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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,) "xan reckon up all the varie ties that infinite wisdom can contrive, or show the impossi bility of organizations dissimilar to any within our experi ence? 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 may be 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 dogma tizing 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 wholhy 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.

the earlier deposites of sand into compact quartz rock, and beds of clay into c'ay slate, or other forms of primary slate. The rock which some authors hare called primary grauwacke, seems to be a mechanical dcposite of coarse sandstone, in which the form of the fragments has not been, so entirely obliterated by heat, as in the cose of compact quartz rock..

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 irery 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 1"

The same conclusion is stated by Cuvier, to be the result of his observations on geological phenomena: "Mais ce qui dtonne davantage encore, et ce qui n'est pas moins certain, e'est que la vie n'a pas toujours existe sur la globe, et qu'il est facile a 1'observateur de reconnoitre le point ou elle a commence" a deposer ses produits."—Cuvier, Ossemens Fossiles, Disc. Prelim. 1821, vol. i. p. ix..

CHAPTER VII.

Strata of the Transition Series.

Thus far we have been occupied with rocks, in which we trace chiefly the results of chemical and mechanical forces; but, as soon as we enter on the examination of strata of the Transition Series, the history of organic life becomes associated with that of mineral phenomena.*

The mineral character of the transition formations presents alternations of slate and shale, with slaty sandstone, limestone, and conglomerate rocks; the latter bearing evidence of the action of water in violent motion; the former showing, by their composition and structure, and by the organic remains which they frequently contain, that they were for the most part deposited in the form of mud and sand, at the bottom of the sea.

Here, therefore, we enter on a new and no less curious than important field of inquiry, and commence our examination of the relics of a former world, with a view to ascertain how far the fossil members of the animal and vegetable kingdoms may, or may not, be related to existing genera and species, as parts of one great system of creation, all bearing marks of derivation from a common author.f

* It is most convenient to include within the Transition scries, all kinds of stratified rocks, from the earliest slates, in which wo find the first traces of animal or vegetable remains, to the termination of the great coal formation. The animal remains in the more ancient portion of this scries, viz. the Grauwacke group, though nearly allied in genera, usually differ in species from those in its more recent portion, viz. the Carboniferous group.

tin Flale 1, I have attempted to convey same idea of the organic remains preserved in the several series of formations, by introducing over each, restored figures of a few of the most characteristic animals and vegetables that occupied the lands and waters, at the periods in which the; were deposited.

Beginning with the animal kingdom, we find the four great existing divisions of Vertebrata, Mollusca, Articulata, and Radiata, to have been coeval with the commencement of organic life upon our globe.*

No higher condition of Vertebrata has been yet discovered in the transition formation than that of fishes, whose history will be reserved for a subsequent chapter.

The Mollusca,f in the transition series, afford examples of several families, and many genera which seem at that time to have been universally diffused over all parts of the world. Some of these, (e. g. the Orthoceratite, Spirifer, and Producta) became extinct at an early period in the history of stratification, whilst other genera (as the Nautilus and Terebratula) have continued through all formations unto the present hour.

The earliest examples of Articulated animals are those afforded by the extinct family of Trilobites, (see Plates 45 and 46) to the history of which we shall devote peculiar consideration under the head of Organic Remains. Although nearly fifty species of these Trilobites occur in strata of the transition period, they appear to have become extinct before the commencement of the secondary series.

* " It has not been found necessary, in discussing the history of fossil plants and animals, to constitute a single new class; they all fall naturally into the same great sections as the existing forms.—Wo are warranted in concluding that the older organic creations were formed upon the same general plan as at present. They cannot, therefore, be correctly described as entirely different systems of nature, but should rather be viewed as corresponding systems, composed of different details. The difference of these details arises mostly from minute specific distinctions; but sometimes, especially among terrestrial plants, certain Crustacea, and reptiles, the differences arc of a more general nature, and it is not possible to refer the fossil tribes to any known recent genus, or even family. Thus we find the problem of the resemblance of recent and fossil organic beings to resolve itself into a general analogy of system, frequent agreement in important points, but almost universal distinction of minute organization."—Phillips's Guide to Geology, p. 61-63, 1834.

t In this great division, Cuvier includes a vast number of animals having soft bodies, without any articulated skeleton or spinal marrow, such as the Cuttle-fish, and the inhabitants of univalve and bivalve •hells.

The Radiated Animals are among the most frequent organic remains in the transition strata; they present numerous forms of great beauty, from which I shall select the family of Crinoidea, or lily-shaped animals allied to Star-fish, for peculiar consideration in a future chapter. (See PI. 47, Figs. 5, 6, 7.) Fossil corallines also abound among the radiata of this period, and show that this family had entered thus early upon the important geological functions of adding their calcarious habitations to the solid materials of the strata of the globe. Their history will also be considered in another chapter.

Remains of Vegetables in the Transition Series.

Some idea may be formed of the vegetation which prevailed during the deposition of the upper strata of the transition series, from the figures represented in our first plate (Fig. 1 to 13.) In the interior regions of this series, plants are few in number, and principally marine;* but in its superior regions, the remains of land plants are accumulated in prodigious quantities, and preserved in a state which gives them a high and two-fold importance; first, as illustrating the history of the earliest vegetation that appeared upon our planet, and the state of climate and geological changes which then prevailed :f secondly, as affecting, in no small degree, the actual condition of the human race.

* M. A. Brongniart mentions the occurrence of four species offucoids in the transition strata of Sweden and Quebec; and Dr. Harlan has described another species found in the Alleghany Mountains.

f The nature of these vegetables, and their relations to existing species, will be considered in a future chapter. .

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