10 OBJECTIONS ANSWERED. 



proved by the experiments of Berthollet, Biot, 

 and Pictet, that when pieces of gold, silver, and 

 copper of the same size and shape, are suddenly 

 and forcibly struck, as when stamped in the pro- 

 cess of coining, they were condensed, and caloric 

 evolved, but more by the first than second blow ; 

 whereas after the third blow, when they had 

 arrived at the limit of condensation, there was no 

 perceptible increase of temperature. (Thomson 

 on Heat and Electricity, p. 339.) 



In accordance with these facts, it is well known 

 that the smith often kindles his furnace by ham- 

 mering a piece of iron until it becomes red hot, 

 without any material loss of metallic dust or 

 scales ; and that after he has reduced it to the 

 limit of condensation, it becomes cold under the 

 hammer. It is therefore evident, that caloric is 

 not generated de novo, by the friction of rubbing 

 dry sticks of wood against each other, the pres- 

 sure of wire drawing, and by rubbing the hands 

 together ; but that it is merely forced out of the 

 pores of bodies, in the same way that water is 

 disengaged from the pores of a sponge by pres- 

 sure. And it will be proved hereafter, that the 

 caloric which is disengaged by rubbing the 

 hands together briskly, is resupplied by the 

 rapidly circulating blood, which obtains it by 

 respiration. 



Should it be urged that caloric is disengaged by 

 rubbing two pieces of ice together in the vacuum 



