282 
MR. A, W. RtiCKER AND DR. T. E. THORPE ON A MAGNETIC 
Fig. 15 shows the true isogonals in this part of the country and proves that the 
form they assume corresponds to the last case. 
The existence of a widespread disturbance is proved not only by the remarkable 
bend in the 18° 10' isogonal between Kew and Reading, but also by several other 
stations. Thus the Declination at Harpenden is the same as that of Kew (18° 16'), 
though it is about thirty miles to the north of it and should therefore be 9' greater. 
Again, Ranmore, Haslemere and Alresford, with Declinations of 18° 9', 18° 8' and 
18° 10' prove that the 18° 10' line has really the great inclination to the meridian 
which the outer curves in fig. 6, p. 262, show. They are further supported by Horsham, 
Chichester, and Ryde, with Declinations of 18° 3', 18° 5' and 18° 2' respectively. 
The isoclinals and lines of equal Horizontal Force do not show any equally striking 
peculiarities in this part of the country. The latter, however, run a little too far 
north to the south of the Thames (see Plate VII.). This is as it should be, for to the 
south of an attracting centre the Horizontal Force will be abnormally great. 
Pig. 1.5. 
Isogonals in Sontli-Eastern England. 
The point at which the terrestrial and true isogonals would intersect if the district 
were not otherwise disturbed is marked by a dot, which will hereafter be called the 
focus of the Pteading disturbance. 
