DR T. THOMSON on Asbesfus, Chlorite, and Talc, 379 



The constituents of these crystals were found to be as fol- 

 lows : 





Silica, "./;,._/.;,, 29.364 



Alumina, .' V ' ', '', .' / . 1 7.808 



Lime, . . , . > 3.092 



Magnesia, ". . . . 12.144 



Protoxide of iron, . . 26.016 



Water, ."'.'' . . . 11.200 



99.624 



If we allow a little of the magnesia in this mineral to be re- 

 placed by lime, we have its atomic constituents as follows : 



f * J . '-* . 



5 atoms silica, 



2 atoms magnesia with lime, /; 



2f atoms alumina, 



2 atoms protoxide of iron, 



2^ atoms water. , 



The silica and magnesia exist in the same proportions as in 

 talc. But more than half the weight of the mineral consists of 

 alumina and protoxide of iron and water. The probability is, that 

 these crystals consist essentially of talc ; but so much contami- 

 nated with foreign matter as greatly to disguise the characters 

 of the mineral. 



. . . .5. Indurated Talc. 



The specimen of indurated talc which I selected for analysis 

 was from Sweden, but I do not know the locality. 

 Its colour was light bluish-green. 



VOL. XI. PART II. 3 B 



