In the thirteenth century, astronomy, as well as other arts and sciences, began to re. rice in Europe, particularly under the auspi ces of the emperor Frederick IL ; who, he shks; restoring some decayed universities, founded a new one, and in 1230 caused the works of A rimode, and the Almagest of Ptole my, to be translated into Latin. Two years after this, John de Sean Damn or John of published his work De Sphara, a compendium of astronomy drawn from the works of Ptolemy, Alfra,gan, AllioTnins, and others. This was held in high estimation for some centuries, and was honoured with a commentary from the pen of Clavius and other learned men. In 1240, Alphonsus king of Castile, a great astronomer himself, and an encourager of astronomers, corrected with their assistance the tables of Ptolemy, which, from him, were called the Alphonsine tables Atom the same time Roger Bacon published his tracts on astronomy, and shortly after Vitellio, a Polander, in his treatise on optics, showed, in ao:ordance with Alhazen, the use of refrao thin in astronomy. Nearly two centuries elapsed from this period before any fiirther made in the science, when Pm Inch composed new tables of sines for every ten minutes, constructed spheres and globes, wrote commentaries on Ptolemy's Almagest, corrected the tables of the planets and the Al phonsine tables, determined the obliquity of the ecliptic at 23 degrees 33 minutes and a halt; and begun, at his death, a new series of tables for computing eclipses. He was suc ceeded by John Muller, commonly called Re. giomontanus, Bernard Walther, John Wer ner, and others. John Werner showed that the motion of the fixed stars, since called the precession of the equinoxes, was about 1 de gree 10 minutes, in a hundred years. The celebrated Copernicus came next in order, who distinguished himself by calling in ques tion the Ptolemaic system of the universe, and reviving that of Pythagoras. After making a series of observations, and forming new tables, he completed in 1530 his work, first published under the title of De Revolutionibus Ccelesti urn Orbium, and afterwards tinder that of Astronomia Instaurata, in which he set forth the system since known by the name of the solar system, in which all the planets are con sidered as revolving round the sun as their immoveable centre.
The science of astronomy henceforth con tinued to receive regular accessions and im provements by a series of writers, as Schoner, Nonnius, Appian, Gemma, Prisms, Byrgius, &c. Besides, William IV., landgrave of Hesse Cassel, applying himself to the study, formed, by the help of the best instruments then to be procured; a catalogue of four hun dred stars, with their latitudes and longitudes adapted to the beginning of the year 1593. About this time the Copernican system found a strenuous though unsuccessful opponent in Tycho Brahe, a Danish nobleman, who to obviate the objections against the Ptolemaic system, advanced an hypothesis of his own, which added less to his reputation, than the accurate observations which he made, by the help of improved instruments, in a new obser vatory built for him by order of the king of Denmark. His friend Kepler, who enjoyed the title of mathematician to the emperor, fin ished his tables after his death, and published them under the title of Rhodolphine tables. This latter astronomer discovered that all the planets revolve round the sun, not in circular but in elliptical orbits ; that their motions are not equable, but quicker and slower as they are nearer to the sun or farther from him ; besides a number of other observations on the motions and distances of the planets. He also conclu ded, from his observations on the comets, that they are freely carried about among the orbits of the planets in paths that are nearly rectili near. To the astronomers of this age may be
added Bayer, who, in his Uranometria, has given ; reprecentation of all the constellations; with the stars marked on-them, and accompa nied with the Greek letters for the conveni ence of reference. ° The seventeenth century added many great names to the list of astronomers, as Galileo, Huygens, Cassini, Hevelius, Newton, and Plarnstead, &c. As the Copernican system had met with an opponent in one that ranked' high in the science, it found a defender in Gali leo, an Italian nobleman, who in his Dialog', in 1632, drew a comparison between the, Ptolemaic and Copernican system, much to the advantage of the latter, for which he in curred the censures of the church, as the doc trine of the sun's immobility was looked upon as directly opposed to the express language of Although Galileo professed to re. cant in order to obtain his liberation from prison, yet the system daily gained ground, and became at length established. Galileo besides made many accurate observations in astrono my, and was one of the first who, by improv ing the new invention of the telescope, was enabled to employ them in advancing his fa vourite science. By this means he is said to have discovered inequalities in the moon's surface, Jupiter's satellites, and the ring of Saturn ; so likewise spots in the surface of the sun, by which he found out the revolution lof that luminary on its own axis. He also as certained what Pythagoras had conjectured, that the milky way and the nebulae consisted of innumerable small stars. Harriot made similar discoveries in England at the same time if not earlier. Hevelius, by means of his observations, formed a catalogue of fixed stars much more complete than that of Tycho's. Huygens and Cassini discovered the satellites lof Saturn, and Sir Isaac Newton demonstra ted, from physical considerations, the laws which regulated the motions of the heavenly bodies, and set bounds to the planetary orbs, determining their excursions from the sun, and their nearest approaches to him ; he also explained the principle which occasioned that constant and regular proportion, observed ooth lby the primary and secondary planets in their revolutions round their central bodies, and their distances compared with their periods. His theory of the moon, grounded on the laws of gravity and mechanics, has also been found to account for all her irregularities. Mr. Plamstead filled the office of Astronomer Royal at Greenwich from 1675 until his death ire 1729, during which time he was constantly employed in making observations on the phe° nomena of the heavens. As the result of his labours, he published a catalogue of three thou sand stars, with their places to the year 1689 ; also new solar tables, and a theory of the moon according to Horrox. On his tables was con structed Newton's theory of the moon, as also the tables of Dr. Halley, who succeeded him in Lois office in 1729. Besides composing tables of the sun, moon, and planets, Dr. Halley ad ded to the list of astronomical discoveries, be ing the first who discovered the acceleration of the moon's mean motion. He also contrived a method for finding her parallax by three ob served places of a solar eclipse, and showed the use that might be madeof the approaching transit of Venus in 1761, in determining the distance of the sun from the earth, and recom mended the method of determining the longi tude by the moon's distance from the sun and certain fixed stars, which was afterwards suc cessfully adopted by Dr. Alaskelyne, Astrono mer Royal.