Atmospheric Pressure. 



423 



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



and for the year 1844. 



Mak. 

 M. T. 



Nov. 

 Dec. 



Feb. 

 March 



May 

 June 



Aug. 

 Sept. 



Year 



1844. 



Mak. 

 M. T. 



Nov. 

 Dec. 



Feb. 

 March 



May 

 June 



Aug. 

 Sept. 



Year 

 1844. 



Jan. 



April. 



July. 



Oct. 



Jan. 



April. 



July. 



Oct. 



h. 



in. 



in. 



in. 



in. 



in. 



h. 



tin. 



in. 



in. 



in. 



in. 



12 



0-0147 



0-0178 



0-0207 



00190 



0-0139 







0-0108 



0-0166 



00188 



00133 



0-0104 



13 



•0099 



•0124 



■0175 



•0150 



•0094 



1 



•0056 



•0145 



•0165 



•0113 



•0074 



14 



•0090 



•0068 



•0138 



•0086 



•0053 



2 



•0040 



•0108 



•0113 



•0093 



•0043 



15 



•0061 



•0027 



•0112 



■0030 



•0014 



3 



•0065 



•0093 



•0069 



•0070 



•0028 



16 



•0025 



•0000 



•0146 



■0000 



•0000 



4 



•0076 



•0106 



•0030 



■0080 



•0027 



17 



•0000 



•0019 



•0192 



•0013 



•0012 



5 



■0098 



•0134 



•0000 



•0100 



•0036 



18 



•0001 



•0041 



•0229 



•0066 



•0041 



6 



•0125 



•0173 



•0024 



•0160 



•0074 



19 



•0043 



•0079 



•0250 



•0130 



•0081 



7 



•0157 



■0225 



■0074 



•0206 



•0118 



20 



•0120 



•0128 



•0267 



•0166 



•0127 



8 



•0164 



•0227 



•0128 



•0253 



•0146 



21 



•0182 



•0154 



•0260 



•0196 



•0153 



9 



•0179 



•0220 



•0172 



■0256 



•0159 



22 



•0232 



•0169 



•0231 



• 0183 



•0160 



10 



•0183 



•0201 



•0185 



•0263 



•0160 



23 



•0184 



•0185 



•0205 



■0170 



•0141 



11 



•0165 



•0193 



•0196 



•0236 



•0149 



The epochs of maxima and minima, distinguishing the principal by 

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



+ and — , for the astronomical quar- 



Winter. Nov., Dec, Jan 



Spring. Feb., March, April,.. 



Summer. May, June, July, 



Autumn. Aug., Sept., Oct., . 

 Year 



Min. 



— 5 h 40 m a.m. 



-4 10 A.M. 

 3 10 A.M. 



-4 20 a.m. 



-4 10 A.M. 



Max. 

 + 10 h 10mA.M. 

 11 10 A.M. 



+ 8 20 a.m. 



9 30 a.m. 



+ 10 a.m. 



Min. 

 2 h m P.M. 

 3 10 p.m. 

 -5 20 p.m. 

 3 30 p.m. 

 3 40 p.m. 



Max. 



9 h 50 m 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 winter. 



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 h m , 7 h 40 m a.m., h 40 m p.m., 6 h 10 m p.m. 



The times from Table XXII. are, l h l7 m A.M., 7 h 20 m A.M., h 40 m p.m., 6 h 30 m p.m. 



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



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 0-029 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 



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 : — 



in. in. in. in. in. 



Winter, 0-023. Spring, 0-023. Summer, 0-027. Autumn, 0-026. The Year, 0-016. 



