114 DR. A. H. COX; REPORT ON MAGNETIC DISTURBANCES IN NORTHAMPTONSHIRE 
(ii.) It has been shown to be highly probable that the Coal Measures extend under 
Melton Mowbray, seeing that they were proved to be 444 feet thick at Ruddington, 
six miles west of Owthorpe, and 800+ at Edwalton, nearer Owthorpe. Owthorpe 
itself is only ten miles north-north-east of Melton Mowbray, in which direction the 
Coal Measures strata are striking (p. 99). 
(iii. ) As regards Rempstone, the Coal Measures have not been proved nearer than 
Ruddington, five miles to the north, but it is known that the Carboniferous rocks 
approach nearer to the surface in a westward direction, as shown by their occurrence 
at 869 feet below O.D. at Owthorpe, 604 feet below O.D. at Edwalton, four miles 
west of Owthorpe, and at only 467 feet below O.D. at Ruddington, two miles further 
west. 
Carboniferous rocks may therefore well be present at Rempstone, and at a less 
depth than at Owthorpe, in which case an intrusive mass at a similar horizon would 
exert an influence greater in proportion to its bulk. 
(iv.) Basic rocks elsewhere usually show a high susceptibility. Rucker and 
White"^ determined the mean susceptibility of 45 specimens of basalts and dolerites 
from various parts of the British Isles as 255 x 10“^, and the mean of 12 from the 
northern counties as 340 x 10~h 
As a consequence of their high susceptibilities, basaltic rocks give rise to consider¬ 
able disturbances in those parts of the country where they are largely developed, 
as in Skye and Antrim. Further, Rucker and ThorpeI have shown that there 
is a distinct magnetic pull towards the coalfields of the Central Valley of Scotland, 
and they have given good reason for supposing that the pull is due to the abundance 
of basic igneous rocks in the coalfields. 
(v.) The susceptibility of ollvine-dolerites found as intrusions in the Midland 
Coal Measures is, in general, higher than that usual in dolerites and basalts. The 
difference is brought out by the following figures ;— 
Olivine-dolerite (marginal basaltic), Owthorpe, 
Nottinghamshire. 
Olivine-dolerite (central), Owthorpe, Notting¬ 
hamshire . 
Olivine-dolerite, Whitwick, Leicestershire . 
,, ,, Kelham, Nottinghamshire . 
,, ,, (lower portion), Kirklington, 
Nottinghamshire. 
Olivine-basalt (upper portion) Kirklington, 
N ottinghamshire. 
* ‘ Ro 3 ^ Soc. Proc.,’ vol. Ixiii. (1898), p. 
t ‘ Phil. Trans.,’ Ser. A, vol. 188 (1896), 
434x 10 
-5 
9 X 10-^ 
391 X lO-'' 
279x 10-' 
Determination by 
Prof E. Wilson 
(p. 84). 
210x 10 
-5 
7 X 10- 
466. 
pp. 621 and 653. 
