SURVPJY OF THE BRITISH ISLES FOR THE EPOCH JANUARY I, 1891. 
G23 
it. It may be remarked that the directions of the Horizontal Disturbing Forces at 
Earlston and Greenlaw are more or less anomalous. At the former place tlie arrow 
points directly away from the neighboimng ridge line and towards a valley line. 
At Greenlaw it points away from the nearest high-level stations. It is, therefore, 
satisfactory to observe that in these, as in so many other cases, the anomalies occur 
at places where the Horizontal Disturbing Force is so small that its direction cannot 
be determined with accuracy. 
Its magnitude is only 0’0024 metric or 0'00024 C.G.S. unit at Greenlaw, and 
only O’OOOll C.G.S, unit (or about half the average error of two independent expe¬ 
riments) at Earlston. 
South of the Cheviots a fairly clear valley line runs from Bellingham to Alnmouth, 
which may, perhaps, be the true boundary of the Scotch Coal Field and Cheviot 
Disturbances. In the case of all the principal valley lines, however, the Horizontal 
Disturbances at most of the places through which they pass point straight away from 
the valley. In this case no such sudden change of direction is observed. The Hori¬ 
zontal Disturbing Forces point north on both sides of the valley, though, to the south 
of it, they begin to swerve to the east. The Bellingham-Alnmouth line must there¬ 
fore be considered as only of secondary importance, and, as we have already said, 
there is no clear breach of magnetic continuity from Dundee to Bedcar, i.c., from the 
Tay to the Tees. 
The main valley line is indeed prolonged southv^ards from Bedcar in a very 
remarkable way. It can be clearly traced running nearly parallel to the Yorkshire 
coast as far as Great Driffield, whence it no doubt passes eastwards towards the sea. 
The directions of the Horizontal Disturbing Forces at Durham, Bedcar, and 
Whitby seem to indicate a centre of attraction off the Durham coast. 
The enormous extension of this district southwards has led us a long way from the 
Scotch Coal Field, to which we must now return. 
The second principal new fact which has come to light with respect to it is a centre 
of very powerful Disturbing Forces at Newmilns. The Horizontal Disturbing Force 
points southwards and thus indicates that Newmilns is to the north of the true focus. 
Had it not been for this fact, it would have seemed most probable that the ridge 
passed in nearly a straight line about six miles south of Falkirk, Glasgow, and 
Cumbrae respectively. It is possible that it does, and that Newmilns is only subject 
to a powerful local disturbance. The facts, however, which makes us for the present 
adopt the contrary view are that New Cumnock, on the valley line, just south of 
Newmilns is near a col, the Vertical Disturbance being — 87 as against — 105 at 
Abington and — 138 at Loch Doon. 
It is true that this is not a very clear indication, the difference between New Cumnock 
and Abington being well within the limits of the error of experiment, but it is sup- 
j ported by the fact that the direction of the Horizontal Disturbing Force at New 
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