DIURNAL VARIATIONS FOR THE TOTAL MAGNETIC FORCE. lxix 
TABLE 65.—Differences of Disturbed and Undisturbed Diurnal Variations of the Total Magnetic Force, 
as deduced from Tables 63 and 64, exhibiting the effect of Irregular Disturbance on the Hourly 
Mean Positions. 
Six Months. 
| 
| OS 
March. | May. Twelve 
April. | June. ; F ee cMutie, 
Aug. 
0-00 . y | 0-00 
— 0207 | | — 0140 
— 0206 —0159 
—0261 | — 0192 
—0184 | — 0169 
—0155 E —0150 
-—0121 —0130 
—0077 | | —0091 
—0055 | | — 0065 
— 0047 | — 0048 
—0031 | —0027 
0000 | | 4 — 0006 
+0034 | 
+0079 
+0100 +0069 
+0135 
+0167 | 
+0192 | 
+0265 
+0254 
+0188 
+0105 
— 0006 
— 0095 
— 0082 
RK SOOCOONOUK WHE oO 
_—a 
145. Diurnal Variation of the Effect of Disturbance on the Total Magnetic Force. The remark made 
No. 102, for the vertical component, will apply also to the following conclusions obtained from Table 65. 
1st, The greatest effect of disturbance in increasing the total magnetic force occurs 
In Dec. Jan. Feb. March, April. May, June. July, Aug. Sept. Oct. Noy. 
About 6 30™ P.M. 5 30™ p.m. 65 15™ p.m, 5 40m p.m, 54 10™ p.m. 
The hours, it will be seen, agree very nearly with those found as the epochs of the maximum total force in the 
disturbed diurnal variation. The maximum positive effect of disturbance on the total force, occurs latest near 
the solstices and earliest near the equinoxes. 
2d, The greatest effect of disturbance in diminishing the total magnetic force occurs 
In Dec, Jan. Feb. March, April. May, June. July, Aug. Sept. Oct. Nov. 
About 2h 0™ A.M. 2h 15™ am. 3h Om am. 2h 45m a.m. 25 10™ am. 
These hours are nearly the same as those for the after-midnight minimum of the diurnal variation; the 
difference is greatest in the summer months when the maximum negative effect occurs latest. 
3d, The effect of disturbance on the total magnetic force is zero 
In Dec. Jan. Feb. March, April. May, June. July, Aug. Sept. Oct. Noy. 
hat f 10® 45™ a.m. 105 15™ a.m. 10® 10™ a.m. 115 15™ aM. 9» 45™ am. 
l 95 40™ p.m. 9» 10™ p.m. 10® 15™ p.m. 95 30™ p.m, 8h 45m pm. 
The one of these epochs is nearly the same as that of the principal minimum in the undisturbed diurnal varia- 
tion ; the other occurs about twelve hours after. 
