206 M. Dove oti the Wind. 



which returns to the equator or to its origin, under tlie form 

 of liquid water, so that there is a double cause to which we 

 may ascribe the mean direction of the wind to the south-we.*t, 

 in the northern temperate zone, and to the north-west, in 

 the southern temperate zone. It is evident, that what has 

 been said as to the mean direction of the wind does not apply to 

 its compounds, that is to say, that at a determined period of tlie 

 year, it must necessarily liappen, that the same parallel should 

 be traversed by winds in a contrary direction. It is not less 

 evident, that it must be extixnnely difficult, in consequence of 

 the multiplicity of directions observed, to demonstrate the 

 compensation which must take place in each case. This fact, 

 at the same time, had always been, indirectly, rendered very 

 probable by the climateric circumstances of localities placed 

 at short distances from each other, in the work ^^'hich the au- 

 thor has undertaken on the periodical changes in the distri- 

 bution of the temperature at the surface of the earth, for 

 upwards of a century, principally between the American and 

 European stations ; but it was desii'able to see tliis compen- 

 sation contirmed in a direct manner. 



A great number of monthly directions of winds, calculated 

 by MM. Schlibler,Kaemtz, Wenckeback,Kupfer,Haellstroem, 

 and the autlior, have demonstrated that in Europe, the di- 

 rection of the wind, which in winter is south-v/est, is changed 

 in summer into a north-west direction, again returning to the 

 south in autumn. According to the causes explained above, 

 there cannot be, in all the temperate zone, a north-west direc- 

 tion of the wind simultaneously in all the places of the same 

 parallel, since at all epoch ^ the south winds must predominate 

 over those of the nortli. It is necessan', therefore, in order 

 that compensation take place, that the periodical changes 

 should be opposed to those of Europe. This is precisely the 

 case with regard to North America, where the south-west 

 direction of the wind prevails in summer, and the north-west 

 in winter. It would occupy too much space to give here the 

 tables and formulas which the author has employed to demon- 

 strate the existence of this phenomenon.* 



'•■■ From Ti'Institut, Xo. 71T, p. 1G9. 



