148 EFFECTS of HEAT 
No. 9.—AN experiment was made with chalk, in a little 
tube; to this, one grain ef water was added, I had intended to 
work with 4 cwt. only ; but the barrel was no fooner placed, 
than an exudation of metal began at the muzzle, owing, doubt- 
lefS, to the elafticity of the water. I immediately increafed 
the preflure to 8.1 cwt. by removing the weight from the 
bucket, when the exudation inftantly ceafed. I continued the 
fire for three quarters of an hour, during which time no exu- 
dation happened; then all came out remarkably clean, with 
{carcely any contamination of metal. The lofs amounted to 
2.58 per cent. The fubftance was tolerably indurated, but had 
not acquired the character of a complete ftone. 
In thefe two laft experiments, the bore being fmall, a pyro- 
meter could not be admitted. 
On the 5th of July 1804, I made three very fatisfactory ex- 
periments of this kind, in a barrel with the large bore of 0.75 
of.an inch. 
No. 10.—was made with a comprefling force of only 3 cwt. 
A fmall eruption at the muzzle being obferved, water was 
thrown on the barrel : the pyrometer gave 21° : the chalk was 
in a firm ftate of limeftone. 
No. 11.—witnH 4 cwt. The barrel ftood without any erup- 
tion or exudation, till the heat rofe to 25°. There was a lofs 
of 3.6 per cent.: the refult was fuperior, in hardnefs and tranf- 
parency, to the laft, having fomewhat of a faline fracture. 
No. 12.—wira 5 cwt. The refult, with a lofs of 2.4 per 
cent., was of a quality fuperior to any of thofe lately obtained. 
THESE experiments appear to anfwer the end propofed, of af- 
certaining the leaft preflure, and loweft heat, in which lime- 
ftone can be formed. The refults, with various barrels of 
different fizes, agree tolerably, and tend to confirmeach other. 
The table fhews, when we compare numbers 1, 2, 8, Io, 11, 
12, That a preffure of 52 atmofpheres, or 1700 feet of fea, is 
' capable 
