Page:Popular Science Monthly Volume 52.djvu/153

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141
FRAGMENTS OF SCIENCE.

eral, the nature and office of the secretions, the nervous system, and the workings of the brain—concerning which, "if increasing knowledge gives us increasing power so to mold a muscular fiber that it shall play to the best the part which it has to ply in life, the little knowledge we at present possess gives us at least as much confidence in a coming far greater power over the nerve cell."

 

The Tilting of the Lake Region.—The discussion of the geological history and future of the region of the Great Lakes was again brought up in the American Association by Dr. W. J. Spencer, who, after reviewing his investigations in former years of the ancient outlets of Lake Erie, spoke of the lake region as having been covered subsequently to the Glacial period by great bodies of water all at one level. One of these, Warren Gulf, which covered the lake basins, was broken up by the rise of the land, and Lakes Superior, Huron, and Michigan were formed, their water emptying to the northeastward and not into the Erie basin. Afterward the land rose higher to the northeastward, filled the rivers of the basins upward, and turned the upper lakes into Lake Erie. At the same time the rocky barriers caused Lake Erie to drown the western hundred miles of its basin, and the waters are now rising and will in a few centuries cover Toledo and Detroit. The evidence is recorded in the shore lines, which have been surveyed by Professor Gilbert, the author, and others. They have risen in some cases from four to seven feet per mile going northeastward in a period of about fifty years. Prof. G. K. Gilbert in another paper presented a comparison of surveys made on the lake shores twenty or more years ago and within the past year. It is found that changes have taken place, all of which show a rising of the land at the north or northeast as compared with the land at the south or southwest. The whole lake region appears to be undergoing a tilting toward the south southwest at such a rate that of two points a hundred miles apart, the northern rises five inches in a century as compared with the southern. The mean level of the lake rises at Chicago about an inch in ten years, or ten inches in a century. It is estimated that in about three thousand years all the overflow from the upper lakes will go to the Illinois. The Detroit and St. Clair Rivers will carry water from Lake Erie to Lake Huron instead of from Huron to Erie, and the Niagara River will run dry.

 

Canada's Oldest Geology.—The presidential address of Dr. D. M. Dawson before the Geological Section of the British Association comprised a comprehensive but highly technical account of the Pre Cambrian Rocks of Canada. At the close of his review the author said that the general tendency of our advance in knowledge appears to be in the direction of extending the range of the Palæozoic downward, whether under the old name Cambrian or under some other name applied to a new system defined, or likely to be defined, by a characteristic fauna. The somewhat arbitrary and artificial definition of the Olenellus zone as the base of the Cambrian seems to be not of world-wide application, and not even generally appropriate to North America; while as a base for the Palæozoic eon it is of still more doubtful value. In the Cambrian period as well as in much later geological times the American continent does not admit of treatment as a single province, but is to be regarded rather as a continental barrier between two great oceanic depressions, each more or less completely different and self-contained in conditions and history—that of the Atlantic and that of the Pacific. On the Atlantic side the Olenellus zone is a fairly well-marked base for the Cambrian; on that of the Pacific it is found naturally to succeed a great consecutive and conformable series of sediments, of which the more ancient fauna is now only beginning to be known.

 

The Thumb and Toes in Men and Apes.—The presidential address of Sir William Turner before the Anthropological Section of the British Association was devoted to some of the characteristics of human structure distinguishing it from that of the apes. Its language is largely technical. The description of the differences in the disposition of the thumb and of the toes presents many points of interest. Both in man and the ape the thumb is not tied to the index digit by an intermediate ligament, which, under the