ntly illustrated with
well-executed figures of all the characteristic species that distinguish
the several periods, mostly drawn from American examples.

_Dynamical Geology_.--This particular branch of the subject is made
less prominent than usual in geological works, but it will not be found
lacking in any point.

The subject is presented in the following order:--

1. Life as an agent in protecting, destroying, and making rocks.

2. Cohesive Attraction.

3. The Atmosphere as a mechanical agent.

4. Water as a mechanical agent.

5. Heat as an agent in volcanic phenomena, igneous eruptions,
metamorphism, veins, etc.

6. Movements of the earth's crust, plication of strata, origin of
mountains, earthquakes, etc.

7. Chemistry of Rocks.

Under the first head, we have much interesting matter concerning peat
and coral formations, coral reefs and their origin, illustrated with
figures.

Under the head of Water as an Agent, some plates are given, new to the
general reader, of the remarkable _canons_ of the Colorado, which so
well illustrate the powerful agency of this element in wearing away
for itself deep channels in the strata. Under the same head is an
interesting essay upon Glaciers, with figures, one of which is a reduced
copy of a sketch in Agassiz's great work, representing the Glacier of
Zermatt, in the Monte-Rosa region.

Under the head of Heat as an Agent, we have, as might be expected,
interesting and valuable matter upon volcanic phenomena, and those of
metamorphism.

We have thus briefly passed in review the contents of the work, and
without criticism, too, for we would scarcely have a sentence in the
book altered or omitted. Yet we do not always concur in all the views
expressed or implied by the author. For instance, we consider the
evidence of the Jurassic age of the Ichnolitic strata of the sandstone
of the Connecticut River too strong to allow of their being any longer
classed among the Triassic. We certainly differ from him in much that is
said upon the subject of Man, as of one species. Yet we do not care to
dwell upon these points, especially the latter. Our author will not
expect to find all readers agreeing with him upon such mooted questions.

We do not think that we overestimate the value of this work, when
we express our belief that its publication will mark an era in our
geological progress. By this we do not mean to imply that its character
is such as to be of great service to tho