Weight afcribed to Heat. 163 
all thofe precautions to avoid errors, which a knowledge of 
the various fources of them, and an earneft defire to deter~ 
mine a fa& which I conceived to be of importance to be 
known, could infpire: but though all my refearches tended 
to convince me, more and more, that a body acquires no ad~ 
ditional weight upon being heated, or rather, that heat has no 
effect whatever upon the weights of bodies, I have been fo 
fenfible of the delicacy of the 1 inquiry that I was for a long 
time afraid to form a decided opinion upon the fubject. 
Being much. ftruck with the experiments recorded in the 
Tranfactions of the Royal Society, Vol. LXXV. made by 
Dr. Fordyce, upon the weight faid to be acquired by water 
upon being frozen; and being poffefled of an excellent ba- 
lance, belonging to his moft Serene Highnefs the Ele¢tor 
Palatine Duke of Bavaria, early in the beginning, of the 
winter of the year 1787 (as foon as the cold was fufficiently 
intenfe for my purpofe) I fet about to repeat thofe experi-+ 
ments, in order to convince myfelf whether the very | extraor- 
dinary fa& related might be depended on; and with a view 
to removing, as far as was in my power, every fource of error 
and deception, I proceeded in the following manner :— 
Having provided a number of glafs bottles, of the form and 
fize of what in England is called a Florence flafk (blown as 
thin as poffible) and of the fame fhape and dimenfions, I 
chofe out from amongft them two, which, after ufing every 
method I could imagine of comparing them together, ap- 
peated to be fo much alike as hardly to be diftinguifhed. 
Into one of thefe bottles, which I {hall on AS put 
4107,86 grains troy of pure diftilled water, which filled it 
about half full; and into the other, B, I put an equal weight 
of weak fpirit of wine; and, fealing both the bottles her+ 
metically, and wafhing them and wiping them perfectly 
elean and dry on the outfide, I fufpended them to the arms 
of the balance, and placed the balance in a large roomy 
which for fome weeks had been regularly heated every: 
day by a German ftove, and in wliich the air was kept up 
to the temperature of 61° of Fahrenheit’s thermometer, with 
very little variation. Having fuffered the bottles, with their 
contents, to remain in this fituation till I conceived they 
¥-2 mutt 
