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OF

GEOLOGY:

INTENDED AS A POPULAR TREATISE ON THE

MOST INTERESTING PARTS OF THE SCIENCE.

TOGETHER WITH AN EXAMINATION OF THE QUESTION,

WHETHER THE DAYS OF CREATION WERE
INDEFINITE PERIODS.

DESIGNED FOR THE USE OF SCHOOLS AND GENERAL READERS.

[graphic]

BY J. L. COMSTOCK, M. D.
Author of an Introduction to Mineralogy, Elements of Chemistry, A System of
Natural Philosophy, and Introduction to Botany.

THIRD EDITION.

NEW YORK.

ROBINSON, PRATT, & CO.

63 WALL STREET.

1838.

8532 .263 11938

ENTERED,

According to Act of Congress, in the year 1834, by

J. L. COMSTOCK, M. D.

In the Clerk's Office of the District Court of Connecticut.

STEREOTYPED BY F. F. RIPLEY,

NEW YORK.

65-32

PREFACE.

GEOLOGY is peculiarly adapted to impress the mind of the student with ideas of the wisdom and power of the Creator, and to lead him to the acknowledgment of a Great First Cause. In addition to this, it is applicable to various, and highly important practical purposes. Millions have been expended in boring for salt, in mining for coal, and in searching for metallic veins, when even a slight knowledge of the nature and geological positions of rocks, as indicated by external appearances, would have shown that such explorations would be fruitless.

In the sinking of wells, in excavations for canals, roads, and buildings, and for a great variety of other purposes connected with both civil and military engineering, a knowledge of geology is often of the highest importance to the contractor, and not less so to the contracting party.

Is it not time, then, that we should begin the study of the earth on which we live, and from which, in common with all terrene animals, we derive our subsistence? And can it be doubted, that the knowledge to be derived from this source, is fully as important to the youth of this great and unexplored country, as that pertaining to the names and sources of rivers, the extent and situation of seas, and the boundaries of nations, states, and towns, which our scholars spend so much time in committing to memory?

To supply the deficiency of books on this subject, adapted to general readers and to our higher schools, is the object of this work. Possibly the clergy of our country, who have no time to read extensive geological works, and thus to collect the scattered facts which show the coincidence and connexion between the Scriptures and geology, may find this little volume an acceptable assistance. At the present day, when infidelity looks almost exclusively among the higher departments of science for aid, ought not theologians, at least, to understand the ground of such hopes, in order to make good their own defence? An experienced soldier always looks well to the strength of his outposts.

With respect to the matter of the following treatise, it is perhaps sufficient to say, that almost every recent systematic geological writer in the English language, as well as many periodical publications, have been consulted. The plan has been to treat of the most interesting and important parts of the science, as a whole, and hence particular notices on American geology have been omitted, only in conformity to this design.

To those acquainted with the present state of geology, it hardly need be said, that to have prepared a volume which should embrace and unite the opinions of even the most recent and respectable authors on many subjects contained within its outlines, would have

been impossible: and to those who are not acquainted with this science, it may be proper to state, that from the very nature of many of its subjects, there must always exist a variety of theories to account for the same facts, until more is known concerning them. This arises from the circumstance, that the causes of many phenomena which the earth exhibits, have long since ceased, and therefore these causes must remain matters of conjecture. Thus coal is found in the earth in great abundance, but none is formed at the present day, and therefore the causes which have produced this substance, or at least the circumstances under which it was formed, remain a subject of theory.

In other instances, the causes still exist, but their effects only are apparent, as in the case of volcanoes and earthquakes.

In these instances, the leading facts are admitted by all, but men have chosen to account for them in different ways, and thus different theories have been proposed, to solve the same phenomena.

Again, in many things connected with the natural history of the earth, the chief circumstance in question may rest on a variety of collateral facts, of the bearing of which geologists differ in opinion. Thus fossil plants, belonging to orders which at present only grow in tropical climates, and the remains of animals whose species are now found only in the hottest regions of the earth, occur in many parts of Europe, and even in frozen Siberia. Hence some have supposed that the climate of Europe has changed since the deposition of these remains, and that the plants grew, and the animals lived, where their relics are now found: while others, reasoning from what they consider conflicting facts, maintain that no change of climate has taken place, and that the main circumstance may be accounted for, by supposing that these remains were transported from hot climates.

At the present day, geological writers profess to maintain their theories only by facts, and fair deductions from them, and thus investigations are constantly going on, and new facts are perpetually accumulating, so that ultiinately it may be expected that this science will consist of deductions from truths which are generally admitted. But in its progress towards such a state, hypothetical reasonings, under the restrictions which the present advanced state of the sciences impose, are not to be deprecated, since this is often almost the only means by which men are stimulated to that thorough investigation of facts and phenomena, which characterizes the practical geologists of the present day.

It must not, however, be understood, that geology consists chiefly of the conflicting opinions of different authorities. On the contrary, though of so recent an origin, it already embraces numerous series of highly interesting, curious, and instructive facts, many of which seem destined to be of great importance to mankind; while others are calculated to excite profound considerations.

An examination of the earth shows that its crust has undergone great, and sometimes repeated mutations. The strata which once corresponded, are now completely dislocated, one portion being thrown up, broken, and distorted, while the other is depressed, and equally mutilated; the whole indicating the effects of an enormous force acting from beneath, and at an unknown depth.

Every part of the earth, except the most recent deposites, present similar phenomena, more or less striking, and in this manner the original disposition and direction of all ancient stratified rocks

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