could be conducted under very favourable circumstances; and in its walls are still to be seen the openings which he made, in order to observe the passage of stars across the meridian. It is supposed to have been about the year 1507 that he first became convinced of the superiority of the planetary theory of Pythagoras. He determined, however, to be very cautious in adopting, and still more cautious in announcing, an opinion so much at variance with the ordinary ideas of mankind. Mathematical instruments were in that age very rude, and the telescope had not been invented. The only implements which Copernicus had for making observations were two, coarsely framed of firwood, with measures marked by lines of ink. Thus provided, he devoted himself for several years to the inquiries necessary for proving his theory; and at length, about the year 1530, he had completed a work, in which the whole system was expounded-namely, the immobility of the sun in the centre of the planetary system; while its apparent motion, and the alternations of day and night, were to be attributed to the annual and diurnal movements of the earth. The real distances of the planets, and the declination of the pole of the earth, were also explained.

The doctrines of Copernicus were already known to a considerable number of learned and comparatively enlightened persons, who received them with due respect; and it is creditable to the Romish church that several of its dignitaries were among the number. But the bulk of mankind, including their religious teachers, were then comparatively ignorant, and accordingly prejudiced; and however firm the conviction of the astronomer as to the truth of his theory, he yet hesitated to make it public, dreading the opposition it would have to encounterseeing that it opposed the inveterate prejudices of the learned, and the illusory testimony of the senses. In reasoning, they acted under the guidance of rules which made it scarcely possible for them to ascertain truth, or to acknowledge it when it was presented to them in the clearest light. If anything had been said in former times by a person whose memory they respected, they would not willingly listen to anything which contradicted, or seemed to contradict it. They walked, in short, by authority, and not by the dictates of reflection; and the consequence was, that every new truth which experience or the inquiries of the best minds brought forth, had to contend with the less worthy notions which had come down from earlier and darker ages. Amongst the opinions received by them, was that which represented the earth as the immovable centre of the universe. It was sanctioned by the greatest men of ancient times; it had long been taught; it was conformable to the common appearances of things; and various passages in the Scriptures were believed to assert it, though in reality those passages only do not contradict (and this probably for wise purposes) the ordinary ideas of mankind respecting the stability of the earth. Copernicus only

acted, therefore, with necessary caution, when he hesitated to publish the work which had cost him the labour of so many years.

Rheticus, one of the friends to whom he had communicated his theory, at length, in 1540, ventured to give an outline of it to the world in a small pamphlet, which he published without his name. As this excited no disapprobation, the same person reprinted it next year with his name. In both publications the doctrines were ascribed openly to Nicolas Copernicus. About the same time, a learned man, Erasmus Reinhold, in a work which he published, spoke of the new doctrines with the greatest respect, and styled their author a second Ptolemy; for it often happens that the greatest compliment that can be paid to the discoverer of truth, is to mention him in the same breath with some founder of error. Copernicus now allowed himself to be persuaded by his friends to publish his work; and it was accordingly put to press at Nuremberg, under the care of some learned persons of that city. But he was now an old man, and it was not his lot to live to see the book published. As soon as it was printed, a copy of it was sent to him by his friend Rheticus, but it only reached him, May 23, 1543, a few hours before he expired. He appeared to be scarcely conscious of the object to which so many years of his life had been devoted. But his mission was accomplished. Committed to the perpetuating operations of the infant printing-press, all danger was over of losing the germ of those great and fertile truths which in our days render astronomy the most perfect of sciences.

The theory of Copernicus was thus brought before the world; but, whether from the death of the philosopher, or because little disturbance of popular notions was anticipated from so learned a work, or from whatever other circumstances, it was visited with no marks of reprobation from any quarter at the time. In proportion, however, as it became known, so did its opponents increase. Those were the days when the fagot and stake made short work with those who presumed to strike out a course of thinking for themselves; and though the author of the system and its immediate adopters passed unmolested, yet during the century which ensued were its followers and supporters persecuted with all the zeal and cruelty that bigotry and ignorant prejudice could devise. Truth, however, is imperishable; and, though repressed and retarded for a season, is ever sure to take its right place among the established beliefs of mankind. And thus it has been with the Copernican theory, whose importance to the progress of accurate science we cannot in reality overestimate. To form anything like an adequate idea of the value of its author's services to the cause of science, we must place ourselves back in the times and circumstances which saw their birth. Then, it must be remembered, the want of telescopes rendered all appearances in the sky much more difficult of explanation than they would have been a century later, The accu

mulated errors and superstitions of fourteen centuries were not to be easily shaken and removed; neither were the prejudices and dogmas of the learned to be disturbed with impunity. What might have been astronomical science, was, even in the writings of the fathers, little better than a mass of absurd and subtle disquisitions on the substance of the heavens and the heavenly bodies. All these Copernicus had to surmount; and the elaboration of his theory presents an ever-memorable example of the power of patient and earnest thought in the investigation of a complicated subject, and acuteness of discrimination between the true and the fallacious.

TYCHO BRAHÉ.

Or eminent astronomers, the next in point of time was Tycho Brahé, who, though adopting the Ptolemaic notion of the earth being the fixed and immovable centre of the universe, yet did good service to the progress of the science by his numerous observations and discoveries. Descended of an ancient and noble family, originally of Sweden, but settled in Denmark, Tycho was born December 14, 1546, at Knub Strup, in the bailiwick of Schönen, the jurisdiction of which was then held by his father. When seven years old, he commenced the study of the classics, his education, as well as that of his brothers, being intrusted to private tutors. His father dying, his uncle sent him, in 1559, to study philosophy and rhetoric at Copenhagen, where it was intended to train him for some civil employment. The great eclipse of the sun on the 21st August 1560 happening at the precise time the astronomers foretold, he began to look upon astronomy as something divine; and purchasing the tables of Stadius, gained some notion of the theory of the planets. His thoughts were now wholly engrossed with astronomy; and though sent by his uncle, in 1562, to study jurisprudence at Leipsic, mathematics, and not law, were the subject of his private labours. It is told of him, that, having procured a small celestial globe, he was wont to wait till his tutor had gone to bed, in order to examine the constellations and learn their names; and that, when the sky was clear, he used to spend whole nights in viewing the stars. He abandoned the amusements and pleasures fitting for his age, and devoted his pocket-money to the purchase of mathematical and astronomical books, the perusal of which he persisted in, in spite of the remonstrances and rebukes of his preceptor. About this time he also began to apply himself to chemistry, less perhaps for the cause of the science, than with a view to discover the Philosopher's Stone and the grand Elixir of Life-a digression from his astronomical career, prompted no doubt by the natural superstition and enthusiasm of his constitution.

In 1571 he returned to Denmark; and was favoured by his mother's brother, Steno Belle, a lover of learning, with a convenient place at the castle of Herritzvad, near Knub Strup, for conducting his observations and building a laboratory: but marrying a peasant girl beneath his rank, such a violent quarrel ensued between him and his relations, that Frederick II., king of Denmark, was obliged to interpose to reconcile them. In 1575 he began his travels through Germany, and proceeded as far as Venice, meeting with the kindliest attention from various philosophers and crowned heads. This attention, conjoined with certain offers made him by the Landgrave of Hesse, and the greater facility of procuring better apparatus, induced him to think of removing his family to Basil; but Frederick of Denmark, being informed of his design, and unwilling to lose such an ornament to his country, promised (to enable him to pursue his studies) to bestow upon him for life the island of Hveen in the Sound, to erect an observatory and laboratory there, and to defray all the expenses necessary for carrying on his designs. Tycho Brahé readily embraced this proposal; and, accordingly, the first stone of the observatory was laid in August 1576. The king also bestowed on him a pension of two thousand crowns, a fee in Norway, and a canonry, which brought him one thousand more. In this retreat he was visited by various princes; among others, by James VI. of Scotland, when proceeding to Denmark to marry the princess Anne. This monarch, of literary memory, made the astronomer several presents, and with his own hand wrote some verses in his praise. In Uranienborg, for such he had styled his new erection, he framed that system of the universe which is yet known by his name; namely, that the earth remains fixed and immovable as the grand centre, and that the sun and all the heavenly bodies revolve round it-a doctrine the reverse of that of Copernicus, which all succeeding astronomers have adopted. But though mistaken in this conception, we are indebted to him for a more correct catalogue of the fixed stars; for several important discoveries respecting the motions of the moon and the comets, and the refraction of the rays of light; and for valuable improvements in astronomical instruments. Tycho was likewise a skilful chemist, and found in poetry his recreation from severer studies. His Latin poems are said to exhibit considerable merit; but his chemical manipulations partook too much of the alchemy of his day to be of use to future inquirers.

Happy might our philosopher have been in the castle of Uranienborg, had not his impetuous character, and his fondness for satire, made him many enemies, who prejudiced Christian IV., the successor of Frederick II., against him. On the death of his patron, he was deprived of his pension, fee, and canonry; and finding himself incapable of bearing the expenses of his observatory, he went to Copenhagen, whither he brought some of his instruments, and continued his observations in the city, till Val

kendorf, chamberlain to Christian, commanded him, by the king's orders, to discontinue them. He then removed his family to Rostock, and afterwards to Holstein, to solicit Henry Ranzon to introduce him to the Emperor Rodolphus, who was a great friend to astronomy and astrology. Succeeding in his wishes, he was received by the emperor with the greatest civility and respect; provided with a magnificent house, till he could procure one more fit for astronomical observations; allotted a pension of three hundred crowns; and promised, upon the first opportunity, a fee for himself and his descendants. Unluckily, he did not long enjoy this happy situation; for, being suddenly taken ill with a fatal disease, he was cut off on the 24th of October 1601, in the fifty-fifth year of his age. He was interred with great pomp and ceremony in the principal church of Prague, where a noble monument was erected to his memory; thus, like many other men of eminence, receiving in a strange land the honours that had been denied him in his own.

Tycho was, notwithstanding his faults and weaknesses, a remarkable man for the age in which he lived; his errors and misjudgments being to a great extent those of his era. His skill in astronomy is universally admitted; and though failing to establish his system over that of Copernicus, yet no one can deny him the merit of advancing by his labours the progress of the science. That he was addicted to astrology, presages, and the occult sciences, is true; but these were features of the age more than of individuals: that he was impetuous, sarcastic, and unamiable, is to be regretted; but it must also be admitted that the grossest injustice was done him and the cause of science by the successor of his patron. Most of his works, which were numerous, and written in Latin, are still extant. The Emperor Rodolphus purchased his expensive astronomical and other instruments; but they were mostly destroyed after the battle of the Weisseberg, near Prague, in 1620. A large sextant alone remains in Prague. The famous brass celestial globe, which was six feet in diameter, and cost about a thousand pounds, returned to Copenhagen after various adventures, but perished in the great fire of 1728. The castle of Uranienborg, where he nightly watched and pondered, has long been in ruins, leaving scarcely a trace of its structure and character. All, however, has not perished, nor been fruitless. "It was the friendship of Tycho," says an eminent authority, "which formed Kepler, and directed him in the career of astronomy. Without this friendship, and without the numerous observations of Tycho, of which Kepler found himself the depositary after the death of his master, he would never have been able to discover those great laws of the system of the world which have been called 'Kepler's Laws,' and which, combined with the theory of central forces, discovered by Huygens, conducted Newton to the grandest discovery which has ever been made in the sciences-that of universal gravitation."