Geoloyy of Mattawa and Othin^a Valleys. — Taylor. 117 
final. But so far as the}^ go they not onl^y add nothing to the 
marine hypothesis, but the presence of the Deux Rivieres kame 
deposit, which appears to have been the latest noticeable 
phase of deposition at that place, suggests rather the hypoth- 
esis of a glacier dam. The absence of silt or clay overlying 
the sand on the lower part of the slope proves that the latter 
was not long submerged beneath still water after it was un- 
covered by the retreating ice. The Mattavva and Ottawa val- 
leys are troughs in the ancient peneplain of the region and 
they are comparatively narrow and deep. It is impossible to 
deny that if a great sheet of land ice moved over this region 
from the noi'th or north-northeast, as the strije indicate, 
there may have been a short period when the ice blocked the 
Ottawa valley by filling it up for some distance east of Deux 
Rivieres and resting its front against the southern highlands 
below that place. The. valleys to the west and possibly also 
for a short distance north above Mattawa may have been 
temporarily open water. But this condition would last only 
a short time at most. Perhaps this supposition explains the 
absence of stronger shore lines and the general absence of 
still-water sediments at high levels north and east of Mat- 
tawa, and it may be that the faint, doubtful shore lines and 
the thin silts south of Mattawa are in reality the remains of 
such short-lived still waters. The great valley of the river 
Du Moine reaching far to the north ofi'ers an appropriate 
channel, both as to position ;ind direction with reference to 
ice-motion, for a great lobe or tongue of ice that may have 
formed a dam below Deux Rivieres. About two miles east of 
Mackey stride were found running S. 20° and 25*^ W. (mag.). 
A little north of Mattawa on the west side of the river they 
bear nearly south (the direction here was not measured by 
compass). One and a half miles northwest of North Bay fine 
specimens of strite were found close to the railway track and 
the predominant direction of the stronger ones is about S. 18*^ 
W., with a few running .5^ to 10° east of south. No strije 
were seen at the other places named. It is perhaps a signifi- 
cant fact that the scoured vallej^s east of Deux Rivieres and 
Mackey are just where the front of the Du ^Nloine ghicier 
would be at one stage of its retreat. These ideas, however. 
are not offered as conclusions which can be clearly affirmed 
