PHYSICAL AND CLLMATAL CONDITIONS. US 



valley, and in whicli the icel)ergs from the far north were 

 probal)ly reinforced l»y ,<:j;reat numbers of similar masses 

 descendinf; from tlie Laurenlian hills on the north side of 

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

 shores. 



I hiive referred in Acadian (leology * to the ingenious 

 theory of J )arwin us to the transport of boulders from lower 

 to higher levels by tloalin*' 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 slal)S of sandstone from the plains of Cumber- 

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

 summits of liills several hundred feet higher than the 

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

 infre(|uent througliout Eastern Canada, and are quite 

 inexplicable on any theory of land glaciation. 



As to transport of materials l)y floating ice, it is almost 

 superfluous to give farther details. A few examples and 

 a few applications to the I'leistocene may l)e mentioned. 

 AVe have already seen that extensive boulder-drift is now 

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

 boulder beaches and pavements almost rival the so-calJed 

 moraines of the Pleistocene. Even on lake margins the 

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

 The writer long ago ilescribed 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 tlie dredges of the " Challenger " took \i\) 



* Fourth Edition, p. 65. 



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

 X Acadian Geology. Report on Frince Edward Island. 

 g Bull. Geol. Sooy. America, Vol. I. 



