118 EFFECGTS-of HEAT 
no rednefs when thrown into it. - Thefe fads clearly prove, 
that the calcination of the contents of the fmall tube had been 
internal, owing to the violent heat which had feparated as 
acid from the moft heated part of the carbonate, according 
to the theory already ftated. The foundnefs of the barrel’ was ~ 
proved by the complete ftate of thofe carbonates which lay 
in lefs heated parts. The air-tube in this experiment had a 
capacity of 0.29, nearly one-third of a cubic inch. : 
Tue fecond of thefe experiments was made on the 29th of © 
April, in the fame barrel with the laft, after it had afford- 
ed fome good refults. The air-tube was reduced to one- 
third of its former bulk, that is, to one-tenth of a cubic inch. 
The heat rofe to 60°. The barrel was covered externally 
with a black fpongy fubftance, the conftant indication of fai- 
lure, and a fmall drop of white metal made its appearance. 
The cradle was removed without any explofion or hifling. 
The carbonates were entirely calcined. The barrel had yield- 
ed, but had refifted well at firft; for, the contents of the little 
tube were found in a complete ftate of froth, and running 
with the porcelain. 
Tue third experiment was made on the 30th of pil; in 
another fimilar barrel. Every circumftance was the fame as 
in the two laft experiments, only that the air-tube was now 
reduced to half its laft bulk, that is, to one-twentieth of a cu- 
bic inch. A pyrometer was placed at each end of the large 
tube. The uppermoft gave 41°, the other only 15°. The~ 
contents of the inner tube had loft 16 per cent., and were redu- 
ced to a moft beautiful ftate of froth, not very much injured 
by the internal ‘calcination, and indicating a thinner ftate of 
fufion than had appeared. — 
Tue fourth experiment was made’on the 2d of May, like 
the reft in all refpects, with a ftill fmaller air-tube, of 0.0318, 
being lefs than one-thirtieth of a cubic inch. The upper py- 
rometer 
