ; they must, therefore, consider the question as confined to 

 the use of heavy oils, which might, no doubt, be employed with 

 advantage. They admitted of better stowage than coal, occupied 

 much less bulk, and would save on board ship a great deal of 



