File:The Bakerian Lecture- A Magnetic Survey of the British Isles for the Epoch January 1, 1886 (1890) (14595813460).jpg

Identifier: philtrans08603087 (find matches)
Title: The Bakerian Lecture: A Magnetic Survey of the British Isles for the Epoch January 1, 1886
Year: 1890 (1890s)
Authors: Rucker, A. Thorpe, T.
Subjects: Proceedings of the Royal Society of London Philosophical Transactions of the Royal Society
Publisher: Royal Society of London

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Ireland from the 1837-87 surveysare inserted in the accompanying map (fig. 1). The general increase from east to west is evident, but in Great Britain there aresome stations the annual decrease at which is less than at those which are nearest tothem on the eastern side. To test whether the differences were accidental a number of supplementary stationswere taken on the Wye. At Malvern and Brecon the calculated secular rates between 1857 and 1886 are— l94 and — l*87, and at Clifton and Cardiff — I87 and — 185. In each case SURVEY OF THE BRITISH ISLES FOR THE EPOCH JANUARY 1,1886. 85 the smaller value occurs at the western station. Between them lie Hereford, Ross,and Chepstow, and the rates obtained from observations at these in April. 1889, are— l*85, — l*83, and — 184, which are in all cases less than those at Malvern andClifton. These observations then support the view that there is a real maximumfollowed by a minimum rate of change of Dip in this neighbourhood. Fig. 1.
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Secular change of Dip, 1858-86. This induces us to show in fig. 1 that if all stations at which there is a maximumrate of change are joined, we get two long lines running from Edinburgh to Exeter,and from Stornoway to Limerick. The stations are not sufficiently numerous toenable us to draw any certain conclusions about them, but the point ought not to belost sight of when the survey is repeated. For the present we note only that of the three pairs of neighbouring abnormalstations at which observations were made in all three surveys, all three are abnormal(in the sense that the rate of change is greater at the easterly station) whether wetake the interval 1837-87 or 1857-87. In both cases the rate at Inverness is greaterthan at Fort Augustus, at Glasgow than at Cumbrae, and at Berwick than atEdinburgh. 86 MR. A. W. RtJCKER AND DR. T. E. THORPE ON A MAGNETIC The distribution of these stations affords, at all events, prima facie evidence thatthe differences between them are not accidentaphiltrans08603087

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