BENJAMIN THOMPSON, COUNT RUMFORD 35 



these radiations, it seems reasonable to conclude that their elon- 

 gations would become less, and consequently that the volume of 

 the body would be contracted; but if the motions of these particles 

 were increased, we might conclude, a priori, that the volume of 

 the body would be expanded. 



"We have not sufficient data to enable us to form distinct ideas 

 of the nature of the change which takes place when a solid body is 

 melted; but as fusion is occasioned by heat, that is to say, by an 

 augmentation (from without) of that action which occasions ex- 

 pansion, if expansion be occasioned by an increase of the motions 

 of the constituent particles of the body, it is, no doubt, a certain 

 additional increase of those motions which causes the form of the 

 body to be changed, and from a solid to become a fluid substance. 



"As long as the constituent particles of a solid body which are 

 at the surface of that body do not, in their motions, pass by each 

 other, the body must necessarily retain its form or shape, however 

 rapid those motions or vibrations may be; but as soon as the mo- 

 tion of these particles is so augmented that they can no longer be 

 restrained or retained within these limits, the regular distribution 

 of the particles which they required in crystallization is gradually 

 destroyed, and the particles so detached from the solid mass form 

 new and independent systems, and become a liquid substance. 



"Whatever may be the figures of the orbits which the particles 

 of a liquid describe, the mean distances of those particles from 

 each other remain nearly the same as when they constituted a 

 solid, as appears by the small change of specific gravity which 

 takes place when a solid is melted and becomes a liquid; and on 

 a supposition that their motions are regulated by the same laws 

 which regulate the solar system, it is evident that the additional 

 motion they must necessarily acquire, in order to their taking the 

 fluid form, cannot be lost, but must continue to reside in the liquid, 

 and must again make its appearance when the liquid changes its 

 form and becomes a solid. 



"It is well known that a certain quantity of heat is required to 

 melt a solid, which quantity disappears or remains latent in the 

 liquid produced in that process, and that the same quantity of 

 heat reappears when this liquid is congealed and becomes a solid 

 body." 



From this disquisition on molecular physics he at once draws 

 the practical conclusion that a saucepan ought to be smoked on 

 the bottom and bright on the sides in order to absorb and retain 

 the greatest amount of heat. Stoves ought not be polished, but 



