Scarcely less conspicuous than the Sigillaria, the Fern, and the Calamite, is the Lepidodendron or Scaly Tree, one of the most curious and interesting among the plants of the Coal-bearing period. Like the Sigillaria and the Calamite, it has been, and still is, a puzzle to the student of Botany. But it needs not the eye of science to see that it is unmistakably a stately forest tree, shut up in the Crust of the Earth, encased in a solid framework of indurated Shale, or Sandstone, or Coal, as the case may be, and overlaid with massive strata of rock hundreds of feet in thickness. Such a specimen as that represented in our woodcut was laid bare some years ago in Yarrow Colliery, near Newcastle.
Fig. 26 Lepidodendron Elegans. Portion of Stem and branches; Coal Mine, Newcastle.
In the same neighborhood was found a portion of the stem and branches of another variety, Lepidodendron Elegans, which will enable the reader to form a more complete idea of the appearance presented by this ancient tree as it stood in its primeval forest.
An unusually favorable illustration of our present subject may be seen at the colliery of Treuil, in France, not far from the city of Lyons. The beds of Coal are overlaid by a kind of slaty sandstone, ten feet thick; and this sandstone is traversed by the vertical stems of enormous petrified plants, chiefly Calamites. Here, then, to all appearance, we have an ancient forest enveloped in sandstone. We must suppose that the forest was submerged while the trees were still erect; that in this condition it received the sedimentary deposits carried down by the current of some great river; and finally, that these deposits were, in the course of ages, compacted into sandstone by a process already explained. It would seem that after the sandstone had been partially, at least, consolidated, it was subjected to a sliding movement here and there, by which the continuity of the stems was broken; the upper part being pushed on one side, as shown in our Figure.
Fig. 27.—Section of a Coal sandstone at Treuil, near Lyons. Showing the erect position of Fossil Trees. (Alex. Brongniart.)
It is time we should bring to a close our survey, meagre and imperfect as it is, of Fossil Remains. Those who desire to pursue the inquiry for themselves will easily find an opportunity of doing so. There are few, we should suppose, who may not, occasionally, have access to one or other of those splendid Museums of Geology, which have been set up in all the great towns of Europe. And the still more extensive cabinets of Nature’s Museum, spread out beneath our feet, are within the reach of all.
But even the scanty facts which have been set forth faithfully, we trust, though perhaps feebly, in these pages, are sufficient to satisfy all reasonable minds that the bones, the skeletons, the trunks and branches of trees, which have been exhumed from the Stratified Rocks are really the remains of Organic Life that once flourished on the earth, or in the waters of the ancient seas. Obvious, however, as this fact must appear to all who have fully realized the character and appearance of Fossil Remains, it has been often vigorously assailed and vehemently denounced. In the early days of Geology phenomena of this kind were ascribed, not uncommonly, to the “plastic power of Nature,” or to the influence of the stars. Such notions, however, meet with little support among modern writers. They were nothing more than wild fancies, without any foundation either in the evidence of facts or in the analogy of Nature. The “plastic power of Nature” was a phrase that sounded well, perhaps, in the ears of unreflecting people; but no one ever undertook to show that Nature really possesses that “plastic power” which was so readily imputed to her. No one ever undertook to show that it is the way of Nature to make the stems, and branches, and leaves of trees, without the previous process of vegetation; or to make bones and skeletons which have never been invested with the ordinary appendages of flesh and blood. Yet surely this is a theory that requires proof; for all our experience of the laws of Nature points directly to the opposite conclusion. And as for the influence of the stars, we may be content to adopt the language of the celebrated painter Leonardo da Vinci:—“They tell us that these shells were formed in the hills by the influence of the stars; but I ask where in the hills are the stars now forming shells of distinct ages and species? and how can the stars explain the origin of gravel occurring at different heights and composed of pebbles rounded as if by the action of running water? or in what manner can such a cause account for the petrifaction in the same places of various leaves, sea-weeds, and marine crabs?”[81]
In modern times the form of objection has been somewhat changed. We are told by some writers that, when we seek to explain the existence of Fossil Remains by the action of natural laws, we seem to forget the Omnipotence of God. They urge upon us, with much solemnity, that He could have made bones, and shells, and skeletons, and petrified wood, though there had been no living animal to which these bones belonged, and no living tree that had been changed into stone. And if He made them, might He not disperse them up and down through His creation, on the lofty mountains, in the hidden valleys, and in the profound depths of the sea? and buried them in limestone rocks and in the soft clay? and arranged them in groups, or scattered them in wild confusion as He best pleased?