SURVEY OF THE BRITISH ISLES FOR THE EPOCH JANUARY I, 1886. 307 
As we should expect from the close agreement of the Declination and Horizontal 
Force ridge lines the disturbing forces in this district are very easy to interpret. In 
no place in the kingdom is a locus of attraction more clearly indicated. At Appleby, 
Thirsk, Hull, and Mablethorpe the disturbing forces act in a south or south-easterly 
direction; at Giggleswick, Leeds, Gainsborough, and Lincoln they point north-east. 
A well-marked ridge line thus runs from the Lincolnshire Wolds through Yorkshire 
and the limestone district of Westmoreland to the Cumberland Lakes. 
Fig. 29. 
Ill the southern part of its course it traverses a region of high Vertical lorce, and 
passes near the station at which the positive disturbance is a maximum, terminating 
in the Wash peak. 
The observations at Manchester and Chesterfield appear to indicare another centre 
of attraction in the limestone district of Derbyshire, but two stations are hardly 
sufficient to decide such a point. It is, however, very significant that the limestones 
of Derbyshire are intercalated with the basaltic rocks known locally as “toadstones, 
and although these do not cover a great area at the surface it is by no means 
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