DR T. THOMSON on Asbestus, Chlorite, and Talc. 387 

 Its constituents were found to be, 



Silica, . . ,,l>c . . 49.816 



Alumina, *:.'. 20.596 



Lime, 6.000 



Potash, ..... 6.800 



Protoxide of iron, . . 1 .500 



Water, ...... 5.000 



99.212 



with a trace of manganese. 



If we calculate the composition of agalmatolite from the pre- 

 ceding analysis, we obtain, 



atoms silica, 

 71 atoms alumina, 

 10 atoms lime, 



7 atoms potash, 



2 atoms protoxide of iron, 

 28 atoms water. 



We might therefore consider it as composed of, 



35 atoms sesquisilicate of alumina. 



5 atoms bisilicate of lime, 



3 atoms tersilicate of potash, 



1 atom silicate of iron, 

 14 atoms water. 



From the analysis of KLAPROTH, and JOHN and VAUQUELIN, 

 it is obvious that the lime and oxide of iron are not always found 

 in agalmatolite. They cannot therefore be essential ingredients. 

 If we leave them out, and consider the silica united with them 

 as in combination with the alumina, agalmatolite will be a com- 



VOL. XI. PART II. 3 C 



