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POPULAR SCIENCE MONTHLY.

mass fell to the earth, the wire melted, and the spectators were left in total darkness.

The nature of this peculiar form of lightning is not yet understood, although Planté and F. von Lepel have succeeded in producing in the laboratory, with the aid of powerful electrical machines, small balls of fire which, like those of Nature, moved to and fro for a while and then vanished.

These experiments have suggested the theory that the fireballs consist of heated air and water vapor. But this theory is insufficient, and gives no satisfactory explanation of the various phenomena which have been observed. The subject still needs investigation. It is especially desirable to increase our store of working material—that is, of observations. Whoever, therefore, is fortunate enough to have witnessed a display of globe lightning should communicate his observations to one of the meteorological journals.—Translated for the Popular Science Monthly from Die Gartenlaube, by Lawrence B. Fletcher.

 

WORLD'S GEOLOGISTS AT ST. PETERSBURG.
By WILLIAM H. BALLOU.

THE Fifth International Geological Congress at Washington received an invitation from the Russian government to hold its seventh session in St. Petersburg. The Sixth Congress at Zürich accepted the invitation. By unanimous vote, A. Karpinsky. Director of the Committee of Geologists of Russia, was elected president of the Bureau of Organization; A. Inostranzew, vice-president; Th. Tschernyschew and N. Androussow, secretaries.

His Majesty the Czar will open the Seventh International Congress at St. Petersburg on August 17th, and welcome the visiting delegates to his empire. The Grand Duke Constantinovitch will act as Honorary President. Prof. Karpinsky will doubtless be made President of the congress. Circulars of information in French have been received by geologists, outlining the occupations of the delegates, so far as the Russians can arrange for their pleasure. The sessions will last seven days, preceded and succeeded by intervals of geological and sight-seeing excursions, covering the principal areas of Russia.

In many respects this will be the most important of the congresses so far held. The geological map of Europe, which will probably be printed complete in two years, will be exhibited. Segments of this map have already been received by geologists, and will probably have their hearty approval at the congress. The