Revieics — Dr. Felix OsivalcVs Map of the Caucasus. 371 



He objects to the original tetrahedral theory on the ground 

 that radioactivity lias rendered it uncertain whether the earth 

 is growing cooler; but he quotes with approval the modification of 

 the tetrahedral theory advanced in 1899. He regards with most 

 favour the explanation that the great mountain chains are connected 

 with geosynclinal subsidences and with the gliding of the adjacent 

 areas under the influence of gravity. In the second part of his book, 

 having cleared the ground by his preliminary discussions, he considers 

 how mountains can be explained without invoking tangential pressure. 

 He advocates the view that subcrustal flow is the main agency in 

 mountain foi'mation. This conclusion was advanced byAmpferer, and 

 Dr. Andree warmly supports it and discusses its relations to isostasy, 

 the distribution of gravity, the structure and course of mountain 

 chains, the distribution of the Atlantic and Pacific lavas, and the 

 types of earthquakes classified as fracture-earthquakes and fold- 

 earthquakes. In his third section he considers the evidence for the 

 uplift of some areas into mountain chains at the present day, and 

 refers especially to that suggestion in regard to the meridional ridge 

 along the mid- Atlantic. He discusses the deep-sea material obtained 

 by the German Antarctic Expedition and its discovery of continental 

 sands on the floor of the South Atlantic, but he does not accept the 

 view that the mid-Atlantic ridge has been proved to be a rising 

 mountain chain. Like Abendanon he believes in the periodicity of 

 movements in the earth's crust with an alternation of epeirogenetic 

 and orogenetic movements. 



Both books are valuable contributions to the study of the formation 

 and distribution of the major features in the relief of the earth. 



J. W. G. 



II. — A Geological Map of the Catjcastjs. By Felix Oswald, D.Sc, 

 B.A., F.G.S., F.R.G.S. With Explanatory I^otes. Loudon: 

 Dulau & Co., Ltd., 1914. Price 15s. net. 



DIl. FELIX OSWALD is already well known in the geological 

 world by his treatise on The Geology of Armenia, published in 

 1906 (8vo, pp. ix, 516, with maps, plates, and sections), reviewed 

 in the Geological ^Magazine, 1906, pp. 562-3.' The map now 

 published has been compiled from the latest sources and is produced 

 in colour on the scale of 1 : 1,000,000 or 15-78 miles to the inch. 

 In the accompanying pamphlet of sixteen pages the author deals 

 first with the general structure of the range, he then gives an 

 account of its evolution, followed by an outline of the geological 

 succession. 



' In connexion with this map of Armenia it may be of interest to record that 

 Sir Archibald Geikie, when President of the Geological Society of London, 

 February 15, 1907, presented the " Murchison Geological Fund " to Dr. Felix 

 Oswald (awarded to him by the Council), in recognition of the value of his 

 contributions to our knowledge of the geology of Armenia in the remarkable 

 volume then recently published. A further note on Dr. Oswald's work on the 

 geology of Armenia will be found in the Geological Magazine for 1910, 

 p. 283. 



