The Bakerian Lecture: A Magnetic Survey of the British Isles for the Epoch January 1, 1886 . is a closeragreement in the methods of working up the results of the observations than thereis between our own and M. Moureauxs. Coming next to the 17° isogonal, we find that on the coast of Norfolk the calculatedDeclinations are generally much lower than the observed values. This would beremedied by moving the 17° isogonal further to the east, but the fact that it isalready to the east of M. Moure atjxs line is a strong argument against such a course. It is noticeable that Sir Fked. Evans appears to h
The Bakerian Lecture: A Magnetic Survey of the British Isles for the Epoch January 1, 1886 . is a closeragreement in the methods of working up the results of the observations than thereis between our own and M. Moureauxs. Coming next to the 17° isogonal, we find that on the coast of Norfolk the calculatedDeclinations are generally much lower than the observed values. This would beremedied by moving the 17° isogonal further to the east, but the fact that it isalready to the east of M. Moure atjxs line is a strong argument against such a course. It is noticeable that Sir Fked. Evans appears to have found some difficulty inthis part of the country (Phil 1872, vol 162, p. 330). His curves are shownin Plate II. The points at which the isogonals cut lat. 52° are given below,and it will be seen that the distance between them is a maximum in the centreof England. Isogonal (1872). Long. Difference ofLong. o 25 0 9-54 W. o 24 7-86 1-68 23 6-16 1-70 22 440 1*76 21 2*40 2-00 20 0-40 2-00 X «7 1-47 E. 1-87 SURVEY OF THE BRITISH ISLES FOR THE EPOCH JANUARY 1, 1886, 243 Fig. Isomagnetics in the border district of the English and French Surveys, R. and T., • — • — Moureaux, hypothetical connections. We think the agreement between our calculated and observed curves is too close toleave any doubt that in this and neighbouring latitudes the law that the distancebetween the points of intersection with a line of latitude is constant is very approxi-mately true. At all events, there is no trace of a change in this distance amountingto a quarter of a degree as is shown by the 1872 lines. As the observations on whichSir F. Evanss map were based were comparatively few in number and were madeexclusively at coast stations the accurate delineation of the isogonals was not makes the observed Declinations too small in the eastern counties. If thedistances between the isogonals had been kept constant the 19° line would have beenpushed further to the west, and a cl
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