MOMES XII. AND XIII. 



NOME XII. GNEISS AND MICA SLATE. 



This is also a common transition in primitive 

 countries. 



Gneiss and mica slate, from the Alps, &c. 



NOME XIH. STEATITE AND ASBESTOS. 



Steatite, in assuming a fibrous form, passes 

 into asbestos. This transition is very uncom- 

 mon. Saussure has described a rock of this 

 kind ; and Patrin has observed that it affords a 

 remarkable example of the passage of one rock 

 into another. 



" This stone, which I received from M. Struve, 

 is of a grey colour, sometimes inclining to yel- 

 low, sometimes to green. It greatly resembles 

 asbestos; but the filaments are larger, softer, 

 and more unctuous to the touch ; while the 

 fracture lengthwise presents long and large 

 fibres, parallel among themselves, perpendicular 

 to their bases, and irregularly prismatic. Some 

 are straight, others a little bent; and they are 

 sometimes three inches in length. Their lustre 

 is little or none ; and where it seems lively, and 



