Revieius — Earth Folds and Mountain Formation. 369 



of JE. scidatus, var. depressics. The significance of this distribution is 

 not necessarily very great, as specimens are only conspicuous on the 

 foreshore and there is relatively little chalk of the subzone of 

 abundant 0. pilida, and hardly any of the zone of A. quadratus 

 exposed on the foreshore. 



(To he contimted in our next Number.) 



I. — Earth Folds and Mountain Fokmation. 



1. E. C. Abendanon. Die Grossfalten der Erdrinde. With 

 a preface by Dr. K. Oestreich. pp. x, 183. Leiden, E. J. Brill; 

 London, Dulau & Co. : 1914. £5. 



2. K. Andree. Uber die Bedingungen der Gebiegsbildxjng. 

 pp. viii, 101. Berlin, Gebriider Borntraeger; London, 

 Dulau & Co.: 1914. Marks 3 Pfg. 20. 



rpHESE two works deal with special branches of geotectonic 

 JL principles and they have many points in common. They show 

 by the conclusions of their authors and by the extensive literature 

 quoted — the references to which are by no means exhaustive — the 

 steady growth of the belief that the main topographic features of the 

 earth are due to movements of the crust and not to denudation. They 

 both moreover agree in rejecting as a cause that great lateral thrusting 

 to which, in many graphic passages, Suess attributed the beliaviour 

 of the land during the elevation of the fold-mountains of Eurasia. 

 E. C. Abendanon, who is well known for his investigations in Mid- 

 China and the Dutch East Indies, in his work discusses the 

 ' Grossfalte ' or the great folds of the earth. 



' Grossfalte,' according to Abendanon, are broad uplifts due to the 

 sinking of "wider surrounding areas. He holds that all the main 

 movements in the crust are vertical. The larger, heavier, stronger 

 blocks sink and thereby force up the lighter, smaller, weaker blocks, 

 "which rise in flat swellings "wherein the material expands and is 

 under tension. ' Grossfalte ' are therefore torn by disruption 

 clefts and broken by rift-valleys, and overthrusting, due to the 

 outward flow of the upraised material, occurs on the edges of these 

 uplifted areas. 



The book has a preface by Professor Oestreich, of TJtrecht, who 

 cautiously declines to predict whether the term ' Grossfalte ' will 

 become naturalized in science. Abendanon's thesis is that the 

 formation of the major folds in the earth's crust is the most 

 important of geological processes. These folds he attributes to 

 vertical movements under the influence of gravity ; he denies 

 the great tangential thrusting assumed by Suess, and regards the 

 main folding as caused by tlie crumpling of the crust during the 

 shrinkage of the earth. The ' great folds ' include the subsidence 

 of the crust in geosynclines, its rise elsewhere in geanticlines, 

 and also extensive systems of faults. In consequence of these 



DECADE VI. — VOL. I.— NO. VIII. 24 



