1875.] 131 [Shaler. 



eastward down to the valley of the St. Lawrence. This view I am, 

 in a measure, compelled to take, on account of the relatively small 

 amount of drift along the southern border of the glacial sheet in the 

 State of Ohio. I do not believe that the excavated matter from the 

 basins of the great lakes is represented in the delta of the Mississippi, 

 nor in the surface -deposits of the country to the south of their south- 

 ern border. When we look for this waste we possibly find it in the 

 vast mass of the Newfoundland Banks, which seem to be a huge sub- 

 merged moraine, or delta, which never could have been formed by 

 the transporting power of the St. Lawrence acting as a river. In this 

 fashion we may possibly account for the production of basins extend- 

 ing east and west, like the great lakes. 



The question will be fairly asked, how it is possible for an ice- 

 sheet to have produced stria across the whole continent, from the 

 Arctic Circle to the Ohio, unless it moved continuously over the 

 whole of this long path? This may be answered as follows: If we 

 suppose the retreat of the glaciers to have been accompanied by a 

 true forward glacial movement of the region near the edge of the 

 sheet, we would have every part of the glaciated area in turn sub- 

 jected to the scratching, without the difficulty of supposing that 

 there was a continuous motion over thousands of miles. I do not 

 deny that the ordinary form of glacial motion took place alono- all 

 parts of the border of the glacial sheet for many miles, but to as- 

 sume that this movement took place in the basin of Lake Erie, while 

 the glacial front was at Cincinnati, seems quite unnecessary. I do 

 deny that there is any such terminal moraine along the southern 

 border as is required if we suppose the movement to have been con- 

 tinuous from the centre of the sheet to the border. The whole of 

 the facts may be accounted for by supposing that there was a motion 

 near the border of the ice, possibly for many miles therefrom ; but 

 we are not required to suppose more than this. Local movements of 

 considerable strength there would undoubtedly be within the mass of 

 the glacier, and as long as these occurred near enough to the border 

 to make the relief easier in that direction, they would doubtless tend 

 that way, but we must always remember that scratches alone give 

 very insufficient evidence of the nature and extent of glacial move- 

 ment; at best, they show us the direction of the very last movement's 

 that took place before the ice disappeared. Other erosion marks, 

 like "crag and tail," doubtless tell more ; but these features are proba- 

 bly the product of many successive glacial periods, and not of the last 



