593 On the Affinities of 



all over with silvery shining globules of iron, which I esti- 

 mated to weigh nearly 1^ gr:T-in, or 3 per cent. 



Experiment X. 



I took a piece of the same chalk, well dried, and roasted 

 it in a moderate heat for five hours. 



When raw it weighed - - 395 grs. 



After roasting it weighed - 236 



Lpst of water and carbonic acid, — — 

 ."equal to 40' 25 per cent. - 159 



Sixty grains of this roasted chalk was fused in a heat of 

 166° of Wedge wood, and a very perfect dense glass ob- 

 tained. It possessed all the transparency of No. VI, which 

 was the same substance fused per se in a raw state, but in 

 place of an ambcr.crecn it approached more to the colour 

 and lustre of the emerald. It differed from No. IV, wherein 

 dcacified spar was fused, very materially, most probably 

 owing to a greater qvuuitity of iron in mixture in the state 

 of oxide. 



Experiment XI. 



Koasted chalk - - - 50 grs. 



Lamp carbon l-5Uih, or - 1 



A very perfect glass was obtained of a lead blue greenish 

 colour, n)ost evidently of the same species of glass with 

 No. Ill, V, and IX, though lighter and more transparent, 

 'jlie. charcoal had disappeared : no metallic globules were 

 visible, although the stale and calour of the glass indicated 

 immediate precipitation.. : , ' 



Experiment XII. 



Kdasicd chalk - - - 50 grs. 



Lanip carbon l-20th, or - 2-i 



A very dense glass "whs obtained, which in point of colour 

 was the same as No. Ill, V, and IX. A large grain of 

 charcoal remained uniakcji up upon the surface of tlie glass. 

 A number of globules .of iron were revived, which I esti- 

 jjniUed at 2 or 2^ g;rains, several of the largest of which were 

 covered with carburet of iron. 



Experiment XIII. 

 Roa-tdC chalk - - - 50 grs. 

 Lamp eavbori I-33d, or - U 



'I his mixture was pnkluctive of a very beautiful glass. 

 The colour light lead b!nc, faintly marked with green, of 

 the same class with N|);'ill, V, IX, XI, and XII, There 

 ronairied untaken up,nearly l-Cth of a grain of charcoal. 

 '■'•- ■'■■' , ' A very 



