XCIV 
General Results of the Makerstoun Observations. 
Table 87. — Diurnal Variation of the Atmospheric Pressure for each Astronomical Season and 
for the Year, deduced from the observations of the Yeax-s 1843-6. 
Mak. 
Nov. 
Feb. 
May. 
Aug. 
1 
J,!ak. 
Nov. 
Feb. 
May. 
Aug. 
Mean 
Dec. 
March. 
June. 
Sept. 
Year. 
Mean 
Dec. 
March. 
June. 
Sept. 
Year. 
Time. 
.Jan. 
April. 
July. 
Oct. 
Time. 
Jan. 
April. 
July. 
Oct. 
h. 
m. 
in 
12 10 
+ •0026 
+ •0040 
+ •0040 
+ •0041 
+ •0037 
0 
10 
+ •0043 
+ •0051 
+ •0029 
+ •0008 
+ •0033 
1.3 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 
- •ooge 
- ^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 
+ •0036 
+ •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 
+ •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 11'^ and from 12'' to 1^, (instead of from 10'' to ll'' only) : the hourly means for each quarter wei'e 
then 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. 
Period. 
Minimum 
A. M. 
Interval 
from 
Min. 
to 
Max. 
Maximum 
A. M. 
Interval 
from 
Max. 
to 
Min. 
Minimum 
P. M. 
Interval 
from 
Min. 
to 
Max. 
Maximum 
p. M. 
Interval 
from 
Max. 
to 
Min. 
Jlean Epo 
the 
Maxima. 
ch betwixt 
rwo 
Minima. 
h. 111. 
h. m. 
h. m. 
h. m. 
h. m. 
h. ni. 
h. m. 
h. m. 
h. m. 
h. m. 
Nov. Dec. Jan. 
5 15 
5 10 
10 25 
3 40 
2 5 
6 55 
9 0 
8 15 
3 42 
9 40 
Feb. Mar. Apr. 
4 5 
7 0 
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 0 
4 15 
3 35 
10 5 
Aug. Sept. Oct. 
4 15 
4 45 
9 0 
6 50 
3 50 
6 10 
10 0 
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 0 
196. Diurnal Variation of the Atmospheric Pressure. — From Table 87, tliis consists of two maxima and 
two minima in each quarter of the year : the approximate epochs in apparent time, as deduced from tlie projoo- 
tions of Table 87 (see Plate IX.), arc given in Table 88. 
1st, The principal maximmn occurs in the evening in spring, and in tlie forenoon in the other quarters : 
the ])rincipal minimum occurs in the morning in winter and spring, and in the afternoon in summer antl 
antumn. 
2o', The morning minimum occurs eai-liest in sununor and latest in \\ intcr. obeying something like the law 
of sunrise, though the difl'erence of epochs is variable, the minimum oeeurring about 3 hours before smu'ise in 
winter, and inmicdiately befcn-e 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 tacts is more apparent than 
real, since the temperature of the air varies little in winter from 6'* r.M. till 8'^ a.m. 
'id, The morning maximum occurs latest in spi'ing and earliest in summer, the ilil!ereiu-e of the epochs 
ibr the two seasons beimr ncarlv three hours. 
