Page:The American journal of science, series 3, volume 49.djvu/28

10 10 W. UpKam — Chamjplain Subsidence and

about 135 miles north to Lake Nipissing it descends at an average rate of about eight inches per mile.

While the eastern part of the Lake Algonquin area was being much uplifted, with the formation of other beaches be- low the first, probably the southern part of the Lake Michigan basin remained with a very slight change of attitude or none, having previously risen to approximately its present height, which it has since held with little or no change. But the northeastward elevation raising the country where Lake Al- gonquin and now Lake Huron have outflowed, gradually caused the water level at Chicago to rise some 40 feet above its old Algonquin level, which is shown by a sublacustrine terrace formed by the Algonquin wave erosion and beach accumulation.

On the Saugeen river, Ontario, and near the south end of Georgian bay, fresh-water shells are found in beds belonging to stages of Lake Algonquin respectively about 40 and 100 feet below the main and earliest Algonquin beach, or 90 and 78 feet above the present lake and bay.

Lake Lundy* — From the Forest beach at Crittenden, Erie county, N. Y., marking the latest level of Lake Warren, there is a descent of 125 feet between 860 and 735 feet above the sea to the earliest strand of the glacial Lake Lundy, which for a time occupied the northeastern three-fourths of the Lake Erie basin. A more conspicuous principal Lundy beach, 30 feet lower, on which is the "ridge road" named Lundy lane, near Niagara Falls, has an eastward ascent of 30 feet in about 40 miles from Font-hill, Ont., to Akron, N. Y., live miles north of Crittenden. Lake Lundy opened through a strait about 30 miles wide into the Lake Ontario basin. Its outflow passed eastward, across the country close north of the Finger lakes, to the Mohawk and Hudson valleys, still partly tilled by the receding ice-sheet and permitting a series of mouths of Lake Lundy to be found at successively lower levels, until as the ice-border withdrew the water soon sank to the lowest point of the Ontario-Mohawk watershed at Rome, ~N. Y., where its level long remained, forming the Iroquois beach. One of the stages of the sinking Lake Lundy or incipient Lake Iro- quois, probably nearly midway in altitude between the Lundy and Iroquois beaches, I find to be indicated by my studies of eskers in Rochester and Pittsford, N. Y.f

this Journal, III, vol. xlvii, pp. 207-211, with map, March, 1894.
 * J. W. Spencer, " Deformation of the Lundy Beach and Birth of Lake Erie,"

f Proceedings of the Rochester Academy of Science, vol. ii, pp. 196-198, Jan., 1893.