sion by the approval of his work which was given by the venerable Prof. W. B. Rogers, then at the head of the Massachusetts Institute of Technology, and for so long a time connected with the Geological Survey of Pennsylvania and the adjoining Appalachian region.
"During all his earnest search for the truths of Nature, Lewis was stimulated by the thought that man does not live by bread alone, but that he who ministers to the mental wants of the race by discovering truth and bringing it within reach of the general apprehension is as truly a philanthropist as he who ministers to their bodily comfort. In all these aims it is gratifying to know that his wife most heartily coincided. A great truth of Nature, like the wonderful history of the Glacial period, when it finds its way into the school-books of the children and into works of general literature, is of incalculable utility in the intellectual development of mankind."
"Prof. Lewis first became specially interested," writes Mr. Upham, "in the glacial drift and its terminal moraine during the latter part of the year 1880, when, in company with Prof. G. F. Wright, he studied the remarkable osars of Andover, Mass., the gravel of Trenton, N. J., containing palæolithic implements, the drift deposits of the vicinity of New Haven, Conn., under the guidance of Prof. Dana, and finally the terminal moraine in eastern Pennsylvania between the Delaware and Lehigh Rivers. The following year Profs. Lewis and Wright traversed together the southern border of the drift through Pennsylvania from Belvidere, on the Delaware, west-northwesterly more than two hundred miles across the ridges of the Alleghanies, to Little Valley, near Salamanca, N. Y., and thence southwesterly one hundred and thirty miles to the line dividing Pennsylvania and Ohio, which it crosses about fifteen miles north of the Ohio River. The report of this survey of the terminal moraine was published in 1884, forming Volume 2 of the reports of progress of the Second Geological Survey of Pennsylvania.
"With the similar exploration of other portions of this great moraine done a few years earlier by Prof. Chamberlin in Wisconsin, Profs. Cook and Smock in New Jersey, and Mr. Warren Upham in Long Island, thence eastward to Nantucket and Cape Cod, and also in Minnesota, it completed the demonstration of the formation of the North American drift by the agency of land-ice.
"The observations of the moraine in Pennsylvania, detailed in this volume, are summarized by Prof. Lewis as follows: 'The line separating the glaciated from the non-glaciated regions is defined by a remarkable accumulation of unstratified drift material and bowlders, which, heaped up into irregular hills and
