And said, "Thus far extend, thus far thy bounds,
This be thy just circumference, oh world!"
4. Thus God the heaven created, thus the earth,
Matter unformed and void; darkness profound
Covered the abyss; but on the watery calm
His brooding wings the Spirit of God outspread,
And vital virtue infused, and vital warmth
Throughout the fluid mass:

then founded, then conglobed
Like things to like, the rest to several place
Disparted, and between spun out the air;
And earth, self-balanced, on her centre hung.
5. "Let there be light," said God; and forthwith light
Ethereal, first of things, quintessence pure,
Sprung from the deep, and, from her native east,
To journey through the airy gloom began,
Sphered in a radiant cloud; for yet the sun
Was not: she in a cloudy tabernacle

6.

Sojourned the while. God saw the light was good,
And light from darkness, by the hemisphere,
Divided: light the day, and darkness night,
He named.

Thus was the first day, even and morn:

Nor passed uncelebrated, nor unsung

By the celestial choirs, when orient light

Exhaling first from darkness they beheld;

Birthday of heaven and earth: with joy and shout

The hollow universal orb they filled,

And touched their golden harps, and, hymning, praised
God and his works: Creator him they sung,

Both when first evening was, and when first morn.

LESSON III.- -CHARACTER OF THE GEOLOGICAL HISTORY OF

THE EARTH.

1. GEOLOGY is the science which treats of the materials that compose the earth, and of the organic remains which they contain. According to Sir Charles Lyell, "Geology is the science which investigates the successive changes that have taken place in the organic and inorganic kingdoms of nature; it inquires into the causes of these changes, and the influences which they have exerted in modifying the surface and external structure of our planet."

2. The earth has not always existed in its present condition, and geology gives us a view of its history during a period of unknown length-not only thousands, but perhaps millions of years-long before the creation of man. It appears that, during this time, the earth underwent many

changes; that beds or strata of rock were formed during successive ages at the bottom of the seas by the gradual wearing away of rocks on land, through atmospheric agencies and the action of water, and their deposition on the bed of the ocean in the form of mud, and sand, and gravel; that these strata were sometimes thrown up by subterranean forces; and that hills and valleys were thus formed, and the sea and land often made to change places. But what is more wonderful than all this, and that which gives the study of geology peculiar interest, we have abundant proof that while these operations were going on, there arose a succession of plants and animals, beginning with those of simplest form, often widely different from any now in existence, and advancing to those of higher character, until those nearest the present races appeared.

3. All this wonderful history has been learned in the following manner. From the present appearances of mountain chains, and chasms, and from artificial excavations, geologists have been enabled, after an almost incredible amount of labor and research, directed by the light of science, to rearrange, measure, and examine the different formations called stratified rocks, which are supposed to reach, when unbroken, to the depth of about ten miles below the surface; below which, and of an unknown depth, are the unstratified masses, which show from their position, and the crystalline arrangement of their parts, the action of heat, and an origin earlier in point of time. All but the lower or first formed class of the stratified rocks are found to contain the remains of plants and animals, generally in a fossil state, nearly all of which (except those in the very uppermost strata), to the number of more than thirty thousand species, were different from any that now exist.

4. It is surprising how much may be learned of the structure and habits of animals from a few fossil remains. It is stated that, so mathematically exact are the proportions between the different parts of an animal, "from the character of a single limb, and even of a single tooth or bone, the forms and proportions of the other bones, and the condition of the entire animal, may be inferred. Hence, not only the frame-work of the fossil skeleton of an extinct animal, but also the character of the muscles by which each bone was moved, the external form and figure of the body, the food, and habits, and haunts, and mode of life of creatures that ceased to exist before the creation of the human race, can, with a high degree of probability, be ascertained."

5. Sometimes organic remains, such as bones, are found but partially decayed, and sometimes impregnated with mineral matter; sometimes, through chemical changes, the animal or vegetable matter has entirely disappeared, and the place which it occupied, in what has since become rock, has been so entirely filled with mineral matter as to form a genuine petrifaction; sometimes, after the rock had become hardened, the animal or plant had decayed and escaped through the pores of the stone, so as to leave nothing but a perfect mould; while at other times the only evidence of the existence of an animal is its track in the clay or sand, since hardened into rock.

6. When Shakspeare made his charming Ariel sing

"Full fathom five thy father lies,

Of his bones are coral made,

Those are pearls that were his eyes;
Nothing of him that doth fade
But doth suffer a sea change

Into something rich and strange,"

he little thought how correctly he painted the chemical changes by which, during the ages past, decomposing animal matter has stamped its myriad forms upon what are now the "medals of creation."

7. The organic remains which have thus far been discovered are more abundant than is generally supposed. Fossil shells, in great quantities, have been found both on lofty mountains and below the beds of rivers. On mountains and in mines, hundreds of miles from the sea, are the remains of strange-looking fish; the skeleton of a whale has been found on a mountain three thousand feet high, and the skeleton of an elephant has been exhumed from the frozen sand and mud on the very confines of the Frozen Sea. But, what is more wonderful still, whole mountains, hundreds and even thousands of feet high, are essentially composed of organic remains.

8. Such is the character of the language which the geologist must learn before he can read the curious history of the earth, and of the animal and vegetable races that have lived upon it. A very accurate and extensive knowledge of zoology and botany will also be required, to enable him to ascertain whether the organic remains which he finds in the rocks belonged to extinct species, or are identical with those now living on the globe. That part of geology which gives the history of the remains of plants and animals is called Pal-eon-tol-o-gy, a Greek word which means "the science of ancient beings or creatures."

THE DIFFERENT PERIODS OF THE EARTH'S HISTORY.

a a, Granite veins; b b, metalliferous veins; c c, dike of serpentine; d, dike of porphyry; e e, lava and volcano; f, dike of trap.

The above cut, designed to give a geological view of the earth's history, represents a vertical section of the earth, with the several classes of stratified formations resting upon the unstratified granite rocks, the latter being represented here as thrown up through the superincumbent mass by volcanic agency. By this tilting up of the stratified rocks in numerous localities, so that the edges of even the lowermost of the strata may be seen, both the relative position and the thickness of all the strata have been very accurately ascertained.

1. The geological history of our globe, as gathered from its structure, begins far back-myriads of years beyond our powers of computation, but even then far removed from "the beginning"-in some unknown age of sterility and desolation. If plants and animals then existed, all traces of them were subsequently destroyed by a period of intense heat, which fused the earth's surface into a molten mass, and formed a vast layer, of unknown depth, of what are called the primary or unstratified rocks, of which the enduring granite, the low

est in the series, and the great frame-work of the earth's crust, is the most abundant.*

2. It is granite rock chiefly which is now seen rising to the greatest heights, and stretching into those mountain chains which form the grand natural divisions of the globe. In these cases the granite has been thrown up by subterranean forces, breaking through the superincumbent strata, tilting them up on their edges, and thus affording to the geologist the opportunity of examining them in detail. It is chiefly in veins of the primary rocks that the ores of lead, tin, and the precious metals are found. The celebrated geologist Hugh Miller, in speaking of this primary period of the world's history, in which he supposes that the earth's crust had sufficiently cooled down to permit the existence of a sea, with waves and currents, draws the following imaginary picture:

3. "I dare not speak of the scenery of the period. We may imagine, however, a dark atmosphere of steam and vapor, which, age after age, conceals the face of the sun, and through which the light of moon or star never penetrates; oceans of thermal water, heated in a thousand centres to the boiling point; low, half-molten islands, dim through the fog, and scarce more fixed than the waves themselves, that heave and tremble under the impulsions of the igneous agencies; roaring geysers, that ever and anon throw up their intermittent jets of boiling fluid, vapor, and thick steam, from these tremulous lands; and, in the dim outskirts of the scene, the red gleam of fire, shot forth from yawning cracks and deep chasms, and bearing aloft fragments of molten rock and clouds of ashes. But, should we continue to linger amid a scene so featureless and wild, or venture adown some yawning opening into the abyss beneath, where all is fiery and yet dark-a solitary hell, without suffering or sin-we would do well to commit ourselves to the guidance of a living poet, and see with his eyes, and describe in his verse:

4.

The awful walls of shadows round might dusky mountains seem,
But never holy light hath touched an outline with its gleam;
"Tis but the eye's bewildered sense that fain would rest on form,
And make night's thick blind presence to created shapes conform.
No stone is moved on mountain here by creeping creature crossed,
No lonely harper comes to harp upon this fiery coast:
Here all is solemn idleness; no music here, no jars,
Where silence guards the coast ere thrill her everlasting bars;
No sun here shines on wanton isles; but o'er the burning sheet
A rim of restless halo shakes, which marks the internal heat;
As in the days of beauteous earth we see, with dazzled sight,

The red and setting sun o'erflow with rings of welling light.-THOMAS AIRD. Granite is composed chiefly of mica, quartz, and feldspar; but in some granite rocks talc and hornblende take the place of mica, and then the rock is called sienite. Porphyry is only another modification of granite. † See cut at the head of this lesson.