390 PALEOZOIC TIME. 



a degree of permanence, in the Appalachian region, after the Pittsburg 

 Coal series, and to a still wider extent, throughout the whole interior 

 east of the Mississippi, after the Upper Coal beds (p. 368) ; so that, 

 when the Carboniferous period closed, the continent in this its eastern 

 half was almost complete. Over the whole surface, including New 

 England, Canada, and the British possessions eastward, no rocks 

 occur between the Paleozoic and Cretaceous, excepting small strips of 

 Mesozoic in the Eastern-border region, east of the Alleghanies, and 

 also in the Connecticut valley and Nova Scotia. 



The interior sea, which in Silurian and Devonian periods had 

 spread from the Gulf of Mexico over the whole Interior Continental 

 basin, and northward on the west side of the Archaean nucleus to the 

 Arctic Ocean, after many variations eastward and westward in its ex- 

 tent through the whole Paleozoic, was at last mostly limited to the 

 region west of the Mississippi ; for here are located all the marine 

 sedimentary deposits of the Interior, formed in later time. 



2. Mountains. — The mountains of the Paleozoic continent were 

 mainly those of the Archaean, — the Adirondack, of northern New 

 York; other heights, in British America; ridges in the line of the 

 Highlands of New Jersey, and the Blue Eidge of Virginia ; probably 

 the Black Mountains of North Carolina ; the Black Hills, Wind River 

 Mountains, and other ridges in the seas of the Rocky Mountain region, 

 etc. The Carboniferous marshes covered a large part of the site of 

 the Alleghanies ; and a sea, in which Carboniferous limestones were 

 forming, a considerable portion — perhaps all but the Archaean 

 heights — of the area of the Rocky Mountains. 



Moreover, after the close of the Lower Silurian, the Green Moun- 

 tain region appears to have been above the sea (pp. 212, 305), and 

 divided the New England or Eastern-border region from the Interior. 

 Consequently, the subsequent progress of the dry land over New 

 England was from the Green Mountain region eastward, as well as 

 from the St. Lawrence southward. In other words, the Devonian 

 beds, which stretch from Gaspe to Vermont, stretch also over much of 

 Maine. But nearly all the interior of New England was probably 

 dry land, after the close of the Lower Devonian, since rocks of the 

 Upper Devonian are confined to the Atlantic border of Maine and 

 New Brunswick. At the close of the Devonian, another mountain- 

 making epoch passed over the Eastern-border region (p. 289) ; and 

 probably the upturning and crystallization of the Devonian and Upper 

 Silurian rocks of New England, as well as of Eastern Canada, Nova 

 Scotia, and New Brunswick, dates from this time. 



3. Rivers. — The rivers of the early Paleozoic were only small 

 streams, such as might have gathered on the limited Archaean lands. 



