﻿1861.] 



HECTOR KOCKY MOUNTAINS, ETC. 



Judging from the altitudes at which erratics are found to be di- 

 spersed, the continent must have been depressed at that period 

 beneath a sea in direct connexion with the Arctic Ocean to the 

 depth of nearly 3000 feet ; and since then, during its gradual emer- 

 gence, this region of North America has received its present form of 

 surface by denudation, — first, as effected on seacoast-lines, and lat- 

 terly by the coast-lines of great inland lakes, which, it will be shown, 

 though still existing, were previously of much greater dimensions. 



The superficial deposits during and posterior to the Drift are so 

 different on the opposite sides of the Rocky Mountains that they 

 must be treated of separately, whilst those anterior to that epoch 

 will be found to have a common character. 



Terraces of the Lake Superior Basin. — In ascending the Kaminis- 

 toquoia River for a considerable distance above the Kakabeka Falls, 

 the country is covered by a deposit of red marl-earth which forms 

 the high terraces of the river. Thus opposite to the mouth of White 

 Fish River there are three distinct terrace -levels of 20, 60, and 90 

 feet. At some distance back from the river still higher terraces 

 occur, belonging to this class of deposits, which must be considered 

 as of more recent age than the true drift. Sir William Logan de- 

 scribes one at the height of 331 feet above Lake Superior. The 

 great deposits of sand and gravel which rest on the highest levels of 

 the axis, and are first met with at Dog Portage, belong, I think, to 

 the period of the Drift, and will be referred to in the next group. 



Superficial Deposits of the Central Plateau. — The steppes of this 

 great slope may be naturally divided into three groups having dif- 

 ferent ages and circumstances of deposition, and boldly marking three 

 distinct Prairie-levels. (See Sect. No. 2, PI. XIII.) To the most re- 

 cent of these belong the low prairies which surround Lake Winnipeg 

 and the lakes of that group, including the marshy country to the west 

 of Manitoba Lake. This forms the First Prairie-level. In the vicinity 

 of the Red River Settlement, its composition is of argillaceous marl, 

 with a deficiency of sandy matter, and it is invariably stratified 

 in thin layers. Underlying this at various depths from the surface, 

 is a bed of stiff clay, which forms tbe immediate margin of the river 

 at many places. The upper layers of this deposit contain leaves and 

 fragments of wood and reeds, and the whole is undoubtedly a fresh- 

 water deposit, indicating a time when the Winnipeg group of lakes 

 covered a much more extended area than at present, the gradual 

 deepening of the rocky channels through the eastern axis having 

 increased the drainage in modern times. 



The surface of this deposit is about 75 to 100 feet above Lake 

 Winnipeg, but it slopes gradually from the west, and at Pembina 

 Mount, near St. Joseph, is at least 100 feet higher. To the east of 

 Red River, in descending the Winnipeg River, two well-marked 

 levels were observed which belong to the group of extended lake- 

 deposits. Thus below the Seven Portages that river flows through a 

 smooth channel, and the banks are composed of a white marl-earth • 

 the river being at first only slightly depressed, but soon from its 

 rapid descent, while the level of the deposit remains the same, the 



