168 an Inquiry concerning the 
their apparent weights; and their fhapes and their quantities 
of furface being the fame, and as they remained for fuch a 
confiderable length of time in the heat and cold to which 
they were expofed, I flattered myfelf that the quantities of. 
moifture remaining attached to their furfaces could not. be fo 
different as fenfibly to effect the refults of the experiments, 
But, in regard to this laft circumftance, F afterwards found 
reafon to conclude that my opinion was erroneous. 
Admitting the fact ftated by Dr. Fordyce, (and which my 
experiments had hitherto rather tended to corroborate thar 
to contradiét,) I could not conceive any other caufe for the 
augmentation of the apparent weight of water, upom its being 
frozen, than the lofs of fo great a proportion of its latent 
heat as that fluid is known to evolve when it congeals; and 
I concluded, that if the 18 of latent heat added to the weight 
of one body, it muft of neceffity produce the fame effect on 
another, and confequently, that the augmentation of the 
quantity of latent heat muft, in all bodies, and in all cafes, 
diminith their apparent weights. od 
To determine whether this is actually the cafe or not, I 
made the following experiment :— 
Having provided two bottles, as nearly alike as poffible, 
and im all refpects fimilar to thofe made ufe of in the exper 
riments above-mentioned, inte one of them I put 4012,46 
grains of water, and into the other an equal weight of mer- 
eury; and fealing them hermetically, and fufpending then 
to the arms of the balance, I fuffered them to acquire the 
temperature of my room, 61°; then, bringing them into a, 
perfect equilibrium with each other, I removed them into a 
room in which the air was at the temperature of 34°, where 
they remained twenty-four hours. But there was not the leat 
appearance of either of them acquiring or lofing any weight. 
Here it is very certain that the quantity of heat loft by the 
water muft have been very confiderably greater than that loft 
by the mercury, the fpeeific quantities of latent heat in water 
and in mereury having been determined to be to each other 
as 1000 to 333 but this difference in the quantities of heat 
jof, produced no fenGible difference on the weights of the 
-fiuids in- quefijon, > asl 
Tee Had 
