Chapter IV…

Chapter IV

EXAMINATION OF THE PROCESS OF REPRODUCTION IN ANIMALS AND PLANTS, AND CONSEQUENT SPECULATIONS.

Sect. 1.--The Examination of the Process of Reproduction in Animals.

IT would not, perhaps, be necessary to give any more examples of what has hitherto been the general process of investigations on each branch of physiology; or to illustrate further the combination which such researches present, of certain with uncertain knowledge;--of solid discoveries of organs and processes, succeeded by indefinite and doubtful speculation concerning vital forces. But the reproduction of organized beings is not only a subject of so much interest as to require some notice, but also offers to us laws and principles which include both the vegetable and the animal kingdom; and which, therefore, are requisite to render intelligible the most general views to which we can attain, respecting the world of organization.

The facts and laws of reproduction were first studied in detail in animals. The subject appears to have attracted the attention of some of the philosophers of antiquity in an extraordinary degree: and indeed we may easily imagine that they hoped, by following this path, if any, to solve the mystery of creation. Aristotle appears to have pursued it with peculiar complacency; and his great work On animals contains[46\17] an extraordinary collection of curious observations relative to this subject. He had learnt the modes of reproduction of most of the animals with which he was acquainted; and his work is still, as a writer of our own times has said,[47\17] "original after so many copies, and young after two thousand years." His observations referred principally to the external circumstances of generation: the anatomical examination was {456} left to his successors. Without dwelling on the intermediate labors, we come to modern times, and find that this examination owes its greatest advance to those who had the greatest share in the discovery of the circulation of the blood;--Fabricius of Acquapendente, and Harvey. The former[48\17] published a valuable work on the Egg and the Chick. In this are given, for the first time, figures representing the developement of the chick, from its almost imperceptible beginning, to the moment when it breaks the shell. Harvey pursued the researches of his teacher. Charles[49\17] the First had supplied him with the means of making the experiments which his purpose required, by sacrificing a great number of the deer in Windsor Park in the state of gestation: but his principal researches were those respecting the egg, in which he followed out the views of Fabricius. In the troubles which succeeded the death of the unfortunate Charles the house of Harvey was pillaged; and he lost the whole of the labors he had bestowed on the generation of insects. His work, Exercitationes de Generatione Animalium, was published at London in 1651; it is more detailed and perfect than that of Fabricius; but the author was prevented by the unsettled condition of the country from getting figures engraved to accompany his descriptions.

[Note 46\17: Bourdon, p. 161.]

[Note 47\17: Ib. p. 101.]

[Note 48\17: Cuv. Hist. Sc. Nat. p. 46.]

[Note 49\17: Ib. p. 53.]

Many succeeding anatomists pursued the examination of the series of changes in generation, and of the organs which are concerned in them, especially Malpighi, who employed the microscope in this investigation, and whose work on the Chick was published in 1673. It is impossible to give here any general view of the result of these laborious series of researches: but we may observe, that they led to an extremely minute and exact survey of all the parts of the fœtus, its envelopes and appendages, and, of course, to a designation of these by appropriate names. These names afterwards served to mark the attempts which were made to carry the analogy of animal generation into the vegetable kingdom.

There is one generalization of Harvey which deserves notice.[50\17] He was led by his researches to the conclusion, that all living things may be properly said to come from eggs: "Omne vivum ex ovo." Thus not only do oviparous animals produce by means of eggs, but in those which are viviparous, the process of generation begins with the developement of a small vesicle, which comes from the ovary, and which exists before the embryo: and thus viviparous or suckling-beasts, {457} notwithstanding their name, are born from eggs, as well as birds, fishes, and reptiles.[51\17] This principle also excludes that supposed production of organized beings without parents (of worms in corrupted matter, for instance,) which was formerly called spontaneous generation; and the best physiologists of modern times agree in denying the reality of such a mode of generation.[52\17]

[Note 50\17: Exerc. lxiii.]

[Note 51\17: Bourdon, p. 221.]

[Note 52\17: Ib. p. 49.]

Sect. 2.--The Examination of the Process of Reproduction in Vegetables.

THE extension of the analogies of animal generation to the vegetable world was far from obvious. This extension was however made;--with reference to the embryo plant, principally by the microscopic observers, Nehemiah Grew, Marcello Malpighi, and Antony Leeuwenhoek;--with respect to the existence of the sexes, by Linnæus and his predecessors.

The microscopic labors of Grew and Malpighi were patronized by the Royal Society of London in its earliest youth. Grew's book, The Anatomy of Plants, was ordered to be printed in 1670. It contains plates representing extremely well the process of germination in various seeds, and the author's observations exhibit a very clear conception of the relation and analogies of different portions of the seed. On the day on which the copy of this work was laid before the Society, a communication from Malpighi of Bologna, Anatomes Plantarum Idea, stated his researches, and promised figures which should illustrate them. Both authors afterwards went on with a long train of valuable observations, which they published at various times, and which contain much that has since become a permanent portion of the science.

Both Grew and Malpighi were, as we have remarked, led to apply to vegetable generation many terms which imply an analogy with the generation of animals. Thus, Grew terms the innermost coat of the seed, the secundine; speaks of the navel-fibres, &c. Many more such terms have been added by other writers. And, as has been observed by a modern physiologist,[53\17] the resemblance is striking. Both in the vegetable seed and in the fertilized animal egg, we have an embryo, chalazæ, a placenta, an umbilical cord, a cicatricula, an amnios, membranes, nourishing vessels. The cotyledons of the seed are the equivalent of the vitellus of birds, or of the umbilical vesicle of **suckling-beasts: {458} the albumen or perisperm of the grain is analogous to the white of the egg of birds, or the allantoid of viviparous animals.

[Note 53\17: Ib. p. 384.]

Sexes of Plants.--The attribution of sexes to plants, is a notion which was very early adopted; but only gradually unfolded into distinctness and generality.[54\17] The ancients were acquainted with the fecundation of vegetables. Empedocles, Aristotle, Theophrastus, Pliny, and some of the poets, make mention of it; but their notions were very incomplete, and the conception was again lost in the general shipwreck of human knowledge. A Latin poem, composed in the fifteenth century by Jovianus Pontanus, the preceptor of Alphonso, King of Naples, is the first modern work in which mention is made of the sex of plants. Pontanus sings the loves of two date-palms, which grew at the distance of fifteen leagues from each other: the male at Brundusium, the female at Otranto. The distance did not prevent the female from becoming fruitful, as soon as the palms had raised their heads above the surrounding trees, so that nothing intervened directly between them, or, to speak with the poet, so that they were able to see each other.

[Note 54\17: Mirbel, El. ii. 538.]

Zaluzian, a botanist who lived at the end of the fifteenth century, says that the greater part of the species of plants are androgynes, that is, have the properties of the male and of the female united in the same plant; but that some species have the two sexes in separate individuals; and he adduces a passage of Pliny relative to the fecundation of the date-palm. John Bauhin, in the middle of the seventeenth century, cites the expressions of Zaluzian; and forty years later, a professor of Tübingen, Rudolph Jacob Camerarius, pointed out clearly the organs of generation, and proved by experiments on the mulberry, on maize, and on the plant called Mercury (mercurialis), that when by any means the action of the stamina upon the pistils is intercepted, the seeds are barren. Camerarius, therefore, a philosopher in other respects of little note, has the honor assigned him of being the author of the discovery of the sexes of plants in modern times.[55\17]

[Note 55\17: Mirbel, ii. 539.]

The merit of this discovery will, perhaps, appear more considerable when it is recollected that it was rejected at first by very eminent botanists. Thus Tournefort, misled by insufficient experiments, maintained that the stamina are excretory organs; and Reaumur, at the beginning of the eighteenth century, inclined to the same doctrine. {459} Upon this, Geoffroy, an apothecary at Paris, scrutinized afresh the sexual organs; he examined the various forms of the pollen, already observed by Grew and Malpighi; he pointed out the excretory canal, which descends through the style, and the micropyle, or minute orifice in the coats of the ovule, which is opposite to the extremity of this canal; though he committed some mistakes with regard to the nature of the pollen. Soon afterwards, Sebastian Vaillant, the pupil of Tournefort, but the corrector of his error on this subject, explained in his public lectures the phenomenon of the fecundation of plants, described the explosion of the anthers, and showed that the florets of composite flowers, though formed on the type of an androgynous flower, are sometimes male, sometimes female, and sometimes neuter.

But though the sexes of plants had thus been noticed, the subject drew far more attention when Linnæus made the sexual parts the basis of his classification. Camerarius and Burkard had already entertained such a thought, but it was Linnæus who carried into effect, and thus made the notion of the sexes of vegetables almost as familiar to us as that of the sexes of animals.

Sect. 3.--The Consequent Speculations.--Hypotheses of Generation.

THE views of the processes of generation, and of their analogies throughout the whole of the organic world, which were thus established and diffused, form an important and substantial part of our physiological knowledge. That a number of curious but doubtful hypotheses should be put forward, for the purpose of giving further significance and connexion to these discoveries, was to be expected. We must content ourselves with speaking of these very briefly. We have such hypotheses in the earliest antiquity of Greece; for as we have already said, the speculations of cosmogony were the source of the Greek philosophy; and the laws of generation appeared to offer the best promise of knowledge respecting the mystery of creation. Hippocrates explained the production of a new animal by the mixture of seed of the parents; and the offspring was male or female as the seminal principle of the father or of the mother was the more powerful. According to Aristotle, the mother supplied the matter, and the father the form. Harvey's doctrine was, that the ovary of the female is fertilized by a seminal contagion produced by the seed of the male. But an opinion which obtained far more general reception was, that {460} the embryo pre-existed in the mother, before any union of the sexes.[56\17] It is easy to see that this doctrine is accompanied with great difficulties;[57\17] for if the mother, at the beginning of life, contain in her the embryos of all her future children; these embryos again must contain the children which they are capable of producing; and so on indefinitely; and thus each female of each species contains in herself the germs of infinite future generations. The perplexity which is involved in this notion of an endless series of creatures, thus encased one within another, has naturally driven inquirers to attempt other suppositions. The microscopic researches of Leeuwenhoek and others led them to the belief that there are certain animalcules contained in the seed of the male, which are the main agents in the work of reproduction. This system ascribes almost everything to the male, as the one last mentioned does to the female. Finally, we have the system of Buffon;--the famous hypothesis of organic molecules. That philosopher asserted that he found, by the aid of the microscope, all nature full of moving globules, which he conceived to be, not animals as Leeuwenhoek imagined, but bodies capable of producing, by their combination, either animals or vegetables, in short, all organized bodies. These globules he called organic molecules.[58\17] And if we inquire how these organic molecules, proceeding from all parts of the two parents, unite into a whole, as perfect as either of the progenitors, Buffon answers, that this is the effect of the interior mould; that is, of a system of internal laws and tendencies which determine the form of the result as an external mould determines the shape of the cast.

[Note 56\17: Bourdon, p. 204.]

[Note 57\17: Ib. p. 209.]

[Note 58\17: Ib. p. 219.]

An admirer of Buffon, who has well shown the untenable character of this system, has urged, as a kind of apology for the promulgation of the hypothesis,[59\17] that at the period when its author wrote, he could not present his facts with any hope of being attended to, if he did not connect them by some common tie, some dominant idea which might gratify the mind; and that, acting under this necessity, he did well to substitute for the extant theories, already superannuated and confessedly imperfect, conjectures more original and more probable. Without dissenting from this view, we may observe, that Buffon's theory, like those which preceded it, is excusable, and even deserving of admiration, so far as it groups the facts consistently; because in doing this, it exhibits the necessity, which the physiological speculator ought to feel, of aspiring to definite and solid general principles; and that thus, though {461} the theory may not be established as true, it may be useful by bringing into view the real nature and application of such principles.

[Note 59\17: Ib. p. 221.]

It is, therefore, according to our views, unphilosophical to derive despair, instead of hope, from the imperfect success of Buffon and his predecessors. Yet this is what is done by the writer to whom we refer. "For me," says he,[60\17] "I vow that, after having long meditated on the system of Buffon,--a system so remarkable, so ingenious, so well matured, so wonderfully connected in all its parts, at first sight so probable;--I confess that, after this long study, and the researches which it requires, I have conceived in consequence, a distrust of myself a skepticism, a disdain of hypothetical systems, a decided predilection and exclusive taste for pure and rational observation, in short, a disheartening, which I had never felt before."

[Note 60\17: Bourdon, p. 274.]

The best remedy of such feelings is to be found in the history of science. Kepler, when he had been driven to reject the solid epicycles of the ancients, or a person who had admired Kepler as M. Bourdon admires Buffon, but who saw that his magnetic virtue was an untenable fiction, might, in the same manner, have thrown up all hope of a sound theory of the causes of the celestial motions. But astronomers were too wise and too fortunate to yield to such despondency. The predecessors of Newton substituted a solid science of Mechanics for the vague notions of Kepler; and the time soon came when Newton himself reduced the motions of the heavens to a Law as distinctly conceived as the Motions had been before.

Chapter V

EXAMINATION OF THE NERVOUS SYSTEM, AND CONSEQUENT SPECULATIONS.

Sect. 1.--The Examination of the Nervous System.

IT is hardly necessary to illustrate by further examples the manner in which anatomical observation has produced conjectural and hypothetical attempts to connect structure and action with some {462} higher principle, of a more peculiarly physiological kind. But it may still be instructive to notice a case in which the principle, which is thus brought into view, is far more completely elevated above the domain of matter and mechanism than in those we have yet considered;--a case where we have not only Irritation, but Sensation;--not only Life, but Consciousness and Will. A part of science in which suggestions present themselves, brings us, in a very striking manner, to the passage from the physical to the hyperphysical sciences.

We have seen already (chap. i.) that Galen and his predecessors had satisfied themselves that the nerves are the channels of perception; a doctrine which had been distinctly taught by Herophilus[61\17] in the Alexandrian school. Herophilus, however, still combined, under the common name of Nerves, the Tendons; though he distinguished such Nerves from those which arise from the brain and the spinal marrow, and which are subservient to the will. In Galen's time this subject had been prosecuted more into detail. That anatomist has left a Treatise expressly upon The Anatomy of the Nerves; in which he describes the successive Pairs of Nerves: thus, the First Pair are the visual nerves: and we see, in the language which Galen uses, the evidence of the care and interest with which he had himself examined them. "These nerves," he says, "are not resolved into many fibres, like all the other nerves, when they reach the organs to which they belong; but spread out in a different and very remarkable manner, which it is not easy to describe or to believe, without actually seeing it." He then gives a description of the retina. In like manner he describes the Second Pair, which is distributed to the muscles of the eyes; the Third and Fourth Pairs, which go to the tongue and palate; and so on to the Seventh Pair. This division into Seven Pairs was established by Marinus,[62\17] but Vesalius found it to be incomplete. The examination which is the basis of the anatomical enumeration of the Nerves at present recognized was that of Willis. His book, entitled Cerebri Anatome, cui accessit Nervorum descriptio et usus, appeared at London in 1664. He made important additions to the knowledge of this subject.[63\17] Thus he is the first who describes in a distinct manner what has been called the Nervous Centre,[64\17] the pyramidal eminences which, according to more recent anatomists, are the communication of the brain with the spinal marrow: and of which the Decussation, described by Santorini, affords the explanation of the action of a part {463} of the brain upon the nerves of the opposite side. Willis proved also that the Rete Mirabile, the remarkable net-work of arteries at the base of the brain, observed by the ancients in ruminating animals, does not exist in man. He described the different Pairs of Nerves with more care than his predecessors; and his mode of numbering them is employed up to the present time. He calls the Olfactory Nerves the First Pair; previously to him, these were not reckoned a Pair: and thus the optic nerves were, as we have seen, called the first. He added the Sixth and the Ninth Pairs, which the anatomists who preceded him did not reckon. Willis also examined carefully the different Ganglions, or knots which occur upon the nerves. He traced them wherever they were to be found, and he gave a general figure of what Cuvier calls the nervous skeleton, very superior to that of Vesalius, which was coarse and inexact. Willis also made various efforts to show the connexion of the parts of the brain. In the earlier periods of anatomy, the brain had been examined by slicing it, so as to obtain a section. Varolius endeavored to unravel it, and was followed by Willis. Vicq d'Azyr, in modern times, has carried the method of section to greater perfection than had before been given it;[65\17] as Vieussens and Gall have done with respect to the method of Varolius and Willis. Recently Professor Chaussier[66\17] makes three kinds of Nerves:--the Encephalic, which proceed from the head, and are twelve on each side;--the Rachidian, which proceed from the spinal marrow, and are thirty on each side;--and Compound Nerves, among which is the Great Sympathetic Nerve.

[Note 61\17: Spr. i. 534.]

[Note 62\17: Dic. Sc. Med. xxxv. 467.]

[Note 63\17: Cuv. Sc. Nat. p. 385.]

[Note 64\17: Ibid.]

[Note 65\17: Cuv. p. 40.]

[Note 66\17: Dict. Sc. Nat. xxxv. 467.]

One of the most important steps ever made in our knowledge of the nerves is, the distinction which Bichat is supposed to have established, of a ganglionic system, and a cerebral system. And we may add, to the discoveries in nervous anatomy, the remarkable one, made in our own time, that the two offices--of conducting the motive impressions from the central seat of the will to the muscles, and of propagating sensations from the surface of the body and the external organs of sense to the sentient mind--reside in two distinct portions of the nervous substance:--a discovery which has been declared[67\17] to be "doubtless the most important accession to physiological (anatomical) knowledge since the time of Harvey." This doctrine was first published and taught by Sir Charles Bell: after an interval of some {464} years, it was more distinctly delivered in the publications of Mr. John Shaw, Sir C. Bell's pupil. Soon afterwards it was further confirmed, and some part of the evidence corrected, by Mr. Mayo, another pupil of Sir C. Bell, and by M. Majendie.[68\17]

[Note 67\17: Dr. Charles Henry's Report of Brit. Assoc. iii. p. 62.]

[Note 68\17: As authority for the expressions which I have now used in the text, I will mention Müller's Manual of Physiology (4th edition, 1844). In Book iii. Section 2, Chap. i., "On the Nerves of Sensation and Motion," Müller says, "Charles Bell was the first who had the ingenious thought that the posterior roots of the nerves of the spine--those which are furnished with a ganglion--govern sensation only; that the anterior roots are appointed for motion; and that the primitive fibres of these roots, after being united in a single nervous cord, are mingled together in order to supply the wants of the skin and muscles. He developed this idea in a little work (An Idea of a new Anatomy of the Brain, London, 1811), which was not intended to travel beyond the circle of his friends." Müller goes on to say, that eleven years later, Majendie prosecuted the same theory. But Mr. Alexander Shaw, in 1839, published A Narrative of the Discoveries of Sir Charles Bell in the Nervous System, in which it appears that Sir Charles Bell had further expounded his views in his lectures to his pupils (p. 89), and that one of these, Mr. John Shaw, had in various publications, in 1821 and 1822, further insisted upon the same views; especially in a Memoir On Partial Paralysis (p. 75). MM. Mayo and Majendie both published Memoirs in August, 1822; and these and subsequent works confirmed the doctrine of Bell. Mr. Alexander Shaw states (p. 97), that a mistake of Sir Charles Bell's, in an experiment which he had made to prove his doctrine, was discovered through the joint labors of M. Majendie and Mr. Mayo.]

Sect. 2.--_The Consequent Speculations. Hypotheses respecting Life, Sensation, and Volition._

I SHALL not attempt to explain the details of these anatomical investigations; and I shall speak very briefly of the speculations which have been suggested by the obvious subservience of the nerves to life, sensation, and volition. Some general inferences from their distribution were sufficiently obvious; as, that the seat of sensation and volition is in the brain. Galen begins his work, On the Anatomy of the Nerves, thus: "That none of the members of the animal either exercises voluntary motion, or receives sensation, and that if the nerve be cut, the part immediately becomes inert and insensible, is acknowledged by all physicians. But that the origin of the nerves is partly from the brain, and partly from the spinal marrow, I proceed to explain." And in his work On the Doctrines of Plato and Hippocrates, he proves at {465} great length[69\17] that the brain is the origin of sensation and motion, refuting the opinions of earlier days, as that of Chrysippus,[70\17] who placed the hegemonic or master-principle of the soul, in the heart. But though Galen thought that the rational soul resides in the brain, he was disposed to agree with the poets and philosophers, according to whom the heart is the seat of courage and anger, and the liver the seat of love.[71\17] The faculties of the soul were by succeeding physiologists confined to the brain; but the disposition still showed itself, to attribute to them distinct localities. Thus Willis[72\17] places the imagination in the corpus callosum, the memory in the folds of the hemispheres, the perception in the corpus striatum. In more recent times, a system founded upon a similar view has been further developed by Gall and his followers. The germ of Gall's system may be considered as contained in that of Willis; for Gall represents the hemispheres as the folds of a great membrane which is capable of being unwrapped and spread out, and places the different faculties of man in the different regions of this membrane. The chasm which intervenes between matter and motion on the one side, and thought and feeling on the other, is brought into view by all such systems; but none of the hypotheses which they involve can effectually bridge it over.

[Note 69\17: Lib. vii.]

[Note 70\17: Lib. iii. c. 1.]

[Note 71\17: Lib. vi. c. 8.]

[Note 72\17: Cuv. Sc. Nat. p. 384.]

The same observation may be made respecting the attempts to explain the manner in which the nerves operate as the instruments of sensation and volition. Perhaps a real step was made by Glisson,[73\17] professor of medicine in the University of Cambridge, who distinguished in the fibres of the muscles of motion a peculiar property, different from any merely mechanical or physical action. His work On the Nature of the Energetic Substance, or on the Life of Nature and of its Three First Faculties, The Perceptive, Appetitive, and Motive, which was published in 1672, is rather metaphysical than physiological. But the principles which he establishes in this treatise he applies more specially to physiology in a treatise On the Stomach and Intestines (Amsterdam, 1677). In this he ascribes to the fibres of the animal body a peculiar power which he calls Irritability. He divides irritation into natural, vital, and animal; and he points out, though briefly, the gradual differences of irritability in different organs. "It is hardly comprehensible," says Sprengel,[74\17] "how this {466} lucid and excellent notion of the Cambridge teacher was not accepted with greater alacrity, and further unfolded by his contemporaries." It has, however, since been universally adopted.

[Note 73\17: Cuv. Sc. Nat. p. 434.]

[Note 74\17: Spr. iv. 47.]

But though the discrimination of muscular irritability as a peculiar power might be a useful step in physiological research, the explanations hitherto offered, of the way in which the nerves operate on this irritability, and discharge their other offices, present only a series of hypotheses. Glisson[75\17] assumed the existence of certain vital spirits, which, according to him, are a mild, sweet fluid, resembling the spirituous part of white of egg, and residing in the nerves.--This hypothesis, of a very subtle humor or spirit existing in the nerves, was indeed very early taken up.[76\17] This nervous spirit had been compared to air by Erasistratus, Asclepiades, Galen, and others. The chemical tendencies of the seventeenth century led to its being described as acid, sulphureous or nitrous. At the end of that century, the hypothesis of an ether attracted much notice as a means of accounting for many phenomena; and this ether was identified with the nervous fluid. Newton himself inclines to this view, in the remarkable Queries which are annexed to his Opticks. After ascribing many physical effects to his ether, he adds (Query 23), "Is not vision performed chiefly by the vibrations of this medium, excited in the bottom of the eye by the rays of light, and propagated through the solid, pellucid, and uniform capillamenta of the nerves into the place of sensation?" And (Query 24), "Is not animal motion performed by the vibrations of this medium, excited in the brain by the power of the will, and propagated from thence through the capillamenta of the nerves into the muscles for contracting and dilating them?" And an opinion approaching this has been adopted by some of the greatest of modern physiologists; as Haller, who says,[77\17] that, though it is more easy to find what this nervous spirit is not than what it is, he conceives that, while it must be far too fine to be perceived by the sense, it must yet be more gross than fire, magnetism, or electricity; so that it may be contained in vessels, and confined by boundaries. And Cuvier speaks to the same effect:[78\17] "There is a great probability that it is by an imponderable fluid that the nerve acts on the fibre, and that this nervous fluid is drawn from the blood, and secreted by the medullary matter."

[Note 75\17: Spr. iv. 38.]

[Note 76\17: Haller, Physiol. iv. 365.]

[Note 77\17: Physiol. iv. 381, lib. x. sect. viii. § 15.]

[Note 78\17: Règne Animal, Introd. p. 30.]

Without presuming to dissent from such authorities on a point of {467} anatomical probability, we may venture to observe, that these hypotheses do not tend at all to elucidate the physiological principle which is here involved; for this principle cannot be mechanical, chemical, or physical, and therefore cannot be better understood by embodying it in a fluid; the difficulty we have in conceiving what the moving force is, is not got rid of by explaining the machinery by which it is merely transferred. In tracing the phenomena of sensation and volition to their cause, it is clear that we must call in some peculiar and hyperphysical principle. The hypothesis of a fluid is not made more satisfactory by attenuating the fluid; it becomes subtle, spirituous, ethereal, imponderable, to no purpose; it must cease to be a fluid, before its motions can become sensation and volition. This, indeed, is acknowledged by most physiologists; and strongly stated by Cuvier.[79\17] "The impression of external objects upon the ME, the production of a sensation, of an image, is a mystery impenetrable for our thoughts." And in several places, by the use of this peculiar phrase, "the me," (le moi) for the sentient and volent faculty, he marks, with peculiar appropriateness and force, that phraseology borrowed from the world of matter will, in this subject, no longer answer our purpose. We have here to go from Nouns to Pronouns, from Things to Persons. We pass from the Body to the Soul, from Physics to Metaphysics. We are come to the borders of material philosophy; the next step is into the domain of Thought and Mind. Here, therefore, we begin to feel that we have reached the boundaries of our present subject. The examination of that which lies beyond them must be reserved for a philosophy of another kind, and for the labors of the future; if we are ever enabled to make the attempt to extend into that loftier and wider scene, the principles which we gather on the ground we are now laboriously treading.

[Note 79\17: Règne Animal, Introd. p. 47.]

Such speculations as I have quoted respecting the nervous fluid, proceeding from some of the greatest philosophers who ever lived, prove only that hitherto the endeavor to comprehend the mystery of perception and will, of life and thought, have been fruitless and vain. Many anatomical truths have been discovered, but, so far as our survey has yet gone, no genuine physiological principle. All the trains of physiological research which we have followed have begun in exact examination of organization and function, and have ended in wide conjectures and arbitrary hypotheses. The stream of knowledge in all such cases is {468} clear and lively at its outset; but, instead of reaching the great ocean of the general truths of science, it is gradually spread abroad among sands and deserts till its course can be traced no longer.

Hitherto, therefore, we must consider that we have had to tell the story of the failures of physiological speculation. But of late there have come into view and use among physiologists certain principles which may be considered as peculiar to organized subjects; and of which the introduction forms a real advance in organical science. Though these have hitherto been very imperfectly developed, we must endeavor to exhibit, in some measure, their history and bearing.

[2nd Ed.] [In order to show that I am not unaware how imperfect the sketch given in this work is, as a History of Physiology, I may refer to the further discussions on these subjects contained in the Philosophy of the Inductive Sciences, Book ix. I have there (Chap. ii.) noticed the successive Biological Hypotheses of the Mystical, the Iatrochemical, and Iatromathematical Schools, the Vital-Fluid School, and the Psychical School. I have (Chaps. iii., iv., v.) examined several of the attempts which have been made to analyze the Idea of Life, to classify Vital Functions, and to form Ideas of Separate Vital Forces. I have considered in particular, the attempts to form a distinct conception of Assimilation and Secretion, of Generation, and of Voluntary Motion; and I have (Chap. vi.) further discussed the Idea of Final Causes as employed in Biology.]

Chapter VI

INTRODUCTION OF THE PRINCIPLE OF DEVELOPED AND METAMORPHOSED SYMMETRY.

Sect. 1.--Vegetable Morphology. Göthe. De Candolle.

BEFORE we proceed to consider the progress of principles which belong to animal and human life, such as have just been pointed at, we must look round for such doctrines, if any such there be, as apply alike to all organized beings, conscious or unconscious, fixed or locomotive;--to the laws which regulate vegetable as well as animal forms and functions. Though we are very far from being able to present a {469} clear and connected code of such laws, we may refer to one law, at least, which appears to be of genuine authority and validity; and which is worthy our attention as an example of a properly organical or physiological principle, distinct from all mechanical, chemical, or other physical forces; and such as cannot even be conceived to be resolvable into those. I speak of the tendency which produces such results as have been brought together in recent speculations upon Morphology.

It may perhaps be regarded as indicating how peculiar are the principles of organic life, and how far removed from any mere mechanical action, that the leading idea in these speculations was first strongly and effectively apprehended, not by a laborious experimenter and reasoner, but by a man of singularly brilliant and creative fancy; not by a mathematician or chemist, but by a poet. And we may add further, that this poet had already shown himself incapable of rightly apprehending the relation of physical facts to their principles; and had, in trying his powers on such subjects, exhibited a signal instance of the ineffectual and perverse operation of the method of philosophizing to which the constitution of his mind led him. The person of whom we speak, is John Wolfgang Göthe, who is held, by the unanimous voice of Europe, to have been one of the greatest poets of our own, or of any time, and whose Doctrine of Colors we have already had to describe, in the History of Optics, as an entire failure. Yet his views on the laws which connect the forms of plants into one simple system, have been generally accepted and followed up. We might almost be led to think that this writer's poetical endowments had contributed to this scientific discovery;--the love of beauty of form, by fixing the attention upon the symmetry of plants; and the creative habit of thought, by making constant developement of a familiar process.[80\17] {470}

[Note 80\17: We may quote some of the poet's own verses as an illustration of his feelings on this subject. They are addressed to a lady.

Dich verwirret, geliebte, die tausendfältige mischung Dieses blumengewühls über dem garten umher; Viele namen hörest du an, und immer verdränget, Mit barbarischem klang, einer den andern im ohr. Alle gestalten sind **ähnlich und keine gleichet der andern; Und so deutet das chor auf ein geheimes gesetz, Auf ein heiliges räthsel. O! könnte ich dich, liebliche freundinn, Ueberliefern so gleich glücklich das lösende wort.

Thou, my love, art perplext with the endless seeming confusion Of the luxuriant wealth which in the garden is spread; Name upon name thou hearest, and in thy dissatisfied hearing, With a barbarian noise one drives another along. All the forms resemble, yet none is the same as another; Thus the whole of the throng points at a deep hidden law. Points at a sacred riddle. Oh! could I to thee, my beloved friend, Whisper the fortunate word by which the riddle is read!]

But though we cannot but remark the peculiarity of our being indebted to a poet for the discovery of a scientific principle, we must not forget that he himself held, that in making this step, he had been guided, not by his invention, but by observation. He repelled, with extreme repugnance, the notion that he had substituted fancy for fact, or imposed ideal laws on actual things. While he was earnestly pursuing his morphological speculations, he attempted to impress them upon Schiller. "I expounded to him, in as lively a manner as possible, the metamorphosis of plants, drawing on paper, with many characteristic strokes, a symbolic plant before his eyes. He heard me," Göthe says,[81\17] "with much interest and distinct comprehension; but when I had done, he shook his head, and said, 'That is not Experience; that is an Idea:' I stopt with some degree of irritation; for the point which separated us was marked most luminously by this expression." And in the same work he relates his botanical studies and his habit of observation, from which it is easily seen that no common amount of knowledge and notice of details, were involved in the course of thought which led him to the principle of the Metamorphosis of Plants.

[Note 81\17: Zur Morphologie, p. 24.]

Before I state the history of this principle, I may be allowed to endeavor to communicate to the reader, to whom this subject is new, some conception of the principle itself. This will not be difficult, if he will imagine to himself a flower, for instance, a common wild-rose, or the blossom of an apple-tree, as consisting of a series of parts disposed in whorls, placed one over another on an axis. The lowest whorl is the calyx with its five sepals; above this is the corolla with its five petals; above this are a multitude of stamens, which may be considered as separate whorls of five each, often repeated; above these is a whorl composed of the ovaries, or what become the seed-vessels in the fruit, which are five united together in the apple, but indefinite in number and separate in the rose. Now the morphological view is {471} this;--that the members of each of these whorls are in their nature identical, and the same as if they were whorls of ordinary leaves, brought together by the shortening their common axis, and modified in form by the successive elaboration of their nutriment. Further, according to this view, a whorl of leaves itself is to be considered as identical with several detached leaves dispersed spirally along the axis, and brought together because the axis is shortened. Thus all the parts of a plant are, or at least represent, the successive metamorphoses of the same elementary member. The root-leaves thus pass into the common leaves;--these into bracteæ;--these into the sepals;--these into the petals;--these into the stamens with their anthers;--these into the ovaries with their styles and stigmas;--these ultimately become the fruit; and thus we are finally led to the seed of a new plant.

Moreover the same notion of metamorphosis may be applied to explain the existence of flowers which are not symmetrical like those we have just referred to, but which have an irregular corolla or calyx. The papilionaceous flower of the pea tribe, which is so markedly irregular, may be deduced by easy gradations from the regular flower, (through the mimoseæ,) by expanding one petal, joining one or two others, and modifying the form of the intermediate ones.

Without attempting to go into detail respecting the proofs of that identity of all the different organs, and all the different forms of plants, which is thus asserted, we may observe, that it rests on such grounds as these;--the transformations which the parts of flowers undergo by accidents of nutriment or exposure. Such changes, considered as monstrosities where they are very remarkable, show the tendencies and possibilities belonging to the organization in which they occur. For instance, the single wild-rose, by culture, transforms many of its numerous stamens into petals, and thus acquires the deeply folded flower of the double garden-rose. We cannot doubt of the reality of this change, for we often see stamens in which it is incomplete. In other cases we find petals becoming leaves, and a branch growing out of the centre of the flower. Some pear-trees, when in blossom, are remarkable for their tendencies to such monstrosities.[82\17] Again, we find that flowers which are usually irregular, occasionally become regular, and conversely. The common snap-dragon (Linaria vulgaris) affords a curious instance of this.[83\17] The usual form of this plant is "personate," the corolla being divided into two lobes, which differ in form, and {472} together present somewhat the appearance of an animal's face; and the upper portion of the corolla is prolonged backwards into a tube-like "spur." No flower can be more irregular; but there is a singular variety of this plants termed Peloria, in which the corolla is strictly symmetrical, consisting of a conical tube, narrowed in front, elongated behind into five equal spurs, and containing five stamens of equal length, instead of the two unequal pairs of the didynamous Linaria. These and the like appearances show that there is in nature a capacity for, and tendency to, such changes as the doctrine of metamorphosis asserts.

[Note 82\17: Lindley, Nat. Syst. p. 84.]

[Note 83\17: Henslow, Principles of Botany, p. 116.]

Göthe's Metamorphosis of Plants was published 1790: and his system was the result of his own independent course of thoughts. The view which it involved was not, however, absolutely new, though it had never before been unfolded in so distinct and persuasive a manner. Linnæus considered the leaves, calyx, corolla, stamens, each as evolved in succession from the other; and spoke of it as prolepsis or anticipation,[84\17] when the leaves changed accidentally into bracteæ, these into a calyx, this into a corolla, the corolla into stamens, or these into the pistil. And Caspar Wolf apprehended in a more general manner the same principle. "In the whole plant," says he,[85\17] "we see nothing but leaves and stalk;" and in order to prove what is the situation of the leaves in all their later forms, he adduces the cotyledons as the first leaves.

[Note 84\17: Sprengel, Bot. ii. 302. Amœn. Acad. vi. 324, 365.]

[Note 85\17: Nov. Con. Ac. Petrop. xii. 403, xiii. 478.]

Göthe was led to his system on this subject by his general views of nature. He saw, he says,[86\17] that a whole life of talent and labor was requisite to enable any one to arrange the infinitely copious organic forms of a single kingdom of nature. "Yet I felt," he adds, "that for me there must be another way, analogous to the rest of my habits. The appearance of the changes, round and round, of organic creatures had taken strong hold on my mind. Imagination and Nature appeared to me to vie with each other which could go on most boldly yet most consistently." His observation of nature, directed by such a thought, led him to the doctrine of the metamorphosis.

[Note 86\17: Zur Morph. i. 30.]

In a later republication of his work (Zur Morphologie, 1817,) he gives a very agreeable account of the various circumstances which affected the reception and progress of his doctrine. Willdenow[87\17] quoted {473} him thus:--"The life of plants is, as Mr. Göthe very prettily says, an expansion and contraction, and these alternations make the various periods of life." "This 'prettily,'" says Göthe, "I can be well content with, but the 'egregie,' of Usteri is much more pretty and obliging." Usteri had used this term respecting Göthe in an edition of Jussieu.

[Note 87\17: Zur Morph. i. 121.]

The application of the notion of metamorphosis to the explanation of double and monstrous flowers had been made previously by Jussieu. Göthe's merit was, to have referred to it the regular formation of the flower. And as Sprengel justly says,[88\17] his view had so profound a meaning, made so strong an appeal by its simplicity, and was so fruitful in the most valuable consequences, that it was not to be wondered at if it occasioned further examination of the subject; although many persons pretend to slight it. The task of confirming and verifying the doctrine by a general application of it to all cases,--a labor so important and necessary after the promulgation of any great principle,--Göthe himself did not execute. At first he collected specimens and made drawings with some such view,[89\17] but he was interrupted and diverted to other matters. "And now," says he, in his later publication, "when I look back on this undertaking, it is easy to see that the object which I had before my eyes was, for me, in my position, with my habits and mode of thinking, unattainable. For it was no less than this: that I was to take that which I had stated in general, and presented to the conception, to the mental intuition, in words; and that I should, in a particularly visible, orderly, and gradual manner, present it to the eye; so as to show to the outward sense that out of the germ of this idea might grow a tree of physiology fit to overshadow the world."

[Note 88\17: Gesch. Botan. ii. 304.]

[Note 89\17: Zur Morph. i. **129.]

Voigt, professor at Jena, was one of the first who adopted Göthe's view into an elementary work, which he did in 1808. Other botanists labored in the direction which had thus been pointed out. Of those who have thus contributed to the establishment and developement of the metamorphic doctrine. Professor De Candolle, of Geneva, is perhaps the most important. His Theory of Developement rests upon two main principles, abortion and adhesion. By considering some parts as degenerated or absent through the abortion of the buds which might have formed them, and other parts as adhering together, he holds that all plants may be reduced to perfect symmetry: and the actual and constant occurrence of such incidents is shown beyond {474} all doubt. And thus the snap-dragon, of which we have spoken above, is derived from the Peloria, which is the normal condition of the flower, by the abortion of one stamen, and the degeneration of two others. Such examples are too numerous to need to be dwelt on.

Sect. 2.--Application of Vegetable Morphology.

THE doctrine, being thus fully established, has been applied to solve different problems in botany; for instance, to explain the structure of flowers which appear at first sight to deviate widely from the usual forms of the vegetable world. We have an instance of such an application in Mr. Robert Brown's explanation of the real structure of various plants which had been entirely misunderstood: as, for example, the genus Euphorbia. In this plant he showed that what had been held to be a jointed filament, was a pedicel with a filament above it, the intermediate corolla having evanesced. In Orchideæ (the orchis tribe), he showed that the peculiar structure of the plant arose from its having six stamens (two sets of three each), of which five are usually abortive. In Coniferæ (the cone-bearing trees), it was made to appear that the seed was naked, while the accompanying appendage, corresponding to a seed-vessel, assumed all forms, from a complete leaf to a mere scale. In like manner it was proved that the pappus, or down of composite plants (as thistles), is a transformed calyx.

Along with this successful application of a profound principle, it was natural that other botanists should make similar attempts. Thus Mr. Lindley was led to take a view[90\17] of the structure of Reseda (mignonette) different from that usually entertained; which, when published, attracted a good deal of attention, and gained some converts among the botanists of Germany and France. But in 1833, Mr. Lindley says, with great candor, "Lately, Professor Henslow has satisfactorily proved, in part by the aid of a monstrosity in the common Mignonette, in part by a severe application of morphological rules, that my hypothesis must necessarily be false." Such an agreement of different botanists respecting the consequences of morphological rules, proves the reality and universality of the rules.

[Note 90\17: Lindley, Brit. Assoc. Report, iii. 50.]

We find, therefore, that a principle which we may call the Principle of Developed and Metamorphosed Symmetry, is firmly established {475} and recognized, and familiarly and successfully applied by botanists. And it will be apparent, on reflection, that though symmetry is a notion which applies to inorganic as well as to organic things, and is, in fact, a conception of certain relations of space and position, such developement and metamorphosis as are here spoken of, are ideas entirely different from any of those to which the physical sciences have led us in our previous survey; and are, in short, genuine organical or physiological ideas;--real elements of the philosophy of life.

We must, however imperfectly, endeavor to trace the application of this idea in the other great department of the world of life; we must follow the history of Animal Morphology.

VII. PROGRESS OF ANIMAL MORPHOLOGY

Sect. 1.--Rise of Comparative Anatomy.

THE most general and constant relations of the form of the organs, both in plants and animals, are the most natural grounds of classification. Hence the first scientific classifications of animals are the first steps in animal morphology. At first, a zoology was constructed by arranging animals, as plants were at first arranged, according to their external parts. But in the course of the researches of the anatomists of the seventeenth century, it was seen that the internal structure of animals offered resemblances and transitions of a far more coherent and philosophical kind, and the Science of Comparative Anatomy rose into favor and importance. Among the main cultivators of this science[91\17] at the period just mentioned, we find Francis Redi, of Arezzo; Guichard-Joseph Duvernay, who was for sixty years Professor of Anatomy at the Jardin du Roi at Paris, and during this lapse of time had for his pupils almost all the greatest anatomists of the greater part of the eighteenth century; Nehemiah Grew, secretary to the Royal Society of London, whose Anatomy of Plants we have already noticed.

[Note 91\17: Cuv. Leçons sur l'Hist. des Sc. Nat. 414, 420.]

But Comparative Anatomy, which had been cultivated with ardor {476} to the end of the seventeenth century, was, in some measure, neglected during the first two-thirds of the eighteenth. The progress of botany was, Cuvier sagaciously suggests,[92\17] one cause of this; for that science had made its advances by confining itself to external characters, and rejecting anatomy; and though Linnæus acknowledged the dependence of zoology upon anatomy[93\17] so far as to make the number of teeth his characters, even this was felt, in his method, as a bold step. But his influence was soon opposed by that of Buffon, Daubenton, and Pallas; who again brought into view the importance of comparative anatomy in Zoology; at the same time that Haller proved how much might be learnt from it in Physiology. John Hunter in England, the two Monros in Scotland, Camper in Holland, and Vicq d'Azyr in France, were the first to follow the path thus pointed out. Camper threw the glance of genius on a host of interesting objects, but almost all that he produced was a number of sketches; Vicq d'Azyr, more assiduous, was stopt in the midst of a most brilliant career by a premature death.

[Note 92\17: Cuv. Hist. Sc. Nat. i. 301.]

[Note 93\17: Ib.]

Such is Cuvier's outline of the earlier history of comparative anatomy. We shall not go into detail upon this subject; but we may observe that such studies had fixed in the minds of naturalists the conviction of the possibility and the propriety of considering large divisions of the animal kingdom as modifications of one common type. Belon, as early as 1555, had placed the skeleton of a man and a bird side by side, and shown the correspondence of parts. So far as the case of vertebrated animals extends, this correspondence is generally allowed; although it required some ingenuity to detect its details in some cases; for instance, to see the analogy of parts between the head of a man and a fish.

In tracing these less obvious correspondencies, some curious steps have been made in recent times. And here we must, I conceive, again ascribe no small merit to the same remarkable man who, as we have already had to point out, gave so great an impulse to vegetable morphology. Göthe, whose talent and disposition for speculating on all parts of nature were truly admirable, was excited to the study of anatomy by his propinquity to the Duke of Weimar's cabinet of natural history. In 1786, he published a little essay, the object of which was to show that in man, as well as in beasts, the upper jaw contains an intermaxillary bone, although the sutures are obliterated. After 1790,[94\17] animated and impelled by the same passion for natural {477} observation and for general views, which had produced his Metamorphosis of Plants, he pursued his speculations on these subjects eagerly and successfully. And in 1795, he published a Sketch of a Universal Introduction into Comparative Anatomy, beginning with Osteology; in which he attempts to establish an "osteological type," to which skeletons of all animals may be referred. I do not pretend that Göthe's anatomical works have had any influence on the progress of the science comparable with that which has been exercised by the labors of professional anatomists; but the ingenuity and value of the views which they contained was acknowledged by the best authorities; and the clearer introduction and application of the principle of developed and metamorphosed symmetry may be dated from about this time. Göthe declares that, at an early period of these speculations, he was convinced[95\17] that the bony head of beasts is to be derived from six vertebræ. In 1807, Oken published a "Program" On the Signification of the Bones of the Skull, in which he maintained that these bones are equivalent to four vertebræ); and Meckel, in his Comparative Anatomy, in 1811, also resolved the skull into vertebræ. But Spix, in his elaborate work Cephalogenesis, in 1815, reduced the vertebræ of the head to three. "Oken," he says,[96\17] "published opinions merely theoretical, and consequently contrary to those maintained in this work, which are drawn from observation." This resolution of the head into vertebræ is assented to by many of the best physiologists, as explaining the distribution of the nerves, and other phenomena. Spix further extended the application of the vertebral theory to the heads of all classes of vertebrate animals; and Bojanus published a Memoir expressly on the vertebral structure of the skulls of fishes in Oken's Isis for 1818. Geoffroy Saint-Hilaire presented a lithographic plate to the French Academy in February 1824, entitled Composition de la Tête **osseuse chez l'Homme et les Animaux, and developed his views of the vertebral composition of the skull in two Memoirs published in the Annales des Sciences Naturelles for 1824. We cannot fail to recognize here the attempt to apply to the skeleton of animals the principle which leads botanists to consider all the parts of a flower as transformations of the same organs. How far the application of the principle, as here proposed, is just, I must leave philosophical physiologists to decide.

[Note 94\17: Zur Morphologie, i. 234.]

[Note 95\17: Zur Morphologie, 250.]

[Note 96\17: Spix, Cephalogenesis.]

By these and similar researches, it is held by the best physiologists {478} that the skull of all vertebrate animals is pretty well reduced to a uniform structure, and the laws of its variations nearly determined.[97\17]

[Note 97\17: Cuv. Hist. Sc. Nat. iii. 442.]

The vertebrate animals being thus reduced to a single type, the question arises how far this can be done with regard to other animals, and how many such types there are. And here we come to one of the important services which Cuvier rendered to natural history.

Sect. 2.--Distinction of the General Types of the Forms of Animals.--Cuvier.

ANIMALS were divided by Lamarck into vertebrate and invertebrate; and the general analogies of all vertebrate animals are easily made manifest. But with regard to other animals, the point is far from clear. Cuvier was the first to give a really philosophical view of the animal world in reference to the plan on which each animal is constructed. There are,[98\17] he says, four such plans;--four forms on which animals appear to have been modelled; and of which the ulterior divisions, with whatever titles naturalists have decorated them, are only very slight modifications, founded on the development or addition of some parts which do not produce any essential change in the plan.

[Note 98\17: Règne Animal, p. 57.]

These four great branches of the animal world are the vertebrata, mollusca, articulata, radiata; and the differences of these are so important that a slight explanation of them may be permitted.

The vertebrata are those animals which (as man and other sucklers, birds, fishes, lizards, frogs, serpents) have a backbone and a skull with lateral appendages, within which the viscera are included, and to which the muscles are attached.

The mollusca, or soft animals, have no bony skeleton; the muscles are attached to the skin, which often includes stony plates called shells; such molluscs are shell-fish; others are cuttle-fish, and many pulpy sea-animals.

The articulata consist of crustacea (lobsters, &c.), insects, spiders, and annulose worms, which consist of a head and a number of successive annular portions of the body jointed together (to the interior of which the muscles are attached), whence the name.

Finally, the radiata include the animals known under the name of zoophytes. In the preceding three branches the organs of motion and of sense were distributed symmetrically on the two sides of an axis, {479} so that the animal has a right and a left side. In the radiata the similar members radiate from the axis in a circular manner, like the petals of a regular flower.

The whole value of such a classification cannot be understood without explaining its use in enabling us to give general descriptions, and general laws of the animal functions of the classes which it includes; but in the present part of our work our business is to exhibit it as an exemplification of the reduction of animals to laws of Symmetry. The bipartite Symmetry of the form of vertebrate and articulate animals is obvious; and the reduction of the various forms of such animals to a common type has been effected, by attention to their anatomy, in a manner which has satisfied those who have best studied the subject. The molluscs, especially those in which the head disappears, as oysters, or those which are rolled into a spiral, as snails, have a less obvious Symmetry, but here also we can apply certain general types. And the Symmetry of the radiated zoophytes is of a nature quite different from all the rest, and approaching, as we have suggested, to the kind of Symmetry found in plants. Some naturalists have doubted whether[99\17] these zoophytes are not referrible to two types (acrita or polypes, and true radiata,) rather than to one.

[Note 99\17: Brit. Assoc. Rep. iv. 227.]

This fourfold division was introduced by Cuvier.[100\17] Before him, naturalists followed Linnæus, and divided non-vertebrate animals into two classes, insects and worms. "I began," says Cuvier, "to attack this view of the subject, and offered another division, in a Memoir read at the Society of Natural History of Paris, the 21st of Floreal, in the year III. of the Republic (May 10, 1795,) printed in the Décade Philosophique: in this, I mark the characters and the limits of molluscs, insects, worms, echinoderms, and zoophytes. I distinguish the red-blooded worms or annelides, in a Memoir read to the Institute, the 11th Nivose, year X. (December 31, 1801.) I afterwards distributed these different classes into three branches, each co-ordinate to the branch formed by the vertebrate animals, in a Memoir read to the Institute in July, 1812, printed in the Annales du Muséum d'Histoire Naturelle, tom. xix." His great systematic work, the Règne Animal, founded on this distribution, was published in 1817; and since that time the division has been commonly accepted among naturalists.

[Note 100\17: Règne A. 61.]

[2nd Ed.] [The question of the Classification of Animals is discussed in the first of Prof. Owen's Lectures on the Invertebrate {480} Animals (1843). Mr. Owen observes that the arrangement of animals into Vertebrate and Invertebrate which prevailed before Cuvier, was necessarily bad, inasmuch as no negative character in Zoology gives true natural groups. Hence the establishment of the sub-kingdoms, Mollusca, Articulata, Radiata, as co-ordinate with Vertebrata, according to the arrangement of the nervous system, was a most important advance. But Mr. Owen has seen reason to separate the Radiata of Cuvier into two divisions; the Nematoneura, in which the nervous system can be traced in a filamentary form (including Echinoderma, Ciliobrachiata, Cœlelmintha, Rotifera,) and the Acrita or lowest division of the animal kingdom, including Acalepha, Nudibrachiata, Sterelmintha, Polygastria.]

Sect. 3.--_Attempts to establish the Identity of the Types of Animal Forms._

SUPPOSING this great step in Zoology, of which we have given an account,--the reduction of all animals to four types or plans,--to be quite secure, we are then led to ask whether any further advance is possible;--whether several of these types can be referred to one common form by any wider effort of generalization. On this question there has been a considerable difference of opinion. Geoffroy Saint-Hilaire,[101\17] who had previously endeavored to show that all vertebrate animals were constructed so exactly upon the same plan as to preserve the strictest analogy of parts in respect to their osteology, thought to extend this unity of plan by demonstrating, that the hard parts of crustaceans and insects are still only modifications of the skeleton of higher animals, and that therefore the type of vertebrata must be made to include them also:--the segments of the articulata are held to be strictly analogous to the vertebras of the higher animals, and thus the former live within their vertebral column in the same manner as the latter live without it. Attempts have even been made to reduce molluscous and vertebrate animals to a community of type, as we shall see shortly.

[Note 101\17: Mr. Jenyns, Brit. Assoc. Rep. iv. 150.]

Another application of the principle, according to which creatures the most different are developments of the same original type, may be discerned[102\17] in the doctrine, that the embryo of the higher forms of animal life passes by gradations through those forms which are {481} permanent in inferior animals. Thus, according to this view, the human fœtus assumes successively the plan of the zoophyte, the worm, the fish, the turtle, the bird, the beast. But it has been well observed, that "in these analogies we look in vain for the precision which can alone support the inference that has been deduced;"[103\17] and that at each step, the higher embryo and the lower animal which it is supposed to resemble, differ in having each different organs suited to their respective destinations.

[Note 102\17: Dr. Clark, Report, Ib. iv. 113.]

[Note 103\17: Dr. Clark, p. 114.]

Cuvier[104\17] never assented to this view, nor to the attempts to refer the different divisions of his system to a common type. "He could not admit," says his biographer, "that the lungs or gills of the vertebrates are in the same connexion as the branchiæ of molluscs and crustaceans, which in the one are situated at the base of the feet, or fixed on the feet themselves, and in the other often on the back or about the arms. He did not admit the analogy between the skeleton of the vertebrates and the skin of the articulates; he could not believe that the tænia and the sepia were constructed on the same plan; that there was a similarity of composition between the bird and the echinus, the whale and the snail; in spite of the skill with which some persons sought gradually to efface their discrepancies."

[Note 104\17: Laurillard, Elog. de Cuvier, p. 66.]

Whether it may be possible to establish, among the four great divisions of the "Animal Kingdom," some analogies of a higher order than those which prevail within each division, I do not pretend to conjecture. If this can be done, it is clear that it must be by comparing the types of these divisions under their most general forms: and thus Cuvier's arrangement, so far as it is itself rightly founded on the unity of composition of each branch, is the surest step to the discovery of a unity pervading and uniting these branches. But those who generalize surely, and those who generalize rapidly, may travel in the same direction, they soon separate so widely, that they appear to move from each other. The partisans of a universal "unity of composition" of animals, accused Cuvier of being too inert in following the progress of physiological and zoological science. Borrowing their illustration from the political parties of the times, they asserted that he belonged to the science of resistance, not to the science of the movement. Such a charge was highly honorable to him; for no one acquainted with the history of zoology can doubt that he had a great share in the impulse by which the "movement" was occasioned; or that he {482} himself made a large advance with it; and it was because he was so poised by the vast mass of his knowledge, so temperate in his love of doubtful generalizations, that he was not swept on in the wilder part of the stream. To such a charge, moderate reformers, who appreciate the value of the good which exists, though they try to make it better, and who know the knowledge, thoughtfulness, and caution, which are needful in such a task, are naturally exposed. For us, who can only decide on such a subject by the general analogies of the history of science, it may suffice to say, that it appears doubtful whether the fundamental conceptions of affinity, analogy, transition, and developement, have yet been fixed in the minds of physiologists with sufficient firmness and clearness, or unfolded with sufficient consistency and generality, to make it likely that any great additional step of this kind can for some time be made.

We have here considered the doctrine of the identity of the seemingly various types of animal structure, as an attempt to extend the correspondencies which were the basis of Cuvier's division of the animal kingdom. But this doctrine has been put forward in another point of view, as the antithesis to the doctrine of final causes. This question is so important a one, that we cannot help attempting to give some view of its state and bearings.

VIII. THE DOCTRINE OF FINAL CAUSES IN PHYSIOLOGY

Sect. 1.--Assertion of the Principle of Unity of Plan.

WE have repeatedly seen, in the course of our historical view of Physiology, that those who have studied the structure of animals and plants, have had a conviction forced upon them, that the organs are constructed and combined in subservience to the life and functions of the whole. The parts have a purpose, as well as a law;--we can trace Final Causes, as well as Laws of Causation. This principle is peculiar to physiology; and it might naturally be expected that, in the progress of the science, it would come under special consideration. This accordingly has happened; and the principle has been drawn {483} into a prominent position by the struggle of two antagonistic schools of physiologists. On the one hand, it has been maintained that this doctrine of final causes is altogether unphilosophical, and requires to be replaced by a more comprehensive and profound principle: on the other hand, it is asserted that the doctrine is not only true, but that, in our own time, it has been fixed and developed so as to become the instrument of some of the most important discoveries which have been made. Of the views of these two schools we must endeavor to give some account.

The disciples of the former of the two schools express their tenets by the phrases unity of plan, unity of composition; and the more detailed developement of these doctrines has been termed the Theory of Analogies, by Geoffroy Saint-Hilaire, who claims this theory as his own creation. According to this theory, the structure and functions of animals are to be studied by the guidance of their analogy only; our attention is to be turned, not to the fitness of the organization for any end of life or action, but to its resemblance to other organizations by which it is gradually derived from the original type.

According to the rival view of this subject, we must not assume, and cannot establish, that the plan of all animals is the same, or their composition similar. The existence of a single and universal system of analogies in the construction of all animals is entirely unproved, and therefore cannot be made our guide in the study of their properties. On the other hand, the plan of the animal, the purpose of its organization in the support of its life, the necessity of the functions to its existence, are truths which are irresistibly apparent, and which may therefore be safely taken as the bases of our reasonings. This view has been put forward as the doctrine of the conditions of existence: it may also be described as the principle of a purpose in organization; the structure being considered as having the function for its end. We must say a few words on each of these views.

It had been pointed out by Cuvier, as we have seen in the last chapter, that the animal kingdom may be divided into four great branches; in each of which the plan of the animal is different, namely, vertebrata, articulata, mollusca, radiata. Now the question naturally occurs, is there really no resemblance of construction in these different classes? It was maintained by some, that there is such a resemblance. In 1820,[105\17] M. Audouin, a young naturalist of Paris, {484} endeavored to fill up the chasm which separates insects from other animals; and by examining carefully the portions which compose the solid frame-work of insects, and following them through their various transformations in different classes, he conceived that he found relations of position and function, and often of number and form, which might be compared with the relations of the parts of the skeleton in vertebrate animals. He thought that the first segment of an insect, the head,[106\17] represents one of the three vertebræ which, according to Spix and others, compose the vertebrate head: the second segment of the insects, (the prothorax of Audouin,) is, according to M. Geoffroy, the second vertebra of the head of the vertebrata, and so on. Upon this speculation Cuvier[107\17] does not give any decided opinion; observing only, that even if false, it leads to active thought and useful research.

[Note 105\17: Cuv. Hist. Sc. Nat. iii. 422.]

[Note 106\17: Ib. 437.]

[Note 107\17: Cuv. Hist. Sc. Nat. iii. 441.]

But when an attempt was further made to identify the plan of another branch of the animal world, the mollusca, with that of the vertebrata, the radical opposition between such views and those of Cuvier, broke out into an animated controversy.

Two French anatomists, MM. Laurencet and Meyranx, presented to the Academy of Sciences, in 1830, a Memoir containing their views on the organization of molluscous animals; and on the sepia or cuttle-fish in particular, as one of the most complete examples of such animals. These creatures, indeed, though thus placed in the same division with shell-fish of the most defective organization and obscure structure, are far from being scantily organized. They have a brain,[108\17] often eyes, and these, in the animals of this class, (cephalopoda) are more complicated than in any vertebrates;[109\17] they have sometimes ears, salivary glands, multiple stomachs, a considerable liver, a bile, a complete double circulation, provided with auricles and ventricles; in short, their vital activity is vigorous, and their senses are distinct.

[Note 108\17: Geoffroy Saint-Hilaire denies this. _Principes de Phil. Zoologique discutés en_ 1830, p. 68.]

[Note 109\17: Geoffroy Saint-Hilaire, Principes de Phil. Zoologique discutés en 1830, p. 55.]

But still, though this organization, in the abundance and diversity of its parts, approaches that of vertebrate animals, it had not been considered as composed in the same manner, or arranged in the same order, Cuvier had always maintained that the plan of molluscs is not a continuation of the plan of vertebrates. {485}

MM. Laurencet and Meyranx, on the contrary, conceived that the sepia might be reduced to the type of a vertebrate creature, by considering the back-bone of the latter bent double backwards, so as to bring the root of the tail to the nape of the neck; the parts thus brought into contact being supposed to coalesce. By this mode of conception, these anatomists held that the viscera were placed in the same connexion as in the vertebrate type, and the functions exercised in an analogous manner.

To decide on the reality of the analogy thus asserted, clearly belonged to the jurisdiction of the most eminent anatomists and physiologists. The Memoir was committed to Geoffroy Saint-Hilaire and Latreille, two eminent zoologists, in order to be reported on. Their report was extremely favorable; and went almost to the length of adopting the views of the authors.

Cuvier expressed some dissatisfaction with this report on its being read;[110\17] and a short time afterwards,[111\17] represented Geoffroy Saint-Hilaire as having asserted that the new views of Laurencet and Meyranx refuted completely the notion of the great interval which exists between molluscous and vertebrate animals. Geoffroy protested against such an interpretation of his expressions; but it soon appeared, by the controversial character which the discussions on this and several other subjects assumed, that a real opposition of opinions was in action.

[Note 110\17: Princ. de Phil. Zool. discutés en 1830, p. 36.]

[Note 111\17: p. 50.]

Without attempting to explain the exact views of Geoffroy, (we may, perhaps, venture to say that they are hardly yet generally understood with sufficient distinctness to justify the mere historian of science in attempting such an explanation,) their general tendency may be sufficiently collected from what has been said; and from the phrases in which his views are conveyed.[112\17] The principle of connexions, the elective affinities of organic elements, the equilibrization of organs;--such are the designations of the leading doctrines which are unfolded in the preliminary discourse of his Anatomical Philosophy. Elective affinities of organic elements are the forces by which the vital structures and varied forms of living things are produced; and the principles of connexion and equilibrium of these forces in the various parts of the organization prescribe limits and conditions to the variety and developement of such forms.

[Note 112\17: Phil. Zool. 15.]

The character and tendency of this philosophy will be, I think, {486} much more clear, if we consider what it excludes and denies. It rejects altogether all conception of a plan and purpose in the organs of animals, as a principle which has determined their forms, or can be of use in directing our reasonings. "I take care," says Geoffroy, "not to ascribe to God any intention."[113\17] And when Cuvier speaks of the combination of organs in such order that they may be in consistence with the part which the animal has to play in nature; his rival rejoins,[114\17] I "know nothing of animals which have to play a part in nature." Such a notion is, he holds, unphilosophical and dangerous. It is an abuse of final causes which makes the cause to be engendered by the effect. And to illustrate still further his own view, he says, "I have read concerning fishes, that because they live in a medium which resists more than air, their motive forces are calculated so as to give them the power of progression under those circumstances. By this mode of reasoning, you would say of a man who makes use of crutches, that he was originally destined to the misfortune of having a leg paralysed or amputated."

[Note 113\17: "Je me garde de prêter à Dieu aucune intention." Phil. Zool. 10.]

[Note 114\17: "Je ne connais point d'animal qui DOIVE jouer un rôle dans la nature." p. 65.]

How far this doctrine of unity in the plan in animals, is admissible or probable in physiology when kept within proper limits, that is, when not put in opposition to the doctrine of a purpose involved in the plan of animals, I do not pretend even to conjecture. The question is one which appears to be at present deeply occupying the minds of the most learned and profound physiologists; and such persons alone, adding to their knowledge and zeal, judicial sagacity and impartiality, can tell us what is the general tendency of the best researches on this subject.[115\17] But when the anatomist expresses such opinions, and defends them by such illustrations as those which I have just quoted,[116\17] we perceive that he quits the entrenchments of his superior science, in which he might {487} have remained unassailable so long as the question was a professional one; and the discussion is open to those who possess no peculiar knowledge of anatomy. We shall, therefore, venture to say a few words upon it.

[Note 115\17: So far as this doctrine is generally accepted among the best physiologists, we cannot doubt the propriety of Meckel's remark, (Comparative Anatomy, 1821, Pref. p. xi.) that it cannot be truly asserted either to be new, or to be peculiarly due to Geoffroy Saint-Hilaire.]

[Note 116\17: It is hardly worth while answering such illustrations, but I may remark, that the one quoted above, irrelevant and unbecoming as it is, tells altogether against its author. The fact that the wooden leg is of the same length as the other, proves, and would satisfy the most incredulous man, that it was intended for walking.]

Sect. 2.--Estimate of the Doctrine of Unity of Plan.

IT has been so often repeated, and so generally allowed in modern times, that Final Causes ought not to be made our guides in natural philosophy, that a prejudice has been established against the introduction of any views to which this designation can be applied, into physical speculations. Yet, in fact, the assumption of an end or purpose in the structure of organized beings, appears to be an intellectual habit which no efforts can cast off. It has prevailed from the earliest to the latest ages of zoological research; appears to be fastened upon us alike by our ignorance and our knowledge; and has been formally accepted by so many great anatomists, that we cannot feel any scruple in believing the rejection of it to be the superstition of a false philosophy, and a result of the exaggeration of other principles which are supposed capable of superseding its use. And the doctrine of unity of plan of all animals, and the other principles associated with this doctrine, so far as they exclude the conviction of an intelligible scheme and a discoverable end, in the organization of animals, appear to be utterly erroneous. I will offer a few reasons for an opinion which may appear presumptuous in a writer who has only a general knowledge of the subject.

1. In the first place, it appears to me that the argumentation on the case in question, the Sepia, does by no means turn out to the advantage of the new hypothesis. The arguments in support of the hypothetical view of the structure of this mollusc were, that by this view the relative position of the parts was explained, and confirmations which had appeared altogether anomalous, were reduced to rule; for example, the beak, which had been supposed to be in a position the reverse of all other beaks, was shown, by the assumed posture, to have its upper mandible longer than the lower, and thus to be regularly placed. "But," says Cuvier,[117\17] "supposing the posture, in order that the side on which the funnel of the sepia is folded should be the back of the animal, considered as similar to a vertebrate, the brain with {488} regard to the beak, and the œsophagus with regard to the liver, should have positions corresponding to those in vertebrates; but the positions of these organs are exactly contrary to the hypothesis. How, then, can you say," he asks, "that the cephalopods and vertebrates have identity of composition, unity of composition, without using words in a sense entirely different from their common meaning?"

[Note 117\17: G. S. H. Phil. Zool. p. 70.]

This argument appears to be exactly of the kind on which the value of the hypothesis must depend.[118\17] It is, therefore, interesting to see the reply made to it by the theorist. It is this: "I admit the facts here stated, but I deny that they lead to the notion of a different sort of animal composition. Molluscous animals had been placed too high in the zoological scale; but if they are only the embryos of its lower stages, if they are only beings in which far fewer organs come into play, it does not follow that the organs are destitute of the relations which the power of successive generations may demand. The organ A will be in an unusual relation with the organ C, if B has not been produced;--if a stoppage of the developement has fallen upon this latter organ, and has thus prevented its production. And thus," he says, "we see how we may have different arrangements, and divers constructions as they appear to the eye."

[Note 118\17: I do not dwell on other arguments which were employed. It was given as a circumstance suggesting the supposed posture of the type, that in this way the back was colored, and the belly was white. On this Cuvier observes (Phil. Zool. pp. 93, 68), "I must say, that I do not know any naturalist so ignorant as to suppose that the back is determined by its dark color, or even by its position when the animal is in motion; they all know that the badger has a black belly and a white back; that an infinity of other animals, especially among insects, are in the same case; and that many fishes swim on their side, or with their belly upwards."]

It seems to me that such a concession as this entirely destroys the theory which it attempts to defend; for what arrangement does the principle of unity of composition exclude, if it admits unusual, that is, various arrangements of some organs, accompanied by the total absence of others? Or how does this differ from Cuvier's mode of stating the conclusion, except in the introduction of certain arbitrary hypotheses of developement and stoppage? "I reduce the facts," Cuvier says, "to their true expression, by saying that Cephalopods have several organs which are common to them and vertebrates, and which discharge the same offices; but that these organs are in them differently distributed, and often constructed in a different manner; {489} and they are accompanied by several other organs which vertebrates have not; while these on the other hand have several which are wanting in cephalopods."

We shall see afterwards the general principles which Cuvier himself considered as the best guides in these reasonings. But I will first add a few words on the disposition of the school now under consideration, to reject all assumption of an end.

2. That the parts of the bodies of animals are made in order to discharge their respective offices, is a conviction which we cannot believe to be otherwise than an irremovable principle of the philosophy of organization, when we see the manner in which it has constantly forced itself upon the minds of zoologists and anatomists in all ages; not only as an inference, but as a guide whose indications they could not help following. I have already noticed expressions of this conviction in some of the principal persons who occur in the history of physiology, as Galen and Harvey. I might add many more, but I will content myself with adducing a contemporary of Geoffroy's whose testimony is the more remarkable, because he obviously shares with his countryman in the common prejudice against the use of final causes. "I consider," he says, in speaking of the provisions for the reproduction of animals,[119\17] "with the great Bacon, the philosophy of final causes as sterile; but I have elsewhere acknowledged that it was very difficult for the most cautious man never to have recourse to them in his explanations." After the survey which we have had to take of the history of physiology, we cannot but see that the assumption of final causes in this branch of science is so far from being sterile, that it has had a large share in every discovery which is included in the existing mass of real knowledge. The use of every organ has been discovered by starting from the assumption that it must have some use. The doctrine of the circulation of the blood was, as we have seen, clearly and professedly due to the persuasion of a purpose in the circulatory apparatus. The study of comparative anatomy is the study of the adaption of animal structures to their purposes. And we shall soon have to show that this conception of final causes has, in our own times, been so far from barren, that it has, in the hands of Cuvier and others, enabled us to become intimately acquainted with vast departments of zoology to which we have no other mode of access. It has placed before us in a complete state, {490} animals, of which, for thousands of years, only a few fragments have existed, and which differ widely from all existing animals; and it has given birth, or at least has given the greatest part of its importance and interest, to a science which forms one of the brightest parts of the modern progress of knowledge. It is, therefore, very far from being a vague and empty assertion, when we say that final causes are a real and indestructible element in zoological philosophy; and that the exclusion of them, as attempted by the school of which we speak, is a fundamental and most mischievous error.

[Note 119\17: Cabanis, Rapports du Physique et du Morale de l'Homme, i. **299.]

3. Thus, though the physiologist may persuade himself that he ought not to refer to final causes, we find that, practically, he cannot help doing this; and that the event shows that his practical habit is right and well-founded. But he may still cling to the speculative difficulties and doubts in which such subjects may be involved by à priori considerations. He may say, as Saint-Hilaire does say,[120\17] "I ascribe no intention to God, for I mistrust the feeble powers of my reason. I observe facts merely, and go no further. I only pretend to the character of the historian of what is." "I cannot make Nature an intelligent being who does nothing in vain, who acts by the shortest mode, who does all for the best."

[Note 120\17: Phil. Zool. p. 10.]

I am not going to enter at any length into this subject, which, thus considered, is metaphysical and theological, rather than physiological. If any one maintain, as some have maintained, that no manifestation of means apparently used for ends in nature, can prove the existence of design in the Author of nature, this is not the place to refute such an opinion in its general form. But I think it may be worth while to show, that even those who incline to such an opinion, still cannot resist the necessity which compels men to assume, in organized beings, the existence of an end.

Among the philosophers who have referred our conviction of the being of God to our moral nature, and have denied the possibility of demonstration on mere physical grounds, Kant is perhaps the most eminent. Yet he has asserted the reality of such a principle of physiology as we are now maintaining in the most emphatic manner. Indeed, this assumption of an end makes his very definition of an organized being. "An organized product of nature is that in which all the parts are mutually ends and means."[121\17] And this, he says, is a universal and necessary maxim. He adds, "It is well known that the {491} anatomizers of plants and animals, in order to investigate their structure, and to obtain an insight into the grounds why and to what end such parts, why such a situation and connexion of the parts, and exactly such an internal form, come before them, assume, as indispensably necessary, this maxim, that in such a creature nothing is in vain, and proceed upon it in the same way in which in general natural philosophy we proceed upon the principle that nothing happens by chance. In fact, they can as little free themselves from this teleological principle as from the general physical one; for as, on omitting the latter, no experience would be possible, so on omitting the former principle, no clue could exist for the observation of a kind of natural objects which can be considered teleologically under the conception of natural ends."

[Note 121\17: Urtheilskraft, p. 296.]

Even if the reader should not follow the reasoning of this celebrated philosopher, he will still have no difficulty in seeing that he asserts, in the most distinct manner, that which is denied by the author whom we have before quoted, the propriety and necessity of assuming the existence of an end as our guide in the study of animal organization.

4. It appears to me, therefore, that whether we judge from the arguments, the results, the practice of physiologists, their speculative opinions, or those of the philosophers of a wider field, we are led to the same conviction, that in the organized world we may and must adopt the belief that organization exists for its purpose, and that the apprehension of the purpose may guide us in seeing the meaning of the organization. And I now proceed to show how this principle has been brought into additional clearness and use by Cuvier.

In doing this, I may, perhaps, be allowed to make a reflection of a kind somewhat different from the preceding remarks, though suggested by them. In another work,[122\17] I endeavored to show that those who have been discoverers in science have generally had minds, the disposition of which was to believe in an intelligent Maker of the universe; and that the scientific speculations which produced an opposite tendency, were generally those which, though they might deal familiarly with known physical truths, and conjecture boldly with regard to the unknown, did not add to the number of solid generalizations. In order to judge whether this remark is distinctly applicable in the case now considered, I should have to estimate Cuvier in comparison with other physiologists of his time, which I do not presume to do. But I may {492} observe, that he is allowed by all to have established, on an indestructible basis, many of the most important generalizations which zoology now contains; and the principal defect which his critics have pointed out, has been, that he did not generalize still more widely and boldly. It appears, therefore, that he cannot but be placed among the great discoverers in the studies which he pursued; and this being the case, those who look with pleasure on the tendency of the thoughts of the greatest men to an Intelligence far higher than their own, most be gratified to find that he was an example of this tendency; and that the acknowledgement of a creative purpose, as well as a creative power, not only entered into his belief but made an indispensable and prominent part of his philosophy.

[Note 122\17: Bridgewater Treatise, B. iii. c. vii. and viii. On Inductive Habits of Thought, and on Deductive Habits of Thought.]

Sect. 3.--Establishment and Application of the Principle of the Conditions of Existence of Animals.--Cuvier.

WE have now to describe more in detail the doctrine which Cuvier maintained in opposition to such opinions as we have been speaking of; and which, in his way of applying it, we look upon as a material advance in physiological knowledge, and therefore give to it a distinct place in our history. "Zoology has," he says,[123\17] in the outset of his Règne Animal, "a principle of reasoning which is peculiar to it, and which it employs with advantage on many occasions: this is the principle of the Conditions of Existence, vulgarly the principle of Final Causes. As nothing can exist if it do not combine all the conditions which render its existence possible, the different parts of each being must be co-ordinated in such a manner as to render the total being possible, not only in itself, but in its relations to those which surround it; and the analysis of these conditions often leads to general laws, as clearly demonstrated as those which result from calculation or from experience."

[Note 123\17: Règne An. p. 6.]

This is the enunciation of his leading principle in general terms. To our ascribing it to him, some may object on the ground of its being self-evident in its nature,[124\17] and having been very anciently applied. But to this we reply, that the principle must be considered as a real discovery in the hands of him who first shows how to make it an instrument of other discoveries. It is true, in other cases as well as in this, that some vague apprehension, of true general principles, such as à {493} priori considerations can supply, has long preceded the knowledge of them as real and verified laws. In such a way it was seen, before Newton, that the motions of the planets must result from attraction; and so, before Dufay and Franklin, it was held that electrical actions must result from a fluid. Cuvier's merit consisted, not in seeing that an animal cannot exist without combining all the conditions of its existence; but in perceiving that this truth may be taken as a guide in our researches concerning animals;--that the mode of their existence may be collected from one part of their structure, and then applied to interpret or detect another part. He went on the supposition not only that animal forms have some plan, some purpose, but that they have an intelligible plan, a discoverable purpose. He proceeded in his investigations like the decipherer of a manuscript, who makes out his alphabet from one part of the context, and then applies it to read the rest. The proof that his principle was something very different from an identical proposition, is to be found in the fact, that it enabled him to understand and arrange the structures of animals with unprecedented clearness and completeness of order; and to restore the forms of the extinct animals which are found in the rocks of the earth, in a manner which has been universally assented to as irresistibly convincing. These results cannot flow from a trifling or barren principle; and they show us that if we are disposed to form such a judgment of Cuvier's doctrine, it must be because we do not fully apprehend its import.

[Note 124\17: Swainson. Study of Nat. Hist. p. 85.]

To illustrate this, we need only quote the statement which he makes, and the uses to which he applies it. Thus in the Introduction to his great work on Fossil Remains he says, "Every organized being forms an entire system of its own, all the parts of which mutually correspond, and concur to produce a certain definite purpose by reciprocal reaction, or by combining to the same end. Hence none of these separate parts can change their forms without a corresponding change in the other parts of the same animal; and consequently each of these parts, taken separately, indicates all the other parts to which it has belonged. Thus, if the viscera of an animal are so organized as only to be fitted for the digestion of recent flesh, it is also requisite that the jaws should be so constructed as to fit them for devouring prey; the claws must be constructed for seizing it and tearing it to pieces; the teeth for cutting and dividing its flesh; the entire system of the limbs or organs of motion for pursuing and overtaking it; and the organs of sense for discovering it at a distance. Nature must also have endowed the brain of the animal with instincts sufficient for concealing itself and for laying plans to {494} catch its necessary victims."[125\17] By such considerations he has been able to reconstruct the whole of many animals of which parts only were given;--a positive result, which shows both the reality and the value of the truth on which he wrought.

[Note 125\17: Theory of the Earth, p. 90.]

Another great example, equally showing the immense importance of this principle in Cuvier's hands, is the reform which, by means of it, he introduced into the classification of animals. Here again we may quote the view he himself has given[126\17] of the character of his own improvements. In studying the physiology of the natural classes of vertebrate animals, he found, he says, "in the respective quantity of their respiration, the reason of the quantity of their motion, and consequently of the kind of locomotion. This, again, furnishes the reason for the forms of their skeletons and muscles; and the energy of their senses, and the force of their digestion, are in a necessary proportion to the same quantity. Thus a division which had till then been established, like that of vegetables, only upon observation, was found to rest upon causes appreciable, and applicable to other cases." Accordingly, he applied this view to invertebrates;--examined the modifications which take place in their organs of circulation, respiration, and sensation; and having calculated the necessary results of these modifications, he deduced from it a new division of those animals, in which they are arranged according to their true relations.

[Note 126\17: Hist. Sc. Nat. i. 293.]

Such have been some of the results of the principle of the Conditions of Existence, as applied by its great assertor.

It is clear, indeed, that such a principle could acquire its practical value only in the hands of a person intimately acquainted with anatomical details, with the functions of the organs, and with their variety in different animals. It is only by means of such nutriment that the embryo truth could be developed into a vast tree of science. But it is not the less clear, that Cuvier's immense knowledge and great powers of thought led to their results, only by being employed under the guidance of this master-principle: and, therefore, we may justly consider it as the distinctive feature of his speculations, and follow it with a gratified eye, as the thread of gold which runs through, connects, and enriches his zoological researches:--gives them a deeper interest and a higher value than can belong to any view of the organical sciences, in which the very essence of organization is kept out of sight. {495}

The real philosopher, who knows that all the kinds of truth are intimately connected, and that all the best hopes and encouragements which are granted to our nature must be consistent with truth, will be satisfied and confirmed, rather than surprised and disturbed, thus to find the Natural Sciences leading him to the borders of a higher region. To him it will appear natural and reasonable, that after journeying so long among the beautiful and orderly laws by which the universe is governed, we find ourselves at last approaching to a Source of order and law, and intellectual beauty:--that, after venturing into the region of life and feeling and will, we are led to believe the Fountain of life and will not to be itself unintelligent and dead, but to be a living Mind, a Power which aims as well as acts. To us this doctrine appears like the natural cadence of the tones to which we have so long been listening; and without such a final strain our ears would have been left craving and unsatisfied. We have been lingering long amid the harmonies of law and symmetry, constancy and development; and these notes, though their music was sweet and deep, must too often have sounded to the ear of our moral nature, as vague and unmeaning melodies, floating in the air around us, but conveying no definite thought, moulded into no intelligible announcement. But one passage which we have again and again caught by snatches, though sometimes interrupted and lost, at last swells in our ears full, clear, and decided; and the religious "Hymn in honor of the Creator," to which Galen so gladly lent his voice, and in which the best physiologists of succeeding times have ever joined, is filled into a richer and deeper harmony by the greatest philosophers of these later days, and will roll on hereafter the "perpetual song" of the temple of science.

{{497}} BOOK XVIII.

THE PALÆTIOLOGICAL SCIENCES.

HISTORY OF GEOLOGY.

Di quibus imperium est animarum, Umbræque silentes, Et Chaos, et Phlegethon, loca nocte silentia late, Sit mihi fas audita loqui; sit, numine vestro Pandere res alta terrâ et caligine mersas. VIRGIL. Æn. vi. 264.

Ye Mighty Ones, who sway the Souls that go Amid the marvels of the world below! Ye, silent Shades, who sit and hear around! Chaos! and Streams that burn beneath the ground! All, all forgive, if by your converse stirred, My lips shall utter what my ears have heard; If I shall speak of things of doubtful birth, Deep sunk in darkness, as deep sunk in earth.

{{499}} INTRODUCTION.

Of the Palætiological Sciences.

WE now approach the last Class of Sciences which enter into the design of the present work; and of these, Geology is the representative, whose history we shall therefore briefly follow. By the Class of Sciences to which I have referred it, I mean to point out those researches in which the object is, to ascend from the present state of things to a more ancient condition, from which the present is derived by intelligible causes.

The sciences which treat of causes have sometimes been termed ætiological, from αἰτία, a cause: but this term would not sufficiently describe the speculations of which we now speak; since it might include sciences which treat of Permanent Causality, like Mechanics, as well as inquiries concerning Progressive Causation. The investigations which I now wish to group together, deal, not only with the possible, but with the actual past; and a portion of that science on which we are about to enter, Geology, has properly been termed Palæontology, since it treats of beings which formerly existed.[1\18] Hence, combining these two notions,[2\18] Palætiology appears to be a term not inappropriate, to describe those speculations which thus refer to actual past events, and attempt to explain them by laws of causation.

[Note 1\18: Πάλαι, ὄντα]

[Note 2\18: Πάλαι, αἰτία]

Such speculations are not confined to the world of inert matter; we have examples of them in inquiries concerning the monuments of the art and labor of distant ages; in examinations into the origin and early progress of states and cities, customs and languages; as well as in researches concerning the causes and formations of mountains and rocks, the imbedding of fossils in strata, and their elevation from the bottom of the ocean. All these speculations are connected by this bond,--that they endeavor to ascend to a past state of things, by the aid of the evidence of the present. In asserting, with Cuvier, that {500} "The geologist is an antiquary of a new order," we do not mark a fanciful and superficial resemblance of employment merely, but a real and philosophical connexion of the principles of investigation. The organic fossils which occur in the rock, and the medals which we find in the ruins of ancient cities, are to be studied in a similar spirit and for a similar purpose. Indeed, it is not always easy to know where the task of the geologist ends, and that of the antiquary begins. The study of ancient geography may involve us in the examination of the causes by which the forms of coasts and plains are changed; the ancient mound or scarped rock may force upon us the problem, whether its form is the work of nature or of man; the ruined temple may exhibit the traces of time in its changed level, and sea-worn columns; and thus the antiquarian of the earth may be brought into the very middle of the domain belonging to the antiquarian of art.

Such a union of these different kinds of archæological investigations has, in fact, repeatedly occurred. The changes which have taken place in the temple of Jupiter Serapis, near Puzzuoli, are of the sort which have just been described; and this is only one example of a large class of objects;--the monuments of art converted into records of natural events. And on a wider scale, we find Cuvier, in his inquiries into geological changes, bringing together historical and physical evidence. Dr. Prichard, in his Researches into the Physical History of Man, has shown that to execute such a design as his, we must combine the knowledge of the physiological laws of nature with the traditions of history and the philosophical comparison of languages. And even if we refuse to admit, as part of the business of geology, inquiries concerning the origin and physical history of the present population of the globe; still the geologist is compelled to take an interest in such inquiries, in order to understand matters which rigorously belong to his proper domain; for the ascertained history of the present state of things offers the best means of throwing light upon the causes of past changes. Mr. Lyell quotes Dr. Prichard's book more frequently than any geological work of the same extent.

Again, we may notice another common circumstance in the studies which we are grouping together as palætiological, diverse as they are in their subjects. In all of them we have the same kind of manifestations of a number of successive changes, each springing out of a preceding state; and in all, the phenomena at each step become more and more complicated, by involving the results of all that has preceded, modified by supervening agencies. The general aspect of all these {501} trains of change is similar, and offers the same features for description. The relics and ruins of the earlier states are preserved, mutilated and dead, in the products of later times. The analogical figures by which we are tempted to express this relation are philosophically true. It is more than a mere fanciful description, to say that in languages, customs, forms of Society, political institutions, we see a number of formations super-imposed upon one another, each of which is, for the most part, an assemblage of fragments and results of the preceding condition. Though our comparison might be bold, it would be just, if we were to assert, that the English language is a conglomerate of Latin words, bound together in a Saxon cement; the fragments of the Latin being partly portions introduced directly from the parent quarry, with all their sharp edges, and partly pebbles of the same material, obscured and shaped by long rolling in a Norman or some other channel. Thus the study of palætiology in the materials of the earth, is only a type of similar studies with respect to all the elements, which, in the history of the earth's inhabitants, have been constantly undergoing a series of connected changes.

But, wide as is the view which such considerations give us of the class of sciences to which geology belongs, they extend still further. "The science of the changes which have taken place in the organic kingdoms of nature," (such is the description which has been given of Geology,[3\18]) may, by following another set of connexions, be extended beyond "the modifications of the surface of our own planet." For we cannot doubt that some resemblance of a closer or looser kind, has obtained between the changes and causes of change, on other bodies of the universe, and on our own. The appearances of something of the kind of volcanic action on the surface of the moon, are not to be mistaken. And the inquiries concerning the origin of our planet and of our solar system, inquiries to which Geology irresistibly impels her students, direct us to ask what information the rest of the universe can supply, bearing upon this subject. It has been thought by some, that we can trace systems, more or less like our solar system, in the process of formation; the nebulous matter, which is at first expansive and attenuated, condensing gradually into suns and planets. Whether this Nebular Hypothesis be tenable or not, I shall not here inquire; but the discussion of such a question would be closely connected with {502} geology, both in its interests and in its methods. If men are ever able to frame a science of the past changes by which the universe has been brought into its present condition, this science will be properly described as Cosmical Palætiology.

[Note 3\18: Lyell, Principles of Geology, p. 1.]

These palætiological sciences might properly be called historical, if that term were sufficiently precise: for they are all of the nature of history, being concerned with the succession of events: and the part of history which deals with the past causes of events, is, in fact, a moral palætiology. But the phrase Natural History has so accustomed us to a use of the word history in which we have nothing to do with time, that, if we were to employ the word historical to describe the palætiological sciences, it would be in constant danger of being misunderstood. The fact is, as Mohs has said, that Natural History, when systematically treated, rigorously excludes all that is historical; for it classes objects by their permanent and universal properties, and has nothing to do with the narration of particular and casual facts. And this is an inconsistency which we shall not attempt to rectify.

All palætiological sciences, since they undertake to refer changes to their causes, assume a certain classification of the phenomena which change brings forth, and a knowledge of the operation of the causes of change. These phenomena, these causes, are very different, in the branches of knowledge which I have thus classed together. The natural features of the earth's surface, the works of art, the institutions of society, the forms of language, taken together, are undoubtedly a very wide collection of subjects of speculation; and the kinds of causation which apply to them are no less varied. Of the causes of change in the inorganic and organic world,--the peculiar principles of Geology--we shall hereafter have to speak. As these must be studied by the geologist, so, in like manner, the tendencies, instincts, faculties, principles, which direct man to architecture and sculpture, to civil government, to rational and grammatical speech, and which have determined the circumstances of his progress in these paths, must be in a great degree known to the Palætiologist of Art, of Society, and of Language, respectively, in order that he may speculate soundly upon his peculiar subject. With these matters we shall not here meddle, confining ourselves, in our exemplification of the conditions and progress of such sciences, to the case of Geology.

The journey of survey which we have attempted to perform over the field of human knowledge, although carefully directed according to the paths and divisions of the physical sciences, has already {503} conducted us to the boundaries of physical science, and gives us a glimpse of the region beyond. In following the history of Life, we found ourselves led to notice the perceptive and active faculties of man; it appeared that there was a ready passage from physiology to psychology, from physics to metaphysics. In the class of sciences now under notice, we are, at a different point, carried from the world of matter to the world of thought and feeling,--from things to men. For, as we have already said, the science of the causes of change includes the productions of Man as well as of Nature. The history of the earth, and the history of the earth's inhabitants, as collected from phenomena, are governed by the same principles. Thus the portions of knowledge which seek to travel back towards the origin, whether of inert things or of the works of man, resemble each other. Both of them treat of events as connected by the thread of time and causation. In both we endeavor to learn accurately what the present is, and hence what the past has been. Both are historical sciences in the same sense.

It must be recollected that I am now speaking of history as ætiological;--as it investigates causes, and as it does this in a scientific, that is, in a rigorous and systematic, manner. And I may observe here, though I cannot now dwell on the subject, that all ætiological sciences will consist of three portions; the Description of the facts and phenomena;--the general Theory of the causes of change appropriate to the case;--and the Application of the theory to the facts. Thus, taking Geology for our example, we must have, first Descriptive or Phenomenal Geology; next, the exposition of the general principles by which such phenomena can be produced, which we may term Geological Dynamics; and, lastly, doctrines hence derived, as to what have been the causes of the existing state of things, which we may call Physical Geology.

These three branches of geology may be found frequently or constantly combined in the works of writers on the subject, and it may not always be easy to discriminate exactly what belongs to each subject.[4\18] But the analogy of this science with others, its present {504} condition and future fortunes, will derive great illustration from such a distribution of its history; and in this point of view, therefore, we shall briefly treat of it; dividing the history of Geological Dynamics, for the sake of convenience, into two Chapters, one referring to inorganic, and one to organic, phenomena.

[Note 4\18: The Wernerians, in distinguishing their study from Geology, and designating it as Geognosy, the knowledge of the earth, appear to have intended to select Descriptive Geology for their peculiar field. In like manner, the original aim of the Geological Society of London, which was formed (1807) "with a view to record and multiply observations," recognized the possibility of a Descriptive Geology separate from the other portions of the science.]

{{505}} DESCRIPTIVE GEOLOGY.

I. PRELUDE TO SYSTEMATIC DESCRIPTIVE GEOLOGY

Sect. 1.--Ancient Notices of Geological Facts.

THE recent history of Geology, as to its most important points, is bound up with what is doing at present from day to day; and that portion of the history of the science which belongs to the past, has been amply treated by other writers.[5\18] I shall, therefore, pass rapidly over the series of events of which this history consists; and shall only attempt to mention what may seem to illustrate and confirm my own view of its state and principles.

[Note 5\18: As MM. Lyell, Fitton, Conybeare, in our own country.]

Agreeably to the order already pointed out, I shall notice, in the first place, Phenomenal Geology, or the description of the facts, as distinct from the inquiry into their causes. It is manifest that such a merely descriptive kind of knowledge may exist; and it probably will not be contested, that such knowledge ought to be collected, before we attempt to frame theories concerning the causes of the phenomena. But it must be observed, that we are here speaking of the formation of a science; and that it is not a collection of miscellaneous, unconnected, unarranged knowledge that can be considered as constituting science; but a methodical, coherent, and, as far as possible, complete body of facts, exhibiting fully the condition of the earth as regards those circumstances which are the subject matter of geological speculation. Such a Descriptive Geology is a pre-requisite to Physical Geology, just as Phenomenal Astronomy necessarily preceded Physical Astronomy, or as Classificatory Botany is a necessary accompaniment to Botanical Physiology. We may observe also that Descriptive Geology, such as we now speak of, is one of the classificatory sciences, like {506} Mineralogy or Botany: and will be found to exhibit some of the features of that class of sciences.

Since, then, our History of Descriptive Geology is to include only systematic and scientific descriptions of the earth or portions of it, we pass over, at once, all the casual and insulated statements of facts, though they may be geological facts, which occur in early writers; such, for instance, as the remark of Herodotus,[6\18] that there are shells in the mountains of Egypt; or the general statements which Ovid puts in the mouth of Pythagoras:[7\18] Vidi ego quod fuerat solidissima tellus, Esse fretum; vidi factas ex æquore terras, Et procul a pelago conchæ jacuere marinæ.

[Note 6\18: ii. 12.]

[Note 7\18: Met. xv. 262.]

We may remark here already how generally there are mingled with descriptive notices of such geological facts, speculations concerning their causes. Herodotus refers to the circumstance just quoted, for the purpose of showing that Egypt was formerly a gulf of the sea; and the passage of the Roman poet is part of a series of exemplifications which he gives of the philosophical tenet, that nothing perishes but everything changes. It will be only by constant attention that we shall be able to keep our provinces of geology distinct.

Sect. 2.--Early Descriptions and Collections of Fossils.

IF we look, as we have proposed to do, for systematic and exact knowledge of geological facts, we find nothing which we can properly adduce till we come to modern times. But when facts such as those already mentioned, (that sea-shells and other marine objects are found imbedded in rocks,) and other circumstances in the structure of the Earth, had attracted considerable attention, the exact examination, collection, and record of these circumstances began to be attempted. Among such steps in Descriptive Geology, we may notice descriptions and pictures of fossils, descriptions of veins and mines, collections of organic and inorganic fossils, maps of the mineral structure of countries, and finally, the discoveries concerning the superposition of strata, the constancy of their organic contents, their correspondence in different countries, and such great general relations of the materials and features of the earth as have been discovered up to the present time. {507} Without attempting to assign to every important advance its author, I shall briefly exemplify each of the modes of contributing to descriptive geology which I have just enumerated.

The study of organic fossils was first pursued with connexion and system in Italy. The hills which on each side skirt the mountain-range of the Apennines are singularly rich in remains of marine animals. When these remarkable objects drew the attention of thoughtful men, controversies soon arose whether they really were the remains of living creatures, or the productions of some capricious or mysterious power by which the forms of such creatures were mimicked; and again, if the shells were really the spoils of the sea, whether they had been carried to the hills by the deluge of which the Scripture speaks, or whether they indicated revolutions of the earth of a different kind. The earlier works which contain the descriptions of the phenomena have, in almost all instances, by far the greater part of their pages occupied with these speculations; indeed, the facts could not be studied without leading to such inferences, and would not have been collected but for the interest which such reasonings possessed. As one of the first persons who applied a sound and vigorous intellect to these subjects, we may notice the celebrated painter Leonardo da Vinci, whom we have already had to refer to as one of the founders of the modern mechanical sciences. He strenuously asserts the contents of the rocks to be real shells, and maintains the reality of the changes of the domain of land and sea which these spoils of the ocean imply. "You will tell me," he says, "that nature and the influence of the stars have formed these shelly forms in the mountains; then show me a place in the mountains where the stars at the present day make shelly forms of different ages, and of different species in the same place. And how, with that, will you explain the gravel which is hardened in stages at different heights in the mountains?" He then mentions several other particulars respecting these evidences that the existing mountains were formerly in the bed of the sea. Leonardo died in 1519. At present we refer to geological essays like his, only so far as they are descriptive. Going onwards with this view, we may notice Fracastoro, who wrote concerning the petrifactions which were brought to light in the mountains of Verona, when, in 1517, they were excavated for the purpose of repairing the city. Little was done in the way of collection of facts for some time after this. In 1669, Steno, a Dane resident in Italy, put forth his treatise, De Solido intra Solidum naturaliter contento; and the {508} following year, Augustino Scilla, a Sicilian painter, published a Latin epistle, De Corporibus Marinis Lapidescentibus, illustrated by good engravings of fossil-shells, teeth, and corals.[8\18] After another interval of speculative controversy, we come to Antonio Vallisneri, whose letters, De' Corpi Marini che su' Monti si trovano, appeared at Venice in 1721. In these letters he describes the fossils of Monte Bolca, and attempts to trace the extent of the marine deposits of Italy,[9\18] and to distinguish the most important of the fossils. Similar descriptions and figures were published with reference to our own country at a later period. In 1766, Brander's Fossilia Hantoniensia, or Hampshire Fossils, appeared; containing excellent figures of fossil shells from a part of the south coast of England; and similar works came forth in other parts of Europe.

[Note 8\18: Augustine Scilla's original drawings of fossil shells, teeth, and corals, from which the engravings mentioned in the text were executed, as well as the natural objects from which the drawings were made, were bought by Woodward, and are now in the Woodwardian Museum at Cambridge.]

[Note 9\18: p. 20.]

However exact might be the descriptions and figures thus produced, they could not give such complete information as the objects themselves, collected and permanently preserved in museums. Vallisneri says,[10\18] that having begun to collect fossils for the purpose of forming a grotto, he selected the best, and preserved them "as a noble diversion for the more curious." The museum of Calceolarius at Verona contained a celebrated collection of such remains. A copious description of it appeared in 1622. Such collections had been made from an earlier period, and catalogues of them published. Thus Gessner's work, De Rerum Fossilium, Lapidum et Gemmarum Figuris (1565), contains a catalogue of the cabinet of petrifactions collected by John Kentman; many catalogues of the same kind appeared in the seventeenth century.[11\18] Lhwyd's **Lythophylacii Britannici Iconographia, published at Oxford in 1669, and exhibiting a very ample catalogue of English Fossils contained in the Ashmolean Museum, may be noticed as one of these.

[Note 10\18: p. 1.]

[Note 11\18: Parkinson, Organic Remains, vol. i. p. 20.]

One of the most remarkable occurrences in the progress of descriptive geology in England, was the formation of a geological museum by William Woodward as early as 1695. This collection, formed with great labor, systematically arranged, and carefully catalogued, he bequeathed to the University of Cambridge; founding and endowing {509} at the same time a professorship of the study of geology. The Woodwardian Museum still subsists, a monument of the sagacity with which its author so early saw the importance of such a collection.

Collections and descriptions of fossils, including in the term specimens of minerals of all kinds, as well as organic remains, were frequently made, and especially in places where mining was cultivated; but under such circumstances, they scarcely tended at all to that general and complete knowledge of the earth of which we are now tracing the progress.

In more modern times, collections may be said to be the most important books of the geologist, at least next to the strata themselves. The identifications and arrangements of our best geologists, the immense studies of fossil anatomy by Cuvier and others, have been conducted mainly by means of collections of specimens. They are more important in this study than in botany, because specimens which contain important geological information are both more rare and more permanent. Plants, though each individual is perishable, perpetuate and diffuse their kind; while the organic impression on a stone, if lost, may never occur in a second instance; but, on the other hand, if it be preserved in the museum, the individual is almost as permanent in this case, as the species in the other.

I shall proceed to notice another mode in which such information was conveyed.

Sect. 3.--First Construction of Geological Maps.

DR. LISTER, a learned physician, sent to the Royal Society, in 1683, a proposal for maps of soils or minerals; in which he suggested that in the map of England, for example, each soil and its boundaries might be distinguished by color, or in some other way. Such a mode of expressing and connecting our knowledge of the materials of the earth was, perhaps, obvious, when the mass of knowledge became considerable. In 1720, Fontenelle, in his observations on a paper of De Reaumur's, which contained an account of a deposit of fossil-shells in Touraine, says, that in order to reason on such cases, "we must have a kind of geographical charts, constructed according to the collection of shells found in the earth." But he justly adds, "What a quantity of observations, and what time would it not require to form such maps!"

The execution of such projects required, not merely great labor, but {510} several steps in generalization and classification, before it could take place. Still such attempts were made. In 1743, was published, A new Philosophico-chorographical Chart of East Kent, invented and delineated by Christopher Packe, M.D.; in which, however, the main object is rather to express the course of the valleys than the materials of the country. Guettard formed the project of a mineralogical map of France, and Monnet carried this scheme into effect in 1780,[12\18] "by order of the king." In these maps, however, the country is not considered as divided into soils, still less strata; but each part is marked with its predominant mineral only. The spirit of generalization which constitutes the main value of such a work is wanting.

[Note 12\18: Atlas et Description Minéralogique de la France, entrepris par ordre du Roi, par MM. Guettard et Monnet, Paris, 1780, pp. 212, with 31 maps.]

Geological maps belong strictly to Descriptive Geology; they are free from those wide and doubtful speculations which form so large a portion of the earlier geological books. Yet even geological maps cannot be usefully or consistently constructed without considerable steps of classification and generalization. When, in our own time, geologists were become weary of controversies respecting theory, they applied themselves with extraordinary zeal to the construction of stratigraphical maps of various countries; flattering themselves that in this way they were merely recording incontestable facts and differences. Nor do I mean to intimate that their facts were doubtful, or their distinctions arbitrary. But still they were facts interpreted, associated, and represented, by means of the classifications and general laws which earlier geologists had established; and thus even Descriptive Geology has been brought into existence as a science by the formation of systems and the discovery of principles. At this we cannot be surprized, when we recollect the many steps which the formation of Classificatory Botany required. We must now notice some of the discoveries which tended to the formation of Systematic Descriptive Geology. {511}

II. FORMATION OF SYSTEMATIC DESCRIPTIVE GEOLOGY

Sect. 1.--Discovery of the Order and Stratification of the Materials of the Earth.

THAT the substances of which the earth is framed are not scattered and mixed at random, but possess identity and continuity to a considerable extent, Lister was aware, when he proposed his map. But there is, in his suggestions, nothing relating to stratification; nor any order of position, still less of time, assigned to these materials. Woodward, however, appears to have been fully aware of the general law of stratification. On collecting information from all parts, "the result was," he says, "that in time I was abundantly assured that the circumstances of these things in remoter countries were much the same with those of ours here: that the stone, and other terrestrial matter in France, Flanders, Holland, Spain, Italy, Germany, Denmark, and Sweden, was distinguished into strata or layers, as it is in England; that these strata were divided by parallel fissures; that there were enclosed in the stone and all the other denser kinds of terrestrial matter, great numbers of the shells, and other productions of the sea, in the same manner as in that of this island."[13\18] So remarkable a truth, thus collected from a copious collection of particulars by a patient induction, was an important step in the science.

[Note 13\18: Natural History of the Earth, 1723.]

These general facts now began to be commonly recognized, and followed into detail. **Stukeley the antiquary[14\18] (1724), remarked an important feature in the strata of England, that their escarpments, or steepest sides, are turned towards the west and north-west; and Strachey[15\18] (1719), gave a stratigraphical description of certain coal-mines near Bath.[16\18] Michell, appointed Woodwardian Professor at Cambridge {512} in 1762, described this stratified structure of the earth far more distinctly than his predecessors, and pointed out, as the consequence of it, that "the same kinds of earths, stones, and minerals, will appear at the surface of the earth in long parallel slips, parallel to the long ridges of mountains; and so, in fact, we find them."[17\18]

[Note 14\18: Itinerarium Curiosum, 1724.]

[Note 15\18: Phil. Trans. 1719, and Observations on Strata, &c. 1729.]

[Note 16\18: Fitton, Annals of Philosophy, N. S. vol. i. and ii. (1832, '3), p. 157.]

[Note 17\18: Phil. Trans. 1760.]

Michell (as appeared by papers of his which were examined after his death) had made himself acquainted with the series of English strata which thus occur from Cambridge to York;--that is, from the chalk to the coal. These relations of position required that geological maps, to complete the information they conveyed, should be accompanied by geological Sections, or imaginary representations of the order and mode of superpositions, as well as of the superficial extent of the strata, as in more recent times has usually been done. The strata, as we travel from the higher to the lower, come from under each other into view; and this out-cropping, basseting, or by whatever other term it is described, is an important feature in their description.

It was further noticed that these relations of position were combined with other important facts, which irresistibly suggested the notion of a relation in time. This, indeed, was implied in all theories of the earth; but observations of the facts most require our notice. Steno is asserted by Humboldt[18\18] to be the first who (in 1669) distinguished between rocks anterior to the existence of plants and animals upon the globe, containing therefore no organic remains; and rocks super-imposed on these, and full of such remains; "turbidi maris sedimenta sibi invicem imposita".

[Note 18\18: Essai **Géognostique.]

Rouelle is stated, by his pupil Desmarest, to have made some additional and important observations. "He saw," it is said, "that the shells which occur in rocks were not the same in all countries; that certain species occur together, while others do not occur in the same beds; that there is a constant order in the arrangement of these shells, certain species lying in distinct bands."[19\18]

[Note 19\18: Encycl. Méthod. Geogr. Phys. tom. i. p. 416, as quoted by Fitton as above, p. 159.]

Such divisions as these required to be marked by technical names. A distinction was made of l'ancienne terre and la nouvelle terre, to which Rouelle added a travaille intermédiaire. Rouelle died in 1770, having been known by lectures, not by books. Lehman, in 1756, claims for himself the credit of being the first to observe and describe correctly the structure of stratified countries; being ignorant, {513} probably, of the labors of Strachey in England. He divided mountains into three classes;[20\18] primitive, which were formed with the world;--those which resulted from a partial destruction of the primitive rocks;--and a third class resulting from local or universal deluges. In 1759, also, Arduine,[21\18] in his Memoirs on the mountains of Padua, Vicenza, and Verona, deduced, from original observations, the distinction of rocks into primary, secondary, and tertiary.

[Note 20\18: Lyell, i. 70.]

[Note 21\18: Ib. 72.]

The relations of position and fossils were, from this period, inseparably connected with opinions concerning succession in time. Odoardi remarked,[22\18] that the strata of the **Sub-Apennine hills are unconformable to those of the Apennine, (as Strachey had observed, that the strata above the coal were unconformable to the coal;[23\18]) and his work contained a clear argument respecting the different ages of these two classes of hills. Fuchsel was, in 1762, aware of the distinctness of strata of different ages in Germany. Pallas and Saussure were guided by general views of the same kind in observing the countries which they visited: but, perhaps, the general circulation of such notions was most due to Werner.

[Note 22\18: Ib. 74.]

[Note 23\18: Fitton, p. 157.]

Sect. 2.--Systematic form given to Descriptive Geology.--Werner.

WERNER expressed the general relations of the strata of the earth by means of classifications which, so far as general applicability is concerned, are extremely imperfect and arbitrary; he promulgated a theory which almost entirely neglected all the facts previously discovered respecting the grouping of fossils,--which was founded upon observations made in a very limited district of Germany,--and which was contradicted even by the facts of this district. Yet the acuteness of his discrimination in the subjects which he studied, the generality of the tenets he asserted, and the charm which he threw about his speculations, gave to Geology, or, as he termed it, Geognosy, a popularity and reputation which it had never before possessed. His system had asserted certain universal formations, which followed each other in a constant order;--granite the lowest,--then mica-slate and clay-slate;--upon these primitive rocks, generally highly inclined, rest other transition strata;--upon these, lie secondary ones, which being more nearly horizontal, are called flötz or flat. The term formation, {514} which we have thus introduced, indicating groups which, by evidence of all kinds,--of their materials, their position, and their organic contents,--are judged to belong to the same period, implies no small amount of theory: yet this term, from this time forth, is to be looked upon as a term of classification solely, so far as classification can be separately attended to.

Werner's distinctions of strata were for the most part drawn from mineralogical constitution. Doubtless, he could not fail to perceive the great importance of organic fossils. "I was witness," says M. de Humboldt, one of his most philosophical followers, "of the lively satisfaction which he felt when, in 1792, M. de **Schlottheim, one of the most distinguished geologists of the school of Freiberg, began to make the relations of fossils to strata the principal object of his studies." But Werner and the disciples of his school, even the most enlightened of them, never employed the characters derived from organic remains with the same boldness and perseverance as those who had from the first considered them as the leading phenomena: thus M. de Humboldt expresses doubts which perhaps many other geologists do not feel when, in 1823, he says, "Are we justified in concluding that all formations are characterized by particular species? that the fossil-shells of the chalk, the muschelkalk, the Jura limestone, and the Alpine limestone, are all different? I think this would be pushing the induction much too far."[24\18] In Prof. Jamieson's Geognosy, which may be taken as a representation of the Wernerian doctrines, organic fossils are in no instance referred to as characters of formations or strata. After the curious and important evidence, contained in organic fossils, which had been brought into view by the labors of Italian, English, and German writers, the promulgation of a system of Descriptive Geology, in which all this evidence was neglected, cannot be considered otherwise than as a retrograde step in science.

[Note 24\18: Gissement des Roches, p. 41.]

Werner maintained the aqueous deposition of all strata above the primitive rocks; even of those trap rocks, to which, from their resemblance to lava and other phenomena, Raspe, Arduino, and others, had already assigned a volcanic origin. The fierce and long controversy between the Vulcanists and Neptunists, which this dogma excited, does not belong to this part of our history; but the discovery of veins of granite penetrating the superincumbent slate, to which the controversy led, was an important event in descriptive geology. Hutton, the {515} author of the theory of igneous causation which was in this country opposed to that of Werner, sought and found this phenomenon in the Grampian hills, in 1785. This supposed verification of his system "filled him with delight, and called forth such marks of joy and exultation, that the guides who accompanied him were persuaded, says his biographer,[25\18] that he must have discovered a vein of silver or gold."[26\18]

[Note 25\18: Playfair's Works, vol. iv. p. 75.]

[Note 26\18: Lyell, i. 90.]

Desmarest's examination of Auvergne (1768) showed that there was there an instance of a country which could not even be described without terms implying that the basalt, which covered so large a portion of it, had flowed from the craters of extinct volcanoes. His map of Auvergne was an excellent example of a survey of such a country, thus exhibiting features quite different from those of common stratified countries.[27\18]

[Note 27\18: Lyell, i. 86.]

The facts connected with metalliferous veins were also objects of Werner's attention. A knowledge of such facts is valuable to the geologist as well as to the miner, although even yet much difficulty attends all attempts to theorize concerning them. The facts of this nature have been collected in great abundance in all mining districts; and form a prominent part of the descriptive geology of such districts; as, for example, the Hartz, and Cornwall.

Without further pursuing the history of the knowledge of the inorganic phenomena of the earth, I turn to a still richer department of geology, which is concerned with organic fossils.

Sect. 3.--Application of Organic Remains as a Geological Character.--Smith.

ROUELLE and Odoardi had perceived, as we have seen, that fossils were grouped in bands: but from this general observation to the execution of a survey of a large kingdom, founded upon this principle, would have been a vast stride, even if the author of it had been aware of the doctrines thus asserted by these writers. In fact, however, William Smith executed such a survey of England, with no other guide or help than his own sagacity and perseverance. In his employments as a civil engineer, he noticed the remarkable continuity and constant order of the strata in the neighborhood of Bath, as discriminated by their fossils; and about the year 1793, he[28\18] drew up a Tabular View of the {516} strata of that district, which contained the germ of his subsequent discoveries. Finding in the north of England the same strata and associations of strata with which he had become acquainted in the west, he was led to name them and to represent them by means of maps, according to their occurrence over the whole face of England. These maps appeared[29\18] in 1815; and a work by the same author, entitled The English Strata identified by Organic Remains, came forth later. But the views on which this identification of strata rests, belong to a considerably earlier date; and had not only been acted upon, but freely imparted in conversation many years before.

[Note 28\18: Fitton, p. 148.]

[Note 29\18: Brit. Assoc. 1832. Conybeare, p. 373.]

In the meantime the study of fossils was pursued with zeal in various countries. Lamarck and Defrance employed themselves in determining the fossil shells of the neighborhood of Paris;[30\18] and the interest inspired by this subject was strongly nourished and stimulated by the memorable work of Cuvier and Brongniart, On the Environs of Paris, published in 1811, and by Cuvier's subsequent researches on the subjects thus brought under notice. For now, not only the distinction, succession, and arrangement, but many other relations among fossil strata, irresistibly arrested the attention of the philosopher. Brongniart[31\18] showed that very striking resemblances occurred in their fossil remains, between certain strata of Europe and of North America; and proved that a rock may be so much disguised, that the identity of the stratum can only be recognized by geological characters.[32\18]

[Note 30\18: Humboldt, Giss. d. R. p. 35.]

[Note 31\18: Hist. Nat. des Crustacés Fossiles, pp. 57, 62.]

[Note 32\18: Humboldt, Giss. d. R. p. 45.]

The Italian geologists had found in their hills, for the most part, the same species of shells which existed in their seas; but the German and English writers, as Gesner,[33\18] Raspe,[34\18] and Brander,[35\18] had perceived that the fossil-shells were either of unknown species, or of such as lived in distant latitudes. To decide that the animals and plants, of which we find the remains in a fossil state, were of species now extinct, obviously required an exact and extensive knowledge of natural history. And if this were so, to assign the relations of the past to the existing tribes of beings, and the peculiarities of their vital processes and habits, were tasks which could not be performed without the most consummate physiological skill and talent. Such tasks, however, have been the familiar employments of geologists, and naturalists incited and {517} appealed to by geologists, ever since Cuvier published his examination of the fossil inhabitants of the Paris basin. Without attempting a history of such labors, I may notice a few circumstances connected with them.

[Note 33\18: Lyell, i. 70.]

[Note 34\18: Ib. 74.]

[Note 35\18: Ib. 76.]

Sect. 4.--Advances in Palæontology.--Cuvier.

SO long as the organic fossils which were found in the strata of the earth were the remains of marine animals, it was very difficult for geologists to be assured that the animals were such as did not exist in any part or clime of the existing ocean. But when large land and river animals were discovered, different from any known species, the persuasion that they were of extinct races was forced upon the naturalist. Yet this opinion was not taken up slightly, nor acquiesced in without many struggles.

Bones supposed to belong to fossil elephants, were some of the first with regard to which this conclusion was established. Such remains occur in vast numbers in the soil and gravel of almost every part of the world; especially in Siberia, where they are called the bones of the mammoth. They had been noticed by the ancients, as we learn from Pliny;[36\18] and had been ascribed to human giants, to elephants imported by the Romans, and to many other origins. But in 1796, Cuvier had examined these opinions with a more profound knowledge than his predecessors; and he thus stated the result of his researches.[37\18] "With regard to what have been called the fossil remains of elephants, from Tentzelius to Pallas, I believe that I am in the condition to prove, that they belong to animals which were very clearly different in species from our existing elephants, although they resembled them sufficiently to be considered as belonging to the same genera." He had founded this conclusion principally on the structure of the teeth, which he found to differ in the Asiatic and African elephant; while, in the fossil animal, it was different from both. But he also reasoned in part on the form of the skull, of which the best-known example had been described in the Philosophical Transactions as early as 1737.[38\18] "As soon," says Cuvier, at a later period, "as I became acquainted with Messerschmidt's drawing, and joined to the differences which it presented, those which I had myself observed in the inferior jaw and the {518} molar teeth, I no longer doubted that the fossil elephants were of a species different from the Indian elephant. This idea, which I announced to the Institute in the month of January, 1796, opened to me views entirely new respecting the theory of the earth; and determined me to devote myself to the long researches and to the assiduous labors which have now occupied me for twenty-five years."[39\18]

[Note 36\18: Hist. Nat. lib. xxxvi. 18.]

[Note 37\18: Mém. Inst. Math. et Phys. tom. ii. p. 4.]

[Note 38\18: Described by Breyne from a specimen found in Siberia by Messerschmidt in 1722. Phil. Trans. xl. 446.]

[Note 39\18: Ossemens Fossiles, second edit. i. 178.]

We have here, then, the starting-point of those researches concerning extinct animals, which, ever since that time, have attracted so large a share of notice from geologists and from the world. Cuvier could hardly have anticipated the vast storehouse of materials which lay under his feet, ready to supply him occupation of the most intense interest in the career on which he had thus entered. The examination of the strata on which Paris stands, and of which its buildings consist, supplied him with animals, not only different from existing ones, but some of them of great size and curious peculiarities. A careful examination of the remains which these strata contain was undertaken soon after the period we have referred to. In 1802, Defrance had collected several hundreds of undescribed species of shells; and Lamarck[40\18] began a series of Memoirs upon them; remodelling the whole of Conchology, in order that they might be included in its classifications. And two years afterwards (1804) appears the first of Cuvier's grand series of Memoirs containing the restoration of the vertebrate animals of these strata. In this vast natural museum, and in contributions from other parts of the globe, he discovered the most extraordinary creatures:--the Palæotherium,[41\18] which is intermediate between the horse and the pig; the Anoplotherium, which stands nearest to the rhinoceros and the tapir; the Megalonix and Megatherium, animals of the sloth tribe, but of the size of the ox and the rhinoceros. The Memoirs which contained these and many other discoveries, set the naturalists to work in every part of Europe.

[Note 40\18: Annales du Muséum d'Hist. Nat. tom. i. p. 308, and the following volumes.]

[Note 41\18: Daubuisson, ii. 411.]

Another very curious class of animals was brought to light principally by the geologists of England; animals of which the bones, found in the lias stratum, were at first supposed to be those of crocodiles. But in 1816,[42\18] Sir Everard Home says, "In truth, on a consideration of this skeleton, we cannot but be inclined to believe, that among the animals destroyed by the catastrophes of remote antiquity, there had {519} been some at least that differ so entirely in their structure from any which now exist as to make it impossible to arrange their fossil remains with any known class of animals." The animal thus referred to, being clearly intermediate between fishes and lizards, was named by Mr. König, Ichthyosaurus; and its structure and constitution were more precisely determined by Mr. Conybeare in 1821, when he had occasion to compare with it another extinct animal of which he and Mr. de la Beche had collected the remains. This animal, still more nearly approaching the lizard tribe, was by Mr. Conybeare called Plesiosaurus.[43\18] Of each of these two genera several species were afterwards found.

[Note 42\18: Phil. Trans. 1816, p. 20.]

[Note 43\18: Geol. Trans. vol. v.]

Before this time, the differences of the races of animals and plants belonging to the past and the present periods of the earth's history, had become a leading subject of speculation among geological naturalists. The science produced by this study of the natural history of former states of the earth has been termed Palæontology; and there is no branch of human knowledge more fitted to stir men's wonder, or to excite them to the widest physiological speculations. But in the present part of our history this science requires our notice, only so far as it aims at the restoration of the types of ancient animals, on clear and undoubted principles of comparative anatomy. To show how extensive and how conclusive is the science when thus directed, we need only refer to Cuvier's Ossemens Fossiles;[44\18] a work of vast labor and profound knowledge, which has opened wide the doors of this part of geology. I do not here attempt even to mention the labors of the many other eminent contributors to Palæontology; as Brocchi, Des Hayes, Sowerby, Goldfuss, Agassiz, who have employed themselves on animals, and Schlottheim, Brongniart, Hutton, Lindley, on plants.

[Note 44\18: The first edition appeared in 1812, consisting principally of the Memoirs to which reference has already been made.]

[2nd Ed.] [Among the many valuable contributions to Palæontology in more recent times, I may especially mention Mr. Owen's Reports on British Fossil Reptiles, on British Fossil Mammalia, and on the Extinct Animals of Australia, with descriptions of certain Fossils indicative of large Marsupial Pachydermata: and M. Agassiz's Report on the Fossil Fishes of the Devonian System, his Synoptical Table of British Fossil Fishes, and his Report on the Fishes of the London Clay. All these are contained in the volumes produced by the British Association from 1839 to 1845. {520}

A new and most important instrument of palæontological investigation has been put in the geologist's hand by Prof. Owen's discovery, that the internal structure of teeth, as disclosed by the microscope, is a means of determining the kind of the animal. He has carried into every part of the animal kingdom an examination founded upon this discovery, and has published the results of this in his Odontography. As an example of the application of this character of animals, I may mention that a tooth brought from Riga by Sir R. Murchison was in this way ascertained by Mr. Owen to belong to a fish of the genus Dendrodus. (Geology of Russia, i. 67.)]

When it had thus been established, that the strata of the earth are characterized by innumerable remains of the organized beings which formerly inhabited it, and that anatomical and physiological considerations must be carefully and skilfully applied in order rightly to interpret these characters, the geologist and the palæontologist obviously had, brought before them, many very wide and striking questions. Of these we may give some instances; but, in the first place, we may add a few words concerning those eminent philosophers to whom the science owed the basis on which succeeding speculations were to be built.

Sect. 5.--Intellectual Characters of the Founders of Systematic Descriptive Geology.

IT would be in accordance with the course we have pursued in treating of other subjects, that we should attempt to point out in the founders of the science now under consideration, those intellectual qualities and habits to which we ascribe their success. The very recent date of the generalizations of geology, which has hardly allowed us time to distinguish the calm expression of the opinion of the wisest judges, might, in this instance, relieve us from such a duty; but since our plan appears to suggest it, we will, at least, endeavor to mark the characters of the founders of geology, by a few of their prominent lines.

The three persons who must be looked upon as the main authors of geological classification are, Werner, Smith, and Cuvier. These three men were of very different mental constitution; and it will, perhaps, not be difficult to compare them, in reference to those qualities which we have all along represented as the main features of the discoverer's genius, clearness of ideas, the possession of numerous facts, and the power of bringing these two elements into contact. {521}

In the German, considering him as a geologist, the ideal element predominated. That Werner's powers of external discrimination were extremely acute, we have seen in speaking of him as a mineralogist; and his talent and tendency for classifying were, in his mineralogical studies, fully fed by an abundant store of observation; but when he came to apply this methodizing power to geology, the love of system, so fostered, appears to have been too strong for the collection of facts he had to deal with. As we have already said, he promulgated, as representing the world, a scheme collected from a province, and even too hastily gathered from that narrow field. Yet his intense spirit of method in some measure compensated for other deficiencies, and enabled him to give the character of a science to what had been before a collection of miscellaneous phenomena. The ardor of system-making produced a sort of fusion, which, however superficial, served to bind together the mass of incoherent and mixed materials, and thus to form, though by strange and anomalous means, a structure of no small strength and durability, like the ancient vitrified structures which we find in some of our mountain regions.

Of a very different temper and character was William Smith. No literary cultivation of his youth awoke in him the speculative love of symmetry and system; but a singular clearness and precision of the classifying power, which he possessed as a native talent, was exercised and developed by exactly those geological facts among which his philosophical task lay. Some of the advances which he made, had, as we have seen, been at least entered upon by others who preceded him: but of all this he was ignorant; and, perhaps, went on more steadily and eagerly to work out his own ideas, from the persuasion that they were entirely his own. At a later period of his life, he himself published an account of the views which had animated him in his earlier progress. In this account[45\18] he dates his attempts to discriminate and connect strata from the year 1790, at which time he was twenty years old. In 1792, he "had considered how he could best represent the order of superposition--continuity of course--and general eastern declination of the strata." Soon after, doubts which had arisen were removed by the "discovery of a mode of identifying the strata by the organized fossils respectively imbedded therein." And "thus stored with ideas," as he expresses himself, he began to communicate them to his friends. In all this, we see great vividness {522} of thought and activity of mind, unfolding itself exactly in proportion to the facts with which it had to deal. We are reminded of that cyclopean architecture in which each stone, as it occurs, is, with wonderful ingenuity, and with the least possible alteration of its form, shaped so as to fit its place in a solid and lasting edifice.

[Note 45\18: Phil. Mag. 1833, vol. i. p. 38.]

Different yet again was the character (as a geological discoverer) of the great naturalist of the beginning of the nineteenth century. In that part of his labors of which we have now to speak, Cuvier's dominant ideas were rather physiological than geological. In his views of past physical changes, he did not seek to include any ranges of facts which lay much beyond the narrow field of the Paris basin. But his sagacity in applying his own great principle of the Conditions of Existence, gave him a peculiar and unparalleled power in interpreting the most imperfect fossil records of extinct anatomy. In the constitution of his mind, all philosophical endowments were so admirably developed and disciplined, that it was difficult to say, whether more of his power was due to genius or to culture. The talent of classifying which he exercised in geology, was the result of the most complete knowledge and skill in zoology; while his views concerning the revolutions which had taken place in the organic and inorganic world, were in no small degree aided by an extraordinary command of historical and other literature. His guiding ideas had been formed, his facts had been studied, by the assistance of all the sciences which could be made to bear upon them. In his geological labors we seem to see some beautiful temple, not only firm and fair in itself, but decorated with sculpture and painting, and rich in all that art and labor, memory and imagination, can contribute to its beauty.

[2nd Ed.] [Sir Charles Lyell (B. i. c. iv.) has quoted with approval what I have elsewhere said, that the advancement of three of the main divisions of geology in the beginning of the present century was promoted principally by the three great nations of Europe,--the German, the English, and the French:--Mineralogical Geology by the German school of Werner:--Secondary Geology by Smith and his English successors;--Tertiary Geology by Cuvier and his fellow-laborers in France.] {523}

III. SEQUEL TO THE FORMATION OF SYSTEMATIC DESCRIPTIVE GEOLOGY

Sect. 1.--Reception and Diffusion of Systematic Geology.

IF our nearness to the time of the discoveries to which we have just referred, embarrasses us in speaking of their authors, it makes it still more difficult to narrate the reception with which these discoveries met. Yet here we may notice a few facts which may not be without their interest.

The impression which Werner made upon his hearers was very strong; and, as we have already said, disciples were gathered to his school from every country, and then went forward into all parts of the world, animated by the views which they had caught from him. We may say of him, as has been so wisely said of a philosopher of a very different kind,[46\18] "He owed his influence to various causes; at the head of which may be placed that genius for system, which, though it cramps the growth of knowledge, perhaps finally atones for that mischief by the zeal and activity which it rouses among followers and opponents, who discover truth by accident, when in pursuit of weapons for their warfare." The list of Werner's pupils for a considerable period included most of the principal geologists of Europe; Freisleben, Mohs, Esmark, d'Andrada, Raumer, Engelhart, Charpentier, Brocchi. Alexander von Humboldt and Leopold von Buch went forth from his school to observe America and Siberia, the Isles of the Atlantic, and the coast of Norway. Professor Jameson established at Edinburgh a Wernerian Society; and his lecture-room became a second centre of Wernerian doctrines, whence proceeded many zealous geological observers; among these we may mention as one of the most distinguished, M. Ami Boué, though, like several others, he soon cast away the peculiar opinions of the Wernerian school. The classifications of this school were, however, diffused over the civilized world with {524} extraordinary success; and were looked upon with great respect, till the study of organic fossils threw them into the shade.

[Note 46\18: Mackintosh on Hobbes, Dissert. p. 177.]

Smith, on the other hand, long pursued his own thoughts without aid and without sympathy. About 1799 he became acquainted with a few gentlemen (Dr. Anderson, Mr. Richardson, Mr. Townsend, and Mr. Davies), who had already given some attention to organic fossils, and who were astonished to find his knowledge so much more exact and extensive than their own. From this time he conceived the intention of publishing his discoveries; but the want of literary leisure and habits long prevented him. His knowledge was orally communicated without reserve to many persons; and thus gradually and insensibly became part of the public stock. When this diffusion of his views had gone on for some time, his friends began to complain that the author of them was deprived of his well-merited share of fame. His delay in publication made it difficult to remedy this wrong; for soon after he published his Geological Map of England, another appeared, founded upon separate observations; and though, perhaps, not quite independent of his, yet in many respects much more detailed and correct. Thus, though his general ideas obtained universal currency, he did not assume his due prominence as a geologist. In 1818, a generous attempt was made to direct a proper degree of public gratitude to him, in an article in the Edinburgh Review, the production of Dr. Fitton, a distinguished English geologist. And when the eminent philosopher, Wollaston, had bequeathed to the Geological Society of London a fund from which a gold medal was to be awarded to geological services, the first of such medals was, in 1831, "given to Mr. William Smith, in consideration of his being a great original discoverer in English geology; and especially for his having been the first in this country to discover and to teach the identification of strata, and to determine their succession by means of their imbedded fossils."

Cuvier's discoveries, on the other hand, both from the high philosophic fame of their author, and from their intrinsic importance, arrested at once the attention of scientific Europe; and, notwithstanding the undoubted priority of Smith's labors, for a long time were looked upon as the starting-point of our knowledge of organic fossils. And, in reality, although Cuvier's memoirs derived the greatest part of their value from his zoological conclusions, they reflected back no small portion of interest on the classifications of strata which were involved in his inferences. And the views which he presented gave to geology an attractive and striking character, and a connexion with {525} large physiological as well as physical principles, which added incomparably to its dignity and charm.

In tracing the reception and diffusion of doctrines such as those of Smith and Cuvier, we ought not to omit to notice more especially the formation and history of the Geological Society of London, just mentioned. It was established in 1807, with a view to multiply and record observations, and patiently to await the result of some future period; that is, its founders resolved to apply themselves to Descriptive Geology, thinking the time not come for that theoretical geology which had then long fired the controversial ardor of Neptunists and Plutonists. The first volume of the Transactions of this society was published in 1811. The greater part of the contents of this volume[47\18] savor of the notions of the Wernerian school; and there are papers on some of the districts in England most rich in fossils, which Mr. Conybeare says, well exhibit the low state of secondary geology at that period. But a paper by Mr. Parkinson refers to the discoveries both of Smith and of Cuvier; and in the next volume, Mr. Webster gives an account of the Isle of Wight, following the admirable model of Cuvier and Brongniart's account of the Paris basin. "If we compare this memoir of Mr. Webster with the preceding one of Dr. Berger (also of the Isle of Wight), they at once show themselves to belong to two very distinct eras of science; and it is difficult to believe that the interval which elapsed between their respective publication was only three or four years."[48\18]

[Note 47\18: Conybeare, Report. Brit. Assoc. p. 372.]

[Note 48\18: Conybeare, Report, p. 372.]

Among the events belonging to the diffusion of sound geological views in this country, we may notice the publication of a little volume entitled, The Geology of England and Wales, by Mr. Conybeare and Mr. Phillips, in 1821; an event far more important than, from the modest form and character of the work, it might at first sight appear. By describing in detail the geological structure and circumstances of England (at least as far downwards as the coal), it enabled a very wide class of readers to understand and verify the classifications which geology had then very recently established; while the extensive knowledge and philosophical spirit of Mr. Conybeare rendered it, under the guise of a topographical enumeration, in reality a profound and instructive scientific treatise. The vast impulse which it gave to the study of sound descriptive geology was felt and acknowledged in other countries, as well as in Britain. {526}

Since that period, Descriptive Geology in England has constantly advanced. The advance has been due mainly to the labors of the members of the Geological Society; on whose merits as cultivators of their science, none but those who are themselves masters of the subject, have a right to dwell. Yet some parts of the scientific character of these men may be appreciated by the general speculator; for they have shown that there are no talents and no endowments which may not find their fitting employment in this science. Besides that they have united laborious research and comprehensive views, acuteness and learning, zeal and knowledge; the philosophical eloquence with which they have conducted their discussions has had a most beneficial influence on the tone of their speculations; and their researches in the field, which have carried them into every country and every class of society, have given them that prompt and liberal spirit, and that open and cordial bearing, which results from intercourse with the world on a large and unfettered scale. It is not too much to say, that in our time, Practical Geology has been one of the best schools of philosophical and general culture of mind.

Sect. 2.--Application of Systematic Geology. Geological Surveys and Maps.

SUCH surveys as that which Conybeare and Phillips's book presented with respect to England, were not only a means of disseminating the knowledge implied in the classifications of such a work, but they were also an essential part of the Application and Extension of the principles established by the founders of Systematic Geology. As soon as the truth of such a system was generally acknowledged, the persuasion of the propriety of geological surveys and maps of each country could not but impress itself on men's minds.

When the earlier writers, as Lister and Fontenelle, spoke of mineralogical and fossilological maps, they could hardly be said to know the meaning of the terms which they thus used. But when subsequent classifications had shown how such a suggestion might be carried into effect, and to what important consequences it might lead, the task was undertaken in various countries in a vigorous and consistent manner. In England, besides Smith's map, another, drawn up by Mr. Greenough, was published by the Geological Society in 1819; and, being founded on very numerous observations of the author and his friends, made with great labor and cost, was not only an important {527} correction and confirmation of Smith's labors, but a valuable storehouse and standard of what had then been done in English geology. Leopold von Buch had constructed a geological map of a large portion of Germany, about the same period; but, aware of the difficulty of the task he had thus attempted, he still forbore to publish it. At a later period, and as materials accumulated, more detailed maps of parts of Germany were produced by Hoffmann and others. The French government entrusted to a distinguished Professor of the School of Mines (M. Brochant de Villiers), the task of constructing a map of France on the model of Mr. Greenough's; associating with him two younger persons, selected for their energy and talents, MM. Beaumont and Dufrénoy. We shall have occasion hereafter to speak of the execution of this survey. By various persons, geological maps of almost every country and province of Europe, and of many parts of Asia and America, have been published. I need not enumerate these, but I may refer to the account given of them by Mr. Conybeare, in the Reports of the British Association for 1832, p. 384. These various essays may be considered as contributions, though hitherto undoubtedly very imperfect ones, to that at which Descriptive Geology ought to aim, and which is requisite as a foundation for sound theory;--a complete geological survey of the whole earth. But we must say a few words respecting the language in which such a survey must be written.

As we have already said, that condition which made such maps and the accompanying descriptions possible, was that the strata and their contents had previously undergone classification and arrangement at the hands of the fathers of geology. Classification, in this as in other cases, implied names which should give to the classes distinctness and permanence; and when the series of strata belonging to one country were referred to in the description of another, in which they appeared, as was usually the case, under an aspect at least somewhat different, the supposed identification required a peculiar study of each case; and thus Geology had arrived at the point, which we have before had to notice as one of the stages of the progress of Classificatory Botany, at which a technical nomenclature and a well-understood synonymy were essential parts of the science.

Sect. 3.--Geological Nomenclature.

BY Nomenclature we mean a system of names; and hence we can {528} not speak of a Geological Nomenclature till we come to Werner and Smith. The earlier mineralogists had employed names, often artificial and arbitrary, for special minerals, but no technical and constant names for strata. The elements of Werner's names for the members of his geological series were words in use among miners, as Gneiss, Grauwacke, Thonschiefer, Rothe todte liegende, Zechstein; or arbitrary names of the mineralogists, as Syenite, Serpentine, Porphyry, Granite. But the more technical part of his phraseology was taken from that which is the worst kind of name, arbitrary numeration. Thus he had his first sandstone formation, second sandstone, third sandstone; first flötz limestone, second flötz limestone, third flötz limestone. Such names are, beyond all others, liable to mistake in their application, and likely to be expelled by the progress of knowledge; and accordingly, though the Wernerian names for rocks mineralogically distinguished, have still some currency, his sandstones and limestones, after creating endless confusion while his authority had any sway, have utterly disappeared from good geological works.

The nomenclature of Smith was founded upon English provincial terms of very barbarous aspect, as Cornbrash, Lias, Gault, Clunch Clay, Coral Rag. Yet these terms were widely diffused when his classification was generally accepted; they kept their place, precisely because they had no systematic signification; and many of them are at present part of the geological language of the whole civilized world.

Another kind of names which has been very prevalent among geologists are those borrowed from places. Thus the Wernerians spoke of Alpine Limestone and Jura Limestone; the English, of Kimmeridge Clay and Oxford Clay, Purbeck Marble, and Portland Rock. These names, referring to the stratum of a known locality as a type, were good, as far as an identity with that type had been traced; but when this had been incompletely done, they were liable to great ambiguity. If the Alps or the Jura contain several formations of limestone, such terms as we have noticed, borrowed from those mountains, cease to be necessarily definite, and may give rise to much confusion.

Descriptive names, although they might be supposed to be the best, have, in fact, rarely been fortunate. The reason of this is obvious;--the mark which has been selected for description may easily fail to be essential; and the obvious connexions of natural facts may overleap the arbitrary definition. As we have already stated in the history of botany, the establishment of descriptive marks of real classes presupposes the important but difficult step, of the discovery of such marks. {529} Hence those descriptive names only have been really useful in geology which had been used without any scrupulous regard to the appropriateness of the description. The Green Sand may be white, brown, or red; the Mountain Limestone may occur only in valleys; the Oolite may have no roe-like structure; and yet these may be excellent geological names, if they be applied to formations geologically identical with those which the phrases originally designated. The signification may assist the memory, but must not be allowed to subjugate the faculty of natural classification.

The terms which have been formed by geologists in recent times have been drawn from sources similar to those of the older ones, and will have their fortune determined by the same conditions. Thus Mr. Lyell has given to the divisions of the tertiary strata the appellations Pleiocene, Meiocene, Eocene, accordingly as they contain a majority of recent species of shells, a minority of such species, or a small proportion of living species, which may be looked upon as indicating the dawn of the existing state of the animate creation. But in this case, he wisely treats his distinctions, not as definitions, but as the marks of natural groups. "The plurality of species indicated by the name pleiocene must not," he says,[49\18] "be understood to imply an absolute majority of recent fossil shells in all cases, but a comparative preponderance wherever the pleiocene are contrasted with strata of the period immediately preceding."

[Note 49\18: Geol. iii. 392.]

Mr. Lyell might have added, that no precise percentage of recent species, nor any numerical criterion whatever, can be allowed to overbear the closer natural relations of strata, proved by evidence of a superior kind, if such can be found. And this would be the proper answer to the objection made by De la Beche to these names; namely, that it may happen that the meiocene rocks of one country may be of the same date as the pleiocene of another; the same formation having in one place a majority, in another a minority, of existing species. We are not to run into this incongruity, for we are not so to apply the names. The formation which has been called pleiocene, must continue to be so called, even where the majority of recent species fails; and all rocks that agree with that in date, without further reference to the numerical relations of their fossils, must also share in the name.

To invent good names for these large divisions of the series of strata is indeed extremely difficult. The term Oolite is an instance in which {530} a descriptive word has become permanent in a case of this kind; and, in imitation of it, Pœcilite (from ποικίλος, various,**) has been proposed by Mr. Conybeare[50\18] as a name for the group of strata inferior to the oolites, of which the Variegated Sandstone (Bunter Sandstein, Grès Bigarré,) is a conspicuous member. For the series of formations which lies immediately over the rocks in which no organic remains are found, the term Transition was long used, but with extreme ambiguity and vagueness. When this series, or rather the upper part of it, was well examined in South Wales, where it consists of many well-marked members, and may be probably taken as a type for a large portion of the rest of the world, it became necessary to give to the group thus explored a name not necessarily leading to assumption or controversy. Mr. Murchison selected the term Silurian, borrowed from the former inhabitants of the country in which his types were found; and this is a term excellent in many respects; but one which will probably not quite supersede "Transition," because, in other places, transition rocks occur which correspond to none of the members of the Silurian region.

[Note 50\18: Report, p. 379.]

Though new names are inevitable accompaniments of new views of classification, and though, therefore, the geological discoverer must be allowed a right to coin them, this is a privilege which, for the sake of his own credit, and the circulation of his tokens, he must exercise with great temperance and judgment. M. Brongniart may be taken as an example of the neglect of this caution. Acting upon the principle, in itself a sound one, that inconveniences arise from geological terms which have a mineralogical signification, he has given an entirely new list of names of the members of the geological series. Thus the primitive unstratified rocks are terrains agalysiens; the transition semi-compact are hemilysiens; the sedimentary strata are yzemiens; the diluvial deposits are clysmiens; and these divisions are subdivided by designations equally novel; thus of the "terrains yzemiens," members are--the terrains clastiques, tritoniens, protéïques, palæotheriens, epilymniques, thalassiques.[51\18] Such a nomenclature appears to labor under great inconveniences, since the terms are descriptive in their derivation, yet are not generally intelligible, and refer to theoretical views yet have not the recommendation of systematic connexion. {531}

[Note 51\18: Brongniart, Tableau des Terrains, 1829.]

Sect. 4.--Geological Synonymy, or Determination of Geological Equivalents.

IT will easily be supposed that with so many different sources of names as we have mentioned, the same stratum may be called by different designations; and thus a synonymy may be necessary for geology; as it was for botany in the time of Bauhin, when the same plants had been spoken of by so many different appellations in different authors. But in reality, the synonymy of geology is a still more important part of the subject than the analogy of botany would lead us to suppose. For in plants, the species are really fixed, and easily known when seen; and the ambiguity is only in the imperfect communication or confused ideas of the observers. But in geology, the identity of a stratum or formation in different places, though not an arbitrary, may be a very doubtful matter, even to him who has seen and examined. To assign its right character and place to a stratum in a new country, is, in a great degree, to establish the whole geological history of the country. To assume that the same names may rightly be applied to the strata of different countries, is to take for granted, not indeed the Wernerian dogma of universal formations, but a considerable degree of generality and uniformity in the known formations. And how far this generality and uniformity prevail, observation alone can teach. The search for geological synonyms in different countries brings before us two questions;--first, are there such synonyms? and only in the second place, and as far as they occur, what are they?

In fact, it is found that although formations which must be considered as geologically identical (because otherwise no classification is possible,) do extend over large regions, and pass from country to country, their identity includes certain modifications; and the determination of the identity and of the modifications are inseparably involved with each other, and almost necessarily entangled with theoretical considerations. And in two countries, in which we find this modified coincidence, instead of saying that the strata are identical, and that their designations are synonyms, we may, with more propriety, consider them as two corresponding series; of which the members of the one may be treated as the Representatives or Equivalents of the members of the other.

This doctrine of Representatives or Equivalents supposes that the geological phenomena in the two countries have been the results of {532} similar series of events, which have, in some measure, coincided in time and order; and thus, as we have said, refers us to a theory. But yet, considered merely as a step in classification, the comparison of the geological series of strata in different countries is, in the highest degree, important and interesting. Indeed in the same manner in which the separation of Classificatory from Chemical Mineralogy is necessary for the completion of mineralogical science, the comparative Classification of the strata of different countries according to their resemblances and differences alone, is requisite as a basis for a Theory of their causes. But, as will easily be imagined from its nature, this part of descriptive geology deals with the most difficult and the most elevated problems; and requires a rare union of laborious observation with a comprehensive spirit of philosophical classification.

In order to give instances of this process (for of the vast labor and great talents which have been thus employed in England, France, and Germany, it is only instances that we can give,) I may refer to the geological survey of France, which was executed, as we have already stated, by order of the government. In this undertaking it was intended to obtain a knowledge of the whole mineral structure of France; but no small portion of this knowledge was brought into view, when a synonymy had been established between the Secondary Rocks of France and the corresponding members of the English and German series, which had been so well studied as to have become classical points of standard reference. For the purpose of doing this, the principal directors of the survey, MM. Brochant de Villiers, De Beaumont, and Dufrénoy, came to England in 1822, and following the steps of the best English geologists, in a few months made themselves acquainted with the English series. They then returned to France, and, starting from the chalk of Paris in various directions, travelled on the lines which carried them over the edges of the strata which emerge from beneath the chalk, identifying, as they could, the strata with their foreign analogues. They thus recognized almost all of the principal beds of the oolitic series of England.[52\18] At the same time they found differences as well as resemblances. Thus the Portland and Kimmeridge beds of France were found to contain in abundance a certain shell, the gryphæa virgula, which had not before been much remarked in those beds in England. With regard to the synonyms in Germany, on the other hand, a difference of opinion {538} arose between M. Elie de Beaumont and M. Voltz,[53\18] the former considering the Grès de Vosges as the equivalent of the Rothe todte liegende, which occurs beneath the Zechstein, while M. Voltz held that it was the lower portion of the Red or Variegated Sandstone which rests on the Zechstein.

[Note 52\18: De la Beche, Manual, 305.]

[Note 53\18: De la Beche, Manual, 381.]

In the same manner, from the first promulgation of the Wernerian system, attempts were made to identify the English with the German members of the geological alphabet; but it was long before this alphabet was rightly read. Thus the English geologists who first tried to apply the Wernerian series to this country, conceived the Old and New Red Sandstone of England to be the same with the Old and New Red Sandstone of Werner; whereas Werner's Old Red, the Rothe todte liegende, is above the coal, while the English Old Red is below it. This mistake led to a further erroneous identification of our Mountain Limestone with Werner's First Flötz Limestone; and caused an almost inextricable confusion, which, even at a recent period, has perplexed the views of German geologists respecting this country. Again, the Lias of England was, at first, supposed to be the equivalent of the Muschelkalk of Germany. But the error of this identification was brought into view by examinations and discussions in which MM. Œyenhausen and Dechen took the lead; and at a later period, Professor Sedgwick, by a laborious examination of the strata of England, was enabled to show the true relation of this part of the geology of the two countries. According to him, the New Red Sandstone of England, considered as one great complex formation, may be divided into seven members, composed of sandstones, limestones, and marls; five of which represent respectively the Rothe todte liegende; the Kupfer schiefer; the Zechstein, (with the Rauchwacké, Asche, and Stinkstein of the Thuringenwald;) the Bunter sandstein; and the Keuper: while the Muschelkalk, which lies between the two last members of the German list, has not yet been discovered in our geological series. "Such a coincidence," he observes,[54\18] "in the subdivisions of two distant mechanical deposits, even upon the supposition of their being strictly contemporaneous, is truly astonishing. It has not been assumed hypothetically, but is the fair result of the facts which are recorded in this paper."

[Note 54\18: Geol. Trans. Second Series, iii. 121.]

As an example in which the study of geological equivalents becomes still more difficult, we may notice the attempts to refer the strata of {534} the Alps to those of the north-west of Europe. The dark-colored marbles and schists resembling mica slate[55\18] were, during the prevalence of the Wernerian theory, referred, as was natural, to the transition class. The striking physical characters of this mountain region, and its long-standing celebrity as a subject of mineralogical examination, made a complete subversion of the received opinion respecting its place in the geological series, an event of great importance in the history of the science. Yet this was what occurred when Dr. Buckland, in 1820, threw his piercing glance upon this district. He immediately pointed out that these masses, by their fossils, approach to the Oolitic Series of this country. From this view it followed, that the geological equivalents of that series were to be found among rocks in which the mineralogical characters were altogether different, and that the loose limestones of England represent some of the highly-compact and crystalline marbles of Italy and Greece. This view was confirmed by subsequent investigations; and the correspondence was traced, not only in the general body of the formations, but in the occurrence of the Red Marl at its bottom, and the Green Sand and Chalk at its top.

[Note 55\18: De la Beche, Manual, 313.]

The talents and the knowledge which such tasks require are of no ordinary kind; nor, even with a consummate acquaintance with the well-ascertained formations, can the place of problematical strata be decided without immense labor. Thus the examination and delineation of hundreds of shells by the most skilful conchologists, has been thought necessary in order to determine whether the calcareous beds of Maestricht and of Gosau are or are not intermediate, as to their organic contents, between the chalk and the tertiary formations. And scarcely any point of geological classification can be settled without a similar union of the accomplished naturalist with the laborious geological collector.

It follows from the views already presented, of this part of geology, that no attempt to apply to distant countries the names by which the well-known European strata have been described, can be of any value, if not accompanied by a corresponding attempt to show how far the European series is really applicable. This must be borne in mind in estimating the import of the geological accounts which have been given of various parts of Asia, Africa, and America. For instance, when the carboniferous group and the new red sandstone are stated to {535} be found in India, we require to be assured that these formations are, in some way, the equivalents of their synonyms in countries better explored. Till this is done, the results of observation in such places would be better conveyed by a nomenclature implying only those facts of resemblance, difference, and order, which have been ascertained in the country so described. We know that serious errors were incurred by the attempts made to identify the Tertiary strata of other countries with those first studied in the Paris basin. Fancied points of resemblance, Mr. Lyell observes, were magnified into undue importance, and essential differences in mineral character and organic contents were slurred over.

[2nd Ed.] [The extension of geological surveys, the construction of geological maps, and the determination of the geological equivalents which replace each other in various countries, have been carried on in continuation of the labors mentioned above, with enlarged activity, range, and means. It is estimated that one-third of the land of each hemisphere has been geologically explored; and that thus Descriptive Geology has now been prosecuted so far, that it is not likely that even the extension of it to the whole globe would give any material novelty of aspect to Theoretical Geology. The recent literature of the subject is so voluminous that it is impossible for me to give any account of it here; very imperfectly acquainted, as I am, even with the English portion, and still more, with what has been produced in other countries.

While I admire the energetic and enlightened labors by which the philosophers of France, Belgium, Germany, Italy, Russia, and America, have promoted scientific geology, I may be allowed to rejoice to see in the very phraseology of the subject, the evidence that English geologists have not failed to contribute their share to the latest advances in the science. The following order of strata proceeding upwards is now, I think, recognized throughout Europe. The Silurian; the Devonian (Old Red Sandstone;) the Carboniferous; the Permian, (Lower part of the new Red Sandstone series;) the Trias, (Upper three members of the New Red Sandstone series;) the Lias; the Oolite, (in which are reckoned by M. D'Orbigny the Etages Bathonien, Oxonien, Kimmeridgien, and Portlandien;) the Neocomien, (Lower Green Sand,) the Chalk; and above these, Tertiary and Supra-Tertiary beds. Of these, the Silurian, described by Sir R. Murchison from its types in South Wales, has been traced by European Geologists through the Ardennes, Servia, Turkey, the shores of the Gulf of Finland, the valley {536} of the Mississippi, the west coast of North America, and the mountains of South America. Again, the labors of Prof. Sedgwick and Sir R. Murchison, in 1836, '7, and '8, aided by the sagacity of Mr. Lonsdale, led to their placing certain rocks of Devon and Cornwall as a formation intermediate between the Silurian and Carboniferous Series; and the Devonian System thus established has been accepted by geologists in general, and has been traced, not only in various parts of Europe, but in Australia and Tasmania, and in the neighborhood of the Alleganies.

Above the Carboniferous Series, Sir R. Murchison and his fellow laborers, M. de Verneuil and Count Keyserling, have found in Russia a well-developed series of rocks occupying the ancient kingdom of Permia, which they have hence called the Permian formation; and this term also has found general acceptance. The next group, the Keuper, Muschelkalk, and Bunter Sandstein of Germany, has been termed Trias by the continental geologists. The Neocomien is called from Neuchatel, where it is largely developed. Below all these rocks come, in England, the Cambrian on which Prof. Sedgwick has expended so many years of valuable labor. The comparison of the Protozoic and Hypozoic rocks of different countries is probably still incomplete.

The geologists of North America have made great progress in decyphering and describing the structure of their own country; and they have wisely gone, in a great measure, upon the plan which I have commended at the end of the third Chapter;--they have compared the rocks of their own country with each other, and given to the different beds and formations names borrowed from their own localities. This course will facilitate rather than impede the redaction of their classification to its synonyms and equivalents in the old world.

Of course it is not to be expected nor desired that books belonging to Descriptive Geology shall exclude the other two branches of the subject, Geological Dynamics and Physical Geology. On the contrary, among the most valuable contributions to both these departments have been speculations appended to descriptive works. And this is naturally and rightly more and more the case as the description embraces a wider field. The noble work On the Geology of Russia and the Urals, by Sir Roderick Murchison and his companions, is a great example of this, as of other merits in a geological book. The author introduces into his pages the various portions of geological dynamics of which I shall have to speak afterwards; and thus endeavors to make out the {537} physical history of the region, the boundaries of its raised sea bottoms, the shores of the great continent on which the mammoths lived, the period when the gold ore was formed, and when the watershed of the Ural chain was elevated.]

IV. ATTEMPTS TO DISCOVER GENERAL LAWS IN GEOLOGY

Sect. 1.--General Geological Phenomena.

BESIDES thus noticing such features in the rocks of each country as were necessary to the identification of the strata, geologists have had many other phenomena of the earth's surface and materials presented to their notice; and these they have, to a certain extent, attempted to generalize, so as to obtain on this subject what we have elsewhere termed the Laws of Phenomena, which are the best materials for physical theory. Without dwelling long upon these, we may briefly note some of the most obvious. Thus it has been observed that mountain ranges often consist of a ridge of subjacent rock, on which lie, on each side, strata sloping from the ridge. Such a ridge is an Anticlinal Line, a Mineralogical Axis. The sloping strata present their Escarpements, or steep edges, to this axis. Again, in mining countries, the Veins which contain the ore are usually a system of parallel and nearly vertical partitions in the rock; and these are, in very many cases, intersected by another system of veins parallel to each other and nearly perpendicular to the former. Rocky regions are often intersected by Faults, or fissures interrupting the strata, in which the rock on one side the fissure appears to have been at first continuous with that on the other, and shoved aside or up or down after the fracture. Again, besides these larger fractures, rocks have Joints,--separations, or tendencies to separate in some directions rather than in others; and a slaty Cleavage, in which the parallel subdivisions may be carried on, so as to produce laminæ of indefinite thinness. As an example of those laws of phenomena of which we have spoken, we may instance the general law asserted by Prof. {538} Sedgwick (not, however, as free from exception), that in one particular class of rocks the slaty Cleavage never coincides with the Direction of the strata.

The phenomena of metalliferous veins may be referred to, as another large class of facts which demand the notice of the geologist. It would be difficult to point out briefly any general laws which prevail in such cases; but in order to show the curious and complex nature of the facts, it may be sufficient to refer to the description of the metallic veins of Cornwall by Mr. Carne;[56\18] in which the author maintains that their various contents, and the manner in which they cut across, and stop, or shift, each other, leads naturally to the assumption of veins of no less than six or eight different ages in one kind of rock.

[Note 56\18: Transactions of the Geol. Soc. of Cornwall, vol. ii.]

Again, as important characters belonging to the physical history of the earth, and therefore to geology, we may notice all the general laws which refer to its temperature;--both the laws of climate, as determined by the isothermal lines, which Humboldt has drawn, by the aid of very numerous observations made in all parts of the world; and also those still more curious facts, of the increase of temperature which takes place as we descend in the solid mass. The latter circumstance, after being for a while rejected as a fable, or explained away as an accident, is now generally acknowledged to be the true state of things in many distant parts of the globe, and probably in all.

Again, to turn to cases of another kind: some writers have endeavored to state in a general manner laws according to which the members of the geological series succeed each other; and to reduce apparent anomalies to order of a wider kind. Among those who have written with such views, we may notice Alexander von Humboldt, always, and in all sciences, foremost in the race of generalization. In his attempt to extend the doctrine of geological equivalents from the rocks of Europe[57\18] to those of the Andes, he has marked by appropriate terms the general modes of geological succession. "I have insisted," he says[58\18] "principally upon the phenomena of alternation, oscillation, and local suppression, and on those presented by the passages of formations from one to another, by the effect of an interior developement."

[Note 57\18: Gissement des Roches dans les deux Hemisphères, 1823.]

[Note 58\18: Pref. p. vi.]

The phenomena of alternation to which M. de Humboldt here refers are, in fact, very curious: as exhibiting a mode in which the transitions from one formation to another may become gradual and insensible, {539} instead of sudden and abrupt. Thus the coal measures in the south of England are above the mountain limestone; and the distinction of the formations is of the most marked kind. But as we advance northward into the coal-field of Yorkshire and Durham, the subjacent limestone begins to be subdivided by thick masses of sandstone and carbonaceous strata, and passes into a complex deposit, not distinguishable from the overlying coal measures; and in this manner the transition from the limestone to the coal is made by alternation. Thus, to use another expression of M. de Humboldt's in ascending from the limestone, the coal, before we quit the subjacent stratum, preludes to its fuller exhibition in the superior beds.

Again, as to another point: geologists have gone on up to the present time endeavoring to discover general laws and facts, with regard to the position of mountain and mineral masses upon the surface of the earth. Thus M. Von Buch, in his physical description of the Canaries, has given a masterly description of the lines of volcanic action and volcanic products, all over the globe. And, more recently, M. Elie de Beaumont has offered some generalizations of a still wider kind. In this new doctrine, those mountain ranges, even in distant parts of the world, which are of the same age, according to the classifications already spoken of, are asserted to be parallel[59\18] to each other, while those ranges which are of different ages lie in different directions. This very wide and striking proposition may be considered as being at present upon its trial among the geologists of Europe.[60\18]

[Note 59\18: We may observe that the notion of parallelism, when applied to lines drawn on remote portions of a globular surface, requires to be interpreted in so arbitrary a manner, that we can hardly imagine it to express a physical law.]

[Note 60\18: Mr. Lyell, in the sixth edition of his Principles, B. i. c. xii., has combated the hypothesis of M. Elie de Beaumont, stated in the text. He has argued both against the catastrophic character of the elevation of mountain chains, and the parallelism of the contemporaneous ridges. It is evident that the former doctrine may be true, though the latter be shown to be false.]

Among the organic phenomena, also, which have been the subject of geological study, general laws of a very wide and comprehensive kind have been suggested, and in a greater or less degree confirmed by adequate assemblages of facts. Thus M. Adolphe Brongniart has not only, in his Fossil Flora, represented and skilfully restored a vast number of the plants of the ancient world; but he has also, in the Prodromus of the work, presented various important and striking views of the general character of the vegetation of former periods, as {540} insular or continental, tropical or temperate. And M. Agassiz, by the examination of an incredible number of specimens and collections of fossil fish, has been led to results which, expressed in terms of his own ichthyological classification, form remarkable general laws. Thus, according to him,[61\18] when we go below the lias, we lose all traces of two of the four orders under which he comprehends all known kinds of fish; namely, the Cycloïdean and the Ctenoïdean; while the other two orders, the Ganoïdean and Placoïdean, rare in our days, suddenly appear in great numbers, together with large sauroid and carnivorous fishes. Cuvier, in constructing his great work on ichthyology, transferred to M. Agassiz the whole subject of fossil fishes, thus showing how highly he esteemed his talents as a naturalist. And M. Agassiz has shown himself worthy of his great predecessor in geological natural history, not only by his acuteness and activity, but by the comprehensive character of his zoological philosophy, and by the courage with which he has addressed himself to the vast labors which lie before him. In his Report on the Fossil Fish discovered in England, published in 1835, he briefly sketches some of the large questions which his researches have suggested; and then adds,[62\18] "Such is the meagre outline of a history of the highest interest, full of curious episodes, but most difficult to relate. To unfold the details which it contains will be the business of my life."

[Note 61\18: Greenough, Address to Geol. Soc. 1835, p. 19.]

[Note 62\18: Brit. Assoc. Report, p. 72.]

[2nd Ed.] [In proceeding downwards through the series of formations into which geologists have distributed the rocks of the earth, one class of organic forms after another is found to disappear. In the Tertiary Period we find all the classes of the present world: Mammals, Birds, Reptiles, Fishes, Crustaceans, Mollusks, Zoophytes. In the Secondary Period, from the Chalk down to the New Red Sandstone, Mammals are not found, with the minute exception of the marsupial amphitherium and phascolotherium in the Stonesfield slate. In the Carboniferous and Devonian period we have no large Reptiles, with, again, a minute amount of exception. In the lower part of the Silurian rocks, Fishes vanish, and we have no animal forms but Mollusks, Crustaceans and Zoophytes.

The Carboniferous, Devonian and Silurian formations, thus containing the oldest forms of life, have been termed palæozoic. The boundaries of the life-bearing series have not yet been determined; but the series in which vertebrated animals do not appear has been {541} provisionally termed protozoic, and the lower Silurian rocks may probably be looked upon as its upper members. Below this, geologists place a hypozoic or azoic series of rocks.

Geologists differ as to the question whether these changes in the inhabitants of the globe were made by determinate steps or by insensible gradations. M. Agassiz has been led to the conviction that the organized population of the globe was renewed in the interval of each principal member of its formations.[63\18] Mr. Lyell, on the other hand, conceives that the change in the collection of organized beings was gradual, and has proposed on this subject an hypothesis which I shall hereafter consider.]

[Note 63\18: Brit. Assoc. Report 1842, p. 83.]

Sect. 2.--Transition to Geological Dynamics.

WHILE we have been giving this account of the objects with which Descriptive Geology is occupied, it must have been felt how difficult it is, in contemplating such facts, to confine ourselves to description and classification. Conjectures and reasonings respecting the causes of the phenomena force themselves upon us at every step; and even influence our classification and nomenclature. Our Descriptive Geology impels us to endeavor to construct a Physical Geology. This close connexion of the two branches of the subject by no means invalidates the necessity of distinguishing them: as in Botany, although the formation of a Natural System necessarily brings us to physiological relations, we still distinguish Systematic from Physiological Botany.

Supposing, however, our Descriptive Geology to be completed, as far as can be done without considering closely the causes by which the strata have been produced, we have now to enter upon the other province of the science, which treats of those causes, and of which we have already spoken, as Physical Geology. But before we can treat this department of speculation in a manner suitable to the conditions of science, and to the analogy of other parts of our knowledge, a certain intermediate and preparatory science must be formed, of which we shall now consider the origin and progress.

{{542}} GEOLOGICAL DYNAMICS.