Ixxiv GENERAL RESULTS OF THE MAKERSTOUN OBSERVATIONS. 
these remarks may be kept in view, in considering the numbers in the following Table, which are obtained from 
Plate VIII. 
TasLeE 68.—Angular Distances between the Disturbed and Undisturbed Positions for each Hour in the 
motion of a freely-suspended Dipping-Needle, as obtained from Plate VIII. 
Mak. i ept. Sept. March ~ 
nee 5 a March. miuye July. ae be a From 
Time. || Feb. ees Aue. Nov. Feb. Aug. Mean | of first 5 
Curve. Columns. 
h. a ’ e , 2 a y ‘ 
12 || 0-36 0-20 0-34 0-28 0-36 0-35 0.25 0-32 
13 26 32 26 +24 28 28 31 26 
14 28 46 20 18 14 18 28 24 
15 09 16 16 -06 12 08 12 08 
16 06 04 18 -08 12 09 09 04 
17 15 08 08 +24 14 13 14 08 
18 | 21 20 08 +32 34 25 18 22 
19 20 24 14 +32 40 29 22 26 
20 18 30 30 -46 42 29 34 28 
21 22 36 28 +30 40 30 32 32 
22 24 28 26 +20 26 28 22 28 
23 24 -30 | 16 +36 +26 24 18 24 
0 28 28 | 12 14 +30 26 18 22 
1 35 +24 28 16 +24 28 24 28 
2 36 +36 40 16 38 34 30 34 
3 29 +32 26 +24 +36 30 28 28 
d 28 44 46 44 “16 40 44 32 
5 | 12 -30 34 +50 12 04 35 18 
6} 15 +36 30 -42 +32 19 28 16 
7 18 42 =| 30 26 38 27 22 24 
8 43 36 16 24 58 50 24 38 
9. | 38 38 24 44 44 38 34 38 
10 39 38 30 +36 “52 45 34 40 
11 42 +26 38 +22 50 45 32 38 
166. The following are the conclusions from Table 68 :— 
lst, In the two figures for the months from September to February, the effect of disturbance in displacing 
the needle is a minimum about 4" a.m. and 4" p.m., the values for these hours being nearly equal, or near the 
hours when the sun is on the magnetic prime vertical. The maximum effect of disturbance occurs in both about 
10" p.m., when the sun is on the magnetic meridian, a secondary maximum occurring in the figure December to 
February about 13 p.m., and in the figure September to November about 8} a.m. 
2d, In the figure for March—April, the minimum occurs about 4" a.m., and the maximum probably about 
85-10" p.m., the value, however, varying little for the 18 hours from 8» a.m. till 2? a.m. 
3d, The mean of the two results for the figures May—June and July—August is to some extent the reverse 
of the result for December to February. The effect of disturbance is a minimum about 4" a.m., and about 
noon ; it is a maximum about 8" a.m. and 4" p.m. It would appear, therefore, that the diurnal law of the 
effect of disturbance varies with season as well as the law of the amount of disturbance (see Nos. 45,77, 110) : 
a minimum is also shewn about 8» p.m. 
4th, In all months of the year the effect of disturbance is a minimum about 4" a.m. In the winter months 
a minimum occurs at 44 p.m., the maximum occurs at the same hour in the summer months. 
5th, Inthe mean figure for the year, minima occur at 4" a.m. and about 53" p.m., the maximum occurs about 
105 p.m,, and a maximum occurs between 8" a.m. and 45 p.m, If, making allowance for the effect of dis- 
turbance on the position of the centre of gravity with reference to dip (No. 121), we suppose the centre of 
gravity of the dotted figure for the year (Plate VIII.) raised 0’-16 on the line of mean declination, or that of 
the continuous figures lowered as much, we find the maximum effect of disturbance to occur about 10" p.m. 
and 10" a.m., and the minimum effect about 4" a.m. and 5" p.m. This result was obtained for the magnetic de- 
clination in 1844, See the Volume for that year, p. 345, 
