Ixviii 
General Results of the Makerstoun Observations. 
In the disturbed diui'nal variation of total magnetic force, the principal maximum occurred latest in the 
quarter December to February, and earliest in the quarter September to November ; the epoch of the 
after-midnight minimum varied little, being slightly nearer midnight in May and June than in the other 
groups ; the secondaiy maximum occurred earliest in May and June, and latest in September to November ; 
and the forenoon minimum occurred earliest in the quarter December to February, and latest in May and June. 
In May and June, therefore, the one minimum occurred nearest noon, the other nearest midnight. (See 
the Continuous Curves, Plate V.) 
Table 64. — Diurnal Variations of the Total Magnetic Force for Different Periods, deduced from 
Days selected as free from Irregular Disturbances, in the Years 1844 and 1845. 
Six Months. 
Mak. 
Dec. 
jVIarch. 
April. 
Mav 
June. 
July 
Aug. 
Sept. 
Twelve 
Months. 
Mean 
Time. 
Jan. 
Feb. 
Oct. 
5ov. 
Sept. to 
March 
Feb. 
to Aug. 
h: m. 
O'OO 
0-00 
0-00 
0-00 
0-00 
0-00 
000 
0-00 
12 13 
-0016 
-0029 
- 0031 
-0032 
-0051 
-0033 
-0031 
— 0034 
13 13 
-0037 
- 0043 
-0039 
-0047 
-0059 
-0048 
- 0043 
- 0045 
14 13 
— 0041 
-0027 
-0034 
-0049 
-0049 , 
-0045 
-0037 
-0040 
15 13 
-0038 
- 0023 
-0014 
-0027 
-0042 
-0040 
-0021 
-0030 
16 13 
-0031 
-0025 
+ 0011 
+ 0003 
-0032 
-0031 
-0004 
-0018 
17 13 
-0022 
-0004 
+ 0021 
+ 0010 
-0022 
-0022 
+ 0009 
-0007 
18 13 
-0022 
+ 0010 
+ 0012 
+ 0009 
- 0023 
-0022 
+ 0010 
-0006 
19 13 
-0023 
+ 0009 
-0016 
-0030 
-0024 
-0023 
-0012 
-0018 
20 13 
-0025 
-0019 
-0077 
-0103 
-0063 
-0044 
-0066 
1 -0055 
21 13 
-0045 
- 0080 
-0162 
-0169 
-0107 
-0076 
-0137 
1 -0106 
22 13 
-0061 
-0151 
-0229 
-0204 
-0146 
-0103 
-0195 
-0149 
23 13 
-0056 
-0182 
-0251 
-0218 
-0125 
-0090 
-0217 
' -0154 
0 13 
-0028 
-0181 
-0200 
-0176 
-0089 
-0058 
-0186 
-0122 
1 13 
+ 0017 
-0100 
-0105 
-0084 
-0002 
+ 0007 
-0096 
-0044 
2 13 
+ 0053 
-0005 
-0024 
+ 0013 
+ 0075 
+ 0064 
-0005 
+ 0029 
3 13 
+ 0071 
+ 0069 
+ 0064 
+ 0108 
+ 0126 
+ 0098 
+ 0080 
+ 0089 
4 13 
+ 0075 
+ 0113 
+ 0139 
+ 0157 
+ 0152 
+ 0113 
+ 0136 
+ 0125 
5 13 
+ 0069 
+ 0143 
+ 0201 
+ 0196 
+ 0140 
+ 0104 
+ 0180 
+ 0142 
6 13 
+ 0059 
+ 0145 
+ 0215 
+ 0197 
+ 0126 
+ 0092 
+ 0186 
+ 0139 
7 13 
+ 0048 
+ 0137 
+ 0199 
+ 0176 
+ 0103 
+ 0075 
+ 0171 
+ 0123 
8 13 
+ 0039 
+ 0105 
+ 0160 
+ 0145 
+ 0086 
+ 0062 
+ 0137 
+ 0099 
9 13 
+ 0032 
+ 0080 
+ 0106 
+ 0086 
+ 0051 
+ 0041 
+ 0091 
+ 0066 
10 13 
+ 0016 
+ 0050 
+ 0045 
+ 0042 
+ 0016 
+ 0016 
+ 0046 
+ 0030 
11 13 
-0014 
+ 0008 
0000 
-0004 
-0036 
-0025 
+ 0001 
-0012 
144. When we consider the diurnal variation, as deduced from days selected as nearly free from intermit- 
tent disturbance, and as exhibited in Table 64, and in the dotted curves, Plate V., we find the approximate epochs 
in apparent time as follow : — 
Dec. Jan. Feb. Jlarch, April. May, June. July, Aug. Sept. Oct. Xov. 
Maxhnum, + 4^ 0'" p.m. + o"^ 40"' p.m. + 6'^ 0™ p.m. + o'' 35™ p.m. + 4'^ 15™ p.m. 
Minimum, l'^ 40™ a.m. 1'' 10™ a.m. 1'' 30™ a.m. 1'' 40™ a.m. 1'^ -25™ a.m. 
Maximum, .5^' 35™ a.m. 6'' 45™ a.m. 5'' 15™ a.m. 5'' 35™ .v.m. 6'^ 20™ a.m. 
Minimum, -10'' 35™ a.m. —IP 45™ a.m. -10'' 55™ a.m. —10'' 55™ a.m. —10'' 30™ a.m. 
'VW. undisturbed diurnal variation of the total magnetic force dvii'ors considerably from that affected by dis- 
ttu'bances, as may be seen at a glance in Plate V. ; the whole variations of the epochs of maxima and minima, 
with season, are different from those obtained. No. 143. In each group of months, the forenoon minimum is 
the principal, and the after-midnight minimum is quite secondary. Tlie principal maxinuun occurs earliest in 
winter, about 4'' P.M., and latest in May and June, about 6'' p.m.; the principal minimum occurs earliest 
in the six months, September to February, and latest in March and April : the secondary ma.ximum ocoui-s 
nearest noon, and the secondary minimum nearest midnijrht. in tlie equinoctial months. 
