534 
BULLKTIN OF THE NATURAL HISTORY SOCIETY. 
water-level, extends from the right-angled bend of the North 
Branch through to join the gorge of the combined stream, as 
shown upon the map, and this valley slopes to the eastward, as 
shown conclusively by the little stream now in its bottom. It 
would certainly seem that these two latter-described valleys, with 
their rocky bottoms at the same level, are of the same age and 
origin. The problem now before us is, therefore, a double one, 
for it includes an explanation not only of the meeting of the two 
rivers midway in the same gorge, but also of the formation of 
and other valleys. 
There are two possible explanations of the meeting of two 
rivers in one straight gorge, — first, that it is merely a coincidence, 
and second, that the gorge was formed and occupied originally 
by a single stream. The chances are immensely against the 
first supposition, and in favor of the second. If, in the present 
case, it is possible to combine the latter supposition with an ex- 
planation of the other valleys, then it will receive the strongest 
confirmation. I believe such a consistent explanation of all the 
phenomena together is possible. I must admit that it is not with- 
out its difficulties, and it is very likely that a more thorough 
examination of the region, especially down the river, where my 
knowledge is especially weak, may require its modification. But 
I offer it as a hypothesis fairly consistent with the facts that are 
known. 
The probable origin of the Forks and Gorges may be express- 
ed in a series of stages. 
First. Originally the two branches of Sevogle did not come 
together in this region at all, but flowed independently north- 
eastward as indicated in the earlier note on the Northumbrian 
Rivers (Note 93). 
Second. In later times, under the influences of geological 
causes, a newer river worked back northeasterly from the North- 
west Mirimicln until it intersected the valleys, first of the South, 
then of the North Branch. Thus originated the main Sevogle 
and part of its North Branch, and it was this river which occupied 
the “ old valley ” of the map (A of Diagram). At this time the 
junction with it of the South Branch lay more to the southward, 
outside the limit of the accompanying map, where the South 
