THE GLACIAL HYPOTHESIS 311 



Hudsons Bay and the polar seas, which, floating over the northern part 

 of the United States, would be met by the warm waters of the Gulf 

 Stream, causing them to deposit their loads. The warm current flow- 

 ing northward would be superimposed on the cold current, the latter 

 continuing southward beneath it, transporting the finer materials, 

 such as now occupy the lower Mississippi Valley. 



Emmons likewise believed the agent of drift transportation to be 

 water and ice. The boulders he thought to be the work of icebergs, 

 but the striations and polishing he felt could not be due to this agency, 

 since the bottom of the ocean is not bare rock, but covered by debris, 

 and, moreover, icebergs would not move in straight lines, a point which 

 some more recent writers have quite overlooked. The bergs might act 

 as agents of transportation, he argued, but not of erosion. According 

 to his ideas the drift-covered region was, during the drift period, de- 

 pressed, the country low and connected at the north with an extensive 

 region giving rise to large rivers which flowed in succession over dif- 

 ferent parts of the region lying between Champlain and the St. Law- 

 rence. These rivers united with the Atlantic on the south through the 

 Champlain, Hudson and Mohawk valleys. They bore along ice loaded 

 with sand, pebbles, etc., which scratched and grooved the surface of 

 rocks over which they flowed, and were the agents also of perforating 

 the rocks in the form of pot holes. 



Hall's ideas were somewhat hazy. That he did not accept Agassiz's 

 doctrine of a vast ice sheet is very evident. Thus, he wrote that 



Blocks of granite, either enclosed in ice or moved by other means, have been 

 the principal agents effecting the diluvial phenomena; that they have scored 

 and grooved the rocks in their passage and, breaking up the strata and mingling 

 themselves with the mass, have been drifted onward carrying everything before 

 them in one general melee. That such may have been the case in some in- 

 stances or in limited localities, can not be denied; but that it ever has been 

 over any great extent of country will scarcely admit of proof. 



Hall was at this time evidently a catastrophist and regarded the 

 drift soils, terraces, and the deep valleys and water courses as due to 

 the violent action of water which may have been caused in part by a 

 sudden submergence and the rapid passage of a wave over its surface. 

 His views, indeed, were in many respects little, if any, in advance of 

 those held by Mitchill twenty-five years earlier. Like Mitchill, he 

 conceived of an inland sea bounded and held back by the Canadian 

 highlands on the north, the New England range on the east, and high- 

 lands of New York and the Alleghenies on the south, and the Eocky 

 Mountains on the west. These presented barriers of from one thou- 

 sand to twelve hundred feet above the level of the ocean until broken 

 through by the St. Lawrence, the Susquehanna, the Hudson, partially 

 by the Mohawk at Little Falls, and perhaps also by the Connecticut. 



