DIURNAL VARIATIONS FOR THE HORIZONTAL COMPONENT. xli 
TABLE 34.—Differences 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. 
Twelve 
iia ata? 
KODOONAUKR WN © 
— 
73. The conclusions from Table 34 are,— 
1st, That the greatest effect of disturbance in increasing the horizontal component occurs 
In Dec. Jan. Feb. March, April. May, June. July, Aug. Sept. Oct. Nov. 
About 35 20m p.m. and 6" a.m. 4> 40™ pM. 54 Om p.m. 5) 15™ p.m. 35 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 greatest 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 effect of disturbance in diminishing the horizontal component occurs 
In Dec. Jan. Feb. March, April. May, June. July, Aug. Sept. Oct. Nov. 
About 12 aM. , 2) am. 2h 30™ a.m. 5h 40™ a.m. 11" p.m. 
A secondary negative maximum occurs in December to February, about 9" 30™ a.m., and in March and April 
about 8" 30™ a.m. The greatest negative effect of disturbance on the hourly mean position, occurs earliest in 
the months September to November, namely about 11» p.m., it occurs farther and farther after that hour in 
the months following, till July and August, when it occurs about 5° 40™ a.m. 
3d, From what has been said, No. 72, the hours when the effect of disturbance is zero must be less certain, 
they are from Table 34. 
In Dec. Jan. Feb. March, April. May, June. July, Aug. Sept. Oct. Nov. 
About 4% 4.0. 10? a.m. 88 p.m. 10h a.m. 8" pm. 1142 am. 83% p.m. Of> p.m. 832 pm. 11" a.m. 7" Pm. 
