History of the Intellectual Development of Europe Volume II Part 14

[Sidenote: Limit of the theory of gravitation.] The theory of gravitation, as delivered by Newton, thus leads us to a knowledge of the mathematical construction of the solar system, and inferentially likewise to that of other systems; but it leaves without explanation a large number of singular facts. It explains the existing conditions of equilibrium of the heavenly bodies, but it tells us nothing of their genesis; or, at the best, in that particular it falls back on the simple fiat of G.o.d.

[Sidenote: Phenomena of the solar system.] The facts here referred to conduct us, however, to another and far higher point of view. Some of them, as enumerated by Laplace, are the following:--1. All the planets and their satellites move in ellipses of such small eccentricity that they are nearly circles; 2. The movements of the planets are in the same direction and nearly in the same plane; 3. The movements of the satellites are in the same direction as those of the planets; 4. The movements of rotation of these various bodies and of the sun are in the same direction as their orbitual motions, and in planes little different.

[Sidenote: The nebular hypothesis.] The nebular hypothesis requires us to admit that all the ponderable material now const.i.tuting the various bodies of the solar system once extended in a rarefied or nebulous and rotating condition, beyond the confines of the most distant planet. That postulate granted; the structure and present condition of the system may be mathematically deduced.

For, as the vast rotating spheroid lost its heat by radiation, it contracted, and its velocity of rotation was necessarily increased; and thus were left behind from its equatorial zone, by reason of the centrifugal force, rotating rings, the same result occurring periodically again and again. These rings must lie all in one plane.

They might break, collapsing into one rotating spheroid, a planet; or into many, asteroids; or maintain the ring-like form. From the larger of these secondary rotating spheroids other rings might be thrown off, as from the parent ma.s.s; these, in their turn breaking and becoming spheroids, const.i.tute satellites, whose movements correspond to those of their primaries.

We might, indeed, advance a step farther, and show how, by the radiation of heat from a motionless nebula, a movement of rotation in a determinate direction could be engendered, and that upon these principles, the existence of a nebulous matter admitted, and the present laws and forces of nature regarded as having been unchanged, the manner of origin of the solar system might be deduced, and all those singular facts previously alluded to explained; and not only so, but there is spontaneously suggested the cause of many minor peculiarities not yet mentioned.

[Sidenote: Facts accounted for by it.] For it follows from the nebular hypothesis that the large planets should rotate rapidly, and the small ones more slowly; that the outer planets and satellites should be larger than the inner ones. Of the satellites of Saturn, the largest is the outermost; of those of Jupiter, the largest is the outermost save one.

Of the planets themselves, Jupiter is the largest, and outermost save three. These cannot be coincidences, but must be due to law. The number of satellites of each planet, with the doubtful exception of Venus, might be foreseen, the presence of satellites and their number being determined by the centrifugal force of their primary. The hypothesis also points out the time of revolution of the planets in their orbits, and of the satellites in theirs; it furnishes a reason for the genesis and existence of Saturn's rings, which are indeed its remaining witnesses--their position and movements answering to its requirements.

It accounts for the physical state of the sun, and also for the physical state of the earth and moon as indicated by their geology. It is also not without furnis.h.i.+ng reasons for the existence of comets as integrant members of our system; for their singular physical state; for the eccentric, almost parabolic orbits of so many of them; for the fact that there are as many of them with a retrograde as with a direct motion; for their more frequent occurrence about the axis of the solar system than in its plane; and for their general ant.i.thetical relations to planets.

[Sidenote: Whether nebulae actually exist.] If these and very many other apparently disconnected facts follow as the mechanical necessities of the admission of a gravitating nebula--a very simple postulate--it becomes important to ascertain whether, by actual observation, the existence of such material forms may be demonstrated in any part of the universe. It was the actual telescopic observation of such objects that led Herschel to the nebular hypothesis. He concluded that there are two distinct kinds of nebulae, one consisting of cl.u.s.ters of stars so remote that they could not be discerned individually, but that these may be discerned by sufficient telescopic power; the other being of a hazy nature, and incapable of resolution. Nebulae do not occur at random in the heavens: the regions poorest in stars are richest in them; they are few in the plane of our sidereal system, but numerous about its poles, in that respect answering to the occurrence of comets in the solar system. The resolution of many of these hazy patches of light into stars by no means disproves the truly nebulous condition of many others.

Fortunately, however, other means than telescopic observation for the settlement of this question are available. In 1846, it was discovered by the author of this book that the spectrum of an ignited solid is continuous, that is, has neither dark nor bright fixed lines. Fraunhofer had previously made known that the spectrum of ignited gases is discontinuous. Here, then, is the means of determining whether the light emitted by a given nebula comes from an incandescent gas, or from a congeries of ignited solids, stars, or suns. If its spectrum be discontinuous, it is a true nebula or gas; if continuous, a congeries of stars.

In 1864, Mr. Huggins made this examination in the case of a nebula in the constellation Draco. It proved to be gaseous.

Subsequent observations have shown that of sixty nebulae examined, nineteen give discontinuous or gaseous spectra; the remainder continuous ones.

It may, therefore, be admitted that physical evidence has at length been obtained, demonstrating the existence of vast ma.s.ses of matter in a gaseous condition, and at a temperature of incandescence. The hypothesis of Laplace has thus a firm basis.

[Sidenote: Opposition to the nebular hypothesis.] Notwithstanding the great authority of the astronomers who introduced it, the nebular hypothesis has encountered much adverse criticism; not so much, however, from its obvious scientific defects, such as its inability to deal with the cases of Ura.n.u.s and Neptune, as from moral and extraneous considerations. There is a line in Aristophanes which points out precisely the difficulty:

Ho Zeus ouk on, all' ant' autou Dinos nuni basileuon.

A reluctance to acknowledge the presidency of law in the existing const.i.tution and movements of the solar system has been yielded only to be succeeded by a reluctance to acknowledge the presidency of law in its genesis. And yet whoever will reflect on the subject will be drawn to the conclusion that the principle involved was really settled by Newton in his "Principia"--that is to say, when it became geometrically certain that Kepler's laws originate in a mathematical necessity.

As matters now stand, the nebular hypothesis may be regarded as the first superficial, and therefore imperfect, glimpse of a series of the grandest problems soon to present themselves for solution--the mathematical distribution of matter and force in s.p.a.ce, and the variations of that distribution in time.

[Sidenote: The intellectual ruin of ecclesiasticism.] Such is the history of the dispute respecting the position of the earth in the universe. Not without reason, therefore, have I a.s.signed the pontificate of Nicolas V. as the true close of the intellectual dominion of the Church. From that time the sceptre had pa.s.sed into another hand. In all directions Nature was investigated, in all directions new methods of examination were yielding unexpected and beautiful results. On the ruins of its ivy-grown cathedrals, Ecclesiasticism, surprised and blinded by the breaking day, sat solemnly blinking at the light and life about it, absorbed in the recollection of the night that had pa.s.sed, dreaming of new phantoms and delusions in its wished-for return, and vindictively striking its talons at any derisive a.s.sailant who incautiously approached too near. I have not s.p.a.ce to describe the scientific activity displayed in all directions; to do it justice would demand volumes. Mathematics, physics, chemistry, anatomy, medicine, and all the many branches of human knowledge received an impulse. [Sidenote: Wonderful development of scientific activity.] Simultaneously with the great events I have been relating, every one of these branches was advancing. Vieta made the capital improvement of using letters as general symbols in algebra, and applied that science to geometry. Tycho, emulating Hipparchus of old, made a new catalogue of the stars; he determined that comets are beyond the moon, and that they cut the crystalline firmament of theology in all directions. Gilbert wrote his admirable book on the magnet; Gesner led the way to zoology, taking it up at the point to which the Saracens had continued Aristotle, by the publication of his work on the history of animals; Belon at the same time, 1540, was occupied with fishes and birds. Fallopius and Eustachius, Arantius and Varolius, were immortalizing themselves by their dissections: the former reminding us of the times of Ptolemy Philadelphus, when he navely confesses "the Duke of Tuscany was obliging enough to send living criminals to us, whom we killed and then dissected." Piccolomini laid the foundations of general anatomy by his description of cellular tissue. Coiter created pathological anatomy, Prosper Alpinus diagnosis, Plater the cla.s.sification of disease, and Ambrose Pare modern surgery. Such were the occupations and prospect of science at the close of the sixteenth century.

[Sidenote: The movement becomes still more vigorous.] Scarcely had the seventeenth opened when it became obvious that the movement, far from slackening, was gathering force. It was the age of Galileo. Descartes introduced the theory of an ether and vortices; but, hearing of the troubles that had befallen Galileo, was on the point of burning his papers. Several years later, he was restrained from publis.h.i.+ng his "Cosmos" "from a pious desire not to treat irreverently the decrees of the holy chair against the planetary movement of the earth." This was in 1633, when the report of the sentence of the Inquisition was made known.

He also developed Vieta's idea of the application of algebra to geometry, and brought into prominence the mechanical fact, destined to an important application in physical astronomy, that every curvilinear deflection is due to a controlling force. To him, among Europeans, also is to be attributed the true explanation of the rise of water in an exhausted s.p.a.ce--"the weight of the water counter-balances that of the air." Napier perfected his great and useful invention of logarithms.

Hydraulics was created by Castelli; hydrostatics by Torricelli, who also discovered barometric variations: both were pupils of Galileo. Fabricius ab Aquapendente discovered the valves in the veins; Servetus almost detected the course of the circulation. Harvey completed what Servetus had left unfinished, and described the entire course of the blood; Asellius discovered the lacteals; Van Helmont introduced the theory of vitality into medicine, and made the practice or art thereof consist in regulating by diet the Archeus, whose seat he affirmed to be in the stomach. In strong contrast with this phantasy, Sanctorio laid the foundation of modern physiology by introducing the balance into its inquiries. Pascal, by a decisive experiment, established the doctrines of the weight and pressure of the air, and published some of the most philosophical treatises of the age: "his Provincial Letters did more than any thing to ruin the name of the Jesuits." The contagion spread to the lawyers: in 1672 appeared Puffendorf's work on the "Law of Nature and Nations." The phlogistic theory, introduced by Beccher and perfected by Stahl, created chemistry, in contradistinction to the Arabian alchemy. Otto Guericke invented the air-pump, Boyle improved it. Hooke, among many other discoveries, determined the essential conditions of combustion. Far above all contemporaries in mathematical learning and experimental skill, Newton was already turning his attention to the "reflexions, refractions, inflexions and colours of light," and introducing the idea of attractions into physics. Ray led the way to comparative anatomy in his synopsis of quadrupeds; Swammerdam improved the art of dissection, applying it to the general history of insects; Lister published his synopsis of sh.e.l.ls; Tournefort and Malpighi devoted themselves to botany; Grew discovered the s.e.xes of plants; Brown the quinary arrangement of flowers. Geology began to break loose from the trammels of theology, and Burnet's Sacred theory of the Earth could not maintain its ground against more critical investigations. The Arabian doctrine of the movement of the crust of the earth began to find supporters. Lister ascertained the continuity of strata over great distances; Woodward improved mineralogy; the great mathematician, Leibnitz, the rival of Newton, propounded the doctrine of the gradual cooling of the globe, the descent of its strata by fracture, the deposit of sedimentary rocks, and their induration. Among physicians, Willis devoted himself to the study of the brain, traced the course of the nerves and cla.s.sified them, and introduced the doctrine of the localization of functions in the brain. Malpighi and Lewenhoeck applied the microscope as an aid to anatomy; the latter discovered spermatozoa.

Graaf studied the function of the generative organs; Borelli attempted the application of mathematics to muscular movement; Duverney wrote on the sense of hearing, Mayow on respiration; Ruysch perfected the art of injection, and improved minute anatomy.

But it is in vain to go on. The remainder of these pages would be consumed in an attempt to record the names of the cultivators of science, every year increasing in number, and to do justice to their works. From the darkness that had for so many ages enveloped it, the human mind at last emerged into light. The intellectual motes were dancing in the sunbeam, and making it visible in every direction.

[Sidenote: Inst.i.tution of scientific societies.] Despairing thus to do justice to individual philosophers and individual discoveries, there is, however, one most important event to which I must prominently allude. It is the foundation of learned societies. Imitating the examples of the Academia Secretorum Naturae, inst.i.tuted at Naples, 1560, by Baptista Porta, and of the Lyncean Academy, founded 1603 by Prince Frederic Cesi at Rome for the promotion of natural philosophy, the Accademia del Cimento was established at Florence, 1637; the Royal Society of London, 1645; and the Royal Academy of Sciences in Paris, 1666.

[Sidenote: Review of anthropocentric philosophy.] Arrived at the close of the description of this first great victory of scientific truth over authority and tradition, it is well for us to pause and look back on the progress of man from the erroneous inferences of his social infancy to the true conclusions of his maturity--from anthropocentric ideas, which in all nations and parts of the world have ever been the same, to the discovery of his true position and insignificance in the universe.

[Sidenote: The sky, apparent nature of.] We are placed in a world surrounded with illusions. The daily events of our life and the objects before us tend equally to deceive us. If we cast our eyes on the earth, it seems to be made only to minister to our pleasures or our wants. If we direct our attention to the sky, that blue and crystalline dome, the edges of which rest on the flat land or the sea--a glacial vault, which Empedocles thought was frozen air, and the fathers of the Church the lowest of the seven concentric strata of heavens--we find a thousand reasons for believing that whatever it covers was intended by some Good Being for our use. Of the various living things placed with us beneath it, all are of an inferior grade when compared with ourselves, and all seem intended for us. The conclusions at which we thus arrive are strengthened by a principle of vanity implanted in our hearts, unceasingly suggesting to us that this pleasant abode must have been prepared for our reception, and furnished and ornamented expressly for our use.

[Sidenote: Anthropocentric ideas of G.o.d.] But reflexion teaches us that we came not hither of ourselves, and that doubtless the same Good Being who prepared this delightful abode brought us as tenants into it. From the fact of our own existence, we are insensibly and inevitably led to infer the existence of G.o.d; from the favourable circ.u.mstances in which our lot is cast, we gather evidences of His goodness; and in the energy which natural phenomena often display, we see the tokens of His power.

What other explanation can we give of tempests in the sea or lightning in the heavens? Moreover, it is only during a part of our time--our waking hours--that we are brought into relation with these material things; for the rest, when we are asleep, a state in which we spend more than a third part of our life, we are introduced to other scenery, other beings, another world. [Sidenote: Of the world and heaven.] From these we gather that there are agents of an intangible and more ethereal mould, perhaps of the nature of Him who brought us here, perhaps His subordinates and messengers. Whence do they issue and whither do they go? Is there not beyond the sky above us a region to which our imperfect vision cannot penetrate, but which may be accessible to them from the peaks of elevated mountains, or to be reached only with wings? And thus we picture to ourselves a heaven shut off from earth, with all its sins and cares, by the untroubled and impenetrable sky--a place of light and repose, its pavement illuminated by the sun and countless other s.h.i.+ning bodies--a place of peace, but also a place of power.

[Sidenote: Of evil beings and h.e.l.l.] Still more, a thousand facts of our life teach us that we are exposed to influences of an evil nature as well as to those that are good. How often, in our dreams, does it happen that we are terror-stricken by the approach of hideous forms, faces of fearful appearance, from which we vainly struggle to escape. Is it not natural for us to attribute the evil we see in the world to these as the good to those? and, since we can not conceive of the existence of beings without a.s.signing them a place, where shall we find for these malignant spirits a habitation? Is it not in the dark region beneath the ground, far away from the realms of light--a region from which, through the volcano, smoke and burning sulphur are cast into this upper world--a place of everlasting fire and darkness, whose portals are in caves and solitudes of unutterable gloom?

[Sidenote: Of man, the supernatural.] Placed thus on the boundary between such opposing powers, man is the sport of circ.u.mstances, sustained by beings who seek his happiness, and tempted by those who desire his destruction. Is it at all surprising that, guided by such obvious thoughts and simple reasonings, he becomes superst.i.tious? that he sees in every shadow a spirit, and peoples every solitary place with invisibles? that he casts a longing look to the good beings who can protect him, seeking to invoke their aid by entreaties, and to propitiate their help by free-will sacrifices of things that are pleasant and valuable? Open to such influences himself, why should he not believe in the efficacy of prayer? His conscious superiority lends force to his suspicion that he is a worthy object for the opposing powers to contend for, a conclusion verified by the inward strifes he feels, as well as by the trials of life to which he is exposed.

[Sidenote: His immortality and future life.] But dreams at night, and sometimes visions by day, serve to enforce the conclusion that life is not limited to our transitory continuance here, but endures hereafter.

How often at night do we see the well-known forms of those who have been dead a long time appearing before us with surprising vividness, and hear their almost forgotten voices? These are admonitions full of the most solemn suggestions, profoundly indicating to us that the dead still continue to exist, and that what has happened to them must also happen to us, and we too are destined for immortality. Perhaps involuntarily we a.s.sociate these conclusions with others, expecting that in a future life good men will enjoy the society of good beings like themselves, the evil being dismissed to the realms of darkness and despair. And, as human experience teaches us that a final allotment can only be made by some superior power, we expect that He who was our Creator shall also be our Judge; that there is an appointed time and a bar at which the final destination of all who have lived shall be ascertained, and eternal justice measure out its punishments and rewards.

[Sidenote: Inducements to morality.] From these considerations there arises an inducement for us to lead a virtuous life, abstaining from wickedness and wrong; to set apart a body of men who may mediate for us, and teach us by precept and example the course it is best for us to pursue; to consecrate places, such as groves or temples, as the more immediate habitations of the Deity to which we may resort.

Such are the leading doctrines of Natural Theology of primitive man both in the old and new continent. They arise from the operations of the human mind considering the fitness of things.

Just as we have in Comparative Anatomy the structure of different animals examined, and their ident.i.ties and differences set forth, thereby establis.h.i.+ng their true relations; just as we have in Comparative Physiology the functions of one organic being compared with those of another, to the end that we may therefrom deduce their proper connexions, so, from the mythologies of various races of men, a Comparative Theology may be constructed. [Sidenote: Course of Comparative Theology.] Through such a science alone can correct conclusions be arrived at respecting this, the most important of the intellectual operations of man--the definite process of his religious opinions. But it must be borne in mind that Comparative Theology ill.u.s.trates the result or effect of the phase of life, and is not its cause.

[Sidenote: Corrections of anthropocentric ideas.] As man advances in knowledge he discovers that of his primitive conclusions some are doubtless erroneous, and many require better evidence to establish their truth incontestably. A more prolonged and attentive examination gives him reason, in some of the most important particulars, to change his mind. He finds that the earth on which he lives is not a floor covered over with a starry dome, as he once supposed, but a globe self-balanced in s.p.a.ce. The crystalline vault, or sky, is recognized to be an optical deception. It rests upon the earth nowhere, and is no boundary at all; there is no kingdom of happiness above it, but a limitless s.p.a.ce, adorned with planets and suns. Instead of a realm of darkness and woe in the depths on the other side of the earth, men like ourselves are found there, pursuing, in Australia and New Zealand, the innocent pleasures and encountering the ordinary labours of life. By the aid of such lights as knowledge gradually supplies, he comes at last to discover that this, our terrestrial habitation, instead of being a chosen, a sacred spot, is only one of similar myriads, more numerous than the sands of the sea, and prodigally scattered through s.p.a.ce.

[Sidenote: Consequence of discovering the form of the earth.] Never, perhaps, was a more important truth discovered. All the visible evidence was in direct opposition to it. [Sidenote: Detection of its insignificance.] The earth, which had hitherto seemed to be the very emblem of immobility, was demonstrated to be carried with a double motion, with prodigious velocity, through the heavens; the rising and setting of the stars were proved to be an illusion; and, as respects the size of the globe, it was shown to be altogether insignificant when compared with mult.i.tudes of other neighbouring ones--insignificant doubly by reason of its actual dimensions, and by the countless numbers of others like it in form, and doubtless, like it, the abodes of many orders of life.

And so it turns out that our earth is a globe of about twenty-five thousand miles in circ.u.mference. The voyager who circ.u.mnavigates it spends no inconsiderable portion of his life in accomplis.h.i.+ng his task.

It moves round the sun in a year, but at so great a distance from that luminary that, if seen from him, it would look like a little spark traversing the sky. It is thus recognized as one of the members of the solar system. [Sidenote: Other solar bodies.] Other similar bodies, some of which are of larger, some of smaller dimensions, perform similar revolutions round the sun in appropriate periods of time.

[Sidenote: Magnitude of the universe.] If the magnitude of the earth be too great for us to attach to it any definite conception, what shall we say of the compa.s.s of the solar system? There is a defect in the human intellect which incapacitates us for comprehending distances and periods that are either too colossal or too minute. We gain no clearer insight into the matter when we are told that a comet which does not pa.s.s beyond the bounds of the system, may perhaps be absent on its journey for more than a thousand years. Distances and periods such as these are beyond our grasp. They prove to us how far human reason excels imagination, the one measuring and comparing things of which the other can form no conception, but in the attempt is utterly bewildered and lost.

[Sidenote: The infinity of worlds.] But as there are other globes like our earth, so too there are other worlds like our solar system. There are self-luminous suns exceeding in number all computation. The dimensions of this earth pa.s.s into nothingness in comparison with the dimensions of the solar system, and that system, in its turn, is only an invisible point if placed in relation with the countless hosts of other systems which form, with it, cl.u.s.ters of stars. Our solar system, far from being alone in the universe, is only one of an extensive brotherhood, bound by common laws and subject to like influences. Even on the very verge of creation, where imagination might lay the beginning of the realms of chaos, we see unbounded proofs of order, a regularity in the arrangement of inanimate things, suggesting to us that there are other intellectual creatures like us, the tenants of those islands in the abysses of s.p.a.ce.

Though it may take a beam of light a million of years to bring to our view those distant worlds, the end is not yet. Far away in the depths of s.p.a.ce we catch the faint gleams of other groups of stars like our own.

The finger of a man can hide them in their remoteness. Their vast distances from one another have dwindled into nothing. They and their movements have lost all individuality; the innumerable suns of which they are composed blend all their collected light into one pale milky glow.

[Sidenote: Insignificance of man.] Thus extending our view from the earth to the solar system, from the solar system to the expanse of the group of stars to which we belong, we behold a series of gigantic nebular creations rising up one after another, and forming greater and greater colonies of worlds. No numbers can express them, for they make the firmament a haze of stars. Uniformity, even though it be the uniformity of magnificence, tires at last, and we abandon the survey, for our eyes can only behold a boundless prospect, and conscience tells us our own unspeakable insignificance.

[Sidenote: Triumph of scientific truth.] But what has become of the time-honoured doctrine of the human destiny of the universe? that doctrine for the sake of which the controversy I have described in this chapter was raised. It has disappeared. In vain was Bruno burnt and Galileo imprisoned; the truth forced its way, in spite of all opposition, at last. The end of the conflict was a total rejection of authority and tradition, and the adoption of scientific truth.

CHAPTER IX.

THE EUROPEAN AGE OF REASON--(_Continued_).

HISTORY OF THE EARTH.--HER SUCCESSIVE CHANGES IN THE COURSE OF TIME.

_Oriental and Occidental Doctrines respecting the Earth in Time.--Gradual Weakening of the latter by astronomical Facts, and the Rise of Scientific Geology._

_Impersonal Manner in which the Problem was eventually solved, chiefly through Facts connected with Heat._

_Proofs of limitless Duration from inorganic Facts.--Igneous and Aqueous Rocks._

_Proofs of the same from organic Facts.--Successive Creations and Extinctions of living Forms, and their contemporaneous Distribution._