4o 



460 T. F. Jamieson — Oscillation of Land in Glacial Period, y 



The marine beds which occur at Lake Champlain and along the 

 •valley of the St. Lawrence have not been traced into the basin of 

 Lake Ontario, although they reach to Kingston, which is close, to its 

 eastern extremity. Now as the present level of Ontario is' 230'feet 

 above the sea, and the highest marine beds at Montreal reach up to 

 470, it is evident that in the present configuration of the country, a 

 sea reaching this level at Montreal would extend into and cover all 

 Lake Ontario. But the strata around Lake Ontario are lacustrine, 

 and so far as hitherto explored have yielded nothing but land and 

 freshwater fossils, and not a trace of the marine shells have any- 

 where been got which are so common in the sands and clays of 

 Montreal and Quebec. We are therefore driven to the conclusion 

 that the sea water somehow did not gain access to the area of the 

 great lakes, or, if it did, the deposits left by it have since been I'e- 

 moved. But we have seen that other facts point to the conclusion 

 that the ice must have vanished from the lake region long before it 

 disappeared from the valley of the St. Lawrence ; so that if the 

 depression was caused by ice, the lake region would be sooner re- 

 lieved from pressure, and would regain its height long before the 

 St. Lawrence district did so. The submergence of the latter would 

 therefore take place after the shores of Lake Ontario had risen, and 

 the sea- water would consequently not extend into the lake basin ; 

 moreover the ice, as we have seen, being heaviest to the east of the 

 lake, would cause a greater depression in that direction. This 

 curious circumstance therefore harmonizes with the theory I am 

 advocating. 



It is perfectly plain that the supposed action of an ice-cap affecting 

 the centre of gravity of the earth, and draining the ocean waters 

 northwards, is a theory that affords no explanation of these singular 

 features in the surface geology of the great lake district of America 

 and of the Mississippi basin, because it is not a question of sub- 

 mergence beneath the sea that we have to answer in these regions. 

 It is a sinking and rising of the land, not of the sea, that we have 

 to account for. 



The Loess Beds. 



Movements of depression and elevation caused by the presence 

 and. disappearance of the ice would also help to explain the formation 

 of the Loess beds of the Rhine, Danube, and other rivers. 



In reference to the Loess of the Rhine, Sir Charles Lyell says : 

 "It seems necessary to suppose first a time when it slowly accumu- 

 lated ; and secondly, a later period, when large portions of it were 

 removed, or when the original valley which had been partially 

 filled up with it, was re-excavated. Such changes may have been 

 brought about by a great movement of oscillation, consisting first of 

 a general depression of the land, and then of a gradual re-elevation 

 of the same. The amount of continental depression which first took 

 place in the interior must be imagined to have exceeded that of the 

 region near the sea, in which case the higher part of the great valley 

 would have its alluvial plain gradually raised by an accumulation of 

 sediment, which would only cease when the subsidence of the land 



