JDr. Dawson — Geology of Prince Edward's Island. 207 



bradorite rock, which must have been derived from the Laurentian 

 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 island, as if at the time of their arrival 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 Lau- 

 rentian rocks. These are said by the inhabitants to be cast up by 

 the sea or pushed up by the ice in spring. Whether 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 much rounded 

 by the waves, differing in this respect from the majority of the 

 boulders found inland. 



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. Farther, that this 

 Boulder-clay is a submarine and not a subaerial deposit, seems to be 

 rendered probable by the circumstance that many of the boulders of 

 sandstone 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 period, 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 by the tidal currents sweeping up the coast, or by the Arctic 

 current from the North, and deposited on the surface of Prince 

 Edward Island, then a shallow sand-bank. The sands with sea- 

 shells probably belonged to this period, or perhaps to the later part 

 of it, when the land was gradually rising. Prince Edward Island 

 thus appears to have received boulders from both sides of the gulf 

 of St. Lawrence during the later Post-pliocene period ; but the 



