74 CONSTITUENT, OR LATENT CALORIC 



relative proportions of each, and the laws of their 

 operation upon each other. Without hoping fully 

 to develope a subject which has hitherto baffled 

 all the efforts of preceding philosophers, I shall 

 endeavour to shew, that the methods which have 

 been employed for the purpose of estimating the 

 constituent caloric of bodies are fallacious ; the 

 application of which, to the phenomena of com- 

 bustion, respiration, evaporation, and solution, has 

 been a constant source of error. 



It has been known ever since the time of Dr. 

 Black, that different quantities of caloric are re- 

 quired to produce the same temperature, in equal 

 weights or volumes of different bodies that 1 Ib. 

 of water requires about double the quantity of 

 caloric to raise its temperature 50 or 100, that 

 1 Ib. of oil does and that, on cooling an equal 

 number of degrees, water gives out twice as much 

 caloric as an equal weight of oil : from which it 

 was inferred, that the same difference existed 

 between the latent caloric of oil and water at all 

 temperatures, down to their absolute zeros in 

 other words, that the whole amount of caloric in 

 water is double that of oil. 



This difference of capacity for caloric, as it was 

 termed by Dr. Black and his disciples, which was 

 found to exist between all other bodies, has been 

 regarded by Crawford, Kirwin, Lavoisier and 

 Laplace, Leslie and Dalton, as a measure of the 

 relative quantities of caloric which is chemically 



