76 DE. A. H. COX: EEPORT ON MAGNETIC DISTURBANCES IN NORTHAMPTONSHIRE 
whether the observed magnetic disturbances are connected in this case with the ore 
deposits now being worked is obvious. 
It was accordingly decided by the Iron-ore Committee (l) that a detailed magnetic 
survey of the Melton Mowbray district should be undertaken ; (2) that at the same 
time a geological examination of the district should be made; and (3) that the rocks 
collected in the district should be tested for their magnetic susceptibilities, with a 
view to determining the origin of the local magnetic disturbances, and to ascertain 
their connexion, if any, with the distribution of the known iron-ore deposits. The 
magnetic survey was undertaken by Mr. Walker with the aid of a grant from the 
Royal Society. The geological aspect of the question was placed in the hands of 
Dr. Aubrey Strahan, Director of the Geological Survey, who obtained the sanction 
of H.M. Treasury for the employment of Dr. A. H. Cox as a temporary member of 
the staff of the Geological Survey in order that he might carry out the geological 
part of the work. The work of determining the magnetic susceptibilities of the 
various rocks collected was undertaken by Prof. Ernest Wilson, of University of 
London, King’s College. 
The geological examination of the district was greatly facilitated by the fact that 
the whole area had recently been re-surveyed by the officers of H.M. Geological 
Survey, and the results of their investigations shown on the Geological Maps and 
Memoirs (list on p. 94). 
It was thought desirable that a series of observations should also be made on some 
known sheet of iron-ore with a view to determining the character of the disturbances 
caused by the sheet. The district selected on the advice of Prof. H. Louis, the 
Chairman of the Committee, was near Irthlingborough in Northamptonshire. This 
district was chosen as being the largest sheet of unworked ferrous carbonate known 
to him suitable for the experiment, as its boundaries had been determined with great 
accuracy. It is now being opened out by the Ebbw Vale Iron Company. Accord¬ 
ingly a series of similar observations was made in that district also by Mr. Walker, 
Dr. Cox, and Prof. Wilson. During this examination the most valuable assistance 
and information were received from Mr. Thos. Falcon, Manager of the Ebbw Vale 
Company’s iron-mines at Irthlingborough, and it is desired to take this opportunity 
of expressing our great indebtedness to him for the facilities so freely granted. 
Method of Procedure. 
It should be borne in mind that the disturbances to be measured were exceedingly 
small as compared with those set up by some of the ore-deposits in Sweden,^ where 
* For an account of the procedure adopted in Sweden, see “ The Most Prominent Features of Swedish 
Iron-ore Mining,” by G. Nordenstrom, ‘ Journ. Iron and Steel Inst.,’ 1898, p. 35; also “ On the Location 
and Examination of Magnetic Ore Deposits by Magnetometric Measurements,” by Eugene Haanel, 
Ottawa, Canada, 1904. 
