No. 390.) REVIEWS OF RECENT LITERATURE. 549 
our best farm lands. Following this description of down-cutting and 
up-building, he brings out the effect of changes in the earth’s crust 
by elevation and subsidence and by variations in climate, particularly 
through glacial action, and then having touched upon the principal 
points of hydrology he gives, as above noted, some of the character- 
istics of important streams, and, in conclusion, takes up the life his- 
tory of a river, showing the principal events from youth to old age. 
The conception is constantly kept before the reader that a river 
is a living thing working out its own life history, and that the appar- 
ently permanent features which we see are the temporary products 
of arestless and moving organism. ‘The converse is also enforced 
that for every delta, terrace, curve, rapid, or fall of the river there is 
a definite cause, which may be sought and explained according to 
general law, and that the apparent anomalies may be reconciled if 
the student will patiently look into the subject. 
The discussion of these natural laws, while necessarily somewhat 
abstruse, is rendered as interesting as possible by copious illustra- 
tions taken from well-known phenomena in the geography of North 
America. For example, as showing the importance of the glacial 
epoch upon the industrial development of New England, it is stated 
that manufactures were established there soon after the coming of 
Europeans, owing to the facilities offered by the numerous small 
water powers. These resulted from the disturbance produced in 
stream development by the débris left by the retreating ice sheet of 
the past geologic age. South of the glacial boundary, that is, south 
of Pennsylvania, water power is far less abundant and mostly within 
the inaccessible portions of the mountains. The development of 
manufacturing industries hence has been delayed and attention given 
more largely to agriculture, for which climatic and other conditions 
are more favorable. Thus a decided trend was early given to the 
New England character and manufacturing was so firmly established 
that although the water powers have relatively declined in importance, 
and steam has usurped their place, yet the glaciated regions of the 
United States still continue to lead in manufacturing. Here we 
have a direct relation between the effects of ancient changes in geog- 
raphy and modern growth of civilization. 
Another striking illustration of the effect of geologic changes upon 
industrial development is given in the case of the drowned river — 
the Hudson — whose valley submerged by subsidence of the earth’s 
crust has become a long narrow arm of the sea, where the tides rise 
and fall. During its early history the river cut its deep channel 
