
D. MILNE HOME ON THE PARALLEL ROADS OF LOCHABER. 619 
At the next level of the lake, viz., shelf 3, when its waters were discharging 
through Glen Glaster, there was also rock at that co/. But if the blockage 
between Craig Dhu and Bohuntine for Shelf 3 was detritus, there would be no 
difficulty in the gradual erosion and ultimate removal of it, to allow another 
subsidence, viz., to Shelf 4. 
What happened in Glen Roy, according to the view now submitted, is 
not without precedent. Lake Winnipeg, in North America, is about 300 
miles long by 60 miles broad. It now overflows_at its north end into 
Hudson’s Bay, by the River Nelson. But from a recent survey it ap- 
pears, that it formerly discharged from its south end, into the valley of the 
Mississipi. . 
This would be the case, if the waters of the lake stood about 360 feet above 
its present level, provided there was a blockage at the north end, reaching 
to that height above the lake. That the lake had stood at this higher level, 
is attested by the existence of four or five bluffs and terraces, on each side 
- of the lake, one above another, up to a height of 360 feet above its present 
level. Some of these terraces run for long distances,—one for no less than 120 
miles, forming “a continuous and horizontal gravel road beautifully arched, about 
100 feet broad.” 
These may in fact be called the Parallel Roads of Lake Winnipeg. The valley 
of the Minnesota, through which the lake at a former period discharged south- 
wards, affords by its elevated and continuous bluffs on each side, unmistakable 
proof that a river, very much larger in size than the stream occupying that valley 
now, did flow through it from the north. The whole of this region of North 
America is covered by drift to a great extent and depth. Every lake in it 
is surrounded by beaches at high levels, all formed on drift deposits. But the 
peculiarity of Lake Winnipeg is, that whilst it stood at its higher level, it 
certainly overflowed at its south end, and as it sunk to its present level (which 
itaccomplished by successive stages), it changed its overflow to the north 
end. Major WARREN, the most recent surveyor of the district, states, after an 
examination of the River Nelson by which the lake now discharges into 
Hudson’s Bay, that this river “has every indication of being of recent origin,” for 
reasons which he specifies. He adds that “the first material of the bed of the 
new outlet was probably loose drift, so that it was easily removed, and the 
outlet widened and deepened.” From Major WArRREN’s report, it rather appears 
that the summit level between Winnipeg and the Minnesota is a ridge of 
granite,—another feature in which it resembles Glens Roy, Gluoy, and Glaster. 
He adverts to an opinion suggested by-some geologists, that a glacier may 
have moved over the country from the Arctic regions to the lake on the north 
side, and compelled an overflow towards the south. But this theory he 
makes short work of, terming it “an unsupported hypothesis, and barren of 
VOL, XXVII. PART Iv. SA 
