THE OLD RED SANDSTONE. 13 



the contact of the latter with the slate along this, their only 

 line of junction, is of very limited extent. At no other part 

 of the boundary does the fine granite meet the slate band; 

 and here it alters the slate in the same manner as the coarse 

 granite : the slate is, in fact, converted into a banded rock, 

 in which a partial separation of the ingredients has been 

 effected, and a variety produced closely resembling a dark- 

 coloured gneiss. The annexed section (fig. 5) will best shew 

 the relation of the rocks at this interesting junction : 



Fig. 5. 



c, Slate penetrated and altered by fine granite ; b, fine granite ; 

 a, coarse granite, forming the upper slope and top of Ben-Ghnuis ; 

 d, rock uncertain. 



The Old Red Sandstone. 



7. The encircling band of clay slate is succeeded on the 

 east and south by a band of old red sandstone, which, like 

 the slate band, is of irregular breadth. It begins to overlie 

 the slate at the Fallen Rocks on the north-east coast, and 

 occupies the shore thence to the march of Achab farm, half a 

 mile north of Corrie. Here it retires inland, the carbon- 

 iferous formations taking its place on the shore; crosses in a 

 narrow band to the west of Maoldon, and stretches thence 

 continuously westward, around the border of the slate, to the 

 mouth of Mauchrie Water. Between this point and Dougrie, 

 near lorsa water-foot, it attains its greatest breadth. The 



