168 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Feb. 6, 



suggestions, I carefully levelled each for ascertaining their present 

 altitude above high water mark, and for determining their horizontal 

 position. The former gave respectively 40 feet 1 1 inches and 40 feet 

 4 inches ; but, allowing for some little difference in the high water 

 mark, I have given the mean as the altitude of each. The latter 

 (No. 2) I found to be a plane, perfectly horizontal. The deposit is 

 composed entirely of water-worn stones, of various sizes, from \ cwt. 

 to a pebble, and of the same character as the solid neighbouring 

 rocks, without fossils, shells, or wood ; which, however, is not sur- 

 prising, as few shells are to be found on the shore ; and they, ex- 

 posed to a heavy sea, would become pulverized and difficult to trace ; 

 and wood is seldom met with. The shingle of No. 1 is covered by 

 about 6 inches of a mossy soil ; that of No. 2 is nearly exposed, and 

 in places as clean as the daily-washed beach ; and, whereas the first 

 is but a short distance from and parallel to the present shore, exposed 

 to the same direction of swell and exhibiting the same effects, that of 

 the latter alone has the general character of a beach, as the present 

 margin of the isle in the direction of the longest fetch is now low, 

 broken, and rocky. 



Lochgilphead. 

 August 29th, 1851. 



Having been detained in Kerrera Sound, I was led by information 

 to search for a deposit with fossils, which I was fortunate in finding ; 

 and, on levelling it, found it to be within 1 inch of the same height 

 as the raised beaches before referred to. The base of the deposit 

 being 39 feet 10 inches, the band about I foot in thickness=40 feet 

 10 inches ; — 40 feet 11 inches being the elevation given (or rather 

 found) of the beach on Lunga. 



The deposit contains fossils having the same appearance as shells 

 now to be constantly seen thrown up by the sea and lodged in the 

 cavities of rocks. 



[In a letter to the Secretary of the Geological Society.] 



Admiralty Survey, Oban, 

 October 31st, 1855. 



I beg herewith to forward a tracing of part of the West Coast of 

 Jura which exhibits the most remarkable raised beaches of the 

 district ; they can also be traced nearly to the northern extreme of 

 the island ; and there is a conspicuous one to the south. Upon the 

 Isles of Colonsay and Oronsay they are equally distinctly marked ; 

 the bare shingle being exposed at the medium level of about 40 feet. 

 I was not on the survey of Islay, but should think they would be 

 traceable there also. 



These beaches are remarkable under several considerations. First, 

 their imiform level, although separated many miles apart, as between 

 Loch Tarbert and Lunga eighteen miles, between Lunga and Kerrera 

 fifteen miles ; — secondly, their uniform horizontal position ; — thirdly, 

 the vast extent of exposed shingle, from the polished pebble the size 

 of a pigeon's egg to the rough stone of near a hundredweight, covering 

 many acres of land ; — and fourthly, their undisturbed state, exhibit- 



