This is owing, partly, to the hard names and scientific language in which geologists have clothed their science, and partly to ignorance of the beauty and attractive nature of the study; we dread the long, abstruse-sounding titles of Ichthyosaurus and Plesiosaurus, and are repelled by the dry disquisitions on mineralogy into which professors of the science are apt to stray. The truth is, however, that geology properly is divided into two distinct branches; one of these consists of the less attractive, though equally useful, investigation of the chemical constituents of the strata, and the classification of the fossil flora and fauna which belong to the various formations; this, which may be styled geology proper, is the department which belongs almost exclusively to men of science, and, inasmuch as it involves the necessity of acquaintance with the sister sciences of chemistry, mineralogy, zoology, and botany, is least adapted to the understanding of the uninitiated. The other branch, which may be called the history of geology, presents none of these difficulties; it is as easy of comprehension, and as suitable to the popular mind, as any other historical account; while it presents a variety of interest, and a revolution of events, before which the puny annals of modern history sink into insignificance. Such of our readers as are unacquainted with the science, will probably be inclined to doubt the possibility of our being aware of events which took place ages before Adam was created; here, however, nature herself steps in, and becoming her own historian, writes "in the living rock" the chronicles of past ages, and so accurately and circumstantially, that we can say positively, "Here existed the sea at such a period, and here the tide ebbed and flowed for centuries;" nay, she shows us the footmarks of extinct animals, and tells us the size, nature, habits, and food of creatures which have for unnumbered ages been buried in the grave of time. She informs us that here the ocean was calm, and that there a river flowed into it; here forests grew and flourished, and there volcanoes vomited forth lava, while mighty earthquakes heaved up mountains with convulsive throes. Such are the events that mark the world's history, and we now purpose giving a short sketch of the various eras in its existence.