302 CALORIFICATION. 



The light loses its transparency, and be- 

 comes thickened, from being colorless it be- 

 comes variegated, from being destitute of 

 temperature, it acquires it to an extreme de- 

 gree, instead of permeating transparent and 

 diaphanous bodies, and remaining in them 

 latent and unaltered ; the matter of fire, on 

 the contrary, manifests its actuality and pre- 

 sence, by the production of temperature like 

 streams of blood, that circulate through the 

 most minute vessels of a living system, it per- 



will become redhot, much sooner than the further extremity 

 of the lower one. So little is the tendency downwards in the 

 motion of fire, that COUNT RUMFORD, was enabled to make 

 the upper surface of water to boil, at a time that a cake of ice, 

 which he had placed at the bottom of the vessel, remained 

 unaltered and frozen ; and the increased degrees of tempe- 

 rature, at the top of a temple, and of a theatre, from what 

 exists at the bottom of it, must have been observed by all. 

 While fire, or the matter of heat, increases the bulk, it de- 

 creases the weight of bodies, making them lighter than 

 before, although it is more opake, than the element of light, 

 it is, perhaps, the rarest and most subtile compound which 

 exists. If its density could be measured in the element of 

 light alone, it would gravitate and fall ; but being more elas- 

 tic than the atmospheric medium in which it is situated, it 

 overcomes the resistance of the air, and rises through it. It 

 is the case with smoke, in which a large proportion of fire is 

 involved ; it is found to rise faster in a dense, than in a rare 

 atmosphere ; and it sinks altogether in a rarified one. The 

 effect is rendered very visible under a receiver, in which any 

 substance may have been burnt the smoke ascends at first 



