IX. THE ELECTRO-CHEMICAL THEORY…

IX. THE ELECTRO-CHEMICAL THEORY

AMONG the consequences of the Electro-chemical Theory, must be ranged the various improvements which have been made in the voltaic battery. Daniel introduced between the two metals a partition permeable by chemical action, but such as to allow of two different acid solutions being in contact with the two metals. Mr. Grove's battery, in which the partition is of porous porcelain, and the metals are platinum and amalgamated zinc, is one of the most powerful hitherto known. Another has been constructed by Dr. Callan, in which the negative or conducting plate is a cylinder of cast iron, and the positive element a cylinder of amalgamated zinc placed in a porous cell. This also has great energy.

The Number of Elementary Substances.

There have not been, I believe, any well-established additions to the list of the simple substances recognized by chemists. Indeed the tendency at present appears to be rather to deny the separate elementary character of some already announced as such substances. Pelopium and Niobium were, as I have said, two of the new metals. But Naumann, in his Elemente der Mineralogie (4th ed. 1855), says, in a foot note (page 25): "Pelopium is happily again got rid of; for Pelopic Acid and Niobic Acid possess the same Radical. Donarium had a still shorter existence."

In the same way, when Hermann imagined that he had discovered a new simple metallic substance in the mineral Samarskite from Miask, the discovery was disproved by H. Rose (Pogg. Ann. B. 73, s. 449). {626}

In general the insulation of the new simple substances, the metallic bases of the earths, and the like,--their separation from their combinations, and the exhibition of them in a metallic form--has been a difficult chemical process, and has rarely been executed on any considerable scale. But in the case of Aluminium, the basis of the earth Alumina, the process of its extraction has recently been so much facilitated, that the metal can be produced in abundance. This being the case, it will probably soon be applied to special economical uses, for which it is fitted by possessing special properties.

{{626}} BOOK XV.

MINERALOGY.

BY the kindness of W. H. Miller, Esq., Professor of Mineralogy in the University of Cambridge, I am able to add to this part the following notices of books and memoirs.

1. Crystallography.

Elemente der Krystallographie, nebst einer tabellarischen Uebersicht der Mineralien nach der Krystallformen, von Gustav Rose. 2. Auflage. Berlin, 1838. The crystallographic method here adopted is, for the most part, that of Weiss. The method of this work has been followed in

A System of Crystallography, with its Applications to Mineralogy. By John Joseph Griffin. Glasgow, 1841. Mr. Griffin has, however, modified the notation of Rose. He has constructed a series of models of crystalline forms.

Frankenheim's System der Krystalle. 1842. This work adopts nearly the Mohsian systems of crystallization. It contains Tables of the chemical constitution, inclinations of the axis, and magnitude of the axes of all the crystals of which a description was to be found, including those formed in the laboratory, as well as those usually called minerals; 713 in all.

Fr. Aug. Quenstedt, Methode der Krystallographie, 1840, employs a fanciful method of representing a crystal by projecting upon one face of the crystal all the other faces. This invention appears to be more curious than useful.

Dr. Karl Naumann, who is spoken of in Chap. ix. of this Book, as the author of the best of the Mixed Systems of Classification, published also Grundriss der Krystallographie, Leipzig, 1826. In this and other works he modifies the notation of Mohs in a very advantageous manner. {628}

Professor Dana, in his System of Mineralogy, New Haven (U.S.), 1837, follows Naumann for the most part, both in crystallography and in mineral classification. In the latter part of the subject, he has made the attempt, which in all cases is a source of confusion and of failure, to introduce a whole system of new names of the members of his classification.

The geometry of crystallography has been investigated in a very original manner by M. Bravais, in papers published in the Journal of the Ecole Polytechnique, entitled Mémoires sur les Systèmes formés par des Points. 1850. Etudes Crystallographiques. 1851.

Hermann Kopp (Einleitung in die Krystallographie, Braunschweig. 1849) has given the description and measurement of the angles of a large number of laboratory crystals.

Rammelsberg (Krystallographische Chemie, Berlin, 1855) has collected an account of the systems, simple forms and angles of all the laboratory crystals of which he could obtain descriptions.

Schabus of Vienna (Bestimmung der Krystallgestalten **in Chemischen Laboratorien erzeugten Producte, Wien, 1855; a successful Prize Essay) has given a description, accompanied by measurements, of 90 crystalline species from his own observations.

To these attempts made in other countries to simplify and improve crystallography, I may add a remarkable Essay very recently made here by Mr. Brooke, and suggested to him by his exact and familiar knowledge of Mineralogy. It is to this effect. All the crystalline forms of any given mineral species are derived from the primitive form of that species; and the degree of symmetry, and the parameters, of this form determine the angles of all derivative forms. But how is this primitive form selected and its parameters determined? The selection of the kind of the primitive form depends upon the degree of symmetry which appears in all the derivative forms; according to which they belong to the rhombohedral, prismatic, square pyramidal, or some other system: and this determination is commonly clear. But the parameters, or the angles, of the primitive form, are commonly determined by the cleavage of the mineral. Is this a sufficient and necessary ground of such determination? May not a simplification be effected, in some cases, by taking some other parameters? by taking a primitive form which belongs to the proper system, but which has some other angles than those given by cleavage? Mr. Brooke has tried whether, for instance, crystals of the rhombohedral system may not be referred with advantage to primitive rhombohedrons which have, in all {629} the species, nearly the same angles. The advantage to be obtained by such a change would be the simplification of the laws of derivation in the derivative forms: and therefore we have to ask, whether the indices of derivation are smaller numbers in this way or with the hitherto accepted fundamental angles. It appears to me, from the examples given, that the advantage of simplicity in the indices is on the side of the old system: but whether this be so or not, it was a great benefit to crystallography to have the two methods compared. Mr. Brooke's Essay is a Memoir presented to the Royal Society in 1856.

2. Optical Properties of Minerals.

The Handbuch der Optik, von F. W. G. Radicke, Berlin, 1839, contains a chapter on the optical properties of crystals. The author's chief authority is Sir D. Brewster, as might be expected.

M. Haidinger has devoted much attention to experiments on the pleochroism of minerals. He has invented an instrument which makes the dichroism of minerals more evident by exhibiting the two colors side by side.

The pleochroism of minerals, and especially the remarkable clouds that in the cases of Iolite, Andalusite, Augite, Epidote, and Axinite, border the positions of either optical axis, have been most successfully imitated by M. de Senarmont by means of artificial crystallizations. (Ann. de Chim. 3 Ser. xli. p. 319.)

M. Pasteur has found that Racemic Acid consists of two different acids, having the same density and composition. The salts of these acids, with bases of Ammonia and of Potassa, are hemihedral, the hemihedral faces which occur in the one being wanting in the other. The acids of these different crystals have circular polarization of opposite kinds. (Ann. de Chim. 3 Ser. xxviii. 56, 99.) This discovery was marked by the assignation of the Rumford Medal to M. Pasteur in 1856.

M. Marbach has discovered that crystals of chlorate of soda, which apparently belongs to the cubic or tessular system, exhibit hemihedral faces of a peculiar character; and that the crystals have circular polarization of opposite kinds in accordance with the differences of the plagihedral faces. (Poggendorf's Annalen, xci. 482.)

M. Seybolt of Vienna has found a means of detecting plagihedral faces in quartz crystals which do not reveal them externally. (Akad. d. Wissenschaft zu Wien, B. xv. s. 59.) {630}

3. Classification of Minerals.

In the Philosophy of the Inductive Sciences, B. VIII. C. iii., I have treated of the Application of the Natural-history Method of Classification to Mineralogy, and have spoken of the Systems of this kind which have been proposed. I have there especially discussed the system proposed in the treatise of M. Necker, Le Règne Minéral ramené aux Méthodes d'Histoire Naturelle (Paris, 1835). More recently have been published M. Beudant's Cours élémentaire d'Histoire Naturelle, Minéralogie (Paris, 1841); and M. A. Dufresnoy's Traité de Minéralogie (Paris, 1845). Both these works are so far governed by mere chemical views that they lapse into the inconveniences and defects which are avoided in the best systems of German mineralogists.

The last mineral system of Berzelius has been developed by M. Rammelsberg (Nürnberg, 1847). It is in principle such as we have described it in the history.

M. **Nordenskiöld's system (3rd Ed. 1849,) has been criticised by G. Rose, who observes that it removes the defects of the system of Berzelius only in part. He himself proposes what he calls a "Krystallo-Chemisches System," in which the crystalline form determines the genus and the chemical composition the species. His classes are-- 1. Simple Substances. 2. Combinations of Sulphur, Selenium, Titanium, Arsenic, Antimony. 3. Chlorides, Fluorides, Bromides, Iodides. 4. Combinations with Oxygen.

We have already said that for us, all chemical compounds are minerals, in so far that they are included in our classifications. The propriety of this mode of dealing with the subject is confirmed by our finding that there is really no tenable distinction between native minerals and the products of the laboratory. A great number of eminent chemists have been employed in producing, by artificial means, crystals which had before been known only as native products.

{{631}} BOOK XVI.

CLASSIFICATORY SCIENCES.

BOTANY.

FOR the purpose of giving to my reader some indication of the present tendency of Botanical Science, I conceive that I cannot do better than direct his attention to the reflections, procedure, and reasonings which have been suggested by the most recent extensions of man's knowledge of the vegetable world. And as a specimen of these, I may take the labors of Dr. Joseph Hooker, on the Flora of the Antarctic Regions,[41\B] and especially of New Zealand. Dr. Hooker was the Botanist to an expedition commanded by Sir James Ross, sent out mainly for the purpose of investigating the phenomena of Terrestrial Magnetism near the South Pole; but directed also to the improvement of Natural History. The extension of botanical descriptions and classifications to a large mass of new objects necessarily suggests wider views of the value of classes (genera, species, &c.,) and the conclusions to be drawn from their constancy or inconstancy. A few of Dr. Hooker's remarks may show the nature of the views taken under such circumstances.

[Note 41\B: _The Botany of the Antarctic Voyage of H. M. Discovery Ships Erebus and Terror, in the years_ 1839-40. Published 1847. Flora Novæ Zelandiæ. 1853.]

I may notice, in the first place, (since this work is intended for general rather than for scientific readers,) Dr. Hooker's testimony to the value of a technical descriptive language for a classificatory science--a Terminology, as it is called. He says, "It is impossible to write Botanical descriptions which a person ignorant of Botany can understand, although it is supposed by many unacquainted with science that this can and should be done." And hence, he says, the state of botanical science demands Latin descriptions of the plants; and this is a lesson which he especially urges upon the Colonists who study the indigenous plants. {632}

Dr. Hooker's remarks on the limits of species, their dispersion and variation, are striking and instructive. He is of opinion that species vary more, and are more widely diffused, than is usually supposed. Hence he conceives that the number of species has been needlessly and erroneously multiplied, by distinguishing the specimens which occur in different places, and vary in unessential features. He says that though, according to the lowest estimate of compilers, 100,000 is the commonly received number of known plants, he thinks that half that number is much nearer the truth. "This," he says, "may be well conceived, when it is notorious that nineteen species have been made of the Common Potatoe, and many more of Solanum nigrum alone. Pteris aquilina has given rise to numerous book species; Vernonia cinerea of India to fifteen at least. . . . . . . Many more plants are common to most countries than is supposed; I have found 60 New Zealand flowering plants and 9 Ferns to be European ones, besides inhabiting numerous intermediate countries. . . . . . So long ago as 1814, Mr. Brown drew attention to the importance of such considerations, and gave a list of 150 European plants common to Australia."

As an example of the extent to which unessential differences may go, he says (p. xvii.,) "The few remaining native Cedars of Lebanon may be abnormal states of the tree which was once spread over the whole of the Lebanon; for there are now growing in England varieties of it which have no existence in a wild state. Some of them closely resemble the Cedars of Atlas and of the Himalayas (Deodar;) and the absence of any valid botanical differences tends to prove that all, though generally supposed to be different species, are one."

Still the great majority of the species of plants in those Southern regions are peculiar. "There are upwards of 100 genera, subgenera, or other well marked groups of plants, entirely or nearly confined to New Zealand, Australia, and extra-tropical South America. They are represented by one or more species in two or more of those countries, and thus effect a botanical relationship or affinity between them all which every botanist appreciates."

In reference to the History of Botany, I have received corrections and remarks from Dr. Hooker, with which I am allowed to enrich my pages.

"P. 359. Note ^3. ~= Note 3\16~ Nelumbium speciosum, the Lotus of India. The Nelumbium does not float, but raises both leaf and flower several feet above the water: the Nymphæa Lotus has floating leaves. Both enter largely into the symbolism of the Hindoos, and are often confounded. {633}

"P. 362. Note ^5. ~= Note 13\16~ For Arachnis read Arachis. The Arachidna of Theophrastus cannot, however, be the Arachis or ground-nut.

"Pp. 388 and 394. For Harlecamp read Hartecamp.

"P. 394. For Kerlen read Kalm.

"P. 394. For Asbech read Osbeck.

"P. 386. John Ray. Ray was further the author of the present Natural System in its most comprehensive sense. He first divided plants into Flowerless and Flowering; and the latter into Monocotyledonous and Dicotyledonous:--'Floriferas dividemus in DICOTYLEDONES, quarum semina sata binis foliis, seminalibus dictis, quæ cotyledonorum usum præstant, e terra exeunt, vel in binos saltem lobos dividuntur, quamvis eos supra terram foliorum specie non efferant; et MONOCOTYLEDONES, quæ nec folia bina seminalia efferunt nec lobos binos condunt. Hæc divisio ad arbores etiam extendi potest; siquidem Palmæ et congeneres hoc respectu eodem modo a reliquis arboribus differunt quo Monocotyledones a reliquis herbis.'

"P. 408. Endogenous and Exogenous Growth. The exact course of the wood fibres which traverse the stems of both Monocotyledonous and Dicotyledonous plants has been only lately discovered. In the Monocotyledons, those fibres are collected in bundles, which follow a very peculiar course:--from the base of each leaf they may be followed downwards and inwards, towards the axis of the trunk, when they form an arch with the convexity to the centre; and curving outwards again reach the circumference, where they are lost amongst the previously deposited fibres. The intrusion of the bases of these bundles amongst those already deposited, causes the circumference of the stem to be harder than the centre; and as all these arcs have a short course (their chords being nearly equal), the trunk does not increase in girth, and grows at the apex only. The wood-bundles are here definite. In the Dicotyledonous trunks, the layers of wood run in parallel courses from the base to the top of the trunk, each externally to that last formed, and the trunk increases both in height and girth; the wood-bundles are here indefinite.

"With regard to the Cotyledons, though it is often difficult to distinguish a Monocotyledonous Embryo from a Dicotyledonous, they may always be discriminated when germinating. The Cotyledons, when two or more, and primordial leaves (when no Cotyledons are visible) of a Monocotyledon, are alternate; those of a Dicotyledon are opposite.

"A further physiological distinction between Monocotyledons and {634} Dicotyledons is observed in germination, when the Dicotyledonous radicle elongates and forms the root of the young plant; the Monocotyledonous radicle does not elongate, but pushes out rootlets from itself at once. Hence the not very good terms, exorhizal for Dicotyledonous, and endorhizal for Monocotyledonous.

"The highest physiological generalization in the vegetable kingdom is between Phænogama and Cryptogama. In the former, fertilization is effected by a pollen-tube touching the nucleus of an ovule; in Cryptogams, the same process is effected by the contact of a sperm-cell, usually ciliated (antherozoid), upon another kind of cell called a germ-cell. In Phænogams, further, the organs of fructification are all modified leaves; those of Cryptogams are not homologous." (J. D. H.)

ZOOLOGY.

I have exemplified the considerations which govern zoological classification by quoting the reflexions which Cuvier gives us, as having led him to his own classification of Fishes. Since the varieties of Quadrupeds, or Mammals (omitting whales, &c.), are more familiar to the common reader than those of Fishes, I may notice some of the steps in their classification; the more so as some curious questions have recently arisen thereupon.

Linnæus first divides Mammals into two groups, as they have Claws, or Hoofs (unguiculata, ungulata.) But he then again divides them into six orders (omitting whales, &c.), according to their number of incisor, laniary, and molar teeth; namely:-- Primates. (Man, Monkey, &c.) Bruta. (Rhinoceros, Elephant, &c.) Feræ. (Dog, Cat, Bear, Mole, &c.) Glires. (Mouse, Squirrel, Hare, &c.) Pecora. (Camel, Giraffe, Stag, Goat, Sheep, Ox, &c.) Belluæ. (Horse, Hippopotamus, Tapir, Sow, &c.)

In the place of these, Cuvier, as I have stated in the Philosophy (On the Language of Sciences, Aphorism xvi.), introduced the following orders: Bimanes, Quadrumanes, Carnassiers, Rongeurs, Edentés, Pachyderms, Ruminans. Of these, the Carnassiers correspond to the Feræ of Linnæus; the Rongeurs to his Glires; the Edentés are a new order, taking the Sloths, Ant-eaters, &c., from the Bruta of Linnæus, the Megatherium from extinct animals, and the Ornithorhynchus, &c., from the new animals of Australia; the Ruminans agree with the {635} Pecora; the Pachyderms include some of the Bruta and the Belluæ, comprehending also extinct animals, as Anoplotherium and Palæotherium.

But the two orders of Hoofed Animals, the Pachyderms and the Ruminants, form a group which is held by Mr. Owen to admit of a better separation, on the ground of a character already pointed out by Cuvier; namely, as to whether they are two-toed or three-toed. According to this view, the Horse is connected with the Tapir, the Palæotherium, and the Rhinoceros, not only by his teeth, but by his feet, for he has really three digits. And Cuvier notices that in the two-toed or even-toed Pachyderms, the astragalus bone has its face divided into two equal parts by a ridge; while in the uneven-toed pachyderms it has a narrow cuboid face. Mr. Owen has adopted this division of Pachyderms and Ruminants, giving the names artiodactyla and perissodactyla to the two groups; the former including the Ox, Hog, Peccary, Hippopotamus, &c.; the latter comprehending the Horse, Tapir, Rhinoceros, Hyrax, &c. And thus the Ruminants take their place as a subordinate group of the great natural even-toed Division of the Hoofed Section of Mammals; and the Horse is widely separated from them, inasmuch as he belongs to the odd-toed division.[42\B]

[Note 42\B: Owen, Odontography.]

As we have seen, these modern classifications are so constructed as to include extinct as well as living species of animals; and indeed the species which have been discovered in a fossil state have tended to fill up the gaps in the series of zoological forms which had marred the systems of modern zoologists. This has been the case with the division of which we are speaking.

Mr. Owen had established two genera of extinct Herbivorous Animals, on the strength of fossil remains brought from South America:--Toxodon, and Nesodon. In a recent communication to the Royal Society[43\B] he has considered the bearing of these genera upon the divisions of odd-toed and even-toed animals. He had already been led to the opinion that the three sections, Proboscidea, Perissodactyla, and Artiodactyla, formed a natural division of Ungulata; and he is now led to think that this division implies another group, "a distinct division of the Ungulata, of equal value, if not with the Perissodactyla and Artiodactyla at least with the Proboscidea. This group he proposes to call Toxodonta.

[Note 43\B: Phil. Trans., 1853.]

{{636}} BOOK XVII.

PHYSIOLOGY AND COMPARATIVE ANATOMY.

VEGETABLE MORPHOLOGY.

Morphology in Linnæus.

I HAVE stated that Linnæus had some views on this subject. Dr. Hooker conceives these views to be more complete and correct than is generally allowed, though unhappily clothed in metaphorical language and mixed with speculative matter. By his permission I insert some remarks which I have received from him.

The fundamental passage on this subject is in the Systema Naturæ; in the Introduction to which work the following passage occurs:--

"Prolepsis (Anticipation) exhibits the mystery of the metamorphosis of plants, by which the herb, which is the larva or imperfect condition, is changed into the declared fructification: for the plant is capable of producing either a leafy herb or a fructification. . . . . .

"When a tree produces a flower, nature anticipates the produce of five years where these come out all at once; forming of the bud-leaves of the next year bracts; of those of the following year, the calyx; of the following, the corolla; of the next, the stamina; of the subsequent, the pistils, filled with the granulated marrow of the seed, the terminus of the life of a vegetable."

Dr. Hooker says, "I derive my idea of his having a better knowledge of the subject than most Botanists admit, not only from the Prolepsis, but from his paper called Reformatio Botanices (Amœn. Acad. vol. vi.); a remarkable work, in respect of his candor in speaking of his predecessors' labors, and the sagacity he shows in indicating researches to be undertaken or completed. Amongst the latter is V. 'Prolepsis plantarum, ulterius extendenda per earum metamorphoses.' The last word occurs rarely in his Prolepsis; but when it does it seems to me that he uses it as indicating a normal change and not an accidental one. {637}

"In the Prolepsis the speculative matter, which Linnæus himself carefully distinguishes as such, must be separated from the rest, and this may I think be done in most of the sections. He starts with explaining clearly and well the origin and position of buds, and their constant presence, whether developed or not, in the axil of the leaf: adding abundance of acute observations and experiments to prove his statements. The leaf he declares to be the first effort of the plant in spring: he proceeds to show, successively, that bracts, calyx, corolla, stamens, and pistil are each of them metamorphosed leaves, in every case giving MANY EXAMPLES, both from monsters and from characters presented by those organs in their normal condition.

"The (to me) obscure and critical part of the Prolepsis was that relating to the change of the style of Carduus into two leaves. Mr. Brown has explained this. He says it was a puzzle to him, till he went to Upsala and consulted Fries and Wahlenberg, who informed him that such monstrous Cardui grew in the neighborhood, and procured him some. Considering how minute and masked the organs of Compositæ are, it shows no little skill in Linnæus, and a very clear view of the whole matter, to have traced the metamorphosis of all their floral organs into leaves, except their stamens, of which he says, 'Sexti anni folia e staminibus me non in compositis vidisse fateor, sed illorum loco folia pistillacea, quæ in compositis aut plenis sunt frequentissima.' I must say that nothing could well be clearer to my mind than the full and accurate appreciation which Linnæus shows of the whole series of phenomena, and their rationale. He over and over again asserts that these organs are leaves, every one of them,--I do not understand him to say that the prolepsis is an accidental change of leaves into bracts, of bracts into calyx, and so forth. Even were the language more obscure, much might be inferred from the wide range and accuracy of the observations he details so scientifically. It is inconceivable that a man should have traced the sequence of the phenomena under so many varied aspects, and shown such skill, knowledge, ingenuity, and accuracy in his methods of observing and describing, and yet missed the rationale of the whole. Eliminate the speculative parts and there is not a single error of observation or judgment; whilst his history of the developement of buds, leaves, and floral organs, and of various other obscure matters of equal interest and importance, are of a very high order of merit, are, in fact, for the time profound.

"There is nothing in all this that detracts from the merit of Goethe's {638} re-discovery. With Goethe it was, I think, a deductive process,--with Linnæus an inductive. Analyse Linnæus's observations and method, and I think it will prove a good example of inductive reasoning.

"P. 473. Perhaps Professor Auguste St Hilaire of Montpellier should share with De Candolle the honor of contributing largely to establish the metamorphic doctrine;--their labors were cotemporaneous.

"P. **474. Linnæus pointed out that the pappus was calyx: 'Et pappum gigni ex quarti anni foliis, in jam nominatis Carduis.'--Prol. Plant. 338." (J. D. H.)

VII. ANIMAL MORPHOLOGY

THE subject of Animal Morphology has recently been expanded into a form strikingly comprehensive and systematic by Mr. Owen; and supplied by him with a copious and carefully-chosen language; which in his hands facilitates vastly the comparison and appreciation of the previous labors of physiologists, and opens the way to new truths and philosophical generalizations. Though the steps which have been made had been prepared by previous anatomists, I will borrow my view of them mainly from him; with the less scruple, inasmuch as he has brought into full view the labors of his predecessors.

I have stated in the History that the skeletons of all vertebrate animals are conceived to be reducible to a single Type, and the skull reducible to a series of vertebræ. But inasmuch as this reduction includes not only a detailed correspondence of the bones of man with those of beasts, but also with those of birds, fishes, and reptiles, it may easily be conceived that the similarities and connexions are of a various and often remote kind. The views of such relations, held by previous Comparative Anatomists, have led to the designations of the bones of animals which have been employed in anatomical descriptions; and these designations having been framed and adopted by anatomists looking at the subject from different sides, and having different views of analogies and relations, have been very various and unstable; besides being often of cumbrous length and inconvenient form.

The corresponding parts in different animals are called homologues, {639} a term first applied to anatomy by the philosophers of Germany; and this term Mr. Owen adopts, to the exclusion of terms more loosely denoting identity or similarity. And the Homology of the various bones of vertebrates having been in a great degree determined by the labors of previous anatomists, Mr. Owen has proposed names for each of the bones: the condition of such names being, that the homologues in all vertebrates shall be called by the same name, and that these names shall be founded upon the terms and phrases in which the great anatomists of the 16th, 17th, and 18th centuries expressed the results of their researches respecting the human skeleton. These names, thus selected, so far as concerned the bones of the Head of Fishes, one of the most difficult cases of this Special Homology, he published in a Table,[44\B] in which they were compared, in parallel columns, with the names or phrases used for the like purpose by Cuvier, Agassiz, Geoffroy, Hallman, Sœmmering, Meckel, and Wagner. As an example of the considerations by which this selection of names was determined, I may quote what he says with regard to one of these bones of the skull.

[Note 44\B: Lectures on Vertebrates. 1846, p. 158. And On the Archetype and Homologies of the Vertebrate Skeleton. 1848, p. 172.]

"With regard to the 'squamosal' (squamosum. Lat. pars squamosa ossis temporis.--Sœmmering), it might be asked why the term 'temporal' might not be retained for this bone. I reply, because that term has long been, and is now universally, understood in human anatomy to signify a peculiarly anthropotomical coalesced congeries of bones, which includes the 'squamosal' together with the 'petrosal,' the 'tympanic,' the 'mastoid,' and the 'stylohyal.' It seems preferable, therefore, to restrict the signification of the term 'temporal' to the whole (in Man) of which the 'squamosal' is a part. To this part Cuvier has unfortunately applied the term 'temporal' in one class, and 'jugal' in another; and he has also transferred the term 'temporal' to a third equally distinct bone in fishes; while to increase the confusion M. Agassiz has shifted the name to a fourth different bone in the skull of fishes. Whatever, therefore, may be the value assigned to the arguments which will be presently set forth, as to the special homologies of the 'pars squamosa ossis temporis,' I have felt compelled to express the conclusion by a definite term, and in the present instance, have selected that which recalls the best accepted anthropomorphical designation of the part; although 'squamosal' must be understood and applied in an arbitrary sense; and not as descriptive of a scale-like {640} form; which in reference to the bone so called, is rather its exceptional than normal figure in the vertebrate series."

The principles which Mr. Owen here adopts in the selection of names for the parts of the skeleton are wise and temperate. They agree with the aphorisms concerning the language of science which I published in the Philosophy of the Inductive Sciences; and Mr. Owen does me the great honor of quoting with approval some of those Aphorisms. I may perhaps take the liberty of remarking that the system of terms which he has constructed, may, according to our principles, be called rather a Terminology **than a Nomenclature: that is, they are analogous more nearly to the terms by which botanists describe the parts and organs of plants, than to the names by which they denote genera and species. As we have seen in the History, plants as well as animals are subject to morphological laws; and the names which are given to organs in consequence of those laws are a part of the Terminology of the science. Nor is this distinction between Terminology and Nomenclature without its use; for the rules of prudence and propriety in the selection of words in the two cases are different. The Nomenclature of genera and species may be arbitrary and casual, as is the case to a great extent in Botany and in Zoology, especially of fossil remains; names being given, for instance, simply as marks of honor to individuals. But in a Terminology, such a mode of derivation is not admissible: some significant analogy or idea must be adopted, at least as the origin of the name, though not necessarily true in all its applications, as we have seen in the case of the "squamosal" just quoted. This difference in the rules respecting two classes of scientific words is stated in the Aphorisms xiii. and xiv. concerning the Language of Science.

Such a Terminology of the bones of the skeletons of all vertebrates as Mr. Owen has thus propounded, cannot be otherwise than an immense acquisition to science, and a means of ascending from what we know already to wider truths and new morphological doctrines.

With regard to one of these doctrines, the resolution of the human head into vertebræ, Mr. Owen now regards it as a great truth, and replies to the objections of Cuvier and M. Agassiz, in detail.[45\B] He gives a Table in which the Bones of the Head are resolved into four vertebræ, which he terms the Occipital, Parietal, Frontal, and Nasal Vertebra, respectively. These four vertebræ agree in general with what Oken called the Ear-vertebra, the Jaw-vertebra, the Eye-vertebra, and {641} the Nose-vertebra, in his work On the Signification of the Bones of the Skull, published in 1807: and in various degrees, with similar views promulgated by Spix (1815), Bojanus (1818), Geoffroy (1824), Carus **(1828). And I believe that these views, bold and fanciful as they at first appeared, have now been accepted by most of the principal physiologists of our time.

[Note 45\B: Archetype and Homologies of the Vertebrate Skeleton. 1848, p. 141.]

But another aspect of this generalization has been propounded among physiologists; and has, like the others, been extended, systematized, and provided with a convenient language by Mr. Owen. Since animal skeletons are thus made up of vertebræ and their parts are to be understood as developements of the parts of vertebræ, Geoffroy (1822), Carus (1828), Müller (1834), Cuvier (1836), had employed certain terms while speaking of such developements; Mr. Owen in the Geological Transactions in 1838, while discussing the osteology of certain fossil Saurians, used terms of this kind, which are more systematic than those of his predecessors, and to which he has given currency by the quantity of valuable knowledge and thought which he has embodied in them.

According to his Terminology,[46\B] a vertebra, in its typical completeness, consists of a central part or centrum; at the back of this, two plates (the neural apophyses) and a third outward projecting piece (the neural spine), which three, with the centrum, form a canal for the spinal marrow; at the front of the centrum two other plates (the hæmal apophyses) and a projecting piece, forming a canal for a vascular trunk. Further lateral elements (pleuro-apophyses) and other projections, are in a certain sense dependent on these principal bones; besides which the vertebra may support diverging appendages. These parts of the vertebra are fixed together, so that a vertebra is by some anatomists described as a single bone; but the parts now mentioned are usually developed from distinct and independent centres, and are therefore called by Mr. Owen "autogenous" elements.

[Note 46\B: Archetype and Homologies of the Vertebrate Skeleton. 1848, p. 81.]

The General Homology of the vertebral skeleton is the reference of all the parts of a skeleton to their true types in a series of vertebræ: and thus, as special homology refers all the parts of skeletons to a given type of skeleton, say that of Man, general homology refers all the parts of every skeleton, say that of Man, to the parts of a series of Vertebræ. And thus as Oken propounded his views of the Head as a resolution of the Problem of the Signification of the Bones of the Head, {642} so have we in like manner, for the purposes of General Homology, to solve the Problem of the Signification of Limbs. The whole of the animal being a string of vertebræ, what are arms and legs, hands and paws, claws and fingers, wings and fins, and the like? This inquiry Mr. Owen has pursued as a necessary part of his inquiries. In giving a public lecture upon the subject in 1849,[47\B] he conceived that the phrase which I have just employed would not be clearly apprehended by an English Audience, and entitled his Discourse "On the Nature of Limbs:" and in this discourse he explained the modifications by which the various kinds of limbs are derived from their rudiments in an archetypal skeleton, that is, a mere series of vertebræ without head, arms, legs, wings, or fins.

[Note 47\B: On the Nature of Limbs, a discourse delivered at a Meeting of the Royal Institution, 1849.]

Final Causes

It has been mentioned in the History that in the discussions which took place concerning the Unity of Plan of animal structure, this principle was in some measure put in opposition to the principle of Final Causes: Morphology was opposed to Teleology. It is natural to ask whether the recent study of Morphology has affected this antithesis.

If there be advocates of Final Causes in Physiology who would push their doctrines so far as to assert that every feature and every relation in the structure of animals have a purpose discoverable by man, such reasoners are liable to be perpetually thwarted and embarrassed by the progress of anatomical knowledge; for this progress often shows that an arrangement which had been explained and admired with reference to some purpose, exists also in cases where the purpose disappears; and again, that what had been noted as a special teleological arrangement is the result of a general morphological law. Thus to take an example given by Mr. Owen: that the ossification of the head originates in several centres, and thus in its early stages admits of compression, has been pointed out as a provision to facilitate the birth of viviparous animals; but our view of this provision is disturbed, when we find that the same mode of the formation of the bony framework takes place in animals which are born from an egg. And the number of points from which ossification begins, depends in a wider sense on the general homology of the animal frame, according to which each part is composed of a certain number of autogenous vertebral elements. In this {643} way, the admission of a new view as to Unity of Plan will almost necessarily displace or modify some of the old views respecting Final Causes.

But though the view of Final Causes is displaced, it is not obliterated; and especially if the advocate of Purpose is also ready to admit visible correspondences which have not a discoverable object, as well as contrivances which have. And in truth, how is it possible for the student of anatomy to shut his eyes to either of these two evident aspects of nature? The arm and hand of man are made for taking and holding, the wing of the sparrow is made for flying; and each is adapted to its end with subtle and manifest contrivance. There is plainly Design. But the arm of man and the wing of the sparrow correspond to each other in the most exact manner, bone for bone. Where is the Use or the Purpose of this correspondence? If it be said that there may be a purpose though we do not see it, that is granted. But Final Causes for us are contrivances of which we see the end; and nothing is added to the evidence of Design by the perception of a unity of plan which in no way tends to promote the design.

It may be said that the design appears in the modification of the plan in special ways for special purposes;--that the vertebral plan of an animal being given, the fore limbs are modified in Man and in Sparrow, as the nature and life of each require. And this is truly said; and is indeed the truth which we are endeavoring to bring into view:--that there are in such speculations, two elements; one given, the other to be worked out from our examination of the case; the datum and the problem; the homology and the teleology.

Mr. Owen, who has done so much for the former of these portions of our knowledge, has also been constantly at the same time contributing to the other. While he has been aiding our advances towards the Unity of Nature, he has been ever alive to the perception of an Intelligence which pervades Nature. While his morphological doctrines have moved the point of view from which he sees Design, they have never obscured his view of it, but, on the contrary, have led him to present it to his readers in new and striking aspects. Thus he has pointed out the final purposes in the different centres of ossification of the long bones of the limbs of mammals, and shown how and why they differ in this respect from reptiles (Archetype, p. 104). And in this way he has been able to point out the insufficiency of the rule laid down both by Geoffroy St. Hilaire and Cuvier, for ascertaining the true number of bones in each species. {644}

Final Causes, or Evidences of Design, appear, as we have said, not merely as contrivances for evident purposes, but as modifications of a given general Plan for special given ends. If the general Plan be discovered after the contrivance has been noticed, the discovery may at first seem to obscure our perception of Purpose; but it will soon be found that it merely transfers us to a higher point of view. The adaptation of the Means to the End remains, though the Means are parts of a more general scheme than we were aware of. No generalization of the Means can or ought permanently to shake our conviction of the End; because we must needs suppose that the Intelligence which contemplates the End is an intelligence which can see at a glance along a vista of Means, however long and complex. And on the other hand, no special contrivance, however clear be its arrangement, can be unconnected with the general correspondences and harmonies by which all parts of nature are pervaded and bound together. And thus no luminous teleological point can be extinguished by homology; nor, on the other hand, can it be detached from the general expanse of homological light.

The reference to Final Causes is sometimes spoken of as unphilosophical, in consequence of Francis Bacon's comparison of Final Causes in Physics to Vestal Virgins devoted to God, and barren. I have repeatedly shown that, in Physiology, almost all the great discoveries which have been made, have been made by the assumption of a purpose in animal structures. With reference to Bacon's simile, I have elsewhere said that if he had had occasion to develope its bearings, full of latent meaning as his similes so often are, he would probably have said that to those Final Causes barrenness was no reproach, seeing they ought to be not the Mothers but the Daughters of our Natural Sciences; and that they were barren, not by imperfection of their nature, but in order that they might be kept pure and undefiled, and so fit ministers in the temple of God. I might add that in Physiology, if they are not Mothers, they are admirable Nurses; skilful and sagacious in perceiving the signs of pregnancy, and helpful in bringing the Infant Truth into the light of day.

There is another aspect of the doctrine of the Archetypal Unity of Composition of Animals, by which it points to an Intelligence from which the frame of nature proceeds; namely this:--that the Archetype of the Animal Structure being of the nature of an Idea, implies a mind in which this Idea existed; and that thus Homology itself points the way to the Divine Mind. But while we acknowledge the full {645} value of this view of theological bearing of physiology, we may venture to say that it is a view quite different from that which is described by speaking of "Final Causes," and one much more difficult to present in a lucid manner to ordinary minds.

{{646}} BOOK XVIII.

GEOLOGY.

WITH regard to Geology, as a Palætiological Science, I do not know that any new light of an important kind has been thrown upon the general doctrines of the science. Surveys and examinations of special phenomena and special districts have been carried on with activity and intelligence; and the animals of which the remains people the strata, have been reconstructed by the skill and knowledge of zoologists:--of such reconstructions we have, for instance, a fine assemblage in the publications of the Palæontological Society. But the great questions of the manner of the creation and succession of animal and vegetable species upon the earth remain, I think, at the point at which they were when I published the last edition of the History.

I may notice the views propounded by some chemists of certain bearings of Mineralogy upon Geology. As we have, in mineral masses, organic remains of former organized beings, so have we crystalline remains of former crystals; namely, what are commonly called pseudomorphoses--the shape of one crystal in the substance of another. M. G. Bischoff[48\B] considers the study of pseudomorphs as important in geology, and as frequently the only means of tracing processes which have taken place and are still going on in the mineral kingdom.

[Note 48\B: Chemical and Physical Geology.]

I may notice also Professor Breithaupt's researches on the order of succession of different minerals, by observing the mode in which they occur and the order in which different crystals have been deposited, promise to be of great use in following out the geological changes which the crust of the globe has undergone. (Die Paragenesis der Mineralien. Freiberg. 1849.)

In conjunction with these may be taken M. de Senarmont's experiments on the formation of minerals in veins; and besides Bischoff's {647} Chemical Geology, Sartorius von Walterhausen's Observations on the occurrence of minerals in Amygdaloid.

As a recent example of speculations concerning Botanical Palætiology, I may give Dr. Hooker's views of the probable history of the Flora of the Pacific.

In speculating upon this question, Dr. Hooker is led to the discussion of geological doctrines concerning the former continuity of tracts of land which are now separate, the elevation of low lands into mountain ranges in the course of ages, and the like. We have already seen, in the speculations of the late lamented Edward Forbes, (see Book xviii. chap. vi. of this History,) an example of a hypothesis propounded to account for the existing Flora of England: a hypothesis, namely, of a former Connexion of the West of the British Isles with Portugal, of the Alps of Scotland with those of Scandinavia, and of the plains of East Anglia with those of Holland. In like manner Dr. Hooker says (p. xxi.) that he was led to speculate on the possibility of the plants of the Southern Ocean being the remains of a Flora that had once spread over a larger and more continuous tract of land than now exists in the ocean; and that the peculiar Antarctic genera and species may be the vestiges of a Flora characterized by the predominance of plants which are now scattered throughout the Southern islands. He conceives this hypothesis to be greatly supported by the observations and reasonings of Mr. Darwin, tending to show that such risings and sinkings are in active progress over large portions of the continents and islands of the Southern hemisphere: and by the speculations of Sir C. Lyell respecting the influence of climate on the migrations of plants and animals, and the influence of geological changes upon climate.

In Zoology I may notice (following Mr. Owen)[49\B] recent discoveries of the remains of the animals which come nearest to man in their structure. At the time of Cuvier's death, in 1832, no evidence had been obtained of fossil Quadrumana; and he supposed that these, as well as Bimana, were of very recent introduction. Soon after, in the oldest (eocene) tertiary deposits of Suffolk, remains were found proving the existence of a monkey of the genus Macacus. In the Himalayan tertiaries were found petrified bones of a Semnopithecus; in Brazil, remains of an extinct platyrhine monkey of great size; and lastly, in the middle tertiary series of the South of France, was discovered a fragment of the jaw of the long-armed ape (Hylobates). But no fossil human {648} remains have been discovered in the regularly deposited layers of any divisions (not even the pleiocene) of the tertiary series; and thus we have evidence that the placing of man on the earth was the last and peculiar act of Creation.

[Note 49\B: Brit. Asso. 1854, p. 112.]

THE END.

Transcriber's Notes

Whewell's book was originally published in 3 volumes in London in 1837. A second edition appeared in 1847, and a third in 1857. A 2-volume version of the 3rd edition was published in New York in 1858, reprinted 1875. This Project Gutenberg text, combining both volumes in sequence, was derived from the 1875 version, relying upon resources kindly provided by the Internet Archive.

Three items have been added to the Contents of the First Volume; they are marked off by ~ ~, as are any other additions to the text.

Printed page numbers have been transcribed in { }; pages without a printed number have been indicated by {{ }}. Where words were hyphenated across pages, the number has been placed before the word.

Fractions have been transcribed as numerator/denominator, occasionally using parentheses to disambiguate. The original sometimes has numerator over a line with denominator below, at other times numerator hyphen denominator. Superscripted characters are marked by a ^ before the character.

Footnotes in the original text were numbered by chapter; here they have been numbered by Book (the number of which is given after a \, for the two appendices to the 3rd edition A has been used for volume 1, B for volume 2). They are placed after the paragraph in which they occur, and are transcribed [Note m\n: ...]. Footnote anchors are transcribed [m\n]. All other square brackets are in the original text.

One difficult item is the use of numbers within a ring as names of asteroids; here the numbers are in ( ).

Corrections to the text have been marked with **. They are listed below, and were usually confirmed by reference to English printings of the text. Inconsistencies, especially with respect to accents and formatting, are numerous and have in general not been adjusted, though Greek quotations have been checked against other versions where available. Nor have Whewell's unbalanced quotation marks been modernised. The English versions have been used to restore Whewell's "gesperrt" emphases in some Greek passages.

Location 1875 Text Correction Vol. 1 p. 25 Cruikshanks Cruickshank p. 30 19 65 p. 30 : ; p. 33 (thrice) 184 182 p. 36 184 182 p. 71 Arisotelians Aristotelians p. 75 " p. 79 σερματικοὶ σπερματικοὶ p. 101 " note 1\2 6 7 p. 175 ecliptical elliptical note 1\4 iv. vi. note 75\4 Summæ Summa note 10\5 iii. iv. p. 271 (twice) Mastlin Mæstlin p. 282 _Dialogo "_Dialogo p. 284 semil semel p. 287 endeaver endeavor note 7\6 1. i. note 8\6 Dial. i. p. 40. p. 141. note 9\6 _Speculutionum _Speculationum p. 325 Gualtier Gualter p. 341 and 342 Marsenne Mersenne p. 374 of p. 377 prependicularity perpendicularity p. 403 " note 30\7 Cosmotheros Cosmotheoros p. 415 casual causal p. 416 ) p. 419 ] p. 431 a a note 69\7 1453 1753 note 84\7 Ast. Ass. p. 463 Philosphical Philosophical p. 471 ] p. 564 prevalance prevalence Vol. 2 p. 50 Ὑφιφάνη Ὑψιφάνη ἄρισπον ἄριστον οὔδιον εὔδιον p. 84 ] p. 85 viii. vii. p. 115 1853 1823 p. 149 , . p. 162 Footnote number missing in text p. 201 stream steam p. 213 and note 39\11 same number as the preceding note p. 240 Cruikshanks Cruickshank note 18\13 Mass-bestimmengen Mass-bestimmungen p. 264 in is note 11\14 _Stahl Stahl p. 295 the _the note 78\14 the entire text of this note is missing p. 301 lecture lectures note 87\14 96. 963. note 92\14 153 853 p. 330 Angels Angles p. 336 given giving p. 343 " p. 394 Surien Surian p. 411 Couérs Elmentaire Cours Elémentaire note 136\16 Εἴδην Εἴδη p. 450 dependance dependence p. 457 sucking-beasts suckling-beasts note 80\17 ählich ähnlich note 89\17 229 129 p. 477 osseuze osseuse note 119\17 229 299* p. 508 Lythophylaccii Lythophylacii p. 511 Stukely Stukeley note 18\18 Géognastique Géognostique p. 513 Sabapennine Sub-Apennine p. 514 Schlotheim Schlottheim p. 530 , ( ,) p. 556 Poissons Poisson's p. 620 iv. vii. p. 624 [ ( p. 628 in (not italicised in text) p. 630 Nordenskiold's Nordenskiöld's p. 638 390 474 p. 640 then than p. 641 1828 (1828)

* This is the page number given in the English edition. In the only version of the text referred to that I have found, the quotation is in a footnote on page 352 of the second edition (1805); the note was not in the first edition.