Geology and Mineralogy considered with reference to Natural Theology/Chapter 6
CHAPTER VI.
Primary Stratified Rocks.
In the summary we have given of the leading phenomena of unstratified and volcanic rocks, we have unavoidably been led into theoretical speculations, and have seen that the most probable explanation of these phenomena is found in the hypothesis of the original fluidity of the entire materials of the earth, caused by the presence of intense heat. From this fluid mass of metals, and metalloid bases of the earths, and alkalies, the first granitic crust appears to have been formed, by oxidation of these bases; and subsequently broken into fragments, disposed at unequal, levels above and below the surface of the first formed seas.
Wherever solid matter rose above the water, it became
exposed to destruction by atmospheric agents; by rains,
torrents, and inundations; at that time probably acting with
intense violence, and washing down and spreading forth, in
the form of mud and sand and gravel, upon the bottom of the
then existing seas, the materials of primary stratified rocks,
which, by subsequent exposure to various degrees of subterranean
heat, became converted into beds of gneiss, and
mica slate, and hornblende slate, and clay slate. In the detritus thus swept from the earliest lands into the most
ancient seas, we view the commencement of that enormous
series of derivative strata which, by long-continued repetition
of similar processes, have been accumulated to a
thickness of many miles.[1]
The total, absence of organic remains throughout those lowest portions of these strata, which have been called primary, is a fact consistent with the hypothesis which forms part of the theory of gradual refrigeration; viz. that the waters of the first formed oceans were too much heated to have been habitable by any kind of organic beings.[2]
In these most ancient conditions, both of land and water Geology refers us to a state of things incompatible with the existence of animal and vegetable life; and thus on the evidence of natural phenomena, establishes the important fact that we find a starting point, on this side of which all forms, both of animal and vegetable beings, must have had a beginning.
As, in the consideration of other strata, we find abundant evidence in the presence of organic remains, in proof of the exercise of creative power, and wisdom, and goodness, attending the progress of life, through all its stages of advancement upon the surface of the globe; so, from the absence of organic remains in the primary strata, we may derive an important argument, showing that there was a point of time in the history of our planet, (which no other researches but those of geology can possibly approach,) antecedent to the beginning of either animal or vegetable life. This conclusion is the more important, because it has been the refuge of some speculative philosophers to refer the origin of existing organizations, either to an eternal succession of the same species, or to the formation of more recent from more ancient species, by successive developments, without the interposition of direct and repeated acts of creation; and thus to deny the existence of any first term, in the infinite series of successions which this hypothesis assumes. Against this theory, no decisive evidence has been accessible, until the modern discoveries of geology had established two conclusions of the highest value in relation to this long disputed question: the first proving, that existing species have had a beginning; and this at a period comparatively recent in the physical history of our globe: the second showing that they were preceded by several other systems of animal and vegetable life, respecting each of which it may no less be proved, that there was a time when their existence had not commenced; and that to these more ancient systems also, the doctrine of eternal succession, both retrospective and prospective, is equally inapplicable.[3]
Having this evidence both of the beginning and end of
several systems of organic life, each affording internal proof
of the repeated exercise of creative design, and wisdom,
and power, we are at length conducted back to a period anterior to the earliest of these systems; a period in which
we find a series of primary strata, wholly destitute of organic
remains; and from this circumstance, we infer their
deposition to have preceded the commencement of organic
life. Those who contend that life may have existed during
the formation of the primary strata, and the animal remains
have been obliterated by the effects of heat, on strata nearest
to the granite, do but remove to one point further backwards
the first term of the finite series of organic beings;
and there still remains beyond this point an antecedent period,
in which a state of total fusion pervaded the entire
materials of the fundamental granite; and one universal
mass of incandescent elements, wholly incompatible with
any condition of life, which can be shown to have ever existed,
formed the entire substance of the globe.[4]
It may be said we have no right to deny the possible existence of life and organization upon the surface, or in the interior of our planet, under a state of igneous fusion, "Who," says the ingenious and speculative Tucker, (Light of Nature, book iii. chap. 10), "can reckon up all the varieties that infinite wisdom can contrive, or show the impossibility of organizations dissimilar to any within our experience? Who knows what cavities lie within the earth, or what living creatures they may contain, endued with senses unknown to us, to whom the streams of magnetism may serve instead of light, and those of electricity affect them as sensibly as sounds and odours affect us? Why should we pronounce it impossible that there should be bodies formed to endure the burning sun, to whom fire maybe the natural element, whose bones and muscles are composed of fixed earth, their blood and juices of molten metals? Or others made to live in the frozen regions of Saturn, having their circulation carried on by fluids more subtle than the highest rectified spirits raised by chemistry?"
It is not for us to meet questions of this kind by dogmatising as to possible existences, or to presume to speculate on the bounds which creative Power may have been pleased to impose on its own operations. We can only assert, that as the laws that now regulate the movements and properties of all the material elements, can be shown to have undergone no change since matter was first created upon our planet; no forms of organization such as now exist, or such as Geology shows to have existed, during any stages of the gradual formation of the earth, could have supported, for an instant, the state of, fusion here supposed.
We therefore conclude, that whatever beings of wholly different natures and properties may be imagined to be within the range of possible existences, not one of all the living or fossil species of animals or vegetables, could ever have endured the temperature. of an incandescent planet. All these species must therefore have had a beginning, posterior to the state of universal fusion which Geology points out.
I know not how I can better sum up the conclusion of this argument, than in the words of my Inaugural Lecture, (Oxford, 1819, p. 20).
"The consideration of the evidences afforded by geological phenomena may enable us to lay more securely the very foundations of natural theology, inasmuch as they clearly point out to us a period antecedent to the habitable state of the earth, and consequently antecedent to the existence of its inhabitants. When our minds become thus familiarized with the idea of a beginning and first creation of the beings we see around us, the proofs of design, which the structure of those beings affords, carry with them a more forcible conviction of an intelligent Creator, and the hypothesis of an eternal succession of causes, is thus at once removed. We argue thus: it is demonstrable from Geology that there was a period when no organic beings had existence; these organic beings must therefore have had a beginning subsequently to this period; and where is that beginning to be found but in the will and fiat of an intelligent and all-wise Creator?"
The same conclusion is stated by Cuvier, to be the result of his observations on geological phenomena: “Mais ce qui étonne davantage encore, et ce qui n'est pas moins certain, c'est que la vie n'a pas toujours existé sur le globe, et qu'il est facile à l'observateur de reconnôitre le point où elle a commencé à déposer ses produits."—Cuvier, Ossemens Fossiles, Disc. Prelim. 1821, vol. i. p. ix.
- ↑ Mr. Conybeare (in his admirable Report on Geology to the British Association for the advancement of Science, 1832, p. 367) shows, that many of the most important principles of the igneous theory, which has been almost demonstrated by modern discoveries, had been anticipated by the universal Leibnitz. "In the fourth section of his Protogæa, Leibnitz presents us with a masterly sketch of his general views, and, perhaps, even in the present day, it would be difficult to lay down more clearly the fundamental positions which must be necessarily common to every theory, attributing geological phenomena in great measure to central igneous agency. He attributes the primary and fundamental rocks to the refrigeration of the crust of this volcanic nucleus; an assumption which well accords with the now almost universally admitted igneous origin of the fundamental granite, and with the structure of the primitive slates, for the insensible gradation of these formations appears to prove that gneiss must have undergone in a greater, and mica slate in a less degree the same action of which the maximum intensity produced granite.
"The dislocations and deranged position of the strata he attributes to the breaking in of vast vaults, ~which the vesicular and cavernous structure assumed by masses, during their refrigeration from a state of fusion must necessarily have occasioned in the crust, thus cooling down and consolidated. He assigns the weight of the materials and the eruption of elastic vapours as the concurrent causes of these disruptions; to which we should perhaps add, that the oscillations of the surface of the still fluid nucleus may, independently of any such cavities, have readily shattered into fragments the refrigerated portion of the crust a especially, as at this early period, it must have been necessarily very thin, and resembling chiefly the scoriæ floating on a surface of lava just beginning to cool. He justly adds, that these disruptions of the crust must, from the disturbances communicated to the incumbent waters, have been necessarily attended with diluvial action on the largest scale. When these waters had subsequently, in the intervals of quiesce nee between these convulsions, deposited the materials first acquired by their force of attrition, these sediments formed, by their consolidation, various stony and earthy strata. Thus, he observes, we may recognise a double origin of the rocky masses, the one by refrigeration from igneous fusion, (which, as we have seen, he considered principally to be assignable to the primary and fundamental rocks,) the other by concretion from aqueous solution. We have here distinctly stated the great basis of every scientific classification of rock formations. By the repetition of similar causes (i. e. disruption of the crust and consequent inundations) frequent alternations of new strata were produced, until at length these causes having been reduced to a condition of quiescent equilibrium, a, more permanent state of things emerged. Have we not here clearly indicated the data on which, what may be termed the, chronological investigation of the series of geological phenomena, must ever proceed?"
- ↑ So long as the temperature of the earth continued intensely high, water could have existed only in the state of steam or vapour, floating in the atmosphere around the incandescent surface.
- ↑ Mr. Lyell, in the four first chapters of the second volume of his Principles of Geology, has very ably and candidly examined the arguments that have been advanced in support of the doctrine of transmutation of species, and arrives at the conclusion,—"that species have a real existence in nature, and that each was endowed, at the time of its creation, with the attributes and organization by which it is now distinguished."
Mr. De la Beche also says (Geological Researches, 1834, p. 239, 1st. edit. 8vo.) "There can be no doubt that many plants can adapt themselves to altered conditions, and many animals accommodate themselves to different climates; but when we view the subject generally, and allow full importance to numerous exceptions, terrestrial plants and animals seem intended to (ill the situations they occupy, as these were fitted for them; they appear created as the conditions arose, the latter not causing a modification in previously existing forms productive of new species."
- ↑ In adopting the hypothesis that the primary stratified rocks have been altered and indurated by subjacent heat, it should be understood, that although heat is in this case referred to as one cause of the consolidation of strata, there are other causes which have operated largely to consolidate the secondary and tertiary strata, which are placed at a distance above rocks of igneous origin. Although many kinds of limestone may have been in certain cases converted to crystalline marble, by the action of heat under high pressure, there is no need for appealing to such agency to explain the consolidation of ordinary strata of carbonate of lime; beds of secondary and tertiary sandstone have often a calcareous cement, which may have been precipitated from water, like the substance of stalactites and ordinary limestone. When their cement is siliceous, it may also have been supplied by some humid process, analogous to that by which the siliceous matter of chalcedony and of quartz is either suspended or dissolved in nature; a process, the existence of which we cannot deny, although it has yet baffled all the art of chemistry to imitate it. The beds of clay which alternate with limestone, and sand, or sandstone, in secondary and tertiary formations, show no indications of the action of heat; having undergone no greater consolidation than may be referred to pressure, or to the admixture of certain proportions of carbonate of lime, where the clay beds pass into marl and marlstone. Beds of soft unconsolidated clay, or of loose unconsolidated sand, are very rarely if ever found amongst any of the primary strata, or in the lower regions of the transition formation; the effects of heat appear to have converted the earlier deposites of sand into compact quartz rock, and beds of clay into clay slate, or other forms of primary slate. The rock which some authors have called primary grauwacke, seems to be a mechanical deposite of coarse sandstone, in which the form of the fragments has not been so entirely obliterated by heat, as in the case of compact quartz rock.