58 G. M. DAWSON — GLACIAL DEPOSITS OF SOUTHWESTERN ALBERTA. 



McConnell,* it may be added that the same principal Avide terrace there 

 shown by him enveloping tlie morainic ridges was particularly observed 

 by me in 1881 at a point about six miles farther up the valley, with an 

 elevation of about 4,200 feet. In my note-book it is thus described : 



"This (bench) is several miles wide and occurs on both sides of the river. It is 

 sandy, gravelly or stony on the surface and is not a river-terrace, but must have 

 been formed when water stood against the mountains at its level, the river from 

 the pass no doubt bringing down the material. Its level at Morley is about 4,030 

 feet, giving a slope upward toward the west of nearly 30 feet to the mile." 



Reviewing the sections afforded by Bow river, the principal facts shown 

 by them are summarized as follows by Mr McGonnell : 



" From the mountains east to Calgary the glacial deposits are entirely 

 of western or local origin and consist of boulder-clays passing occasion- 

 ally into gravels and overlain in places b}^ fine glacial clays and silts. 



'• East of Calgary the rolled gravels and associated clays and sands 

 which underlie the boulder-clay are also of western origin, and probably 

 represent, for some distance at least, the wash of streams flowing east- 

 ward from the Bow River glacier. 



" From Calgary to a point between Blackfoot crossing and Medicine 

 Hat the boulder-clay contains western, local and eastern material, the 

 former greatly predominating at first, but gradually diminishing in rela- 

 tive quantity toward the east until it is entirely replaced by the latter, 

 so far at least as it is capable of recognition. 



" The third zone extends from a point above Medicine Hat eastward, 

 and in it the boulder-clay, so far as known, is entirely of eastern or of 

 local origin. 



" The boulder-clays of the middle and eastern zones graduate into each 

 other, but the relations between the middle and western zones are less 

 clearly defined. At Calgary, the most westerly point at which mixed 

 boulder-clay was found, it is underlain by a gravelly clay bed of western 

 origin similar to certain phases of the western boulder-clay and undoubt- 

 edly a continuation of it, modified to some extent by water. Tlie inferior 

 position of this bed shows that part at least of the western drift was 

 deposited before the advent of any material from the east; but whether 

 the whole of it was laid down prior to tlie eastern invasion or not I was 

 unable to ascertain." 



Summary and Discussion. 



In concluding this paper, which, because of a wish to present ol)served 

 facts rather than any theoretical deductions, has attained considerable 

 length, a few words may be added on the more obvious conclusions to 



*Cf. ; also op. cit., p. 146 C. 



