different Earths for Carlon. 139 



ders it highly presumable that the affinity is not excited in 

 any degree of heat short of fusion. 



VII. 50 grains of roasted quartz, pulverized, 



5 ditto pure lime. 

 These were exposed, in a Cornwall clay crucible, to ] 67°- 

 The result of this was a semi-vitrified mass, granulated, 

 pure in colour, and very hard. The angles cut glass with 

 considerable facility. 



VIII. 50 grains of roasted quartz, 



10 ditto pure lime, were softened into a white 

 mass of porcelain, possessing a slight tint of azure. 



IX. 50 grains of roasted quartz, 



15 ditto pure lime, were melted into a whitish 

 mass covered with some very perfect glass. The fracture 

 was dense throughout, though not homogeneous. 



X. 50 grains of roasted quartz, 

 15 ditto pure lime, 



1 ditto lamp black, formed a solid mass of glass 

 of a lead-blue colour. The carbonaceous matter had disap- 

 peared. 



XI. 50 grains of roasted quartz, 

 15 ditto pure lime, 



2 ditto lamp black. 

 This mixture fused, and formed a very black glass consi- 

 derably spongy. The charcoal had, as in former experi- 

 ments, disappeared. In this experiment, the interior of the 

 crucible of Cornwall clay had received the usual glaze ob- 

 served in experiments where the quantity of carbon made 

 use of approaches nearly to that which the mixture is ca- 

 pable of taking up. 



XII. 50 grains of roasted quartz, 

 15 ditto pure lime, 



3 ditto lamp black. 

 This mixture was fused into a honey-combed mass of dark- 

 coloured glass possessed of neither beauty nor transparency. 

 A portion of the lamp black remained in its original state, 

 partly enveloped in the mass and partly upon the surface. It 

 was found to amount to nearly half a grain. The quan- 

 tity, therefore, taken up by the quartz in this experiment, 

 supposing the pure lime remained neutral, is exactly equal 

 to l -20th 3 and, by the combination of this proportion 

 of carbon, the pure white porcelain, produced in Experi- 

 ments VI IF and IX, is changed into a honey-combed mass 

 of black glass. 



XIII. Fifty grains of pure silex were introduced into a 

 Cornwall clay crucible, and exposed to a heat of 1 70° of 



L 4 Wedgwood, 



