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Page:Popular Science Monthly Volume 54.djvu/278

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THE POPULAR SCIENCE MONTHLY.

illustrations in Pennsylvania, Nova Scotia, Kansas, Nevada, and Florida.

Professor Hitchcock has studied the Quaternary or glacial deposits with great success. His first publication upon the terraces and allied phenomena of Vermont appeared while the old views of a submergence, with icebergs, prevailed, to account for the phenomena. A study of the glaciers of Switzerland in 1866 satisfied him of the truth of Agassiz's theory; and whenever the opportunity came for re-examination of the surface geology of northern New England, the facts were found to require a different theoretical explanation. He caused a thorough examination to be made of the Connecticut River terranes by Warren Upham in the New Hampshire Survey, and proved that all the high mountains of Vermont, New Hampshire, and Maine had been glaciated by a southeasterly movement. The ice came from the Laurentian highlands, pushed in a southern direction down the Champlain-Hudson Valley, with a southeasterly flow over New England and southwesterly over the Adirondacks; the last two courses having been subordinate to the first. At present the Laurentian hills are lower than the New England and New York mountains overridden by the ice, and probably the same was the case in the Glacial period. The best explanation of these paths is afforded by the suggestion that a gigantic ice cap accumulated north of the St. Lawrence, towering into the clouds so much that its overflow naturally descended over the White and Adirondack Mountains.

That glaciers should accumulate terminal moraines is axiomatic, but no geologist before 1868 had ventured to suggest where moraines might be located in the United States. In that year Professor Hitchcock delivered a lecture before the Lyceum of Natural History in New York and the Long Island Historical Society in Brooklyn, in which he affirmed that the drift deposits from Prospect Park along the backbone of Long Island for its entire length constituted the terminal moraine of the great continental ice sheet. This declaration inaugurated a new era in the study of the age of ice. The geologists in their several States found the terminal moraines, and the various phenomena began to be classified according to new laws. The search for moraines has resulted in a restatement of the incident of the age of ice; more than a dozen successive terminal moraines have been mapped between New York and Montana, which suggest to us the existence of several glacial periods. In compiling a catalogue of observations of the course of glacial striƦ by the United States Geological Survey, it was found that Professor Hitchcock had recorded for New England as many as all other geologists had observed for the whole country.

Eskers are another interesting class of phenomena, and were