510 
MR. A. W. RUCKER AND DR. T. E. THORPE OR A MAGRETIC 
Inclination. 
The Dip observations were treated like those on the Declination and Horizontal 
Force. 
In the following Table the rates of change are expressed in terms of minutes of 
arc per degree of latitude and longitude respectively 
Ti^BLE VIL 
District. 
Central station. 
0\, 
do' 
_ do' 
^ ~ d\' 
Lat. N. 
Lon^. W. 
""“Iff- 
I. 
56 38-2 
O / 
4 21-5 
70 57-3 
.34 5 
6-7 
II. 
55 23-9 
3 23-7 
70 9-3 
31-9 
6-5 
III. 
53 24-2 
2 5-9 
68 53'6 
37-2 
6-3 
IV. 
61 47-4 
0 46 0 
67 42-2 
40T 
7-2 
V. 
54 2-7 
7 37-9 
69 52-6 
35-4 
8-2 
VI. 
53 30 5 
5 35-2 
69 19-5 
36T 
6-2 
VII. 
51 5-3 
3 8-0 
67 32-1 
41-4 
8-1 
VlII. 
52 51-5 
8 11-6 
69 II-9 
400 
6-8 
IX. 
51 41-9 
4 32-6 
68 5-2 
38-7 
6-6 
From these data the district curves were calculated as before. 
Details are given in Table VIII. (p. 518). 
The terrestrial curves were at first calculated for the whole kingdom from the 
formulae 
p = Z - 50°-855 + 0T833 (X - 4) 
-- 1-5 {0 — 67-5) + 0-055 {0 — 67-5'f, 
where 0 is the Dip expressed in degrees and fractions of a degree. 
If 6» is given, the latitude at which the corresponding isoclinal cuts any particular 
line of longitude can easily be found. 
If 6* is required, when I and X are given, is first found, and then by solving the 
quadratic we get 
0 = 53°-864 + 13^-636 ^/(l + 2^/l0-227). 
This formula agrees well with the district lines if the Dip is less than 71°, after 
that the <liscrepancy increases till at lat. 58° 30', long. 7°, it amounts to 9'‘6. 
This divergence between the general formula and the district lines affects only 
places north of the central station of our most northerly district (I), where on the 
one hand we have only the district lines of that region to rely upon, and on the 
other hand the accuracy of the lines is not checked by their overlapping those in 
