6 
Ce ee ee eee ee 
‘ 
Weight afcribed to Heat. 163 
had been too hafty in my communication. Sir Charles, ix 
his anfwer to my letter, expreffed doubts refpecting the fact; 
but, befere his letter had reached me, I had learned,. from 
my own experience, how very dangerous it is, in philofo- 
phical inveftigations, to draw conclufions from fimgle expe- 
riments. 
- Having removed the balance, with the two bottles attached ° 
to it, from the cold into the warm reom, (which ftill remained 
at the temperature of 61°,) the ice in the bottle A gradually 
thawed; and being at length totally reduced to water, and 
this water having acquired the temperature of the furround- 
ing air, the two bottles, after being wiped perfectly clean and 
dry, were found to weigh as at the beginning of the experi- 
ment before the water was frozen. 
This experiment, being repeated, gave nearly the fame re- 
fult, the water appearing, when frozen, to be heavier than 
in its fluid ftate; but fome irregularity in the manner in 
which the water loft the additional weight which it had ap- 
peared to acquire upon being frozen, when it was afterwards 
thawed, as alfo a fenfible difference in the quantities of 
weight apparently acquired in the different experiments, led 
me to fufpe& that the experiment could not be depended or 
for deciding the fact in queition: I therefore fet about to 
repeat it, with fome variations and improvements :—but, be- 
fore I give an account of my further inveftigations relative to 
this fubje&t, it may not be amifs to mention the method 1 
purfued for difcovering whether the appearances mentioned 
in the foregoing experiments might not arife from the im- 
perfections of my balance; and it may likewife be proper to 
give an account, in this place, of an intermediate experiment 
which I made, with a view to difcover, by a fhorter route, 
and in a manner lefs exceptionable than that above-men- 
tioned, whether ‘bodies actually lofe, or acquire, any weiglit, 
upon acquiring an additional quantity of latent heat. 
My fufpicions refpeéting the accuracy of the balance arofe 
from a knowledge (which I acquired from the maker of it} 
of the manner in which it was conftructed. 
The three principal points of the balance having been de- 
termined, as nearly as poffible, by meafurement, the axes of 
‘ 7 | motion 
