J. GEIKIE ON THE GLACIAL PHENOMENA 



height of 80 feet. At the Butt some shelly sand, which appears to 

 be of aqueous origin, overlies the glacial deposits, and reaches to a 

 height of 80 feet or so above the sea. It is just possible, however, 

 that this accumulation may be merely a rearranged portion of the 

 fossiliferous glacial beds ; at all events, no recent marine deposit 

 attained an equal elevation in any of the islands. Shelly sands do 

 occur at higher levels, especially in the little islands south of Barra ; 

 but these are simply blown in by the strong westerly winds from 

 the sandy beaches, the shelly materials consisting chiefly of finely 

 comminuted fragments of the common cockle. What appear to be 

 old sea-levels occur along the shores of West Loch Tarbert, and here 

 and there upon the west coasts of several of the islands ; but none 

 of these reaches higher than a dozen feet or so above the sea ; and I 

 should have been surer of their marine origin had I found beach- 

 deposits resting upon them, but I was not so fortunate. Neverthe- 

 less one can hardly doubt that much of the low flat ground that 

 borders on the Atlantic has been reclaimed from the sea in post- 

 glacial times. The absence of recent marine deposits at high 

 levels has struck me also in not a few of the islands of the Inner 

 Hebrides, the raised beaches which I have seen occurring mostly 

 below a height of 100 feet above the present sea-level. Prom 

 the aspect presented by some of these "raised beaches," they 

 seemed to indicate no long persistent submergence, but rather 

 to have been the result of storm-waves. Not unfrequently they 

 occur on low spits of land exposed to the full swell of the Atlantic, 

 and they appear also upon the borders of narrow bays facing in 

 the same manner the open sea. Along the steeper shores of the 

 same islands, however, one usually looked in vain for ledges 

 excavated in the solid rock at levels corresponding to those occu- 

 pied by the shingle-beds or raised beaches, and the most distinct 

 ledges occur at low levels. According to my colleague, Mr. J. 

 Home, there is a similar absence in the Shetland Islands of high- 

 level recent marine deposits, and my brother has shown that this is 

 likewise true of the Orkneys. Although very much has been done 

 towards working out the history of the postglacial submergence of 

 Scotland, there is yet a great deal more to be learned, and not a 

 little, as I believe, to be unlearned. At present we have no 

 evidence to indicate that the mainland of Scotland experienced a 

 greater degree of submergence in postglacial times than 100 feet. 

 The marine deposits at higher levels than this belong, as I have 

 brought forward evidence to show, not to postglacial, but to inter- 

 glacial times. 



At various points along the shores of the Long Island occur beds 

 of peat, with remains of trees, in positions which prove that these 

 outer islands in late postglacial and recent times were of larger 

 dimensions than now. Precisely the same phenomena reappear on 

 the opposite coasts of the mainland, as geologists have long been 

 aware. 



