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BULLETIN OF THE NATURAL HISTORY SOCIETY. 
will be noticed, further, that the directions in which all these streams 
tlow, and in which they enter one another, are fully consistent with 
this interpretation.* 
Down to the ^orth Pole Branch there are few hills near the river, 
and the first lofty hills appear just below that branch, on both sides 
of the river. They appear to be well up towards 1,000 feet above the 
water and to form part of a ridge crossing the river and separating 
the North Pole from the Lower North Branch. This range is exactly 
on the hinge line described in the preceding note. Eastward of this 
ridge the country appears to fall away to a great plateau, a true pene- 
plain, which slopes off to the sea. 
Just above the seventeen-mile bend, the falls and rapids suddenly 
begin again, and the river falls over crystalline ledges for half a mile, 
at the foot of which is a typical small gorge and pool. Here again the 
valley seems typically post-Glacial, and although I did not trace out a 
pre-Glacial valley, I suspect that one exists in the direction shown by 
the shading on the map. Below this the river is not so rough for a 
mile, this part being, doubtless, the ancient valley; but at Island Rock 
begins the worst series of rapids and falls on the entire river. Here 
the river falls over rocky ledges, into which it has cut small gorges, a 
very typical example of which occurs at the foot of the series. The 
whole aspect of this part of the river bed is typically post-Glacial, but 
yet it is very difficult to interpret it in that way. The valley here is 
V-shaped, with the walls of great irregular angular masses of rock, 
cut by actual measurement about 250 feet below the surface of the 
great rolling plateau, or peneplain, of which this region is constituted. 
There appears to be no room in the valley for a pre-Glacial channel 
around these present ledges and falls, and yet it is equally difficult to 
imagine that it lies outside of the present valley ; for the amount 
of work required to cut down the present valley to such a depth in 
such hard rocks appears too great to have been accomplished in post- 
Glacial times. If, however, this has happened, the pre-Glacial channels 
would have run in one of the directions indicated by the shading on 
the map. More detailed study than I could give the question will, no 
doubt, settle it. At Libbys Brook (566 feet above the sea), which 
enters the main valley by a lofty post-Glacial fall, the character of the 
• It is quite possible that the North Pole Branch emptied earlier at the angle to the 
-eastward of its present mouth, where a small brook now is. 
