Pressure of the Wind. 



289 



TABLE XXVI. 



-Means of the Maximum Pressures of Wind between the Hours of Observation for 

 each Month and Quarter of 1843. 



Period. 



10h_18i'. 



18b_20''. 



aoi"— 22''. 



221' — Oi. 



Ob— 2h. 



2ii 411. 



4i>_6h. 



ei-— sb. 



Sh— 10b. 



Range. 





lb. 



lb. 



lb. 



lb. 



lb. 



lb. 



lb. 



lb. 



lb. 



lb. 



January 



2-56 



2-29 



207 



2-42 



2-40 



1-94 



1-71 



2-08 



1-60 



0-82 



February- 



1-96 



1-32 



1-61 



1-40 



1-50 



1-60 



1-79 



1-20 



Ml 



0-68 



March 



0-89 



0-39 



0-43 



0-67 



0-97 



1-00 



0-71 



0-43 



0-41 



0-61 



April 



0-87 



0-61 



1-04 



1-26 



1-33 



1-38 



112 



0-78 



0-56 



0-82 



May 



0-86 



0-47 



0-69 



0-86 



102 



107 



106 



0-82 



0-52 



0-60 



June 



0-75 



0-56 



0-72 



0-78 



1-08 



102 



0-92 



0-82 



0-53 



0-55 



July 



0-85 



0-37 



0-64 



0-75 



0-95 



109 



0-91 



0-72 



0-46 



0-72 



August 



0-37 



016 



0-42 



0-54 



0-80 



0-74 



0-62 



0-50 



0-28 



0-64 



September 



0-40 



0-18 



0-35 



0-60 



0-71 



0-71 



0-47 



0-22 



0-16 



0-55 



October 



1-60 



0-76 



0-80 



1-25 



1-30 



0-94 



0-79 



062 



0-62 



0-68 



November 



1-48 



103 



109 



1-38 



1-41 



Ml 



0-72 



0-53 



0-69 



0-88 



December 



1-93 



M9 



1-48 



1-41 



1-60 



1-33 



1-42 



1-58 



1-35 



0-41 



Spring 



0-87 



0-49 



0-72 



0-93 



Ml 



115 



0-96 



0-68 



0-50 



0-66 



Summer 



0-66 



0-36 



0-59 



0-69 



0-94 



0-95 



0-82 



0-68 



0-42 



0-59 



Autumn 



116 



0-66 



0-75 



1-08 



114 



0-92 



0-66 



0-46 



0-49 



0-68 



Winter 



215 



1-60 



1-72 



1-74 



1-83 



1-62 



1-64 



1-62 



1-35 



0-48 



The Year 



1-21 



0-78 



0-95 



Ml 



1-26 



116 



102 



0-86 



0-69 



0-57 



The observations in tlie first week of January were not made use of in obtaining the hourly means for that 

 month in Tables XXVI. and XXVII. No observations having been made at 18^ in the second week, a cor- 

 rection was applied to the mean for that hour of —0-11 in Table XXVI., and of —0-14 in Table XXVII., 

 obtained from Tables XXIII. and XXIV. as follows : — 



{Mean pressure, January 9 — 31 = 2-21 minus mean pressure, January 16 — 31 = 2-32} = — Oil. 



{Mean pressure, January 9 — 31 = 1-43 minus mean pressure, January 16—31 = 1'57} = — 0-14. 



The means for January in Tables XXVI. and XXVII. are further corrected by —0-15 and —0-10 re- 

 spectively, in order to render the means for that month equal to those obtained Tables XXIII. and XXIV. 



Diurnal Variation of the Maximum Pressure of Wind. — ■The means for the months of January, February, 

 and December are very irregular, presenting two or three maxima and two or three minima within tlie nine daily 

 observations ; in the other months only one maximum is evident, occurring between 1 1 a.m. and 2 p.m. The 

 minimum occurs after 9 p.m. and before 7 a.m. The following are the interpolated hours for the maximum for 

 the mean meteorological and astronomical seasons, obtained on the assumption tbat the means correspond to 

 the middle of the interval to which they belong ; for example, that the mean of the maximum pressures occur- 

 ring betwixt 0'' and 2'* correspond to l'^ : — * 



Seasons. Mean Meteorological. Astronomical. 



Spring, . . I'' 20™ p.m. 1^ 40™ p.m. Makerstoun mean time. 



Summer, . . l^^ 10™ p.m. 1^ 20™ p.m 



Autumn, . . ll^* 10™ p.m. Ill' 30™ a.m 



Winter, . . O'' 10™ p.m. ll'' 30™ a.m , 



The maximum pressures occur latest in the day in Spring, and earliest in Autumn and Winter. 



A secondary minimum and maximum occur in Winter of the meteorological group about 2** p.m. and 4'' p.m. 

 respectively, and in Winter of the astronomical group about 4*^ p.m. and 6'^ p.m. respectively. 



The maximum in the diurnal variation for the year occurs at O'' 30™ p.m. The value of the maximum 

 pressure increases regularly from &^ 10™ a.m. till O'' 30™ p.m. at the rate of 008 lb. per hour, and it diminishes 

 from O*' 30™ p.m. till &" 10™ at the same rate. 



* This assumption is obviously inexact, as the means of the maximum pressures, while the pressure is increasing, will most pro- 

 bably belong to nearly the termination of the periods in which they occur, but since, while the pressure is diminishing, they will 

 probably correspond to nearly the commencement of the periods, the interpolated time of maximum will not be affected by the error 

 of the hypothesis. 



MAG. AND MET. OBS. 1843. 4 D 



