108 



jf Strontian^ ^ 



there appears to have taken place an exchange of mhierals along the 

 frontier, the quartz having entered into the limestone as a hostage 



for tlie lime in tlie granite. 



4 



these cases it is always the quartz which is foremost ; like the light 

 infantry of an army previously to a general engagement, while the 

 felspar, which is the main body is In allignment or column in rear- 

 He also considers the fact to be corroborative of an opinion expressed 

 by Humboldt in his Geognosy, viz. that there appears to be no reci^ 

 procity or sympathy in nature between limestone and felspar. I 

 have not used the language of either of these gentlemen, but I be- 

 lieve the sense is the same* 



The felspar, which is usually the predominating mineral in this 

 aggregate, is generally of a deep ilesh-color j and when this is joined, 

 as it often is, to opalescent quartz, a beautiful compound is the re- 

 sult. The structure of the rock, when the felspar is the predomi- 

 nating mineral, is either compact or laminar : when hornblende 

 abounds, it is generally foliated like gneiss, and sometimes porphy- 

 ritic. It exhibits no distinct appearance of stratification, although 1 

 have sometimes imagined that such a feature did exist, and that ver- 

 tical strata directed between south and south-west, could be obscure- 

 ly traced. Schorl, epidote, ^nd tremolite, are among tlie dissem- 

 inated minerals. The schorl is usually in small imperfect crystals, 

 studding the surface of the natural joints of the syenite or granite, 

 while the epidote occupies a similar position in the greenstone ; the 

 former is also found in tolerably large pieces, (much intermixed 

 with white quartz) imbedded in the granite. These pieces shew 



very 



shining coal- 



black faces of prisms, deeply striated, may often be seen. Although 

 felspar usually envelops the schorl, it is seldom intermixed widi it- 

 A curious bed, composed almost entirely of epidote and tremolite, 

 is met with in this neighborhood, holding a geological position which 

 UTiplies a contemporaneous origin with tlie crystalline rock above de- 

 scribed. This bed, together with the frequent occurrence of schorl 

 and epidote in this rock, affords the best support to its pretensions to 

 be considered primary. Tiie following Is a mlneralogical descrip- 

 tion of the bed in question, with which I shall terminate this paper. 

 This aggregate strongly resembles a verde antico, or a mixture 

 of granular serpentine and white limestone ; its colors are therefore 

 green (dark) and white. The white mineral is the paste through 

 which the other is distributed, usually in small rounded grains, 

 though an ae^gregation of prismatic ciTSlals or of laminae may be oc- 



