DIuRNAL VARIATIONS FOR THE HorizonTAL COMPONENT. XXXIX 
and from October to September, the morning maximum becomes smaller in comparison with the afternoon 
maximum ; and in May and August there are traces of the former which wholly disappear in June and July. 
The forenoon minimum occurs earliest in August, and before 10" a.m. in the four months from June till Sep- 
tember ; it occurs latest in November and December, and after 10> a.m. in the seven months October till 
April: the afternoon maximum occurs earliest for the first six months of the year, in February, and for the 
last six months, in September; it occurs latest in June and December. In order to destroy the smaller ir- 
regularities, means for groups of months have been taken; the same groups have been used as those already 
adopted for the magnetic declination (No. 31). 
TABLE 32.—Diurnal Variations of the Horizontal Component of Magnetic Force for Different Periods, 
deduced from Table 31. 
Six Months. 
March. . Twelve 
April. A ; Months. 
KP COOMNAUARWNHRrO 
— 
70. The following are the approximate epochs of maxima and minima in apparent time from Table 32. 
(See also Plate IT.) 
Dec. Jan. Feb. March, April. May, June. July, Aug. Sept. Oct. Nov. 
Minimum, 10 20m 4m. 102 10™ aM. 10 Om a.m. 9h 35™ a.m. 105 Om 4m. 
Maximum, 4h (Om p.m. 55 15m p.m. 65 20™ p.m. 5h 45m p.m. 5h 50™ p.m, 
Minimum, Qh 0” a.m. RO De Ua, Ee UO dia cS Se Qh 0m a.m. 
Maximum, 6h 10™ a.m. DEAD M vacate wheats sec JoeA A ahh decane 5h 30™ aM. 
From these means of groups, the forenoon minimum occurs earliest in July and August, and latest in 
December to February; the afternoon maximum occurs earliest in December to February, and latest in May 
and June; the morning maximum occurs earliest in September to November, and latest in the three months 
thereafter ; the after-midnight minimum appears to occur generally about 2" a.m. 
The previous conclusions are obtained from the means of all the daily observations ; the following Table 
contains means for the same groups of months, deduced from the 10 days selected in each month of 1844 as 
free from intermittent disturbance, and the 10 days similarly selected for each month of 1845. See Table 
XXVIII, p. 362, 1844, and Table XXV., p. 14, of this volume. 
MAG. AND MET. oBs, 1845 anv 1846. k 
