THE GLACTAL PERIOD AND THE EARTH-MOVEMENT HYPOTHESIS. 239 



were uplifted — will readily believe that some of the sub- 

 marine river-troughs of North America, such as that of the 

 Hudson, may belong even to Secondary times.* It would be 

 hard to say at what particular date the excavation of the 

 Scottish highland valleys commenced — but it was probably 

 during the later part of the Palaeozoic era. The process has 

 doubtless been retarded and accelerated frequently enough, 

 during successive movements of depression and elevation, but 

 it was practically completed before the beginning of Pleisto- 

 cene times, and that is all that we may trouble about here. 

 Precisely the same conclusion holds good for Norway : and 

 such being the case it is obvious that the origin and age of 

 the fiords have no bearing whatever on the problem of the 

 glacial climate and its cause. In point of fact the evidence, 

 as already remarked, tells against the " earth-movement 

 hypothesis " for it shows us that, during a period when 

 Europe and North America stood several thousand feet higher, 

 and extended much further seawards, rivers, and not glaciers, 

 were the occupants of our mountain-valleys. It was not 

 until all those valleys had come to assume much the appear- 

 ance they now present that general glaciation supervened. 



We are not without direct evidence, however, as to the 

 geographical conditions that obtained in the ages that imme- 

 diately preceded the Pleistocene period. The distribution of 

 the Pliocene marine beds of Britain entitles us to assume that 

 at the time of their accumulation our lands did not 

 extend quite so far to the south and east as now. The 

 absence of similar deposits from the coast-lands of North 

 America is supposed to support the view of great continental 

 elevation in pre- glacial times. All it seems to prove, however, 

 is that in Pliocene times the North American continent was 

 not less extensive than it is at present. It is even quite pos- 

 sible that in glacial times pre-existing Pliocene beds may have 

 been ploughed out by the ice, just as seems to have been the 

 case in the north-east of Scotland. But without going so far 

 back as Pliocene times, we meet with evidence almost every- 

 where throughout the maritime regions of the glaciated areas 

 of Europe and North America, to show that immediately 

 before those tracts became swathed in ice the geographical 

 conditions were much the same as at present. The shelly 



* Professor Dana inclines to date the erosion of the Hudson Trough so 

 far back as the Jura-Trias period. American Journ. Science, xl. (J890), 

 435. 



T 2 



