Weight afcribed to Heat. 167 
very fine wires, two equal globes of glafs filled with mer- 
¢eury, and, fuffering them to remain in my room till they 
fhould have acquired the known temperature of the air im it, 
to have removed them afterward into the cold, and to have 
feen if they ftill remained in equilibrio under fuch difference 
ef temperature: but, confidering the obftinacy with which 
moifture adheres to the furface of glafs, and being afraid 
that fomehow or other, notwithflanding 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 
increafed ; and having found, by a former experiment, of 
which I have already had the honour of communicating an 
account to the Royal Society, that the gilt furfaces of metals 
do not attract moifture; inftead ale vlafs clobes filled with 
mercury, I made ufe of two equal folid globes of brafs, well 
gilt and burnifhed, which I fufpended to the arms of the 
balance by fine gold wires. 
Thefe globes, which weighed 4975 grains each, being 
wiped perfe€tly clean, and having acquired the temperature 
{61°) of my room, in which they were expofed more than 
twenty-four hours, were brought into the moft ferupulous 
equilibrium, and were then removed, attached to the arms 
of the balance, into a room in which the‘air was at the tem- 
perature of 26°, where they were left all night. 
The refult of this trial furnithed the mow fatisfactory 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. 
Having thus removed my doubts refpecting the accuracy 
of my balance, I now refumed my inveftigations relative to 
the augmentation of weight which fluids have been faid to 
acquire upon being congealed. 
In the experiments which I had made, I had, as I then 
imagined, guarded as much as poflible againft every fource 
of error and deception. The bottles being of the fame fize, 
neither any oecafional alteration in the preflure of the atma- 
fphere during the experiment, nor the neceflary and unavoid- 
able difference in the denfities of the air in the hot and in 
the cald rooms in which they were weighed, could affegét 
their 
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