13G Dr. Berger on the physical Structure 



distinct beds in primitive mountains, included in rocks of serpentine 

 with which it is closely connected, but he does not give any ex- 

 ample.* 



Of all the rocks allied to the serpentine formation, steatite is that, 

 without doubt, which approaches nearest to it in chemical composition. 

 The only analyses of these two rocks which I know, are, that of ser- 

 pentine by Kirwan, and of the soap-rock of Cornwall by Klaproth, 

 v/ho calls it seifenstein. The coincidence of these two able chemists 

 in the proportions of the component parts of these substances, ren- 

 ders the idea I had formed, relative to their common origin, more 

 probable. I subjoin a comparative statement of the results of these 

 two analyses. It is possible, that hereafter, when such experiments 

 are multiplied, we may discover too many anomalies to allow us 

 longer to consider these two rocks as nearly allied to each other, 

 and that we shall be obliged to arrange soap-rock as a distinct species 

 of steatite. 



Serpentine analysed by Kirwan. Soap-rock analysed by Klaproth. 



Silica . , 0, 45 0,48 



Magnesia . 0, 23 0, 20.50 



Alumina . 0, 18 0, 14 



Iron . . 0, 03 0,01 



Water . . 0, 12 0, 15.50 



101 99 



We see that with the exception of the silica and the water, which 

 are most abundant in the soap-rock, there is in this last substance a 

 diminution of about 0,03, or 0,04 of all the other component parts 



* Brjchant, Traite do Miiicralogie. tome i. p. 471 



