38 James Oeikle — On Changes of Climate. 



materials re-assorted. Yet a vast number escaped this levelling pro- 

 cess to puzzle future geologists as to "how they managed it." To 

 the period of re-elevation I feel inclined to refer all the post-Grlacial 

 clays with Arctic and Boreal shells. I do not, however, mean to say 

 that any hard and fast line can be drawn between these deposits and the 

 Karnes ; nor would I think of denying the possibility of shell-bearing 

 clays having been deposited during subsidence. Both kinds of drift 

 may have accumulated on different parts of the same sea-bottom, but 

 the only junction of the two I ever had the luck to detect showed 

 plainly that the clays abutted against the sand and gravel, and even 

 spread over the truncated or flattened tops of the Kames. I never 

 found Kames resting upon any of the Arctic shell-beds. Not that I 

 think these facts taken by themselves go for much. It might be said 

 that as the land sank down, the clays would naturally come to lie 

 upon the gravels, the deep-sea deposits overlapping the shallow- 

 water accumulations. Yet if they did do so, it is certainly singular 

 that they have never been detected in the interior of the country. 

 Irregular patches of laminated clay occur here and there in hollows 

 of the Till at considerable heights above the sea, but it is often 

 doubtful whether they are of marine or freshwater origin. None of 

 them, at all events, have yielded arctic shells. If arctic shelly clays 

 ever occurred in as thick beds in the inland as in the maritime dis- 

 tricts, surely we should have found some notable trace of them. It 

 will not do to lay the blame of their disappearance on that geological 

 scapegoat denudation. Denudation has not run off with the Kames, 

 why should it have been less considerate with the clays ? The 

 Kames have come down to us almost, if not quite, in the same state 

 as the sea-god left them ; but if shelly clays ever existed in the 

 interior parts of the country, they would appear to have vanished, and 

 left not a wrack behind. If it was in Scotland only where the arctic 

 shell-clays were confined to the maritime districts, there might be 

 some excuse for dragging in denudation to account for their absence 

 at the higher levels reached by the Kame drift ; but in Norway and 

 Labrador and Maine the shelly clays are restricted precisely as in 

 Scotland to the vicinity of the sea-coast. In North America, sand 

 and gravel drift goes up to great heights, but the shelly clays 

 reach no higher than 600 or 600 feet above the sea ; and, 

 what is still more to the purpose, they show a gradual passage 

 upwards from beds containing a prevalence of Arctic forms to beds 

 in which the organic remains are the same as those in the neigh- 

 bouring seas. I believe our arctic shell-beds will yet be found to 

 do the same. 



In attempting to account for the absence of arctic shell-clays at 

 the higher levels attained by the marine drift, we must bear in mind 

 that the Kames and shelly clays have been formed under very dif- 

 ferent conditions. The former evidently consist of the re-arranged 

 material derived from the waste of pre-existing glacial deposits, 

 and, as far as that goes, might have been accumulated in the waters 

 of a warm ocean ; the latter are composed of fine mud washed out 

 directly from the snouts of glaciers. During the accumulation of the 



