SERPENTINE. 199 



strata are confounded among the multitude of discor- 

 dant rifts, as happens also in diallage rock. Where 

 visible, it admits of no doubt; the indications of the 

 strata being prolonged in a parallel direction to those 

 of the accompanying schistose rocks, and dipping in 

 a conformable manner. The same appearances, if less 

 explicit, may be traced in the neighbouring island of 

 Fetlar. I cannot quote any further examples of this 

 disposition; the apparently similar indications in Aber- 

 deenshire being extremely questionable. 



The associations of Serpentine with the primary 

 rocks are even more various than those of limestone ; 

 since I know not that this has yet been found involved 

 in granite, as the former is. In Aberdeenshire, irre- 

 gular masses of Serpentine are enclosed within that 

 rock, excepting, of course, where it is itself visible. I 

 know not that this appearance is an objection to the 

 originally stratified nature of Serpentine ; since frag- 

 ments or masses of other rocks are often found in this 

 position. But it is worthy of remark, that, at the 

 contact of the granite 'and the serpentine, there is 

 generally a lamina of steatite or of talcose schist; 

 while there is occasionally an uncertainty of charac- 

 ters at the junction, which may even be termed a trans- 

 ition between the two. We shall presently see the 

 value of this observation. 



In Sutherland, and in Glas island near Harris, ser- 

 pentine is found imbedded in gneiss; having two 

 parallel sides, or assuming the appearance of a short 

 stratum, while in this association, the external parts 

 are commouly intermixed with hornblende and with 

 actinolite ; so that an irregular transition into the sur- 

 rounding rock is produced. In Shetland it is associated, 

 indifferently, with gneiss, and with micaceous, chlorite 

 and argillaceous schists, as it is with the latter roc 



