188 



GEOLOGY OF ARRAN. 



have often been confounded. This section shews the series 

 very distinctly, and it was left by xis completely opened up. 



89. The last section opened was just below the east 

 end of the sandstone gorge, opposite a bend on the river, 

 and a little way above a wooden guard placed upon the 

 stream. Here a blue argillaceous shale, dipping S.W. at 

 15 to 20, forms the bed of the stream, and rises up 

 with the same dip into the east bank. Over this the 

 boulder-clay and other beds come on; and, following ap- 

 parently the inclination of the shale below, they slope 

 towards the stream, and so thin out westwards. This ar- 

 rangement is shewn in the annexed cut (fig. 34) : 



9 



Fig. 34. 



a a a, Shale ; &, boulder-day ; c, shell-bed ; d, upper drifts. 



At the expense of some time and labour, the facings 

 and debris were here completely cleared away, so that the 

 entire section was laid bare, from the underlying shale to 

 the upper drift bed; and nothing could be more interesting 

 or perfectly satisfactory than to observe the contacts and 

 complete distinction between the contiguous beds. The 

 boulder-clay has all its usual characters, as already described, 

 and does not yield a single shelly fragment ; the shells begin 

 to abound directly the overlying clay bed is entered. This 

 has its usual character, which we need not again describe, 

 and over it come the upper drifts, again strongly contrasting 

 with it and with the boulder-clay, but here not well ex- 

 hibited, from the nature of the ground. 



90. This section is highly illustrative in another way. 



