88 Reviews — Mineral Resources of Great Britain. 



the conclusion that the solutions giving rise to the metasomatic 

 replacement of the Carboniferous Limestone travelled in the main 

 downwards from the overlying New Ked rocks ; the first stage 

 appears to have been the replacement of the tests of calcareous 

 micro-organisms by compounds of iron, this change afterwards 

 spreading to the fine-grained matrix and being accompanied or 

 followed by a certain amount of silicification. The close connexion 

 existing between ore-bodies and fault-fissures appears to be con- 

 clusive evidence of the truth of. this explanation. Even the lode-like 

 masses of haematite in the Skiddaw Slates and other ancient rocks 

 seem to have been formed by descending solutions. The " sops " 

 of Furness, which are obviously ancient pot-holes, were first filled 

 by calcareous breccia and afterwards metasomatized by iron 

 solutions, and there is no real support for the view that any ore- 

 bodies were deposited in cavernous open spaces in the limestone. 



The possible further underground extensions of the ore-field and 

 the amount of probable reserves are fully discussed, and 120 pages 

 are occupied by detailed descriptions of the mines, illustrated by 

 excellent diagrams of the forms of the ore-bodies and their 

 relations to varying rock-structures. It is estimated that the ore 

 proved to exist amounts to about forty-five million tons, while 

 probable reserves unproved, may be ninety milHon tons, most of 

 this being in Cumberland. The Lancashire field seems to be 

 rajjidly approaching exhaustion, only five million tons of ore being 

 actually known to exist. 



This memoir is an admirable example of the judicious combination 

 of scientific deduction and practical knowledge that is so highly 

 desirable in the literature of economic geology. R. H. R. 



Special Reports on the Mineral Resources op Great 

 Britain. Vol. IX, Iron Ores (cont.) : Sundry Unbedded 

 Ores op Durham, East Cumberland, North Wales, Derby- 

 shire, the Isle op Man, Bristol District, and Somerset, 

 Devon, and Cornwall. By T. C. Cantrill, R. L. Sherlock, 

 and H. Dewey. Mem. Geol. Surv. pp. 87, with 7 figs. 1919. 

 Price 3s. 6d. net. 

 TN this volume we have a useful collected account of some relatively 

 -*- unimportant sources of unbedded ores, partly in the form of 

 replacement deposits and partly as true mineral veins. Some of 

 the occurrences, as those of the Carboniferous Limestone of North 

 Wales, Derbyshire, North Somerset, and Devon, are similar in form 

 and origin to the great haematite deposits of North- Western England. 

 In the Isle of Man and in the Coal-measures of Bristol haamatite 

 occurs in veins, perhaps due to alteration of calcite and dolomite by 

 ferruginous waters from the Trias. The spathic vein-ore of West 

 Somerset, Devon, and Cornwall consists in depth of chalybite, con- 

 verted near the surface to limonite. In some places spathic ore is 



