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



of greatest change of level in opposition to the current; and we do find 

 these conditions exhibited in a striking manner in such tributaries and 

 in proportion to the opportunities afforded for the action of the supposed 

 cause. Two cases in point will suffice for illustration. One of these is 

 a branch which enters the main stream at the head of Taibis lake, from 

 which a long still-water stretch extends to the northeast. The other is a 

 river coming from the southwest and entering the western extremity of 

 Mattagami lake. It may be named the Mattagami river. There is no 

 parallelism in the two sides of these affluents. On the contrary, they 

 are broken up into irregular peninsulas, bays, lagoons, inlets, or culs-de- 

 sac, with islands here and there, these peculiarities being just such as we 

 would expect to find if the water flooded back over a low but slightly 

 undulating clayey surface. The accompanying outlines (plate 23, figures 

 1 and 2) from track-surveys of these two streams will illustrate the con- 

 dition just described. 



MATTAGAMI RIVER. 



If the flooded condition seen in the Mattagami river be due to a very 

 slight tilting of its bed in that direction, we should find a corresponding 

 lowering of the water at the opposite end of the lake. Accordingly, on 

 the north shore, about 5 miles from the east end, very conspicuous old 

 water-marks are seen on perpendicular red granite rocks up to a height 

 of 13 feet above the summer level, while the annual spring rise does not 

 amount to more than about 5 feet. 



At the foot of nearly all the low falls or chutes on this part of the river 

 it was found by sounding that the water was considerably deeper than 

 elsewmere, usually ranging from 50 to 80 feet. Mention has already been 

 made of certain rocky narrows in this stretch which terminate in sudden 

 widenings of the river. In these expansions, close to the entrance of the 

 accompanying narrows and in line with the axis of the stream above, the 

 water was always found to be very deep. There is little doubt that when 

 the river flowed at a lower level these narrow parts were the sites of 

 strong rapids and the deep-water expansion below each of them repre- 

 sents a flooded condition of the pool and widening which nearly always 

 occur at the foot of such rapids in any river. If the water were now to 

 be lowered by a slight increase in the grade of the present stream we 

 would no doubt have chutes and rapids at these narrows, while the 

 amount of fall in the low chutes which still remain would be increased. 



NOTTA WA Y RIVER. 



A short distance below Mattagami lake the Nottaway expands into 

 a sheet of water 30 miles in length, running north and south, called 

 Soskamika (= "slippery shores ") lake. The soft level clay land at its 



