1883.] 483 [Crosby. 



on his map showing the land at the beginning of Paleozoio 

 time there appears in this part of the continent only a very narrow, 

 broken strip, lying far within the present continental borders) ; 

 while others have considered it as of continental extent. As I 

 have before remarked, if it extended more than one hundred 

 miles beyond the present coast line, a part of it now forms the 

 floor of the deep sea. 



There is another important consideration, besides the thickness 

 of the Paleozoic sediments, demanding an extension of the Paleo- 

 zoic land to or beyond the existing border of the continent, and 

 that is the entire absence of Paleozoic rocks on the Atlantic sea- 

 board south of New England. Very plainly, the Blue Ridge belt 

 of crystalline rocks was not, during the Paleozoic era, a narrow 

 strip of land washed by the ocean on both sides, but it formed 

 the western border of the Paleozoic continent. And all analogy 

 requires us to suppose that this Paleozoic land had breadth like 

 the continents of to-day. But this is equivalent to saying that 

 the greater part of it is now covered by the deep sea. 



As I have elsewhere pointed out, the submarine contours of 

 the Gulf of Maine show that it must have been once something 

 like the modern Hudson Bay, land-bordered on the east as well 

 as on the west; for a broad submarine ridge or plateau extends 

 over nearly nine-tenths of the distance betAveen Nova Scotia and 

 Cape Cod, forming a nearly complete barrier between the compar- 

 atively deep water of the Gulf of Maine and the greater depths 

 of the ocean beyond. If the sea bottom were elevated fifty fath- 

 oms, the Gulf of Maine, although still three hundred miles long, 

 and having a maximum depth of 110 fathoms, would be changed 

 from a broad-mouthed bay to an almost completely land-locked 

 gulf. The Paleozoic rocks observable around the Gulf of Maine 

 show that it was in existence in Paleozoic time, when its eastern 

 border probably formed a part of a great Atlantic continent. 



At the close of the Paleozoic era the Appalachian sediments 

 yielded to the horizontal pressure in the crust and the Alleghany 

 Mountains were formed. It is plain that when a zone of the 

 earth's crust is thus plicated a subsidence of adjacent portions is 

 a necessary consequence. Professor Dana, holding that the con- 

 tinents are stable and fixed, attributes the folding and crumpling 

 of the strata in mountains in general, and in the Alleghanies in 



