lxiv ' GENERAL RESULTS OF THE MAKERSTOUN OBSERVATIONS. 
131. Diurnal Variation of the Effect of Disturbance on the Magnetic Dip—A remark, similar to that 
made No. 72, with reference to the horizontal component, will apply to Table 60. The conclusions from this 
Table are as follow :— 
1st, The greatest effect of disturbance in increasing the magnetic dip occurs 
In Dec, Jan. Feb. March, April. May, June. July, Aug. Sept. Oct Nov. 
123” a.m. 13> a.m. h a gyn 9? a.m. 95 PM. 
sae { 93> aM. 835 a.m. ee 92 p.m. 10° p.m. 
There are two epochs in May and June at which the positive effect of disturbance is a maximum, and there 
are two similar epochs for each group of months, for one of which either the positive effect is a secondary maxi- 
mum, or the negative effect is a minimum ; the times of these are given above, in the second line. 
2d, The greatest effect of disturbance in diminishing the magnetic dip occurs 
In Dec. Jan. Feb. March, April. May, June. July, Aug. Sept. Oct. Noy. 
4" pM. 4) p.m 5b PM. 
h h M. b bh 
About {8 A.M, and 3" p.m. ree Pig a 12" pu 335 a.m. and 3? pm. 
In the winter groups there are two nearly equal maxima for the negative effect of disturbance, and in each of 
the others there is, besides the principal maximum, either a secondary maximum of the negative effect, or a 
minimum of the positive effect ; the times of these are given above in the second line, 
3d, The effect of disturbance upon the hourly mean magnetic dip is zero 
In Dec. Jan. Feb. March, April. May, June. July, Aug. Sept. Oct. Nov. 
About 10% a.M., 7) P.M., 3 A.M. 7% a.M., 10> a.M., 75 P.M. Noon, 95 p.m. 15 p.m., 85 P.M. 10> a.M., 6» P.M., 1» A.M. 
The best defined hours are those from 6" p.m. to 92 p.m., and from 10" a.m. to 1" p.m. 
See No. 76 for the probable law of mean disturbance for the magnetic dip, substituting for positive distur- 
bance of the horizontal component, negative disturbance of dip, and vice versa. 
TABLE 61.—Variations of the Magnetic Dip with reference to the Moon’s Hour-Angle for the Winter 
and Summer Lunations, and for all the Lunations of the Years 1844 and 1845. 
2 Winter Lunations. Summer Lunations. All the Lunations. 
Moon’s 
Angle. | : 5. , , 1845. Mean. : 1845. || Mean. 
Hour- | - Fe 
’ 
-045 
| 
S 
= 
i) 
b+++1 
Beas ed 
++t41 
Heke tt a 
132. Variations of the Magnetic Dip with Reference to the Moon's Howr-Angle.—The four independent 
columns of Table 61, give results quite analogous to those obtained for the horizontal component of magnetic 
force, No. 79: the results for the winter lunations of 1844, and for the summer Junations of both years, agree 
very nearly with that for the mean of both years in the last column of Table 61,—which may be stated as 
follows :— 
The magnetic dip is a minimum about 1 hour after the moon's inferior transit. 
weet eeee ene eee ee maximum about 84 hours before the moon’s superior transit. 
minimum about 23 hours after the moon’s superior transit. 
maximum about 8 hours after the moon’s superior transit. 
