Part 25 (1/2)

_In the seventh and last place, geology has given great enlargement to our knowledge of the divine plans and operations in the universe, and in the following particulars_:--

1. It expands our ideas of the time in which the material universe has been in existence as much as astronomy does in regard to its extent.

To those not familiar with the details of geology, this will probably seem a startling and extravagant a.s.sertion. There has been, and still is, an extreme sensitiveness in the minds of intelligent men on this subject. And I highly respect the ground from which their apprehensions spring, viz., a fear that to admit the great antiquity of the globe would bring discredit upon revelation. And yet I believe the most candid and able theologians of the present day do not fear that to admit the existence of the matter of the world previous to the six days' work of creation, is inconsistent with the Mosaic statement. But if we allow any period between its creation and the six demiurgic days, it is no more derogatory to Scripture to make that period ten millions of years than ten years. For if the sacred writer would pa.s.s over ten years in silence, he could, with the same propriety, pa.s.s over ten millions. Now, the longer I study geology, the nearer do my ideas approximate to the latter number as a measure of the earth's duration. Let us contemplate a few facts. We are able to trace the geological changes that have taken place on the earth since man's existence upon it with a good deal of accuracy. For since his remains are found only in alluvium, we must regard all changes that took place previous to the deposition of that formation to have been of an earlier date than his creation. Now, what are the changes which the last six thousand years have witnessed? In some places, the agency of rivers and other causes have made an acc.u.mulation of alluvial matter to the depth of not more than one or two hundred feet, although in particular places it is several hundred feet. These deposits have been pushed forward at the mouths of some large rivers, so as to cover hundreds, and even thousands, of square miles. Oceanic currents have also made deposits in the bottom of wide seas of considerable extent; and in some limited spots these deposits have been consolidated into rock. The action of frost and gravity, also, has crumbled from precipitous ledges angular fragments enough to form a slope of detritus sometimes a hundred feet high. The polyparia, or coral builders, have advanced their work only a few feet in thickness during this period, and soils have acc.u.mulated in some places about as much. Volcanic action has occasionally thrown up a new island from the ocean's bed; but only a few of them have been permanent. Some tracts of country, in no case more than a few hundred miles in extent, have, by the same agency, been raised a few feet, or sunk down the same amount. But after all, the earth's surface remains essentially the same as when man was placed upon it.

Now, compare these slight changes with those which have preceded it, through the operation of the same agencies, since the first existence of animals upon the globe. I will not contend, with some distinguished geologists, that these same changes have always operated with the same intensity as at present. But there are several circ.u.mstances which show that the depositions from water could not have been essentially different in ancient and modern times. Now, just compare six or eight miles in thickness of the fossiliferous deposits of the previous periods with the two hundred feet of alluvium acc.u.mulated during the historic period; and, after you have made all reasonable allowance for the greater intensity of action in former times, you will still find yourselves confounded by the incalculable time requisite to pile up such an immense thickness of materials, and then to harden most of them into stone; especially when you call to mind the numerous changes of organic life, and the vast amount of animal remains which they exhibit. A superficial observer might lump such a work, and crowd it into a few thousand years. But the more its details are studied, the longer does the period appear that is requisite for its production. Each successive investigation discovers new evidence of changes in composition, or organic contents, or of vertical movements effected by extremely slow agencies, so as to make the whole work immeasurably long.

But when we have gone back to the commencement of animal existence on the globe, we have taken but one step in our review of its early history. The next backward step embraces that wide period during which the stratified, non-fossiliferous rocks--far thicker than the fossiliferous--were deposited; probably by the agency of fire and water. Or if we adopt the metamorphic theory of Mr. Lyell, we shall be still more deeply impressed by the length of that period, during which these rocks were in a course of deposition, consolidation, and metamorphosis. For he supposes them originally deposited from water, just as mud, sand, and gravel now are acc.u.mulating in the ocean's bed, and to have enveloped organic beings, as similar materials now do. Next the whole were consolidated, so as to form the exact prototype of the existing fossiliferous rocks; and finally it underwent almost complete fusion, by the slow propagation of internal heat upwards, until all the organic contents were obliterated, and a crystalline structure was subst.i.tuted. Nay, according to this theory, other systems of rocks, of an a.n.a.logous character, may have preceded the present primary stratified ones, and have been at length entirely melted into the unstratified; so that we cannot say when organic life first began on the globe. But I will not press this theory, because most of the ablest geologists reject it, at least in its full extent. And we have a period long enough to confound the imagination, if we take the common view, which supposes the non-fossiliferous rocks to have been deposited from water, at a temperature too high to admit the existence of organic beings.

We have now gone back to that point in the earth's history when a crust had begun to form over the sh.o.r.eless ocean of melted matter, of which we have reason to suppose it was then composed. Shall we attempt to trace back that history any farther? The light does, indeed, grow dim, and the clew more and more uncertain, the farther we recede along the track of the earth's existence. Still there are some scattered rays that seem to recall to us a condition of the earth still earlier than that in which it const.i.tuted a molten globe. It may have been dissipated into vapor, like a comet, or a nebula; and subsequently, by the slow radiation of its heat, have been condensed into an opaque, though a melted, incandescent ma.s.s.

Several a.n.a.logies certainly throw an air of plausibility over this hypothesis. And if such was, indeed, the earliest condition of the earth, the time requisite to condense it into melted matter must have been longer than any other period of its history.

Who, now, at all familiar with the dynamics of geological agencies, shall undertake to give an arithmetical expression to the periods that make up the world's entire history? Not only does the reasoning faculty fail to grasp the entire sum, but even imagination, as she flies backwards through period after period, tires in the effort, and brings back not even a conjectural result. The same feeling does, in fact, come over the mind, which she experiences when astronomy has hurried her from world to world, from sun to sun, from system to system, from nebula to nebula, and yet she seems no nearer to the limits of creation than when she started. We know certainly that there are limits; because matter cannot be infinite. But we cannot conjecture where they are fixed. We know, also that there was a time when this world did not exist, an epoch when its entire ma.s.s was spoken into existence by the fiat of Jehovah; because the Bible expressly declares it. But that epoch is unrevealed. If there is any truth in geology, it was certainly more than six thousand years ago. Nay, that science carries us as far back into the arcana of time as astronomy does into the arcana of s.p.a.ce. Neither the distance in the one case, nor the duration in the other, can be estimated. But there is a sublime inspiration in the effort to grasp the subject; and I see not why there is not as much grandeur and high gratification in the idea of vast duration as of vast expansion. And I see not why we do not gain as much enlargement of our conceptions of the plans of Jehovah respecting the universe in the one case as in the other. We cannot but infer, from the pre-Adamic state of our world, that it must have subserved other purposes than to sustain its present inhabitants.

2. In the second place, geology gives us impressive examples of the extent of organic life on the globe since its creation.

I shall not contend, with some geologists, that even the primary crystalline rocks may once have been filled with organic remains, which have been obliterated by heat; and that, in this way, there may have been a number of creations of organized beings on the globe, of which no trace now remains. I take as the basis of my argument only the relics of animals and plants actually found in the rocks. And when one sees mountain ma.s.ses, often of small sh.e.l.ls, and spread over wide areas, he is amazed to learn how prolific nature has been. What a countless number of vegetables, too, must have been required to produce beds of coal from one to fifty feet thick, and extending over thousands of square miles, and alternating several times with sandstone in the same basin! There is reason to believe, too, that the number of animals preserved in the strata bears only a small proportion to those which have been utterly destroyed and decomposed into their original elements. For example, in the sandstone along Connecticut River, the tracks of more than forty species of bipeds and quadrupeds have been found most distinctly marked. Some of these bipeds must have been of colossal size--as much as twelve or fifteen feet in height. And yet scarcely any other vestige of their existence has been discovered. They were the giant rulers of that valley for centuries; but they have all vanished. How numerous, then, may have been the softer animals of the ancient world, which have not left even a footmark to certify their existence to coming generations!

But the facts recently brought to light respecting infusoria and polythalamia fill us with the greatest admiration of the extent of organic life upon the globe. We have already seen that some of these animals are so minute that eight millions of them are found in a s.p.a.ce not larger than a mustard-seed; and yet they had skeletons of silex, lime, and iron; and, of course, these skeletons have been preserved; and, though of the smallest size, it requires not less than forty-one billions to make a single cubic inch; yet deposits of them, or of species not much larger, occur, several feet in thickness, and extending over several square miles.

Nay, the chalk of Northern Europe, and also of Western Asia, where it const.i.tutes most of Mount Lebanon, and extends southerly through Palestine into Arabia and Egypt, and also deposits in North and South America, thousands of miles in extent,--this rock, I say, is nearly half composed of microscopic sh.e.l.ls. The olite, also, contains them; and, indeed, infusorial remains occur in flint and opal; and, as instruments and observations are perfected, more and more of the solid rocks are found to have once const.i.tuted the framework of animals. It is hardly to be doubted that such was the fact with nearly all the limestone on the globe, occupying at least a seventh part of its surface. In fact, we seem fast coming to regard as sober truth the ancient adage, apparently so extravagant--_Omnis calx e vermibus; omne ferrum e vermibus; omnis silex e vermibus._ Indeed, it is the opinion of so competent a geologist as Dr.

Mantell that ”probably there is not an atom of the solid materials of the globe which has not pa.s.sed through the complex and wonderful laboratory of life.”--_Wond. of Geology_, vol. ii. p. 670.--What a vast field here opens before us to contemplate the far-reaching plans, the benevolence, and the wisdom of the Deity!

In the third place, geology shows us that the present system of organic life on the globe is but one link of a series, extending very far backward and infinitely forward.

Revelation describes only the existing species, leaving to science the task and the privilege to lift up the veil that hangs over the past, and to disclose other economies that have pa.s.sed away. How many of them have existed we do not certainly know. If, with Aga.s.siz, we characterize them by their predominant tribes, we might say that all the period previous to the new red sandstone const.i.tuted the reign of fishes; from thence to the chalk, the reign of reptiles; from thence to the drift, the reign of mammifera. But this is a less philosophical view than that of Deshayes, who finds five great groups of animals, specifically independent of one another. But who will attempt to fix the chronological limits of these systems? We can only say that they must have been exceedingly long, if we can place any dependence upon existing a.n.a.logies; and we know that each one of them is made up of numerous subdivisions, or minor groups, widely, though not entirely, different in composition and organic contents. We know that the more we examine the whole series, the deeper does our conviction become that its commencement runs back far, very far, into the depths of past eternity. We know, also, from the joint testimony of Scripture and geology, that another change is to pa.s.s over the world, to prepare it for inhabitants far more elevated than those now living upon it, and in possession of perfect holiness and perfect happiness. And it may be it will experience far greater changes, adapting it for higher and higher grades of being, through periods of duration to which we can a.s.sign no limits. O, what a vast chain of being is here spread out before the imagination, reaching immeasurably far into the depths of the eternity which is past, and into the eternity which is to come! What a field for the display of G.o.d's infinite perfections! What a vista does it open to us into the vast plans and purposes of Jehovah!

In the fourth place, geology reveals to us a curious series of improvements in the condition of worlds, as they pa.s.s through successive changes.

If the earth began its existence in the state of vapor, we can hardly imagine it in that state capable of sustaining any organic natures, formed upon the general type of those now existing. Nor, when the vapor was condensed into a molten globe, could such natures inhabit it, till a crust had formed over its surface, and the heat had been so reduced as not to decompose animals and plants. Even then, the natures placed upon it must have been of a peculiar and low type of organization, capable of enduring the high temperature and catastrophes which would destroy those of more delicate and complicated organization. But gradually did the temperature diminish, while aqueous and atmospheric agencies were acc.u.mulating a deeper and a richer soil, so that the next change of inhabitants would allow natures of a higher organization and a denser population to occupy the surface. Their remains, buried in the earth, would increase the quant.i.ty of carbonate of lime in a form available for the use of animals and plants; that is, lime would gradually be eliminated, by plants and animals, from its more concealed combinations in the crystalline rocks, and be converted into carbonates, sulphates, and humates. A larger amount of organic matter would also be converted into humus. Now, limestone soils are of all others most favorable to vegetation, when there is a sufficient supply of organic matter. Hence every successive change becomes more and more adapted for animals and plants, because the lime and the organic matter in a state favorable for their support have been increasing; and the present state of the surface is more favorable than any conditions which have preceded it, and accordingly it is peopled with more perfect and more numerous organic natures. Can we doubt but that, if another change pa.s.ses over the earth, this same great principle of progressive improvement will be manifested in the renovated world? I am not prepared to maintain, however, that this future change will be, like the past ones, an improvement as to soil and climate; for the change, as Scripture teaches, will be accomplished by fire; and so different will be the state of existence in the new earth, wherein dwelleth righteousness, that we cannot say how far the present system of nature will be introduced. But that it will be an improved condition, we can hardly doubt, if we infer any thing from the splendid figures by which it is described in the Bible, and from the character of those who are to be its denizens.

Some of the facts of modern astronomy impress us with the idea that this principle of progress may extend to other worlds. Some of these are in a gaseous state, some condensed into fiery liquid globes, some covered with a crust of solidified volcanic matter, and some surrounded by a liquid, like water. Do not these facts justify the supposition, that the changes which our earth has undergone are merely a single example of a great principle in G.o.d's government of the natural world? If so, it presents the divine wisdom in an interesting aspect. We see the Deity employing the same matter for different purposes. Instead of creating it for one single economy of organic beings, he seems to have made it the theatre for the display of his benevolence through successive periods; but at the same time not losing sight of the highest use he intended to make of it, by the introduction of rational and immortal natures upon it. Human wisdom would have p.r.o.nounced this impossible; but divine wisdom, prompted by divine benevolence, could accomplish it.

Finally, geology discloses to us chemical change as a great animating, controlling, and conservative principle of the material universe.

When Newton brought to light the principle of gravitation, and showed how it controls and keeps in harmonious movement the heavenly bodies, he developed the great mechanical power by which the universe is governed.

And this power was supposed for a long time to be superior to all others.

But geology has brought out a second great controlling and conservative agency,--the chemical power,--”the second right hand of the Creator,” as Dr. McCulloch expressively calls it. Suppose matter under the control of gravity, and let it be balanced by a centrifugal force. You have, indeed, harmonious motions among the celestial bodies, and, if no disturbing cause come in, you have endless motion. But until you introduce chemical agencies, every thing in the individual worlds would be compacted by gravity into one dead ma.s.s of matter, destined to no resurrection. But let chemical agencies leaven that ma.s.s, let affinity and cohesion commence their segregating processes, and constant motion and change would follow, with a thousand new and splendid forms. Especially when the Deity had infused the living principle into portions of that matter, and put chemistry, and her handmaid electricity, under the control of the vital power, would these worlds teem with animation, and countless exhibitions of beauty.

And in all known worlds, these chemical changes are at work unceasingly.

We know not whether those worlds are all inhabited, but we have evidence that all are undergoing the trans.m.u.tations of chemistry; not on their surface merely, but in their deep interior. The consequence is, universal change; change often upon a vast scale; change extending through thousands and millions of years, and through the entire ma.s.s of immense worlds. We have glanced, in these lectures, at the most important of those changes which this world has undergone, and we have seen it to be almost universal. We have found that the entire crust of the globe, many miles in thickness, and probably to its centre, has been dissolved by heat, and much of it also by water; that a large part of it, at least, has, by the same chemistry, been made to const.i.tute portions of the animal frame; that, even now, much of its interior is held in igneous solution, and that probably the time was when its entire ma.s.s was a molten, self-luminous world. Indeed, the conjecture is not without some foundation, which carries back this chemical action one step farther, and makes the world originally a diffused ma.s.s of nebula.

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 nebul; for here we probably find matter in its most chaotic and attenuated form, const.i.tuting self-luminous, diffused ma.s.ses 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 pa.s.sed. 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 pa.s.ses 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 circ.u.mstances, in a cycle; that is, the substance, after pa.s.sing 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 pa.s.sing, 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 a.s.sured, on the testimony of Scripture, that the next change of the earth will be from solid to liquid.