654 MR. A. W. RtrCKER AMI) DR. T. E. THORPE ON A MAGNETIC 
There are two principal exceptions, viz., the Cheviot and Berwickshire District, and 
the igneous rocks of Galway. These are marked by red dots in Maps 39 and 40 
respectively. 
The Cheviots and BerivicJcshire. 
It has already been shown that at Jedburgh, Kelso, and Wooler, the three stations 
nearest to the central mass of crystalline rock, the Vertical Force is large and the 
Horizontal Disturbing Forces tend inwards. 
The evidence may perhaps be put more strongly in another way. 
Greenlaw, Earlston, Selkirk, Hawick, Pticcarton Junction, Harbottle, Alnwick, and 
Wooler form a ring of eight stations surrounding but clear of the igneous rocks. Of 
these the four most distant are Selkirk, Hawick, Biccarton Junction, and Alnwick. 
The mean northerly component of the Horizontal Disturbing Force at the four 
nearer stations (expressed in terms of O'OOOl metric or O’OOOOl C.G.S. unit) is 35, 
and at the four more distant stations it is 41. The mean westerly components at the 
same two groups are 9 and 3 respectively. The two latter are both so small 
that it is evident that the mean Disturbing Force in the district acts almost due 
north. 
Ptegarding this as a regional disturbance due to the Scotch Coal Field ridge line, 
we may attempt to hud disturbances of the second order due only to the Cheviots 
and Berwickshire District, by subtracting the mean northerly and westerly components 
from those of each station separately. 
These values {n and iv') are shown in the next Table, together with the ano-le 
between the local Horizontal Disturbing Force and the geographical meridian. 
Jedburgh and Kelso, which are too much involved in the disturbed ground to be 
included in the list from which the mean disturbance w^as found, are treated in the 
same way. 
n. 
u\ 
n . 
w.' 
1 
9>'. ' 
Greenlaw. 
+ 14 
+ 20 
- 24 
+ 14 
1 
+ 150 1 
Earlston. 
+ 11 
0 
- 27 
— 6 
-167 1 
Selkirk. 
+ 70 
- 5 
+ 32 
-11 
- IS 
Hawick. 
-|- b3 
— 3 
+ 25 
- 9 
- 20 
Riccarton Junction 
+ 19 
+ 6 
- 19 
0 
±180 
Harbottle. 
+ 80 
-12 
+ 42 
-IS 
- 23 
Alnwick. 
+ 12 
+ 15 
- 26 
+ 9 
+ 161 
^VMoler. 
+ o4 
+ 28 
- 4 
+ 22 
+ 101 
]\Iean. 
+ 38 
+ 6 
Jedburgh . 
+ 63 
-29 
+ 25 
—35 
— 55 
Kelso. 
-162 
+ 79 
-200 
+ 73 
+ 160 
