216 Catalogue of Specimen* 



Along with No. 3. is a specimen (A 3.) of common yel- 

 low marble, bearing a strong resemblance to the artificial 

 stone. 



Nos. 8, 9, 10, 1 1, all formed from pieces of chalk exposed 

 Unbroken to heat and pressure. 



No. S. is remarkable for a shining grain and semi-trans- 

 parency. Nos. 9 and 10. show parallel planes like internal 

 stratification, which has often appeared in chalk in conse- 

 quence of the action of heat, though nothing of the kind 

 could be seen in the native mass. No. 11. very compact, 

 and of a yellow colour. Nos. 12 and 13. examples of weld- 

 ing, in which the pounded chalk has been incorporated with 

 a lump of chalk upon which it had been rammed, so that 

 their joining is hardly visible in the fracture. 



Nos. 14, 15, 16, showing the fusion of the carbonate 

 well advanced, with a considerable action on the porcelain 

 tube. 



In No. 15. the rod of chalk is half melted, and a yellow 

 substance produced by a mixture of the carbonate with the 

 porcelain. No. 16. is a lump of chalk in a state indicating- 

 softness, a piece of porcelain which lay in contact with it 

 having sunk a little into the substance of the carbonate. 



Nos. 17 and 18, and all the following numbers, being de- 

 licate, are inclosed in tubes of glass, and fixed with sealing- 

 wax on little cups of wood. 



No. 17, formed from pounded chalk, shows in one part 

 the most complete formation of spar, with its rhomboidal 

 fracture, I ever obtained. 



The carbonate, having lost some of its carbonic acid, had 

 crumbled so much in its essential parts by the action of the 

 air, that the crystallization was no longer visible; and I 

 had given up the specimen for lost, till some time in July 

 1804, when, employed in examining these results-, in order 

 to show them in the Royal Society of Edinburgh, a mass of 

 the carbonate broke in two and exhibited the fracture now 

 before us, nearly in as good a state as it was originally. I 

 immediately inclosed it in a glass tube, and sealed it with 

 wax, so that I have hopes of preserving it; and it still con- 

 tinues entire, though now sealed up for a year and a half. 

 2 No. IS, 



