the Accompanying substances. 23 



5. The liquor of No. 4. was precipitated by muriate of am- alumina taken 

 monia, and afforded alumina : which, being warned and ignited, " p by P otani * 

 weighed 37,5 grains. 



I could alfo perceive a trace of manganefe. 

 The proportions therefore are, 



Silica ... 42,5 



Alumina - 37,5 



Lime ... 15^0 



Iron .... 3,0 

 Lofs, with a trace of manganefe - 2,0 



3 grs. iron re- 

 mained. 



Mur. amm. pre- 

 cipitated 37,5 

 alumina, 

 Manganefe, a 

 trace. 

 Comp. parte. 



100,0. 



By a fimilar treatment, the following fubftances, contained 

 in this matrix, afforded the under-mentioned refults. 



100,00. 

 This is the only Hone I have ever met with, that yielded 

 nothing but filica and alumina ; for the quantity of iron was fo 

 fmall as hardly to be taken into account. I have repeated this 

 analyfis three times, and have not found a difference of half a 

 grain. 



Thallite in Cryjlals, with a rough Surface. 



Silica 



Alumina 



Lime 



Iron 



Lofs 



of rough thallite; 



45 

 2S 

 15 

 11 

 1 



100. 



Thallite 





