IN GLEN TILT. 331 



are in beds, the small quantity of the rock, that appears, 

 would hardly discover them to be so. 



75. 1 hese compound substances are succeeded (at 4 in the 

 plan) by a red sienite, very similar to that at A. Owing to 

 a covering of lichens, which makes every thing obscure, and a 

 reddish tinge, which pervades the rocks last described as well as 

 the sienite, the one appeared on a first view to pass into the 

 other j but, on a closer examination, the lines of junction be- 

 tween the sienite and the granular quartz, even where the lat- 

 ter approaches to a gneiss, were distinctly traced, and veins 

 of the sienite observed to run through the granular quartz. 

 The sienite first shews itself on the southern bank a little far- 

 ther up, (at 4 in the plan) in the direction of N. between 48" 

 and 53° E. from where it first occurs on the northern. 



76. From these points, to the fall above the bridge, a dis- 

 tance of about sixty yards on the southern bank, and between 

 eighty and ninety on the northern, the prevailing rock is the 

 red sienite ; but it is interspersed, especially on the north side 

 of the river, with masses of gneiss, granular limestone, horn- 

 blende-slate, and granular quartz, from the size of a hazel- 

 nut, to that of several feet in every dimension. The strati- 

 fication of these masses is for the most part distinct. Many 

 of them are imbedded in the sienite ; and others are inter- 

 sected by veins of it, varying in their breadth from a small 

 fraction of an inch to more than a foot, 



77. The appearances throughout these rocks are closely 

 analogous; but it may be more satisfactory to give a separate 

 description of the most remarkable of them, subjoining at 

 the same time, that in such spots as are not particularly dwelt 

 upon, we observed no facts materially different from what I 

 have to state. Every thing that I have to notice below the 

 bridge is on the north side of the river. 



78. The 



