on some of the leading doctrines of caloric, &c. 387 
mined it more nearly from 900° to 950° ; and Lavoisier and 
La Place have made it 1000°. 
It is evident that whenever the water, into which the latent 
heat is evolved by condensation of the vapour, becomes much 
hotter than the surrounding air, it will be impossible to 
ascertain how much of the caioric is dissipated ; and conse- 
quently, the true quantity contained in the vapour must re- 
main uncertain. 
The sources of error in operating with the calorimeter of 
Lavoisier and La Place, were first pointed out by Mr. 
Wedgwood, and have been . since commented on by Dr. 
Thomson, and other good systematists. It is said to be 
difficult to obtain precisely uniform quantities of liquified ice 
in the repetition of the same experiments, with that celebrated 
apparatus. 
From the smallness of the retort in my mode of proceed- 
ing, the shortness of the neck, and its thorough insertion into 
the globe, we prevent condensation by the air in transitu ; 
while the surface of the globe and the mass of water being 
great, relative to the quantity of vapour employed, the heat 
is entirely transferred to the refrigeratory, where it is allowed 
to remain, without apparent diminution, for a few minutes. 
In numerous repetitions of the same experiment, the accord- 
ances were excellent. The following table contains the mean 
results. The water in the basin weighed in each case 
$234,0 gr. The globe w^as held steadily in the centre of the 
water by a slender ring fixed round its neck. The distilla- 
tion was rapidly performed, so that all the condensation took 
place in the globe. 
SE 
MDCCCXVIII. 
