PART OF NEW YORK. 187 



an entire rock, destitute of herbage, and constituting 

 about three-fourths of the whole height of the moun- 

 tain ; which I suppose to be about twelve hundred 

 feet. The foot of this rock terminates abruptly at 

 the margin of the lake, and extends along its shore 

 for more than half a mile : it is commonly known by 

 the name of Roger's Rock. Near the northern ex- 

 tremity of this rock, a spur sets out towards the east, 

 which is apparently about two-thirds as high as the 

 main body of the mountain : it is on this spur, that 

 the following minerals occur either in veins, or im- 

 bedded in primitive Trap, Sienite, or Carbonate of 

 Lime; viz, Augite; Coccolite (Pyroxene- granuli- 

 forme of Hauy) ; Sphene ; granular and massive 

 Garnet; and Plumbago. 



The primitive Trap is well characterised, the 

 Hornblende being in distinct crystalline laminae, not 

 unlike that which occurs in many places in the vicini- 

 ty of Philadelphia, particularly at the head of the 

 old canal road, on the Schuylkill, and on the Brandy- 

 wine, near Wilmington. The rock which I have 

 called Sienite, is composed of Hornblende, and com- 

 pact Feldspar ; it therefore differs from the common 

 Sienite in as much, as the Feldspar does not possess 

 a crystalline structure : the colour of the Hornblende 

 is black, and greenish-black, that of the Feldspar is 

 white and reddish- white, or flesh coloured : the pro- 

 portion of the Hornblende is very small : this is the 

 most abundant rock in the neighbourhood of this part 

 of lake George. 



