298 



METEOROLOGY AND ALLIED SUBJECTS. 



winds. [This influence seems to relate to matters of minor importance as 

 compared with those to which Professor Ferrel has confined his atten- 

 tion.] {Z. 0. G. M., XVI, 1881, p. 532.) 



Dr. A. Sprung gives an elucidation of the theoretical considerations 

 explanatory of his conclusion that the daily period in wind force is a 

 necessary consequence of a daily period in wind direction and velocity. 

 He finds for a period of cloudless weather in Magdeburg the following 

 mean velocities recdrded by the meteorograph of Dr. Assmann. 



These show a wind force increasing as the wind veers toward the 

 east in the morning, and diminishing in the afternoon as the wind backs 

 to NE. A general summary, based on records from 18 stations in Europe 

 and Asia, shows that the number of plus or minus revolutions of the 

 wind-vane is as follows : 



Morning, -\- 4185 - 2617 

 Afternoon, + 2885 - 3267 



whence the Dove law of winds is not confirmed for the afternoon inter- 

 val 1 p. m. to 9 p. m., but is perfectly so inthemorning hours. The " Espy- 

 Koppen" theory of the diurnal variation of the strength of the wind re- 

 quires that no such period should exist at considerable altitudes above 

 the earth, and this is confirmed by the observations taken on Schaffberg 

 and Pic-du-Midi. {Z. 0. G. M., XVI, 1881, p. 424.) 



Sprung has continued his theoretical investigations on the wind by 

 adding a few empirical results as to the relation between the force of 

 the wind, the gradient, and their diurnal periodicity. Expressing the 

 wind force (S) on the Beaufort (0 to 12) scale, and the gradient in milli- 

 meters of the barometer for 111 kilometers (or millimeters for degiee 

 of latitude), he finds in general : 



Gradient = 0.5 + 0.212 8 + 0.019 8\ 



For the same gradient the wind force is greater for north and east 

 winds than for south and west winds, also greater in summer than in 

 winter. The diurnal variation in wind force during clear days is much 



