XXV1 GENERAL RESULTS OF THE MAKERSTOUN OBSERVATIONS. 
41. If we consider the mean position as deduced from all the observations in each month, we find that the 
number of observations for which the declination was to the west, is least from 6" a.m. to 10" s.m., and greatest 
from 6" p.at. to 10" p.m.; the reverse of course holding for the deviations to the east : if, however, we consider 
the hourly mean position deduced from the days selected free from disturbance, we find that the number of 
westerly observations is greatest from about 9” a.m, till noon, and that it is least from 8» p.m. till 1" a.m. ; which 
result is nearly the reverse of the other. As the maximum effect of disturbance, in increasing the westerly 
declination (No. 36), occurs about the same time as the maximum frequency of westerly excursions from the 
undisturbed position (as seen in the second result), the displacement westerly of the mean position, by dis- 
turbance, reduces the number of westerly excursions from that position to a minimum (as seen in the first 
result). The same explanation applies to the other epoch. 
Diurnal Variation of the Sums of Disturbances of the Hourly values of Magnetic Declination in 1844 and 
1845,—The following table contains the sums, for 100 observations, of the deviations of the north end of the 
declination magnet from the monthly mean positions at the corresponding hours, the latter being deduced from 
the days selected as free from irregular disturbance. 
TABLE 17.—Hourly sums, for 100 Observations of Westerly Declination in 1844 and 1845, of the 
Positive and Negative Excursions from the Approximate Normal Positions for each Hour. 
Positive (W.) Disturbances. Negative (E.) Disturbances. 
May. Aug. Nov. Feb. May. Aug. 
June. Sept. Dec. March, | June. Sept. 
July. Oct. Jan. April. | July. Oct. 
101 305 259 339 
107 253 
157 f 215 
177 159 
141 172 
225 134 
286 116 
294 118 
344 80 
335 77 
260 66 
260 98 
250 88 
250 99 
268 81 
244 109 
197 108 
157 113 
123 125 
97 168 
70 194 
52 170 
62 158 
87 220 
RK OOM AUNrwWNr SO 
oe 
42, The results from the Table are as follows :— 
1st, The sum of positive or westerly disturbances 
In Nov. Dec. Jan. Feb. March, April. May, June, July. Aug. Sept. Oct. 
Is a maximum at 0 Noon. 9h a.m. and 2 p.m. 10h a.m. 83 a.m. 
Isa minimum at 11" p.m. 8 p.w.—11> p.m. 83> p.m. 92 pM. 
2d, The sum of negative or easterly disturbances 
Is a maximum at 85—115 p.m. 9h pM. 123h a.m. 91> p.m. 
Isa minimum at 8" a.m. 7> a.m.—10® a.m. 10" a.m. 8» «.m.—0Oh Noon. 
