RECORD AND DISCUSSION OP FORCE OF WIND. 



79 



Quantity and Relative Frequency of the Winds. The sum of the velocity-numbers, 

 or the number of miles travelled over by the air in any direction for any given 

 period, may be called the quantity (q) of the wind which has been transferred over 

 the place of observation during that time. It will not be necessary to take into 

 account the variations in the density of the air, and the number given below refers, 

 therefore, to an average density. The velocity-numbers for each wind and month 

 have been given in a preceding table; they require, however, a correction, in order 

 to find q, for the occasional omissions in the observations. Thus, in September, 

 1853, no observations were recorded during 109 hours, and we may assume that 

 during this time the several winds (inclusive of calms) occurred, or would have 

 occurred in quantity and with a frequency directly proportional to their numbers 

 found from the 720 109 remaining hours of the month. After adding this pro 

 portional number for each wind and month, and after taking mean values for the 

 same months, the following table of the quantity of w r ind (q) has been made out. 



The following table gives the number of hours during which each wind blew, or 

 the relative frequency of each wind for every month. 



The preceding tabular results have been laid down graphically on the accom 

 panying diagrams. The two rectangular diagrams show the quantity of each wind 

 for each month ; the first for the directions S., S. W., W., and N. W., the second 

 for the directions N., N. E., E., and S. E. The circular diagram exhibits the quan 

 tity of each wind for the whole year, as indicated by a full line according to the 

 scale at the foot of the diagram. It likewise shows, by a dotted line, the relative 

 frequency of each wind during the year (on a ten times larger scale). 



