CARBONIFEROUS AGE. 355 



When the era of the Coal-measures had fairly set in, the great 

 Interior region of the Continent, even from the eastern limits of the 

 Appalachian region to the western borders of Kansas and Nebraska, 

 as the extent of the Coal-formation shows, slowly emerged ; and the 

 continent then, for the first time, extended from the remote Arctic 

 zone, south to Alabama. West of Kansas, there were limestones of 

 the Coal -measure era in progress, instead of coal-beds ; and these 

 indicate that the old sea of the Interior region still covered the slopes 

 and summits of the Rocky Mountains ; and over these meridians the 

 waters may have connected with the Arctic ocean. The limestones 

 of Point Barrow, at the farther extremity of the Rocky Mountain 

 range, may be of the same age. 



This emergence, giving so great extent to the young continent, was 

 not complete until the first of the great beds of vegetable debris 

 began to form. Then North America, within the limits stated, was 

 one vast forest, except where fresh waters lay too deep for forests to 

 grow ; and the lakes probably had islands of shrubbery and forest 

 vegetation floating over the waters, as is now true of some of the 

 tropical lakes of India. 



Since single coal-beds in the earlier part of the series appear to 

 have had a very wide range, it is safe to conclude that the great In- 

 terior region had nearly a common level, — that it was a vast plain, 

 with, at the most, only gentle undulations in the surface, and with 

 the higher land mainly over the Archaean and Silurian lands to the 

 north. There were no Alleghanies ; for this very region was a part 

 of the great coal-making plain : there were no Rocky Mountains, for 

 these, as the Carboniferous limestones prove, were mainly under the 

 sea. The Appalachian region and the Interior basin, both east and 

 west of the Mississippi, were merged in one great continental basin, 

 all making together one nearly level country, the low Cincinnati ridge 

 being the only land west of New York that projected above the level 

 of the marshes. Being thus level, there could have been no great 

 Mississippi or Ohio ; the continent would have had no sufficient drain- 

 age, and the wide plains would necessarily have been marshy, and 

 spotted with shallow lakes. 



This Continental basin, as stated on page 146, was separated from 

 the Eastern-border region, by the Green Mountains, — a range which 

 had stood as a low barrier between New England and New York, 

 from the close of the Lower Silurian. Both the Nova Scotia Coal- 

 measures and those of central Pennsylvania are almost destitute of 

 true marine fossils ; and hence the true raised border of the continent 

 was some miles, or scores of miles, to the eastward of the most eastern 

 Carboniferous limits. The Nova Scotia and New Brunswick beds 



