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PKOCEEDLNGS OF THE GEOLOGICAL SOCIETY. 



[Apr. 10, 



diately afterwards, in the course of the ascent, true granite occurs, 

 and after several alterations schistose flags reappear at Upper Island 

 Portage, but now dipping at a high angle to the north-west. 



From the falls to the Dog Lake the ascent of the river pursues a 

 northerly course, crossing the beds obliquely by a succession of 

 minor falls, giving rise to scenery of unequalled beauty. At the 

 Dog Portage another sudden rise takes place in the water-level ; for 

 the rocky high grounds which, for a long way below, have been 

 skirting the river at some distance, forming, as it were, the limits 

 of a wide valley, here converge and form a granitic barrier across 

 the river, the summit of which is about 719 feet above Lake Su- 

 perior, and 440 feet above the river at the lower end of the portage, 

 but only 140 feet above the lake-level at the upper end, thus making 

 a rise in the water-level of 297 feet in the short distance of two and 

 a half miles. As the portage-road passes right over the top of this 

 hill and leads to a point in the lake far from the exit of the river, 

 the nature of the rock at the falls which produce this sudden 

 change in level could not be examined, but the mass of the hills 

 seems to be granite. Although this is not the highest point of land 

 over which we passed during the route, still it is probable that this 

 hill is as high as any portion of the rocky axis of the country ; as 

 those along the lake are inferior to it in elevation, while the 

 ascent which is made after leaving the upper end of Dog Lake is 

 through a swampy country covered with drift. In fact, after leaving 

 Dog Lake, until a considerable descent has been made to the west, no 

 rock is exposed, the whole summit-level being covered with a thick 

 deposit of drift. 



From the Lake of the Thousand Isles, where the rocky flooring of 

 the country is again uncovered, until Sturgeon Lake is reached, the 

 descent is very slight, and the route follows a chain of small lakes, 

 which are in most cases detached from one another, being sepa- 

 rated by rocky barriers over which the canoes and cargoes are 

 carried. 



In many cases the lakes are at exactly the same level at each end 

 of the portage, and the greatest difference between the two ends 

 of any of these portages is only about 35 feet, so that the total 

 descent in this part of the route cannot amount to very much. This 

 chain of lakes may, in fact, be considered as occupying a line parallel 

 with the summit of the watershed, and the country in which they 

 lie is almost wholly composed of granite, occurring in broad round 

 eminences, nowhere rising to 100 feet above the level of this half- 

 drowned country. It is probable that this granitic belt is expanded 

 considerably where the old portage-route crosses it, and that the 

 whole chain of lakes between Lake Easiganagah and Sturgeon Lake 

 lies within it. It is this belt which will form the great obstacle to 

 the formation of any kind of road across this watershed. 



From Sturgeon Lake to Bad liiver there is a considerable descent 

 to the south, which forms the only exception to the general north- 

 westerly descent of the waters to Rainy Lake. 



From the Lake of the Cross to Lake Namuean the descent is rapid, 



