Peessuee and Direction of the Wind. 



Cl 



212. The following numbers are the ratios for each second hour of the hourly mean pressures observed 

 in all directions (obtained from the year-column of Table 92, by the addition of 0-46, the mean pressure for 

 the 4 years), to the resultant mean pressures, No 210. 



1211 



2'' A.M. 



41, 



6^ 



8^ 



lOi 



0^ 



2^ P.M. 



4" 



et 



Sb 



10" 



2-1 



2-1 



2-1 



2-3 



2-3 



2-4 



2-6 



2-8 



2-9 



2-8 



2-4 



2-2 



We may conclude, as in No. 209, that of the total mass of air in motion at each hour, the greatest proportion 

 was from the same quadrant or direction at 2^ a.m., and the greatest proportion was from opposite directions 

 at 4** P.M. 



213. Times which the Wind blew from the 16 Principal Points of the Compass. — The times which the 

 wind was observed blowing fi-om each point of the compass, at the observation hours, are given for each year 

 in the previous and in the present volume; for 1843 and 1846 the sums for 12 two-hourly observations are 

 given, having doubled these to make them comparable with the means from the hourly observations of 1844 

 and 1845, the sums for four years for each point were obtained : the sums for each of the 16 principal points 

 were then formed in this manner ; — the sum of the times in the north was made equal to half the sum of the 

 times in N by W., plus half the sum of the times in N by E., plus the sum of the times observed in N. ; and 

 similarly for each of the other 16 points.* The sums thus obtained from the four years' observations are as 

 follow : — 



N. 



NNE. 



NE. 



ENE. 



E. 



ESE. 



SE. 



SSE. 



S. 



SSW. 



sw. 



WSW. 



w. 



WNW. 



NW. 



NNW 



779 



1318 



1668 



867 



431 



177 



329 



575 



1088 



2672 



4212 



1949 



1198 



726 



932 



866 



The wind blew most frequently with a pressure of 0*1 lb., or upwards, from a few degrees south of SW., the 

 number of times diminishes rapidly to WNW., increases slightly in NW., diminishes from thence to N., it then 

 increases considerably to a few degrees north of NE., where the secondary maximum occurs almost diametri- 

 cally opposite to the principal maximum of frequency ; from NE. the frequency diminishes to a few degrees 

 south of ESE., where it is a principal minimum, a secondary minimum occurring in the opposite point; from 

 ENE. the number increases rapidly to the maximum at SW. See curve h in the figure. 



Radial scales, a, 1 inch = 2000 lbs. h, 1 inch = 2000 times, c, 1 inch =■ 1 lb. 



* The combination into the 16 principal points was rendered necessary by the fact, that in observing the direction of the wind 

 from an oscillating vane-index, there is a tendency in all cases of doubt to prefer the principal to the secondary point, for which 

 reason the numbers of observations for each of the 16 principal points were always greater than for either of the two adjacent points. 



