Cosmos: A Sketch of the Physical Description of the Universe Part 5

We will here subjoin one important observation by way of elucidating the connection of which we have spoken. The first general glance over the vegetation of a vast extent of a continent shows us forms the most dissimilar -- Graminae and Orchideae, Coniferae and oaks, in local approximation to one another; while natural families and genera, instead of being locally a.s.sociated, are dispersed as if by chance. This dispersion is, however, only apparent. The physical description of the globe teaches us that vegetation every where presents numerically constant relations in the development of its forms and types; that in the same climates, the species which are wanting in one country are replaced in a neighboring one by other species of the same family; and that this 'law of subst.i.tution', which seems to depend upon some inherent mysteries of the organism, considered with reference to its origin, maintains in contiguous regions a numerical relation between the species of various great families and the general ma.s.s of the phanerogamic plants const.i.tuting the two floras. We thus revealed in the multiplicity of the distinct organizations by which these regions are occupied; and we also discover in each zone, and diversified according to the families of plants, a slow but continuous action on the aerial ocean, depending upon the influence of light -- the primary condition of all organic vitality -- on the solid and liquid surface of our planet. It might be said, in accordance with a beautiful expression of Lavoisier, that the ancient marvel of the myth of Prometheus was incessantly renewed before our eyes.

If we extend the course which we have proposed, following in the exposition of the physical description of the earth to the sidereal part of the science of the Cosmos, the delineation of the regions of s.p.a.ce and the bodies by which they are occupied, we shall find our task simplified in no common degree. If, according to ancient but unphilosophical forms of nomenclature, we would distinguish between 'physics', that is to say, general considerations on the essence of matter, and the forces by which it is actuated, and 'chemistry', which treats of the nature of substances, their elementary composition, and those attractions that are not determined solely by the relations of ma.s.s, we must admit that the description of the earth comprises at p 63 once 'physical' and 'chemical' actions. In addition to gravitation, which must be considered as a primitive force in nature, we observe that attractions of another kind are at work around us, both in the interior of our planet and on its surface. These forces, to which we apply the term 'chemical affinity', act upon molecules in contact, or at infinitely minute distances from one another,* and which, being differently modified by electricity, heat, condensation in porous bodies, or by the contact of an intermediate substance, animate equally the inorganic world and animal and vegetable tissues.

[footnote] * On the question already discussed by Newton, regarding the difference existing between the attraction of ma.s.ses and molecular attraction, see Laplace, 'Exposition du Systeme du Monde', p. 384, and supplement to book x. of the 'Mecanique Celeste', p. 3, 4; Kant, 'Metaph.

Anfangegrunde der Naturwissenschaft, S?m. Werke', 1839, bd. v., s. 309 (Metaphysical Principles of the Natural Sciences); Pectet, 'Physique', 1838, vol. i., p. 59-63.

If we except the small asteroids, which appear to us under the forms of aerolites and shooting stars, the regions of s.p.a.ce have hitherto presented to our direct observation physical phenomena alone; and in the case of these, we know only with certainty the effects depending upon the quant.i.tative relations of matter of the distribution of ma.s.ses. The phenomena of the regions of s.p.a.ce may consequently be considered as influenced by simple dynamical laws -- the laws of motion.

The effects that may arise from the specific difference and the hererogeneous nature of matter have not hitherto entered into our calculations of the mechanism of the heavens. The only means by which the inhabitants of our planet can enter into relation with the matter contained within the regions of s.p.a.ce, whether existing in scattered forms or united into large spheroids, is by the phenomena of light, the propagation of the force of gravitation or the attraction of ma.s.ses. The existence of a periodical action of the sun and moon on the variations of terrestrial magnetism is even at the present day extremely problematical. We have no direct experimental knowledge regarding the properties and specific qualities of the ma.s.ses circulating in s.p.a.ce, or of the matter of which they are probably composed, if we except what may be derived from the fall of aerolites or meteoric stones, which, as we have already observed, enter within the limits of our terrestrial sphere. It will be sufficient here to remark, that the direction and the excessive velocity of projection (a velocity wholly planetary) manifested by these ma.s.ses, render it more than probable that p 64 they are small celestial bodies, which, being attracted by our planet, are made to deviate from their original course, and thus reach the earth enveloped in vapors, and in a high state of actual incandescence. The familiar aspect of these asteroids, and the a.n.a.logies which they present with the minerals composing the earth's crust, undoubtedly afford ample grounds for surprise,* but, in my opinion, the only conclusion to be drawn from these facts is that, in general, planets and other sidereal ma.s.ses, which by the influence of a central body, have been agglomerated into rings of vapor, and subsequently into spheroids, being integrant parts of the same system, and having one common origin, may likewise be composed of substances chemically identical.

[footnote] I[The a.n.a.lysis of an aerolite which fell a few years since in Maryland, United States, and was examined by Professor Silliman, of New Haven, Connecticut, gave the following results: Oxyd of iron, 24; oxyd of nickel, 1.25; silica, with earthy matter, 3.46; sulphur, a trace - 28.71.

Dr. Mantell's 'Wonders of Geology', 1848, vol. i., p. 51.] -- 'Tr.'

Again, experiments with the pendulum, particularly those prosecuted with such rare precision by Bessel, confirm the Newtonian axiom, that bodies the most heterogeneous in their nature (as water, gold, quartz, granular limestone, and different ma.s.ses of aerolites) experience a perfectly similar degree of acceleration from the attraction of the earth. To the experiments of the pendulum may be added the proofs furnished by purely astronomical observations. The almost perfect ident.i.ty of the ma.s.s of Jupiter, deduced from the influence exercised by this stupendous planet on its own satellites, on Enck's comet of short period, and on the small planets Vesta, Juno, Ceres, and Pallas, indicates with equal certainty that within the limits of actual observation attraction is determined solely by the quant.i.ty of matter.*

[footnote] *Poisson, 'Connaissances des Temps pour l'Anne' 1836, p. 64-66.

Bessel, Poggendorf's 'Annalen', bd. xxv., s. 417. Encke, 'Abhandlungen der Berliner Academie' (Trans. of the Berlin Academy), 1826, s. 257.

Mitscherlich, 'Lehrbuch der Chemie' (Manual of Chemistry), 1837 bd. i. s.

352.

This absence of any perceptible difference in the nature of matter, alike proved by direct observation and theoretical deductions, imparts a high degree of simplicity to the mechanism of the heavens. The immeasurable extent of the regions of s.p.a.ce being subjected to laws of motion alone, the sidereal portion of the science of the Cosmos is based on the pure and abundant source of mathematical astronomy, as is the terrestrial portion on physics, chemistry, and organic morphology; but the domain of these three last-named sciences embraces p 65 the consideration of phenomena which are so complicated and have, up to the present time, been found so little susceptible of the application of rigorous method, that the physical science of the earth can not boast of the same certainty and simplicity in the exposition of facts and their mutual connection which characterize the celestial portion of the Cosmos. It is not improbable that the difference to which we allude may furnish an explanation of the cause which, in the earliest ages of intellectual culture among the Greeks, directed the natural philosophy of the Pythagoreans with more ardor to the heavenly bodies and the regions of s.p.a.ce than to the earth and its productions, and how through Philolaus, and subsequently through the a.n.a.logous views of Aristarchus of Samos, and of Seleucus of Erythrea, this science has been made more conducive to the attainment of a knowledge of the true system of the world than the natural philosophy of the Ionian school could ever be to the physical history of the earth. Giving but little attention to the properties and specific differences of matter filling s.p.a.ce, the great Italian school, in its Doric gravity, turned by preference toward all that relates to measure, to the form of bodies, and to the number and distances of the planets,* while the Ionian physicists directed their attention to the qualities of matter, its true or supposed metamorphoses, and to relations of origin.

[footnote] *Compare Otfried Muller's 'Dorien', bd. i., s. 365.

It was reserved for the powerful genius of Aristotle, alike profoundly speculative and practical to sound with equal success the depths of abstraction and the inexhaustible resources of vital activity pervading the material world.

Several highly distinguished treatises on physical geography are prefaced by an introduction, whose purely astronomical sections are directed to the consideration of the earth in its planetary dependence, and as const.i.tuting a part of that great system which is animated by one central body, the sun.

This course is diametrically opposed to the one which I propose following.

In order adequately to estimate the dignity of the Cosmos, it is requisite that the sidereal portion, termed by Kant the 'natural history of the heavens', should not be made subordinate to the terrestrial. In the science of the Cosmos, according to the expression of Aristarchus of Samos, the pioneer of the Copernican system, the sun, with its satellites, was nothing more than one of the innumerable stars by which s.p.a.ce is occupied. The physical history of the world must, therefore, begin with the description of the heavenly bodies, p 66 and with a geographical sketch of the universe, or, I would rather say, a true 'map of th world', such as was traced by the bold hand of the elder Herschel. If, notwithstanding the smallness of our planet, the most considerable s.p.a.ce and the most attentive consideration be here afforded to that which exclusively concerns it, this arises solely from the disproportion in the extent of our knowledge of that which is accessible and of that which is closed to our observation. This subordination of the celestial to the terrestrial portion is met with in the great work of Bernard Varenius,* which appeared in the middle of the seventeenth century.

[Footnote] *'Geographia Generalis in qua affectiones generales telluris explicantur.' The oldest Elzevir edition bears date 1650, the second 1672, and the third 1681; these were published at Cambridge, under Newton's supervision. This excellent work by Varenius is, in the true sense of the words, a physical description of the earth. Since the work 'Historia Natural de las Indias', 1590, in which the Jesuit Joseph de Acosta sketched in so masterly a manner the delineation of the New Continent, questions relating to the physical history of the earth have never been considered with such admirable generality. Acosta is richer in original observations, while Varenius embraces a wider circle of ideas, since his sojourn in Holland, which was at that period the center of vast commercial relations, had brought him in contact with a great number of well-iinformed travelers.

'Generalis sive Universalis Geographia dictur quae tellurem in genere considerat atque affectiones explicat, non habita particularium regionum ratione.' The general description of the earth by Varenius ('Pars Absoluta', cap. i.-xxii.) may be considered as a treatise of comparative geography, if we adopt the term used by the author himself ('Geographia Comparativa', cap. x.x.xiii.-xl.), although this must be understood in a limited acceptation. We may cite the following among the most remarkable pa.s.sages of this book: the enumeration of the systems of mountains; the examination of the relations existing between their directions and the general form of continents (p. 66, 76, ed. Cantab., 1681); a list of extinct volcanoes, and such as were still in a state of activity; the discussion of facts relative to the general distribution of islands and archipelagoes (p.

220); the depth of the ocean relatively to the height of neighboring coasts (p. 103); the uniformity of level observed in all open seas (p. 97); the dependence of currents on the prevailing winds; the unequal saltness of the sea; the configuration of sh.o.r.es (p. 139); the direction of the winds as the result of differences of temperature, etc. We may further instance the remarkable considerations of Varenius regarding the equinoctial current from east to west, to which he attributes the origin of the Gulf Stream, beginning at Cape St. Augustin, and issuing forth between Cuba and Florida (p. 140). Nothing can be more accurate than his description of the current which skirts the western coast of Africa, between Cape Verde and the island of Fernando Po in the Gulf of Guinea. Varenius explains the formation of sporadic islands by supposing them to be "the raised bottom of the sea:"

'magna spirituum inclusorum vi, sicut aliquando montes e terra protusos esse quidam scribunt' (p. 225). The edition published by Newton in 1681 ('auctior et emendatior' unfortunately contains no additions from this great authority; and there is not even mention made of the polar compression of the globe, although the experiments on the pendulum by Richer had been made nine years prior to the appearance of the Cambridge edition. Newton's 'Principia Mathematica Philosophie Naturalis' were not communicated in ma.n.u.script to the Royal Society until April, 1686. Much uncertainty seems to prevail regarding the birth-place of Varenius. Jaecher says it was England, while, according to 'La Biographie Universelle' (b.xlvii., p. 495), he is stated to have been born at Amsterdam; but it would appear, from the dedicatory address to the burgomaster of that city (see his 'Geographia Comparativa', that both suppositions are false. Varenius expressly says that he had sought refuge in Amsterdam, "because his native city had been burned and completely destroyed during a long war," words which appear to apply to the north of Germany, and to the devastations of the Thirty Years'

War. In his dedication of another work, 'Descriptio regni j.a.poniae' (Amst., 1649), to the Senate of Hamburgh, Varenius says that he prosecuted his elementary mathematical studies in the gymnasium of that city. There is, therefore, every reason to believe that this admirable geographer was a native of Germany, and was probably born at Luneburg ('Witten. Mem. Theol.', 1685, p. 2142; Zedler, 'Universal Lexicon', vol. xlvi., 1745, p. 187).

p 67 He was the first to distinguish between 'general and special geography', the former of which he subdivides into an 'absolute', or, properly speaking, 'terrestrial' part, and a 'relative or planetary' portion, according to the mode of considering our planet either with reference to its surface in its different zones, or to its relations to the sun and moon. It redounds to the glory of Varenius that his work on 'General and Comparative Geography'

should in so high a degree have arrested the attention of Newton. The imperfect state of many of the auxiliary sciences from which this writer was obliged to draw his materials prevented his work from corresponding to the greatness of the design, and it was reserved for the present age, and for my own country, to see the delineation of comparative geography, drawn in its full extent, and in all its relations with the history of man, by the skillful hand of Carl Ritter.*

[Footnote] *Carl Ritter's 'Erdkunde im Verh?ltniss zur Natur und zur Geschichte des Menschen, oder allgemeine vergleichende Geographie'

(Geography in relation to Nature and the History of Man, or general Comparative Geography).

The enumeration of the most important results of the astronomical and physical sciences which in the history of the Cosmos radiate toward one common focus, may perhaps, to a certain degree, justify the designation I have given to my work, and, considered within the circ.u.mscribed limits I have proposed to myself, the undertaking may be esteemed less adventurous than the t.i.tle. The introduction of new terms, especially with reference to the general results of a science which p 68 ought to be accessible to all, has always been greatly in opposition to my own practice; and whenever I have enlarged upon the established nomenclature, it has only been in the specialities of descriptive botany and zoology, where the introduction of hitherto unknown objects rendered new names necessary. The denominations of physical descriptions of the universe, or physical cosmography, which I use indiscriminantely, have been modeled upon those of 'physical descriptions of the earth', that is to say, 'physical geography', terms that have long been in common use. Descartes, whose genius was one of the most powerful manifested in any age, has left us a few fragments of a great work, which he intended publishing under the t.i.tle of 'Monde', and for which he had prepared hiimself by special studies, including even that of human anatomy. The uncommon, but definite expression of the 'science of the Cosmos' recalls to the mind of the inhabitant of the earth that we are treating of a more widely-extended horizon -- of the a.s.semblage of all things with which s.p.a.ce is filled, from the remotest nebulae to the climatic distribution of those delicate tissues of vegetable matter which spread a variegated covering over the surface of our rocks.

The influence of narrow-minded views peculiar to the earlier ages of civilization led in all languages to a confusion of ideas in the synonymic use of the words 'earth' and 'world', while the common expressions 'voyages round the world', 'map of the world', and 'new world', afford further ill.u.s.trations of the same confusion. The more n.o.ble and precisely-defined expressions of 'system of the world', 'the planetary world', and 'creation and age of the world', relate either to the totality of the substances by which s.p.a.ce is filled, or to the origin of the whole universe.

It was natural that, in the midst of the extreme variability of phenomena presented by the surface of our globe, and the aerial ocean by which it is surrounded, man should have been impressed by the aspect of the vault of heaven, and the uniform and regular movements of the sun and planets. Thus the word Cosmos, which primitively, in the Homeric ages, indicated an idea of order and harmony, was subsequently adopted in scientific language, where it was gradually applied to the order observed in the movements of the heavenly bodies, to the whole universe, and then finally to the world in which this harmony was reflected to us. According to the a.s.sertion of Philolaus, whose fragmentary works have been so ably commented upon by B?ckh, and conformably to the general testimony p 69 of antiquity, Pythagoras was the first who used the word Cosmos to designate the order that reigns in the universe, or entire world.*

[footnote] *[Greek word], in the most ancient, and at the same time most precise, definition of the word, signified 'ornament' (as an adornment for a man, a woman, or a horse); taken figuratively for [Greek word], it implied the order or adornment of a discourse. According to the testimony of all the ancients, it was Pythagoras who first used the word to designate the order in the universe, and the universe itself. Pythagoras left no writings; but ancient attestation to the truth of this a.s.sertion is to be found in several pa.s.sages of the fragmentary works of Philolaus (Stob., 'Eclog.', p. 360 and 460, Heeren), p. 62, 90, in Bockh's German edition. I do not, according to the example of Nake, cite Timof Locris, since his authenticity is doubtful. Plutarch ('De plac. Phil.', ii., I) says, in the most express manner, that Pythatoras gave the name of Cosmos to the universe on account of the order which reigned throughout it; so likewise does Galen ('Hist. Phil.', p. 429). This word, together with its novel signification, pa.s.sed from the schools of philosophy into the language of poets and prose writers. Plato designates the heavenly bodies by the name of 'Uranos', but the order pervading the regions of s.p.a.ce he too terms the Cosmos, and in his 'Timus' (p. 30 a.) he says 'that the world is an animal endowed with a soul'

[Greek words]. Compare Anaxag. Claz., ed. Schaubach, p. III, and Plut.

('De plac. Phil.', in Aristotle ('De Caelo', I, 9), 'Cosmos' signifies "the universe and the order pervading it," but it is likewise considered as divided in s.p.a.ce into two parts -- the sublunary world, and the world above the moon. ('Meteor.', I., w, 1, and I., 3, 13, p. 339, 'a', and 340, 'b', Bekk.) The definition of Cosmos, which I have already cited is taken from Pseudo-Aristoteles 'de Mundo', cap. ii. (p. 391); the pa.s.sage referred to is as follows: [Greek words]. Most of the pa.s.sages occurring in Greek writers on the word 'Cosmos' may be found collected together in the controversy between Richard Bentley and Charles Boyle ('Opuscula Philologica', 1781, p.

347, 445; 'Dissertation upon the Epistles of Phalaris', 1817, p. 254); on the historical existence of Zaleucus, legislator of Leucris, in Nake's excellent work, 'Sched. Crit.', 1812, p. 9, 15; and, finally in Theophilus Schmidt, 'ad Cleom. Cycl. Theor.', met. I., 1, p. ix., 1 and 99. Taken in a more limited sense, the word Cosmos is also used in the plural (Plut., 1, 5), either to designate the stars (Stob., 1, p. 514; Plut., 11, 13) or the innumerable systems scattered like islands through the immensity of s.p.a.ce, and each composed of a sun and a moon. (Anax. Claz., 'Fragm.', p. 89, 93, 120; Brandis, 'Gesch. der Griechisch-R?mischen Philosophie', b. i., s. 252 (History of the Greco-Roman Philosophy). Each of these groups forming thus a 'Cosmos', the universe, [Greek words], the word must be understood in a wider sense (Plut., ii., 1). It was not until long after the time of the Ptolemies that the word was applied to the earth. Bockh has made known inscriptions in praise of Trajan and Adrian ('Corpus Inscr. Graec.', I, n.

334 and 1036), in which [Greek word] occurs for [Greek word] in the same manner as we still use the term 'world' to signify the earth alone. We have already mentioned the singular division of the regions of s.p.a.ce p 70 [Footnote continues]

into three parts, the 'Olympus, Cosmos' and 'Ouranos' (Stob., i., p. 488; Philolaus, p. 95, 303); this division applies to the different regions surrounding that mysterious focus of the universe, the [Greek words] of the Pythagoreans. In the fragmentary pa.s.sage in which this division is found, the term [Greek word] designates the innermost region, situated between the moon and earth; this is the domain of changing things. The middle region, where the planets circulate in an invariable and harmonious order, is, in accordance with the special conceptions entertained of the universe, exclusively termed 'Cosmos', while the word 'Olympus' is used to express the exterior or igneous region. Bopp, the profound philologist, has remarked that we may deduce, as Pott has done, 'Etymol. Forschungen', th.i., s. 39 and 252 ('Etymol. Researches'), the word [Greek word] from the Sanscrit root 'sud', 'purificari', by a.s.suming two conditions; first that the Greek letter 'kappa' in [Greek word] comes from the palatial 'epsilon', which Bopp represents by 's' and Pott by '' (in the same manner as [Greek word], 'decem, taihun' in Gothic, comes from the Indian word 'dasan'), and, next, that the Indian 'd'' corresponds, as a general rule, with the Greek 'theta'

('Vergleichende Grammatik' 99 -- Comparative Grammar), which shows the relation of [Greek word] (for [Greek word]) with the Sanscrit root 'sud', whence is also derived [Greek word]. Another Indian term for the world is 'gagat' (p.r.o.nounced 'dschagat'), which is, properly speaking the present participle of the verb 'gagami' (I go), the root of which is 'ga.' In restricting ourselves to the circle of h.e.l.lenic etymologies, we find ('Etymol. M.', p. 532, 12) that [Greek word] is intimately a.s.sociated with [Greek word] or rather with [Greek word], whence we have [Greek word] or [Greek word] Welcker ('Eine Kretische Col in Theben', s. 23 -- A Cretan Colony in Thebes) combines with this the name [Greek word] , as in Hesychius [Greek word] signifies a Cretan suit of arms. When the scientific language of Greece was introduced among the Romans, the word 'mundus', which at first had only the primary meaning of [Greek word] (female ornament), was applied to designate the entire universe. Ennius seems to have been the first who ventured upon this innovation. In one of the fragments of this poet, preserved by Macrobius, on the occasion of his quarrel with Virgil, we find the word used in its novel mode of acceptation: "Mundus caeli vastus const.i.tit silentio" (Sat., vi., 2). Cicero also says, "Quem nos lucentem mundum vocamus" (Timus, 'S.de univer.', cap. x.) The Sanscrit root 'mand'

from which Pott derives the Latin 'mundus' ('Etym. Forsch.', th. i., s.

240), combines the double signification of shining and adorning. 'Loka'

designates in Sanscrit the world and people in general, in the same manner as the French word 'monde', and is derived according to Bopp, from 'lok' (to see and shine); it is the same with the Slavonic root 'swjet', which means both 'light' and 'world.' (Grimm, 'Deutsche Gramm.', b. iii., s. 394 -- German Grammar.) The word 'welt', which the Germans make use of at the present day, and which was 'weralt' in old German, 'worold' in old Saxon, and 'weruld' in Anglo-Saxon, was, according to James Grimm's interpretation, a period of time, an age ('saeculum') rather than a term used for the world in s.p.a.ce. The Etruscans figured to themselves 'mundus' as an inverted dome, symmetrically opposed to the celestial vault (Otfried Muller's 'Etrusken', th. ii., s. 96, etc.). Taken in a still more limited sense, the word appears to have signified among the Goths the terrestrial surface girded by seas ('marei, meri',) the 'merigard', literally, 'garden of seas.'

From the Italian school of philosophy, the expression pa.s.sed, in this signification, into the language of those early poets p 71 of nature, Parmenides and Empedocles, and from thence into the works of prose writers. We will not here enter into a discussion of the manner in which, according to the Pythagorean views, Philolaus distinguishes between Olympus, Ura.n.u.s, or the heavens, and Cosmos, or how the same word, used in a plural sense, could be applied to certain heavenly bodies (the planets) revolving round one central focus of the world, or to groups of stars. In this work I use the word Cosmos in conformity with the h.e.l.lenic usage of the term subsequently to the time of Pythagorus, and in accordance with the precise definition given of it in the treatise ent.i.tled 'De Mundo', which was long erroneously attributed to Aristotle. It is the a.s.semblage of all things in heaven and earth, the universality of created things const.i.tuting the perceptible world. If scientific terms had not long been diverted from their true verbal signification, the present work ought rather to have borne the t.i.tle of 'Cosmography', divided into 'Uranography' and 'Geography.' The Romans, in their feeble essays on philosophy, imitated the Greeks by applying to the universe the term 'mundus', which, in its primary meaning, indicated nothing more than ornament, and did not even imply order or regularity in the disposition of parts. It is probable that the introduction into the language of Latium of this technical term as an equivalent for Cosmos, in its double signification, is due to Ennius,* who was a follower of the Italian school, and the translator of the writings of Epicharmus and some of his pupils on the Pythagorean philosophy.

[footnote] *See, on Ennius, the ingenious researches of Leopold Krahner, in his 'Grundlinien zur Geschichte des Verfalls der Romischen Staats-Reigion', 1837, s. 41-45 (Outlines of the History of the Decay of the Established Religion among the Romans). In all probability, Ennius did not quote from writings of Epicharmus himself, but from poems composed in the name of that philosopher, and in accordance with his views.

We would first distinguish between the physical 'history' and the physical 'description' of the world. The former, conceived in the most general sense of the word, ought, if materials for writing it existed, to trace the variations experienced by the universe in the course of ages from the new stars which have suddenly appeared and disappeared in the vault of heaven, from nebul dissolving or condensing -- to the first stratum of cryptogamic vegetation on the still imperfectly cooled surface of the earth, or on a reef of coral uplifted from the depths of ocean. 'The physical description of the world' presents a picture of all that exists in s.p.a.ce -- of the siimultaneous action of p 72 natural forces, together with the phenomena which they produce.

But if we would correctly comprehend nature, we must not entirely or absolutely separate the consideration of the present state of things from that of the successive phases through which they have pa.s.sed. We can not form a just conception of their nature without looking back on the mode of their formation. It is not organic matter alone that is continually undergoing change, and being dissolved to form new combinations. The globe itself reveals at every phase of its existence the mystery of its former conditions.

We can not survey the crust of our planet without recognizing the traces of the prior existence and destruction of an organic world. The sedimentary rocks present a succession of organic forms, a.s.sociated in groups, which have successively displaced and succeeded each other. The different super-imposed strata thus display to us the faunas and floras of different epochs. In this sense the description of nature is intimately connected with its history; and the geologist, who is guided by the connection existing among the facts observed, can not form a conception of the present without pursuing, through countless ages, the history of the past. In tracing the physical delineation of the globe, we behold the present and the past reciprocally incorporated, as it were, with one another; for the domain of nature is like that of languages, in which etymological research reveals a successive development, by showing us the primary condition of an idiom reflected in the forms of speech in use at the present day. The study of the material world renders this reflection of the past peculiarly manifest, by displaying in the process of formation rocks of eruption and sedimentary strata similar to those of former ages. If I may be allowed to borrow a striking ill.u.s.tration from the geological relations by which the physiognomy of a country is determined, I would say that domes of trachyte, cones of basalt, lava streams ('coules')of amygdaloid with elongated and parallel pores, and white deposits of pumice, intermixed with black scoriae, animate the scenery by the a.s.sociations of the past which they awaken, acting upon the imagination of the enlightened observer like traditional records of an earlier world. Their form is their history.

The sense in which the Greeks and Romans originally employed the word 'history' proves that they too were intimately convinced that, to form a complete idea of the present state of the universe, it was necessary to consider it in its successive p 73 phases. It is not, however, in the definition given by Valerius Flaccus,*

but in the zoological writings of Aristotle, that the word 'history'

presents itself as an exposition of the results of experience and observation.

[Footnote] *Aul. Gell., 'Nect. Att.', v., 18.

The physical description of the word by Pliny the elder bears the t.i.tle of 'Natural History', while in the letters of his nephew it is designated by the n.o.bler term of 'History of Nature.' The earlier Greek historians did not separate the description of countries from the narrative of events of which they had been the theater. With these writers, physical geography and history were long intimately a.s.sociated, and remained simply but elegantly blended until the period of the development of political interests, when the agitation in which the lives of men were pa.s.sed caused the geographical portion to be banished from the history of nations, and raised into an independent science.

It remains to be considered whether by the operation of thought, we may hope to reduce the immense diversity of phenomena comprised by the Cosmos to the unity of a principle, and the evidence afforded by rational truths. In the present state of empirical knowledge, we can scarcely flatter ourselves with such a hope. Experimental sciences, based on the observation of the external world, can not aspire to completeness; the nature of things, and the imperfection of our organs, are alike opposed to it. We shall never succeed in exhausting the immeasurable riches of nature; and no generation of men will ever have cause to boast of having comprehended the total aggregation of phenomena. It is only by distributing them into groups that we have been able, in the case of a few, to discover the empire of certain natural laws, grand and simple as nature itself. The extent of this empire will no doubt increase in proportion as physical sciences are more perfectly developed. Striking proofs of this advancement have been made manifest in our own day, in the phenomena of electro-magnetism, the propagation of luminous waves and radiating heat. In the same manner, the fruitful doctrine of evolution shows us how, in organic development, all that is formed is sketched out beforehand, and how the tissues of vegetable and animal matter uniformly arise from the multiplication and transformation of cells.

The generalization of laws, which, being at first bounded by narrow limits, had been applied solely to isolated groups of phenomena, acquires in time more marked gradations, and gains in extent and certainty as long as the process of reasoning p 74 is applied strictly to a.n.a.logous phenomena; but as soon as dynamical views prove insufficient where the specific properties and heterogeneous nature of matter come into play; it is to be feared that, by persisting in the pursuit of laws, we may find our course suddenly arrested by an impa.s.sible chasm.

The principle of unity is lost sight of, and the guiding clew is rent asunder whenever any specific and peculiar kind of action manifests itself amid the active forces of nature. The law of equivalents and the numerical proportions of composition, so happily recognized by modern chemists, and proclaimed under the ancient form of atomic symbols, still remains isolated and independent of mathematicl laws of motion and gravitation.