Part 2 (1/2)

he adds, emphatically, ”the _terrestrial gravitation_. Magnetic needles freely suspended show its meridional or directive polar force, and that the force converges at two opposite parts, which are bounded by the Antarctic and Arctic circles.”

This polar force, like a stream, is constantly moving from pole to pole; and experiment proves that this movement is from the South Pole to the North. ”Hence the various terrestrial substances, solids and fluids, through which this subtle and universal power permeates, are controlled, propelled, and modified over the entire surface of our globe, commencing at the south and dissolving at the north. Thus, all terrestrial matter moves towards the Arctic region, and finally disappears by dissolution and absorption, to be renewed again and again in the Antarctic Sea to the end of time.”

In order to prove that the north polar basin is the receptacle of the final dissolution of all terrestrial substances, Mr. Hopkins quotes the Gulf Stream. Bottles, tropical plants, and wrecks cast into the sea in the South Atlantic, are carried to Greenland in a comparatively short time. The great _tidal_ waves commence at the fountain-head in the Antarctic circle, impinge against the south coast of Tierra del Fuego, New Zealand, and Tasmania, and are then propelled northward in a series of undulations. The South Atlantic stream, after doubling the Cape of Good Hope, moves towards the Guinea coast, bends towards the Caribbean Sea, producing the trade winds; again leaves Florida as the Gulf Stream, and washes the coasts of Greenland and Norway, and finally reaches the north polar basin.

Again the great polar force shows itself in the arrangement of the mineral structure below. In all the primary rocks in every quarter of the globe where they have been examined, its action is recognised in giving to the crystalline ma.s.ses--granites and their laminated elongations--a polar grain and vertical cleavage. ”Had it been possible to see our globe stripped of its sedimentary deposits and its oceanic covering, we should see it like a gigantic melon, with a uniform grain extending from pole to pole.” This structure appears to give polarity to earthquakes--thermal waters and earthquakes--which are all traceable in the direction of the polar grain or cleavage from north to south.

In England, for instance, thermal and saline springs are traceable from Bath, through Cheltenham, to Dudley. In Central France, mineral springs occur in lines, more or less, north and south. All the known salt-springs in South America occur in meridional bands. Springs of chloride of sodium in the Eastern Cordilleras stretch from Pinceima to the Llanoes de Meta, a distance of 200 miles. The most productive metalliferous deposits are found in meridional bands. The watery volcanoes in South America are generally situated along the lines of the meridional splits and the secondary eruptive pores on the transverse fractures. The sudden ruptures arising locally from increasing tension of the polar force, and the rapid expansion of the generated gases, produce a vibratory jar in the rocky structure below, which being propagated along the planes of the polar cleavage, gives rise to great superficial oscillations, and thus causes earthquakes and subterranean thunder for thousands of miles, from south to north.

In 1797, the district round the volcano of Tunguraqua in Quito, during one of the great meridional shocks, experienced an undulating movement, which lasted upwards of four minutes, and this was propagated to the sh.o.r.es of the Caribbean Sea.

All these movements demonstrated, according to Mr. Hopkins, that the land as well as the ocean moves from the south pole and north pole, and that the magnetic power has a tendency to proceed from pole to pole in a _spiral_ path from south-east to north-west, a movement which produces an apparent change in the equinoxes, or the outer section of the plane of the ecliptic with the equator, a phenomenon known to astronomers as the precession of the equinoxes.

Such is a very brief summary of the arguments by which Mr. Evan Hopkins maintains the literal correctness of the Mosaic account of the creation, and attempts to show that all the facts discovered by geologists may have occurred in the ages included in the Mosaic chronology.

That the mysterious power of terrestrial magnetism can perform all that he claims for it, we can perhaps admit. But how does this explain the succession of Silurian, Old Red Sandstone, Carboniferous and other strata, up to the Tertiary deposits, with their fossils, each differing in character from those of the preceding series? That these were successive creations admits of no doubt, and while it is undeniable that the fiat of the Creator could readily produce all these phenomena, it may reasonably be asked if it is probable that all these myriads of organic beings, whose remains serve as records of their existence, were created only to be immediately destroyed.

Again, does not the author of the ”Principles of Terrestrial Physics”

prove too much? He admits that 3,000 years ago the climate of England was tropical: he does not deny that a subsequent period of intense cold intervened, 2,550 years ago. He admits historical records, and 2,350 years ago Pythagoras constructed his cosmography of the world, which has never been seriously impugned; and yet he has no suspicion that countries so near to his own had changed their climates first from tropical to glacial, and back again to a temperate zone. It is not reasonable to believe this parable.

The school of philosophy generally considered to be the most advanced in modern science has yet another view of cosmogony, of which we venture to give a brief outline. s.p.a.ce is infinite, says the exponent of this system,[9] for wherever in imagination we erect a boundary, we are compelled to think of s.p.a.ce as existing beyond it. The starry heavens proclaim that it is not entirely void; but the question remains, are the vast regions which surround the stars, and across which light is propagated, absolutely empty? No. Modern science, while it rejects the notion of the luminiferous particles of the old philosophy, has cogent proofs of the existence of a luminiferous ether with definite mechanical properties. It is infinitely more attenuated, but more solid than gas.

It resembles jelly rather than air, and if not co-extensive with s.p.a.ce, it extends as far as the most distant star the telescope reveals to us; it is the vehicle of their light in fact; it takes up their molecular tremors and conveys them with inconceivable rapidity to our organs of vision. The splendour of the firmament at night is due to this vibration. If this ether has a boundary, ma.s.ses of ponderable matter may exist beyond it, but they could emit no light. Dark suns may burn there, metals may be heated to fusion in invisible furnaces, planets may be molten amid intense darkness; for the loss of heat being simply the abstraction of molecular motion by the ether, where this medium is absent no cooling could take place.

[9] Professor Tyndall in _Fortnightly Review_.

This, however, does not concern us; as far as our knowledge of s.p.a.ce extends, we are to conceive of it as the holder of this luminiferous ether, through which the fixed stars are interspersed at enormous distances apart. a.s.sociated with our planet we have a group of dark planetary ma.s.ses revolving at various distances around it, each rotating on its axis; and, connected with them, their moons. Was s.p.a.ce furnished at once, by the fiat of Omnipotence, with these burning orbs? The man of science should give no answer to this question: but he has better materials to guide him than anybody else, and can clearly show that the present state of things _may_ be derivative. He can perhaps a.s.sign reasons which render it probable that it _is derivative_. The law of gravitation enunciated by Newton is, that every particle of matter in the universe attracts every other particle with a force which diminishes as the square of the distance increases. Under this law a stone falls to the ground, and heat is produced by the shock; meteors plunge into the atmosphere and become incandescent; showers of such doubtless fall incessantly upon the sun, and were it stopped in its...o...b..t, the earth would rush towards the sun, developing heat in the collision (according to the calculations of MM. Joule, Mayer, Helmholtz, and Thomson), equal to the combustion of five thousand worlds of solid coal. In the attraction of gravity, therefore, acting upon this luminous matter, we have a source of heat more powerful than could be derived from any terrestrial combustion.

To the above conception of s.p.a.ce we must add that of its being in a continual state of tremor. The sources of vibration are the ponderable ma.s.ses of the universe. Our own planet is an aggregate of solids, liquids, and gases. On closer examination, these are found to be composed of still more elementary parts: the water of our rivers is formed by the union, in definite proportions, of two gases, oxygen and hydrogen. So, likewise, our chalk hills are formed by a combination of carbon, oxygen, and calcium; elements which in definite proportions form chalk. The flint found within that chalk is compounded of oxygen and silicon, and our ordinary clay is for the most part formed by a union of silicon, oxygen, and aluminum. By far the greater part of the earthy crust is thus compounded of a few elementary substances.

Such is Professor Tyndall's view of the universe, rising incidentally out of his theory of heat, his main object being to elucidate his theory of heat and light.

MODIFICATIONS OF THE SURFACE OF THE GLOBE.

As a consequence of the hypothesis of central heat, it is admitted that our planet has been agitated by a series of local disturbances; that is to say, by ruptures of its solid crust occurring at more or less distant intervals. These partial revolutions at the surface are supposed to have been produced, as we shall have occasion to explain, by upheavals or depressions of the solid crust, resulting from the fluidity of the central parts, and by the cooling down of the external crust of the globe.

Almost all bodies, in pa.s.sing from a liquid to a solid state, are diminished in size in the process. In molten metals which resume the solid state by cooling, this diminution amounts to about a tenth of their volume; but the decrease in size is not equal throughout the whole ma.s.s. Hence, as a result of the solidification of the internal parts of the globe, the outer envelope would be too large; and would no longer fit the inner sphere, which had contracted in cooling. Cracks and hollows occur under such circ.u.mstances, even in small ma.s.ses, and the effect of converting such a vast body as the earth from a liquid, or rather molten condition, to a solid state, may be imagined. As the interior became solid and concrete by cooling, furrows, corrugations, and depressions in the external crust of the globe would occur, causing great inequalities in its surface; producing, in short, what are now called _chains of mountains_.

At other times, in lieu of furrows and irregularities, the solid crust has become ruptured, producing fissures and fractures in the outer envelope, sometimes of immense extent. The liquid substances contained in the interior of the globe, with or without the action of the gases they enclose, escape through these openings; and, acc.u.mulating on the surface, become, on cooling and consolidating, _mountains_ of various heights.

It would also happen, and always from the same cause, namely, from the internal contraction caused by the unequal cooling of the globe, that minor fissures would be formed in the earth's crust; incandescent liquid matter would be afterwards injected into these fissures, filling them up, and forming in the rocky crust those long narrow lines of foreign substances which we call _d.y.k.es_.

Finally, it would occasionally happen, that in place of molten matter, such as granite or metalliferous compounds, escaping through these fractures and fissures in the globe, actual rivers of boiling water, abundantly charged with various mineral salts (that is to say, with silicates, and with calcareous and magnesian compounds), would also escape, since the elements of water would be abundant in the incandescent ma.s.s. Added to these the chemical and mechanical action of the atmosphere, of rain, rivers, and the sea, have all a tendency to destroy the hardest rocks. The mineral salts and other foreign substances, entering into combination with those already present in the waters of the sea, and separating at a subsequent period from these waters, would be thrown down, and thus const.i.tute extensive deposits--that is to say, _sedimentary formations_. These became, on consolidation, the _sedimentary rocks_.

The furrows, corrugations, and fractures in the terrestrial crust, which so changed the aspect of the surface, and for the time displaced the sea-basins, would be followed by periods of calm. During these periods, the debris, torn by the movement of the waters from certain points of the land, would be transported to other parts of the globe by the oceanic currents. These acc.u.mulated heterogeneous materials, when deposited at a later period, would ultimately const.i.tute formations--that is, _transported or drifted rocks_.

We have ventured to explain some of the theories by which it is sought to explain the cosmography of the world. But our readers must understand that all such speculations are, of necessity, purely hypothetical.

In conformity with the preceding considerations we shall divide the mineral substances of which the earth is composed into three general groups, under the following heads:--

1. _Eruptive Rocks._--Crystalline, like the second, but formed at all geological periods by the irruption or intrusion of the liquid matter occupying the interior of our globe through all the pre-existing rocks.