Heviews — Geology of Tavistock and Launceston. 227 



Silurian', but of older Palaeozoic age than the Yeryan Series, which 

 is regarded as Ordovician by Mr. Howard Fox.' 



These questions, dealt with mostly in footnotes by the author, 

 are not of great concern in connexion with the main object of his 

 work. With regard to the age of the ore-deposits he states : " That 

 much of the iron oxide, iron and copper sulphide, and oxide of 

 manganese of the Devonian and Carboniferous rocks appears to be 

 pre-granitic in origin. On the other hand there is very little reason 

 for supposing that there was any tin in the rocks before the granite 

 was intruded." 



The mode of occurrence of the ore-deposits, the earth-folds and 

 faults, together with the granite intrusions, are described, and full 

 particulars are given of the carbonas, stockworks, and floors. The 

 lode-fillings and modifications in adjacent country rocks, the sources 

 and distribution of ores and vein-stones, the relative ages of elvans 

 and lodes, and the detrital ore-deposits all receive attention. 



The area dealt with extends from Ashburton in Devon to the 

 Land's End, and the author gives a general account of each mining 

 district or chief group of mines, with instructive details illustrated 

 by maps, sections, and plans of particular mines, the district of 

 Camborne and Illogan being regarded as " almost equal in importance 

 to all the remainder of the regions taken together". Outlying 

 mineral areas are likewise dealt with, including the Brendon Hill 

 iron-lodes, the Brixham iron-mines, the Upton Pyne manganese-ore, 

 etc. Subterranean water-circulation and thermal waters are also 

 described. There is an Alphabetical List of Mines, with statistics 

 of production ; and there are tables of the occurrence of minerals in 

 different rocks and in successive deposits in veins or fissures. A good 

 index completes this eminently practical volume. 



II. — Geological Sukvet of Great Bkitain. 



1. The Geology of the Country around Tavistoce: and Launceston. 

 By Clement Reid, F.R.S., G. Barrow, F.G.S., II. L. Sherlock, 

 D.Sc, D. A. MacAlister, A.R.S.M., and Henry Dewey, F.G.S, 

 8vo ; pp. vi, 144, with 3 plates and 48 text-illustrations. 1911. 

 Price 3s. 



A GLANCE at the excellent colour -printed map (Sheet 337, 

 price Is. 6d. net) which accompanies this memoir indicates the 

 many important additions made to our knowledge of the country since 

 the 1 inch geological map of De la Beche was published. The 

 contrast is shown in the subdivisions of the igneous and metamorphic 

 rocks in the Culm Measures and valley deposits ; at the same time 

 not so many divisions are distinguished on the map as are stated 

 in the table (p. 2) to be so represented. There is no doubt that 

 the area is one of the most difficult in Britain to interpret owing to 

 successive earth -movements prior to and dni'ing the intrusion of the 

 granite masses, and subsequently. So that with faulting, irregular 



^ See J. B. Hill and D. A. MacAlister, Geology of Falmouth and Truro 

 (Geol. Survey), 1906, pp. 15, 19. 



