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Wilkes, Gilbert. Some Practical Hints in Dynamo Design. University of Wisconsin. Pp. 14.

Winchell. Geological and Natural History Survey of Minnesota for 1893. Minneapolis. Pp. 210.

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Meeting of the Geological Society in Baltimore.—The seventh annual meeting of the Geological Society of America was held a; the Johns Hopkins University, Baltimore, Md., December 27th to the 29th. About sixty fellows of the society were present, and fifty papers were read. Prof. T. C. Chamberlin, in his address as the retiring president, spoke of his observations during the past summer on the glaciers and ice sheet of Greenland, especially of Inglefield Gulf and of Bowdoin Bay, a fiord extending from that gulf northward to Lieutenant Peary's winter station. A series of very instructive lantern views of these glaciers was exhibited after this address. The surface of Inglefield Gulf, at its far northern latitude of 78°, lying twelve hundred and fifty miles north of the southern end of Greenland and only about eight hundred and fifty miles from the pole, was mostly frozen during all last summer; and it was with much difficulty that the stanch steamer Falcon, bearing this Peary Relief Expedition, cut its way through the ice pack in August to reach Bowdoin Bay. Because the sun's rays there fall so slantingly, their effect to promote the flow of the glaciers is very slight, the maximum rate of the glacial currents being found to be only two and a half feet a day in midsummer; but the reflection of the solar heat from the ground at the ice margin causes the ends of the valley glaciers and the border of the great inland ice sheet to have a very steep slope, or even in many places a precipitous and sometimes overhanging front. In these ice cliffs, rising abruptly one hundred to two hundred feet or more, the lower half of the ice incloses ranch englacial drift and is very distinctly laminated, having obtained a nearly horizontal or often steeply inclined stratification through the shearing effect of its motion in the upper and central parts being faster than below. As the bowlders and smaller rock fragments are carried onward in the ice, they are thus subjected to much wearing upon each other. At some localities this englacial drift is being amassed beneath the ice border in low, rounded hillocks, nearly like the drumlins or oval hills of till so well developed about Boston, in central New York, and in some other districts of the northern United States and Canada, which have long puzzled glacialists to explain how they could be formed. Other glacial papers were presented at this meeting by Prof. G. Frederick Wright, on his observations last summer in a second expedition to Newfoundland, Labrador, and Greenland; by Prof. C. H. Hitchcock, on deposits regarded as deltas of a glacial or ice-dammed lake in the basin of Lake Memphremagog, the old water level having been about four hundred feet above that of to-day; by H. F. Reid, on the secular recessions and readvances of the present glaciers of the Alps and other regions; by Warren Upham, on the question whether the ice sheets of the Glacial period were formed chiefly by snowfall upon all their area or advanced far beyond their zone of predominant snow accumulation, and a second paper on the climatic conditions shown by North American interglacial deposits; and two papers by Prof. H. L. Fairchild, on the lakes held by the barrier of the waning ice sheet in the valleys of the Finger Lakes, the Genesee River, and other streams in central New York. Prof. Fairchild, from observations made principally during the past year, maps and names fifteen or more of these lakes. They range from ten to thirty miles in length and from two to five miles in width, with outlets across the southern watershed to the head-streams of the Susquehanna. In the long and deep valleys now occupied by Canandaigua, Keuka, Seneca, and Cayuga Lakes, the former glacial lakes stood four hundred to seven hundred feet above the present lake levels, as shown by the old deltas and shore lines. Papers on the crystalline rocks of Archæan or pre-Cambrian age were presented by C. W. Hall, F. . Adams, J. F. Kemp, C. H. Smyth, Jr., W. S. Bayley, and others. The folded structure of the Appalachian mountain belt was 