GEOLOGY OF ARRAN. 



breadth is also considerable from the Fallen Rocks to a point 

 a little south of the base of Cioch-na-h'oighe. A line from the 

 north side of Brodick Bay to Dougrie very nearly marks out 

 its line of junction with the slate. In structure it varies from 

 a fine-grained red or dark-brown sandstone to a coarse con- 

 glomerate, in which the fragments are more than a foot in 

 diameter. The coarse and fine strata do not follow any 

 particular oi-der, but alternate throughout the formation, 

 indicating the operation of powerful currents and interme- 

 diate periods of repose. 



It may here be merely noticed that the sandstones of the 

 coast have the edges of the strata tm-ned up towards the 

 central granite, and that north of the mouth of North San- 

 nox Water the dip is towards the north-east and north, 

 while south of this point it is south-east and south. Thin 

 bands of limestone occur subordinate to the old red sandstone 

 at the march of Achab farm at Corrie, in Glenloig, and in a 

 few other places. This limestone is of concretionary struc- 

 ture, without fossils, and similar to the cornstoues of Eng- 

 land members of the Old-Red system. 



T/te Carboniferous Series. 



8. The southern half of the island, southward of the old 

 red sandstone boundary above defined that is, from the 

 String road and valley of Mauchrie Water to the South End 

 is composed of several members of the carboniferous series, 

 broken through and overlaid by various igneous rocks, chiefly 

 those of the greenstone type. The prevailing rock and sub- 

 stratum of the whole southern plateau is red sandstone, vary- 

 ing from a fine compact structure to that of a coarse con- 

 glomerate. A band of this sandstone extends also along 

 the eastern shore northwards to Corrie ; and again from 

 the Fallen Rocks north-west to the Scriden at the northern 

 extremity near the entrance of Loch Ranza. Subordinate to 

 this sandstone are beds of limestone, abounding in fossils of 

 tine carboniferous types, with beds of shale and coal, in which 



