564 Reviews — Professor JJoiinei/ — Building of the Alps. 



the distribution of land and sea leads on to a luminous account of tlie 

 tetrahedral theory of the earth. The chief points in tke earth's history 

 throu<>h the various geological periods are then dealt with, and the 

 geo<iraphical elements are traced in the existing continents and oceans. 

 Having considei'ed the main stages in the making of the earth, 

 Professor Gregory proceeds to discuss the biosphere, and finishes his 

 sketch with a delightfully speculative chapter on ' Protobion ' — the 

 jfirst living being on the earth. At the eml of the book is a 

 Bibliograpliy — in this case a particularly useful inclusion. The writer 

 of the geological volume for this series held a peculiar responsibility, 

 and we feel that in the ])resent work Professor Gregory has done 

 inucli that will help his readers to think geologically. 



II. — The Building of the Alps. By T. G. Bonnet, Sc.D., F.R.S., 

 Emeritus Pi'ofessor of Geology, University College, London. 8vo ; 

 pp. 384, with 32 plates and 16 text-illustrations. London: 

 T. Fibber Unwin, Adelphi Terrace, 1912. Price 12.s. 6d. net. 



IN this handsome volume, printed in large type, light in weight, and 

 admirably illustrated, Professor Bonney gives us a clear exposition 

 of the petrography, general structure, and mode of formation of the 

 great Alpine mountain region, followed by a description of the Glacial 

 phenomena and by remarks on some Alpine topics of modern times. 

 That he has come well-grounded to his task may be judged from the 

 fact that since 1856 he has spent an amount of time upon it equal to 

 nearly three years — in the earlier visits in walking and climbing and 

 observing more particularly the effects of ice-action, in later visits 

 (since 1880) in the investigation of rock-structures in the field, 

 supplemented by home-studies of tlie materials under the microscope. 



In his opening chapter the author deals with the geographical 

 distribution of the rocks, which may be broadly grouped into the 

 crvstalline and the obviously sedimentary. The oldest crystalline 

 rocks consist of gneisses and mica-schists, and these are followed by 

 a group of foliated rocks, comprising mica-schists, quartz-schists, 

 crystalline limestones, with serpentine, hornblendic and chloritic 

 rocks. Intrusive in these rocks are coarse granitoid gneisses which 

 often form a central position as the backbones of the higher mountains. 

 The loftier peaks and more prominent ridges are all formed of the 

 great series of crystalline rocks ; the sedimentary rocks in only one 

 instance attaining a height of 13,000 feet, in the limestone peak of 

 the Eiger. 



Avoiding so far as possible the use of technical terms, the author 

 briefly explains the origin of the crystalline rocks, all of which had 

 undergone great mechanical and chemical changes and assumed 

 a foliated condition prior to the vast movements that led to the 

 elevation of the mountains. He does not deny the possibility that 

 some gneisses may have been produced by the raetamorphism of 

 sediments, but he knows of no conclusive instance. He recognizes 

 a great break between the earliest of tbe sedimentary rocks and the 

 older gneisses and schists, remarking that the former have not 

 advanced in metamorphism beyond the stage of phyllite, or, in other 



