304 METEOROLOGY AND ALLIED SUBJECTS. 



The diurnal periodicity is as follows : 



Interval. No. of Btorms. 



Midnight to 2 a. m 27 



2 a. m. to 4 a. m 26 



4 a. m. to 6 a. m 15 



6 a. m. to 8 a. m , IG 



8 a. m. to 10 a. m 18 



10 a. m. to noon 57 



Noon to 2 p. m 115 



2 p. m. to 4 p. m 143 



4 p. m. to 6 p. m 173 



6 p. m. to 8 p. m 141 



8 p. m. to 10 X). m 75 



10 p. m. to midnight 37 



{Z. 0. G. M., Vol. XVI, pp. 369-372.) 



Schiaparelli and Frisian! have prepared a study of the observations 

 of thunder storms made in Upper Italy during 1877. The latter liuds 

 that the greater part of the storms occur when a barometric maximum 

 is present on the Atlantic coasts of France and England, and pressure 

 is high on the north side of the Alps; a smaller proportion of the storms 

 occur when the maximum barometer is over Northern Africa; very few 

 occur when the maximum is over Upper Italy, and only when clear 

 warm days prevail. None occur when the weather is perfectly clear, 

 Avith uniform high pressure, or when the minimum pressure is due west 

 or the temperature too low. No encouragement is found as to the proba- 

 bility of our being able to predict local thunder storms. {Z. 0. G. ilf., 

 XVI, 1881, p. 300.) 



The distribution of thunder storms in Ziirich during the past ninety 

 years has been studied by the scientific society in that city, the summary 

 of which is given by Hann. The daily records for this period sbow 1,734 

 thunder storms with thunder and lightning, 217 lightning without 

 thunder, and 368 hail storms, of which 116 are included in the above 

 1,734. The annual distribution of these storms by ten-day periods show 

 two maxima of 155 each, viz, the 11th to 20th of June, and 10th to 19th 

 of August. {Z. 0. G. .¥., Vol. XVI, p. 349.) 



X. — ELECTRICITY, MAGNETISM, AURORAS, ETC. 



H. Fritz has published a very complete summary of the present state 

 of our knowledge of the aurora {Bas PolarlicJit, Leipzig, 1881). We 

 quote the following: 



(1) The region of greatest frequency is in the neighborhood of the 

 Arctic Circles, touching North Cape and Point Barrow, and at its 

 southernmost passing through Northern Labrador. This generalization 

 was first published by him in 1867, but in the present work is revised 

 by the help of his great catalogue of auroras, published in 1873. 



The relative frequency of auroras for stations nearest the zone of 



