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 convulsive emergence of the pebbly banks out of the neval ocean, either at the deluge, or by some preceding strophe. There are mountains 10,000 feet high, in the s, formed of firmly conglomerated pebbles.

Another and most striking proof that the rocks have n elevated by some force acting beneath them, is exited by primitive mountains in various parts of the

-ld.

som are f every

sea a have

destru

Here we find granite in the centre, with stratified rocks, gneiss, mica-slate and clay-slate, leaning against its s, sometimes nearly in a vertical position. Now as se stratified rocks must have been deposited on a horital level, or nearly so, and surely not in the highly ined positions in which they are found, it is evident that r original positions must have been changed, and their inations caused by the same force which elevated the nitive mountains.

to ha

must a

Under the article "Classification of Rocks," this subis illustrated by a wood cut, to which the reader is reed.

forts

Ha

believ

rated

Concea

every

t thus appears sufficiently evident, that at least a great portion of the habitable earth was formed in strata er the sea; and that subsequently to its being consoled chiefly in the position and form of horizontal layit has been violently elevated above the water, by

lar la

would nothin

ome tremendous subterranean power. Hence the strata re found oblique, dislocated, and rent asunder in nearly very part of the world; and from this cause it is, that the a and land have exchanged places, and the mountains ave been elevated; but to the same cause, even to the estruction of that continuity and harmony which seems have existed in the form of the primitive globe, we ust attribute many of the greatest conveniences and comrts which the present earth affords.

Had no disturbing forces interposed, there is reason to lieve that the inferior strata, now in many places eleated into hills and mountains, would for ever have been oncealed from the knowledge of man; for was the earth erywhere covered with horizontal strata, lying in regur layers, one upon another, the same kind of formations ould everywhere exist; and of which we should know thing below the depth of actual excavations. Metallic ins, salt, and coal, would afford no indications of their istence at or near the surface. There would have been O mural precipices, or mountain declivities, or outOppings of strata, by which the geologist, or practical ner, would be enabled to judge of the interior. Nor uld there have been any spring of water issuing from è surface of the earth, for it is the inclination of the ata which directs the water to the surface, and its unenness which allows it to break forth in the form of ings. In plain level districts, no water rises to the face. In these, and many other examples which might noticed, we cannot but see the traces of benevolence 1 design, even in the "wreck of matter," which this th everywhere displays; and which, at every step, ces us to acknowledge, not only the Power, but the isdom and Kindness of the Almighty Builder of this · habitation.

With respect to the agent which has thus thrown mounis and continents from the depths of the oceans, and dislocated the framework of the globe, we can conve of none except volcanic, of sufficient power to proe such effects. It is true that no continents or extenè mountains, have been elevated from the sea, since historical era, but we have a sufficient number of mples of the effects of this power, even during the sent age, to show that the established order of nature

e elevation of land to the extent of a hundred miles the coast of Chili; the rising of the Sabrina island out the ocean; and of the Aleutian islands on the coast of mtschatka, out of the same; the changes made by the ce of volcanoes in the neighborhood of Naples, and the ects of the earthquakes of Calabria and Lisbon, (all of ich we have described in the preceding pages,) afford logies by which it is not unreasonable to conclude, t it was the same kind of force which broke in pieces crust of the primeval globe, and raised the habitable th from the ocean's bed.

At what period of the creation these great changes took ce, we must remain in ignorance, but it is improbable t they were all effected at the same time. On the conry, the appearance of the strata seem to indicate a sucsion of revolutions at different, and perhaps remote iods from each other. These revolutions appear to e been before the creation of man and animals, and bably by such means did the Wisdom and Benevolence the Creator prepare a place for their reception and fort.

CLASSIFICATION OF ROCKS.

In

The most simple division of rocks is into Primitive or mary, and Secondary. The first consisting of those ich are supposed to have been originally formed, such granite and its associates, and the second such as were med by the disintegration, or destruction of these.

early state of geological knowledge this was the reved classification. In the first kind no organic reins, as plants or shells, are found, and hence they re supposed to have been formed before the creation of anized beings. In the secondary, these remains exist etimes in great abundance. To this classification the ebrated Werner added the Transition class, which cons of the larger fragments of the primitive, and which ntermediate between this, and that usually called sedary.

The

globe. same t One of is a co

At present, there are a considerable variety of classifions, some of which are too prolix and complicated for opular work, while others are forbidding on account of technical language in which they are written.

erals a

felspar

a glass

broken.

Felspar

broken, with sm

but more

thin flex

Separabl name of economic for stores

strata, or

erals diff

ferent ro

size, some

a foot in

larger the

The ot

slate, Pr

which son

This w

Perhaps the best which we can adopt, as embracing all e others, without their minute subdivisions, is the followg:

1. PRIMARY.

2. TRANSITION, OR INTERMEDIATE.

3. SECONDARY, comprising,

a. THE LOWER SECONDARY SERIES.
b. THE UPPER SECONDARY SERIES.

4. TERTIARY.

5. BASALTIC, AND VOLCANIC ROCKS.
6. DILUVIAL, AND ALLUVIAL DEPOSITES.

PRIMARY ROCKS.

These compose the great frame, or groundwork of the obe. They form the most lofty mountains, and at the me time extend downward below all other formations. e of the principal rocks of this class is granite. This compound rock, being composed of three distinct minls aggregated into a solid form. These are quartz, spar, and mica. Quartz has commonly a white color, glassy lustre, and does not divide into layers when ken. It often forms a large proportion of the granite. spar has a yellowish, or milk white color, and when ken, often divides into layers of considerable thickness, h smooth shining faces. Mica is also sometimes white, more commonly of a dark green color. It consists of flexible leaves, adhering slightly together, and easily arable by the nail. This is well known under the e of isinglass, and when in large plates is used for nomical purposes, as the dead-lights for ships, windows, stoves and lanthorns, &c. Granite never consists of ta, or layers, like gneiss and mica-slate. These mins differ greatly in their respective proportions in difnt rocks. They also differ widely with respect to some granites being composed of crystals, or grains, ot in diameter; while in others the grains are no er than those of sand.

he other Primitive rocks, are Gneiss, Mica-slate, ClayPrimitive Limestone, Porphyry, and Sienite; to ch some add several others.

re, and never contain the fragments of other rocks, or ■y organized substance.

Gneiss, and mica-slate are composed of the same marials as granite, but differently arranged. They are also enerally composed of much smaller grains than granite. gneiss the felspar and quartz are aggregated closely gether, forming strata, or layers, between which interne scales of mica. Hence gneiss is a stratified rock, id when broken at right angles with the strata, presents striped appearance, the quartz and felspar being nearly hite, while the mica is deep green or black.

Mica-slate is chiefly composed of quartz and mica, the Ispar being in only small quantities, or in some instances early absent. The quartz is commonly in fine grains, d the mica usually predominates, or at least is much e most apparent. Some specimens of this rock appear be almost entirely composed of small scales of mica, osely adhering together.

Mica-slate differs from gneiss in containing a less proortion of felspar, and in being more distinctly stratified, slaty in its structure. It is readily divided into layers, tables, by means of wedges, and is extensively employ1 for economical purposes, especially for flagging the side

alks of cities.

Gneiss is intermediate between granite and mica-slate its structure, and is often found interposed between these ocks, lying over the former, and under the latter. Indeed ese rocks pass by insensible degrees into each other, e granite gradually becoming stratified runs into gneiss, hile the gneiss becoming fissile forms mica-slate. These ree are called granitic rocks, and form together a great roportion of the solid crust of our globe.

The adjoining wood cut from Daubuisson, represents e most common relative positions of granite, gneiss and ica-slate, as they occur on the earth.

The centre or middle mass, 1, projecting high above e side strata, is granitie. The flanking planes, 22, are neiss, appearing as though they had been elevated to eir present situation by the tremendous force which fted up the granite. The mica-slate, 3, 3, is seen restng against the gneiss. The two latter rocks have the ppearance of once having been in a horizontal position,