the Weight ascribed to Heat. 7 



My first idea was, to suspend to the arms of the bal- 

 ance, by very fine wires, two equal globes of glass, filled 

 with mercury, and, suffering them to remain in my 

 room till they should have acquired the known tempera- 

 ture of the air in it, to have removed them afterward 

 into the cold, and to have seen if they still remained in 

 equilibrio under such difference of temperature ; but, 

 considering the obstinacy with which moisture adheres 

 to the surface of glass, and being afraid that somehow 

 or other, notwithstanding all my precautions, one of the 

 globes might acquire or retain more of it than the other, 

 and that by that means its apparent weight might be 

 increased ; and having found by a former experiment, 

 of which an account is given in one of the preceding 

 papers (that on the Moisture absorbed from the Atmos- 

 phere by various Substances.), that the gilt surfaces of 

 metals do not attract moisture (see Vol. I. p. 232), 

 instead of the glass globes filled with mercury, I made 

 use of two equal solid globes of brass, well gilt and 

 burnished, which I suspended to the arms of the bal- 

 ance by fine gold wires. 



These globes, which weighed 4975 grains each, being 

 wiped perfectly clean, and having acquired the tempera- 

 ture (61) of my room, in which they were exposed 

 more than twenty-four hours, were brought into the 

 most scrupulous equilibrium, and were then removed, 

 attached to the arms of the balance, into a room in 

 which the air was at the temperature of 26, where they 

 were left all night. 



The result of this trial furnished the most satisfac- 

 tory proof of the accuracy of the balance ; for, upon 

 entering the room, I found the equilibrium as perfect as 

 at the beginning of the experiment. 



