Review of Recent Geological Literature. 261 
Earth Sculpture, or the Origin of Land Forms. By James Geikie. 
New York, G. P. Putnam's Sons; London, John Murray, 1898. Pp. 397, 
octavo, 89 illustrations, 2 plates. S2.00. 
Rivers of North A7nerica : A reading lesson for students of geogra- 
phy and geology. Dy Israel C. Russell. New York, G. P. Putnam's 
Sons; London, John Murray, 1898. Pp. 327, octavo, 23 illustrations in 
the text and 17 plates. S2.00. 
In these two works the new science of geomorphy finds its first 
comprehensive English expression in popular form; for, while the gen- 
eral and broad title of the former necessarily embraces all the prin- 
ciples and groups all the facts of earth sculpture, the special topic dis- 
cussed by Prof. Russell, the rivers of North America, cannot be full}' 
treated, as he himself states, without involving much more than that 
>ubject alone implies: and he is drawn easily into a brief presentation 
of some of the same phenomena which Dr. Geikie treats of at length, 
though confining himself to the region of North America. 
Dr. Geikie's comprehensive subject leads to a discussion of all the 
agents and methods of denudation, and of all the accidental variations 
and as well as the usual topographic forms seen in the existing land 
surface of the earth, due to diflferences in the pose and in the hardness 
of the rocks of the crust when acted on by atmospheric forces. The 
author traces the history of a mountain, or chain of mountains, involv- 
ing folding and faulting of all kinds, modified by rocks of differing 
hardness, through its period of ruggedness to its middle life and old 
age, the result being a base -level or peneplain. 
The history of the peneplain is then followed further, through sub- 
sequent uplift and faulting, through long denudation and channelling 
by streams, through a second mountainous period, illustrated by the 
southern uplands and the northern highlands of Scotland, these hills 
being simply the results of secondary dissection of ancient plateaux. 
By continuance of this denudation the author shows that the whole 
may be again reduced to a second peneplain. "It is seldom, however, 
that a cj'cle of erosion is allowed to pass through all its stages. The 
study of many ancient plateaux has shown that the base-level is not in- 
frequently disturbed, sometimes by elevation, at other times by depres- 
sion." 
Follow-ing this discussion of the grand round of a cycle of erosion 
are various chapters devoted to special topographic features and to 
their causes, such as hills due to faults, to igueous action, and to great- 
er firmness and endurance of certain rocks. 
The author considers glacier ice as an effective agent of erosion. 
"It not only abrades, rubs, smooths, and polishes, but also crushes, 
folds, disrupts, and displaces rock-masses, the amount of diturbancc 
Ining in proportion to the reisting power of the rocks and the pressure 
■exerted by the ice." 
The work closes with a full presentation of eolian action, with illus- 
trations, underground waters, basins, and a cLissification of land forms. 
