At this point of the argument, geology appeals to astronomy, to show how widely this principle of chemical change has operated, and still operates, in the universe. We look first at the nebulæ; for here we probably find matter in its most chaotic and attenuated form, constituting self-luminous, diffused masses of vapor. In some of them, however, that matter has begun to condense, doubtless by the radiation of its heat. In the comets, we find probably similar matter, some of it still farther advanced in the process of condensation, so that perhaps a nearly solid nucleus may exist. In the sun and fixed stars, the condensation has gone on so far that cohesive attraction begins to operate, the latent heat of the vapor is extricated, and melted luminous worlds are the result. Around them, however, there probably still floats a wide atmosphere of the more elastic materials, which the heat dissipates, of which the zodiacal light, perhaps, furnishes us with an example. The nebulosity which surrounds the asteroids, Ceres, Pallas, Juno, Vesta, and Astrea, renders it probable that, though they have advanced so far in the process of refrigeration as to become opaque, they may still retain heat enough to dissipate much of their substance. Still farther advanced towards the condition of a habitable world is the moon; and yet volcanic desolation covers its surface. Not improbably Jupiter is nearly surrounded with a fluid like water, and Saturn by a fluid lighter than water—being still farther advanced towards the condition of the earth.
I acknowledge that these are but slight glimpses of the geology and chemistry of other worlds. And yet, taken in connection with the geological history of our own globe, do they not furnish us with some extremely probable examples of those changes to which our earth has been subject? They show us that worlds may exist in the form of vapor, and that some are actually at this time in the various conditions through which geology supposes this world to have passed. Do we not, in these examples, gather strong intimations of a great law of chemical change in the universe? Gaseous matter, so far as we know, appears to have been the earliest state of the universe; and then, by the agency of heat, it passes through the successive changes of liquid and solid, which have been described.
The chemical changes that take place on the earth, under our immediate cognizance, through the agency of water, usually proceed, under favorable circumstances, in a cycle; that is, the substance, after passing through a series of changes, returns at length into the same condition from which it started. Thus aqueous vapor, by the loss of heat, is first converted into water, next into ice, and then, by the access of heat, into water again, and at last into vapor. The question naturally arises, whether those mutations, through which worlds are passing, may not form a similar cycle. We are able to trace them through several steps, from gaseous to liquid, and from the liquid to the solid; and we are assured, on the testimony of Scripture, that the next change of the earth will be from solid to liquid. And in those stars which in past ages have suddenly broken forth with remarkable splendor, and then disappeared, may we not have examples of other worlds burnt up,—not annihilated,—but deluged by fire, and either dissipated or again cooled? What changes, if any, will succeed the final conflagration of the globe, neither science nor revelation informs us.
Yet, if the laws of nature respecting heat are not entirely altered, other changes must follow; and we have seen, in a former lecture, that those changes are perfectly consistent with our ideas of heaven, and that they may, in fact, enhance the happiness of heaven. They may go on forever; in which case, we can hardly doubt but they would form a cycle, though how wide the circuit we cannot conjecture; or they may, at least, reach an unchanging state. I confess, however, that the idea of perpetual change corresponds best with the analogies of the existing universe; and in eternity, as well as in time, it may form an essential element of happiness.
In this world, too, this unceasing change, though it presents at first view a strong tendency to ruin, is, in fact, the grand conservative principle of material things. In a world of life and motion like ours, it is impossible that bodies, especially organic bodies, should not be sometimes subject to violent disarrangements and destruction from the mechanical agencies which exist; and were no chemical changes possible, ultimate and irremediable ruin must be the result. But the chemical powers, inherent in matter, soon bring forth new forms of beauty from the ruins; and, in fact, throughout all nature, the process of renovation usually counterbalances that of destruction; and thus far, indeed, the former has done more than this; for every time nature has changed her dress in past ages, she has put on more lovely robes, and a fresher countenance. Can we doubt that this same principle of change, operating, as it does, on a stupendous scale through the universe, is one of the great means of its preservation? It seems, indeed, paradoxical to say that instability is the basis of stability. But I see not why it is not literally true; and I can hardly doubt but this principle is superior to the laws of gravity—superior to every other law, in fact, for giving permanence and security to the universe.
It is true that, in the case of man, connected as diminution and decay are with the curse denounced on sin, they assume, in his view, a melancholy aspect; and the perishable nature of all created things has ever been viewed by the sentimentalist with sad emotions.
“What does not fade? The tower that long had stood
The crush of thunder, and the warring winds,
Shook by the slow but sure destroyer Time,
Now hangs in doubtful ruins o’er its base;
And flinty pyramids and walls of brass
Descend; the Babylonian spires are sunk;
Achaia, Rome, and Egypt moulder down.
Time shakes the stable tyranny of thrones;
And tottering empires rush by their own weight.
This huge rotundity we tread grows old,
And all those worlds that roll around the sun.
The sun himself shall die, and ancient night
Again involve the desolate abyss.”—Akenside.
If we turn now our thoughts away from man’s dissolution, and think how speedily chemical power will raise nature out of her grave, in renovated and increased beauty, this universal tendency to decay puts on the aspect of a glorious transformation. We connect the changes around us with those which have taken place in the great bodies of the universe; we see them all to be but parts of a far-reaching plan of the Deity, by which the stability of the world is maintained, and its progressive improvement secured. When we look forward, fancy kindles at the developments of divine power, wisdom, and benevolence which will in this manner be made in the round of eternal ages. We see that what our ignorance had mistaken for a defect in nature is, in fact, a great conservative principle of the universe, which Newton did not discover because geology had not yet unfolded her record.
Such are the developments of the divine character and plans unfolded to us by geology. Compare them now with the views which have hitherto prevailed. The common opinion has been, and still, indeed, is, that about six thousand years ago this earth, and, in fact, the whole material universe, were spoken into existence in a moment of time; and that, in a few thousand more, they will, by a similar fiat, be swept from existence, and be no more. On the other hand, geology places the time when the matter of the universe was created out of nothing at an epoch indefinitely but immensely remote. Since that epoch, this matter has passed through a multitude of changes, and been the seat of numerous systems of organic life, unlike one another, yet all linked together into one great system by a most perfect unity; each minor system being most beautifully adapted to its place in the great chain, and yet each successive link becoming more and more perfect. Nor does geology admit that any evidence exists of the future annihilation of the material universe; but rather of other changes, by which new and brighter displays of divine wisdom and benevolence shall be brought out, it may be in endless succession. Geology is not, indeed, insensible to the displays of the divine character which are exhibited on the present theatre of the world. Indeed, she distinctly recognizes the act which is now passing as the most perfect of all. Yet this scene of the great drama she regards as only one of the units of a similar series of changes that have gone by or will hereafter come; the chain stretching so far into the eternity that is past and the eternity that is to come, that the extremities are lost to mortal vision.
Do any shrink back from these immense conclusions, because they so much surpass the views they have been accustomed to entertain respecting the beginning and the end of the material universe? But why should they be unwilling to have geology liberalize their minds as much in respect to duration as astronomy has done in respect to space? Perhaps it is a lingering fear that the geological views conflict with revelation. Such fears formerly kept back many from giving up their souls to the noble truths of astronomy. But they learnt, at length, that astronomy merely illustrates, and does not oppose, revelation. It showed men how to understand certain passages of sacred writ respecting the earth and heavenly bodies which they had before misinterpreted. Just so is it with geology. There is no collision between its statements and revelation. It only enables us more correctly to interpret some portions of the Bible; and then, when we have admitted the new interpretation, it brings a flood of light upon the plans and attributes of Jehovah. Geology, therefore, should be viewed, as it really is, the auxiliary both of natural and revealed religion. And when its religious relations are fully understood, theology, I doubt not, will be as anxious to cultivate its alliance as she has been fearful of it in days past.