OF THE DIRECTION AND FORCE OF TITE WIND. 



63 



R 



n 



; this supposes an equal and parallel motion of all particles passing over ; the 



length of the path described by each can be found by the summation of all the vs 

 (for each hour) during the period. 



The great variability in the direction and force of the atmospheric motion ren- 

 ders the taking of resulting values for short intervals unnecessary, and a subdivision 

 of the reduction into monthly periods has been found convenient. 



To include more than eight directions into the discussion would not only render 

 it very tedious, but would give no materially increased accuracy. Observed direc- 

 tions, intermediate of the eight directions, are referred to the nearest principal 

 direction ; and if midway, and occurring more than once, they are referred to the 

 nearest preceding and following direction alternately. 



The winds observed during July and August, 1857, and in September, 1859, 

 cannot well be combined with the body of the observations, and have, therefore, 

 not been reduced. 



To illustrate the process of reduction, the working up of the observations for 

 direction and force of the wind in the month of September, 1857, is here given as 

 an examj^le. 



By preceding formula) we find — 



c = —145 0.7 (c—d) = —190 



rf=+126 o.7(e+rf)=— 13 



c— d = —271 a = +299 



c+d = _ 19 b = + 9G 



equivalent to a resulting direction of the wind S. W. f S. 



J? 3 = +109 

 Rw= + 83 

 R = +137 



<P = 37° 



