272 Dr T. THOMSON'S Account of the Constituents of Minerals. 



Mr NUTALL was good enough to send me several specimens 

 of it, one of which was analysed at my request by Mr THOMAS 

 STEEL. The result of two successive analyses were as follows : 



Silica, 41.256 



Magnesia, .... 41.720 



Alumina, 1.000 



Peroxide of Iron, . . 0.400 



Water, ..... 17.680 



102.056 



It is therefore a hydrous sesquisilicate of magnesia, or a va- 

 riety of the precious serpentine, or picrolite of HAUSMANN. 



I have already extended this paper to a greater length than 

 I intended. Yet I have been able to introduce but a very small 

 number of the many analyses made by my practical pupils during 

 the course of the two last years ; and I have omitted altogether a 

 pretty numerous set of analyses made by myself during that time. 

 These I may perhaps lay before the public at some future oppor- 

 tunity. Meanwhile it is highly requisite to attend to the adage 

 of TERENCE, " Ne quid nimis" 



