Fig. 14. that strata of rounded pebbles assuredly agglutinated in a horizontal position, are now found standing in upright walls. Thus the famous pudding-stones of Valorsine in Savoy, are a kind of graywacke schist, containing rounded fragments of gneiss, and mica-slate, six or seven inches in diameter. That stones previously rounded by attrition, should build themselves up into a nearly perpendicular wall, as seen at Fig. 14, and stand steadily thus, till fine particles of hydraulic cement should have time to envelop and fix them in their places, is an absurd and impossible supposition. It is therefore demonstrable that these pudding-stone strata were formed in horizontal, or slightly inclined beds, and erected after their accretion. Such effects would be produced, in the convulsive emergence of the pebbly banks out of the primeval ocean, either at the deluge, or by some preceding catastrophe. There are mountains 10,000 feet high, in the Alps, formed of firmly conglomerated pebbles. Another and most striking proof that the rocks have been elevated by some force acting beneath them, is exhibited by primitive mountains in various parts of the world. Here we find granite in the centre, with stratified rocks, as gneiss, mica-slate and clay-slate, leaning against its sides, sometimes nearly in a vertical position. Now as these stratified rocks must have been deposited on a horizontal level, or nearly so, and surely not in the highly inclined positions in which they are found, it is evident that their original positions must have been changed, and their inclinations caused by the same force which elevated the primitive mountains. Under the article "Classification of Rocks," this subject is illustrated by a wood cut, to which the reader is referred. It thus appears sufficiently evident, that at least a great proportion of the habitable earth was formed in strata under the sea; and that subsequently to its being consolidated chiefly in the position and form of horizontal layers, it has been violently elevated above the water, by Hence the strata some tremendous subterranean power. are found oblique, dislocated, and rent asunder in nearly every part of the world; and from this cause it is, that the sea and land have exchanged places, and the mountains have been elevated; but to the same cause, even to the destruction of that continuity and harmony which seems to have existed in the form of the primitive globe, we must attribute many of the greatest conveniences and comforts which the present earth affords. Had no disturbing forces interposed, there is reason to believe that the inferior strata, now in many places elevated into hills and mountains, would for ever have been concealed from the knowledge of man; for was the earth everywhere covered with horizontal strata, lying in regular layers, one upon another, the same kind of formations would everywhere exist; and of which we should know nothing below the depth of actual excavations. Metallic veins, salt, and coal, would afford no indications of their existence at or near the surface. There would have been no mural precipices, or mountain declivities, or outcroppings of strata, by which the geologist, or practical miner, would be enabled to judge of the interior. Nor would there have been any spring of water issuing from the surface of the earth, for it is the inclination of the strata which directs the water to the surface, and its unevenness which allows it to break forth in the form of springs. In plain level districts, no water rises to the surface. In these, and many other examples which might be noticed, we cannot but see the traces of benevolence and design, even in the "wreck of matter," which this earth everywhere displays; and which, at every step, forces us to acknowledge, not only the Power, but the Wisdom and Kindness of the Almighty Builder of this our habitation. With respect to the agent which has thus thrown mountains and continents from the depths of the oceans, and has dislocated the framework of the globe, we can conceive of none except volcanic, of sufficient power to produce such effects. It is true that no continents or extensive mountains, have been elevated from the sea, since the historical era, but we have a sufficient number of examples of the effects of this power, even during the present age, to show that the established order of nature would not be changed by the elevation of a continent, The elevation of land to the extent of a hundred miles on the coast of Chili; the rising of the Sabrina island out of the ocean; and of the Aleutian islands on the coast of Kamtschatka, out of the same; the changes made by the force of volcanoes in the neighborhood of Naples, and the effects of the earthquakes of Calabria and Lisbon, (all of which we have described in the preceding pages,) afford analogies by which it is not unreasonable to conclude, that it was the same kind of force which broke in pieces the crust of the primeval globe, and raised the habitable earth from the ocean's bed. At what period of the creation these great changes took place, we must remain in ignorance, but it is improbable that they were all effected at the same time. On the contrary, the appearance of the strata seem to indicate a succession of revolutions at different, and perhaps remote periods from each other. These revolutions appear to have been before the creation of man and animals, and probably by such means did the Wisdom and Benevolence of the Creator prepare a place for their reception and comfort. CLASSIFICATION OF ROCKS. The most simple division of rocks is into Primitive or Primary, and Secondary. The first consisting of those which are supposed to have been originally formed, such as granite and its associates, and the second such as were formed by the disintegration, or destruction of these. In the early state of geological knowledge this was the received classification. In the first kind no organic remains, as plants or shells, are found, and hence they were supposed to have been formed before the creation of organized beings. In the secondary, these remains exist sometimes in great abundance. To this classification the celebrated Werner added the Transition class, which con. sists of the larger fragments of the primitive, and which is intermediate between this, and that usually called secondary. At present, there are a considerable variety of classifications, some of which are too prolix and complicated for a popular work, while others are forbidding on account of the technical language in which they are written. Perhaps the best which we can adopt, as embracing all the others, without their minute subdivisions, is the following: 1. PRIMARY. 2. TRANSITION, OR INTERMEDIATÉ. 3. SECONDARY, comprising, a. THE LOWER SECONDARY SERIES. b. THE UPPER SECONDARY SERIES. 4. TERTIARY. 5. BASALTIC, AND VOLCANIC ROCKS. PRIMARY ROCKS. These compose the great frame, or groundwork of the globe. They form the most lofty mountains, and at the same time extend downward below all other formations. One of the principal rocks of this class is granite. This is a compound rock, being composed of three distinct minerals aggregated into a solid form. These are quartz, felspar, and mica. Quartz has commonly a white color, a glassy lustre, and does not divide into layers when broken. It often forms a large proportion of the granite. Felspar has a yellowish, or milk white color, and when broken, often divides into layers of considerable thickness, with smooth shining faces. Mica is also sometimes white, but more commonly of a dark green color. It consists of thin flexible leaves, adhering slightly together, and easily separable by the nail. This is well known under the name of isinglass, and when in large plates is used for economical purposes, as the dead-lights for ships, windows, for stoves and lanthorns, &c. Granite never consists of strata, or layers, like gneiss and mica-slate. These minerals differ greatly in their respective proportions in different rocks. They also differ widely with respect to size, some granites being composed of crystals, or grains, a foot in diameter; while in others the grains are no larger than those of sand. The other Primitive rocks, are Gneiss, Mica-slate, Clayslate, Primitive Limestone, Porphyry, and Sienite; to which some add several others. This whole class is generally crystalline in its struc ture, and never contain the fragments of other rocks, or any organized substance. Gneiss, and mica-slate are composed of the same materials as granite, but differently arranged. They are also generally composed of much smaller grains than granite. In gneiss the felspar and quartz are aggregated closely together, forming strata, or layers, between which intervene scales of mica. Hence gneiss is a stratified rock, and when broken at right angles with the strata, presents a striped appearance, the quartz and felspar being nearly white, while the mica is deep green or black. Mica-slate is chiefly composed of quartz and mica, the felspar being in only small quantities, or in some instances. nearly absent. The quartz is commonly in fine grains, and the mica usually predominates, or at least is much the most apparent. Some specimens of this rock appear to be almost entirely composed of small scales of mica, closely adhering together. Mica-slate differs from gneiss in containing a less proportion of felspar, and in being more distinctly stratified, or slaty in its structure. It is readily divided into layers, or tables, by means of wedges, and is extensively employed for economical purposes, especially for flagging the side walks of cities. Gneiss is intermediate between granite and mica-slate in its structure, and is often found interposed between these rocks, lying over the former, and under the latter. Indeed these rocks pass by insensible degrees into each other, the granite gradually becoming stratified runs into gneiss, while the gneiss becoming fissile forms mica-slate. These three are called granitic rocks, and form together a great proportion of the solid crust of our globe. The adjoining wood cut from Daubuisson, represents the most common relative positions of granite, gneiss and mica-slate, as they occur on the earth. The centre or middle mass, 1, projecting high above the side strata, is granitie. The flanking planes, 2 2, are gneiss, appearing as though they had been elevated to their present situation by the tremendous force which lifted up the granite. The mica-slate, 3, 3, is seen resting against the gneiss. The two latter rocks have the appearance of once having been in a horizontal position, |