280 
Abstracts of the Makerstoun Observations, 1843. 
that month; no observations having been made at 18 h in the second week, a correction 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, inclnded 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 h 10 m a.m. 4 h 10 m p.m. 10 h 40 m a.m. 3 h 30 m p.m. 
Summer, . . 9 h 0 m a.m. 5 h 10 m p.m. 9 h 0 m a.m. 5 h 0 m p.m. 
Autumn, . . 10 h 20 m a.m. 3 h 20 m p.m. 8 h 40 m a.m. 4 h 50 m p.m. 
Winter, . . 10 h 50 m a.m. 2 h 40 m p.m. 10 h 40 m a.m. 2 h 0 m 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 quarter. 
In the meteorological group, the principal maximum occurs at or after 9 h 10™ p.m. for Spring, Autumn, and 
Winter, and the principal minimum occurs at or before 5 h 10 m a.m. in Autumn and Winter. 
In the mean for the year, 
The principal minimum occurs at or before 5 h 10 m a.m. Makerstoun mean time. 
A maximum occurs at . . . 10 h 10 m a.m 
A minimum occurs at . . . 4 h 10 m p.m 
A maximum occurs at or after . . 9 b 10 m p.m 
The pressure at 5 h 10™ a.m. is very little less than that at 4 h 10 m p.m., and tbe pressure at 9 h 10 m pja. 
is exactly the same as at 9 h 10 m a.m., and ll h 10 m a.m. 
The mean pressure for the year occurs at 7 h 10 m a.m. 
0 h 54 m p.m. 
6 h 54 m p.m. 
The interval between the first two periods is 5 h 44 m 
second two periods is 6 h 0 m 
Range of the Mean Diurnal Variation of Atmospheric Pressure. — The greatest diurnal range for any 
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 
under 0-020 in., or about one-eleventh part of the mean of the diurnal ranges for the year. 
