“ 
Weight afcribed to Heat. 71 
At the end of forty-eight hours (during which time the 
apparatus was left in this fituation) I entered the room, open- 
ing the door very gently for fear of difturbing the balance; 
when I had the pleafure to find the three thermometers, viz. 
that in the bottle A, which was now inclofed in a folid cake 
of ice, that in the bottle B, and that fufpended in the open 
air of the room, all ftanding at the fame point, 29° F., and 
the bottles A and B remaining in the moft perfect equilibrium. 
To affure myfelf that the play of the balance was free, I 
now approached it very gently, and caufed it to vibrate; and 
T had the fatisfaction to find, not only that it moved with 
the utmoft freedom, but alfo, when its vibration ceafed, that 
it refted precifely at the point from which it had fet out. 
I now removed the bottle B from the balance, and put the 
bottle C in its place; and I found that ¢dat likewife remained 
of the fame apparent weight as at the beginning of the expe: 
riment, being in the fame perfec equilibrium with the bot- 
tle A as at firft, 
I afterwards removed the whole apparattis into a warm 
room, and, caufing the ice in the bottle A to thaw, and fuf- 
fering the eee. bottles to remain till they and their contents 
had acquired the exact temperature of the furrounding air, I 
wiped them very clean, and, comparing them together, I 
found their weights remained unaltered. 
This experiment I afterwards repeated feveral times, and 
always with precifely the fame refult; the water, zm no in- 
fiance, appearing to gain or to lofe the leaft weight upon 
being frozen, or upon being thawed; neither were the rela- 
tive weights of the fluids in either of the other bottles in the 
leaft changed, by the various degrees of heat, and of cold, to 
which they were expofed. 
If the bottles were weighed at a time when their contents 
were not precifely of ihe fume temperature, they would fre- 
quently appear to have gained, or to have loft, fomething of 
their weights; but this doubtlefs arofe from the vertical cur- 
rents which they caufed in the atmofphere upon being heated 
or cooled in it; or to unequal quantities of moifture attached 
to the furfaces of the bottles; or to both thefe caufes ope- 
rating together, 
Zo As 
