MODIFIED by COMPRESSION. 131 



VI. 



Experiments made in Platina, — with Spar, — with Shells,— and with 

 Carbonate of Lime of undoubted purity. 



Since I had the honour of laying before this Society a 

 fhort fketch of the foregoing experiments, on the 30th of Auguft 

 laft (1804), many chemifts and miner alogifls of eminence have 

 favoured me with fome obfervations on the fubject, and have 

 fuggefted doubts which I am anxious to remove. It has been 

 fuggefted, that the fulibility of the carbonates may have been 

 the confequence of a mixture of other fubftances, either ori- 

 ginally exifting in the natural carbonate, or added to it by 

 the contact of the porcelain tube. 



With regard to the firfl of thefe furmifes, I beg leave to 

 obferve, that, granting this caufe of fufion to have been the 

 real one, a material point, perhaps all that is ftri&ly necefla- 

 ry in order to maintain this part of the Hattonian Theory, was 

 neverthelefs gained. For, granting that our carbonates were 

 impure, and that their impurity rendered them fufible, ft ill 

 the fame is true of almoft every natural carbonate ; fo that 

 our experimenats were, in that refpect, conformable to nature. 

 And as to the other furmife, it has been fhewn, by com- 

 paring together a varied feries of experiments, that the mu- 

 tual action between the lime and the porcelain was oc- 

 cafioned entirely by the prefence of the carbonic acid, fince, 

 when it was abfent, no action of this kind took place. The 

 fufion of our carbonates cannot, therefore, be afcribed to the 

 porcelain. 



Being convinced, however, by many obfervations, that the 

 fufibility of the carbonate did not depend upon impurity, 



R 2 I 



