348 Of the Propagation of Heat 



When common salt is dissolved in water, the specific 

 gravity of the saturated solution is greater than that of 

 pure water, and will therefore descend in it ; and cold 

 being produced in the process, and water being a non- 

 conductor of Heat, the specific gravity of the saturated 

 solution will be still farther increased, in consequence of 

 its condensation with this cold, by which its descent in 

 the water will be still farther accelerated. 



A curious question here presents itself, which, could 

 it be resolved, might greatly tend to elucidate this ab- 

 struse subject of philosophical investigation. Suppos- 

 ing that, in a case where Heat is generated in the solu- 

 tion of a solid in a fluid menstruum, the addition to the 

 specific gravity of the menstruum, arising from its 

 chemical union with the solid, should so precisely coun- 

 terbalance the diminution of the specific gravity of the 

 Fluid, by the Heat generated in the process, that the hot 

 saturated solution should be precisely of the same speci- 

 fic gravity as the cold menstruum, would or would 

 not the process of solution be possible under such cir- 

 cumstances ? 



If the apparent tendency to approach each other, 

 which we sometimes perceive in solids and their fluid 

 menstrua, were real ; if that peculiar kind of attrac- 

 tion of predilection which has been called chemical 

 affinity has a real existence, and if its influence reaches 

 beyond the point of actual contact (as has, I believe, been 

 generally supposed), as there is no appearance of any 

 attraction whatever, or affinity, between any solid body 

 and a saturated solution of the same body in its proper 

 menstruum, it seems probable that the solution would 

 take place, under the circumstances described ; but 

 should the attraction of affinity, according to the defini- 



