26 



THE rOST-PLlOCENE. 



rocks of Labrador and Canada, distant 250 miles or more to the 



northward. These Laurentian rocks are chiefly found on the north 



side of the isL'vnd, as if at the time of their ari'ival the island formed a 



shoal, at the north side of which the ice carrying the boulders 



grounded and melted away. With reference to these boulders, it is 



to be observed that a depression of four or five hundred feet would 



open a clear passage for the Arctic current entering the Straits of Belle 



Isle to the Bay of Fundy ; and that heavy ice carried by this current 



would then ground on Prince Edward Island, or be carried across it 



to the southward. If the Laurentian boulders came in this way, 



their source is probably 400 miles distant in the Strait of Belle Isle. 



On the north shore of Prince Edward Island, except where occupied 



by sand dunes, the beach shows great numbers of pebbles and small 



boulders of Laurentian rocks. These are said by the inhabitants to 



be cast up by the sea or pushed up by the ice in spring. AVhether 



they are now being drifted by ice direct from the Labrador coast, or 



are old drift being washed up from the bottom of the gulf, which 



north of the island is very .shallow, does not appear. They are all 



mucli rounded by the waves, differing in this respect from the majority 



of the boulders found inland. I may add here that Laurentian 



boulders have been observed on the north shore of Nova Scotia.* 



Dr Iloneyman records their appearance even on the Atlantic coast., 



The older boulder clay of Prince Edward Island, with native 

 boulders, must have been produced under circumstances of powerful 

 ice action, in which comparatively little transport of material from a 

 distance occurred. If we attribute this to a glacier, then as Prince 

 Edward Island is merely a slightly raised portion of the bottom of 

 the Gulf of St Lawrence, this can have been no other than a gigantic 

 mass of ice filling the whole basin of the gulf, and without any slope 

 to give it movement except toward the centre of this great though 

 shallow depression. On the other hand, if we attribute the boulder clay 

 to floating ice, it must have been produced at a time when numerous 

 heavy bergs were disengaged from what of Labrador was above water, 

 and when this was too thoroughly enveloped in snow and ice to afford 

 many travelled stones. Further, that this boulder-clay is a submarine 

 and not a subaerial deposit, seems to be rendered probable by the cir- 

 cumstance, that many of the boulders of the native sand.stone are so soft 

 that they crumble immediately when exposed to the weather and frost. 

 The travelled boulders lying on the surface of the boulder clay 

 evidently belong to a later jDcriod, when the hills of Labrador and 

 Nova Scotia were above water, though lower than at present, and were 

 sufficiently bare to furnish large supplies of stones to coast Ice carried 

 " Notes on Post-jjliocene, 1872, p. 112. 



