248 



REPORT 1844. 



By these results it appears that the greatest amount of wind is in the 

 spring and autumn, the least in summer and winter. By the types in Plate 

 XXXIII. the current advances more steadily and rapidly in its course in the 

 spring and autumn than in the summer and winter. It must be remembered, 

 however, that in all these deductions we are speaking of the integral or total 

 effects ; the mean daily velocity of the wind, taken without regard to direc- 

 tion, may be of itself very considerable, and yet by the neutralization of op- 

 posite forces the great mass of the air may have made but comparatively little 

 progress in a given direction. 



By generalizing the mean results in Table IV. we obtain the comparative 

 amount of wind from opposite points of the compass. Thus calling the 

 winds between N.N.E. and N.N.W. exclusive, north winds; those between 

 S.S.E. and S.S.W. exclusive, south winds; and so on, and then taking the 

 mean integral amount, we have for eight opposite points thus reduced the 

 following comparative numbers : — 



North S86 West 295 South-east 150 North-east 417 

 South 1793 East 308 North-west 312 South-west 929, 



by which it appears that the mean amount of north winds including 45 de- 

 grees, is le.ss than that of south winds, in the ratio of 1 : 4 at least. 



The mean amount of west wind is less than that of east, in the ratio of 

 1 : 1-7 nearly. 



The mean amount of south-east is less than that of north-west, in the ratio 

 of 1 : 2 nearly. 



The mean amount of north-east is less than mean amount of south-west 

 also, in the ratio of 1 : 2 nearly. 



It must be borne in mind, that in generalizing the results of this instru- 

 ment we are not considering the prevalence or frequency of any particular 

 wind in a given place, but its particular or integral effect, that is to say, 

 the comparative distance over which a particle of air would pass during the 

 time a certain wind blows ; and this may with a strong east wind of only one 

 day, far exceed in effect the breezes of a gentle west wind of a week. If 

 we take in Table IV. the total mean amount of wind in the north semicircle, 

 and also that in the south semicircle, from east to west exclusive, c&W'mg those 

 on the north side, north winds, and those on the south, south winds, we ob- 

 tain the following results : — 



North 2672, south 5806, being in the ratio of 1 : 2. 



Treating the east and west semicircles in a similar way from north to south 

 exclusive, we have, east 2697, west 4120, being a ratio of 1 : 1-5 nearly. 



Reducing these numbers to two effective forces by subtracting the north 

 from south and east from west, we have for a final result, south 3134, west 

 1423, that is to say, two rectangular forces, whose intensity and directions 

 are given and whose resultant may therefore be easily found. 



The direction of this resultant will be N.N.E., the wind being S.S.W,, as in 



