1856.] Physical Geography of North America. 179 



the natural hydrographic basin of Hudson Bay, an area or basin of 

 fossiliferous palaeozoic strata of the upper Silurian, Devonian, and 

 possibly Carboniferous periods. This may be called the Hudson 

 Bay, or Arctic Palaeozoic Basin. 



To the south of the before-mentioned Lawrentine igneous water- 

 shed, and westward from the Atlantic slope to the Rocky Mountains, 

 and even to the great Pacific chain, and probably north-westward to 

 the basin of Mackenzie River, there spreads another still larger palaeo- 

 zoic basin. The south-eastern and best-developed part of this area, 

 from the Appalachians to the plains of Kanzas and Nebraska, en- 

 titled the Appalachian Basin, includes formations of all the palaeozoic 

 periods known to geologists, from the dawn of life upon the globe, 

 to the close of the age of the coal. 



From this brief statement of the two basins, and an inspection of 

 the geological map, it appears that the Appalachian Basin, or that 

 south of the Lawrentian Lakes, was depressed or under water in the 

 earlier palaeozoic periods, while the region north of the Lawrentine 

 watershed was above the level of the sea. But at the close of the 

 Cambrian or older Silurian ages, that great disturbance of the crust, 

 which let the ocean in upon the area of the present basin of Hudson 

 Bay, for the production of the Silurian and later strata, lifted out a 

 part, and shallowed other portions of the sea-bed of the other, or 

 Appalachian Basin, to the south. This is manifested in a break in 

 the sequence of the strata, wherever the older Silurian or Cam- 

 brian, and the later palaeozoic rocks are there recognisable together. 



The first stage, then, in the physical geography of the primeval 

 North America, was the existence of a small northern continent, the 

 southern coast of which was nearly coincident with the northern skirt 

 of the present valley of the St. Lawrence and its lakes. This con- 

 tinent, or nucleus of one, sent forward to the south a long peninsular 

 tract, the vestiges of which we may discern in the hypozoic and azoic 

 belt of the Atlantic slope, stretching from New Brunswick to 

 Georgia. Very possibly other lands lay to the eastward of this 

 region of the Atlantic slope at that early date, and were depressed 

 during some of the earlier oscillations of the crust in this quarter of 

 the hemisphere ; the seeming eastern origin of many of the Appa- 

 lachian palaeozoic strata, to the coal rocks inclusive, is eminently 

 suggestive of the existence in the palaeozoic times, of some such 

 large tract of land, an antient Atlantis, now imder the bed of the 

 western part of the Atlantic. 



The next general movement of the crust, in the region now con- 

 stituting the eastern half of North America, was at. the end of the 

 coal period, manifestly an epoch of very extensive uplift of the con- 

 tinent. This shift of level, and total drainage of the eastern half of 

 the Appalachian sea-bed, caused a large accession to the continent, 

 the new shore of which, if assumed to be coincident with the line 

 which now separates the palaeozoic Appalachian formations, and yet 

 older ones of the Atlantic slope, from the later horizontal cretaceous 



