n8 EFFECT'S 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 its 

 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. 



The 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 6o°. 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 hilling. 

 The carbonates were entirely calcined. The barrel had yield- 

 ed, but had refilled well at firft j for, the contents of the little 

 tube were found in a complete flate of froth, and running 

 with the porcelain. 



The third experiment was made on the 30th of April, in 

 another nmilar 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. 



The fourth experiment was made on the 2d of May, like 

 the reft in all refpe&s, with a ftill fmaller air-tube, of 0.0318, 

 being lefs than one-thirtieth of a cubic inch. The upper py- 

 rometer 



