The Bakerian Lecture: A Magnetic Survey of the British Isles for the Epoch January 1, 1886 . E 9876543ZIS Terrestrial Isogonals running approximately north and south. True Isogonals produced by (Fig. 4) a weak, and (Fig. 5) a strong centre of attraction at A, Fig, 6. f. - Terrestrial Isogonals approximately parallel. - True Isogonals produced by a centre of attraction at A. It is, of course; quite possible that a single closed curve may sometimes be underground attracting surface, rising up steeply on the eastern side and fallingaway very gently to the west, might cause a maximum dec
The Bakerian Lecture: A Magnetic Survey of the British Isles for the Epoch January 1, 1886 . E 9876543ZIS Terrestrial Isogonals running approximately north and south. True Isogonals produced by (Fig. 4) a weak, and (Fig. 5) a strong centre of attraction at A, Fig, 6. f. - Terrestrial Isogonals approximately parallel. - True Isogonals produced by a centre of attraction at A. It is, of course; quite possible that a single closed curve may sometimes be underground attracting surface, rising up steeply on the eastern side and fallingaway very gently to the west, might cause a maximum declination on the eastwithout any corresponding minimum on the west; but in general the normal comple-ment of a closed isogonal is another of the same type. The curves shown in figs. 3 to 6 will not be realised in practice, but their main SURVEY OF THE BRITISH ISLES FOR THE EPOCH JANUARY 1, 1886. 263 characteristics may be reproduced, and a knowledge of their forms is very useful ininterpreting maps on which the true isomagnetic curves are drawn. These facts may also be illustrated by means of diagrams of another kind. Thus if,in figs, 7 and 8, the s]ope of the line AD represents the normal rate of increase of theDeclination with longitude, the effect of an attrac
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectproceed, bookyear1890
