l68 THE WEATHER, AND WEATHER PROPHETS. 



point has 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 tne en( i 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. 



