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THE POPULAR SCIENCE MONTHLY.

since been found at three of the places which he specifically pointed out.

During the summers of 1884 and 1885 he was employed with the United States Geological Survey in tracing the glacial boundary across Illinois, and in reviewing the field in Ohio and western Pennsylvania. His report of this work appeared in 1890, as Bulletin 58 of the United States Geological Survey, on The Glacial Boundary in Western Pennsylvania, Ohio, Kentucky, Indiana, and Illinois. In the summer of 1886 he visited Washington Territory and examined the Muir Glacier in Alaska, where he spent the month of August in company with the Rev. J. L. Patton and Mr. Prentiss Baldwin, collecting facts concerning the motion, size, present general condition, and probable past history and future career of the glacier. He devoted the two following seasons to the further exploration of Ohio and of Dakota, and other parts of the Northwest. "Thus," he says, "I have personally been over a large part of the field containing the wonderful array of facts" which he presents in his Ice Age in North America.

Since making these systematic explorations, while he has continued his outdoor work in various fields, Prof. Wright has devoted much attention to presenting the results of his researches to the public. He delivered courses of lectures on the subject before the Lowell Institute in Boston in the fall of 1887, before the Peabody Institute in Baltimore in 1888, and in Brooklyn, N. Y. The substance of these lectures, rewritten and much added to, was published in 1889 in his noble book, the Ice Age in North America and its Bearings on the Antiquity of Man, a large illustrated volume of 648 pages, which may be fitly described as one of the most valuable of recent contributions to the literature of geology, and as marking an important step in the advance of the science. The volume also contains an exhaustive discussion of the evidences concerning the early presence of man on the American continent, and particularly his existence during the ice age. Besides incorporating in this discussion the fruits of the discoveries of Dr. Metz in Ohio, of Cresson at Medora, Ind., and Claymont, Del., of Winchell and Miss Babbitt in Minnesota, of Dr. Abbott in the Delaware Valley, of Whitney in California, etc., he has introduced discoveries in regard to which he has himself made careful investigations; of the pal├Žolithic implements found at Newcomerstown, Ohio, of the image found at Nampa, Idaho, under the basalt, and of a stone mortar found under Table Mountain in California. As a professor habituated to theological studies, the question of man's antiquity naturally followed him in these investigations, with the inevitable conclusion that the human period must be allowed an extension far beyond previous ideas of the subject, as well as the question of the method of reconciling the fact with