280 Abstracts of the Makerstoun Observations, 1843. 



that month ; no observations having been made at 18*^ in the second week, a con-ection was applied to the 

 mean for that hour of — 0'327 in., obtained from Table XV. as follows : — 



{Mean pressure, Jan. 9 — 31, = 29-271 in. minus mean pressure, Jan. 16 — 31, = 29-598 in.} = — 0-327 in. 



The means were afterwards corrected by + 0-090 in., in order to render the mean for the month from 

 these means equal to that obtained. Table XV., from all the daily means. 



Diurnal Variation of the Atmospheric Pressure, — The means for the majority of the months indicate the 

 existence of two maxima and two minima ; the periods of only one maximum and one minimum can be deter- 

 mined from the nine observations. The means for the month of November present the greatest departure 

 from the usual diurnal variation ; in that month the pressure increases continuously from 5 a.m. till 9 p.m. The 

 following are the periods of the maximum and minimum, included in the observations from 5 a.m. till 9 p.m., 

 for the mean meteorological and astronomical seasons. 



Mean Meteorological Seasons. Astronomical Seasons. 



Maximum. Minimum. Maximum. Minimum. 



Spring, . . 9'> 10™ a.m. 4'» 10™ p.m. 10^^ 40™. a.m. 3^ 30™ p.m. 



Summer, . . g*" 0™ a.m. 5^ 10™ p.m. %^ 0™ a.m. b^ 0™ p.m. 



Autumn, . . lO'^ 20™ a.m. 3^ 20™ p.m. 8'^ 40™ a.m. 4.^ 50™ p.m. 



Winter, . .10'^ 60™ a.m. 2^ 40™ p.m. 10^ 40™ a.m. 2'^ 0™ p.m. 



The maximum seems to occur earliest in the warmest quarter, and the minimum latest in the same 

 quarter ; the maximum also occurs latest in the coldest quarter, and the minimum earliest in the same quai-ter. 

 In the meteorological group, the principal maximum occurs at or after 9'' 10™ p.m. for Spring, Autumn, and 

 Winter, and the principal minimum occurs at or before 5** 10™ a.m. in Autumn and Winter. 



In the mean for the year. 



The principal minimum occurs at or before 5'' 10™ a.m. Makerstoun mean time. 



A maximum occurs at . . . 10*^ 10™ a.m 



A minimum occurs at ... 4** 10™ p.m 



A maximum occurs at or after . . 9'' 10™ p.m 



The pressure at 5*^ 10™ a.m. is very little less than that at 4*" 10™ p.m., and the pressure at 9"^ 10™ p.m, 

 is exactly the same as at 9^* 10™ a.m., and ll'^ 10™ a.m. 



The mean pressure for the year occurs at 7** 10™ a.m. 



0*^ 54™ p.m. 



6^ 54™ P.M. 



The interval between the first two periods is 5'' 44™ 

 : second two periods is 6** 0™ 



Range of the Mean Diurnal Variation of Atmospheric Pressure. — The greatest diurnal ranffe for anv 

 month is that for November, being 0-072 in. ; the least is that for June, being 0-019 in. The diurnal range is 

 greatest in Winter and least in Summer. The diurnal range of the quarterly means is greatest in Winter 

 (whatever mode of grouping be adopted) ; it is least in Spring for the meteorological groups, and least in 

 Summer of the astronomical group ; the result for the latter is therefore the same as already obtained. Table 

 XVII., for the mean of the diurnal ranges. The diurnal range of the means for the year 1843 is probably 

 iinder 0-020 in., or about one-eleventh part of the mean of the diurnal ranges for the year. 



