Page:Popular Science Monthly Volume 46.djvu/145

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ing the Glacial and Recent periods, is marked by the number of papers—eight before the Geological Society, and an equal number before the association, which pertained to this latest geologic era. Among these, perhaps the most notable was by Arthur Hollick, on the disturbance of the Cretaceous and Tertiary clay and sand strata next beneath the glacial drift along the course of the terminal moraine in northern New Jersey, on Staten and Long Islands, Martha's Vineyard, and Nantucket. The crumpled and distorted condition of these beds he ascribed to the crushing force of the ice advance. The dislocations and tilting are of similar character with the disturbances which have been shown to have resulted from the thrust of the Scandinavian ice sheet on the islands of Möen and Rügen in the Baltic Sea.

The recession of the ice sheet from the region of the Great Lakes tributary to the St. Lawrence was discussed in a paper by Warren Upham, tracing the successive stages of the ice-dammed lakes of that region, as known by their beaches, far above the present lake shores. From the relationship of those glacial lakes, held by the barrier of the waning ice sheet on their north and northeast sides, it was shown that the ice sheet in its retreat was melted away from the northern borders of the United States west of Lake Ontario somewhat earlier than from New York and New England. The measure of the Postglacial or Recent period, from the end of the Ice age until now, was thought from the rate of erosion of the gorge below Niagara Falls to have been about seven thousand years. Prof. J. W. Spencer, however, in another paper argued that the duration of this period has been some thirty thousand years.

Prof. Spencer also read a paper on the late Tertiary and Quaternary changes of level of the West Indies, in which great movements of uplift and depression of Cuba and the adjacent Antilles were held to have united these islands repeatedly to the North and South American continents, while the Gulf of Mexico and the Caribbean Sea were connected with the Pacific Ocean.

The Quaternary history of the Mississippi Valley was considered by Oscar H. Hershey, who regarded the loess of Illinois, Iowa, and the States farther south as the deposit of a somewhat late stage of the Glacial period.

Prof. Calvin's address is published in full in the American Geologist for September; most of the Geological Society's papers will soon be issued in its Bulletin, and abstracts of the association papers will appear, probably about a year hence, in the Proceedings of this meeting.

Officers of the American Association. The following officers of the American Association have been elected for next year: President, E. W. Morley, Cleveland, Ohio. Vice Presidents: A, Mathematics and Astronomy, E. S. Holden, Lick Observatory, Cal.; B, Physics, W. Leconte Stevens, Troy, N. Y.; C, Chemistry, William McMurtrie, Troy, N. Y.; D, Mechanical Science and Engineering, William Kent, Passaic, N. .J.; E, Geology and Geography, Jed. Hotchkiss, Staunton, Va.; F, Zoölogy, D, S. Jordan, Palo Alto, Cal.; G, Botany, J. C. Arthur, Lafayette, Ind.; H, Anthropology, F. H. Gushing, Washington, D. C.; I, Economic Science and Statistics, B. E. Fernow, Washington, D. C. Permanent Secretary, F. W. Putnam, Cambridge, Mass. General Secretary, James Lewis Howe, Louisville, Ky. Secretary of Council, Charles R. Barnes, Madison, Wis. Treasurer, R. S. Woodward, New York. Secretaries of Sections: A, E. H. Moore, Chicago, 111.; B, E. Merritt, Ithaca, N. Y.; C, William P. Mason, Troy, N. Y.; D, H. S. Jacoby, Ithaca, N. Y.; E, J. Perrin Smith, Palo Alto, Cal.; F, S. A, Forbes, Champaign, Ill.; G, B. T. Galloway, Washington, D. C.; H, Mrs. Anita Newcombe McGee, Washington, D. C.; I, E. A. Ross, Palo Alto, Cal. The association decided to meet next year in San Francisco, Cal., provided acceptable terms were secured from the railroads.

The Falling of the Leaves. According to a paper by Prof. Trelease, quoted in Garden and Forest, three more or less distinct periods are observable in the falling of the leaves. The first, occurring on an average a week earlier than the main fall, is marked by the loss of the leaves of weakly twigs; the second comprises the main defoliation; the third embraces the period during which straggling leaves, mostly on branches that have been shaded during the growing season,