refpe&ing Heat or Caloric. -221 



the product differs in its capacity from the ingredients ; and 

 the fame holds in decompofitions. Had this been properly 

 attended to, it would have been found perfectly fufficient, 

 when taken along with that property by which heat tends to 

 equilibrium, to explain the paffage of heat from fub fiances to 

 other fub fiances, without ever once fuppofing the heat changed 

 in its properties. Heat feems to aft uniformly, and its effects 

 depend always on its quantity (not kind) compared with the 

 capacity of ihe body into which it enters : but it is continu- 

 ally bandied about, as it were, by the conftant changes thai 

 are puffing upon bodies, by which their capacities for receiv- 

 ing or holding it are altered; fo that it is in a conftant ftate 

 of influx and efflux in bodies, and there is going on a con- 

 ftant adjuftment, as it were, of the differences exifting among 

 them, each requiring its own fhare of the common ftock, and 

 giving off, receiving, or merely tranfmitting heat, according 

 to circumftances. Bodies are continually undergoing change 

 by the a&ion of heat. This is admitted on all hands. Is it 

 necefTary then to look for a change in the agent as well as 

 the patient ? In many refpe&s its a6lion, as we have before 

 obferved, may be illuftrated by that of water. Different fub- 

 ftances require different quantities of water to diffolve them; 

 and different fubftances require different quantities of heat to 

 diffolve them. The property which different fubftances have 

 to take in different quantities of water, may be called their 

 capacity for water : but who ever talks of a certain quantity 

 of water, when diffufed among any number of fubftances in 

 proportion to their capacities, being latent ibater P or, when 

 an interpofed hygrometer is affected by its paffage from one 

 ^idjftance to another, of its being then jenfible or free? 



IV. Re- 



