The southern part of the lower peninsula of Michigan is deeply coated with drift. The drift is often very homogeneous and but moderately interspersed with boulders. Toward the shores of lakes Michigan and Erie the drift is covered by fine lake clays, representing the floors of glacial lakes Maumee, Chicago, and their contemporaries. In this drift, the rivers of the region have carved winding valleys between grassy bluffs, and themselves follow courses yet more winding on the flood-plain floor. Rock is rarely encountered, being buried too deeply. The border of the flood-plain under the bounding bluffs is quite irregular in plan when mapped, but is habitually scalloped in curves concave toward the river and of radius of curvature little greater than that of the neighboring meanders. Occasionally such curves adjoin, separated by sharp reentrant cusps. From 5 to 10 per cent of the bluff is bare of grass or . . .