438 Results op Makeestoun Observations, 1844. 



Times which the Wind blew from the different Points of the Compass. — It will be observed from the sums 

 of times, Table XXXV., that the sums are greater for each of the 16 principal points than for the points imme- 

 diately preceding and succeeding ; tliis is due to the preference given by tlie observer in all doubtful cases to the 

 principal points. The wind blew oftenest in 184-t (as in 1843) from the SW. and scldomest from the SE. by E. 

 If we take the sums of the times for the 5 points SSW. to WSW. corresponding to SW., from WSW. to WNW. 

 corresponding to W., and so for the others of the 8 principal points, we obtain the following numbers : — 



These sums give the same result as the more limited series for 1843. The wind blew oftenest from SW. : 

 tlie number of times diminishes to NNW., where it is a secondary minimum ; it increases to NE., where it is 

 a secondary maximum, and diminishes again to about SE. by E., from which the wind blew seldomest. The 

 wind blew twice as often fi'om SW. as from NE., and twice as often from NW. as from SE. The numbers for 

 the points SE., NW., NE., and SW., arc approximately in the ratio of 1 , 2, 4, and 8. The ratio of the numbers 

 for the same points in 1843 was as 1, 4, 8, and 16. The wind blew twice as often from the points included between 

 N., W., and S., as fi-om the points in the opposite semicircle ; the number fi-om the hourly observations being 

 for the former 2823, and for the latter 1422 : the same result was obtained from the obsei-vations for 1843. 



Sums of Pressures with which the Wind blew from the different Points of the Compass. — The greatest sum 

 of pressures is that for SW., and the least is that for SE. by E. The sums of pressures for each of the 5 points, 

 including the 8 principal points as above, are as follow : — 



The sums of pressures ai-e a maximum about SW. ; they diminish from thence to W., NW., and N., a 

 secondary minimum occurring about that point ; the sums increase thence to NE., where they are a secondai-j' 

 maximum, and diminish from NE. to SE., whei-e the sums of pressures are least ; they increase from the mini- 

 mum at SE. to the maximum at SW. 



Mean Pressure of the Wind, while bloiviny, for different Points of the Compass. — Dividing the sums of 

 pressures, given by the above, for the 8 principal points by the number of times wliich tlie wind blow, we obtain 

 the following as the mean pressures with which the wind blew from the different points : — 



NE. 



lb. 



0-52 



The wind, therefore, on the average, blew with the greatest force from about W. by N., and with the least 

 force from about NE. This result is not nearly so distinct and regular as that for 1843, in which year the 

 wind blew with the gi-eatest force from NW., and with the least from NE. 



Diurnal Variation of the Residtant Pressures of the Wind. — The resultant mean for the time during which 

 the wind blew is a secondary minimum about 5'' 40"" a.m., a principal maximum about l^" p.m., a pi-inci])al mini- 

 mum about 6'' 40™ p.m., and a secondary maximum about midnight. (See Table XXXVI.) The resultant 

 means for the whole number of observations indicate generally the same law. 



Diurnal Variation of the Direction of the Resultant Wind. — The result exhibited in tlie last column of 

 Table XXXVI. was obtained from the observations for 1843, though not so distinctly. The direction of the 

 wind is nearly W. at 2'' p.m., and it is nearly SW. after midnight. The direction of the wind is nearest W, 

 about the time of maximum temperature, and ueai-est S. about the time of minimum temperature. The direction 

 of the wind, therefore, is most westerly when its velocity is gi-eatest, and most southerly when tlie velocity is 

 least. It is extremely probable that both facts may be explained by the greater descent of the upper current 

 when the air at the surface is mt)st rarified, i. e., at the time of maximum temperature. See remarks on the 

 motions of the different currents, after Tabic XXXVII. 



