CARBONIFEROUS PERIOD. 365 



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 Eocky Mountain range, may be of the same age. 



As 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 

 central coal area stood nearly at a common level, — that the region 

 was a vast plain, with, at the most, only gentle undulations in the 

 surface breaking its continuity, and with the higher land mainly 

 over the Azoic and Silurian lands to the north. There were no 

 Appalachians, for this very region was a part of the great coal- 

 making plain ; there were no Eocky Mountains, for these, as the 

 Carboniferous limestones prove, were mainly under the sea. 



Being thus level, there could have been no great Mississippis, and 

 no sufficient drainage for the continent ; and the wide plains would 

 have necessarily been marshy, and spotted with shallow lakes. 



Eastward there was another similar level area, in Ehode Island 

 and eastern Massachusetts, which probably extended northwest- 

 ward over the Nova Scotia Coal field to the interior of New- 

 foundland, covering more or less of Massachusetts Bay, eastern 

 Maine, Nova Scotia, New Brunswick, and the Gulf of St. Lawrence. 

 The continent in that direction, therefore, had for the time its 

 present enlarged limits, and probably spread even beyond. Near 

 the present mouth of the St. Lawrence must have emptied the prin- 

 cipal river of the continent ; for in the back country at that era 

 there were mountains of moderate elevation, to pour waters into 

 such a stream, — the Azoic heights of northern New York and Canada. 



Over these marshes, then, grew the clumsy Sigillarice and Catamites, 

 and the more graceful Lepidodendra and Conifers, with an under- 

 growth of ferns, and upon the dry slopes near by, forests of Lepido- 

 dendra and Conifers ; and the luxuriant growth was prolonged until 

 the creeping centuries had piled up vegetable debris enough for a 

 coal bed. Trees and shrubs were expanding, and shedding their 

 leaves and fruit, and dying, making the accumulation of vegetable 

 remains. Islands of vegetation, like those now occurring in India, 

 may have floated over the lakes and contributed to the vegetable 

 debris. Stumps stood and decayed in the swamps, while the debris 

 of the growing vegetation, or detritus borne by the waters, accu- 

 mulated around them, and their hollow interiors received sands, 

 or leaves, or bones, or became the haunts of reptiles, as was their 

 ehance. 



Where the floating islands and other vegetation were drifted out 

 into salt-water bays, the coal-bed accumulations might contain 



