The Report of the Non-Ferrous Mining Committee 



TPvURING the last few months we have frequently referred in our 

 -■-^ Editorial Notes to the proceedings of the Board of Trade 

 Committee on the JN on-ferrous Mining Industry. This committee — 

 which was composed as follows : Mr. H. B. Betterton, M.P. (chair- 

 man), Mr. H. F. Collins, Mr. J. Harris, Dr. F. H. Hatch, Mr. R. A. 

 Thomas, Mr. J. Wignall, M.P., and Sir Lionel Phillips, who was 

 obliged to resign very soon after appointment — has now with com- 

 mendable promptitude issued its report, a document of much interest 

 from many points of view. While not primarily concerned with the 

 geological aspects of British non-ferrous mining, the Committee 

 have nevertheless investigated with some thoroughness certain 

 geological matters in connexion with the tin lodes of Cornwall, 

 the lead-zinc deposits of northern England, Scotland, and Wales, 

 and the barytes of Shropshire. A most interesting extract is given 

 from a report by Dr. Malcolm Maclaren to Messrs. Bewick, Moreing 

 and Co., on the central mines of the Camborne-Redruth area, 

 summarizing his views on the limits in de2:»th of profitable tin 

 working in that district. Dr. Maclaren points out that in most 

 instances there is a marked falling off in tin- content at an average 

 depth below the granite-killas contact of about 200 fathoms, or some 

 360 fathoms from the surface ; only in one case, the well-known 

 Dolcoath ore-body, did productive ore extend much below this ; 

 even this has failed at about the 500 fathom level. The facts here 

 summarized are entirely consistent with the views as to the existence 

 of definite mineral zones brought forward in the recent paper by 

 Dr. W. R. Jones at the Institution of Mining and Metallurgy, and 

 in the discussion on that paper hj Professor Cullis, Mr. Rastall, 

 Dr. Hatch, and other speakers. Favourable reference is also made 

 to the projects for exploration below the abandoned shallow mines 

 of this district by means of cross-cuts driven from the workings of 

 the larger and deeper mines. It is certain that the granite-killas 

 contact mi;st extend far to the north of its surface outcrop at no 

 very great depth ; there is every probability that this contact is 

 in point of fact an undulating one, and account must be taken of the 

 fact that granite again comes to the surface at St. Agnes, where also 

 there is well-develoi^ed mineralization. It seems probable that all 

 the granite bosses of Cornwall and Devon are in point of fact local 

 domes, cupolas in the American sense of the term, on the surface 

 of a great bathylith, underlying the whole region at a rather small 

 de|)th. It is of course uncertain what this actual depth may be, 

 and in places it is probably below the limit of working under present 

 conditions ; there is also the further fact to be taken into account 

 that in America it is believed that ore-minerals tend to concentrate 

 themselves in the upper parts of these cupolas. Hence it is not safe 

 to infer the existence of a tin-zone all over the upper surface of the 



