1898] GEOGRAPHICAL EVOLUTION 121 



caiiic phenomena, Suess concludes that, in the processes of the earth's 

 contraction by cooling, vast subterranean hollows are left, which are 

 usually filled by a sinking of the superficial crust ; wliile owing to tan- 

 gential thrusts caused by the contraction of the outer crust, violent 

 foldings are produced along certain lines. In some cases, the lateral 

 thrusts and the vertical subsidences are combined; but Professor Suess 

 can find no agency that will account for the uplift of large areas in 

 mass and undisturbed. 



The rest of the present volume is devoted to a series of descrip- 

 tive chapters on the mountain system of the world. They are of 

 high value as a summary of knowledge of the geology of the world 

 up to the date at which the book was written ; while M. de Mar'^erie 

 and his collaborators have introduced a series of footnotes, giving 

 additional references to literature, and, in some places, incorporated 

 important additions in the text. The descriptions are of high value, 

 not only as a statement of facts, but for the original insight which 

 enables Professor Suess to point out the connection of distant and now 

 isolated areas. The author begins with a description of the Alpine 

 system and adjoining country geologically connected with it, of the 

 fundamental geological structure of the middle zone of Europe. He 

 describes the main structural lines of the Alps and of the great 

 plateau belt (the Alpine Vorland), which sweeps across Europe from 

 the high, treeless wastes of the Spanish meseta, the chateau-crowned 

 crags of the central plateau of France, and the pine-clad " horsts " of 

 the Schwarzwald and Thuringia, into the level, wind-swept Eussian 

 plain. Eastward he follows the Alps into the multiserial chains of 

 ' the world's white roof-tree ' of Northern India and Thibet. South 

 of the Alpine area he describes the subsided trough of the Adriatic, 

 and the great basin of the Mediterranean ; he shows that the latter 

 is only the eastern arm of a long sea, which once extended from the 

 Levant to Yucatan, and from the central part of which the Atlantic 

 grew by the gradual enlargement of two gulfs that ran out north 

 and south. South of the Mediterranean is the great tropical table- 

 land ; its northern part forms the deserts of the Sahara, Kordofan 

 -and Arabia ; the rest forms the great block of equatorial Africa, 

 which once probably extended eastward to Southern India and west- 

 ward to join the similar eastern highlands of Brazil. 



In this manner Professor Suess sketches out the development of 

 existing continents. From the high standpoint of his wide knowledge, 

 by the far-reaching penetration of his mental vision, he surveys all 

 the mountains of the world ; with splendid self-restraint he leaves 

 behind him the temptation to premature theory ; and he clearly 

 brings out the essential facts upon which any theory of geo- 

 graphical evolution must be based. Into the apparently bewildering 

 variety of topographic accidents he introduces harmony, bringing 



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