I have now to present the discussions that arose respecting the third great philosophical problem the nature of the world.

An uncritical observation of the aspect of Nature persuades us that the earth is an extended level surface which sustains the dome of the sky, a firmament dividing the waters above from the waters beneath; that the heavenly bodies the sun, the moon, the stars pursue their way, moving from east to west, their insignificant size and motion round the motionless earth proclaiming their inferiority. Of the various organic forms surrounding man none rival him in dignity, and hence he seems justified in concluding that every thing has been created for his use the sun for the purpose of giving him light by day, the moon and stars by night.

Comparative theology shows us that this is the conception of Nature universally adopted in the early phase of intellectual life. It is the belief of all nations in all parts of the world in the beginning of their civilization: geocentric, for it makes the earth the centre of the universe; anthropocentric, for it makes man the central object of the earth. And not only is this the conclusion spontaneously come to from inconsiderate glimpses of the world, it is also the philosophical basis of various religious revelations, vouchsafed to man from time to time. These revelations, moreover, declare to him that above the crystalline dome of the sky is a region of eternal light and happiness heaven the abode of God and the angelic hosts, perhaps also his own abode after death; and beneath the earth a region of eternal darkness and misery, the habitation of those that are evil. In the visible world is thus seen a picture of the invisible.

On the basis of this view of the structure of the world great religious systems have been founded, and hence powerful material interests have been engaged in its support. These have resisted, sometimes by resorting to bloodshed, attempts that have been made to correct its incontestable errors a resistance grounded on the suspicion that the localization of heaven and hell and the supreme value of man in the universe might be affected.

That such attempts would be made was inevitable. As soon as men began to reason on the subject at all, they could not fail to discredit the assertion that the earth is an indefinite plane. No one can doubt that the sun we see to-day is the self-same sun that we saw yesterday. His reappearance each morning irresistibly suggests that he has passed on the underside of the earth. But this is incompatible with the reign of night in those regions. It presents more or less distinctly the idea of the globular form of the earth.

The earth cannot extend indefinitely downward; for the sun cannot go through it, nor through any crevice or passage in it, Since he rises and sets in different positions at different seasons of the year. The stars also move under it in countless courses. There must, therefore, be a clear way beneath.

To reconcile revelation with these innovating facts, schemes, such as that of Cosmas Indicopleustes in his Christian Topography, were doubtless often adopted. To this in particular we have had occasion on a former page to refer. It asserted that in the northern parts of the flat earth there is an immense mountain, behind which the sun passes, and thus produces night.

At a very remote historical period the mechanism of eclipses had been discovered. Those of the moon demonstrated that the shadow of the earth is always circular. The form of the earth must therefore be globular. A body which in all positions casts a circular shadow must itself be spherical. Other considerations, with which every one is now familiar, could not fail to establish that such is her figure.

But the determination of the shape of the earth by no means deposed her from her position of superiority. Apparently vastly larger than all other things, it was fitting that she should be considered not merely as the centre of the world, but, in truth, as the world. All other objects in their aggregate seemed utterly unimportant in comparison with her.

Though the consequences flowing from an admission of the globular figure of the earth affected very profoundly existing theological ideas, they were of much less moment than those depending on a determination of her size. It needed but an elementary knowledge of geometry to perceive that correct ideas on this point could be readily obtained by measuring a degree on her surface. Probably there were early attempts to accomplish this object, the results of which have been lost. But Eratosthenes executed one between Syene and Alexandria, in Egypt, Syene being supposed to be exactly under the tropic of Cancer. The two places are, however, not on the same meridian, and the distance between them was estimated, not measured. Two centuries later, Posidonius made another attempt between Alexandria and Rhodes; the bright star Canopus just grazed the horizon at the latter place, at Alexandria it rose 7 1/2 degrees. In this instance, also, since the direction lay across the sea, the distance was estimated, not measured. Finally, as we have already related, the Khalif Al-Mamun made two sets of measures, one on the shore of the Red Sea, the other near Cufa, in Mesopotamia. The general result of these various observations gave for the earth’s diameter between seven and eight thousand miles.

This approximate determination of the size of the earth tended to depose her from her dominating position, and gave rise to very serious theological results. In this the ancient investigations of Aristarchus of Samos, one of the Alexandrian school, 280 B.C., powerfully aided. In his treatise on the magnitudes and distances of the sun and moon, he explains the ingenious though imperfect method to which he had resorted for the solution of that problem. Many ages previously a speculation had been brought from India to Europe by Pythagoras. It presented the sun as the centre of the system. Around him the planets revolved in circular orbits, their order of position being Mercury, Venus, Earth, Mars, Jupiter, Saturn, each of them being supposed to rotate on its axis as it revolved round the sun. According to Cicero, Nicetas suggested that, if it were admitted that the earth revolves on her axis, the difficulty presented by the inconceivable velocity of the heavens would be avoided.

There is reason to believe that the works of Aristarchus, in the Alexandrian Library, were burnt at the time of the fire of Cæsar. The only treatise of his that has come down to us is that above mentioned, on the size and distance of the sun and moon.

Aristarchus adopted the Pythagorean system as representing the actual facts. This was the result of a recognition of the sun’s amazing distance, and therefore of his enormous size. The heliocentric system, thus regarding the sun as the central orb, degraded the earth to a very subordinate rank, making her only one of a company of six revolving bodies.

But this is not the only contribution conferred on astronomy by Aristarchus, for, considering that the movement of the earth does not sensibly affect the apparent position of the stars, he inferred that they are incomparably more distant from us than the sun. He, therefore, of all the ancients, as Laplace remarks, had the most correct ideas of the grandeur of the universe. He saw that the earth is of absolutely insignificant size, when compared with the stellar distances. He saw, too, that there is nothing above us but space and stars.

But the views of Aristarchus, as respects the emplacement of the planetary bodies, were not accepted by antiquity; the system proposed by Ptolemy, and incorporated in his “Syntaxis,” was universally preferred. The physical philosophy of those times was very imperfect one of Ptolemy’s objections to the Pythagorean system being that, if the earth were in motion, it would leave the air and other light bodies behind it. He therefore placed the earth in the central position, and in succession revolved round her the Moon, Mercury, Venus, the Sun, Mars, Jupiter, Saturn; beyond the orbit of Saturn came the firmament of the fixed stars. As to the solid crystalline spheres, one moving from east to west, the other from north to south, these were a fancy of Eudoxus, to which Ptolemy does not allude.

The Ptolemaic system is, therefore, essentially a geocentric system. It left the earth in her position of superiority, and hence gave no cause of umbrage to religious opinions, Christian or Mohammedan. The immense reputation of its author, the signal ability of his great work on the mechanism of the heavens, sustained it for almost fourteen hundred years that is, from the second to the sixteenth century.

In Christendom, the greater part of this long period was consumed in disputes respecting the nature of God, and in struggles for ecclesiastical power. The authority of the Fathers, and the prevailing belief that the Scriptures contain the sum, of all knowledge, discouraged any investigation of Nature. If by chance a passing interest was taken in some astronomical question, it was at once settled by a reference to such authorities as the writings of Augustine or Lactantius, not by an appeal to the phenomena of the heavens. So great was the preference given to sacred over profane learning that Christianity had been in existence fifteen hundred years, and had not produced a single astronomer.

The Mohammedan nations did much better. Their cultivation of science dates from the capture of Alexandria, A.D. 638. This was only six years after the death of the Prophet. In less than two centuries they had not only become acquainted with, but correctly appreciated, the Greek scientific writers. As we have already mentioned, by his treaty with Michael iii., the khalif Al-Mamun had obtained a copy of the “Syntaxis” of Ptolemy. He had it forthwith translated into Arabic. It became at once the great authority of Saracen astronomy. From this basis the Saracens had advanced to the solution of some of the most important scientific problems. They had ascertained the dimensions of the earth; they had registered or catalogued all the stars visible in their heavens, giving to those of the larger magnitudes the names they still bear on our maps and globes; they determined the true length of the year, discovered astronomical refraction, invented the pendulum-clock, improved the photometry of the stars, ascertained the curvilinear path of a ray of light through the air, explained the phenomena of the horizontal sun and moon, and why we see those bodies before they have risen and after they have set; measured the height of the atmosphere, determining it to be fifty-eight miles; given the true theory of the twilight, and of the twinkling of the stars. They had built the first observatory in Europe. So accurate were they in their observations, that the ablest modern mathematicians have made use of their results. Thus Laplace, in his “Système du Monde,” adduces the observations of Al-Batagni as affording incontestable proof of the diminution of the eccentricity of the earth’s orbit. He uses those of Ibn-Junis in his discussion of the obliquity of the ecliptic, and also in the case of the problems of the greater inequalities of Jupiter and Saturn.

These represent but a part, and indeed but a small part, of the services rendered by the Arabian astronomers, in the solution of the problem of the nature of the world. Meanwhile, such was the benighted condition of Christendom, such its deplorable ignorance, that it cared nothing about the matter. Its attention was engrossed by image-worship, transubstantiation, the merits of the saints, miracles, shrine-cures.

This indifference continued until the close of the fifteenth century. Even then there was no scientific inducement. The inciting motives were altogether of a different kind. They originated in commercial rivalries, and the question of the shape of the earth was finally settled by three sailors, Columbus, De Gama, and, above all, by Ferdinand Magellan.

The trade of Eastern Asia has always been a source of immense wealth to the Western nations who in succession have obtained it. In the middle ages it had centred in Upper Italy. It was conducted along two lines a northern, by way of the Black and Caspian Seas, and camel-caravans beyond the headquarters of this were at Genoa; and a southern, through the Syrian and Egyptian ports, and by the Arabian Sea, the headquarters of this being at Venice. The merchants engaged in the latter traffic had also made great gains in the transport service of the Crusade-wars.

The Venetians had managed to maintain amicable relations with the Mohammedan powers of Syria and Egypt; they were permitted to have consulates at Alexandria and Damascus, and, notwithstanding the military commotions of which those countries had been the scene, the trade was still maintained in a comparatively flourishing condition. But the northern or Genoese line had been completely broken up by the irruptions of the Tartars and the Turks, and the military and political disturbances of the countries through which it passed. The Eastern trade of Genoa was not merely in a precarious condition it was on the brink of destruction.

The circular visible horizon and its dip at sea, the gradual appearance and disappearance of ships in the offing, cannot fail to incline intelligent sailors to a belief in the globular figure of the earth. The writings of the Mohammedan astronomers and philosophers had given currency to that doctrine throughout Western Europe, but, as might be expected, it was received with disfavor by theologians. When Genoa was thus on the very brink of ruin, it occurred to some of her mariners that, if this view were correct, her affairs might be re-established. A ship sailing through the straits of Gibraltar westward, across the Atlantic, would not fail to reach the East Indies. There were apparently other great advantages. Heavy cargoes might be transported without tedious and expensive land-carriage, and without breaking bulk.

Among the Genoese sailors who entertained these views was Christopher Columbus.

He tells us that his attention was drawn to this subject by the writings of Averroes, but among his friends he numbered Toscanelli, a Florentine, who had turned his attention to astronomy, and had become a strong advocate of the globular form. In Genoa itself Columbus met with but little encouragement. He then spent many years in trying to interest different princes in his proposed attempt. Its irreligious tendency was pointed out by the Spanish ecclesiastics, and condemned by the Council of Salamanca; its orthodoxy was confuted from the Pentateuch, the Psalms, the Prophecies, the Gospels, the Epistles, and the writings of the Fathers St. Chrysostom, St. Augustine, St. Jerome, St. Gregory, St. Basil, St Ambrose.

At length, however, encouraged by the Spanish Queen Isabella, and substantially aided by a wealthy seafaring family, the Pinzóns of Palos, some of whom joined him personally, he sailed on August 3, 1492, with three small ships, from Palos, carrying with him a letter from King Ferdinand to the Grand-Khan of Tartary, and also a chart, or map, constructed on the basis of that of Toscanelli. A little before midnight, October 11, 1492, he saw from the forecastle of his ship a moving light at a distance. Two hours subsequently a signal-gun from another of the ships announced that they had descried land. At sunrise Columbus landed in the New World.

On his return to Europe it was universally supposed that he had reached the eastern parts of Asia, and that therefore his voyage bad been theoretically successful. Columbus himself died in that belief. But numerous voyages which were soon undertaken made known the general contour of the American coast-line, and the discovery of the Great South Sea by Balboa revealed at length the true facts of the case, and the mistake into which both Toscanelli and Columbus had fallen, that in a voyage to the West the distance from Europe to Asia could not exceed the distance passed over in a voyage from Italy to the Gulf of Guinea a voyage that Columbus had repeatedly made.

In his first voyage, at nightfall on September 13, 1492, being then two and a half degrees east of Corvo, one of the Azores, Columbus observed that the compass needles of the ships no longer pointed a little to the east of north, but were varying to the west. The deviation became more and more marked as the expedition advanced. He was not the first to detect the fact of variation, but he was incontestably the first to discover the line of no variation. On the return-voyage the reverse was observed; the variation westward diminished until the meridian in question was reached, when the needles again pointed due north. Thence, as the coast of Europe was approached, the variation was to the east. Columbus, therefore, came to the conclusion that the line of no variation was a fixed geographical line, or boundary, between the Eastern and Western Hemispheres. In the bull of May, 1493, Pope Alexander VI. accordingly adopted this line as the perpetual boundary between the possessions of Spain and Portugal, in his settlement of the disputes of those nations. Subsequently, however, it was discovered that the line was moving eastward. It coincided with the meridian of London in 1662.

By the papal bull the Portuguese possessions were limited to the east of the line of no variation. Information derived from certain Egyptian Jews had reached that government, that it was possible to sail round the continent of Africa, there being at its extreme south a cape which could be easily doubled. An expedition of three ships under Vasco de Gama set sail, July 9, 1497; it doubled the cape on November 20th, and reached Calicut, on the coast of India, May 19, 1498. Under the bull, this voyage to the East gave to the Portuguese the right to the India trade.

Until the cape was doubled, the course of De Gama’s ships was in a general manner southward. Very soon, it was noticed that the elevation of the pole-star above the horizon was diminishing, and, soon after the equator was reached, that star had ceased to be visible. Meantime other stars, some of them forming magnificent constellations, had come into view the stars of the Southern Hemisphere. All this was in conformity to theoretical expectations founded on the admission of the globular form of the earth.

The political consequences that at once ensued placed the Papal Government in a position of great embarrassment. Its traditions and policy forbade it to admit any other than the flat figure of the earth, as revealed in the Scriptures. Concealment of the facts was impossible, sophistry was unavailing. Commercial prosperity now left Venice as well as Genoa. The front of Europe was changed. Maritime power had departed from the Mediterranean countries, and passed to those upon the Atlantic coast.

But the Spanish Government did not submit to the advantage thus gained by its commercial rival without an effort. It listened to the representations of one Ferdinand Magellan, that India and the Spice Islands could be reached by sailing to the west, if only a strait or passage through what had now been recognized as “the American Continent” could be discovered; and, if this should be accomplished, Spain, under the papal bull, would have as good a right to the India trade as Portugal. Under the command of Magellan, an expedition of five ships, carrying two hundred and thirty-seven men, was dispatched from Seville, August 10, 1519.

Magellan at once struck boldly for the South American coast, hoping to find some cleft or passage through the continent by which he might reach the great South Sea. For seventy days he was becalmed on the line; his sailors were appalled by the apprehension that they had drifted into a region where the winds never blew, and that it was impossible for them to escape. Calms, tempests, mutiny, desertion, could not shake his resolution. After more than a year he discovered the strait which now bears his name, and, as Pigafetti, an Italian, who was with him, relates, he shed fears of joy when he found that it had pleased God at length to bring him where he might grapple with the unknown dangers of the South Sea, “the Great and Pacific Ocean.”

Driven by famine to eat scraps of skin and leather with which his rigging was here and there bound, to drink water that had gone putrid, his crew dying of hunger and scurvy, this man, firm in his belief of the globular figure of the earth, steered steadily to the northwest, and for nearly four months never saw inhabited land. He estimated that he had sailed over the Pacific not less than twelve thousand miles. He crossed the equator, saw once more the pole-star, and at length made land the Ladrones. Here he met with adventurers from Sumatra. Among these islands he was killed, either by the savages or by his own men. His lieutenant, Sebastian d’Elcano, now took command of the ship, directing her course for the Cape of Good Hope, and encountering frightful hardships. He doubled the cape at last, and then for the fourth time crossed the equator. On September 7, 1522, after a voyage of more than three years, he brought his ship, the San Vittoria, to anchor in the port of St. Lucar, near Seville. She had accomplished the greatest achievement in the history of the human race. She had circumnavigated the earth.

The San Vittoria, sailing westward, had come back to her starting-point. Henceforth the theological doctrine of the flatness of the earth was irretrievably overthrown.

Five years after the completion of the voyage of Magellan, was made the first attempt in Christendom to ascertain the size of the earth. This was by Fernel, a French physician, who, having observed the height of the pole at Paris, went thence northward until he came to a place where the height of the pole was exactly one degree more than at that city. He measured the distance between the two stations by the number of revolutions of one of the wheels of his carriage, to which a proper indicator bad been attached, and came to the conclusion that the earth’s circumference is about twenty-four thousand four hundred and eighty Italian miles.

Measures executed more and more carefully were made in many countries: by Snell in Holland; by Norwood between London and York in England; by Picard, under the auspices of the French Academy of Sciences, in France. Picard’s plan was to connect two points by a series of triangles, and, thus ascertaining the length of the arc of a meridian intercepted between them, to compare it with the difference of latitudes found from celestial observations. The stations were Malvoisine in the vicinity of Paris, and Sourdon near Amiens. The difference of latitudes was determined by observing the zenith-distances, of delta Cassiopeia. There are two points of interest connected with Picard’s operation: it was the first in which instruments furnished with telescopes were employed; and its result, as we shall shortly see, was to Newton the first confirmation of the theory of universal gravitation.

At this time it had become clear from mechanical considerations, more especially such as had been deduced by Newton, that, since the earth is a rotating body, her form cannot be that of a perfect sphere, but must be that of a spheroid, oblate or flattened at the poles. It would follow, from this, that the length of a degree must be greater near the poles than at the equator.

The French Academy resolved to extend Picard’s operation, by prolonging the measures in each direction, and making the result the basis of a more accurate map of France. Delays, however, took place, and it was not until 1718 that the measures, from Dunkirk on the north to the southern extremity of France, were completed. A discussion arose as to the interpretation of these measures, some affirming that they indicated a prolate, others an oblate spheroid; the former figure may be popularly represented by a lemon, the latter by an orange. To settle this, the French Government, aided by the Academy, sent out two expeditions to measure degrees of the meridian one under the equator, the other as far north as possible; the former went to Peru, the latter to Swedish Lapland. Very great difficulties were encountered by both parties. The Lapland commission, however, completed its observations long before the Peruvian, which consumed not less than nine years. The results of the measures thus obtained confirmed the theoretical expectation of the oblate form. Since that time many extensive and exact repetitions of the observation have been made, among which may be mentioned those of the English in England and in India, and particularly that of the French on the occasion of the introduction of the metric system of weights and measures. It was begun by Delambre and Mechain, from Dunkirk to Barcelona, and thence extended, by Biot and Arago, to the island of Formentera near Minorea. Its length was nearly twelve and a half degrees.

Besides this method of direct measurement, the figure of the earth may be determined from the observed number of oscillations made by a pendulum of invariable length in different latitudes. These, though they confirm the foregoing results, give a somewhat greater ellipticity to the earth than that found by the measurement of degrees. Pendulums vibrate more slowly the nearer they are to the equator. It follows, therefore, that they are there farther from the centre of the earth.

From the most reliable measures that have been made, the dimensions of the earth may be thus stated:

Greater or equatorial diameter..............7,925 miles.
Less or polar diameter......................7,899 "
Difference or polar compression.............   26 "

Such was the result of the discussion respecting the figure and size of the earth. While it was yet undetermined, another controversy arose, fraught with even more serious consequences. This was the conflict respecting the earth’s position with regard to the sun and the planetary bodies.

Copernicus, a Prussian, about the year 1507, had completed a book “On the Revolutions of the Heavenly Bodies.” He had journeyed to Italy in his youth, had devoted his attention to astronomy, and had taught mathematics at Rome. From a profound study of the Ptolemaic and Pythagorean systems, he had come to a conclusion in favor of the latter, the object of his book being to sustain it. Aware that his doctrines were totally opposed to revealed truth, and foreseeing that they would bring upon him the punishments of the Church, he expressed himself in a cautious and apologetic manner, saying that he had only taken the liberty of trying whether, on the supposition of the earth’s motion, it was possible to find better explanations than the ancient ones of the revolutions of the celestial orbs; that in doing this he had only taken the privilege that had been allowed to others, of feigning what hypothesis they chose. The preface was addressed to Pope Paul iii.

Full of misgivings as to what might be the result, he refrained from publishing his book for thirty-six years, thinking that “perhaps it might be better to follow the examples of the Pythagoreans and others, who delivered their doctrine only by tradition and to friends.” At the entreaty of Cardinal Schomberg he at length published it in 1543. A copy of it was brought to him on his death-bed. Its fate was such as he had anticipated. The Inquisition condemned it as heretical. In their decree, prohibiting it, the Congregation of the Index denounced his system as “that false Pythagorean doctrine utterly contrary to the Holy Scriptures.”

Astronomers justly affirm that the book of Copernicus, “De Revolutionibus,” changed the face of their science. It incontestably established the heliocentric theory. It showed that the distance of the fixed stars is infinitely great, and that the earth is a mere point in the heavens. Anticipating Newton, Copernicus imputed gravity to the sun, the moon, and heavenly bodies, but he was led astray by assuming that the celestial motions must be circular. Observations on the orbit of Mars, and his different diameters at different times, had led Copernicus to his theory.

In thus denouncing the Copernican system as being in contradiction to revelation, the ecclesiastical authorities were doubtless deeply moved by inferential considerations. To dethrone the earth from her central dominating position, to give her many equals and not a few superiors, seemed to diminish her claims upon the Divine regard. If each of the countless myriads of stars was a sun, surrounded by revolving globes, peopled with responsible beings like ourselves, if we had fallen so easily and had been redeemed at so stupendous a price as the death of the Son of God, how was it with them? Of them were there none who had fallen or might fall like us? Where, then, for them could a Savior be found?

During the year 1608 one Lippershey, a Hollander, discovered that, by looking through two glass lenses, combined in a certain manner together, distant objects were magnified and rendered very plain. He had invented the telescope. In the following year Galileo, a Florentine, greatly distinguished by his mathematical and scientific writings, hearing of the circumstance, but without knowing the particulars of the construction, invented a form of the instrument for himself. Improving it gradually, he succeeded in making one that could magnify thirty times. Examining the moon, he found that she had valleys like those of the earth, and mountains casting shadows. It had been said in the old times that in the Pleiades there were formerly seven stars, but a legend related that one of them had mysteriously disappeared. On turning his telescope toward them, Galileo found that he could easily count not fewer than forty. In whatever direction he looked, he discovered stars that were totally invisible to the naked eye.

On the night of January 7, 1610, he perceived three small stars in a straight line, adjacent to the planet Jupiter, and, a few evenings later, a fourth. He found that these were revolving in orbits round the body of the planet, and, with transport, recognized that they presented a miniature representation of the Copernican system.

The announcement of these wonders at once attracted universal attention. The spiritual authorities were not slow to detect their tendency, as endangering the doctrine that the universe was made for man. In the creation of myriads of stars, hitherto invisible, there must surely have been some other motive than that of illuminating the nights for him.

It had been objected to the Copernican theory that, if the planets Mercury and Venus move round the sun in orbits interior to that of the earth, they ought to show phases like those of the moon; and that in the case of Venus, which is so brilliant and conspicuous, these phases should be very obvious. Copernicus himself had admitted the force of the objection, and had vainly tried to find an explanation. Galileo, on turning his telescope to the planet, discovered that the expected phases actually exist; now she was a crescent, then half-moon, then gibbous, then full. Previously to Copernicus, it was supposed that the planets shine by their own light, but the phases of Venus and Mars proved that their light is reflected. The Aristotelian notion, that celestial differ from terrestrial bodies in being incorruptible, received a rude shock from the discoveries of Galileo, that there are mountains and valleys in the moon like those of the earth, that the sun is not perfect, but has spots on his face, and that he turns on his axis instead of being in a state of majestic rest. The apparition of new stars had already thrown serious doubts on this theory of incorruptibility.

These and many other beautiful telescopic discoveries tended to the establishment of the truth of the Copernican theory and gave unbounded alarm to the Church. By the low and ignorant ecclesiastics they were denounced as deceptions or frauds. Some affirmed that the telescope might be relied on well enough for terrestrial objects, but with the heavenly bodies it was altogether a different affair. Others declared that its invention was a mere application of Aristotle’s remark that stars could be seen in the daytime from the bottom of a deep well. Galileo was accused of imposture, heresy, blasphemy, atheism. With a view of defending himself, he addressed a letter to the Abbe Castelli, suggesting that the Scriptures were never intended to be a scientific authority, but only a moral guide. This made matters worse. He was summoned before the Holy Inquisition, under an accusation of having taught that the earth moves round the sun, a doctrine “utterly contrary to the Scriptures.” He was ordered to renounce that heresy, on pain of being imprisoned. He was directed to desist from teaching and advocating the Copernican theory, and pledge himself that he would neither publish nor defend it for the future. Knowing well that Truth has no need of martyrs, he assented to the required recantation, and gave the promise demanded.

For sixteen years the Church had rest. But in 1632 Galileo ventured on the publication of his work entitled “The System of the World,” its object being the vindication of the Copernican doctrine. He was again summoned before the Inquisition at Rome, accused of having asserted that the earth moves round the sun. He was declared to have brought upon himself the penalties of heresy. On his knees, with his hand on the Bible, he was compelled to abjure and curse the doctrine of the movement of the earth. What a spectacle! This venerable man, the most illustrious of his age, forced by the threat of death to deny facts which his judges as well as himself knew to be true! He was then committed to prison, treated with remorseless severity during the remaining ten years of his life, and was denied burial in consecrated ground. Must not that be false which requires for its support so much imposture, so much barbarity? The opinions thus defended by the Inquisition are now objects of derision to the whole civilized world.

One of the greatest of modern mathematicians, referring to this subject, says that the point here contested was one which is for mankind of the highest interest, because of the rank it assigns to the globe that we inhabit. If the earth be immovable in the midst of the universe, man has a right to regard himself as the principal object of the care of Nature. But if the earth be only one of the planets revolving round the sun, an insignificant body in the solar system, she will disappear entirely in the immensity of the heavens, in which this system, vast as it may appear to us, is nothing but an insensible point.

The triumphant establishment of the Copernican doctrine dates from the invention of the telescope. Soon there was not to be found in all Europe an astronomer who had not accepted the heliocentric theory with its essential postulate, the double motion of the earth movement of rotation on her axis, and a movement of revolution round the sun. If additional proof of the latter were needed, it was furnished by Bradley’s great discovery of the aberration of the fixed stars, an aberration depending partly on the progressive motion of light, and partly on the revolution of the earth. Bradley’s discovery ranked in importance with that of the precession of the équinoxes. Roemer’s discovery of the progressive motion of light, though denounced by Fontenelle as a seductive error, and not admitted by Cassini, at length forced its way to universal acceptance.

Next it was necessary to obtain correct ideas of the dimensions of the solar system, or, putting the problem under a more limited form, to determine the distance of the earth from the sun.

In the time of Copernicus it was supposed that the sun’s distance could not exceed five million miles, and indeed there were many who thought that estimate very extravagant. From a review of the observations of Tycho Brahe, Kepler, however, concluded that the error was actually in the opposite direction, and that the estimate must be raised to at least thirteen million. In 1670 Cassini showed that these numbers were altogether inconsistent with the facts, and gave as his conclusion eighty-five million.

The transit of Venus over the face of the sun, June 3, 1769, had been foreseen, and its great value in the solution of this fundamental problem in astronomy appreciated. With commendable alacrity various governments contributed their assistance in making observations, so that in Europe there were fifty stations, in Asia six, in America seventeen. It was for this purpose that the English Government dispatched Captain Cook on his celebrated first voyage. He went to Otaheite. His voyage was crowned with success. The sun rose without a cloud, and the sky continued equally clear throughout the day. The transit at Cook’s station lasted from about half-past nine in the morning until about half-past three in the afternoon, and all the observations were made in a satisfactory manner.

But, on the discussion of the observations made at the different stations, it was found that there was not the accordance that could have been desired the result varying from eighty-eight to one hundred and nine million. The celebrated mathematician, Encke, therefore reviewed them in 1822-’24, and came to the conclusion that the sun’s horizontal parallax, that is, the angle under which the semi-diameter of the earth is seen from the sun, is 8 576/1000 seconds; this gave as the distance 95,274,000 miles. Subsequently the observations were reconsidered by Hansen, who gave as their result 91,659,000 miles. Still later, Leverrier made it 91,759,000. Airy and Stone, by another method, made it 91,400,000; Stone alone, by a revision of the old observations, 91,730,000; and finally, Foucault and Fizeau, from physical experiments, determining the velocity of light, and therefore in their nature altogether differing from transit observations, 91,400,000. Until the results of the transit of next year (1874) are ascertained, it must therefore be admitted that the distance of the earth from the sun is somewhat less than ninety-two million miles.

This distance once determined, the dimensions of the solar system may be ascertained with ease and precision. It is enough to mention that the distance of Neptune from the sun, the most remote of the planets at present known, is about thirty times that of the earth.

By the aid of these numbers we may begin to gain a just appreciation of the doctrine of the human destiny of the universe the doctrine that all things were made for man. Seen from the sun, the earth dwindles away to a mere speck, a mere dust-mote glistening in his beams. If the reader wishes a more precise valuation, let him hold a page of this book a couple of feet from his eye; then let him consider one of its dots or full stops; that dot is several hundred times larger in surface than is the earth as seen from the sun!

Of what consequence, then, can such an almost imperceptible particle be? One might think that it could be removed or even annihilated, and yet never be missed. Of what consequence is one of those human monads, of whom more than a thousand millions swarm on the surface of this all but invisible speck, and of a million of whom scarcely one will leave a trace that he has ever existed? Of what consequence is man, his pleasures or his pains?

Among the arguments brought forward against the Copernican system at the time of its promulgation, was one by the great Danish astronomer, Tycho Brahe, originally urged by Aristarchus against the Pythagorean system, to the effect that, if, as was alleged, the earth moves round the sun, there ought to be a change of the direction in which the fixed stars appear. At one time we are nearer to a particular region of the heavens by a distance equal to the whole diameter of the earth’s orbit than we were six months previously, and hence there ought to be a change in the relative position of the stars; they should seem to separate as we approach them, and to close together as we recede from them; or, to use the astronomical expression, these stars should have a yearly parallax.

The parallax of a star is the angle contained between two lines drawn from it one to the sun, the other to the earth.

At that time, the earth’s distance from the sun was greatly under-estimated. Had it been known, as it is now, that that distance exceeds ninety million miles, or that the diameter of the orbit is more than one hundred and eighty million, that argument would doubtless have had very great weight.

In reply to Tycho, it was said that, since the parallax of a body diminishes as its distance increases, a star may be so far off that its parallax may be imperceptible. This answer proved to be correct. The detection of the parallax of the stars depended on the improvement of instruments for the measurement of angles.

The parallax of alpha Centauri, a fine double star of the Southern Hemisphere, at present considered to be the nearest of the fixed stars, was first determined by Henderson and Maclear at the Cape of Good Hope in 1832-’33. It is about nine-tenths of a second. Hence this star is almost two hundred and thirty thousand times as far from us as the sun. Seen from it, if the sun were even large enough to fill the whole orbit of the earth, or one hundred and eighty million miles in diameter, he would be a mere point. With its companion, it revolves round their common centre of gravity in eighty-one years, and hence it would seem that their conjoint mass is less than that of the sun.

The star 61 Cygni is of the sixth magnitude. Its parallax was first found by Bessel in 1838, and is about one-third of a second. The distance from us is, therefore, much more than five hundred thousand times that of the sun. With its companion, it revolves round their common centre of gravity in five hundred and twenty years. Their conjoint weight is about one-third that of the sun.

There is reason to believe that the great star Sirius, the brightest in the heavens, is about six times as far off as alpha Centauri. His probable diameter is twelve million miles, and the light he emits two hundred times more brilliant than that of the sun. Yet, even through the telescope, he has no measurable diameter; he looks merely like a very bright spark.

The stars, then, differ not merely in visible magnitude, but also in actual size. As the spectroscope shows, they differ greatly in chemical and physical constitution. That instrument is also revealing to us the duration of the life of a star, through changes in the refrangibility of the emitted light. Though, as we have seen, the nearest to us is at an enormous and all but immeasurable distance, this is but the first step there are others the rays of which have taken thousands, perhaps millions, of years to reach us! The limits of our own system are far beyond the range of our greatest telescopes; what, then, shall we say of other systems beyond? Worlds are scattered like dust in the abysses in space.

Have these gigantic bodies myriads of which are placed at so vast a distance that our unassisted eyes cannot perceive them have these no other purpose than that assigned by theologians, to give light to us? Does not their enormous size demonstrate that, as they are centres of force, so they must be centres of motion suns for other systems of worlds?

While yet these facts were very imperfectly known indeed, were rather speculations than facts Giordano Bruno, an Italian, born seven years after the death of Copernicus, published a work on the “Infinity of the Universe and of Worlds;” he was also the author of “Evening Conversations on Ash-Wednesday,” an apology for the Copernican system, and of “The One Sole Cause of Things.” To these may be added an allegory published in 1584, “The Expulsion of the Triumphant Beast.” He had also collected, for the use of future astronomers, all the observations he could find respecting the new star that suddenly appeared in Cassiopeia, A.D. 1572, and increased in brilliancy, until it surpassed all the other stars. It could be plainly seen in the daytime. On a sudden, November 11th, it was as bright as Venus at her brightest. In the following March it was of the first magnitude. It exhibited various hues of color in a few months, and disappeared in March, 1574.

The star that suddenly appeared in Serpentarius, in Kepler’s time (1604), was at first brighter than Venus. It lasted more than a year, and, passing through various tints of purple, yellow, red, became extinguished.

Originally, Bruno was intended for the Church. He had become a Dominican, but was led into doubt by his meditations on the subjects of transubstantiation and the immaculate conception. Not caring to conceal his opinions, he soon fell under the censure of the spiritual authorities, and found it necessary to seek refuge successively in Switzerland, France, England, Germany. The cold-scented sleuth-hounds of the Inquisition followed his track remorselessly, and eventually hunted him back to Italy. He was arrested in Venice, and confined in the Piombi for six years, without books, or paper, or friends.

In England he had given lectures on the plurality of worlds, and in that country had written, in Italian, his most important works. It added not a little to the exasperation against him, that he was perpetually declaiming against the insincerity; the impostures, of his persecutors that wherever he went he found skepticism varnished over and concealed by hypocrisy; and that it was not against the belief of men, but against their pretended belief, that he was fighting; that he was struggling with an orthodoxy that had neither morality nor faith.

In his “Evening Conversations” he had insisted that the Scriptures were never intended to teach science, but morals only; and that they cannot be received as of any authority on astronomical and physical subjects. Especially must we reject the view they reveal to us of the constitution of the world, that the earth is a flat surface, supported on pillars; that the sky is a firmament the floor of heaven. On the contrary, we must believe that the universe is infinite, and that it is filled with self-luminous and opaque worlds, many of them inhabited; that there is nothing above and around us but space and stars. His meditations on these subjects had brought him to the conclusion that the views of Averroes are not far from the truth that there is an Intellect which animates the universe, and of this Intellect the visible world is only an emanation or manifestation, originated and sustained by force derived from it, and, were that force withdrawn, all things would disappear. This ever-present, all-pervading Intellect is God, who lives in all things, even such as seem not to live; that every thing is ready to become organized, to burst into life. God is, therefore, “the One Sole Cause of Things,” “the All in All.”

Bruno may hence be considered among philosophical writers as intermediate between Averroes and Spinoza. The latter held that God and the Universe are the same, that all events happen by an immutable law of Nature, by an unconquerable necessity; that God is the Universe, producing a series of necessary movements or acts, in consequence of intrinsic, unchangeable, and irresistible energy.

On the demand of the spiritual authorities, Bruno was removed from Venice to Rome, and confined in the prison of the Inquisition, accused not only of being a heretic, but also a heresiarch, who had written things unseemly concerning religion; the special charge against him being that he had taught the plurality of worlds, a doctrine repugnant to the whole tenor of Scripture and inimical to revealed religion, especially as regards the plan of salvation. After an imprisonment of two years he was brought before his judges, declared guilty of the acts alleged, excommunicated, and, on his nobly refusing to recant, was delivered over to the secular authorities to be punished “as mercifully as possible, and without the shedding of his blood,” the horrible formula for burning a prisoner at the stake. Knowing well that though his tormentors might destroy his body, his thoughts would still live among men, he said to his judges, “Perhaps it is with greater fear that you pass the sentence upon me than I receive it.” The sentence was carried into effect, and he was burnt at Rome, February 16th, A.D. 1600.

No one can recall without sentiments of pity the sufferings of those countless martyrs, who first by one party, and then by another, have been brought for their religious opinions to the stake. But each of these had in his supreme moment a powerful and unfailing support. The passage from this life to the next, though through a hard trial, was the passage from a transient trouble to eternal happiness, an escape from the cruelty of earth to the charity of heaven. On his way through the dark valley the martyr believed that there was an invisible hand that would lead him, a friend that would guide him all the more gently and firmly because of the terrors of the flames. For Bruno there was no such support. The philosophical opinions, for the sake of which he surrendered his life, could give him no consolation. He must fight the last fight alone. Is there not something very grand in the attitude of this solitary man, something which human nature cannot help admiring, as he stands in the gloomy hall before his inexorable judges? No accuser, no witness, no advocate is present, but the familiars of the Holy Office, clad in black, are stealthily moving about. The tormentors and the rack are in the vaults below. He is simply told that he has brought upon himself strong suspicions of heresy, since he has said that there are other worlds than ours. He is asked if he will recant and abjure his error. He cannot and will not deny what he knows to be true, and perhaps for he had often done so before he tells his judges that they, too, in their hearts are of the same belief. What a contrast between this scene of manly honor, of unshaken firmness, of inflexible adherence to the truth, and that other scene which took place more than fifteen centuries previously by the fireside in the hall of Caiaphas the high-priest, when the cock crew, and “the Lord turned and looked upon Peter” (Luke xxi! And yet it is upon Peter that the Church has grounded her right to act as she did to Bruno. But perhaps the day approaches when posterity will offer an expiation for this great ecclesiastical crime, and a statue of Bruno be unveiled under the dome of St. Peter’s at Rome.