390 On the Affinities of 



Expaiment I. 



T took a very transparent crystal of double refracting spar 

 and exposed it to a heat of 166° of Wedgevvood. It was 

 found tused into a very perfect glass of a rich green amber 

 colour, considerably transparent. 



Experiment II. 



A fr^ment of the same crystal, weighing 20 grains, 

 was introduced along with one grain of lamp carbon, and a 

 p&rfcct fusion was obtained. The charcoal had entirely dis- 

 appeared, and the colour of the glass was changed to a deep 

 fiery amber colour, less transparent than the result in Exp. I. 



Experiment III. 



The same spar, weighing 20 grains, was mixed with 

 l-j grain of lamp carbon, and introduced into the furnace. 

 The fusion was completed in fifteen minutes. I found a 

 perfect glass of a cloudy milky lead colour. A minute por- 

 tion of the charcoal remained, and there appeared twenty- 

 three globules of iron upon the surface of the glass, many 

 of which were so small as not to be visible by the naked 

 eye ; estimated at half a grain, or 21 per cent. 



Experiment IV. 

 I took another crystal of the same double refracting spar, 

 and distilled it in a gradually increasing heat for five hours. 

 I found it had lost its transparency, but had preserved its 

 figure and form in a most perfect manner. The original 

 laminae were entire, and alternated in various shades of co- 

 lour, several of which seemed derived from iron. 



The crystal at first weighed - - 69 grs. 



After distillation - - _ 39 



Lost of water and carbonic acid, equal to ■ 

 43*48 per cent. - - - 30 



Twenty grains of calcareous matter thus obtained were 

 fused per se, and a very fine portion of glass was the result. 

 The colour was a water)' blueish glass faintly marked with 

 grecn_, not very transparent. 



Experiment Y. 



Double refracting spar deacified 20 grains, povmded and 

 mixed v.-ith one grain of lamp carbon, was fused into a glasS' 

 similar to No. Ill, but more inclined to a lead colour, and 

 possessing less transparency. About l-6th of a grain of 

 carbon remained upon the surface of the glass, and the 

 2 number 



