different Earths for Carbon. 291 



number of globules of iron revived amounted to seventeen, 

 and which I estimated to be equal to half a grain. 



Experiment VI — with Chalk. 



Fifty grains of white very well dried chalk was intro- 

 duced per se, and fused in a heat of 163° of Wedgewood. 

 A beautiful amber green coloured glass was obtained, pos- 

 sessed of great depth of transparency. When cold, the 

 bottom of the crucible and the smallest speck were visible 

 through the thickness of glass, which was more than a 

 quarter of an inch in the middle. Compared with No. I, 

 it possessed a darker tinge of green. 



Experiment VII. 



Raw chalk finely pounded - 50 grs. 

 Lamp carbon l-50th, or - 1 



There resulted from the fusion of this mixture a dark 

 green primrose coloured glass, possessing some tints of the 

 topaz. Its transparency was not in the least impaired by 

 the union of the carbon, the whole of which had disap- 

 peared. 



Experimeni VIII. 



Raw chalk pounded - - 50 grs. 



Lamp carbon l-20th, or - 2i 



I obtained from the fusion of this mixture, at a heat not 

 exceeding 159° of Wedgewood, a very perfect glass of a 

 dark fiery amber colour, possessed of a greater degree of 

 lustre and effect than any of the former products. The 

 charcoal had disappeared, and the surface of the glass re- 

 mained free from any appearance of metal. Compared with 

 No. II, the results seemed altogether similar. The present 

 seemed, although the greatest mass, to have the advantage 

 in point of transparency. 



Eocperiment IX. 

 Raw chalk pounded - - 50 grs. 



I^amp carbon l-]5th, or - 4 



A perfect fusion was here obtained, as in the former ex- 

 periments. The glass possessed a dark blueish lead colour, 

 transparent in their fragments, but dull and opaque in the 

 mass. It exactly resembled the earthy parts of an iron ore 

 when separated from their metallic contents by fusion in a 

 black lead crucible, when the richest carburatcd iron is pro- 

 duced. There remained untaken up half a grain of charcoal, 

 mixed with some particles of the calcareous earth of a pure 

 white colour. The surface of the glass was nearly covered 

 T 2 all 



