372 
The American Geologist. 
June, 1896 
the till exhibits elsewhere, it has faint traces of bedding in 
thin and nearly horizontal layers of sand or laminated clay, 
while yet the chief mass of the deposit consists of inter¬ 
mingled clay, sand, gravel, and boulders, having, with the ex¬ 
ception of the obscure bedding, all the characters of typical 
till. 
Both these criteria indicate that the superficial portion of 
the till was contained in the ice-sheet and was therefore ex¬ 
posed to leveling and partial stratification when its deposition 
took place in glacial lakes on the border of the retreating ice. 
Observations of Sublacustrine Till. 
Lake Agassiz. Large tracts on each side of the flat valley 
plain of the Red river of the North, which was the bed of the 
glacial lake Agassiz, consist of till, having the very smooth 
contour and slight stratification here noted. Such deposits of 
normal sublacustrine till also occupy extensive tracts adjoin¬ 
ing lakes Winnipeg and Manitoba and in the vicinity of the 
city of Winnipeg, where the water of lake Agassiz, shown by 
the altitude of its east and west shores, was 500 to 600 feet 
deep when these tracts were first relinquished by the ice-sheet 
and covered by the glacial lake. The position of the stratified 
silt and clay of the Red river valley, in a belt along its axial 
lowest part, shows that these sediments were chiefly fluvial, 
being supplied by streams flowing northward along this 
avenue of drainage after the glacial lake and its ice barrier 
disappeared. 
Where the courses of continuation of marginal moraines 
traverse the area of lake Agassiz, no hills nor even hillocks 
are found, but the surface has unusually plentiful boulders. 
The drift corresponding to the moraines is spread so evenly 
that one scarcely observes any addition above the general 
sheet of till forming adjacent parts of the lake bed; except 
that one of these belts of smoothly leveled morainic till, a few 
miles wide, stretches continuously across the Red river valley, 
past Ada, Minn., and Caledonia, N. Dak., rising very slightly 
above the central broad alluvial tract which otherwise is un¬ 
interrupted along a distance of 250 miles. If the morainic 
drift was supplied from the surface of the melting frontal 
slope of the ice-sheet, it would be washed away and leveled 
in the lake by the great waves of storms; but if it had been 
