272 THE ATMOSPHEEE AND METEOEOLOGY. 



analogous result, because the direction of an atmospheric current often 

 oscillates to the right and left of one point in the horizon, before 

 describing a complete rotation in one direction or the other. Never- 

 theless, in order to guard oneself against all errors, it is import- 

 ant to study assiduously all the oscillations of the weathercock, 

 for if such a coftiplete gyration of the wind is not effected in the 

 space of one month, the other kind can be completed in the space of 

 a day. At Gnadenfeld, in Silesia, Kolbing observed a normal rotation, 

 the duration of which did not exceed 16 hours, which is the length 

 of a winter night.* 



* Dove, Loi dcs Tempetes^ p. 92 ; PoggendorflTs Annalen, Ixii. p. 273. 



