Geology of the Highlands. 233 



ing to the Wernerian arrangement It would rather ap- 

 pear as if the gneiss rocks, tea miles in breadth^ wore the 

 central or oldest formation ; and that, begiunitig with this 

 rock, we could trace corresponding strata on each side. 

 After this general view of the rocks constitutins: the 



Highlands, a more particular account will be readii^' com- 

 prehended. 



rr^ 



fhe granitic layers embraced in the gneiss consist chief- 

 ly of no small proportion of semi-transpnrent quprtz of a 

 hyaline appearance, a very little silver-coloured mica, and 

 a large proportion of greyish-white feldspar of a pearly lus- 

 tre. In a lew limited localities the feldspar is flesh-cciour- 

 ed. Sometimes the quartz is very dark coloured; ard in 

 some rocks the feldspar appears of a sky-blue colour. 



The mica of the gneiss is almost invariably black, and 

 the feldspar while. Beds of considerable extent are em- 

 braced in the gneiss rock near Fort Putnam, which consist 

 chiefly of hornblende. In this rock are found imperfect 

 crystals of green augite of a large size, and considerable 

 quantities of the green coccolite variety. 



Where the gneiss meets the hornblende rock stratum, 

 both north and south, many interesting minerals are dis- 

 seminated. The most beautiful specimens of serpentine in 

 calc spar are found at this meeting of the strata, three miles 

 north of the military academy. They appear like grass- 

 green gems set in masses of pearl. 



Vast quantities of very dark lamellar hornblende appear 

 in the form of veins traversing the hornblende rocks- The 

 same variety of hornblende is disseminated in the granitic 

 layers included in the gneiss rocks ; which is often mistaken 

 forshorl on a slight view of the rocks. It sometimes gives 

 the granite a graphic appearance. 



Those geologists, who study hand specimens in the cabi- 

 net and are disposed to multiply names, may here find the 

 primitive trap, pYimitive greenstone, sienite, greenstone 

 porphyry ; and perhaps every other variety into which the 

 hornblende rock is varied in any country. 



The granulated Iron ore containing small crystals of phos- 

 phate of lime which abounds in the gneiss rocks of these 

 mountains, together with the carburet of iron, with other 

 n)inerals, have already been mentioned in former publica- 

 tions. The minerals of these mountain?, howevtir, have 



