'Professor Müller and Mr. Straus have ably and amply illustrated the arrangements by which the eyes of insects and crustaceans are adapted to produce distinct vision, through the medium of a number of minute facets, or lenses, placed at the extremity of an equal number of conical tubes or microscopes; these amount sometimes, as in the butterfly, to the number of 35,000 facets in the two eyes, and in the dragon-fly to 14,000.'

The eyes of the fossils crustaceans present analogous examples of optical adaptation.

In the asaphus caudatus (a species of trilobite) each eye contains at least 400 nearly spherical lenses fixed in separate compartments on the surface of the cornea. The form of the general cornea is peculiarly adapted to the uses of an animal destined to live at the bottom of the water: to look downwards was as much impossible as it was unnecessary to a creature living at the bottom; but for horizontal vision in every direction the contrivance is complete. The form of each eye is nearly that of the frustum of a cone, incomplete on that side only which is directly opposite to the corresponding side of the other eye, and in which, if facets were present, their chief range would be towards each other across the head, where no vision was required. The exterior of each eye, like a circular bastion, ranges nearly round three-fourths of a circle, each commanding so much of the horizon, that where the distinct vision of one eye ceases, that of the other eye begins, so that in the horizontal direction the combined range of both eyes was panoramic.

If we compare this disposition of the eyes with that in the three cognate crustaceans, by which we have been illustrating the general structure of the trilobites, we find the same mechanism pervading them all, modified by peculiar adaptations to the state and habits of each.'

The Doctor adds beautifully and most ingeniously:

The results arising from these facts are not confined to animal physiology; they give information also regarding the condition of the ancient sea and ancient atmosphere, and the relations of both these media to light, at that remote period when the earliest marine animals were furnished with instruments of vision, in which the minute optical adaptations were the same that impart the perception of light to crustaceans now living at the bottom of the sea.

'With respect to the waters wherein the trilobites maintained their existence throughout the entire period of the transition formation, we conclude that they could not have been that imaginary turbid and compound chaotic fluid, from the precipitates of which some geologists have supposed the materials of the surface of the earth to be derived; because the structure of the eyes of these animals is such, that any kind of fluid in which they could have been efficient at the bottom, must have been pure and transparent enough to allow the passage of light to organs of vision, the nature of which is so fully disclosed by the state of perfection in which they are preserved.

• With

'With regard to the atmosphere also we infer, that had it differed materially from its actual condition, it might have so far affected the rays of light, that a corresponding difference from the eyes of existing crustaceans would have been found in the organs on which the impressions of such rays were then received.

Regarding light itself also, we learn, from the resemblance of these most ancient organizations to existing eyes, that the mutual relations of light to the eye, and of the eye to light, were the same at the time when crustaceans endowed with the faculty of vision were first placed at the bottom of the primeval seas, as at the present

moment.

'Thus we find among the earliest organic remains an optical instrument of most curious construction, adapted to produce vision of a peculiar kind in the then existing representatives of one great class in the articulated division of the animal kingdom. We do not find this instrument passing onwards, as it were, through a series of experimental changes, from more simple into more complex forms; it was created at the very first, in the fulness of perfect adaptation to the uses and condition of the class of creatures to which this kind of eye has ever been, and is still appropriate.

'If we should discover a microscope or telescope in the hand of an Egyptian mummy, or beneath the ruins of Herculaneum, it would be impossible to deny that a knowledge of the principles of optics existed in the mind by which such an instrument had been contrived. The same inference follows, but with cumulative force, when we see nearly four hundred microscopic lenses set side by side in the compound eye of a fossil trilobite; and the weight of the argument is multiplied a thousand-fold when we look to the infinite variety of adaptations by which similar instruments have been modified, through endless genera and species, from the long-lost trilobites of the transition strata, through the extinct crustaceans of the secondary and tertiary formations, and thence onwards throughout existing crustaceans, and the countless hosts of living insects.

It appears impossible to resist the conclusions as to unity of design in a common author, which are thus attested by such cumulative evidences of creative intelligence and power; both, as infinitely surpassing the most exalted faculties of the human mind, as the mechanisms of the natural world, when magnified by the highest microscopes, are found to transcend the most perfect productions of human art.'pp. 396-404.

We cannot take our leave of Dr. Buckland's fossil zoology without calling the attention of our readers to the chapter on fossil insects, and on the radiated animals and zoophytes. No one can have looked upon a slab of the entrochal marble of Derbyshire without being struck with the myriads of encrinites that must have swarmed in the ancient seas. The whole rock seems to be formed out of their remains. The plates, illustrative of this and every other part of the work, are full of interest, and are executed with

the

the greatest fidelity and care; and when we see the number and beauty of these illustrations, we cease to wonder that Dr. Buckland's should have been the last to make its appearance of all the 'Bridgewater Treatises.' * But though last, it will not, most assuredly, be considered the least, whether we look to the quantity of information contained in it, or the judgment with which that information has been applied to the case to be proved. Even as a repertorium paleontologicum, it will be eagerly sought for; and when we find that the subject is made an appeal to the better and nobler sentiments of our nature, in plain language, unincumbered as much as possible by the technical terms that deter too many from entering this most pleasant field of inquiry, we doubt not that Dr. Buckland will be the means of introducing many a saurian, many a trilobite, and many an encrinite to the acquaintance of those who would hardly have heard of such beings but for his excellent book.

We have still to speak of the flora of the fossil or mineral kingdom-a department of geology equally rich with that we have last touched upon in evidences of the uniformity of design which has ever pervaded the laws of organic life.

As yet the number of fossil plants that have been described does not much exceed five hundred species; yet small as this number is when compared to that of living plants, it appears to M. Adolphe Brongniart, who has devoted himself to this study, that by applying the principles which are found to influence the distribution of living plants, we can already establish some results of very great interest and importance in regard to the climates in which the vegetables grew, which are found in a fossil state in the different strata, and that they prove there was a marked difference in the climates of the different geological formations.

Dr. Buckland gives a summary of these results and a concise enumeration of the tribes of plants which have been found to be peculiar to each geological epoch, and we may (speaking in a general manner, for we have not room for a more detailed statement) give the following as the results arrived at.

1. The vegetable remains which are found in the oldest fossiliferous beds, such as the transition slates and limestones to the coal formations inclusive, consist of a few marine algæ, equisetacea of very large size, ferns in great numbers, lycopodeaceæ, a few palms, and some coniferæ.

2. In the lias and oolitic series, and to the chalk inclusive, are marine algæ, some equisetaceæ, ferns, a few lycopodeaceæ, coniferæ, liliaceæ, and cycadeæ.

We have heard, and can well believe, that Doctor Buckland's generous ardour has induced him to spend the whole of Lord Bridgewater's 10007. upon this magnificent appendix of engravings.

3. In

3. In the beds above the chalk we find algæ, a few ferns and equisetaceæ, palms, characeæ, liliacea, and many dicotyledonous plants.

In the first of these periods the very large size of some of the equisetaceæ, viz., those known by the name of calamites, which much exceed any of the living plants of this family, their great abundance, and the prodigious number of ferns, of which many have large fronds, are considered to indicate that the climate in which they grew was one even hotter than that of the equatorial regions of the present era.

The vegetable remains of the second period are for the most part of tribes analogous to those which grow in the equatorial regions at the present day. They are considered to indicate a high degree of temperature, though they do not exhibit so great a development as in the preceding period, and, therefore, the heat is supposed to have been less.

The fossil plants of the third period, or that of the beds above the chalk, approach much nearer to those of the present day, and contain many which indicate a temperate climate. In fact, we do not find in them any forms which are not analogous to some of the living tribes of plants.

In separating fossil vegetables into periods so decidedly distinct, it must be supposed that such is rather an account of the present state of our knowledge on the subject, than a statement of ultimate results. What we have said of the small number of plants yet known, will make us cautious in our conclusions, from such limited materials, although great interest must attach to the inquiry.

It would be interesting to find that the arguments as to climate, which may be furnished by the evidence derived from fossil plants, were confirmed by the character of the remains of animals found in the strata of the same period, and such, indeed, is supposed to be the case. It is, however, to be observed, that a great difficulty must attend this part of the inquiry, from the fact that the fossil organic remains are principally those of the inhabitants of the sea-which are not so well calculated to furnish decided conclusions as those of terrestrial animals. Besides this, we must allow that, as yet, we know but little of the circumstances under which vegetables have been preserved. The process by which silex has taken the place of wood, while yet the delicate structure has been preserved so as to show, when examined by the high powers of the microscope, the minute characteristic peculiarities which distinguish coniferous wood, is altogether inexplicable by our most profound chemists, and although we know, from what we observe in the formation of peat, that some kinds of

plants

plants when exposed to decay in wet places undergo a change, from which results an accumulation of bituminous and carbonaceous matter, yet we are far from being able to understand all the circumstances which have attended the formation of coal.

The quantity of fossil remains of plants, principally of ferns, which are accumulated in the coal measures, is immense. The impressions of ferns and other plants occur so closely placed together in shale or slaty clay over the coal, as frequently to cause the shale to fall and expose to view in the ceiling of the mine a most beautiful sight. One instance is thus described by Dr. Buckland

The most beautiful example I have ever witnessed is that of the coal mines of Bohemia. The most elaborate imitations of living foliage on the painted ceilings of Italian palaces bear no comparison with the beauteous profusion of extinct vegetable forms with which the galleries of these instructive coal mines are overhung. The roof is covered as with a canopy of gorgeous tapestry, enriched with festoons of most graceful foliage flung in wild irregular profusion over every portion of its surface. The effect is heightened by the contrast of the coal-black colour of these vegetables, with the light ground work of the rock to which they are attached. The spectator feels transported, as if by enchantment, into the forests of another world; he beholds trees, of form and character now unknown upon the surface of the earth, presented to his senses almost in the beauty and vigour of their primeval life; their scaly stems, and bending branches, with their delicate apparatus of foliage, are all spread forth before him, little impaired by the lapse of countless ages, and bearing faithful records of extinct systems of vegetation, which began and terminated in times of which these relics are the infallible historians. Such are the grand natural herbaria wherein these most ancient remains of the vegetable kingdom are preserved, in a state of integrity little short of their living perfection, under conditions of our planet which exist no more.'—p. 458.

We must here, however unwillingly, bring to a conclusion our quotations from this most instructive and interesting volume, of which every page is pregnant with facts inestimably precious to the natural theologian;-offering, as we unfeignedly do, our sincere acknowledgments to Dr. Buckland for the industry and research he has devoted to the performance of his task, and for the commanding eloquence with which he has called forth the very stocks and stones that have been buried for countless ages in the deep recesses of the earth, to proclaim the universal agency throughout all time of one all-directing, all-pervading mind, and to swell the chorus in which all creation hymns His praise,' and bears witness to His unlimited power, wisdom, and benevolence.

ART.