CHAPTER X. 



CALORIFIC POWER OF COAL BURNT UNDER 

 A STEAM-BOILER. 



FUEL USED AND WATER EVAPORATED. 

 DISTRIBUTION OF THE HEAT PRODUCED. 



EXPERIMENTS in heating steam-boilers have to deter- 

 mine : 



1. How much water is vaporized by a given quantity of 

 coal, so as to compare it with other coals or fuels ; 



2. The evaporative power of the steam-boiler used; 



3. A comparison of the various styles of grates or meth- 

 ods of heating applied to steam-boilers. 



In this book we will consider only the first case, the 

 others being outside of its scope. 



The knowledge of the heat of combustion of coal and 

 other fuels is closely connected with experiments in heating 

 steam-boilers. It is not enough to know the proportion of 

 water which the apparatus or the fuel tested will vaporize : 

 we must also determine the number of calories lost. We 

 must know, besides, the composition of the coal and its heat 

 of combustion, to determine the proportion of calories used to 

 that possible with perfect combustion. 



The first work in this direction worth mentioning was 

 probably that done by Peclet in 1833, but his results were 

 very crude, and are of no account now. The next were those 

 made by Prof. Johnson, in 1842 and 1843, f r tne U. S. 

 Navy Department, to determine the steaming powers of the 



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