24 THE ROYAL SOCIETY OF CANADA 
Some of the reasons which suggest themselves to account for the 
difference in size and character of the two valleys are as follows:— 
The valley of Nelson river was originally excavated by a stream 
no larger than, and perhaps not as large as the stream which at the 
same time flowed in the valley of Hayes river, and as the soft materials 
in which the two valleys were excavated were not very dissimilar 
in character the valleys themselves undoubtedly presented the same 
general characteristics, which were those of a stream without falls 
or serious rapids winding between or beside alluvial flats that rose 
by regular or terraced slopes to the level of the adjoining plain. Hayes 
river is quite competent to carve out the valley in which it now flows, 
while Nelson river is much too large for such a duty, and therefore 
in the lower portion of its valley which we are now considering it 
was once much smaller than it is at present. It may be that the over- 
flow of Lake Winnipeg did not reach this portion of the valley of 
Nelson river at that time, but found its way to Hudson Bay by some 
other channel, and that we are here dealing with the lower valley of 
the united Grass and Burntwood rivers which flow from the west 
into the west end of Split Lake. These two streams together drain 
an area of 1,300 square miles west of Split Lake, and their waters 
united into one river would doubtless have been competent to cut 
out the original Nelson valley. We have already observed that frag- 
ments of the Mission Terrace, 30 feet above high tide level, occur in 
protected places in the lower part of the valley, where the present 
river is not able to reach and destroy them, and therefore it would 
appear probable that the smaller river, which we may refer to as the 
Burntwood river, occupied the valley down to the time of the Mission 
beach at least, and perhaps even to the time of the 10 feet beach. 
Then the volume of water was greatly increased, possibly by the junc- 
tion of the stream flowing from Lake Winnipeg with the Burntwood 
river, and the enlarged stream adopted the valley of the latter river 
and followed it to Hudson Bay. At the present time it is ie 
engaged in widening and deepening that valley. 
The naked precipitous cliffs of clay descending to the edge of 
the water are themselves sufficient evidence of the rapid erosion which 
the river is performing, but in addition a little bit of evidence was 
found which has a decidedly human interest. On the north end of 
Gillam Island is a wooded terrace which is bounded towards the 
north by a steep cliff 25 feet high descending to the water which is 
deep enough for a small ship. Here Ben Gillam brought his ship 
in the summer of 1682; on the terrace he built his fort and spent the 
winter of 1682-3, and in the spring of 1683 the fort was burnt down 
and abandoned. Most of its site has been washed away, but a little 
