PTOLEMY (CL/towns), in biography, a very celebrated geographer, astrono mer, and mathematician, among the an cients, was born at Pelusium, in Egypt, a bout the seventeenth year of the Christian era, and died, it has been said, in the se venty-eighth year of his age, and in the year of Christ 147. He taught astrono my at Alexandria, in Egypt, where he made many astronomical observations, and composed his other works. It is cer tain that he flourished in the reigns of Marcus Antoninus and Adrian ; for it is noted in his Canon, that Antoninus Pius reigned twenty-three years, which shows that he himself survived him : be also tells us in one place, that he made a great many observations upon the fixed stars at Alexandria, in the second year of Antoni nus Pius ; and in another, that he observ ed an eclipse of the moon in the ninth year of Adrian ; from which it is reason able to conclude, that this astronomer's observations upon the heavens were ma ny of them made between the year 125 and 140.
Ptolemy has always been reckoned the prince of astronomers among the an cients, and in his works has left us an en tire body of that science. He has pre served and transmitted to us the obser vations and principal discoveries of the ancients, and at the same time augment ed and enriched them with his own. He corrected Hipparchus's catalogue of the fixed stars ; and formed tables, by which the motions of the sun, moon, and planets might be calculated and regulated. He was, indeed, the first who collected the scattered and detached observations of the ancients, and digested them into a system, which he set Forth in his "MEyezAz sive Magna Constructio," di vided into thirteen books. He adopts and exhibits here the ancient system of the world, which placed the earth in the centre of the universe ; and this has been {'tom him, the Ptolemaic System, to distinguish it from those of Copernicus and Tycho Brahe.
About the year 827, this work was translated by the Arabians into their lan in which it was called " Almages tum, 'by order of one of their kings ; and from Arabic into Latin, about 1230, by the encouragement of the Emperor Fre deric H. There were also other versions
from the Arabic into Latin ; and a manu script of one done by Girardus Cremo nensis, who flourished about the middle of the fourteeth century, Fahricius says, is still extant in the library of All Souls College, in Oxford. The Greek text of this work began to be read in Europe in the fifteenth century, and was first pub lished by Simon at Basil, 1538, in folio, with the eleven books of Com mentaries by Theon, who flourished at Alexandria in the reign of the elder The odosius. In 1541, it was reprinted at Basil, with a Latin version by George Trapezond ; and again at the same place in 1551, with the addition of other works of Ptolemy, and Latin versions by Came rarius. We learn from Kepler, that this last edition was used by Tycho.
Of this principal work of the ancient astronomers, it may not be improper to give here a more particular account. In general it may be observed, that the work is founded upon the hypothesis of the earth's being at rest in the centre of the universe, and that the heavenly bodies, the stars and planets, all move round it in solid orbs, whose motions are all directed by one, which Ptolemy calls the primum mobile, or First Mover, of which he dis courses at large. But, to be more parti this great work is divided into thir teen books.
In the first book, Ptolemy shows the earth is in the centre of those orbs, and of the universe itself, as he under stood it ; he represents the earth as of a spherical figure, and but as a point in comparison of the rest of the heavenly bodies : he treats concerning the several circles of the earth, and their distances from the equator ; as also of the right and oblique ascension of the heavenly bodies in a right sphere.
In the second book he treats of the habitable parts of the earth ; of the ele vation of the pole in an oblique sphere, and the various angles which the several circles make with the horizon, according to the different latitude of places ; also of the phenomena of the heavenly bodies depending on the same.