Reviews — Natural Sources of Energy. 33 



The most important and older gold-veins are of late Cretaceous or 

 early Eocene age, and appear to be genetically related to the great 

 granitic intrusion. The younger gold-veins are enclosed in eruptive 

 rocks, principally rhyolites. 



VI. — Indo-China. 



YET another large area of the unknown geological world has been 

 explored by our friends and neighbours, whose labours are 

 being made known in the Memoires du Service geologique de I'lndo- 

 chine. Of, these beautiful publications we have received vol. i 

 (fasc. i), Etude geologique du Yun-Nan Oriental, by J. Deprat and 

 H. Mansuy, 4to, pp. 370, and nineteen exquisite plates of views 

 and one of rock-sections, with accompanying atlas of 178 sections and 

 many maps. Ease, ii, by H. Mansuy, deals with the palaeontology 

 (Cambrian to Trias, Tertiary Lignite and Quaternary), and contains 

 twenty-five excellent plates by Memin of Arcueil (Seine) ; fasc. iii, 

 by J. Deprat, is Etude des Funtilinides de Chine et d^ Indochine et 

 classification du Caleaires a Fusulines ; and fasc. iv treats of Laos and 

 Tonkin in the following papers: " Geologie des environs de Luang- 

 Prabang " ; "Mission Zeil dans le Laos septentrional, resultats 

 paleontologiques " ; and " Contribution a la geologic du Tonkin, 

 Paleontologie ", all by H. Mansuy ; the last illustrated by a series 

 of similarly beautiful plates. 



All these works seem to have been printed in Hanoi-Haiphong 

 and published in 1912, and it gives us peculiar satisfaction to call 

 tlie attention of the specialist to so rich a series of reference memoirs 

 on Far Eastern Asiatic fossils. 



VII. — Natural Sources of Energy. By A. H. Gibson, D.Sc, 

 Professor of Engineering in the University of St. Andrews, at 

 University College, Dundee. 8vo ; pp. viii, 131, with 17 

 illustrations. Cambridge : at tlie University Press, 1913. 

 Price Is. net. 



IN this little volume questions of general and worldwide interest 

 are discussed, some of them having a direct bearing on matters 

 of economic geology. The depletion of fossil fuels is in the first 

 place considered, and reference is made to the probable life of 

 British coal-fields, the lowest estimate being 175 years. Taking the 

 most recent available estimates for the world, the entire supply is 

 reckoned to be about 4,000,000 million tons. These immense 

 quantities of coal, at the present rate of consumption, and " allowing 

 for 33 per cent of wastage, Avould last some 2,500 years; whereas 

 should the consumption keep on increasing at the same arithmetical 

 rate as during the past five years they would be exhausted within 

 350 years". 



"With regard to oil fuel, while it is held by some authorities that 

 "the manufacture of oil in Nature's laboratory" is still in progress 

 through "the action of water vapour under high pressures upon 

 various metallic carbides ", yet it is considered that depletion would 



DECADE VI. — VOL. I.— NO. I. 3 



