OBSERVATIONS ON SUPPOSED GLACIAL DRIFT. 259 . 



Oue hundred and twenty miles •nest of Lake Winnipeg the 

 Buccessive steps or terraces of the Hiding and Duck IVlouutains rise 

 in well-defined succession on the south and south-western slopes ; 

 but on the north-east and north sides they present a precipitous 

 escarpment more than 900 feet in altitude, or 1000 feet ahove L;ike 

 "Winnipeg, or IGOO feet above the sea; uhile Lake Traver.-c, which 

 sends water during floods to the Eed Kiver of the north as well as 

 to the Mississippi, is only 906 feet above the same level ; and from 

 10 to 15 miles west of Lake Traverse and Big Stone Lnke (9G0 leet 

 above the sea) is the abrupt escarpment of the Coteaux des Prairies, 

 whoso summit is 1000 feet above them. " 



Illustrations of a precipitous escarpment on one face, with gentle 

 sloping plateaux separated by terraces on the otlier side, might be 

 greatly multiplied ; they are indeed the common feature in the 

 scenery of the basin of Lake "Winnipeg, west o( that lake ; and, with 

 a single known exception, mentioned bv Dr. Ilectoi*, the precijiitous 

 escarpment faces the north-east or th.e north, and the terraces and 

 plateaus the south or south-west. This feature is also observed in 

 all the outliers in the great prairies and plains of the basin of Lake 

 Wiuuipego The terraces of Lake Supeiior and the escarpments, 

 with their corresponding terraces in the Lnke Winnipeg basin, con- 

 sidered in relation to the driftless area in Wisconsin, point to the 

 former existence of great glacial lakes, as i^uggested by J^ir. Jamiesou 

 to explain the origin of the Parallel lloads of Glen Koy. The clean- 

 cwept floor of the level country at the foot of the great escarpment 

 of the Riding, Duck, and Porcupine Mountains, in which Lake 

 Winnipeg and its associated lakes lie, indicates the boundary of a 

 vast glacier, which excavated their basins and left its di it- beds on 

 the prairie country even as far as the south branch of the Saskat- 

 chewan, where I observed the forced arrangement of slabs in wn- 

 stratijied clay in 1858. 



§ 5. Anchor-ice — Eizcavation of Lake-hasins. 

 It has been frequently stated that a difficulty arises as to the 

 ■modus operandi by which a moving glacier can excavate lake-basins. 

 May not the manner in which stratified rocks, at least, over which 

 a glacier may be moving, be involved in its mass in the form of 

 slabs or mud, constituting dirt-beds, be partially explained by tha 

 phenomena attending the formation of ' anchor-ice ' ? It is no 



• The Cyprus Hills, Quart. Journ. Geol. Soc vol. xvii. p. 399. 



