Effects of Heat modified ly Compression. 307 



the little tube, which after its introduction had been wiped 

 smooth, were a set of white crystals, with shining facettes, 

 large enough to be distinguished by the naked eye, and 

 seeming to rise out of the mass of carbonate. I likewise 

 observed that the solid mass on which these crystals stood 

 was uncommonly transparent. 



In these four experiments the bulk of the included air was 

 successivelv diminished, and by that means its elasticity in- 

 creased. The consequence was, that in the first experiment, 

 where that elasticity was the least, the carbonic acid was 

 allowed to separate from the lime, in an early stage of the 

 rising heat, lower than the fusing point of the carbonate, 

 and complete internal calcination was effected. In the se- 

 cond experiment, the elastic force being much greater, cal- 

 cination was prevented, till the heat rose so high as to occa- 

 sion the entire fusion of the carbonate, and its action on the 

 tube, before the carbonic acid was set at liberty by the failure 

 of the barrel. In the third experiment, with still greater 

 elastic force, the carbonate was partly constrained, and its 

 fusion accomplished, in a heat between 41° and 15°. In 

 the last experiment, where the force was strongest of all, 

 the carbonate was almost completely protected from decom- 

 position by heat, in consequence of which it crystallized 

 and acted on the tube in a temperature between 25° and 16°. 

 On the other hand, the efficacy of the carbonic acid as a 

 flux on the lime, and in enabling the carbonate to act as a 

 flux on other bodies, was clearly evinced ; since the first ex- 

 periment proved, that quicklime, by itself, could neither he 

 melted, nor act upon porcelain, even in the violent heat of 

 79"; whereas, in the last experiment, where the carbonic acid 

 was retained, both of these effects took place in a very low' 

 temperature. 



[To be contiiiucd.] 



U 2 LVI. 01- 



