Pressure and Direction of the Wind. 435 



The first column of resultant means is obtained by dividing the resultant sums by the whole number of 

 observations of 24 a-day ; the second column is obtained by dividing the resultant sums by the number of ob- 

 servations for which the wind was blowing. 



Annual Variation of the Resultant Pressure of the Wind. — The resultant mean, with reference to the whole 

 number of observations, was greatest in April and least in July, September, and December. It was greatest 

 in the meteorological summer and least in the meteorological winter ; it was greatest in the astronomical spring 

 and least in the astronomical summer and winter. The resultant mean, with reference to the time during which 

 the wind was blowing, was greatest in January and was least in September ; it was greatest in the meteorological 

 summer and least in the auturun ; it was greatest in the astronomical spring and least in the summer. 



The direction of the resultant was between W. and N. in February, March, and July; between S. and W. 

 in January, April, June, August, September, and October; between N. andE. in May; and between S. and E. 

 in November and December. The direction of the resultant for the meteorological quarters is between S. and 

 W. in the quarters, spring, summer, and autumn, and it is nearly W. in winter ; it is between S. and W. in all 

 the astronomical quarters. 



The direction of the resultant pressure of wind for 1844, =W. 21° S. 



1843, (Table XXXII., p. 299, 1843) =W. 21° S. 



Diurnal Variation of the number of Times which the Wind blew O'l lb., or upwards, in 1844. From 

 Table XXXV. the numbers for each hour are as follow : — 



12 h l h A.M. 2 h 3 h 4 h 5 h 6'- 7 h 8 h 9 h 10 h ll h h Hi P.M. 2 h 3 h 4 h 5 h 6 1 ' 7 h 8 h 9 b 10 h 11'' 

 122 132 12G 137 125 133 143 167 195 204 218 225 236 237 237 232 217 216 197 174 149 139 139 148 



The wind blew oftenest about l h 20 m p.m., nearly the time of maximum temperature and seldomest about 

 2 h a.m., the number being twice as great for the maximum as for the minimum. 



Diurnal Variation of the number of Points of the Compass from which the Wind blew. — The numbers of 

 points in which the wind blew (04 lb., or upwards) oftener than once, twice, or thrice, are as follow: — 



Oftener than 12 h l h A.M. 2 h 3 1 ' 4 h 5 b 6 h 7 h 8 h 9 h 10 h ll h h 1^ p.m. 2 b 3>> i h 5 h 6 h 7 h 8 h 9 h 10 1 ' 1V> 



times, 27 29 29 25 27 25 28 28 30 30 30 31 30 32 32 30 30 31 32 28 28 29 30 30 



1 22 23 20 22 24 22 21 26 25 26 28 29 30 30 28 30 28 28 28 25 24 22 23 22 



2 18 16 16 18 17 17 17 18 22 22 27 24 27 28 25 27 27 26 23 21 18 16 19 1*9 



3 13 11 12 13 13 12 15 16 18 20 23 21 20 24 23 21 21 23 18 17 15 14 14 15 



The wind blows from the greatest number of points about the time of maximum temperature, and from the 

 least number about the time of minimum temperature. If we divide the number of points for each hour by the 

 number of times which the wind blew from them, the quotient will represent the variability of direction. These 

 quotients are as follow : — 



12 h l h A.M. 2 1 ' 3>> 4h 5>» 6h 7 h 8 h 9 1 ' 10'' ll h h l h P.M. 2 h 3 h ■ 4 h 5 h 6 h 7 h 8 h 9 h 10 1 ' XI 1 ' 

 0-22 0-22 0-23 0-18 0-22 0.19 0-20 0"17 0'15 0-15 0-14 0-14 0-13 0-14 0'14 0-13 0'14 0-14 0-17 0-16 0-19 0-21 0-22 0-20 



If the points of the compass be rejected for which the wind blew only once, the variability at the several 

 hours will be represented by the following quantities : — 



0-19 0-18 0-17 0-17 0-20 0-17 0-15 0"16 0-13 0-13 0-13 0-13 0'13 0-13 0-12 0-13 0-13 0'13 0-15 0-15 0-17 0-17 0-17 016 



From both series the variability of direction of the wind is least about the time of maximum temperature 

 and greatest about midnight. The variability, however, has nearly a constant value from 8 h a.m. till 5 h p.m. 



Diurnal Variation of the Mean Pressure of Wind while blowing. — If we divide the sums of pressures for 

 each hour (obtained from Table XXXV.) by the number of times which the wind was observed blowing, we 

 obtain the following mean pressures : — 



12M h A.M. 2>> 3 h 4 h 5 h 6 h 7'' 81' 9h 10*1 ll'i h l h P.M. 2'' 3 h 4'' 5 1 ' 6 h 7 h 8 1 ' 9'' 10 1 ' ll h 

 0'60 -55 -61 -58 '60 -56 -56 -57 "61 -72 -71 '74 -79 -84 -84 -73 -69 -66 -59 -57 -60 -60 "60 -60 



The average pressure of the wind while blowing was greatest at l h 40 m p.m., and it was least about 

 6 h a.m. ; it had nearly the same value about 7 h p.m. as at 6 h a.m., the pressure from 8 h p.m. till 4 h a.m. beintr 

 slightly greater than at either of these hours. 



