78 



RECORD AND DISCUSSION OF FORCE OF WIND. 



Mean Velocity of the Winds. The average velocity with which each of the eight 

 winds passes over the place of observation in each month and for the whole year, 

 is found by dividing the sum of their velocity-numbers in the period by their 

 respective number of entries in the table; thus, for the month of September, 1853, 

 we have: 



In the following table of the mean velocity of the winds, the values for Sep 

 tember, October, November, December, and January are mean values. As in the 

 above example, the weighted means are given in the table. 



The winds, therefore, blow with their greatest strength in the months of Sep 

 tember and December, and with their least strength in the months of March and 

 May; in the former the mean velocity is 9.6, and in the latter case 4.2 miles per 

 hour. In the following table is exhibited the mean velocity of each wind 

 separately : 



Magnetic 

 direction. 



S. . 

 S. W. 

 W. . 

 N. W. 



N. . 

 N. E. 

 E. . 

 S. E. 



Mean velocity in 

 miles per hour. 



. T.4 

 . 11.2 



4.1 



. 4.8 

 . 3.5 



6.2 

 . 6.0 



6.3 



IrucMnlJb 



Of all winds, the S. W. (magnetic) 

 blows with the greatest force, and the 

 north wind with the least. The rela 

 tion of the velocity of the wind to its 

 direction is further illustrated by the an 

 nexed diagram. 



o 6 10 mil 



