154 LABRADOR 
Bowdoin Canyon was so named by Cary and Cole, who 
discovered it in 1891. Issuing from the basin at the foot 
of the great cascade, the river zigzags in half-mile courses 
to the east and southwest until it finally issues into the main 
valley. The distance from the falls to the mouth of the 
canyon is eight miles in a straight line, but by the river 
it is more than twice that distance. The canyon is cut 
sharply and nearly perpendicularly out of the granites 
and other crystalline rocks to a depth of over five hundred 
feet below the general surface of the plateau. The zigzag 
courses of the gorge conform with the directions of two sets 
of jointage planes, which split the granites into huge blocks 
in the area below the falls. The cracks appear to influence 
the direction of the river courses, and to have greatly as- 
sisted the water in clearing out the gorge. The canyon 
is probably a new valley excavated by the river since the 
Glacial Period. The ancient river which, in pre-Glacial 
time, flowed down the main valley seems to have been 
diverted by dams of glacial drift and perhaps by local 
changes of level, so that it now flows on the surface of the 
plateau to the north of the old valley. On reéntering the 
old valley with such a tremendous fall, the river has cut 
out the canyon in a comparatively short period of time. 
The break in the surface of the plateau is so sharp that an 
approach to within a few yards of the edge may be made 
without any indication of its presence, the first warning 
being the hoarse roar of the rapids far below. Across its 
top the gorge rarely exceeds a hundred yards; at the bottom 
the river is confined to a width of a hundred feet. The 
difference in level between the water in the basin and that 
issuing into the main valley is two hundred and sixty feet, 
