PETROLOGICAL ABSTRACTS AND REVIEWS 83 
carbon dioxide, and oxygen, and by the decrease in the average specific 
gravity of the minerals formed. 
The authors do not lay much stress upon the zones of katamorphism 
and anamorphism, emphasized by Van Hise, for the zone through which 
katamorphism extends, for example, has very indefinite limits, both 
katamorphic and anamorphic changes being possible simultaneously 
at moderate depths in different kinds of rocks, or in the same kind of 
rock under different conditions. 
The weathering of granite is used as a type of katamorphism. The 
rock used as an example is a Georgia ‘‘granite,’”’ and although so called 
by Watson it is not a granite, neither mineralogically as shown by the 
table on page 6, nor chemically. It is a quartz-monzonite verging toward 
a granodiorite, and not greatly different from Lindgren’s type granodi- 
orite. So far as the results of the alteration go, however, it is immaterial 
what the rock is called, and the term granite may be used in the “‘com- 
mercial sense.” In this chapter 16 pairs of analyses, representing the 
weathering of acid igneous rocks, are shown by “‘straight-line diagrams,”’ 
which well illustrate the changes which have taken place. 
The second chapter treats of the katamorphism of basic igneous 
rocks, 17 pairs of analyses being given in the second plate. 
In the third chapter the production of bauxite and laterite by the 
extreme weathering of rocks is discussed, the authors maintaining that 
bauxite and the associated clays are the products of the surface weather- 
ing of syenite by normal processes of rock-decomposition, and that they 
are not chemical sediments. They believe that kaolin is an intermediate 
stage and that they can trace the gradation from syenite through kaolin- 
ized syenite to bauxite wherever fresh cross-sections appear. There 
is a good discussion of the formation of laterite and associated iron ores 
in Cuba. 
A comparison of the two plates showing the hydrothermal kata- 
morphism of 29 igneous rocks with the plates showing normal weathering 
gives a clear conception of the differences between these two types of 
alteration. 
So far the book has dealt with the katamorphic destruction of igneous 
rocks and with the nature and distribution of the end-products. The 
katamorphism of sediments, cres, etc., is now taken up in several 
chapters, and is followed by sc pages on the redistribution of the con- 
stituents of the average crystalline and igneous rocks during kata- 
morphism. Here the redistribution of the constituents is considered in 
terms of sediments—first in weight proportions of shales, sandstones, and 
