Diurnal Variations for the Horizontal Cojjponent. 
xli 
Table 34. — DifiFerenees of Disturbed and Undisturbed Diurnal Variations of the Horizontal Com- 
ponent of Magnetic Force, as deduced from Tables 32 and 33, exhibiting the effect of Irregular 
Disturbance on the Hourly Mean Positions. 
Six Months. 
Mak. 
Alean 
Dec. 
Jan. 
i Sept. 
Oct. 
March. 
May. 
July. 
Sept. 
to 
Feb. 
March 
Twelve 
Time. 
Feb. 
April. 
June. 
Aug. 
Nov. 
to 
Aug. 
Months. 
h. m. 
0-00 
0-00 
O'OO 
0-00 
0-00 
O'OO 
0-00 
0-00 
12 12 
-0134 
-0221 
-0218 
-0075 
-0196 
— 0 I 7 1 
-0169 
1.3 12 
-0092 
-0404 
-0216 
-0189 
-0075 
— 0084. 
— 0970 
-0177 
14 12 
1 -0277 
-0647 
-0232 
-0226 
-0201 
— 09^Q 
— UODO 
-0304 
15 12 
-0108 
-0178 
-0210 
-0227 
-0032 
— 0070 
— 090'^ 
-0137 
16 12 
-0003 
-0172 
-0260 
-0240 
-0027 
— 001 
— 09 9d 
-0119 
17 12 
+ 0079 
-0143 
-0164 
-0304 
-0025 
4- 0097 
— 090-1 
-0087 
18 12 
+ 0113 
+ 0019 
-0136 
-0178 
-0015 
4- 004Q 
-0025 
19 12 
+ 0063 
-0038 
-0178 
- 0201 
-0093 
— 001 T 
— 0 1 1Q 
-0077 
20 12 
+ 0027 
-0179 
-0240 
-0247 
-0013 
I OOOfi 
— 0999 
— yj 
-0108 
21 12 
-0061 
-0143 
-0193 
-0244 
-0082 
— 0079 
— 0 1 Qd 
— yj 1 y^: 
-0134 
22 12 
-0040 
+ 0011 
-0162 
-0181 
+ 0006 
-0017 
-0111 
-0064 
23 12 
+ 0048 
+ 0042 
-0050 
-0083 
-0015 
+ 0016 
-0031 
-0007 
0 12 
+ 0022 
+ 0138 
+ 0062 
-0018 
+ 0140 
+ 0080 
+ 0061 
+ 0070 
1 12 
+ 0039 
+ 0305 
+ 0145 
+ 0064 
+ 0177 
+ 0107 
+ 0171 
+ 0140 1 
2 12 
+ 0107 
+ 0360 
+ 0330 
+ 0101 
+ 0199 
+ 0153 
+ 0264 
+ 0209 
3 12 
+ 0166 
+ 0334 
+ 0261 
+ 0310 
+ 0307 
+ 0236 
+ 0302 
+ 0269 
4 12 i 
+ 0136 
+ 0507 
+ 0514 
+ 0558 
+ 0202 
+ 0169 
+ 0526 
+ 0348 
5 12 
-0005 
+ 0524 
+ 0430 
+ 0669 
+ 0261 
+ 0128 
+ 0541 
+ 0334 
6 12 
+ 0052 
+ 0325 
+ 0393 
+ 0578 
+ 0112 
+ 0082 
+ 0432 
+ 0257 
7 12 
+ 0083 
+ 0054 
+ 0401 
+ 0318 
-0008 
+ 0038 
+ 0258 
+ 0148 
8 12 
+ 0075 
+ 0002 
+ 0155 
+ 0102 
-0106 
-0016 
+ 0086 
+ 0036 
9 12 
+ 0043 
-0129 
-0097 
-0093 
-0173 ! 
-0065 
-0107 
-0085 
10 12 
-0175 
-0235 
-0096 
-0063 
-0189 
-0182 
-0131 
-0157 
11 12 
- 
-0152 
-0142 
t 
-0253 
-0122 
-0167 
-0159 
-0173 
-0166 
73. The conclusions from Table 34 are, — 
1st, That the greatest effect of disturbance in increasing the horizontal component occurs 
In Dec. Jan. Feb. JIarch, April. May, June. July, Aug. Sept. Oct. Nov. 
About 3'' 20m P.M. and 6^ a.m. 4^ 40^^ p.m. 0™ p.m. 6^ 15™ p.m. 3^ 40™ p.m. 
In the months December to February there are two maxima of the positive effect of disturbance, the second 
maximum occurring about 6'^ a.m. ; this is also shewn, though less distinctly, in the quantities for March and 
April. The gi-eatest positive effect of disturbance occurs latest in July and August, and earliest in the months 
from September to February ; occurring throughout the year betwixt 3*^ p.m. and 5^ p.m. 
2d, That the greatest etfect of disturbance in diminishing the horizontal component occurs 
In Dec. Jan. Feb. March, April. May, June. July, Aug. Sept. Oct. Nov. 
About l'' A.M. A.M. 2^^ 30™ A.M. 40°^ A.M. ll'^P.M. 
i secondary negative maximum occurs in December to February, about 9^ 30™ a.m., and in March and April 
ibout 8^ 30™ A.M. The greatest negative effect of disturbance on the hourly mean position, occurs earliest in 
he months September to November, namely about 11^ p.m., it occurs farther and farther after that hour in 
ihe months following, till July and August, when it occurs about 5'' 40™ a.m. 
M, From what has been said, No. 72, the hours when the effect of disturbance is zero must be less certain, 
hey are from Table 34. 
i In Dec. Jan. Feb. March, April. May, June. July, Aug. Sept. Oct. Nov. 
ibout 41^ A.M. 10*1 A.M. 8^^ P.M. 1 Oh A.M. 8^ P.M. llll^ A.M. 81'^ P.M, 01'^ P.M. 81'' P.M. IP A.M. 7" P.M. 
