Effects of Heat modified by Compression. 1.9 



to pieces ; but I found a lump of chalk, then in a state of 

 white marble, welded to the compound ; which last, in its 

 fracture, showed that irregular black colour, interspersed 

 roughly through a crystalline mass, that belongs to the al- 

 pine marbles, particularly to the kind called at Rome Cipol- 

 llne. It was very hard and firm ; I think unusually so. It 

 effervesced constantly to the last atom in diluted nitric acid, 

 but much more sluggishly than the marble made of pure 

 chalk. A cloudiness appeared pervading all the liquid. 

 When the effervescence was over, a series of bubbles con- 

 tinued during the whole day in the acid, without any dis- 

 position to burst, or rise to the surface. After standing all 

 next day and night, they maintained their station ; and the 

 solution, being stirred, was found to be entirely agglutinated 

 into a transparent jelly, breaking with sharp angles. This 

 experiment affords a direct and positive proof of a chemical 

 union having taken place between the carbonate and silex. 



VI. Experiments made in Platina, with Spar, with Sheik, 

 and with Carbonate of Lime of undoubted Purity. 



Since I had the honour of laying before this society a 

 short sketch of the foregoing experiments, on the ,30th of 

 August last (1804), many chemists and mineralogists of 

 eminence have favoured me with some observations on the 

 subject, and have suggested doubts which I am anxious to 

 remove. It has been suggested, that the fusibility of the 

 carbonates may have been the consequence of a mixture of 

 other substances, either originally existing in the natural 

 carbonate, or added to it by the contact of the porcelain 

 tube. 



With regard to the first of these surmises, I beg leave to 

 observe, that, granting this cause of fusion to have been the 

 real one, a material point, perhaps all that is strictly ne- 

 cessary in order to maintain this part of the Huttonian The- 

 ory, was nevertheless gained. For, granting that our car- 

 bonates were impure, and that their impurity rendered them 

 fusible, still the same is true of almost every natural car- 

 bonate; so that our experiments were, in that respect, con- 

 formable to nature And as to the other surmise, it his 

 JB 2 been 



