EEaULAE GYEATION OF THE WIND. ]r 271 



takes place according to the path, of the sun." Since the time of 

 the great Greek naturalist many authors, whom Dove has taken the 

 trouble to enumerate, have re-affirmed this fact of the regular rotation 

 of the winds, which was besides known to sailors from time imme- 

 morial. 



" When the wind veers against the sun, 

 =: Trust it not, for back it will run," 



is a seaman's adage. Nevertheless it is only in the nineteenth century 

 that this meteorological phenomenon has been put beyond all doubt. 

 Dove was the first to combine the scattered testimonies which confirm 

 the popular idea, and transform the ancient hypothesis into a scientific 

 certainty. For the future, it has become an incontestable fact, thanks 

 to the savant of Berlin, that in the northern hemisphere the winds 

 succeed each other most frequently in a regular order, which is indi- 

 cated by the following formula : 



S.W., W., N.W., N., N.E.,E., S.E., S., S.W. 

 In the southern hemisphere the normal rotation of the aerial cur- 

 rents is accomplished in the opposite direction, that is to say, from 

 north-west to south-east by the west and south, and from the south- 

 east to north-west by the east and north : 



N.W., W„ S.W., S., S.E., E., N.E., N., KAY. 

 Thus in each of the opposite hemispheres the procession of the 

 winds coincides with the apparent path of the sun, which for Euro- 

 peans describes its daily course to the south of the zenith, and for the 

 Australians passes to the north of this same point. Such is the 

 regular order to which the discoverer has given the name of " law of 

 gyration," and which is often and very justly designated by the name 

 of "Dove's law." Thus the general winds themselves follow, in 

 their succession, the same order as the little diurnal breeze caused by 

 the relative position of the earth and the sun ; * and it is perhaps 

 owing to the support of these light breezes that the normal condition of 

 the rotation of the aerial currents is established in space. 



It is shown, by a great number of observations made in different 

 parts of Europe, that the complete revolutions of the winds in the 

 normal direction are much more numerous than those that occur in a 

 retrograde direction. At Liverpool, London, Brussels, and Kharkov, 

 the direct revolutions constitute, on an average, two-thirds of the total 

 revolutions ; in this respect, there is an almost perfect agreement be- 

 tween the atmospheric system of western and that of eastern Europe. 

 In studying the partial revolutions, one does not always arrive at an 



* See above, p. 261. 



