Beelevation of the St. Lawrence river basin. 3
uplift averages seven inches per mile ; and the eastward ascent is approximately three inches per mile. The latest and lowest of the Western Superior lake beaches observed at Duluth, occupied by the "boulevard" or pleasure driveway, 475 feet above the lake, on the bluffs back of the city, appears to have an ascent of only about 35 feet in the distance to Mt. Jose- phine, showing that the uplift of the land was quite rapidly in progress while the ice-front still maintained the lake at the St. Croix outlet. Not long after the glacial retreat passed east- ward beyond Mt. Josephine and Marquette, this lake was low- ered and merged with Lake Warren across the lowlands of the northern peninsula of Michigan. The vertical interval between the final stage of the Western Superior Lake and the level of Lake Warren shown by its earliest beach at Duluth was about 60 feet. Thenceforward the outlet of Lake Warren past Chi- cago carried away the drainage from the glacial melting and rainfall of the Superior basin.
The Western Erie glacial lake* — Outflowing from the southwestern end of the Lake Erie basin by a large abandoned watercourse, which reaches from Ft. Wayne, Ind., where the St. Joseph's and St. Mary's rivers unite to form the Maumee, across the present watershed to the Wabash river, this glacial lake formed two distinct beaches, named by N. H. Winchell the Yan Wert and Leipsic ridges, separated by a vertical inter- val of 15 to 20 or 25 feet. The upper or Yan Wert beach, with its crest varying in altitude from 200 to 220 feet above Lake Erie (whose mean height is 573 feet above the sea), extends about 75 miles east to Findlay, Ohio, and nearly an equal distance northeast past Bryan, Ohio, to the vicinity of Adrian, Mich., if not farther. At Findlay the lake while forming this beach, as Winchell and Leverett have shown, was bounded on the north by the ice-sheet then forming the Blan- chard moraine. The second or Leipsic beach of the Western Erie Lake, ranging in height from 190 to 210 feet, runs from Ft. Wayne eastward 175 miles to its termination, as described by Leverett, at the line of a later moraine close southwest of
- G. K. Gilbert, this Journal, IIT, vol. i, pp. 339-345, with map, May, 1871;
Geology of Ohio, vol. i. 1873, pp. 540-556, with two maps. N. H. Winchell, Proc. A. A. A. S., vol. xxi, for 1872, pp. 171-179 ; Geology of Ohio, vol. ii, 1874, pp. 56. 431-4H3, etc. J. S. Newberry, Geology of Ohio, vol. ii pp. 46-65, with three maps and numerous sections. E. W. Claypole, "The Lake Age in Ohio," Trans. Geol. Soc. Edinburgh, 1887, p. 42, with four maps. G. F. Wright, The Ice Age in North America, 1889, chapter xv (with reproduction of Prof. Clay- pole"s maps, that of Lake Erie-Ontario being on p. 355). J. W. Spencer, this Journal, III, vol. xli, p. 208, with map, March, 1891; Bulletin, Geol. Soc. Am., vol. ii, 1891, pp. 465-476, with map. Frank Leverett, this Journal, III, vol. xliii, pp. 281-297. with map, April, 1892. Warren Upham. Bulletin, Geol. Soc. Am., vol. ii, p. 259; Minnesota Geol. Survey, Twenty-second Ann. Rep. for 1893, p. 62 (first use of the name Western Erie Glacial Lake).
