26 Reviews — Origin, Groiutli, and Decay of Mountains. 



distinguish them from, or rehite them to, those of other districts or 

 epochs. The problem is a very large one and does not admit of very 

 rigid treatment in the present state of our knowledge or ignorance. 

 It seems to us that no more convincing argument in favour of the views 

 of Judd, Harker, Prior, and Becke, has ever been brought forvi^ard 

 than Professor Iddings' calm and impartial summary of the facts. 

 The contrast furnished by the volcanic rocks of Africa, mainly 

 ' alkali-rocks', with a few andesites in the north-west part of the 

 continent, with the andesitic volcanoes of Japan, with a few centres 

 of alkali rocks on the western side, is as striking as the difference 

 between the broken plateau of Africa and the ridge-folds of Japan. 

 It is true there are many exceptions and anomalies, but these do not 

 affect the main issue. They show merely that there is much work 

 to be done in this field, many types and sub-types still to be defined 

 and established, and many disturbing factors to be taken into account. 

 It lends a new interest to petrology which seemed about to lose itself 

 in a wilderness of descriptive material, endlessly varied, but leading 

 to few wide generalizations. The application of exact methods to the 

 experimental synthesis of rocks and minerals and the study of 

 magmas in relation to the physical history of their province are the 

 most notable advances of the science of petrology in recent years. 



The second part of this volume, accordingly, is of the greatest 

 importance to students of petrology. Professor Iddings has spared 

 no labour to become acquainted with the facts at first hand, and he 

 marshals them in order and places them clearly before us. Many 

 small inaccuracies might be pointed out in the chapter on British 

 rocks, but these are mainly due to the imperfection of the descriptions 

 given by the older writers on the subject. The volume fills an 

 important gap in the list of books required by the student of rocks for 

 his daily work. 



III. — Mountains : their Origin, Growth, and Decay. By James 

 Geikie, LL.D., D.C.L., F.R.S., etc., Murchison Professor of 

 Geology and Mineralogy in the University of Edinburgh. 8vo ; 

 pp. xix, 313, with 81 plates and 57 text-illustrations. Edinburgh: 

 Oliver & Boyd. Price 12s. &d. net. 



SINCE the publication in 1886 of T. Mellard Reade's Origin of 

 Mountain Ranges there has not been issued in this country any 

 work dealing exclusively with this subject from a worldwide point 

 of view, although of course a mine of information is to be found in 

 the monumental work of Suess, Bas AntliU der Erde (English 

 translation, 1904-9). Of more recent works those on The Building 

 of the Alps by Professor Bonney, audi Earth Features and their Cleaning 

 by Professor "W. H. Hobbs, both published in 1912, have been 

 noticed in the Geological Magazine. The subject in those two 

 volumes is dealt with in a manner less severely scientific than that 

 of Mellard Reade, and this is the case with the handsome and profusely 

 illustrated volume before us. As remarked by Professor Geikie, all 

 that he has attempted "is such a comprehensive sketch as maybe 

 helpful to readers not specially versed in Geology, who desire a fuller 



