Paper, 'On the relation between the magnetic permeability of rocks and regional magnetic disturbances' by A W [Arthur William] Rucker Rucker writes: 'The investigation, of which an account is given in this paper, was undertaken with the object of throwing light on the causes of local magnetic disturbances. The two main theories which have hitherto been proposed attribute local perturbations of the needle to earth currents and to magnetic rocks respectively. In the Bakerian Lecture for 1889 ('Phil. Trans.,' A. 1890, p. 53), Dr Thorpe and I compared the directions of the disturbing magnetic forces found by us to exist near Melton Mowbray and Reading with the results of a survey of the local earth currents made in the neighbourhood of those places under the direction of Mr Preece, F. R. S.' Annotations in pencil and ink. Includes three diagrams of experimental apparatus and measurements with corresponding engraved prints. Subject: Magnetism Received 30 May 1890. Read 19 June 1890. A version of this paper was published in volume 48 of the Proceedings of the Royal Society as 'On the relation between the magnetic permeability of rocks and regional magnetic disturbances'. 1890