458 Proceedings of the Royal Irish Academy. 



"boulder-clay, siicli as the occurrence of giant kettles, the absence of 

 marine shells over large tracts of country, &c. 



According to Prof. J. Geikie (35 «, p. 432), the boulder-clay which 

 has been traced over a vast area in Northern Europe, exactly resembles 

 in all important particulars the similar accumulations met with in the 

 British Islands. They resemble one another also in the occasional 

 occurrence of sea-shells, the frequent appearance of bedded deposits, 

 iind the often inexplicable course taken by boulders from their sourct; 

 of origin. It is well, therefore, to weigh the words recently uttered 

 by Prof. Bonney (lOrt, p. 280) before rushing to tlie conclusion that 

 this boulder-clay necessarily represents a ground moraine. " The 

 singular mixture," he says, *' and apparent crossing of tlie paths of 

 boulders, as already stated, are less difficult to explain on the hypo- 

 thesis of distribution by floating ice than on that of transport by land- 

 ice, because, iu the former case, though the drift of winds and currents 

 would be generally in one direction, both might be varied at par- 

 ticular seasons. So far as concerns the distribution and thickness of 

 the glacial deposits, there is not much to choose between either hypo- 

 thesis ; but on that of land-ice it is extremely difficult to explain the 

 intercalation of perfectly stratified sands and gravels and of boulder- 

 clay, as well as the not infrequent signs of bedding in the latter." 

 The view of the marine origin of the British boulder-clay has been 

 most carefully worked out by Mr. Mellard lleade (71), whilst Mr, 

 Bulman (143) brought forward some additional objections to the ter- 

 restrial liypothcsis. Sir Henry Howorth (40 r/) has gathered together 

 a sui-prising number of facts in favour of the marine theory, and has 

 embodied his wide knowledge of glacial geology in a work which is 

 quite a storehouse of information. With his conclusions, however, I 

 cannot agree. It seems to me that the distribution of the drift can 

 be explained without invoking a great diluvial catastrophe. 



I think that I shall be able to advance some additional evidence in 

 favour of the view that the boulder-clay of Europe is a marine deposit, 

 and that Northern Russia and Germany were not covered by glaciers 

 during the Pliocene or Pleistocene Epochs, 



It has been urged by many writers, both on zoological and geo- 

 logical grounds, that at some time during the Pleistocene Epoch, or 

 perhaps even later, the "White Sea and the Baltic were joined across 

 Northern Russia, and that then also the lowlands of Northern 

 Gex-many. and those of Sweden and Norway were partially flooded. 

 The zoological evidence alone, that such a junction has taken place, 

 within recent geological times, is very strong indeed. 



