DIRECTION AND VELOCITY OF THE WIND. 217 



Since writing the above I have been kindly favoured by 

 Mr. Main with a copy of the unpublished results of the 

 Anemograph observations for 1866. These I have com- 

 bined with the results of the previous seven years, and 

 have obtained the following mean bi-horary values of the 

 direction and movement of the wind for the entire period 

 of eight years : — 





Mean 



Mean 





Mean 



Mean 





direction. 



bi-horary 





direction. 



bi-horary 



h. 



1 



velocity. 



h. 



/ 



velocity. 



.. 



.... 224 11 .. 



.... 15-43 



12 .. 



... 216 2 .. 



.... 12-12 



2 .. 



.... 225 19 . 



•••• 1573 



14 .. 



... 216 47 .. 



.... 11-96 



4 •• 



.... 223 10 . 



.... 14-89 



16 .. 



... 216 13 .. 



.... 11-82 



6 .. 



.... 220 20 . 



•••• i3'32 



18 .. 



.... 218 56 .. 



.... 11-87 



8 .. 



.... 216 36 . 



.... I2'4I 



20 .. 



.... 218 53 .. 



.... 12-71 



.. 



.... 214 42 . 



.... 12-24 



22 .. 



.... 222 26 . 



.... 14-25 



The mean direction was S. 40° W., and mean daily 

 movement 159 miles. The direction of the disturbing 

 force was from S. 69° 3' W. ; and it had the effect of giving 

 to the air a mean daily movement in that direction of 

 i6'86 miles. The mean magnetic declination for 1866 

 was 20° 28' W._, and the mean for the eight years 1859-66 

 was 20° 52'-8 W. A line perpendicular to this is S. 69° y''2 

 W. to N. 69° 7' -2 E. Thus the mean direction in which 

 the disturbing force acted during the eight years, differed 

 only 4'* 2 from that of a perpendicular to the magnetic 

 meridian. The observations for 1866, therefore, fully bear 

 out the conclusions to which I had been led by the dis- 

 cussion of those of the preceding seven years. 



It will be evident that a force which moves the atmo- 

 sphere daily through an average distance of 1 6 or 1 7 miles, 

 in a direction differing considerably from the mean direc- 

 tion of the wind, is an important element to be taken into 

 account in framing a scientific system of forecasting the 

 state of the weather. 



