REVIEWS. 
Der Bau DER ErRpDE. By L. Koper. pp. 324, with 2 plates, and 
46 text-figures. Berlin: Gebriider Borntraeger. 1921. Price 
80 marks. 
(ae speculations on the plan of the earth, the distribution 
of land and sea, of mountain ranges, and other geographical 
features; are a subject of never-failing interest, most students of 
geology have come to the conclusion that life is not long enough to 
read Suess. The Face of the Earth is heavy going in any one of the 
three versions, the conclusions are not always clear, parts are out 
of date, and, owing to the long period that elapsed between the 
appearance of the first and last volumes the author's views had 
necessarily undergone important changes. In recent years many 
new facts have come to light and prevalent ideas have had to undergo 
revision. The book under review gives in small compass a summaty 
of the present state of our knowledge on the structural features of 
the earth. It cannot be described as altogether an impartial state- 
ment, since the author is obviously arguing in favour of his own 
hypothesis. What that hypothesis is will be discussed later. The 
book is written in a clear and simple style, in short sentences very 
unlike the usual German manner, in fact, in places almost telegraphic, 
and occasionally the meaning of a sentence is rendered somewhat 
obscure by the absence of a principal verb. 
The book begins with a discussion of the nature of the earth’s 
crust, its thickness and composition, and its morphological sub- 
divisions, emphasizing the contrast between the massive and 
permanent continental blocks and the folded regions, the latter 
originating as geosynclinals. For these last elements the word 
“ Orogen”’ 1s employed, a word difficult to translate neatly, but 
perhaps best expressed as orogenic zone. Much importance is 
rightly attached to the different facies of sedimentation and the 
close connexion between types of earth movement and the Atlantic 
and Pacific igneous rock-families of Harker is strongly insisted on. 
The writer commits himself to the somewhat unusual view that the 
Atlantic (alkaline) magma is the typical world-magma of the depths, 
and that the Pacific magma is a special variety due to differentiation 
by orogenic movements. This is in absolute contradiction to the 
trend of modern opinion, especially in America. 
The structures of continental masses and mountain chains are 
compared and contrasted, and the present plan of the surface is 
mainly attributed to Mesozoic geosynclinals. The account of the 
structure of the Alpine chains is specially clear, and brings out well 
the results of recent work in establishing the southward folding of the 
Eastern Alps and the Dinaric chains. The Alpine mountain system 
in general is interpreted as the boiling over of a geosynclinal between 
the jaws of a vice, as figured by Suess, but it is made clear that the 
