the Weight ascribed to Heat. 



SUPPLEMENT. 



THE foregoing paper having been originally drawn 

 up for the purpose of being laid before 'the Royal 

 Society, my respect for that learned body induced me 

 to confine my observations to such points as I con- 

 ceived to be new ; and I took no notice whatever of a 

 considerable number of experiments which I had made 

 in the course of my investigations, because they were 

 very similar to experiments that had before been made 

 by other persons ; and because their results did not 

 appear to me to afford sufficient grounds to form any 

 decisive opinion respecting the matter in question. 

 There were, however, among my experiments, two or 

 three of which I shall now give an account, which will 

 probably be thought sufficiently interesting to deserve 

 being mentioned. 



Most of the experiments, from the results of which 

 philosophers had been induced to form their opinions 

 respecting the -ponderability of heat^ had been made by 

 weighing the same given body at different temperatures. 

 Thus, solid globes of metal cannon-balls, for instance 

 had frequently been weighed when cold, and then, be- 

 ing heated red-hot, had been again weighed at that high 

 temperature, and, from the apparent difference of the 

 weight of the ball when cold and when red-hot, conclu- 

 sions had been formed respecting the weight or levity of 

 heat. But had the numerous causes of error in these 

 most difficult experiments been less evident than they 

 are, yet the results of the experiments of this kind which 

 have hitherto been made by different persons have 



VOL. n. 



