16 THE ROYAL SOCIETY OF CANADA 
Glacial Grooves and Striae 
On Hayes river the most northerly glacial markings observed 
were at ‘The Rock’”’ where two sets, probably not very different in 
age, run S. 65° W., and S. 85° W., respectively, while these are over- 
ridden and almost obliterated by a later set running S. 20° E. Much 
of the surface was scored and polished by this last glaciation so that 
its direction and its relationship to the earlier glaciations were quite 
unmistakable, but nevertheless it was not observed on any rocks 
farther south on Hayes river, so that either it did not extend much 
farther south than this point, or it did not move the till or reach 
down to the underlying rock at any of the places examined by me, 
for while a first glaciation will usually score the underlying rock a 
second glaciation will not necessarily do so unless it either moves or 
removes the older till. 
At the outcrops of Ordovician limestone which I examined on 
the Shamattawa river the surface of the rock was everywhere rough 
and weathered, and no glacial markings could be discovered. 
Farther east, on Severn river, two distinct sets of glacial grooves 
and striae were conspicuous, one bearing a few degrees east or west 
of north, and the other and later set bearing S. 60° W. 
Different Periods of Glaciation 
I have elsewhere shown that there were at least three periods! 
during which this country was more or less completely covered with 
ice, namely the Patrician, Keewatin, and Labradorean periods. At 
that time the Keewatin glaciation was thought to be the oldest of 
the three, but further consideration has led me to the belief that the 
Keewatin glacier, at least in its terminal stages, was later than the 
Patrician glacier. In order of time therefore we would have 1st, 
a Patrician Period during which the ice spread out from a centre 
in the country between Hudson Bay and Lake Superior, northward 
into the basin of Hudson Bay, westward across the Hayes and Nelson 
rivers, and doubtless also southward towards Lake Superior and Lake 
of the Woods; 2nd, a Keewatin Period when the ice accumulated 
on a centre west of Hudson Bay and north of the Churchill river, 
and moved southward and southeastward down to and over the basin 
of Lake Winnipeg and the plains of southern Manitoba; and 3rd, 
a Labradorean Period during which the ice moved southwestward 
across the southern portion of the basin of Hudson Bay as far as Lake 
Winnipeg, overriding the marine deposits in the bottom of the Bay 
and shoving a certain portion of them to and over the country to the 
! Hudson Bay Exploring Expedition, 1912, by J. B. Tyrrell. 22nd Report 
Ontario Bureau of Mines, Toronto, 1913. 

