This phenomenon extending itself by degrees to the whole mass of watery vapour existing in the atmosphere, the waters covered the earth in increasing quantities; and as the conversion of all liquids into vapour is provocative of a notable disengagement of electricity, a vast quantity of electric fluid necessarily resulted from the conversion of such large masses of water into vapour. Bursts of thunder, and bright flashes of lightning were the necessary accompaniments of this extraordinary struggle of the elements — a state of things xvhich M. Maurando has attempted to represent on the opposite page (Plate VII.). How long did this struggle for supremacy between fire and water, with the incessant noise of thunder, continue? All that can be said in reply is, that a time came when water was triumphant. After having covered vast areas on the surface of the earth, it finally occupied and entirely covered the whole surface; for there is good reason to believe that at a certain epoch, at the commencement, so to speak, of its evolution, the earth was covered by water over its whole extent The ocean was universal. From this moment our globe

entered on a regular series of revolutions, interrupted only by the outbreaks of the internal fires which were concealed beneath its still imperfectly consohdated crust. " At the early periods in which the materials of the ancient crystalline schists were accumulated, it cannot be doubted that the chemical processes which generated silicates were much more active than in moie recent times. The heat of the earth's crust was probably then far greater than at present, while a high temperature prevailed at comparatively small depths, and thermal waters abounded. A denser atmosphere, charged with carbonic acid gas, must also have con^ tributed to maintain, at the earth's surface, a greater degree of heat, though one not incompatible with the existence of organic life. " These conditions must have favoured many chemical processes, which in later times have nearly ceased to operate. Hence we find that subsequently to the eozoic times, silicated rocks of clearly marked chemical origin are comparatively rare."*

In order to comprehend the complex action, now mechanical, now chemical, which the waters, still in a heated state, exercised on the solid crust, let us consider what were the components of this crust. The rocks which formed its first stratum — the framework of the earth, the foundation upon which all others repose — may be presumed to have been a compound which, in varying proportions, forms granite and gneiss, and has latterly been designated by geologists Laurentian.

What is this gneiss, this granite, speaking of it with reference to its mineralogical character? It is a combination of silicates, with a base of alumina, potash, soda, and sometimes lime — quartz^ felspar^ and mica form, by their simple aggregation, granite — it is thus a ternary combination, or composed of three minerals.

Qtmrtz, the most abundant of all minerals, is silica more or less pure and often crystallised. Felspar is a crystalline or crystallised mineral, composed of silicate of alumina, potash, soda, or lime; potash-felspar is called orthoclase, soda-felspar albite^ lime-felspar anorthite. Mica is a silicate of alumina and potash, containing magnesia and oxide of iron; it takes its name from the Latin 7nicare, to shine or glitter. Granite (from the Italian gratw, being granular in its structure) is, then, a compound rock, formed of felspar, quartz, and mica, and the three constituent minerals are more or less crystalline. Gneiss is a schistose variety of granite, and composed of the same minerals;

** Address to the American Association for the Advancement of Science," by Thomas Sterry Hunt, LL.D., p. 56. 1871.

the only difference between the two rocks (whatever may be their difference of origin) being that the constituent minerals, instead of being confusedly aggregated, as in granite, assume a foliated texture in gneiss. This foliated structure leads sometimes to gneiss being called stratified granite. " The teiTn gneiss originated with the Freiberg miners, who from ancient times have used it to designate the rock in which their veins of silver-ore were found."*

The felspar, which enters into the composition of granite, is a mineral that is easily decomposed by water, either cold or boiling, or by the water of springs rich in carbonic acid. The chemical action of carbonic acid and water, and the action (at once chemical and mechanical) of the hot water in the primitive seas, powerfully modified the granitic rocks which lay beneath them. The warm rains which fell upon the mountain-peaks and granitic pinnacles, the torrents of rain which fell upon the slopes or in the valleys, dissolved the several alkaline silicates which constitute felspar and mica, and swept them away to form elsewhere strata of clay and sand; thus were the first modifications in the primitive rocks produced by the united action of air and water, and thus were the first sedimentary rocks deposited from the oceanic waters.

The argillaceous deposits produced by this decomposition of the felspathic and micaceous rocks would participate in the still heated temperature of the globe — ^would be again subjected to long continued heat; and when they became cool again, they would assume, by a kind of semi-crystallisation, that parallel structure which is called foliation. All foliated rocks, then, are metamorphic, and the result of a metamorphic action to which sedimentary strata (and even some eruptive rocks) have been subjected subsequently to their deposition and consolidation, and which has produced a re-arrangement of their component mineral particles, and frequently, if not always, of their chemical elements also. In this manner would the first beds of crystalline schist^ such as mica-schist, be formed, probably out of sandy and clayey muds, or arenaceous and argillaceous shales.

At the end of this first phase of its existence, the terrestrial globe was, then, covered, over nearly its whole surface, with hot and muddy water, forming extensive but shallow seas. A few islands, raising their granitic peaks here and there, would form a sort of archipelago, surrounded byseas filled with earthy matter in suspension. During a long series of ages the solid crust of the globe went on increasing in

Cotta's " Rocks Classified and Described," by P. H. Lawrence, p.H 232.

thickness, as the process of solidification of the underlying liquid matter nearest to the surface proceeded. This state of tranquillity could not last long. The solid portion of the globe had not yet attained sufficient consistency to resist the pressure of the gases and boiling liquids which it covered and compressed with its elastic crust. The waves of this internal sea triumphed, more than once, over the feeble resistances which were opposed to it, making enormous dislocations and breaches in the ground — immense upheavals of the solid crust raising the beds of the seas far above their previous levels — and thus mountains arose out of the ocean, not now exclusively granitic, but composed, besides, of those schistose rocks which have been deposited under water, after long suspension in the muddy seas.

On the other hand the Earth, as it continued to cool, would also contract; and this process of contraction, as we have already explained, was another cause of dislocation at the surface, producing either considerable ruptures or simjDle fissures in the continuity of the crust. These fissures would be filled, at a subsequent period, by jets of the molten matter occupying the interior of the globe — by eruptive granite, that is to say — or by various mineral compounds; they also opened a passage to those torrents of heated water charged with mineral salts, with silica, the bicarbonates of lime and magnesia, which, mingling with the waters of the vast primitive ocean, were deposited at the bottom of the seas, thus helping to increase the mass of the mineral substances composing the solid portion of the globe.

These eruptions of granitic or metallic matter — these vast discharges of mineral waters through the fractured surface — would be of frequent occurrence during the primitive epoch we are contemplating. Itshould not, therefore, be a matter for surprise to find the more ancient rocks almost alv/ays fractured, reduced in dimensions by faults and contortions, and often traversed by veins containing metals or their oxides, such as the oxides of copper and tin \ or their sulphides, 'such as those of lead, of antimony, or of iron — which are now the object of the miner's art.

PRIMARY EPOCH.

After the terrible tempests of the primitive period — after these great disturbances of the mineral kingdom — Nature would seem to have gathered herself together, in sublime silence, in order to proceed to the grand mystery of the creation of living beings.

During the primitive epoch the temperature of the earth was too high to admit the appearance of life on its surface. The darkness of thickest night shrouded this cradle of the world; the atmosphere probably was so charged with vapours of various kinds, that the sun's rays were powerless to pierce its opacity. Upon this heated surface, and in this perpetual night, organic life could not manifest itself No plant, no animal, then, could exist upon the silent earth. In the seas of this epoch, therefore, only unfossiliferous strata were deposited.

Nevertheless, our planet continued to be subjected to a gradual refrigeration on the one hand, and, on the other, continuous rains

were purifying its atmosphere. From this time, then, the sun's rays, being less obscured, could reach its surface, and, under their beneficent influence, life was not slow in disclosing itself "Without light," said the illustrious Lavoisier, " Nature was \vithout life; it was dead and inanimate. A benevolent God, in bestowing light, has spread on the surface of the earth organisation, sentiment, and thought." We begin, accordingly, to see upon the earth — the temperature ofwhich was nearly that of our equatorial zone — a few plants and a few animals make their appearance. These first generations of life will be replaced by others of a higher organisation, until at the last stage of the creation, man, endowed with the supreme attribute which we call intelligence, will appear upon the earth. " The word progress^ which we think peculiar to humanity, and even to modem times," said Albert Gaudry, in a lecture on the animals of the ancient world, delivered in 1863, "was pronounced by the Deity on the day when he created the first living organism."

Did plants precede animals? We know not; but such would appear to have been the order of creation. It is certain that in the H 2

lOO THE WORLD BEFORE THE DELUGE.

sediment of the oldest seas, and in the vestiges which remain to us of the eariiest ages of organic life on the globe, that is to say, in the argillaceous schists, we find both plants and animals of advanced organisation. But, on the other hand, during the greater part of the primary epoch — especially during the Carboniferous age — the plants are particularly numerous, and terrestrial animals scarcely show themselves; this would lead us to the conclusion that plants preceded animals. It may be remarked, besides, that from their cellular nature, and their looser tissues composed of elements readily affected by the air, the first plants could be easily destroyed without leaving any material vestiges;from which it may be concluded, that, in those primitive times, an immense number of plants existed, no traces of which now remain to us. We have stated that, during the earlier ages of our globe, the waters covered a great part of its surface; and it is in them that we find the first appearance of life. When the waters had become sufficiently cool to allow of the existence of organised beings, creation was developed, and advanced with great energy; for it manifested itself by the appearance of numerous and very different species of animals and plants. One of the most ancient groups of organic

Fig. 17.— Paradoxides— Bohemia. Bohemicus remains are the Brachiopoda, a group of MoUusca, particularly typified by the genus Lingula, a species of which still exist in the present seas; the Trilobites (Fig. 17), a family of Crustaceans, especially characteristic of this period; then come Productas, Terebratulae, and Orthoceratites — other genera of Mollusca. The Corals, which appeared at an early period, seem to have lived in all ages, and survive to the present day.

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