198 Mr. Bryce on the Geology of the Island of Bute. 



1st December, 1847. — The Vice-President in the Chair. 



A living land tortoise, belonging to Mr. Forrester, Gordon-Street, was 

 exhibited; also a specimen of Epiphyllum truncatum in flower, from 

 Mr. Wardlaw, gardener, Ibroxhill. 



The following paper was read: — 



XXXI. — Notices of the Geology of the Island of Bute. By James 

 Bryce, Jun., M.A., F.G.S. 



1. The only account which we possess of the geology of Bute, is that 

 given by Dr. MacCulloch, in his " Description of the Western Islands of 

 Scotland." During the thirty years that have elapsed since the publica- 

 tion of that work, no observations, that I am aware of, have been put on 

 record, either supplementary to this account, or in correction of it. 

 Indeed, the island seems to have been entirely overlooked ; — the superior 

 grandeur and interest of the sister isle of Arran having wholly absorbed 

 the attention of geologists. Yet Bute has many points of great interest 

 in itself; and phenomena, which in Arran are but obscurely shown, are 

 here fully exhibited. During a residence on the island for a part of last 

 summer, I had frequent opportunities of testing the accuracy of Dr. 

 MacCulloch 's account ; and it is but justice to the memory of that distin- 

 guished geologist, to say, that both in this island, and in other islands, 

 and adjoining portions of the mainland, which I have been in the habit 

 of carefully examining from time to time for a considerable period, I have 

 found the description of the phenomena to agree very closely with my 

 own observations, and the work to be an accurate and safe, as well as 

 most pleasant guide. I have not, therefore, in the present communication 

 attempted a new history of the strata of Bute ; but adopting the arrange- 

 ment and descriptions of Dr. MacCulloch, I merely propose to supplement 

 his account by such other observations as seem worthy of being put on 

 record. In order, however, to make the remarks which follow more 

 easily understood, it may be well to state, briefly, a few particulars 

 respecting the general structure of the island. 



2. The island of Bute is naturally divided into four portions, by three 

 deep depressions or valleys, which traverse it in a direction perpendicular 

 to its greatest length, as illustrated in the accompanying sketch. 



No. l. 



a, Kaimes bay ; b, Rothesay ; c, Kilchattan ; m, mica slate ; n, clay slate ; s, sandstone, 

 old red; t, trap: r, the terrace. 



