XCIV 



General Results of the Makeestoun Observations. 



Table 87. — Diurnal Variation of the Atmospheric Pressure for each Astrotiomical Season and 

 for the Year, deduced from the observations of the Years 1843-6. 



Mak. 



Nov. 



Feb. 



May. 



Aug. 





Mak. 



Nov. 



Feb. 



Mav. 



Aug. 





Mean 



Dec. 



March. 



June. 



Sept. 



Year. 



Mean 



Dec. 



March. 



June. 



Sept. 



Year. 



Time. 



.h. m. 



Jan. 



April. 



July. 



Oct. 





Time. 



Jan. 



April. 



July. 



Oct. 





in. 



in. 



in. 



in. 



in. 



h. m. 



in. 



in. 



in. 



in. 



in. 



12 10 



+ •0026 



+ •0040 



+ •0040 



+ •0041 ; 



+ •0037 



10 



+ •0043 



+ •0051 



+ •0029 



+ •0008 



+ 0033 



13 10 



-•0041 



-•0013 



+ •0010 



+ •0013 



-•0008 



1 10 



-•0005 



+ •0011 



+ •0003 -•0036 



-•0007 



14 10 



-•0055 



-•0057 



-•0028 



- ^0023 



-•0041 



2 10 



-•0029 



-•0038 



-•0035 !-^0073 



- -0043 



15 10 



-•0108 



-•0112 



- ^0047 



-•0058 



-•0081 



3 10 



-•0010 



-•0062 



-0080 --0106 



-0064 



16 10 



-•0159 



-•0135 



-•0025 



-•0073 



-•0098 



4 10 



+ •0017 



-•0059 



-•0117 !-^0113 



-•0068 



17 10 



-•0179 



-•0122 



+ •0016 



-•0043 



-•0082 



5 10 



+ •0034 



-•0030 



-•0136 



-•0097 



-•0057 



18 10 



-•0158 



-•0092 



+ •0049 



+ •0009 



-■0048 



6 10 



+ •0060 



+ •0013 



-•0103 



-•0047 



-0019 



19 10 



- ^0096 



-•0043 



+ •0075 



+ •0057 



-•0002 



7 10 



+ •0073 



+ •0078 



-•0060 



+ •0004 



+ ^0024 



20 10 



-•0012 



+ •0008 



+ •0091 



+ •0082 



+ •0042 



8 10 



+ •0085 



+ •0108 



-•0006 



+ •0051 



+ •0059 



21 10 



+ •0060 



+ •oose 



+ •0082 



+ •0091 



+ •0067 



9 10 



+ •0095 



+ •0107 



+ •0024 



+ •0068 



+ 0073 



22 10 



+ •0122 



+ •0059 



+ •0071 



+ •0074 



+ •0081 



10 10 



+ •0078 



+ •0092 



+ •0044 



+ •0072 



+ •0071 



23 10 1 



+ •0098 



+ •0075 



+ •0056 



+ •0048 



+ •0069 



11 10 : 



+ •0066 



+ •0075 



+ •0051 



+ -0060 



-f -0063 



Table 87 has been formed thus : — The hourly means for each quarter were obtained for each year ; those for 

 1844 and 1845 were corrected for continuous barometric change as described in the volume for 1844, p. 422, 

 excepting that the change of pressure from 11'' to 12'\ was considered equal to the mean of the changes from 

 lO'' to IP and from 12'' to 1'', (instead of from lO"^ to ll'* only) : the hourly means for each quarter were 

 tlien combined in the manner already described for the magnetic declination. No. 26. 



Table 88. — Daily Epochs of Maximum and Minimum Atmospheric Pressure, with the Intervals 

 from Epoch to Epoch, for each Quarter, and for the Year. 







Interval 

 from 





Interval 

 from 





Interval 

 from 





Interval 

 from 



Mean Epoch betwixt 



Period. 



Minimum 



Min. 



Maximum 



Max. 



Minimum 



Min. 



Maximum 



Max. 



the Two 





A. M. 



to 

 Max. 



A. M. 



to 

 Min. 



p. M. 



to 

 Max. 



P.M. 



to 

 Min. 



Maxima. 



Minima. 





li. m. 



li. m. 



h. in. 



h. m. 



h. m. 



h. m. 



li. m. 



h. m. 



h. m. 



h. ni. 



Nov. Dec. Jan. 



5 15 



5 10 



10 25 



3 40 



2 5 



6 55 



9 



8 15 



3 42 



9 40 



Feb. Mar. Apr. 



4 5 



7 



11 5 



4 15 



3 20 



5 10 



8 30 



7 35 



3 47 



9 42 



May June July 



3 15 



4 55 



8 10 



8 45 



4 55 



6 5 



11 



4 15 



3 35 



10 5 



Aug. Sept. Oct. 



4 15 



4 45 



9 



6 50 



3 50 



6 10 



10 



6 15 



3 30 



10 2 



Year 



4 10 



6 10 



10 20 



5 30 



3 50 



5 40 



9 30 



6 40 



3 55 



10 



196. Diurnal Variation of the Atmospheric Pressure. — From Table 87, this consists of two maxima and 

 two minima in each quarter of the year : the approximate epochs in apparent time, as deduced from the projec- 

 tions of Table 87 (see Plate IX.), are given in Table 88. 



\st. The principal maximum occurs in the evening in spring, and in the forenoon in the other quarters ; 

 the principal minimum occurs in the morning in winter and spring, and in the afternoon in summer and 

 autumn. 



2d, The morning minimum occurs earliest in summer and latest in winter, obeying something like the law 

 of suni'ise, though the difference of epochs is variable, the minimum occurring about 3 hours before sunrise in 

 winter, and irnmediately before sunrise in summer : the epoch of minimum temperature had a nearly similar 

 relation to that of sunrise, but the similarity of the relations of the two classes of facts is more apparent than 

 real, since the temperature of the air varies little in winter from 6'' p.m. till 8^ a.m. 



3(i, The morning maximum occurs latest in spring and earliest in summer, the difference of the epochs 

 for the two seasons being nearly three hours. 



