Abstract
THE American Naturalist for June contains several excellent articles. The first is by Prof. J. S. Newberry, “On the Surface Geology of the Basin of the great Lakes and the Valley of the Mississippi.” In the northern half of this area down to the parallel of 38° to 40° N. lat., are found, not everywhere, but in most localities where the nature of the underlying rocks is such as to retain inscriptions made upon them, the unmistakeable indications of glacial action. Some of the valleys and channels which bear the marks of glacial action, evidently formed or modified by ice, and dating from the ice period of an earlier epoch, are excavated far below the present lakes and water-courses which occupy them. These valleys form a connected system of drainage at a lower level than the present river system, and lower than could be produced without a continental elevation of several hundred feet. Upon the glacial surface are found a series of unconsolidated materials, generally stratified, called the drift deposits. These consist in the lowest stratum of the Erie clays of Sir William Logan, above which are sands containing beds of gravel; and near the surface elephants' teeth have been found, water-worn and rounded. Upon these stratified clays, sands, and gravel of the drift, are scattered boulders and blocks of all sizes, of granite, greenstone, siliceous and mica slates, and various other metamorphic and eruptive rocks, generally traceable to some locality in the Eozoic area of the lakes. Among these boulders many balls of native copper have been found, which could have come from nowhere else than the copper district of Lake Superior. Above all these drift deposits, and more recent than any of them, are the “lake ridges,” corresponding to our raised sea-beaches, embankments of sand, gravel, sticks, leaves, &c., which run imperfectly parallel with the present outlines of the lake margins, where highlands lie in the rear of such margins. The general conclusions drawn are the existence of a glacial epoch over the northern half of the continent of North America, probably contemporaneous with that of Europe, and with a climate comparable to that of Greenland; that the courses of these ancient glaciers correspond in a general way with the present channels of drainage; and that at this period the continent must have been several hundred feet higher than now.—“A Winter's Day in the Yukon Territory,“ by W. H. Dall, refutes the prevalent idea, perpetuated even by “official” reports, that the island of St. Paul is surrounded in winter by immense masses of ice, on which the polar bears and arctic foxes sail down from the north and engage in pitched battles with the wretched inhabitants. The fact is that there is no solid and very little floating ice near St. Paul in winter; the arctic foxes found there as well as on most of the islands were purposely introduced by the Russians for propagation, a certain number of skins being taken annually; and there is no authentic evidence that the polar bear has ever been found south of Behring's Straits. The country of Alaska comprises two climatic regions, which differ as widely as Labrador and South Carolina in their winter temperature. One contains the mainland north of the peninsula of Alaska and the islands north of the St. Matthew group; the other includes the coast and islands south and east of Kadiak, while the Aleutian Islands, with the group of St. Paul and St. George, are some-what intermediate. A day's excursion during the winter season in the northern and more inhospitable of these two regions yielded a considerable number of interesting animals.—Articles of a popular character are “Our native Trees and Shrubs,”by Rev. J. W. Checkering, Jun.; and “A Few Words about Moths,” by A. S. Packard, Jun. A review of Principal Dawson's article in the Canadian Naturalist on “Modern Ideas of Derivation,”criticises, favourably on the whole, that writer's strictures on the Darwinian theory of Natural Selection.—The Natural History Miscellany contains many interesting notes, either original or culled from English scientific journals.
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Scientific Serials. Nature 2, 177–178 (1870). https://doi.org/10.1038/002177a0
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DOI: https://doi.org/10.1038/002177a0