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Some interesting and important ideas about groups and fields

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REVIEWS 203and of the exploRion at Wiener Neustadt in 1912 by Dr. J. N. Dorr. The author is not prepared to decide whether these observations can be taken as supporting the theory of Von dem Borne, that the sound-waves, which reach the area of abnormal audibility, are reflected in the upper regions of the atmosphere at about the jiinction of the nitrogen ntinosphere with the hydrogen atmosphere, or as agreeing rather with that of S. Fujiwharrr, who in the Bulletin of the Central Meteorological Observatory of Japan connects it with the conditions of wind velocity, at first increasing above the earth's surface up to a certain height, and then decreasing. He mentions incidentally that doily ascents of kites and pilot balloons at Hamburg, Lindenburg, and Friedrichshafen are being made to determine the conditions prevailing in the upper air. Dr. J. N. Dorr also contributes a paper on the same eubject in the same number. The desirability of making observations whenever possible on the audibility of such explosions is strongly urged.