The fishes of the two periods are equally striking in their contrasts; the two orders of Ganoids and Placoids are common to both, while the Ctenoids and Cycloids appear for the first time in the history of our planet, and which were afterward to contribute so largely to the sustenance and comforts of man. The Reptilians show a declension in the latter period in numbers, with the introduction, however, of four new genera—one of which (the Iguanodon Mantelli), is also found in the wealden.

The Cimoliornis Diomedeus, described by Professor Owen, is the only specimen of the order Aves or bird-tribe that as yet appears over this waste of waters. The term cimoliornis means simply the chalk-bird, and is allied, in some of its osseous processes, to the albatross, but also differs in too many points to be regarded as the ancestor of that courageous storm-braving animal. The claims of this fossil, indeed, to its true place in the system, have not yet been fully established. “Of the few actually fossilized remains of birds,” says Professor Owen, “that have been discovered in England, the most complete and characteristic are those from the London clay. Some fragmentary Ornitholites have been discovered in the older pliocene crag, and in the newer pliocene fresh water deposits and bone caves. Extremely scanty have hitherto been the recognizable remains of birds from the chalk formations. The fossil from the wealden, which I formerly believed, with Cuvier and Dr. Mantell, to belong to a wading bird, I have since adduced reasons for referring to the extinct genus of flying reptiles called Pterodactyle.” The fossil bones of the Cimoliornis were obtained by the Earl of Enniskillen from the chalk beds near Maidstone, and resemble the humerus of the albatross in form, proportions and size; there are no distinct traces of the attachments of the quill-feathers in any of the fragments; but in other points there are analogies to the osseous structure of birds; and there are bones so gigantic as will assign them a place, if the proofs are completed, among the enormous foot-print class of the permian age, and go almost to realize the fabulous “roc” of the Arabian romance.

Our attention in this group of deposits, however, is riveted more by the little than the great—by the microscopic than the gigantic forms of life. It is astounding, indeed, to contemplate the myriads of creatures which swarmed in the seas during this period. A fragment of chalk, the size of a garden pea, contains thousands of perfect shells; these shells inclose still, in many instances, the pulpy animal matter; and consist of a series of distinct well-defined chambers. In a cubic inch of the rock it is calculated that there are upward of a million of infusorial animalcules. Yet their orders are determined, their genera fixed, their very species are described, so perfect is the structure, and so thoroughly preserved all the parts of their minute shelly coverlets. The microscope has restored, under the action of certain dilute acids, the contour and shape of entire hosts of these creatures. Some specimens, so positively can it speak of them, appear to consist of tubes placed edgewise,—one projecting sometimes beyond another. Others are seen to possess a series of tubular organs placed parallel, and disposed in long lines of fragile reticulated riband. Some are oblong figures. Others are complicated, exhibiting numerous projecting processes, and of every variety of shape. Some resemble the shell of the nautilus; others are still detected with the skin adhering to the skeleton; while in the stomachs and digestive sacs of others the more minute infusoria, which the diminutive monster had swallowed, are made palpable to the sight.

All this may be called trifling, a misapplication of talent, a waste of ingenuity. What terms too grand to describe the lofty speculations of the astronomer, who points his telescope to some dark point in the blue sky, and descries in its infinite depths a cluster of closely aggregated shining particles, minute as the motes in the sunbeam, and hails it as the discovery of a new system of worlds. He cannot count them, for they are innumerable. He cannot measure them, for they have no dimensions. He cannot tell their relations, nor describe their orbits of motion, for a sparkling heap of star-dust is all that flits before the reflector. But the boundaries of knowledge are enlarged, and though man nor any of the arts may ever be benefited thereby, the fortunate discoverer will have his name inscribed in that distant region of the universe, and transmitted from generation to generation with increasing luster.

The discoveries of the geologist may be inferior in grandeur, but are they practically less illustrative in their bearings on existing arrangements? He sees the past in the present, the near and the distant in time brought together. A charm is thereby thrown over studies and speculations which would otherwise be useless. Thus, in the mineral structures resulting from the agencies of these invisible organic bodies, the mind is struck with the resemblance to similar processes that may be now going forward in the ocean: it sees in the discoloration of the waves, as the voyager steers his vessel over the main, a light by which to decipher the story of an age; and, while no voice issues from the countless myriads of animals which thicken the waters, rocks are elaborating and depositions made that will yet be raised into islands or continents. “On the coast of Chili, a few leagues north of Conception, the Beagle,” says Dr. Darwin, “one day passed through great bands of muddy water, which, when taken up in a glass, was found to be slightly stained as if by red dust, and after leaving it for some time quiet, a cloud collected at the bottom. With a lens of one-fourth of an inch focal distance, small hyaline points could be seen, darting about with great rapidity, and frequently exploding. Examined with a much higher power, their shape was found to be oval, and contracted by a ring round the middle, from which line curved little setæ proceeded on all sides; and these were the organs of motion. The animals move with the narrow apex forward, by the aid of their vibratory cilia, and generally by rapid starts. Their numbers were infinite, and in one day we passed through two spaces of water thus stained, one of which alone must have extended over several square miles. The color of the water, as seen at some distance, was like that of a river which has flowed through a red clay district; but under the shade of the vessel’s side, it was quite as dark as chocolate.”

These are the foundation-builders of future islands, of the very color and size, it may be, as those which piled up these masses of the brick-red chalk. In an ounce of sea-sand, from three to four millions of these minute bodies have been enumerated. Twenty-two thousand can be placed side by side on a linear inch of surface. One single individual, in the course of a month in summer, will produce as many as 800,000,000. In a globule of water, a cubic inch contains more inhabitants than are now existing of the human family on the face of the globe. The skeletons of the animalcula are transported through the air in the form of a fine impalpable dust, covering the decks of vessels, and darkening the atmosphere many hundred miles distant at sea. The eye can trace nothing of structure—not even of granular form—and while clothes, rigging, and every crevice is filled and discolored with the organic nebulæ, it is not until the highest microscopic powers are applied, that it becomes resolvable and demonstrated to be a system of living creatures, moving through space, and fulfilling their destiny!

The views of nature thus opened up are boundless and infinite, in either terms of the scale, ascending or descending. The immensity of things on the one side, and their minuteness on the other, carry them equally beyond the reach of direct observation, and the intervention of means must in both cases be provided, ere they can become the subjects of human perception and examination. But what is it to me, some will reason, if there lie within the depths of space myriads of rolling worlds, when I see them not, and whose revolutions can in no way affect my condition on earth? These rocks around are but obstacles in my way, or stones for which I have no regard, as I can apply them to no useful purpose. I know that every blade of grass, every leaf in the forest, every drop of water, every grain of sand, teem with living creatures. And, in the air I breathe, systems more, beyond the ken of human view “both when we wake and when we sleep,” revel in the irresponsible enjoyment of sentient existence. Science, viewed in this light, and calculated upon the rule of mere statistical enumeration, may be reckoned as utterly valueless, and knowledge as but a term for Materialism.

But neither astronomy nor geology will permit our speculations thus to terminate. A principle of causation is involved in both, and to trace this through a chain of sequences and effects, whether in the great or little, in the remote or near, is the one grand aim of philosophy. If I can perceive no bounds to the vast expanse in which natural causes operate, and can fix no border or termination of the universe; and if I am equally at a loss to discern things in their elements, and to discover the limits which terminate the subdivisions of organic matter, my inquiries will not here cease. The mind will not be satisfied so to close and to shut up the thesis propounded. I am compelled to advance onward, even as the objects recede from the view, or expand in magnitude beyond the grasp of comprehension. The soul is filled with the idea of immensity, as it familiarizes itself to the thought of the highest mountains of the earth being but specks on its surface—the terraqueous globe as an atom compared with the sun—the sun itself dwindling to a star from some point in the distant fields of space—and even all the systems that sparkle in the clearest sky only as faint streaks of light, or not discernible even for millions of years after their creation, in the systems that replenish and shine in the still remoter void. Speculations, lofty as these, do leave something behind—something nobler than arithmetical calculation—and knowledge becomes spiritualized by them.