110 {STUDIES, SCIENTIFIC AND SOCIAL chap. 



erosion have never discussed it, intimating that they 

 " deemed silence on this topic more prudent than speech." 



As this theory is put forward with so much confidence, 

 and by geologists of such high reputation, I feel bound to 

 devote some space to its consideration, and shall, I think, 

 be able to show that it breaks down on close examination. 



In the first place, it does not attempt to explain that 

 wonderful absence of valley-lakes from all the mountain 

 regions of the world except those which have been highly 

 glaciated. It is, no doubt, true that during the time the 

 lakes were filled with ice instead of water they would be 

 preserved from filling up by the influx of sediment ; and 

 this may be fairly claimed as a reason why lakes of this 

 class should be somewhat more numerous in glaciated 

 regions, but it does not in any way explain their total 

 absence elsewhere: We are asked to believe that from 

 the period immediately preceding the glacial epoch to our 

 own day, earth-movements of a nature to produce deep 

 lakes occurred in every mountain range without exception 

 that was about to be or had been subject to severe glacia- 

 tion, and not only so, but occurred on both sides of each 

 range, as in the Alps, or all round a mountain range, as in our 

 Lake district, or in every part of a complex mountain region, 

 as in Scotland from the Frith of Clyde to the extreme 

 north coast — all in this very limited period of geological 

 time. We are further asked to believe that during the whole 

 period from the commencement of the ice-age to our day 

 such earth-movements have never produced a single group 

 of valley-lakes in anyone of the countless mountain ranges 

 and hilly regions throughout the whole of the very much 

 more extensive non-glaciated regions of the globe ! This 

 appears to me to be simply incredible. The only way to 

 get over the difficulty is to suppose that earth-movements 

 of this nature occurred only at that one period, just before 

 the ice age came on, and that the lakes produced by them 

 in all other regions have since been filled up. But is there 

 any evidence of this ? And is it probable that all lakes so 

 produced in non-glaciated regions, however large and deep 

 they might be, and however little sediment was carried 

 down by their inflowing streams, should have entirely 



