212 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 under- 

 stood, although Plants and F. von Lepel have succeeded in pro- 

 ducing 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 insuffi- 

 cient, and gives no satisfactory explanation of the various phe- 

 nomena which have been observed. The subject still needs in- 

 vestigation. 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 light- 

 ning should communicate his observations to one of the meteoro- 

 logical journals. Translated for the Popular Science Monthly 

 from Die Gartenlaube, by Laivrence B. Fletcher. 



WORLD'S GEOLOGISTS AT ST. PETERSBURG. 



By WILLI A.M 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 

 Ziirich accepted the invitation. By unanimous vote, A. Karpin- 

 sky. 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, secre- 

 taries. 



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 Constantino- 

 vitch will act as Honorary President. Prof. Karpinsky will 

 doubtless be made President of the congress. Circulars of in- 

 formation 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 con- 

 gresses so far held. The geological map of Europe, which will 

 probably be printed complete in two years, will be exhibited. Seg- 

 ments of this map have already been received by geologists, and 

 will probably have their hearty approval at the congress. The 



