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Page:Popular Science Monthly Volume 44.djvu/289

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POPULAR MISCELLANY.

England, one from Belfast, Ireland, three from Massachusetts, two from Ohio, two from Illinois, and one each from Iowa and Colorado. Of the twenty-seven papers by professional geologists, twelve were from the United States and three from Canada, the twelve others being as follows: from Brazil, two; Venezuela, one; England, Scotland, and Germany, each two; and Sweden, Norway, and Switzerland, each one. Besides the formal papers, interesting discussions followed, and the programmes for three of the days ended with questions for special discussion, these being. Are there any natural geological divisions of world-wide extent? What are the principles and criteria to be observed in the restoration of ancient geographic outlines? and similarly, What are the principles and criteria to be observed in the correlation of glacial formations in opposite hemispheres? Among the geologists present at this Congress were Prof. Dr. Groth, of Munich; Mr. Hjalmar Lundbohm, of Stockholm; Dr. A. R. C. Selwyn, Director of the Geological Survey of Canada; the venerable Prof. James Hall, whose work in geology began sixty years ago; Profs. Le Conte, Chamberlin, Salisbury, Lindahl, Walcott, H. S. and G. H. Williams, N. H. Winchell, G. F. Wright, and many others from the United States.

 

Subdivisions or Unity of the Glacial Period.—The final day of the World's Congress on Geology was devoted to papers on the Glacial period, of which eight were presented. Brief notes of these papers and of the ensuing discussions will be of popular interest, as they all were specially directed to the recently much debated question whether the ice age comprised two or several glacial epochs, separated by warm intervals, as has been urged by Croll, Geikie, Wahnschaffe, Penck, De Geer, Chamberlin, McGee, and others, or was a single and continuous period of glaciation, as maintained by Dana, Wright, Upham, Lamplugh, Kendall, Falsan, Hoist, Nikitin, and others.

The first paper of this series was by Prof. James Geikie, of Scotland. This distinguished glacialist concludes, from his observations in Great Britain and their correlation with the northern drift-covered portion of continental Europe, that no less than five distinct glacial epochs are recognizable there, separated by long times of interglacial temperate climate. These alternations are held to be in accord with Dr. James Croll's astronomic theory of the causes of the Ice age, affording indeed a demonstration of the truth of that theory.

Mr. Hjalmar Lundbohm, of Sweden, giving the results of his own studies and of the more extended observations of Baron De Geer in that country, thought that good evidence is found for two epochs of ice accumulation and drift deposition. During the first glaciation the Scandinavian ice-sheet flowed outward over the northwestern half of Russia and the northern half of Germany, while southwestward it covered the basin of the North Sea and was confluent with the British ice. The later glaciation, in which a great ice-lobe stretched south and southwest over the basin of the Baltic Sea, formed conspicuous moraines in Finland, northern Germany, and southern Sweden. Since the retreat of this ice-sheet Scandinavia has been differentially uplifted to a maximum amount of about one thousand feet in the center of the peninsula, and the Baltic Sea has been alternately open to the ocean and closed from it, so that for some time it was a fresh-water lake.

Mr. Andrew M. Hansen, of Norway, also declared in favor of two glacial epochs, each of them inclading two or more stages of ice advance and retreat. The glacial drift of Norway, however, was described as affording little testimony of an interglacial epoch, which this author accepts from its stratified deposits underlain and overlain by till in other parts of Europe.

Dr. Albrecht Heim, of Switzerland, from the glacial drift with intercalated beds containing lignite coal and plentiful plant remains in valleys of the Alps, confidently asserted that the glaciers must three times have advanced far beyond their present limits. The second advance was the farthest, and was doubtless contemporaneous with the maximum extension of the ice-sheets of Scandinavia and Great Britain.

Dr. Robert Bell spoke of the glaciation of Canada, which was wholly enveloped by the North American ice-sheet, excepting a tract west of the lower Mackenzie Valley and perhaps a narrow area adjoining the east