1 10 CALORIFIC POWER OF FUELS. 



coals then in use. He analyzed and tested some thirty-five 

 different coals, domestic and foreign. The tests were made 

 with a specially built boiler, and careful and copious notes 

 were taken all through. The chimney gases were analyzed, 

 and an attempt made to determine their quantity. In 1891 

 Mr. W. Kent* reviewed his work, and found that, with correc- 

 tions for the constants employed by Johnson, the tests were 

 comparable with those made at the present time. The 

 figures given in the tables as Johnson's are with Kent's 

 corrections. 



The first experiments based on the knowledge of the 

 composition and heat of combustion of coal were published 

 in 1868 and 1869 in the Bulletin de la Socitte 1 Industrielle 

 de Mulhouse. Scheurer-Kestner remarks in the first part of 

 this work, which he prosecuted later on with assistance of 

 Meunier-Dollfus (loc. cit. p. i) : 



"It is necessary to analyze the great difference found 

 between the theoretical heat of combustion (at that time 

 no actual determinations had been made) and the practical 

 yield. 



" Several elements of the calculation aid in making this 

 shortage. The principal ones are : 



" The heat of combustion of the coal; 



" The composition of the coal; 



" The composition of the cinders as drawn from the 

 ash-pit ; 



* ' The quantity of water vaporized and the temperature 

 of the steam produced ; 



*' The volume of gases introduced under the grate, and 

 their temperature when they leave the boiler to pass into the 

 chimney ; 



''The composition of the gaseous products of combus- 

 tion ; 



* Engineering and Mining Journal, Oct. 1891. 



