26 CALORIC* 



form fluids; because the force of attraction 

 would be overcome by the repulsive power of 

 caloric ; and the particles of bodies would separate 

 themselves indefinitely, having nothing to give 

 limits to their expansion, unless their own gravity 

 might collect them together so as to form an 

 atmosphere. 



It may be admitted, therefore, as a general prin- 

 ciple, that almost every body in nature is suscep- 

 tible of three several states of existence, solid, 

 liquid, and aeriform ; and that these states depend 

 upon the quantity of caloric combined with the 

 body. 



The elastic aeriform fluids are expressed by the 

 generic name of gas ; and in each species of gas, 

 a distinction is made between the caloric, which, 

 in some measure, serves the purpose of a solvent, 

 and the substance which, in combination with the 

 caloric, forms the base of the gas. Thus water, 

 united to a sufficient quantity of caloric, is called 

 aqueous gas ; ammoniac saturated with caloric, is 

 called ammoniacal gas, &c. 



Caloric, when free, appears to move in the form 

 of rays, and to be capable of being reflected in the 

 same manner as light. The calorific part of the 

 solar rays, or those which occasion heat, are con- 

 densed by a lens, ora mirror, as well as those which 

 produce light ; and the rays of heat from any burn- 

 ing body, or even of a body heated, although not 

 in a state of combustion, are thrown off in a radiat- 

 ing manner. If two polished metallic mirrors be 

 placed opposite to each other, at several feet dis- 

 tance, and if a pan of burning coals, or a heated 

 piece of iron, be held in the focus of one of them, a 

 thermometer placed in the focus of the opposite 

 one, will be immediately affected as if it had been 



