History of the Intellectual Development of Europe, Volume I (of 2) / Revised Edition

by John William Draper

It was thus in Alexandria, under the Ptolemies, that modern astronomy arose. Ptolemy Soter, the founder of this line of kings, was not only a patron of science, but likewise an author. He composed a history of the campaigns of Alexander. Under him the collection of the library was commenced, probably soon after the defeat of Antigonus at the battle of Ipsus, B.C. 301. The museum is due to his son Ptolemy Philadelphus, who not only patronized learning in his own dominions, but likewise endeavoured to extend the boundaries of human knowledge in other quarters. Thus he sent an expedition under his admiral Timosthenes as far as Madagascar. Of the succeeding Ptolemies, Euergetes and Philopator were both very able men, though the later was a bad one; he murdered his father, and perpetrated many horrors in Alexandria. Epiphanes, succeeding his father when only five years old, was placed by his guardians under the protection of Rome, thus furnishing to the ambitious republic a pretence for interfering in the affairs of Egypt. The same policy was continued during the reign of his son Philometor, who, upon the whole, was an able and good king. Even Physcon, who succeeded in B.C. 146, and who is described as sensual, corpulent, and cruel—cruel, for he cut off the head, hands, and feet of his son, and sent them to Cleopatra his wife—could not resist the inspirations to which the policy of his ancestors, continued for nearly two centuries, had given birth, but was an effective promoter of literature and the arts, and himself the author of an historical work. A like inclination was displayed by his successors, Lathyrus and Auletes, the name of the latter indicating his proficiency in music. The surnames under which all these Ptolemies pass were nicknames, or titles of derision imposed upon them by their giddy and satirical Alexandrian subjects. The political state of Alexandria was significantly said to be a tyranny tempered by ridicule. The dynasty ended in the person of the celebrated Cleopatra, who, after the battle of Actium, caused herself, as is related in the legends, to be bitten by an asp. She took poison that she might not fall captive to Octavianus, and be led in his triumph through the streets of Rome.

If we possessed a complete and unbiased history of these Greek kings, it would doubtless uphold their title to be regarded as the most illustrious of all ancient sovereigns. Even after their political power had passed into the hands of the Romans—a nation who had no regard to truth and to right—and philosophy, in its old age, had become extinguished or eclipsed by the faith of the later Cæsars, enforced by an unscrupulous use of their power, so strong was the vitality of the intellectual germ they had fostered, that, though compelled to lie dormant for centuries, it shot up vigorously on the first occasion that favouring circumstances allowed.

They patronize literature as well as science.

This Egyptian dynasty extended its protection and patronage to literature as well as to science. Thus Philadelphus did not consider it beneath him to count among his personal friends the poet Callimachus, who had written a treatise on birds, and honourably maintained himself by keeping a school in Alexandria. The court of that sovereign was, moreover, adorned by a constellation of seven poets, to which the gay Alexandrians gave the nickname of the Pleiades. They are said to have been Lycophron, Theocritus, Callimachus, Aratus, Apollonius Rhodius, Nicander, and Homer the son of Macro. Among them may be distinguished Lycophron, whose work, entitled Cassandra, still remains; and Theocritus, whose exquisite bucolics prove how sweet a poet he was.

The writings of Apollonius.

To return to the scientific movement. The school of Euclid was worthily represented in the time of Euergetes by Apollonius Pergæus, forty years later than Archimedes. He excelled both in the mathematical and physical department. His chief work was a treatise on Conic Sections. It is said that he was the first to introduce the words ellipse and hyperbola. So late as the eleventh century his complete works were extant in Arabic. Modern geometers describe him as handling his subjects with less power than his great predecessor Archimedes, but nevertheless displaying extreme precision and beauty in his methods. His fifth book, on Maxima and Minima, is to be regarded as one of the highest efforts of Greek geometry. As an example of his physical inquiries may be mentioned his invention of a clock.

The writings of Hipparchus.

Fifty years after Apollonius, B.C. 160-125, we meet with the great astronomer Hipparchus. He does not appear to have made observations himself in Alexandria, but he uses those of Aristyllus and Timochares of that place. Indeed, his great discovery of the precession of the equinoxes was essentially founded on the discussion of the Alexandrian observations on Spica Virginis made by Timochares. In pure mathematics he gave methods for solving all triangles plane and spherical: he also constructed a table of chords. In astronomy, besides his capital discovery of the precession of the equinoxes just mentioned, he also determined the first inequality of the moon, the equation of the centre, and all but anticipated Ptolemy in the discovery of the evection. To him also must be attributed the establishment of the theory of The theory of epicycles and eccentrics. epicycles and eccentrics, a geometrical conception for the purpose of resolving the apparent motions of the heavenly bodies, on the principle of circular movement. In the case of the sun and moon, Hipparchus succeeded in the application of that theory, and indicated that it might be adapted to the planets. Though never intended as a representation of the actual motions of the heavenly bodies, it maintained its ground until the era of Kepler and Newton, when the heliocentric doctrine, and that of elliptic motions, were incontestably established. Even Newton himself, in the 37th proposition of the third book of the "Principia," availed himself of its aid. Hipparchus also undertook to make a register of the stars by the method of alineations—that is, by indicating those which were in the same apparent straight line. The number of stars catalogued by him was 1,080. If he thus depicted the aspect of the sky for his times, he also endeavoured to do the same for the surface of the earth by marking the position of towns and other places by lines of latitude and longitude.

The writings of Ptolemy.

Subsequently to Hipparchus, we find the astronomers Geminus and Cleomedes; their fame, however, is totally eclipsed by that of Ptolemy, A.D. 138, the author of the great work "Syntaxis," or the mathematical construction of the heavens—a work fully deserving the epithet which has been bestowed upon it, "a noble exposition of the mathematical theory of epicycles and eccentrics." It was translated by the Arabians after the Mohammedan conquest of Egypt; and, under the title of Almagest, was received by them as the highest authority on the mechanism and phenomena of the universe. It maintained its ground in Europe in the same eminent position for nearly fifteen hundred years, justifying the His great work: the mechanical construction of the heavens. encomium of Synesius on the institution which gave it birth, "the divine school of Alexandria." The Almagest commences with the doctrine that the earth is globular and fixed in space; it describes the construction of a table of chords and instruments for observing the solstices, and deduces the obliquity of the ecliptic. It finds terrestrial latitudes by the gnomon; describes climates; shows how ordinary may be converted into sidereal time; gives reasons for preferring the tropical to the sidereal year; furnishes the solar theory on the principle of the sun's orbit being a simple eccentric; explains the equation of time; advances to the discussion of the motions of the moon; treats of the first inequality, of her eclipses, and the motion of the node. It then gives Ptolemy's own great discovery—that which has made his name immortal—the discovery of the moon's evection or second inequality, reducing it to the epicyclic theory. It attempts the determination of the distances of the sun and moon from the earth, with, however, only partial success, since it makes the sun's distance but one-twentieth of the real amount. It considers the precession of the equinoxes, the discovery of Hipparchus, the full period for which is twenty-five thousand years. It gives a catalogue of 1,022 stars; treats of the nature of the Milky Way; and discusses, in the most masterly manner, the motions of the planets. This point constitutes Ptolemy's second claim to scientific fame. His determination of the planetary orbits was accomplished by comparing his own observations with those of former astronomers, especially with those of Timochares on Venus.