John Muller of Koningsberg, better known by the name of Regiomontanus, repaired to Vienna at an early age, to receive instructions from Purbachius. At the death of his master, he went to Rome, to prepare him self for the study of the Almagest, by the acquisition of the Greek language. IIis numerous translations of Greek authors, and his treatise on trigonometry, added so greatly to his reputation, that the senate of Nurem berg invited him to that city. Having accepted the in vitation, Regiomontanus erected an observatory, with the pecuniary aid of a wealthy citizen, Bernard Wal ther, and furnished it with excellent instruments, which he had himself either invented or improved. In Fe bruary, 1472, Regiomontanus made observations on a comet which had a tail more than 30 degrees long, and in its motion towards its perigee, described an arch of 30 degrees in 24 hours. When pope Sextus IV. pro posed to reform the calendar, he invited Regiomontanus to Rome to direct and execute this important work. Al lured by the most magnificent promises, and by his no mination to the bishopric of Ratisbon, Regiomontanus repaired to Rome in 1475, but was cut off by the plague a few months after his arrival.
The place of Regiomontanus was in some measure supplied by Walther, his friend and disciple, who conti nued to observe the heavens about 30 years after the death of his master. This astronomer was the first who made use of clocks in his astronomical observa tions, and he had discovered the effects of refraction be fore he had read the works of Alhazen and Vitellio. His numerous observations on eclipses and occultations, and on the longitudes and distances of the planets, kc. were published along with those of Regiomontanus in 1544, by order of the senate of Nuremberg.
Walther was succeeded by John Werner, a clergy man at Nuremberg. After studying astronomy at Rome, he returned to his own country, and described the orbit of the comet which appeared in April, 1500. In the commentary which he added to his translation of Ptole my's Geography, lie explains the method which is now employed for finding the longitude at sea by the dis tance of a fixed star from the moon. He constructed a machine for representing the motion of the planets, and he found the precession of the equinoxes to be 1° 10" in 100 years.
Astronomy now begins to advance with rapid steps, under the guidance of the illustrious Copernicus, who was a native of Thorn in Prussia. Allured to the study of the heavens by the high reputation of Regiomonta nus, he went to receive instructions from Dominic Ma ria, professor of astronomy at Bologna. From Bologna he went to Rome, where, being appointed professor of mathematics, he made several observations about the year 1500. Returning to Nuremberg, where lie was made canon of Ermeland by his uncle the bishop of Wurmia, he directed his attention to the various hypo theses which had been invented to explain the celestial motions ; and being embarrassed by the epicycles and eccentrics of Hipparchus and Ptolemy, which he re garded as inconsistent with the simplicity of nature, he adopted the system of Pythagoras respecting the motion of the earth, and the immobility of the sun. From this
hypothesis all the celestial phenomena received a plau sible explanation. The diurnal motion of the heavens was a deception arising from the motion of the terres trial globe ; and the precession of the equinoxes was explained by a slight variation in the position of its axis. The stations and retrogradations of the planets, which had so long perplexed astronomers, were the necessary consequences of this new arrangement ; and, to use the words of Copernicus himself, " The several appear ances of the heavenly bodies will not only follow from this hypothesis, but it will so connect the order of the planets, their orbits, magnitudes, and distances, and even the apparent motion of the fixed stars, that it will be impossible to remove one of these bodies out of its place without disordering the rest, and even the whole universe also." This beautiful system, remarkable for its simplicity, and its conformity with all the laws of me chanicks and physicks, has been defended by its author against every objection, and is fully explained in the first book of his work, entitled, Astronomia Instaurata, sive de Revolutionibus Orldum Celestium. This work was completed about the year 1530; but, dreading the consequences of vulgar prejudice, it was only in the latter part of his life that his friends could prevail upon him to give it to the world. The rupture of a blood vessel put a sudden termination to the life of this great man, on the very same day on which he received a com plete copy of his work. His remains were deposited near the altar, in the cathedral of Frauenberg, and spheres cut out in relief upon his tomb, was the only epitaph that recorded his labours. This hallowed spot, which no philosopher could approach without the deep est sensations of reverence and awe, has a few years ago been most wantonly violated by two pretended friends of science, who went in quest of the manuscripts of Co pernicus, with the intention of doing honour to his name. No sooner had they entered the cathedral, and washed the dust from the tomb of the astronomer, than they raised up the stone which protected his grave, and carried off the few mouldering bones which for nearly three centuries had reposed in that sacred spot. These valuable relics were given to the chapter of the cathe dral, and a few reserved to gratify the impious curiosi ty of the Polish travellers. See COPERNICUS.