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To this we may add, that the very same heat, transforming all the waters of the earth into vapour and gas, would extract all the fluids from animal and vegetable bodies, and expand them into the same element, and so leave the world one vast desert, utterly barren, waste, and lifeless.

Now, let us assume all to have taken place that these considerations involve, and imagine ourselves at the same time fixed on some starry pinnacle, listening to the voice of the great Elohim as it breaks from the unapproachable cloud of glory that surrounds His throne, "Let there be light,” and that mandate calls worlds into form and beauty. As we look, adore, and wonder, we hear that first great host of choristers, "the morning stars" that "sang together," and "all the sons of God" who "shouted for joy," as they witnessed this terrestrial creation struggling in the birththroes of a new existence.

It is sufficiently clear that an extended vapoury mass of matter, if pervaded by the powerful agency of gravitation, might condense into a sphere, like the planet on which we live. Science cannot demonstrate that this great globe once existed in a gaseous state; "that, by the gases entering into combination, a glowing and fused mass whirled round in space; and that this was the first 'genesis' by which our world was made visible and palpable." Yet there is evidence leading to the conclusion, that the surface, at least, was once in a state of fusion in consequence of great and universal heat. The phrase, "crust of the earth," seems to imply that such was the case. And this is the general opinion of geologists. Various natural phenomena show that there are at the present time vast subterranean regions of fire perpetually burning, and ready at any moment to burst out and spread wide consternation, ruin, and death, when and where these calamities are but little expected. In the existence of active volcanoes, (two hundred of which are enumerated as found in different parts of the earth,) occasionally throwing up flames, and pouring out liquid fire which spreads in streams and lakes of many miles in extent, we have information of this terrible element confined within the crust-formed surface. The shock of the earthquake, so often attendant on the eruption of the volcano, points to the same agency. The increase of heat, from the surface downward, in mines, wells, and wherever the temperature can be ascertained at any considerable depth, adds the strongest evidence: being, according to numerous and very careful observations, about one degree Fahrenheit for every fifteen yards of descent. It has been thought probable that this increase is in geometrical proportion. Taking these statements as correct, we may mark the heat as follows:- Water will boil at the depth of two thousand four hundred and thirty yards; lead will melt at the depth of eight thousand four hundred yards; there will be red heat at the depth of seven miles; gold will melt at twenty-one miles; cast iron, at seventy-four miles; soft iron, at ninety-seven miles; and at the depth of one hundred miles there will be a heat equal to the greatest ever yet attained by artificial means-a temperature capable of fusing platinum, porcelain, &c. If this scale of temperature be adopted, the earth is fluid at

the depth of one hundred miles from the surface.* Thermal springs, giving out streams of heated water from the interior of the earth, bear the same testimony. And the rocks themselves bear indelible traces of these fiery influences, not to be mistaken. Hence geologists conclude that the earth's crust was once a glowing sea of fire, if the globe itself were not one mass of gaseous vapour, whirling in its annual orbit round the sun; and that the hardened surface has been produced by cooling, but since modified by other agencies. Such are the conclusions, on this curious and interesting subject, to which careful and long-continued observations appear to conduct us.

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But it is with the rocky materials of the crust-like envelope, as they now present themselves, that geology has more especially to do.-By "the crust of the earth we mean the various classes of rocks composing the surface beneath our feet. These are exposed to observation, chiefly, in wells, pits, mines, scars or cliffs, mountain sides and summits, and especially in the upturned edges of strata at various points in most countries. Observations are made on these various rocks, to the depth of several miles; and their arrangement, character, contents, thicknesses, &c., have been ascertained. It is usual to divide them into two great classes,-igneous and aqueous; or those formed by fire, and those formed by water; which together constitute the whole mass, with the exception of a small but very interesting portion formed by vital agencies.

The different sorts of granite, basalt, and lava, known to geologists, comprise nearly the whole of the igneous class of rocks. The main agents in producing these varieties are, it is believed, the pressure (at varying degrees of intensity) under which they have been cooled, and the different circumstances of exposure to air or water during that process.

These rocks bear very decided characteristics of their origin. They appear, both internally and externally, to have been formed out of a molten, fluid mass. They always exhibit the glassy or crystalline in their texture. They take no particular form or shape, except that given to them by the place where they are cooled down. They are often ejected, in their molten state, into large cavernous openings or fissures, formed by the breaking and upheaving of the superincumbent masses through which they are hurled from the deep-seated furnace below; or, at other times, they are spread out on the surface above, in the form of lava, such as may be seen rolling down the sides of volcanoes in a living fiery stream, or lying in solid sheets around their base. None of the rocks of this class are strati

These observations and figures are extracted from "Things not generally known." We have a statement to the same effect, (copied from the "Record," of May 25th, 1857,) as follows:-" By experiments made during last year by Professor Smyth, at Edinburgh, with a series of earth-thermometers, imbedded in earth at varying depths, it was proved that there was a gradually increasing heat of one degree Fahrenheit for every forty feet of depth; so that at less than one and a half miles water would boil, and at less than one hundred miles deep all things must be in a state of fusion."

fied, and none contain organic remains. If they ever did contain such remains, the traces have been obliterated by the influence of heat.

Granite, the most crystalline, compact, abundant, and interesting of this class, often forms the tops of lofty mountains, as the Alps, Pyrenees, Andes, and others; to which it ascends from unmeasured depths below, where it underlies all the other varieties, and forms their base, spreading out and enveloping the whole globe, while resting on the hidden fires beneath. A mass of this sort-that is, of fire-formed rocks-may be, at a great depth, granite; higher up, basalt; and at the top, lava; according to the circumstances in which the refrigerating process has been carried on. These rocks are of all ages, but are most abundant at an early period. The granites are, as a general rule, the oldest; and the lavas the youngest, or most recently formed.

The aqueous rocks are, on various accounts, much more interesting than the former. Unlike the igneous class, which are formed mainly by forces acting from below, these are formed by influences acting on the surface, the chief of which is water. But, as we shall see, there are other agents, which, though less conspicuous, are nevertheless continually lending their aid for the same purpose.

The material elements constituting this great class of rocks are mud and clay, sand and gravel. They are chiefly hard and compact, like grit or limestone. But they may be soft, like loose sand or clay and still, in geological phrase, they are all named rocks, unless of very small amount, and at the surface. If a small stone be picked up and examined, it will generally appear to be formed of what was once clay or sand; and this is, in reality, the case. If it contain small pebbles not angular, but rounded, as if they had been long rolled and worn in water, it just reveals to us the manner of its formation. Such is the way in which the aqueous rocks are formed. The materials of which they are composed are precisely such as are every day borne down from plains, hills, and mountain-sides, by streams and rivers, into lakes or seas,-chiefly into the latter; where they fall to the bottom, compose extensive deposits, and, in length of time, harden into solid rocks, such as supply material for building and other important uses. They spread out to a greater or less extent, according to the character of the materials, and the size or transporting power of the river which conveys them from the land to the lake or sea. Such rivers as the Mississippi, Amazon, and Ganges form deposits hundreds of miles in extent. Rocks thus formed are said to be stratified; that is, spread out in successive layers upon each other. They are not crystalline, like the igneous, unless they have been baked or exposed to great heat, as the earlier formations appear to have been, by being exposed to some of that force which produced the igneous class. They are of all colours, and of various thicknesses, from less than a quarter of an inch to several hundreds of feet; and are slaty, shaly, or massive in texture.

Perhaps their most important characteristic is, that they lie one upon another in a regular and well-defined order of succession, from which they

never depart. In consequence of this order of succession, their relative ages can be determined, and the situation of any individual of the series easily known, wherever found. And, as they contain the entombed remains of various families of animals and plants which lived at the different periods of their formation, they constitute the natural archives of the world. They record, also, a series of events the most remarkable for magnitude, antiquity, long continuance, and variety.

The strata or rocks belonging to this class are never found all together in any one place; but as many as are anywhere found together are always in their proper order in the series. It may be at a considerable distance from any locality where a group is found, that the next set above or below occurs. Some may be absent altogether, but none will be out of their due arrangement.

It is in the earlier portions of the stratified rocks, as a general rule, that the metallic veins are found; the contents of which, as all are aware, have served high and valuable purposes in civilized communities, while they have employed and enriched a multitude of individuals.

One class of rocks, to which allusion has been made, may be here again mentioned; those, namely, which are formed by vital agencies. Perhaps the most interesting of these are coral-reefs. These, as it is well known, are formed by the insect which bears the same name. They belong to the warmer regions of the globe. Those existing at the present day in the Southern Ocean are of great extent. On the east coast of Australia, a coral-reef stretches three hundred and fifty miles in length. In the Pacific, between the Duff and Disappointment groups of islands, there are coral-reefs extending five hundred miles, over which the natives can pass from one island to another. Between New Guinea and Australia we find a string of coral-reefs seven hundred miles in length, the widest gaps not being more than thirty miles. The coral-islets called the Maledivas are four hundred and eighty geographical miles long.

To the early Silurian rocks, corals have supplied a large amount of material. The Oolitic limestones are nothing but consolidated coral-reefs. As much may be said of the Coral Rag. And the vast ranges of the Jura Mountains in Switzerland are formed, to a great extent, in the same way. The mountain-limestone, so conspicuous in many parts of England, is formed chiefly of animal exuviæ mixed with corals.*

* From a remarkable paper, recently published, "Coral and the Coral-Maker," we give an extract:—

"By no means so highly endowed as the insects with which, in common speech, it is generally associated, it is one of the simplest of organized beings; and yet, strange to say, one of the mightiest of agents in producing great physical changes. All the huge creatures that geology has made known put together, with all the whales, and sharks, and great fish innumerable, that have swarmed in the ocean from the days of Adam till now, have done far less to alter the character of the earth's surface than the successive generations of these coral polypes, which have been quietly at work the while in those same waters. And let us here say, that the vast structures which these little creatures raise up from the deep abysses of the

Other animalcules, and various mollusks, contribute largely to the formation of the calcareous rocks, which make so considerable a part of the crust of the earth. The Nummulitic limestones are composed, almost wholly, of Nummulitic exuviæ. They appear in Northern Italy, in the Apennines, on both sides of the Pyrenees, and in the high Alps; in Morocco, Egypt, Greece, and Asia Minor. They may be traced, in fact, at intervals, from the Mediterranean to the borders of India. Sir R. Murchison says they connect the deposits of Europe with those of India,

ocean are really much more curious in their character than most people suppose. The common idea, that coral is a mere assemblage of cells which the coral animals have made to live in, is one of those popular errors which ought to have been long ago exploded. It is nothing of the sort. The little star-like sets of delicate plates which any one may see in a piece of ordinary reef-coral, are no more the sides or walls of a cell in which the coral polype lived, than are the bones of a dog the walls of a cell in which the dog lives. They are the veritable internal skeletons of the coral polypes, and the whole mass of coral is nothing more than so many successive coats or layers of these individual skeletons. This may seem very strange; but it is nevertheless perfectly true. The entire mass of stony matter, forming a branch of ordinary reef-making coral, has been formed within the substance of the polypes that produced it; and each separate star-shaped cluster of plates is neither more nor less than the cast or skeleton of an individual polype.

"It will be obvious, from what has been just said, that the coral animal does not make the coral, at least, in any proper sense of the word. The common notion, that the stony mass is built up particle by particle, as the bee builds its honeycomb, -that the coral is thus something external to the animal, and made by an intentional act,-is altogether a mistake. We have already explained that it is produced within the substance of the polype; and it will be seen that, properly speaking, it cannot be said to be made at all, since it grows, just as much as our own bones grow, and quite as independently of the will of the polype. All that has been said and sung, therefore, about the ingenuity of the little polype as an architect, about its industry and important labours, goes for nothing. It is really no more an architect than an oyster, and its coral-making is in no sort to be regarded as an act of labour. "The true nature of coral-formations will be more apparent, if we consider for a moment in what condition they are found while still growing at the sea-bottom. Let us suppose, then, that, by some contrivance or other, we have managed to get up a mass of living coral from the sides of a coral-reef, and that we have it now before us in a parlour aquarium. What shall we see? Well, observe, in the first place, that the entire mass is covered with a coating of gelatinous flesh, which completely conceals the hard, stony coral. Look narrowly, and you will also perceive that this fleshy coating is nothing more than an extension of the gelatinous substance of the polypes which so thickly stud its surface, and that the entire colony is not merely compacted together as to space, but that there is thus a most intimate organic connexion subsisting between them. Each polype, indeed, has its own separate mouth and tentacles, and its own separate stomach; but, beyond this, it has little claim to be regarded as an independent being. Anyone looking attentively at a mass of living coral in the manner we have supposed, would naturally come to the conclusion that the entire zoophyte is properly to be regarded, not as a society of separate individuals, but as one compound being, fed and nourished by a multiplicity of separate mouths and stomachs. This is undoubtedly the correct view of the coral masses; and it is only on such a supposition that we can explain many of the details of their economy."

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