548 THE AMERICAN NATURALIST. [VoL. XXXIII. 
GEOLOGY. 
Rivers of North America.!— A book with the comprehensive 
title Rivers of North America cannot fail to arouse interest among 
students of nature, especially when followed by the name of the 
, author, Professor Israel C. Russell. Curiosity is felt as to how a 
subject so vast as this can be concisely treated by any writer, par- 
ticularly by one who has obtained many of his conceptions at first 
hand through observation and study in the field. Of the many ways 
in which the rivers of North America might be discussed there occur 
to the mind two as especially distinct and important. The first is a 
geographic description of the position, length, volume, character of 
water, and other existing conditions; and the second might be an 
analysis from the geologic standpoint of the causes of these features 
or of the phenomena as noted along the course of each river. This 
latter form of treatment is that toward which Professor Russell has 
directed most of his investigations, and the book reflects largely the 
results of his field work. In fact his book might be classed as a 
primer of hydro-geology or hydrology, using this latter term as dis- 
tinct from hydro-geography (hydrography), or the description of 
bodies of water. The hydrographic or descriptive part of the sub- 
ject is not neglected, being included under the head of “ Charac- 
teristics of American Rivers,” but is subordinate to the thorough 
discussion of the why and wherefore of present conditions. 
Professor Russell begins by showing that the surface of the earth 
is a scene of continuous change, the higher portions being gradually 
worn away and modified by the running waters, which, gathering into 
streams, make for themselves valleys proportioned to the various 
forces at work. Beginning with rock decay and removal of the sur- 
face débris, he passes on to discuss the laws governing streams, the 
limitation of downward cutting to base level, the influence of the 
hardness of the rock in producing rapids and waterfalls, and makes 
note of the material carried by the streams in visible particles or in 
solution. Passing from the destructive or eroding action of the 
rivers, he takes up their constructive features and shows how the 
alluvial cones and deltas grade from one into the other, and brings 
out the origin of the stream terraces, developing the fact that these, 
from the industrial standpoint, are among the most important result- 
ants in the development of the country, since they furnish some of 
1 Russell, Israel C. Zhe Rivers of North America. xix + 327 pp. 17 pls» 
18 figs. New York, Putnams, 1808. 
