SURVEY OF THE BRITISH ISLES FOR THE EPOCH JANUARY I, 1891. 625 
that the Galloway ridge line is crossed by the secondary line which runs from 
Ayrshire to the English Lakes. 
The Galloway line, clearly marked by secondary maxima of Vertical Force, is 
prolonged into the Scotch Coal Field District, as may be best seen by aid of Map 12. 
Its effect on the Horizontal Forces is negligible when compared with that of the main 
Scotch Coal Field line, but it can be traced to the north of the latter. It thus forms 
a continuous, though, in some pcirts, a weak chain of magnetic connection between 
Galloway and Forfar. 
Returning to Wigtonshire, the arrows drawn from the valley line, which passes 
through Stranraer, all point: straight at the ridge line to the south ; but, on the other 
side of the line, there is some confusion. At three stations, Whithorn, Kirkcud¬ 
bright, and Castle Douglas, the Horizontal Forces point—as we should expect—north, 
but at Wigtown and Parton, which are nearer to the ridge line, the Horizontal 
Disturbance acts parahel to or directly away from the ridge line. These stations, 
therefore, appear to be anomalous. There is little difficulty in explaining this. At 
Wigtown the magnitude of the Horizontal Disturbing Force is 0'00022 C.G.S. unit; 
at Parton it is 0‘00031. Hence, at one place it is less than, and at the other practically 
equal to the limit, below which considerable errors of direction are likely to occur. 
The same statement holds good of Kirkcudbright and Castle Douglas, while at Whit¬ 
horn the force, though larger, is still small (0'00056 C.G.S. unit). Hence there 
would be no reason for surprise if there were some discrepancies. As a matter of 
fact, however, the Vertical Disturbing Force is a little greater (algebraically) at 
Whithorn and Castle Douglas than at Wigtown and Parton. The difference is 
less than the possible error of experiment, but it occurs twice over, and suggests the 
possible existence of a minor ridge line parallel to the chief one and passing near 
these places. If this were so, the anomalies at Wigtown and Parton would be 
accounted for, but we cannot insist on an explanation, which, in view of the small 
Horizontal Disturbances, is hardly needed, and itself depends on differences too small 
to be trustworthy. 
District 9. —The English Lakes. 
This district, though not large, is complicated. Two stations in the centre, viz. : 
Keswick and Hesket Newmarket are places of moderately high Vertical Force, and 
the directions of the arrows prove that the centre of attraction is between them. 
They lie on a continuation of the weak ridge line, which crosses the Galloway 
district from north to south, and appears to enter the next district to the south of the 
English Lakes in Eskdale. The evidence on this last point is doubtful, as the Eskdale 
stations are not a mile apart, and the Horizontal Disturbing F'orces at both are very 
small. There are also suggestions that another ridge line crosses the district from 
east to west. 
The Vertical Force does not indeed indicate it, but the directions of the Horizontal 
MDCCCXCVI.—A. 4 I 
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