gravitation. If, then, the science we are considering can be shown to afford analogous presumptive proofs regarding others, the argument would be interesting and important enough to deserve more extended notice than Dr. Buckland has bestowed on it. One of the most striking, because novel, facts mentioned in his work is the discovery of the eyes of extinct crustacea, which by their resemblance to those organs in living races, indicate the identity of the light of the primæval world with that element which now pervades space. Geology offers numberless other conclusions of an analagous kind with respect to inorganic creation : fossil plants, by their similarity in structure and developement to existing species, may be fairly concluded to have been nourished by water and air of the same chemical, as well as mechanical, properties as that which fills our seas, rivers, and lakes, and descends from the clouds in rain and dew. The arrangement of the component ingredients of conglomerates and breccias reciprocally establish the permanence of their specific gravity, and of the hydrostatic pressure of the water which floated them to their present sites; and as the gravitation has been shown to be constant, the other laws, chemical and mechanical, may be inferred to be so likewise. These presumptive proofs being established, the nature of the evidence on which geological deductions rest becomes of more weight.

Having fulfilled the least agreeable part of our duty, we may now indulge in the pleasure of pointing out a few of the many beautiful illustrations and philosophical deductions, which the reader will find in Dr. Buckland's work, expressed with that force and grace which make both his writings and lectures so popular. We would especially call attention to the following passage, as inculcating a principle in which man is but too much deficient-humility, and which ought to have double force as coming from a philosopher and a divine.

"I would in this, as in all other cases, be unwilling to press the theory of relation to the human race so far, as to contend that all the great geological phenomena we have been considering were conducted solely and exclusively with a view to the benefit of man. We may rather count the advantages he derives from them as incidental and residuary consequences; which, although they may not have formed the exclusive object of creation, were all foreseen and comprehended in the plans of the great Architect of the globe, which in His appointed time was destined to become the scene of human habitation.

"With respect to the animal kingdom, we acknowledge with gratitude that among the higher classes there is a certain number of living species which are indispensable to the supply of human food and raiment, and to the aid of civilized man in his various labours and occupations; and that these are endowed with dispositions and faculties which adapt them in a peculiar degree for domestication: but their number bears an extremely small proportion to the total amount of existing species; and with regard to the lower classes of animals, there are but very few, among their almost countless multitudes, that minister either to the wants or luxuries of the human race. Even could it be proved, that all existing species are serviceable to man, no such inference could be drawn with respect to those numerous extinct animals which geology shows to have ceased to live long before our race appeared upon the earth. It is surely more consistent

with sound philosophy, and with all the information that is vouchsafed to us respecting the attributes of the Deity, to consider each animal as having been created, first for its own sake, to receive its portion of that enjoyment which the Universal Parent is pleased to impart to each creature that has life; and secondly, to bear its share in the maintenance of the general system of co-ordinate relations, whereby all families of living beings are reciprocally subservient to the use and benefit of one another. Under this head only can we include their relations to man, forming, as he does, but a small, although it be the most noble and exalted part, of that vast system of universal life with which it hath pleased the Creator to animate the surface of the globe." (Vol. i. p. 101.)

One very striking and satisfactory result of the investigations of extinct races of animals, is the discovery of those links in the great chain of organized beings which were wanting to its continuity. We possessed long detached segments of this chain, but we searched in vain among living genera for these connecting portions; geology is now come to the aid of natural history, and from the numerous contributions it has already furnished, we may hope it will in time enable us to complete what is still deficient, and establish the truth of the dictum, Natura non facit saltus.

The order Pachydermata, as our readers are aware, was particularly deficient in genera to constitute intermediate links between such remotely allied animals as the horse, hog, rhinoceros, hippopotamus, tapir, and elephant; the numerous extinct genera of this order, already discovered, fill up these hiatuses.

"This numerical preponderance of pachydermata, among the earliest fossil mammalia, beyond the proportion they bear among existing quadrupeds, is a remarkable fact, much insisted on by Cuvier; because it supplies, from the relics of a former world, many intermediate forms which do not occur in the present distribution of that important order. As the living genera of Pachydermata are more widely separated from one another than those of any other order of mammalia, it is important to fill these vacant intervals with the fossil genera of a former state of the earth; thus supplying links that appeared deficient in the grand continuous chain which connects all past and present forms of organic life, as parts of one great system of creation." (Vol. i. p. 88.)

Besides filling up the gaps in the order, some of the fossil genera of Pachydermata form points of connexion between that and the orders. Ruminantia and Edentata, and one, the Dinotherium, cannot properly be assigned to any one of these orders exclusively, on account of the singular anomalous formation of its lower jaw, terminating in two tusks projecting downwards, like those from the upper jaw of a walrus.

Most of those species which belong to extinct genera agree in some points with several widely dissimilar living species, which are by this means brought into closer union,—and not only orders, but even classes, are placed in unexpected affinity by means of these inhabitants of a primæval world.

The Saurian Reptiles and Fishes are connected by the gigantic Ichthyosaurians; but a still more marvellous example of the union of characters of remote classes is presented by that mystery, the Pterodactyli which were intermediate to the Saurians and the Cheiroptera.

The wonderful and imposing fact of the successive creation and extinction of species is brought before the mind with peculiar force, when we absolutely find the relics of an extinct order still lingering, as it were, on the globe, and perhaps destined at no distant period to die out like their ancestral family. We may fancy the Polypteri of the African, and the Lepidostei of the American rivers, viewing with indifference a creation in which they feel themselves out of their places, and recalling those periods of Ichthyal grandeur, when the aristocratic supremacy of Megalichthys was acknowledged throughout the deep, and the lordly Sauroids were legitimate monarchs by the strength of their teeth. We doubt not the Bichir of the Nile often views the crocodile with envy, and repines, like other creatures, at the partiality of Providence, which has shown such favour to a modern branch of their noble stock, while the true representative is struggling with adversity, and only holds the precarious tenure of its existence by the compassionate forbearance of such plebeian upstarts.

It would be a curious and interesting object of inquiry to find whether, in the present state of our knowledge of the relations between organic life and the inanimate world, we possess any data for venturing at a guess what existing species among the higher orders will next become extinct, in obedience to this law of succession, which seems to form a part of the code of Creation; and to trace the probable effect of human agency in modifying the natural progress of this event,-whether there exists a generic power of continuance in certain races which will effectually counteract the unremitting persecution and war of extermination carried on against them, in consequence either of the real wants, the cupidity, or the cruelty of mankind. It is most probable, however, that we have but little influence beyond keeping down the numbers of certain genera or races, and that it is only because the accurate adjustment between the organic functions and the external world is deranged, that a race of animals becomes extinct. If it be true that in the Dodo we have an instance of a genus becoming extinct since the creation of the human race, how much must we regret that we possess such meagre information of the circumstances.

The incorrectness of the conclusion, which had been hastily adopted from insufficient geological researches, that there had been a progressive advance from the simpler to the more complicated forms of organic structure, has been established by different and conclusive arguments, suggested by more accurate knowledge. The avowal, that we know not what class of animals are to be considered as a standard for estimating relative simplicity or complexity of structure, is extorted from us by Ehrenberg's investigations of Infusoriæ; while the discovery of types of the higher classes, as we term them, in the more ancient strata, prove that at all periods there has existed a proportional variety among cotemporary species, as at present. In the following passage we have laid open to us a new source of error to be guarded against, in our attempts to interpret the state of organic creation in remote eras.

"The values to be attached to numerical proportions of fossil plants, in estimating the entire condition of the Flora of these early periods, has been diminished by the result of a recent interesting experiment made by

Professor Lindley, on the durability of plants immersed in water. Having immersed in a tank of fresh water, during more than two years, one hundred and seventy-seven species of plants, including representatives of all those which are either constantly present in the coal-formations, or universally absent, he found,

1. That the leaves and bark of most dicotyledonous plants are wholly decomposed in two years, and that of those which do resist it the greater part are Coniferæ and Cycadeæ.

"2. That Monocotyledons are more capable of resisting the action of water, particularly palms and scitamineous plants; but that grasses and sedges perish.

“3. That fungi, mosses, and all the lowest forms of vegetation, disappear.

"4. That ferns have a great power of resisting water, if gathered in a green state, not one of those submitted to the experiment having disappeared; but that their fructification perished.

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Although the results of this experiment, in some degree, invalidate the certainty of our knowledge of the entire Flora of each of the consecutive periods of geological history, it does not affect our information as to the number of the enduring plants which have contributed to make up the coal-formation; nor as to the varying proportions, and changes in the species of ferns and other plants, in the successive systems of vegetation that have clothed our globe.

"It may be further noticed, that as both trunks and leaves of Angiospermous dicolyledonous plants have been abundantly preserved in the tertiary formations, there appears to be no reason why, if plants of this tribe had existed during the secondary and transition periods, they should not occasionally have escaped destruction in the sedimentary deposits of these earlier epochs.”—P. 481.

Dr. Buckland has not dwelt sufficiently on the various causes which influence the preservation in strata of parts of organic beings; nor on the circumstances that cause a far greater Lumerical proportion of the remains of certain classes and orders to be found than of others. Without this commentary, the nature and value of the evidence derived from this source cannot be properly appreciated; unless thus forewarned, the first hasty conclusion which would be drawn, is, that the proportion between the numbers of species of which the remains are preserved, was the same as that of the species existing at the period.

But when it is shown that marine animals, generally, are placed in circumstances most favourable to the preservation of their solid parts, and conchiferous and molluscous more so than fish, and these again more than amphibious reptiles,—and that it must require a rare combination of circumstances to allow of the skeletons of birds, or the exuviæ of insects, being preserved from that decomposition to which the most solid parts of all organic beings are subject from exposure to atmospheric influence; the student is made aware of the caution necessary to be used in drawing inferences as to the state of living creation at any former period, from the fossil remains of that time. Perhaps in the strong cases we have cited in illustration, his unaided judgment would not far mislead him; and he would infer from analogy, the existence of a proportional number

of insects at all periods of the Creation, to serve as the intermediate agents in the ceaseless routine of conversion of animal into vegetable bodies, destined again to furnish nutriment to the former; but it is necessary he should constantly have these general principles present to his mind, to apply before he draws any conclusions on the subject of the numerical proportion of living beings of the most nearly related orders, since, even among these, habits and modes of life may concur to favour the preservation of the remains of certain genera, while those of others may strongly militate against the preservation of any records of them.

We are here obliged to close our remarks, and we are less reluctant to do so, knowing how much has appeared elsewhere in our own as well as in the pages of cotemporary works; the volumes are, indeed, replete with the most interesting and valuable information on the subject of fossil remains; and our regret that Dr. Buckland did not make the plan of his work more comprehensive, shows how highly we estimate both the extent of his knowledge and his powers of instruction.

We will not conclude our notice without expressing admiration at the taste and judgment shown in the selection and execution of the plates. The wood-cuts, designed and engraved by Mr. Fisher, place him in the first rank of his invaluable profession, and the exquisite skill and talent of Mr. J. D. C. Sowerby as an artist are well known. Dr. Buckland will not take it as a bad compliment, if we say that his second volume alone would entitle him to the gratitude of every naturalist and geologist.

THE PHILOSOPHY OF THE HOUR-GLASS.

In olden time, long ere the art of clock-making was discovered, our ancestors marked the fleeting hours by the flowing of sand in a glass. This contrivance was called the hour-glass, and it is still very generally to be found upon the table of the public lecturer, or the private teacher, in the laboratory of the philosopher, or in the cottage of the peasant. It is a far more accurate measurer of time than is usually imagined, and, therefore, perhaps a short account of the theory of its action may be acceptable to the readers of the Magazine of Practical Science.

The investigation was undertaken a few years since by M. H. Bournand: his experiments are exceedingly curious, and merit to be more generally known. A few only of the most remarkable, and easy of performance, are detailed in the following notice.

The first remarkable fact regarding the hour-glass is, that the flow of its enclosed sand is perfectly equable, whatever may be the quantity contained in the glass, at any period of its flowing: or, in other words, that it runs no faster when the upper cone is quite full, than when it is nearly empty. This is contrary to what we might expect, for it would be natural enough to conclude, that when full of sand, the lowest particles would sustain a greater pressure from the incumbent mass, and, therefore, be more swiftly urged through the aperture, than when only a quarter full, and near the close of the hour.