35 6 Of the Propagation of Heat 



ment seems to indicate, namely, that there is no such 

 thing as an attraction of predilection between solids and 

 their solvents, and that all those motions which have 

 been attributed to the action of that supposed power 

 (as well as all other motions which take place in Fluids) 

 are the immediate effects of gravitation acting according 

 to immutable laws, and changes of specific gravity by Heat ; 

 yet there would still remain one great difficulty in ex- 

 plaining chemical solution. As all mechanical operations 

 require a certain time for their performance ; and as the 

 motion which is occasioned in a Fluid by a change of 



J D 



specific gravity in any individual particles of it begins as 

 soon as the change begins to take place, if there be no 

 attraction between the particles of solid bodies and the 

 particles of their menstrua ; as Heat is supposed to be 

 generated or absorbed, or to speak more properly 

 both generated and absorbed, in the contact of those 

 particles, and previous to the completion of their chem- 

 ical union, how does it happen that the particle of the 

 menstruum whose specific gravity is necessarily changed 

 by this change of temperature does not immediately quit 

 the solid, in consequence of this change, and before the 

 process of solution has had time to be completed? 



A consideration of the effects of the vis inertia of the 

 particle of the menstruum whose specific gravity is thus 

 changed, and also of the vis inertia of the rest of the 

 Fluid, and the resistance it must oppose to the motion 

 of its individual solitary particles, would furnish us with 

 arguments that might be employed with advantage in re- 

 moving this difficulty ; but I fancy that the result of the 

 experiment of which I shall presently give an account 

 will be more satisfactory than any reasoning, unsup- 

 ported by facts, that I could -offer on the subject. 



