Between the time of Hipparchus and Ptolemy, the chief observers of any note are Agrippa, liLmelaus, and Theon; the two latter of which are better known as geometriciansthan astronomers. We mark, however, in this interval, the re'.
formation of the calendar by Julius Cxsar, and a more exact knowledge of the flux and reflux of the ocean. We pass over the dark ages, and observe that Frederic II. about 1230, set himself to restore some decayed universities, and founding a new one at Vienna. He also caused the works of Aristotle, and Ptolemy's Almagest, to be translated into Latin ; from which lat ter circumstance we may date the revival of astronomy in Europe. Two years after this, John of Halifax, commonly known by the name of Sacro Bosco, compiled, from Ptolemy, Albategnius, Alfraganus, and other Arabic astronomers, his work "De Sphxra," which continued in great estimation for more than 300 years after wards, and was honoured with commen taries by Clavius, and other learned men. Alphonsus, King of Castile, may also be reckoned as one of the most zealous en couragers and protectors of this science ; though, being but ill seconded by the astronomers of that time, the tables which he published were not found to answer the great expense which attended them. See AVIAOEST.
About the same period also Roger Ba con, an English monk, besides many learn ed works of various kinds, wrote several treatises on astronomy ; after which but little progress was made in the science till the time of Purbach, Regiomontanus, and Walther, who all flourished about the end of the fifteenth century, and by their labours prepared the way for the great discoveries which followed. Itegiomon tanus, in particular, who was born at Ko ningsberg, a town of Franconia, in 1426, and whose proper name was John Muller, rendered considerable services to astro nomy, not only by his observations and writings, but by his trigonometrical tables of sines and tangents, which he computed to a radius of 1,000,000 for every minute of the quadrant, and by this means great ly facilitated astronomical computations. Next after these was Nicholas Coperni cus, the celebrated restorer of the old Pythagorean system of the world, which had been now set aside ever since the time of Ptolemy. He was born at Thorn, in Polish Prussia, in 1743, and having gone through a regular course of studies at Cracow, and afterwards at Rome, he was made, by the interest of his uncle, who was bishop of Wormia, a canon of Fraw enberg in which peaceful 'retreat, after 36 years of observations and meditations, lie established his theory of the motion of the earth, with such new and demonstra tive arguments in its favour, that it has gradually prevailed from that time, and is now universally received by the learned throughout Europe. This great man, however, had not the satisfaction of wit nessing the success of his undertaking ; being threatened by the persecution of -religious bigots on the one side, and with an obstinate and violent opposition from those who called themselves philosophers on the other, it was not without the great est solicitations that he could be prevail ed upon to give up his papers to his friends, with permission to make them public ; but, from continued importunities of this kind, he at length complied, and his book, " De Revolutionibus Orbium Ccelestium," after being suppressed for many years, was at length published, and a copy of it brought to him a few hours before his death. From Copernicus we
proceed to Tycho Brahe, the celebrated Danish astronomer, who was born in 1546, and began to manifest his taste for this science at the early age of 14. An eclipse of the sun, which happened in 1560, first attracted his attention, and the justness of the calculation which announced this phxnomenon inspired him with a strong desire of understanding the principles upon which it was founded. But meet ing with some opposition from his tutor, and a part of his family, to these pursuits, which probably served only to increase his attachment to them, he made a jour ney into Germany, where he formed con nections, and entered into a correspon dence with some of the most eminent astronomers of that country, particularly with the landgrave of Hesse, who receiv ed him in the most flattering manner, and recommended him to the notice of his sovereign. Becoming by this means bet ter known, on his return to Denmark, Frederic II. gave him the little island of Iluen, at the entrance of the Baltic, where he built an observatory, under the name of Uraniburg, and in which, during a course of 20 years, he made a prodigious number of observations. His tranquillity, however, in this happy retreat, was at length interrupted; for soon after the death of Frederic, which happened in 1596, he was deprived, through the as persions of some envious and malevolent persons, of his pension and establishment, and was not allowed even to follow his pursuits at Copenhagen, a minister of that time, of the name of Walchenderp, having tbrbid him to continue his obser vations. Happily, however, he found a powerful protector in the Emperor Ro dolphus II. who ordered him to be pro perly provided for at his own expense, and gave him a commodious house at Prague. After residing in this city till the year 1601, he was taken off by a sud den death, in the midst of his labours, and at an age while he was yet capable ofren dering great services to astronomy. This great man, as is well known, was the in ventor of a kind of semi Ptolemaic system of astronomy that was afterwards called by his name, and which he vainly endea voured to establish, instead of the Coper nican, or true system. But though he was not happy in this respect, he has been of great use to astronomy, by his numerous observations and discoveries.