the Weight ascribed to Heat. 187 
water, must have been very considerably greater than that lost 
by the mercury ; the specific quantities of latent heat in water 
and in mercury, having been determined to be to each other as 
1000 to 33; but this difference in the quantities of heat lost, 
produced no sensible difference on the weights of the fluids in 
question. 
Had any difference of weight really existed, had it been no 
more than one millionth part of the weight of either of the fluids, 
I should certainly have discovered it ; — and, had it amounted to 
so much as 7 o bVoo P art t ^ iat weight, I should have been able 
to have measured it; so sensible, and so very accurate, is the 
balance which I used in these experiments. 
I was now much confirmed in my suspicions, that the appa- 
rent augmentation of the weight of the water upon its being 
frozen, in the experiments before related, arose from some acci- 
dental cause ; but I was not able to conceive what that cause 
could possibly be, — unless it were, either a greater quantity of 
moisture attached to the external surface of the bottle which 
contained the water, than to the surface of that containing the 
spirits of wine, — or some vertical current or currents of air, 
caused by the bottles or one of them not being exactly of the 
temperature of the surrounding atmosphere. 
Though I had foreseen, and, as I thought, guarded sufficiently 
against, these accidents, — by making use of bottles of the same 
size and form, — and which were blown of the same kind of glass, 
— and at the same time, — and by suffering the bottles, in the expe- 
riments, to remain for so considerable a length of time exposed to 
the different degrees of heat and of cold, which alternately they 
were made to acquire ; yet, as I did not know the relative con- 
ducting powers of ice and of spirit of wine with respect to 
