170 EXPEDITION TO JAPAN. 



Thus, the Cumberland coal has the aggregate advantage in value — 



Over the Formosa coal, of. 11.4 per cent. 



" Japan, (1st variety,) of. 51.1 " 



" Japan, (2d variety,) of. 44.2 " 



" Mixture of Japan, of. 50.3 " 



As far as chemical analysis and examination can go, the satio of these numbers expresses the 

 comparative value of these varieties of coal in their application to sea steamers only, for it is in 

 this connexion alone that they have been examined. 



From the fact that varying proportions of the carbon of fuel escapes combustion, or is only 

 imperfectly burned, it becomes impossible to establish the actual value of any fuel for any given 

 purpose by chemical analysis, or by any other method than by practical application on the large 

 scale. And even then, the economic value as applied to one purpose, and obtained from one 

 furnace, flue, and chimney, will be no better index of value for other purposes, with other 

 furnaces, flues, and chimneys, than a chemical analysis to the general purposes to which fuel is 

 applied. 



B. F. BACHE, 



Director Laboratory. 



