MEMORIAL OF G. F. WRIGHT 17 



age channel that was tributary to the plain from the north. In Andover 

 a very remarkable tract of eskers, collectively known as Indian Iiidge, 

 was found by Wright to be a part of a prolonged series of such ridges 

 which he traced practically 25 miles. From the south edge of New 

 Hampshire it crosses the Merrimac Kiver* at Lawrence and continues 

 southward through Andover, Reading, and Wakefield to Maiden. He 

 also mapped another and nearly parallel esker series, seven to ten miles 

 farther east, crossing the Merrimac near Haverhill. Among the earliest 

 to give the true explanation of the origin of kames and eskers, by deposi- 

 tion in the ice-walled channels of streams flowing from the ice-shei k t 

 when it was being melted away, Wright contributed four papers, pub- 

 lished in 1875 to 1879 by the Essex Institute, the Boston Society of Natu- 

 ral History, and the Geological Survey of New Hampshire. 



In 1881 Professor Wright and Henry Carvill Lewis were appointed 

 by J. P. Lesley, Director of the Second Geological Survey of Pennsyl- 

 vania, to trace the terminal moraine of the continental ice-sheet across 

 that State. The account of this work, prepared by Lewis, forms volume 

 Z in the elaborate series of that survey, being entitled "The Terminal 

 Moraine in Pennsylvania and Western New York/'' 



Through the interest and financial aid of friends in Ohio, Wright ex- 

 tended his exploration of the drift border through that State and Indiana 

 to southern Illinois. In the vicinity of Cincinnati he ascertained that 

 the ice margin covered the valley of the Ohio River along a distance of 

 fully thirty miles, reaching several miles into Kentucky, and there spread- 

 ing its till, with striated boulders, to a thickness of ten or fifteen feet at 

 heights of about 400 to 550 feet above the river, which at Cincinnati is 

 450 feet above the sealevel. His report, "The Glacial Boundary in Ohio, 

 Indiana, and Kentucky," 86 pages, with numerous maps, issued at Cleve- 

 land in 1884, is Tract 60 in the series of publications of the Western 

 Reserve Historical Society. 



An ice-dam of such area and height would hold a large and widely 

 branching lake, having its surface 1,000 feet or more above the sea, 

 along the valleys of the upper Ohio and its tributaries. Evidence for 

 this Lake Ohio, as it was named by Prof. E. W. Claypole in a paper read 

 before the Geological Society of Edinburgh and published in their Trans- 

 actions in 1887, has been supplied by many observations of Wright and 

 others, including most notably Prof. I. C. White, of Morgantown, West 

 Virginia, in the Monongahela Valley. 



This very interesting subject, winch deserves further attention with 

 detailed surveys of the valley terraces, was well reviewed by Wright in 



* This river, and also the county and township named from it. are spelled Merrimack 

 in New Hampshire; hut the river and township in Massachusetts arc Merrimac. — W. 1*. 



II— Bull. Geol. Soc. Am.. Vol. 33, 1921 



