the Weight ascribed to Heat. 21 



An Account of an Experiment made with a Bullet of Fine Gold. 



Munich, i^d April, 1785. Weather cloudy, with 

 intervals of sunshine ; thermometer in my room at 

 65 F ; barometer at 26 inches 4 lines. 



A small bullet of fine gold, equal in value to 10 Ger- 

 man ducats, which I procured from the master of the 

 mint, being weighed in the open air of my room, was 

 found to weigh 477-}!! g ra i ns - 



The small open china cup, in which the bullet was 

 weighed, was exactly counterbalanced by a weight = 

 440||| grains. 



At 10 h. 5 m. A. M. the bullet, heated to a clear red 

 heat approaching to whiteness, and weighed in the cup, 

 open to the air, the bullet and the cup together were 

 found to have lost of their weight ^ff of a grain. 



Removing the bullet immediately, I found that the 

 cup, or rather the cup and the scale in which it was 

 placed, together had lost in weight ^|| parts of a grain. 



Consequently, the bullet must have lost of its weight 

 by being heated red-hot ; or it appeared to be lighter 

 when red-hot than when cold by ^f g- parts of a grain, 

 or ^ oTf -9 part of its whole weight. 



. Upon repeating the experiment I had nearly the 

 same result ; but upon varying it, by covering the 

 heated bullet in the scale, in different ways, I found 

 such variations in the results as convinced me that the 

 apparent diminution of weight above mentioned might 

 easily have arisen from currents in the atmosphere, 

 and consequently that no dependence can be placed 

 in experiments of that kind for deciding the fact rela- 

 tive to the weights of heated bodies, or the ponder- 

 ability of heat. 



