ANCIENT BEACHES ON THE GREAT DOGr. 



257 



of the changes now taking place in the relations of land 

 and water throughout the Lake Eegion. 



The boulders and slabs of limestone on the low prairies 

 of Eed Eiver and the Assinniboine resting upon lacustrine 

 deposits, were probably brought by ice at a period pos- 

 terior to the Boulder Drift. They are illustrations of the 

 operations of ice at higher lake levels, similar to those 

 occurring at the present time. 



BEACHES AND TERRACES. 



The most remarkable beach and terrace between Lake 

 Superior and Lake Winnipeg, showing an ancient coast 

 line, is undoubtedly that which separates Great Dog from 

 Little Dog Lake on the Kaministiquia canoe route. 



The Great Dog Portage, fifty-five miles from Lake 

 Superior by the canoe route, rises 490 feet above the 

 level of the Little Dog Lake, and the greatest elevation 

 of the ridge cannot be less than 500 feet above it. The 

 difference between the levels of Little and Great Dog 

 Lakes is 347*81 feet, and the length of the portage 

 between them, one mile and fifty-three chains. 



It is stated in Chapter II. that the base of the Great 

 Dog Mountain consists of a gneissoid rock supporting 

 numerous boulders and fragments of the same material. 

 A level plateau of clay then occurs for about a quarter of 

 a mile, at an altitude of 283 feet above Little Dog Lake, 

 from which rises, at a very acute angle, an immense 

 bank or ridge of stratified sand, holding small water-worn 

 pebbles. The bank of sand continues to the summit of 

 the portage, or 185 feet above the clay plateau. The 

 portage path does not pass over the highest part of the 

 sand ridge ; east of the path it is probable that its summit 

 is 500 feet above the Little Dog Lake. 



VOL. II. s 



