93 



This brings me to the pleasanter task of examining the 

 evidences of ice-action which Dr. Colley March has so ably set 

 before us as affecting the Southern Counties, and which disagree- 

 ment with the great ice-sheet theory need in no way prejudice us 

 from favourably considering. 



The sheets of plateau gravel, mounds and ridges of sand, often 

 resting on boulder clay, on the exclusion of the ice-sheet theory, 

 would find their more natural explanation in the violent current 

 action of the receding waters as the land emerged from the sea at 

 the close of the glacial period, the boulder clay and till having been 

 laid down by melting icebergs and ice-flows during partial sub- 

 mergences. Boulder-clay is now, according to the Challenger 

 expedition, being laid down under the sea within the Arctic circle, 

 one hundred miles from land, by the melting floe ice, in Baffin's 

 Bay and the Labrador coast*. With regard to the Isle of Man, 

 instead of ice having reached to the height of 2,000 feet, as stated 

 on page 73, a writer in the Geological Magazine\ produces evidence of 

 the island having been submerged to a depth of 2,000 feet, during 

 the progress of which I would suggest that the phenomena referred to 

 by Dr. Colley March were produced. Similarly the facts of glacia- 

 tion in North-west Pembrokeshire may be explained by substituting 

 the word " submergence " for " altitude," and the depth of sub- 

 mergence, rather than the thickness of an ice-sheet, was probably 

 "not less than the 800 to 1,000 feet, and may have been much 

 more." 



I may here mention in passing that it is not only in Europe 

 that this difference of opinion as to the explanation of glacial 

 phenomena exists. In Canada our brother geologists also are 

 divided into two camps, one upholding a great ice- sheet theory, and 

 others believing in local glaciation and submergences as affording 

 the true explanation. The great exponent of the more simple 

 theory was the late Sir William Dawson, who had far more oppor- 

 tunities of studying the effects of ice-work in the great North 

 American Continent than we are favoured with in the British Isles, 

 and whose objections to the ice-sheet theory were substantially 

 identical with those which I have endeavoured to lay before you. 



At the top of page 74, the pieces of flint described by Dr. 

 Colley March as coming from Ireland, I would submit are evidences 

 of transport by floating ice rather than by glaciers, there being no 

 sufficient land area in Ireland to produce ice-sheets of the enormous 

 size demanded by the later theory, even were it possible for any 

 known forces to have propelled such glaciers across the Irish 

 Channel. Could our friends discover a glacier of half the 

 dimensions they require traversing a sea-bed even 100 miles across 

 and ascending mountains 1,000 feet high on the other side, our 

 opposition to their views would be dismissed. But we maintain 

 that such a feat has never been accomplished, and indeed is 



* Murray, Reports of Challenger Expedition. 

 See also Sir W. Dawson's ''Great Ice Age" in "Salient Points in the 

 Science of the Earth." 



f New Series, vii. 6. 



