330 Reviews — Mineral Resources of Great Britain. 



have undergone important changes and developments since the 

 appearance of the second edition in 1898. No doubt it would be 

 possible to pick out individual examples of omissions of recent work, 

 but this is not the real object of this review, which is to give a general 

 impression of the book as a whole, and in this case the general 

 impression is excellent. The sections on physical properties in 

 general have been revised, and the part dealing with optics has been 

 largely rewritten and greatly improved. Concerning crystallography, 

 the most important addition is the introduction of the methods 

 employed in the use of the stereographic and gnonomic projections, 

 and Appendix A, on crystal-drawing, has been largely rewritten. 

 Appendix B has been greatly enlarged by the addition of an elaborate 

 table of minerals arranged according to chemical composition, 

 which will be useful to those desiring to ascertain all possible sources 

 of some given element. For these days the book is decidedly cheap. 



Special Reports on the Mineral Resources of Great Britain. 

 Vol. XX, Lead and Zinc. The Mining District of North 

 Cardiganshire and West Montgomeryshire. By 0. T. 

 Jones, M.A., D.Sc, Mem. Geol. Survey, pp. vi + 205, with 

 xxvii plates, 4 text-figures, and a coloured map. 1922. Price 

 75. net. 

 rpHE publication of this report has been anticipated with much 

 -*- interest by mining geologists. Professor Jones was admirably 

 qualified for the task of writmg it by his intimate knowledge of the 

 structure and stratigraphy of this region, which he has made 

 peculiarly his own, and the Geological Survey is to be congratulated 

 on having secured his services for the purpose. He brings out with 

 the utmost clearness the close connexion between the folding and 

 faulting of the area and the distribution of the ore-deposits, which 

 have been in the past of great importance and still contain 

 possibilities of extensive development under more favourable 

 economic conditions. The mineralized veins are entirely confined 

 to the Bala and Llandovery strata, but these alone are estimated to 

 be 10,000 feet thick, and practically all the payable lodes are faults 

 or shatter-belts striking approximately east and west. The relation- 

 ship between folding, faulting, and ore-deposition is close, and 

 Professor Jones is inclined to attribute the mineralization to the later 

 phases of the Caledonian earth-movements, although there is no 

 positive proof. Some of the later faults which displace the lodes may 

 be of Hercynian origin. 



This report is an excellent addition to this most valuable series. 

 Without wishing in any way to be ungracious, we venture to raise 

 a protest against the intolerable and cumbersome length of the 

 official titles of many of these reports, which are a perfect nightmare 

 to bibliographers and to authors wishing to quote them in footnotes. 

 It will eventually be necessary to devise some shorter form of 

 reference than the strictly orthodox designation, as set out at the 



