l68 THE WEATHER, AND WEATHER PROPHETS. 



point lias been surmised from very early times ; but 

 until lately, rather as a matter of occasional remark, 

 agreeing on the whole with the general impressions of 

 casual observers, than as a meteorological law of uni- 

 versal applicability. As such, however, it has now taken 

 its place among ascertained facts ; verified by the regis- 

 tered movements of the wind- vane at every station where 

 continuous observation is made ; and connected by the 

 researches of M. Dove with that great fact which under- 

 lies so many other phenomena the rotation of the 

 earth on its axis.* Nothing apparently can be more 

 capricious than the shifting and veering of a weather- 

 cock on a gusty day, and to any one who watches its 

 leaps to and fro for a few hours, it may well be a matter 

 of surprise to be told that with anything like a fair expo- 

 sure, the preponderance of its movement is sure to be in 

 one direction if not in a week or two, at all events on 

 the long average, and in a great majority of cases before 

 the expiration of a month. Thus it appears from the 

 record kept at the Observatory at Greenwich, in which 

 every change of the wind's direction is noted by a piece 

 of mechanism attached to the vane and traced on a 

 table by a pencil that in the thirteen years elapsed 

 from the beginning of 1849 to the end of 1861, the vane 

 made 166 complete revolutions more in the direction. 



* For the reasoning by which this connexion is made, and for 

 the mode in which any casual advance and retreat of a body of air 

 over an extensive but limited tract of country is transformed by 

 this cause into a relative gyration, the reader is referred to the 

 works already cited in a former note. 



