﻿1851.] 



RICHARDSON ON NORTH AMERICA. 



213 



averages a little more than a foot in the mile. Six hundred miles of 

 the western part of this slope is nearly regular in its descent, being 

 what is named "prairie land," or "rolling prairie," — the rest is va- 

 riously excavated. 



In proceeding eastward from the Rocky Mountains in the southern 

 half of the continent, nothing deserving the name of a mountain- 

 chain is met with, until we come to the Alleghanies or Apalachian 

 chain, which running parallel to the Atlantic coast and near it, for a 

 thousand miles from Georgia to the promontory of Gaspe in the Gulf 

 of St. Lawrence, has a course of North 46° East, and consequently 

 forms an angle of 72° with the axis of the Rocky Mountains. 



Between the Apalachian chain and the Rocky Mountains lies the 

 great valley of the Mississippi, having a width of 30° of longitude, in 

 which space the Ozarh Hills, lying to the westward of the river, are 

 the only eminences* having a mountainous character; but, were the 

 general slope extended without excavation across the valley, their 

 summits would not rise above its plane. The axis of these hills is 

 parallel to that of the Alleghanies. 



On the north side of the St. Lawrence basin, there is a formation 

 of gneiss, granite, trap rocks, and conglomerates, flanked on both sides 

 with Silurian deposits, which does not rise into a mountain-chain, but 

 which, running nearly parallel to the line of great lakes, forms the 

 brim of the basin and the watershed between it and Hudson's Straits 

 and Bay and Lake Winipeg. From Lake Superior northwards the 

 western boundary of this formation takes a course of North 30° West, 

 and maybe traced for 1600 geographical miles up to Coronation 

 Gulf in the Arctic Sea ; and it consequently inclines, though slightly, 

 towards the axis of the Rocky Mountains, the intervening space nar- 

 rowing considerably as we advance northwards. 



This formation is hummocky rather than hilly, and its summits do 

 not pass beyond the plane of the general eastern slope, or at least 

 very rarely, although, when seen from the lake-basins, they occa- 

 sionally assume an alpine character. 



Of the forty degrees of latitude between the Gulf of Mexico and the 

 Arctic Sea, the valley of the Mississippi occupies about one half, and 

 the river has a descent from its source in Lake Itasca of 1500 feetf. 

 Now the lake lies between 500 and 600 miles from the highly inclined 

 base of the Rocky Mountains, which has an altitude of 2500 feet, and 

 consequently one-third of the descent, were it equable, being accom- 

 plished at Lake Itasca, the height of the district in which the river 

 rises would be 1600 feet. The sandy eminences {hauteurs de terres) 

 near the lake, do not in fact rise perceptibly above this height. 



Proceeding northwards from the sources of the Mississippi, we have 

 a space between the 46th and 56th parallels, in which two great rivers 

 flow transversely and cross the low intermediate granite and gneiss 

 formation above-mentioned in their course to Hudson's Bay. 



* The highlands in the northern counties of the State of New York are outliers 

 of the Alleghanies similar to the projection towards Illinois at the south end of 

 the chain, making, with the Ozarh Hills and Lake Superior rocks, fragments of a 

 basin. 



f More exactly 1490 feet. 



