Effects of Heat modified by Compression. 21 



not fit to retain a thin liquid ; but, in most cases, that cir- 

 cumstance was of no consequence ; and I foresaw that the 

 carbonates could not thus escape without proving the main 

 point under consideration, namely, their fusion. 



The rest of the apparatus was arranged in all respects as 

 formerlv described, the same precautions being taken to de- 

 fend the platina vessel as had been used with the inner tubes 

 of porcelain. 



In this manner I have made a number of experiments 

 during this spring and summer, the result of which is highly 

 satisfactory. They prove, in the first place, the proprietv 

 of the observations which led to this trial, bv showing, that 

 the pure carbonate, thus defended from any contamination, 

 is decidedly more refractory than chalk ; since, in many ex- 

 periments, the chalk has been reduced to a state of marble, 

 while the pure carbonate, confined in the platina vessel, has 

 been but very feebly acted upon, having only acquired the 

 induration of a sandstone. 



In other experiments, however, I have been more suc- 

 cessful, having obtained some results, worthy, I think, of 

 the attention of this society, and which I shall now submit 

 to their inspection. The specimens are all inclosed, for 

 safety, in glass tubes, and supported on little stands of wax 

 (fig. 31, 32, 33). The specimens have,- in general, been 

 removed from the cup or tube of platina in which they were 

 formed, these devices having the advantage of Securing both 

 the vessel and its contents, by enabling us to unwrap the 

 tolds without violence ; whereas in a solid cup or tube it 

 would have been difficult, after the experiment, to avoid the 

 destruction cither of the vessel or its contents, or both. 



April 16, 1805. — An experiment \vas made with pure cal- 

 careous spar from St. Gothard, remarkably transparent, and 

 having a strong double refraction. A temperature of 40° 

 was applied j but, owing to some accident, the weight was 

 not known. The conical cup came out clean and entire, 

 filled not quite to the brim with a yellowish gray substance, 

 having a shining surface, with longitudinal streaks, as we. 

 sometimes see on glass. This surface was here and there 

 interrupted by little white tufts or protuberances disposed 

 B 3 irregularis 



