Rez'iew of Recent Geological Literature. 389 
oxidation, carbonation, and hydration. The alterations of the zone of 
anamorphism occur with absorption of heat and diminution of volume, 
the chief reactions being deoxidation, silication with decarbonation, and 
dehydration. Thus the alterations in the two oppose each other. The 
zone of katamorphism is divided into two belts, that above the level of 
ground water, tlie belt of weathering, and that below the level of ground 
■water, called the belt of cementation. While the physical-chemical prin- 
ciples of alteration are the same in each of these belts, the geological 
processes are very different. The belt of weathering is characterized by 
solution, decrease of volume, and softening, resulting in physical de- 
generation. The belt of cementation is characterized by deposition, in- 
crease of volume, and induration, resulting in physical coherence. 
Chapter V treats of minerals. Each of the rock-making minerals is 
discussed with reference to its occurrence and alterations. The altera- 
tions are considered from the physical-chemical point of view. An at- 
tempt is made to write chemical equations which represent the trans- 
formations, and to calculate the volume relations resulting. It is found 
that a great number of rock-making minerals undergo two classes of 
changes, one of which is characteristic of the zone of katamorphism. and 
the other of which is characteristic of the zone of anamorphism. Per- 
haps the most important generalization of this chapter is as to the re- 
versibility of reactions in the two opposing zones. This generalization 
is as follows : The equations which represent the reactions in the zone 
of katamorphism are reversible in the zone of anamorphism ; and so far 
as there is expansion of volume and liberation of heat in the upper zone, 
just so far is there condensation of volume and absorption of heat in 
the lower zone. 
Chapter VI considers the belt of weathering. The belt of weathering 
being the one which is most readily observed, has been treated by many 
authors. The chapter in this volume on weathering differs from pre- 
vious discussions in that the phenomena are not considered mainly from 
the descriptive point of view, the emphasis being given to the classifica- 
tion of the phenomena and their explanation under physical and chem- 
ical principles. Also an important feature of this chapter is the consid- 
eration of the phenomena of the belt of weathering in relation to the 
alterations of the other belts of nietamorphism. 
Chapter VII treats of the belt of cementation. This belt is defined 
as extending from the belt of weathering to the bottom of the zone of 
fracture. The geological results are found to contrast very markedly 
from those of the belt of weathering. In the latter belt solution is' the 
rule; openings are enlarged: the rocks degenerate. In the belt of ce 
mentation, upon the other hand, the processes of nietamorphism con- 
tinuously deposit material, the openings are closed, and thus the rocks 
are consolidated. ELach of the cementing substances is considered, and 
an explanation is offered as to why cementation rather than solution 
is a general process in this belt. 
Chapter VIII treats of the zone of anamorphism. This i.s the zone 
in which rock flow occurs. Full explanations of the meaning of rock 
