248 R. BELL — DIFFERENTIAL RISING OF LAND ALONG BELL RIVER. 



in the surrounding country the tamaracks and black spruces in the 

 isolated swamps are perfectly healthy, and the above explanation seems 

 to be the only way of accounting for the dying condition of those in the 

 swamp at the head of the lake. 



OTTAWA RIVER. 



Change in its outfloio and causes therefor. — The strongest evidence show- 

 ing a differential elevation of the land toward the northeast is to be found 

 in the total stoppage of the former, northward outflow of Grand lake at 

 its northern extremity, by which the waters of the Ottawa above it for- 

 merly passed down Bell river to Hudson bay. Although the outflow of 

 this lake has been affected by a change of level of only a few feet, it has 

 had the effect of shifting the position of the watershed of the large area 

 comprising the hydrographic basin of the Ottawa river above the new 

 outlet of Grand lake, which measures about 90 miles eastward and 60 

 miles south westward. The evidence of the former discharge of Grand 

 lake from the extremity of its northern arm is very striking, and one 

 almost wonders why the lake does not still flow out that way ; and prob- 

 ably it would resume its outflow by this old channel if its new outlet 

 were dammed up so as to raise the present spring level only a few feet. 



When the full volume of the Ottawa was flowing north there was 

 probably a strong current through the Long narrows in that arm of 

 Grand lake and also through Mink narrows, about one mile further 

 north, in the same arm ; but beyond these contractions the valley pass- 

 ing over the height-of-land widens out all the way to the northern 

 extremity of Christopherson lake, a distance of 22 miles. In this wide 

 part the current was checked and great quantities of sand were deposited 

 in the still water. Bye and bye the sand choked the northward flow of 

 the river and at the same time the rising water of Grand lake to the 

 southward found a new outlet to the west at Snake creek over the low 

 and almost horizontal ridge of gneiss which had heretofore kept the lake 

 up on that side. Along the foot or western slope of this ridge and at a 

 considerably lower level than that of Grand lake a rock}^ stream al- 

 ready flowed, which had heretofore formed the headwaters of the Ottawa. 

 This channel, which was now greatly increased by the accession of all 

 the waters flowing into Grand lake, zigzags among the gneiss ridges, but 

 follows a general westward course all the way to lake Temiscaming. 



By the washing away of the surface materials along its course the 

 channel of the new outlet (Snake creek) would become rapidly deeper ' 

 and the relief thus afforded at the northward outlet would cause it to 

 cease to flow altogether, and this low barrier of silt now became the 

 height-of-land between the waters of Hudson bay and the Saint Lawrence. 



