132 



this very cause is not the least interesting portion of geologic science. 



In the remarks which I have now the honour to submit to the 

 Society, I do not propose to enter into any theoretical discussion, but 

 merely to attempt a brief account of several appearances which the 

 Frith of Clyde presents, and the analogues of which may be met with 

 on this and every other coast. 



In doing so, I cannot claim originality. Much of what I shall lay 

 before you I have myself observed, but the subject has already been 

 largely written on by such men as Mr. Smith, of Jordan-hill, Mr. 

 Charles MacLaren, Mr. Robert Chambers, and many more. 1 am 

 induced to make this communication, less perhaps by the hope that the 

 local details of a district so far removed as the estuary of the Clyde is 

 from that of the Mersey, will be interesting to you, as by a desire that 

 the class of facts with which I shall have to deal should be brought 

 vinder your notice, that your attention may thereby be directed as oppor- 

 tunity may offer to the observation and recording of the similar 

 appearances which this neighbourhood also abundantly presents. 



My attention was more particularly directed to this branch of geology 

 by a circumstance, an account of which I had the honour of giving at 

 the time to the Philosophical Society of Glasgow. Those acquainted 

 with the topographical features of Glasgow, will remember that the 

 town is built on a series of ridges of some eminence, running parallel, 

 or nearly so, to the River Clyde, and that a slight hollow betwixt two 

 of these, namely, Blytheswood Hill and the commencement of Garnet 

 Hill, is occupied by Sauchiehall-street. In digging a drain in this 

 street, in the summer of 1850, the workmen, after going down about 

 four feet, came to a bed of pure peat, one foot thick, and below that 

 they dug four feet through beds of sand, containing shells of the 

 common species, " Trochus Ziziphanus." In prosecuting my inquiries, 

 I soon found that the occurrence of shells at heights above the level of 

 the sea, from 40 to 3G0 feet, was not at all uncommon in the valley of 

 tlie Clyde. 



Of a relative change in the level of the sea and land, denoted by this 

 ancient beach in the heart of Glasgow, we have no want of corrobo- 

 rative proofs. Some of these I shall proceed to describe. 



Commencing with the Island of Arran, we find there undeniable 

 evidence of this alteration of level. The road from Brodick to Corrie, 

 and so on round the north end of the Island, occupies a tlat and level, 

 but not broad, space of ground, a little elevated above the level of the 

 sea, and backed by a series of cliffs of considerable height, and the 

 vertical faces of which are water-worn and hollowed out into caves. The 



