QUATEKNARY BEACHES IN RED RIVER VALLEY. 261 



track for Indians on the east flank of the Eicling Mountain. 

 Probably these ridges are found close together, at the foot 

 of the Pembina Mountain, where no less than four dis- 

 tinct steps occur close together near the sources of 

 Scratching Eiver.* The summit of these steps may be 

 the plateau whose altitude was ascertained by Dr. Owen 

 to be 210 feet above the prairie level, and the first steps 

 may be continuous with the Big Eidge, limiting the level 

 prairies of Eed Eiver and the Assinniboine. 



The prairies enclosed by the Big Eidge are every- 

 where intersected by small subordinate ridges, which 

 often die out, and are evidently the remains of shoals 

 formed in the shallow bed of Lake Winnipeg when its 

 waters were limited by the Big Eidge. Many opportu- 

 nities for observing the present formation of similar shoals 

 occurred in Lake Manitobah, St. Martin's Lake, Lake 

 Winnipeg and Dauphin Lake. These, when the lakes 

 become drained, will have the form of ridges in the level 

 country then exposed. Indeed it may be said that the 

 region between Dauphin Mountain and Lake Manitobah 

 in the direction of Ebb and Flow Lake and south of that 

 body of water, is but recently drained, or still in process 

 of draining, being removed from the surface of Ebb and 

 Flow Lake, by a very few feet and covered with water to 

 a large extent in the spring. At present it consists of 

 marsh, bog and ridge, in continued succession. When 

 completely drained, the country will resemble the present 

 prairies of the Assinniboine, with the gentle rich depres- 

 sions, and the low dry gravelly ridges. 



The Pembina Mountain is par excellence the ancient 

 beach in the valley of Lake Winnipeg. Dr. Owen thus 



* The steps are shown on Sheet 2 of the large map accompanying the 

 Reports on the Assinniboine and Saskatchewan Exploring Expedition. 



s 3 



