254 PROGRESS OF METEOROLOGY IN 1889, 



Professors Mohii and Hildebrandssou have published a studj^ of 

 thunder- storms in the Scandinavian peninsula. (Upsala, 1888, 55 pp.) 

 This monograph supplies for the Scandinavian peninsula statistical 

 information about thunder-storms similar to that so richly collected in 

 the states of central Europe. The meteorological conditions favorable 

 to thunder-storms in eastern Xorway are given in detail, and by their 

 aid thunder-storms can be predicted from the morning weather map. 



Dr. E. Wagner has investigated the periodicity of thunder-storms in 

 Bavaria, Wurtemburg, and Baden, and tinds that they have a period 

 of twenty-nine days, containing three maximum points, the chief of 

 these being in the last half quarter, the next at new moon, and the 

 least at full moon. No phj-sical explanation for this is attempted. 

 {Meteor ologische Zeitschrift, 1889, vi, p. 299.) 



Doctor Wagner has tabulated the observations of thunder-storm 

 frequency in Bavaria and Wurtemburg with respect to the phases of 

 the moon, and considers that they each show a well-marked maximum 

 between the last quarter and the fourth octant. {Ibid, p. 300.) 



Dr. Karl Lang has reported to the German Meteorological Society 

 the results of his investigations upon the velocity of propagation of 

 thunder-storms in south Germany. He finds a close connection between 

 the velocity of propagation and the proximity of storm tracks. Thus 

 in the winter months, when van Bebber's cyclone track No. iv has its 

 most southerly position, the velocity of thunder-storms is greatest, and 

 geographically the velocity diminishes from north to south. Thunder- 

 storms coming from the west and west-southwest most frequently arise 

 in the southern border of cyclones and travel the fastest, while those 

 from northwest to northeast travel the slowest. {Ibid, p. 271.) 



Dr. Franz Horn finds from a study of thunder and hail storms in 

 Bavaria during the years 1880 to 1888 tliat no hail has ever been re- 

 ported without a simultaneous observation of electrical discharge. 

 The hours of greatest thunder-storm frequency are in the afternoons; 

 in the winter between 2 p. m. and 3 P. m., and in summer an hour later. 

 {Ibid. p. 272.) 



Tornado charts. — Lieut. J. P. Finley has published in successive 

 issues of the American Meteorological Journal State tornado charts 

 showing paths of tornadoes, each accompanied by a brief table of sta- 

 tistics. These ought to be a concise presentation of valuable informa- 

 tion collected on this subject; but as shown by Professor Hinrichs, 

 they contain rather a large amount of mis-information due to the utter 

 absence of scientific criticism in the compilation of the data. 



Tornadoes and derechos. —lu a paper entitled "Tornadoes and Dere- 

 chos," Professor Hinrichs describes the characters of tornadoes and 

 of the peculiarly destructive squalls of Iowa, which he has named the 

 derecho. 



He defines the derecho as a violently progressing mass of cold air, 



