AND RIDGES. 335 
mark the boundary line between the United States and the British Provinces from 
Lake Superior to Rainy Lake. These valleys all have a northeast and southwest 
bearing, and preserve a uniform parallelism, with a few exceptions, for short dis- 
tances; and these exceptions will generally be found, on investigation, to maintain 
a parallelism with one of the two other systems, or to be complicated by the tra- 
versal of subordinate axes, to be mentioned hereafter. 
The third system of valleys runs north and south, or nearly so, and includes the 
Valleys of Wisconsin River, from near its source to Winnebago Portage; of Red 
Cedar River (Menominie of the Chippewas); of St. Croix River, from the Falls to 
the outlet of Lake St. Croix; of Rum River, from Snake River Portage to its 
mouth ; of the upper two-thirds of Snake River; of St. Louis-River, from the Two 
Rivers to the mouth of East Savannah River; of Bois Brulé River; of Illinois 
River, from Naples to its mouth; of the Wabash, from Darwin to Vincennes, and 
from the Grand Chain to its mouth; of the Mississippi, from.Crow Wing to the 
mouth of Clear-Water River, from the mouth of Root River to that of Turkey 
River, from Savannah to Bear Island, from Keithsburgh to Oquawka, from the 
mouth of the Des Moines to Hannibal, and from “ Grand Tower” to Cape Girardeau; 
and of Red River of the North, from its Great Bend to its entry into Great Lake 
Winnipeg. These valleys are parallel to the basin of Lake Michigan. 
To this list might be added the Missouri River, which maintains a southeasterly 
course from the mouth of Chayenne River to the mouth of the Kansas, and is, 
therefore, parallel to the Mississippi for several hundred miles. The valleys of 
numerous smaller streams might also be enumerated, all maintaining a parallelism 
to one or other of the three great systems of valleys named, and all tending to 
support the opinion that the great structural features of the country are due to 
subterranean movements, acting at different periods on an immense extent of the 
crust of the earth, and with great uniformity during each epoch; and not to local 
disturbances only, or to mere alterations of the surface from glacial or diluvial 
action, however much these agencies may have altered the face of the country. 
As will be seen from the report of details of the geology of the country north of 
the western portion of Lake Superior, a large district has been subjected to dis- 
turbances of a more local character, and at various periods; and that they extended 
into the great valleys named, and gave rise to numerous local variations in the 
strike of ridges and the direction of subordinate valleys. Judging, however, from 
the great degree of uniformity exhibited in the various systems of trap rocks 
exposed along the Lake coast, and as far north as the water-shed, there can be but 
little doubt that the same degree of uniformity and parallelism is maintained 
throughout the whole extent of country southwest of Lake Superior, where trap 
dikes are found to penetrate the metamorphic and more recent sedimentary strata, 
at various points, as far as the Mississippi; and that the various directions of 
subordinate hills and valleys would be found, on examination, to conform to some 
one or other of these systems. 
Relatively, the high ranges and chains of hills, which begin in Canada and cross 
into Minnesota north of Lake Superior, may be termed mountains, although they 
