68 THE HISTORY OF THE NORTH ATLANTIC 



that of a basin as that of a shallow elongated plate with its 

 middle a little raised. Its true margins are composed of 

 portions of the over-crust folded, overlapped and crushed, as 

 if by lateral pressure emanating from the sea itself. We can- 

 not, for example, look at a geological map of America without 

 perceiving that the Appalachian ridges, which intervene be- 

 ween the Atlantic and the St. Lawrence valley, have been 

 driven bodily back by a force acting from the east, and that 

 they have resisted this pressure only where, as in the Gulf of 

 St. Lawrence and the Catskill region of New York, they have 

 been protected by outlying masses of very old rocks, as, for 

 example, by that of the island of Newfoundland and that of 

 the Adirondack Mountains. The admirable work begun by 

 my friend and fellow-student, Professor James Nicol, followed 

 up by Professor Lapworth, and now, after long controversy, 

 fully confirmed by the recent observations of the Geological 

 Survey of Scotland, has shown the most intense action of the 

 same kind on the east side of the ocean in the Scottish high- 

 lands ; and the more widely distributed Eozoic and other old 

 rocks of Scandinavia may be appealed to in further evidence 

 of this.i 



If we now inquire as to the cause of the Atlantic depres- 

 sion, we must go back to the time when the areas occupied 

 by the Atlantic and its bounding coasts were parts of the 

 shoreless sea in which the earliest gneisses or stratified granites 

 of the Laurentian age were being laid down in vastly extended 

 beds. These ancient crystalline rocks have been the subject 

 of much discussion and controversy, to which reference has 

 been made in a previous chapter. 



It will be observed, in regard to these theories, that they do 



* Address to Geological Section, Brit. Assoc, by Prof. Judd, Aberdeen 

 Meeting, 1885. According to Rogers, the crumpling of the Appalachians 

 has reduced a breadth of 158 miles to about 60. Geikie, Address, Geo- 

 logical Society, 189 1-2. 



