It is difficult to reply with any confidence to this question; nevertheless, our readers will not object to accompany us a step further, while we express an opinion, founded on a.n.a.logy and scientific induction.

What are the causes which have produced the present inequalities of the globe--the mountain-ranges, continents, and waters? The primordial cause is, as we have had frequent occasion to repeat, the cooling of the earth, and the progressive solidification of the external crust, the nucleus of which still remains in a fluid or viscous state. These have produced the contortions, furrows, and fractures which have led to the elevation of the great mountain-ranges and the depression of the great valleys--which have caused some continents to emerge from the bed of ocean and have submerged others. The secondary causes which have contributed to the formation of a vast extent of dry land are due to the sedimentary deposits, which have resulted in the creation of new continents by filling up the basins of the ancient seas.

Now these two causes, although in a minor degree, continue in operation to the present day. The thickness of the terrestrial crust is only a small fraction compared to that of the internal liquid ma.s.s. The princ.i.p.al cause, then, of the great dislocations of the earth's crust is, so to speak, at our gates; it threatens us unceasingly. Of this the earthquakes and volcanic eruptions, which are still frequent in our day, give us disastrous and incontestable proofs. On the other hand, our seas are continually forming new land: the bed of the Baltic Sea, for instance, is gradually rising, in consequence of the deposits which will obviously fill up its area entirely in an interval of time which it might not be impossible to calculate.

It is, then, probable that the actual condition of the surface and the respective limits of seas and continents have nothing fixed or definite in them--that they are, on the contrary, open to great modifications in the future.

There is another problem much more difficult of solution than the preceding, but for which neither induction nor a.n.a.logy furnish us with any certain data--viz., the perpetuity of our species. Is man doomed to disappear from the earth some day, like all the races of animals which preceded him, and prepared the way for his advent? Will a new _glacial period_, a.n.a.logous to that which, during the Quaternary period, was felt so rigorously, again come round to put an end to his existence? Like the Trilobites of the Silurian period, the great Reptiles of the Lias, the Mastodons of the Tertiary, and the Megatheriums of the Quaternary epoch, is the human species to be annihilated--to perish from the globe by a simple natural extinction? Or must we believe that man, gifted with the attribute of reason, marked, so to say, with the Divine seal, is to be the ultimate and supreme term of creation?

Science cannot p.r.o.nounce upon these grave questions, which exceed the competence, and extend beyond the circle of human reasoning. It is not impossible that man should be only a step in the ascending and progressive scale of animated beings. The Divine Power which has lavished upon the earth life, sentiment, and thought; which has given organisation to plants; to animals, motion, sensation, and intelligence; to man, in addition to these multiple gifts, the faculty of reason, doubled in value by the ideal--reserves to Himself perhaps in His wisdom the privilege of creating alongside of man, or after him, a being still more perfect. This new being, religion and modern poesy would present in the ethereal and radiant type of the Christian angel, with moral qualities whose nature and essence would escape our perceptions--of which we could no more form a notion than one born blind could conceive of colour, or the deaf and dumb of sound. _Erunt aequales angelis Dei._ "They will be as the angels of G.o.d," says Holy Scripture, speaking of man raised to the life eternal.

During the Metamorphic epoch the _mineral kingdom_ existed alone; the rocks, silent and solitary, were all that was yet formed of the burning earth. During the Primary epoch, the vegetable kingdom, newly created, extended itself over the whole globe, which it soon covered from pole to pole with an uninterrupted ma.s.s of verdure. During the Secondary and Tertiary epochs, the vegetable and animal kingdoms divided the earth between them. In the Quaternary epoch the _human kingdom_ appeared. Is it in the future destinies of our planet to receive yet another lord?

And after the four kingdoms which now occupy it, is there to be a _new kingdom_ created, the attributes of which can never be anything but an impenetrable mystery, and which will differ from man in as great a degree as man differs from the other animals, and plants from rocks?

We must be contented with suggesting, without hoping to solve, this formidable problem. It is a great mystery, which, according to the fine expression of Pliny, "lies hidden in the majesty of Nature," _latet in majestate naturae_; or (to speak more in the spirit of Christian philosophy) it is known only to the Almighty Creator of the Universe.