76 



RECORD AND DISCUSSION OF FORCE OF WIND. 



Resulting Monthly Direction of the Wind. — The resulting monthly direction ^ of the 

 wind is obtained by adding up the velocity-numbers for each wind separately, from 

 the hourly observations taken during the month, irrespective of omissions. The 

 numbers thus obtained are then treated in accordance with the preceding formulae. 

 For the month of September, 1853, for instance, we would have — 



To convert the resulting ^ from the magnetic into the true direction, apply the 

 magnetic declination, viz: 108° 12' west.^ 



In like manner, the mean direction of the wind for each month has been made 

 out. The following table exhibits the sum of the velocity-numbers for each wind, 

 as well as the resulting direction of the winds for each month of observation : — 



To obtain the resulting direction of the wind in each month, each season, and for 

 the whole year, we first take the mean of the values li^, and i?„ respectively, for 

 the same months in the different years and find — 



' See my discussion of Dr. Kane's magnetical observations, in Vol. X, of the Smithsonian Contnbu- 

 tions to Knowledge, 1858, p. 25. 



