SOLID FUELS. 



77 



vessel is a most important indication, taken in connection 

 with its elementary composition. Gruner gave his opinion 

 that the real value of a coal could be determined better from 

 its proximate than from the ultimate composition. Speaking 

 of the Loire coal, he says : 



" The proximate analysis, which consists in distilling coal 

 in a retort and incinerating the residue, allows direct valu- 

 ation of the agglomerating power as well as the nature and 

 proportion of the ash. Further, it is easy to show, especially 

 with the aid of the work of Scheurer-Kestner and Meunier- 

 Dollfus, that the calorific power varies with the proportion of 

 fixed carbon left by distillation. This is true at least for all 

 coal properly so called, but not always true for anthracite 

 and lignite." * 



Gruner formed the following table based on the quantity 

 and nature of the coke furnished and the calorific power. He 

 held, from the results of S.-K. and M.-D., that if the heat 

 value of a coal increases with the proportion of fixed carbon 



* Annales des Mines, 1878, vol. IV. 



