86 The American Geologist. February, i904. 
upper portion of the underground quartzyte-ridge, clad and 
flanked, to some extent at least, by later Mesozoic rocks and 
rising more or less abruptly above the Tertiary plains, thus giv- 
ing way to the tendency of the ice-sheet to extend also laterally 
at about the point where we have now the northern limit of 
Lincoln county. 
In the southern part of the region we meet with a similar 
phenomenon. As seen on the map, the "Canton ridge"' sud- 
denly changes its direction at a point cut by the 96° 40' merid- 
ian, and, trending westward for about 7 miles, forms an angle 
of nearly 90°. The circumstance that in about that neighbor- 
hood, as already mentioned, a very firm, "flint like" sandstone 
has been revealed by boring at a depth of about 100 feet, prob- 
ably underlain by the same red Sioux quartzyte as found in the 
north, suggests that also here the quartzyte, flanked or entirely 
covered by hard sandstone, rose probably as an outlier above its 
surroundings. The lateral extension as well as the southward 
movement of the glacier was here arrested, the resistance met 
with giving rise to a stowing of the material to a bight which 
even exceeds that of the northern ridge, while the more western 
portions of the ice-sheet, which were not obstructed by barriers 
of anv kind, proceeded southward, thus continuing the moraine 
over Beresford in an average direction N.-S. beyond the south- 
ern limit of the area. 
Standing on the back of the northern member of the mo- 
raine, about three miles north of Tea, one is struck by the flat- 
ness of the surface that extends, like a narrow swell, about a 
mile in width, at nearly the same level towards the east, until 
it turns northward and assumes towards Sioux Falls a rather 
hillv character. It is discontinued within the limits of the 
region under discussion at several points, where the waters, dis- 
charged from the glacier, had dug outlets into the deposited 
material. These outlets exist in the form of shallow sags with 
more or less even floors east of the Breckenridge Division of 
the Great Northern R. R. and west of the Chicago. Milwaukee 
& St. Paul R. R., and also in the form of a deeper channel, 
which, about a mile in breadth in its upper level, has cut over 
60 feet into the till, thus dividing the northern member of the 
Altamont moraine into two portions, a western and an eastern 
one. This deeper channel as well as the shallower sags drained 
