Atmospheric Pressuee. 



423 



TABLE XXII. — Hourly Variations of the Height of the Barometer for each Astronomical Quarter, 



and for the year 1844. 



The epochs of maxima and minima, distinguishing the principal by + and 

 ters, and for the year, are as follow : — 



for the astronomical quar- 



Winter. 



Spring. 



Summer. 



Autumn. 



Year 



Nov., Dec, Jan., 



Feb., March, April,.. 



May, June, July, 



Aug., Sept., Oct., .. 



Min. 

 - 5" 40m A.ji. 

 -4 10 A.M. 

 3 10 A.M. 



-4 20 A.M. 



-4 10 A.M. 



Max. 

 + 10'nOmA.M. 

 11 10 A.M. 

 + 8 20 A.M. 



9 30 A.M. 



+ 10 A.M. 



Min, 

 2'i O"" P.M. 



3 10 P.M. 



-5 20 P.M. 



3 30 P.M. 



3 40 P.M. 



JIax. 

 9^ 50" P.M. 

 + 7 40 P.M. 

 12 P.M. 



+ 10 P.M. 



+ 9 40 P.M. 



The morning minimum occurs earliest in summer, and latest in winter. 



The morning maximum occurs earliest in summer, and latest in spring and winter. 



The afternoon minimum occurs latest in summer, and earliest in mnter. 



The evening maximum occurs latest in summer, and earliest in spring. 



The differences in the epochs appear to be related to the varying times of sunrise and sunset. 



The true times of mean pressure for the year from Table XXI. are, 12'^ 0™, T^ 40"' a.m., O"" 40™ p.m., 6'' 10" p.m. 



The times from Table XXII. are, l^ 17m a.m., 7*' 20'° a..m., 0'' 40"° p.m., 6'' 30™ p.m. 



The intervals between the times of mean pressure for the last case are, 6"^ 3™, 5^ 20™, 5^ 50™. 



Range of the Mean Diurnal Variation. — The ranges of the mean diurnal variation from Table XXI. are 



Jan. Feb. March. April. May. June. July. Aug. Sept. Oct. Nov. Dec. * 



in. in. in. in. in. in. in. in. in. in. in. in. 



0-022 0-057 0-057 0-021 0-038 0-018 0-038 0-032 0029 0-044 0-038 0-031 



The range of the mean variations was greatest in February, March, and October, and least in June and 

 January. The ranges of the means for the astronomical quarters, and the year, were 



in. 

 Winter, 0-028. 



Spring, 0-041. 



Summer, 0-030. 



Autumn, 0-026. 



The Year, 0-022. 



These ranges, however, are affected by the changes of mean pressure from day to day ; the following 

 ranges of the mean variations from Table XXII. are probably much nearer the truth : — 



Winter, 0-023. Spring, 0-023. 



Summer, 0-027. 



Autunm, 0-026. 



The Year, 0-016. 



