File:The Bakerian Lecture- A Magnetic Survey of the British Isles for the Epoch January 1, 1886 (1890) (14759557396).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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hat between neighbour-ing stations the rate of change of the disturbing force is uniform. The arrows repre-sent the Horizontal disturbing Forces in magnitude and direction. The dotted arrowsrepresent the disturbing forces calculated from Mr. Welshs survey. There are only two or three discrepancies, and they all occur, as we anticipated, nearvalley lines. The most remarkable is Stornoway. There can be no doubt as to the SUEVEY OF THE BBITISH ISLES FOR THE EPOCH JANUARY 1, 1886. 301 accuracy of our results obtained on three different occasions and at two stations, andwe can only suppose either that there has been a real change or that Mr. Welshsstation was subject to some very great local disturbance. Loehgoilhead, which ourobservations place just over the valley line in the next district is, according to Welsh,just within this. At Pitlochrie there is a large angle between the two forces. It isdoubtful whether the valley line is here correctly drawn. The region of high Vertical Fig. 25.
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Highland District, Force near Crieff seems to belong to the next district. At Crieff itself the disturbanceof the Vertical Force is a maximum, and there is probably a peak in the neighbour-hood. The direction of the Horizontal Force cannot therefore be deduced from theVertical Forces, and the fact that it happens to act northwards has perhaps led to itsbeing wrongly included in this district. If the valley line runs direct from Alford toLoehgoilhead it would pass close to Pitlochrie. Our result would thus make its 302 MR. A. W. RUCKER AND DR. T. E. THORPE OF A MAGNETIC relations uncertain, as the direction of the Horizontal Force would lie nearly alongthe valley line. The direction deduced from Welshs observation would place it inthe next district. The same remark applies, though more doubtfully, to Ardrishaig. If, however, these three or four border stations be put aside, the map leads to aconsistent view of the magnetic state of the district, which is in exact accord withthat previo

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