183 



dk\ 4= 



+ dk 



and 



In this case we find 

 above general expressions lead to the known results. 



, and the 



II. Supplement to a Paper, read January 27, 1859, " On the 

 Thermodynamic Theory of Steam-engines with dry Satu- 

 rated Steam, and its application to practice." By W. J. 

 MACQUOEN RANKINE, C.E., F.R.S. &c.* 



(Abstract.) 



This supplement gives the dimensions, tonnage, indicated horse- 

 power, speed, and consumption of fuel, of the steam- ships whose 

 engines were the subjects of the experiments referred to in the 

 original paper. Results are arrived at respecting the available heat 

 of combustion of the coal employed, and the efficiency of the furnaces 

 and boilers, of which the following is a summary : 



Available Heat of Combustion of 1 Ib. of coal 

 1,980,000 ft.-lbs. 



Efficiency of steam x Ib. coal per I. H. P. per hour 



* Phil. Trans. 1859, p. 177 ; and Proceedings of the Royal Society, vol. ix. 

 p. 626. 



