PHYSICAL AND CUMATAL CONDITIONS. 115 



valley, and in which the icebergs from the far north were 

 probably reinforced by great numbers of similar masses 

 descending from the Laurentian hills on the north side of 

 that valley, as well as by the field-ice formed along its 

 shores. 



I have referred in Acadian Geology * to the ingenious 

 theory of Darwin as to the transport of boulders from lower 

 to higher levels by floating ice in a subsiding condition of 

 the land-f This theory, in my judgment, still affords the 

 only satisfactory explanation of such facts as the trans- 

 ference of slabs of sandstone from the plains of Cumber- 

 land and the St. Mary's river in Nova Scotia to the 

 summits of hills several hundred feet higher than the 

 original seats of the erratics. Facts of this kind are not 

 infrequent tliroughout Eastern Canada, and are quite 

 inexplicable on any theory of land glaciation. 



As to transport of materials by floating ice, it is almost 

 superfluous to give farther details. A few examples and 

 a few applications to the Pleistocene may be mentioned. 

 We have already seen that extensive boulder-drift is now 

 taking place in the lower St. Lawrence, and that our 

 boulder beaches and pavements almost rival the so-called 

 moraines of the Pleistocene. Even on lake margins the 

 ice produces appearances of the same kind on a small scale. 

 The writer long ago described these in Nova Scotia,J and 

 Spencer has correlated the ancient and modern margins 

 on the larger Canadian lakes. § The removal of large 

 boulders by the ice is a matter of constant occurrence on 

 our shores, and the dredges of the " Challenger " took up 



* Fourth Edition, p. 65. 



t Journal of London Geol. Society, Vol. IV., p. 315. 

 X Acadian Geology. Report on Prince Edward Island. 

 § Bull. Geol. Socy. America, Vol. I. 



