been erected to contain a sundial with eight faces, meeting the four cardinal and four intermediate points of the horizon, and a clepsydra; and, by an ingenious contrivance, it would appear that the latter was sometimes made to divide the day into twelve equal parts, the aperture through which the water flowed contracting or enlarging according as the length of the natural day increased or diminished.

A great variety of instruments were constructed by the Alexandrians. Astrolabes, or armillary spheres, were used in the observance of solar and sidereal phenomena. These, in the hands of the Arabs, at a subsequent period were largely improved, and made upon a gigantic scale. Whether any knowledge was possessed of the means by which the natural sight is now assisted in the contemplation of distant objects, is a controverted topic. From some obscure intimations found in the ancient writers of bodies circulating in the universe invisible to the naked eye, it has been conceived that the satellites of Jupiter and Saturn are meant, having been discovered by the aid of instruments analogous to the telescope. Sir W. Drummond assigns a knowledge of that instrument to the Greeks, Chaldeans, and Hindús; but though some strong facts may be quoted in favour of the former, the evidence is not sufficient to warrant the inference. In enabling the eye to bear the brilliancy of the solar light, when directed towards that luminary, various methods were adopted. Aristotle speaks of mirrors being used in his time, probably meaning thin metallic plates finely polished. Ptolemy mentions vessels of oil being employed in viewing eclipses, and Seneca refers to the medium now common, that of smoked glass.

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We now take leave of the ancient world, bewildered by the apparently involved and disorderly movements of the heavens, having hold of no clue by which to arrive at the discovery of their harmony, "puzzled with mazes and perplexed with errors." The economy of the universe was a sealed book to the eye of antiquity-the theory of its best scholar a dream, at utter variance with the truth. The book had been shut for thousands of years previous, and it remained closed for more than a thousand years afterwards. Yet there were not wanting some lofty minds who clearly perceived the discordance between the interpretation given and the facts observed, after all that ingenuity and application had done towards a reconcilement, and who seem to have indulged the anticipation of the appearance of a person able to open the volume and read the perfect coherence of its contents. Such was Seneca the philosopher. "How many things," he remarks, are beyond the reach of human intelligence! and how small is the part of the universe accessible to our knowledge! even the Deity himself is no better known to us." But, as if inspired with the spirit of prophecy, he observes: "The time will come when posterity will be surprised that we could be ignorant of things, the knowledge of which might have been so easily acquired, and some one will at length arise who shall teach men the paths of the comets, their magnitude and number, and why they deviate so far from the routes of the planets." How has the anticipation been realised the prophecy been fulfilled! It is somewhat remarkable that he who in his Natural Questions thus expressed himself, should, in a similarly happy vein, have treated another topic in the tragedy of Medea as follows:- "Eras shall come in late years, in which ocean may loosen the bonds of things, and a spreading continent expand, and Tethys reveal new regions, nor Thule be the boundary to the lands." If the former passage strongly reminds us of Copernicus and Halley, the latter does so equally of Columbus and Vasco de Gama.

o rule the nations with imperial sway, to impose terms of peace, to spare the humbled, and to crush the proud, resigning it to others to describe the courses of the heavens, and explain the rising stars; this, to use the words of the poet of the Eneid in the apostrophe of Anchises to Fabius in the Shades, was regarded as the proper province of a Roman. The genius of the people was even more adverse to the cultivation of the physical sciences than that of the European Greeks; and we have seen that the latter left experimental philosophy chiefly in the hands of the Asian and African colonists. The elegant literature and metaphysical speculations of Athens, her epics, dramas, histories, and orations, had a numerous host of admirers in Italy, but a feeling of indifference was displayed to the practical science of Alexandria. This repugnance of the Roman mind at home to mathematics and physics, together with the prevalence of its military despotism abroad, which extended from the Atlantic to the Indian Ocean, from Northern Britain to the cataracts of the Nile, annihilated in a measure the pure sciences in the conquered districts where they had been pursued, and prohibited attention to them in the mother country. Long, indeed, after the age of Ptolemy, the school in connexion with which he flourished, remained in existence; but, receiving no countenance from the imperial representatives, and the iron yoke of arbitrary power prostrating the energies of the people, it gradually waned, and was finally extinguished by the disorders that broke up the Roman empire. The interval between the overthrow of ancient civilisation by the rude and warlike tribes that took possession of its seat, and the revival of learning, exhibits an entire neglect of the liberal arts, with the exception of the Arabs during the era of their power on the banks of the Tigris in the East, and the Guadalquiver in the West.

The brilliant career of these Children of the Desert, soon after their emergence from it, was marked by an act, committed in the fever of fanaticism-the destruction of the Alexandrian library, which betokened little the literary and scientific ardour of their descendants. The event strikingly contrasts with that which occurred in the reign of Almamon,

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when a long train of camels entered the gates of Bagdad laden with volumes of imported learning, the fruit of a treaty made with the emperor of the East which imposed upon him the condition of furnishing copies of all the Greek authors. The medicine of Galen, the metaphysics of Aristotle, and the astronomy of Ptolemy, thus came into the hands of the caliph, and speedily appeared in the language of the caliphate. Arabian cultivation commenced with the dynasty of the Abassides, or the middle of the eighth century. Three princes in succession, Almansor, Alraschid, and Almamon, used every means in their power to promote the growth of learning among their people, and the advantages supplied by their fine climate were not lost upon the followers of the Prophet, when a taste for astronomical science had been created; for upon the same sites where the old Chaldeans, two thousand years previously, had gazed with wonder upon the heavens, they entered upon a course of observation, with all the ardour common to their impulsive character, guided by the light of the Greek results. The work of Ptolemy was their text-book; his system, theirs but instruments were constructed upon a larger scale; his determinations were subjected to a rigid examination; and in many instances a more accurate conclusion was obtained. The length of the tropical year was found within a few seconds of the truth. A degree of the terrestrial meridian was measured in the Desert near Palmyra, to verify the value obtained by Eratosthenes. The obliquity of the ecliptic was determined. The great inequalities also of Jupiter and Saturn are marked in the tables of planetary motions constructed by the Arab astronomers. Their observations, in general, of the celestial bodies have a greater degree of accuracy than those of the Greeks, on account of the necessary correction being made for the phenomena of refraction, which was observed with reference to bodies near the horizon. Bagdad, however, was only the centre of a movement in favour of science. The impulse extended as wide as the language and profession of Islam, to Egypt, Morocco, and Spain; and it long survived after the political power of the Eastern caliphs, which had gleamed like a meteor, had as suddenly vanished. An observatory was erected in the northern part of Persia, by a descendant of Gengis-Khan ; and Ulugh Beg, a prince of the house of Timour, erected one at Samarcand, where he compiled his now extant catalogue of the stars. The preface to this work states that eight stars marked in the catalogue of Ptolemy could not then be found in the heavens. This may have arisen simply from a mistaken entry in the first instance; but, if a case of real disappearance, it is far from being the only one, though a profound mystery. Arabian cultivation attained its meridian splendour in Spain at a period when the rest of Europe was plunged in darkness. Through intercourse with the Moors of that country, some gleams of light gradually radiated through the Continent; and undoubtedly they are to be regarded as having transmitted the torch of civilisation from antiquity to modern ages. Among the first fruits of their influence, the construction of the Alphonsine tables may be placed, a work of the king of Castile of that name, chiefly confined to a more accurate determination of the motions of the sun and planets, and the length of the year, the materials for which were derived from his Mahommedan neighbours to the south. There is little to detain us of any interest or importance in relation to astronomy, at this era, in countries where it has now arrived at such marvellous perfection. Observers abounded in the middle ages; but their midnight watchings of the great canopy of heaven had very generally only an astrological purpose in view. Speculatists were numerous respecting the mechanism of the universe; but blindly adhering to the doctrines of the earth's immobility, and of the uniform and circular motions of the celestial lights, they laboured hard, but in vain, to adjust observed phenomena with preconceived theory. The Aristotelian notion of the spheres was revived in all its grossness, and huge materialities were conceived to constitute the eternal paths of the bodies composing the solar system, necessary to the end of keeping them in place. To account for all the celestial move

ments, several of these solid spheres were required to be in attendance upon the same body, and to be of various structure; and they were multiplied and shaped, until a system was imagined which it fairly baffled the inventors to comprehend. The remark of the Castilian monarch respecting this intricate and cumbrous architecture was not without some justification, though breathing an irreverent spirit: "Had the Deity," said he, “consulted me at the creation of the universe, I could have given him some good advice."

The presumptive evidence against the truth of the Ptolemaic theory is admirably, though not professedly, expressed by Milton, in the representation of Adam reasoning,

How Nature, wise and frugal, could commit
Such disproportions,

as the supposition of the revolution of the firmament round the earth involves. It must then travel, as he argues, "spaces incomprehensible," the "swift return diurnal" implying a swiftness not to be described or imagined; and when the phenomena of the celestial appearances are accounted for, and day and night produced, by the simple rotation of the earth upon its axis, and its translation in space, the presumption is strong, that "Nature, wise and frugal," would never "commit such disproportions," as the theory of terrestrial repose and firmamental movement supposes. But it is difficult for the mind to disengage itself from the force of a universal opinion, especially when it is sanctioned by a venerable antiquity; and hence, it was not until some time after the era of Copernicus, and not until after many a battle in behalf of the faith of past ages, that his system, beautiful for its simplicity, and now demonstratively proved to be correct in its leading features, received the credence of mankind. It was reserved for this great man, born on the banks of the Vistula, to deviate from the path of his predecessors, to renounce allegiance to the speculative physics of Aristotle, and to point the way, though with a cautious footstep, to the true system of the universe; a labour which occupied upwards of thirty years of his life, one of the most glorious achievements that has marked the page of human history. He it was who revolutionised for ever the face of astronomical science, and in the magnificent language of one of his immediate followers, "commanded the sun to stand still, moved the earth from its foundations, stopped the revolution of the firmament, and subverted the whole ancient order of the universe."

NICHOLAS COPERNICUS, or ZEPERNIC, was born at Thorn, near the place where the Vistula crosses the Polish frontier, some time in the years 1472 or 1473. He was educated with an eye to his father's profession, that of medicine, but was happily diverted from it by accidentally hearing a course of lectures, which inspired him with a passion for astronomy. He was at Bologna in Italy in 1497, studying the science under Dominic Maria, and settled for a time at Rome as a teacher of mathematics, where he established a considerable reputation. His uncle, who was a dignified ecclesiastic, bishop of Ermeland, upon a vacancy occurring in the canonry of his cathedral church of Frauenburg, appointed Copernicus to the place in the chapter, who had previously taken orders probably in Italy. Here he passed the remainder of his days, dividing his time between his ecclesiastical duties, the gratuitous practice of medicine among the poor, and astronomical researches. He went but little into company, seldom conversed except on serious and scientific topics, was mild and gentle in his manners, and steadfast in his friendships. Frauenburg is a small town on the coast, not far from the junction of the Vistula with the sea. There, in a house situated on the brow of a mountain, overlooking the waters of the Gulf of Dantzic, he pursued his enquiries into the economy of the universe in peaceful seclusion, confident that he was doing a great work for posterity to appreciate. His mind was profoundly impressed with the idea that simplicity characterises the arrangements of

nature; and, struck with the want of this in received hypotheses, he seems to have come to the conclusion that such scenes of complexity could not be true representations of the heavens. It does not appear when his own views became settled; but in the year 1530, the manuscript of his work "On the Revolutions of the Heavenly Bodies was finished." In this production he disclosed his system: the Earth, a planet revolving round the Sun in an orbit between Venus and Mars; its rotation upon its axis producing the apparent diurnal procession of the heavens; the complicated movements of the planets being the consequence of their own motions in space, combined with that of the Earth. It is difficult to appreciate fully the freedom of spirit and independence of thought displayed in thus rising superior to the prejudices of centuries, now that the truth of the system has been long settled; neither is it easy to conceive the delight and awe which must have filled the mind of its author, when, after years of patient and intense application, he was permitted to gaze upon the mechanism of the heavens unveiled, in its simplicity and grandeur, from his mountain home at Frauenburg.

The prudence of the great discoverer in propounding his views is no less admirable than his sagacity in seizing hold of them. Aware of the obstinacy with which human nature clings to its early imbibed opinions, he was careful not to rouse hostility by an abrupt dogmatic attack upon the ancient theory. He communicated privately with his friends; Reinhold and Rheticus, astronomers; Schomberg, a cardinal; and Gyse, a bishop. With these parties his views found acceptance. They were discussed in their respective circles, and obtained a number of converts; not, however, without opposition, for Copernicus was satirised upon the stage at Elburg. His work, completed in 1530, was still in manuscript in 1540, notwithstanding repeated efforts to induce him to publish it. An arrangement at length was made, during the latter year, for Rheticus to furnish an account of the manuscript volume; and, that being favourably received, Copernicus consented to the appearance of his own production. It was committed into the hands of Rheticus; Andrew Osiander of Nuremberg superintended the printing, and Cardinal Schomberg bore the expense. But the illustrious author did not live to read his work in print. A copy was handed to him as he lay, a paralytic, upon his bed. He saw it, he touched it, and in a few hours afterwards expired, May 23. 1543. The cathedral of Frauenburg received his ashes without pomp or epitaph, except that upon his tombstone some spheres were cut in relief. The great square of Warsaw has a statue in honour of his memory; and the civilised world holds his name in reverence, as one whose genius dissipated the illusions of the senses, and discovered the true astronomy. Copernicus is described as a man of ruddy complexion and light hair. A portrait, painted by himself, a half-length, came into the hands of Tycho Brahé, who made it the subject of an epigram to the effect that the whole earth would not contain the whole of the man who whirled the earth itself in ether.

The scheme of Copernicus was presented to the world in the form of hypothesis. It could not be broached in any other manner, for not until the discovery of the aberration of the stars by Bradley, and the determination of the diminution of gravity at the equator by Richter, was demonstration given to the doctrine of the earth's rotation and translation in space. "Astronomers," he remarks, in the dedication of his work to Paul III., "being permitted to imagine circles to explain the motions of the stars, I thought myself equally entitled to examine if the supposition of the motion of the earth would render the theory of these appearances more exact and simple." But, though the resolving the apparent diurnal revolution of the sphere into the actual diurnal motion of the globe in an opposite direction was a pure hypothesis, yet we have so many examples of a real movement on our part producing an apparent antagonistic motion in other bodies, as when we sail along a river or travel on a railway, while there is something so manifestly absurd in supposing the daily revolution of the firmament, that, even if no demonstration