130 THE SCIENTIFIC PAPERS OP 



into gudgeons, so as to press out the ends of the scissors ; the ends 

 of the bars being provided with little surface-plates to distribute 

 the pressure over a certain extent of surface. Such a machine, in 

 coal sufficiently tender, would work rapidly, because with one 

 piston in operation a range of at least 9 inches could be obtained, 

 and the fissure in that case would be in aid of the separation of 

 the mass. 



In the discussion of the Paper 



" ON THE PROGRESS OF LIQUID FUEL," * 

 By Captain J. H. SELWYX, 



MR. CHARLES W. SIEMENS said, as the Chairman has called 

 upon me, I may say I go so far with the author of the paper, in 

 the able manner in which he has put it forward, that in burning a 

 fuel, a hydro-carbon, such as oil is, we may expect very superior 

 results to those which we obtain from evaporating water by carbon 

 or ordinary coal. No doubt, the calculation which Captain Selwyn 

 has put before us is the correct one, according to the best facts 

 with which we are acquainted. Only I would observe that if the 

 6'4G per cent, of non-combustible matter in the oil is oxygen 

 there should be a tare allowed on account of it. 



Captain Selwyn. I think I gave that. 



Mr. Siemens. It appeared to me that Captain Selwyn did not 

 make any distinction between oxygen and mere foreign matter. 



Captain Selwyn. I took both cases and gave you the result of 

 both cases. 



Mr. Siemens. Well, in the case of oxygen, of course combus- 

 tion takes place without generation of heat, inasmuch as the fixed 

 oxygen in combining with fixed carbon produces a gaseous com- 

 pound, carbonic acid, without generating heat at all. Therefore, 

 for the equivalent of the oxygen, carbon ought to be taken off the 

 result. It may be asked, why should oil give such a superior result 



* Excerpt Transactions of the Institute of Naval Architects, Vol. X. 1869, p. 37. 



