142 EFFECTS of HEAT 
firft tolerable compreflion accomplithed by a determinate force. 
The pyrometer indicated 22°. 
Tuis experiment wes repeated the tito day, when a ftill 
fmaller quantity of metal efcaped at the muzzle ; but the bar- 
rel had given way below, in the manner of thofe that have 
yielded for want of fufficient air. Even this refult was fatis- 
factory, by fhewing that a mechanical power, capable of for- 
cing fome of the barrels, could now be commanded. The car- 
bonate in the little tube had loft 20 per cent.; but part ont was 
in a hard and firm ftate, effervefcing to the laft. 
No. 2.—On the 21ft June, I made an experiment with ano- 
ther barrel, with the fame circumftances. I had left an empty 
{pace in the large tube, and had. intended to introduce its 
muzzle downwards, meaning that {pace to.anfwer as an air- 
tube ; but it was inverted by miftake, and the tube entering 
with its muzzle upwards, the empty {pace had of courfe filled 
with metal, and thus the experiment was made without any 
included air. There was no pyrometer ufed; but the heat was 
guefled to be about 25° where the fubject of experiment 
lay. The barrel, when opened, was found full of metal, 
and the cradle being laid flat.on the table, a confiderable 
quantity of metal ran from it, which had undoubtedly 
been lodged in the vacuity of the large tube. When cold, I 
found that vacuity {till empty, with a plating of metal. 
The tube was very clean to appearance, and, when fhaken, 
jts contents were heard to rattle. Above the littie tube, 
and the cylinder of chalk, I had put fome borax and fand, 
with a little pure borax in the middle, and chalk over it. 
The metal had not penetrated beyond the borax and fand,. by 
a good fortune peculiar to this experiment; the intrufion of 
metal in this mode of execution, being extremely troublefome. 
The button of chalk, was found in a ftate of clean white car- 
bonate, and pretty hard, but without tranfparency. The little 
tube | 
