Effects of Heat modified ly Compression, 26 



when a fine powder is used in acting upon each other, and 

 I did not choose to run any risk of contamination by re- 

 ducing the substance to a finer powder. Whatever be the 

 cause, it is certain, that in many experiments in which the 

 chalk was changed to marble, this substance remained in a 

 loose and brittle state, though consisting generally or' clear 

 and shining particles. I at last, however, succeeded in ob- 

 taining some very good results with this carbonate. 



In an experiment made with it on the 18th of June, in a 

 strong heat, 1 obtained a very firm mass with a saline frac- 

 ture, moulded in several places on the platina, which was 

 now used in the cylindrical form. On the 23d, in a similar 

 experiment, the barrel failed, and the subject of experiment 

 was found in an entire state of froth, proving its former 

 iluidity. 



On the 25lh, in a similar experiment, a heat of 64° was 

 applied without any water within the barrel. The platina 

 tube (having been contaminated in a former experiment with 

 same fusible metal) melted, and the carbonate, retaining its 

 'cylindrical shape, had fallen through it, so as to touch the 

 piece of porcelain which had been placed next to the platina 

 tube. At the point of contact the two had run together, as 

 a hot iron runs when touched by sulphur. The carbonate 

 itself was very transparent, resembling a piece of snow in 

 the act of melting. 



On the 26th of June I made an experiment with this 

 carbonate, which afforded a beautiful result. One grain of 

 water was introduced with great care; yet there was a loss 

 of 6-5 per cent., and the result has fallen to decay. The 

 pyrometer indicated 4 3°. On the outside of the platina cy- 

 linder, and on one of the lids, were seen a set of globules 

 like pearls, as once before obtained, denoting perfect fusion. 

 When the upper lid was removed, the substance was found 

 to have sunk almost out of sight, and had assumed a form 

 not easily described. (I have endeavoured to represent it in 

 fig. 31. by an ideal section of the platina tube and its con- 

 tents, made through the axis of the cylinder.) The powder, 

 first shrinking upon itself in the act of agglutination, had 

 formed a cylindrical rod, a remnant of which (ale) stood 



up 



