by a readvance of the ice, which raised the water about 20 feet to an outlet leading past Imlay, Mich. Then was formed the highest beach in the Cleveland area, the Butternut Ridge of the Berea quadrangle and the Leipsic or Middle Maumee beach of the Maumee Basin. The level of this shore line in the Cleveland district is 770 to 780 feet above the sea. At this stage the lake extended eastward to the ice border in the vicinity of Girard, Pa. Glacial Lake Arkona.-The next well-marked step of the ice retreat caused a still greater lowering of the glacial lake waters. The ice withdrew entirely from the Thumb of Michigan, so that the lake east of it fell to the level of a small lake in the Saginaw Basin (Lake Saginaw) and merged with that lake. The resulting lake, called FIGURE 9.-Falling and rising stages of lake waters in the Erie Basin. Oldest at left. Beaches submerged by later expansion of the ponded waters indicated by dotted pattern Lake Arkona, extended from the vicinity of Gladwin, Mich., to a point at least 40 miles east of Buffalo, N. Y., and covered a considerable part of southern Ontario as well as the entire Erie Basin. It found an outlet westward through the Grand River Channel into the Lake Michigan Basin and thence by the Chicago outlet into the Illinois and the Mississippi. Its altitude above sea level was at first 710 feet, but by deepening of the outlet it was lowered to about 695 feet. To this lake is referred the cutting of the lake cliff in the Cleveland district at the base of the Whittlesey beach. Glacial Lake Whittlesey.-This low-water stage was followed by a notable advance of the ice front; connections with glacial Lake Saginaw were severed by the ice crowding upon the Thumb of Michigan, and the waters of the Erie Basin were raised to the level of an outlet |