THE HISTORY OF THE NORTH ATLANTIC 77 



conditions of sedimentation. It would seem also that, as Hicks 

 has argued for Europe, and Logan and Hall for America, this 

 Cambrian age was one of slow subsidence of the land previously 

 elevated, accompanied with or caused by thick deposits of 

 detritus along the borders of the subsiding shore, which was 

 probably covered with the decomposing rock arising from long 

 ages of subaerial waste. 



In the coal formation age its characteristic swampy flats 

 stretched in some places far into the shallower parts of the 

 ocean. 1 In the Permian, the great plicated mountain margins 

 were fully developed on both sides of the Atlantic. In the 

 Jurassic, the American continent probably extended farther to 

 the sea than at present. In the Wealden age there was much 

 land to the west and north of Great Britain, and Professor 

 Bonney has directed attention to the evidence of the existence 

 of this land as far back as the Trias, while Mr. Starkie Gardiner 

 has insisted on connecting links to the southward, as evidenced 

 by fossil plants. So late as the Post-glacial, or early human 

 period, large tracts, now submerged, formed portions of the 

 continents. On the other hand, the interior plains of America 

 and Europe were often submerged. Such submergences are 

 indicated by the great limestones of the Palaeozoic, by the chalk 

 and its representative beds in the Cretaceous, by the Num- 

 mulitic formation in the Eocene, and lastly, by the great Pleis- 

 tocene submergence, one of the most remarkable of all, one 

 in which nearly the whole northern hemisphere participated, 

 and which was probably separated from the present time by 

 only a few thousands of years. 3 These submergences and ele- 



1 I have shown the evidence of this in the remnants of Carboniferous 

 districts once more extensive on the Atlantic coast of Nova Scotia and Cape 

 Breton ("Acadian Geology "). 



8 The recent surveys of the Falls of Niagara coincide with a great many 

 evidences to which I have elsewhere referred in proving that the Pleistocene 

 submergence of America and Europe came to an end not more than ten 



