366 GEOLOGICAL APPEARANCES 



with that which occurred so abundantly upon it towards Glen 

 Criny. Farther up, the fragments are chiefly of gneiss ; and 

 near the head of the Glen, they are either gneiss, or sienitic 

 greenstone, with its gradations. — On the side of Ben y Venny, 

 near the head of the Glen, we met with sienitic greenstone in 

 the fixed rock, and the loose blocks that had fallen from this 

 mountain were either gneiss, or sienitic greenstone ; the latter 

 afforded gradations into grey sienite, for quartz occurred in it 

 frequently. Some of the blocks consisted of felspar, horn- 

 blende, and mica. — In ascending the steep at the head of the 

 Glen, on the western side of the stream, we found the rocks, 

 that projected in different places from the surface, to be alter- 

 nately gneiss, and sienitic greenstone, but could not determine 

 their relative positions. 



148. I now resume the description of the bed of the river. 

 On the eastern side of the Merk, a furlong above its junction 

 with the Deery, the strata are of gneiss, stretching N. 85" E., 

 with a southerly dip at an angle of 22**. Fifty yards farther 

 up, the gneiss stretches N. lOS*" E., and dips to the south at an 

 angle some degrees larger. An hundred and fifty yards far- 

 ther, there is gneiss interstratiiied with beds of felspar porphy- 

 ry ; the stretch is here N. 46" E. and the dip southerly at an 

 antrle of 28". Three hundred yards higher up the stream, the 

 strata are again gneiss, stretching N. 63" E., and dipping south- 

 erly at an angle of 27°. There are here some appearances of 

 bendings in the strata. We saw nothing but gneiss, with its 

 dip southerly, in the fixed rocks, till we came within a quarter 

 of a mile, or somewhat more, of the head of the Glen ; when 

 we met with a junction of gneiss and granite, close to the east- 

 ern side of the stream. The strata of gneiss are much disor- 

 dered ; and are cut by veins, — some of granite, that is to say, a 

 compound of felspar, quartz, and mica, and some of felspar and 



mica. 



