Imatges de pÓgina
PDF
EPUB

"This mortal chasm, in the succession of mineral formations, breaks the chain of the Huttonians. It is the death blow of their theory; demonstrating that the present earth has resulted from definite creative Fiats; and not from the progressive operations of any merely physical forces whatsoever. It is therefore to be regretted, that a mind so accomplished as that of Professor Playfair should have devoted so many studious years to the decoration of the phantoms described by him in the following paragraph.

"How often these vicissitudes of decay and renovation have been repeated, is not for us to determine; they constitute a series, of which, as the author of this theory has remarked, we neither see the beginning nor the end; a circumstance that accords well with what is known concerning other parts of the economy of the world. In the continuation of the different species of animals and vegetables that inhabit the earth, we, discern neither a beginning nor an end; and in the planetary motions, where geometry has carried the eye so far both into the future and past, we discover no mark either of the commencement or of the termination of the present order. It is unreasonable, indeed, to suppose that such marks should any where exist. The Author of Nature has not given laws to the universe, which, like the institutions of men, carry in themselves the elements of their own destruction. He has not permitted in his works any symptom of infancy or old age, or any sign by which we may estimate either their future or past duration. These phenomena, then, are all so many marks of the lapse of time, among which the principles of geology enable us to distinguish a certain order, so that we know some of them to be more, and others to be less distant, but without being able to ascertain, with any exactness, the proportion of the immense intervals which separate them. These intervals admit of no comparison with the astronomical measures of time; they cannot be expressed by the revolutions of the sun or the moon; nor is there any synchronism between the most recent epochas of the mineral kingdom, and the most ancient of our ordinary chronology.'

"Our ordinary chronology comprehends the deluge, a great epocha of the mineral kingdom, the truth of which is obviously discarded by Mr. Playfair. In the third part of the present work, ample evidence will be adduced from Cuvier and other practical naturalists, of the reality of that recent epocha, and of its synchronism with our chronology. Moreover, it will be shown in our second part, that the mineral strata contain formations, which discover marks of the commencement' of the

different species of vegetables and animals that peopled the earth. The astronomical comparison is a strange solecism for so acute a logician to commit. The cases are quite discrete, and destitute of any true analogy. The laws of the planetary motions are represented in a system of mechanical theorems, which relate solely to co-existing phenomena. The principles of their actual equilibrium apply equally to all past and future time. The appearances reveal nothing in the past, or the future, different from the present, except change of relative position among separate masses. The physical constitution of the planets, which could alone afford, in their anterior metamorphoses, kindred or parallel facts for geology, are beyond our cognisance. In the mineral structure of the earth, we shall find symptoms of infancy, as well as on its surface, considered as the dwelling-place of man."

Our author gives the Wernerian theory fair play, in judging it by D'Aubuisson's temperate representation. On this, its most reasonable form, we find the following observations; in which we perfectly concur.

"It would be superfluous, indeed, to offer an elaborate refutation of a world-building hypothesis, so extravagant, so visionary, and so inconsistent with every principal of mechanical and chemical science. Whence arose that immense chaotic ocean, within whose bosom the summits of the Himmalaya and the Andes were crystallised? Whither did it retire in measured stages of descent, to allow the primary and secondary rock formations, to lay their successive platforms, in the amphitheatre of the globe? The atmosphere has a finite extent, not expanding into space beyond a limited distance from the earth; and thus that world of waters could not escape into another sphere, in vaporous exhalations. The quantity of water requisite to cover the globe to the height of the Himmalaya, or 27,000 feet, would be as great as the whole mass of our actual ocean. Werner was too little of a philosopher to calculate that his crystallisation plan called on him to provide a receptacle for 1000 millions of cubic miles of water. The great density of the interior body of the earth precludes the possibility of that receptacle being subterranean. Since neither celestial nor terrestrial space will admit his retiring chaotic ocean, itself must be deemed an inadmissible supposition. Even granting its reality, and allowing moreover that this water was adequate to dissolve the now insoluble granitic mountains, so as to form a clear and tranquil fluid, we may ask, why the solvent that then exercised so marvellous an affinity for the siliceous and aluminous earths, came so soon to discard them

[

altogether from its bosom ? The attractive force that made the solution should have maintained it. To imagine an effect to come to pass without a cause, is sufficiently ridiculous, though not without a parallel in modern philosophy; but to expect a solidifying action, a stony deposit, from a liquefying agent, unabated in force and magnitude, is truly absurd. The other assumption of the clear and tranquil solution becoming spontaneously muddy and disturbed, as it parted with, its solid contents, is repugnant no less to common sense, than to chemical experience. A still liquid containing soluble and insoluble matter usually deposits the insoluble, which is mechanically diffused, before the crystals appear, provided the latter be regularly aggregated, as occurs in granite. We shall not waste more words on this analysis; but conclude with expressing our astonishment that the theoretic dreams of Werner should ever have been regarded as realities, in the present age." a

f

3

་ ་་

11.

The body of Dr. Ure's work is distributed into three books; each containing several chapters. The first book comprehends what may be called, on Dr. Ure's principles, primordial creation, including primitive rocks. Chapters I. II. III. treat respectively of heat, light, and the atmosphere. In Chapter IV., entitled Primeval Land and Ocean," some of our author's new thoughts on the structure and revolutions of the earth begin to appear...

!

Circumstances, which will transpire in the progress of our researches, cause me to assign a different proportion between the dry and humid surface in the primeval globe, from that which now prevails. I am led to conclude, that the area of the land bore to that of the water, probably the ratio of equality, instead of nearly 100 to 365, as at present. One obvious consequence of this condition was, that the depth of the primeval ocean was greater, as its superficial expanse was less. By this means, the water came into far deeper and more extensive contact with those ignited, combustible, and explosive materials, which the phenomena of mines and volcanoes demonstrate to exist within the crust of the globe."

[ocr errors]
[ocr errors]

-woff Multiplied observations have shown, that the crust of the earth is composed superficially, or to a moderate depth, of certain stratiform or schistose rocks, which, being devoid of organic remains, are termed primitive...We shall at present confine our attention to two of them, called gneiss and mica-slate. These are arranged in planes usually parallel to each other, the mica-slate being, for the most part, uppermost. We have

1

reason to believe, that hardly any district of the terrestrial surface is destitute of these great slaty rocks, though in many places they may be deeply covered over with secondary formations, and therefore inaccessible. Gneiss constitutes the body of the Himmalaya mountains, and abounds among the Andes, Alps, Urals, Pyrenees. It forms also Ross island, the most northern known land of the globe. Mica-slate is nearly coextensive. But their wide-stretched foliated planes are seldom or never horizontal, or concentrate with the curvature of the earth. They usually lie at highly inclined angles, like tables resting on their edges, in a nearly vertical position. In very many localities, vast irregular masses of granite are seen rising up through the schistose fields, as if these had been upheaved and dislocated by its protrusion, and were thrown-like mantles round its shoulders and base..

Ca 50 gang

1

We therefore conclude, that the primordial earth, as it lay beneath the circumfused abyss, was at first endowed with concentric coats of gneiss, mica-slate, and the other primitive schists; that at the recorded command of the Almighty, a general eruption and protrusion of the granitic, syenitic, porphyritic, and other unstratified rocks, took place, which broke up and elevated the schists into nearly vertical planes, similar to what now exist, leaving commensurate excavations for the basin of the sea.

[ocr errors]

"In meditating on this mighty operation, though we may shrink from the overwhelming scene, and feel our faculties abased, nay annihilated as it were, in the presence of that Power, who hath measured the waters in the hollow of his hand, weighed the mountains in scales, and the hills in a balance; who sitteth upon the circle of the earth, and stretcheth -out the heavens as a curtain,' yet the magnitude of these terrestrial disruptions will create no difficulty in the mind of the astronomer, familiar with acts of Omnipotence incomparably more stupendous. Even the geographer would smile at the geologist, who should ask for Deity a countless lapse of ages to build upon the earth its superficial scaffolding, whose size is to its total bulk, as the roughness of the rind to the ball of the orange."

The constitution of water, as described in this chapter, shows what interest a philosophical spirit may infuse into the tritest subjects. 0039; Taolisie mit

**

D

This water, by its mysterious tenuity, loosens the indurated soil, enters the invisible pores of plants, passes freely through all their vessels, expands in the filmy blossom, and is an element of the fleeting aroma, But these fluid particles can be

Pu

chained together in the firmest cohesion: in which state it may exhibit either the hardness of rock, or the softness of eider-down. Enormous blocks of water thus stand in immov able columns, surmounting the loftiest pinnacles of our globe. How different are these from the soft insinuating liquid, which is the circulating medium of all organic life!

"Every common water in its natural state, whether salt or fresh, contains about a fortieth of its bulk of air, which it readily evolves either by the heat of ebullition, or when placed in vacuo. In these circumstances, we perceive minute globules oozing out from every point of the liquid, which when liberated, rise by their innate lightness and elasticity, in a pearly-looking stream to the surface. Now this liquified air is the element of respiration, the pabulum vitæ, to all bronchial animals. The gills of fish elaborate that liquid air, as the lungs of land animals do its elastic form. Both organs convert its oxygenous part into carbonic acid, for the sustenance of vegetation, terrestrial or submarine.

"Enough has now been stated to evince, that water in its liquid state is not the uninteresting, inert element which the multitude suppose it to be, but that its constitution is most refined and intentional, adapted to the manifold functions which it must discharge towards countless orders of organic and inorganic being. Its habitudes with heat are peculiarly beautiful. A certain energy of this power gives to water its liquid condition, in which, as already mentioned, the molecular attraction is very nearly neutralised by the repulsive force. Had the cohesion of its parts been less, it could not have afforded the reaction requisite for the movements of fishes and ships; nor could man have availed himself of its impulsion to aid his feeble arm in preparing his food, clothing, and domestic ac. commodation. The same calorific agency wafts the ponderous liquid on the wings of the wind, to supply the organic inhabitants of mountains and plains with vivifying moisture; or under the guidance of mechanic genius, it animates the steamengine, the noblest offspring of science and art, the unwearied and docile servant of man.

“The equilibrium of its mobility lies within narrow bounds. A very moderate reduction of temperature restores the cohesive power to uncontrolled dominion, under which the form of water ceases to exist, and might thus continue unknown. Again, had the particles of water been mutually elastic, though but in an inconsiderable degree, the least disturbance by winds or tides must have produced tremendous commotions in its mass; and a floating body would have been alternately tossed

« AnteriorContinua »