318 GEOLOGY OP BUTE. 



merely be a repetition of facts contained in all elementary 

 works. The sandstone is in the place of the Old Red, 

 as succeeding the slates, and has much of the mineral 

 character of this formation in other districts. Along the 

 E. shore in several places, and again at Kilchattan, beds of 

 limestone occur subordinate to it; but unlike the Arran 

 limestones in the same subordinate positions, they have no 

 fossils; containing much siliceous matter, they are of little 

 economic value, and thus have many analogies with the corn- 

 stones of the Old Red, such as occur near the base of Ben- 

 Lomond and in several localities in Arran, the march of 

 Achab farm, the Fallen Rocks, Glen Loig, and Kilchattan. 

 It is very doubtful, however, whether the rock is really of 

 this age.* 



Carboniferous Beds. 



133. But there are in Bute sandstones and limestones 

 newer than these, which have been till very recently quite 

 overlooked by geologists. There occurs, in fact, at Ascog a 

 small coal formation which may yet turn out to be of 

 economic value. It is connected with an isolated, overlying 

 mass of trap, appearing on the shore and occupying the cliffs 

 near Ascog mill. On the north side of the promontory, 

 south of the mill, several thin courses of nodular limestone 

 traverse beds of brown, crumbling shale, subordinate to sand- 

 stone. The shale is of considerable thickness, and rises into 

 banks above the road. The south side of the promontory 

 presents the following section (fig. 38). 



The lowest bed, o, is a fine-grained, bluish-gray, nodular 



In the last edition, the lowest beds of the sandstone were referred 

 to the Old Bed ; a late visit to Bute, however, led me to doubt this 

 view, and the qualified statement in the text was then made. I have 

 since learned that Professor Geikie considers all the sandstones to be 

 newer than the Old Bed. It seems to me, nevertheless, to be highly 

 probable that the lowest bands traversing the obscured belt of low 

 land along the border of the slate may really yet be found to be of 

 this age. 



