Pto precious monuments of antiquity. lemy has not rendered less service to geography, in collecting all the known longitudes and latitudes of different places, and laying the foundation of the method of projections, for the construction of geographical charts. He composed a great treatise on optics, which has not been preserved, in which he explained the astronomical refractions: he likewise wrote treatises on the several sciences of chronology, music, gnomonics, and mechanics. So many labours, and on such a variety of subjects, manifest a very superior genius, and will ever obtain him a distinguished rank in the history of science. On the revival of astronomy, when his system gave way to that of nature, mankind avenged themselves on him for the despotism it had so long maintained; and they accused Ptolemy of having appropriated to himself the discoveries of his predecessors; but in his time, the works of Hipparchus, and of the astronomers of Alexandria, must have been sufficiently known, to have rendered excusable, his not distinguishing what belonged to them from his own discoveries. As to the long continuation of his errors, it must be attributed to the same causes which replunged Europe into darkness. The fame of Ptolemy has met with the same fate as that of Aristotle and Descartes. Their errors were no sooner recognized, than a blind admiration gave way to an unjust contempt, for even in science itself, the most useful revolutions are not always exempt from passion and prejudice. CHAP. III. Of the Astronomy of the Arabs, Chinese and Persians. THE progress of astronomy in the school of Alexandria terminated with the labours of Ptolemy. This school continued to exist for five centuries, but the successors of Ptolemy and Hipparchus contented themselves with commenting on their works without adding to their discoveries. With the exception of two eclipses, recorded by Theon, and some observations of Theon of Athens, the phenomena of the heavens continued unobserved during a period of more than six hundred years. Rome, once the seat of valour, glory, and learning, did nothing useful to science. The consideration that was always attached by the republic to eloquence and military talents, seduced the imagination to those pursuits and science, offering no advantage, was necessarily neglected in the midst of conquests undertaken by ambition, and of internal commotions in which liberty expired and yielded to the despotism of the emperors. The division of the empire, the necessary consequence of its vast extent, brought on its fall, and the light of science, extinguished by the barbarians, was only again revived among the Arabians. This people, exalted by fanaticism, after having extended its religion and its arms over a great part of the Earth, had no sooner reposed in peace, than it devoted itself to letters and science, It, however, was but a short time before that they destroyed their most beautiful ornament, by burning the famous library of Alexandria. In vain the philosopher Philoponus exerted himself for its preservation. If these books, replied Omar, are conformable to the alcoran, they are useless; if they are contrary to it, they are detestable. Thus perished this immense treasure of erudition and genius. Repentance and regret soon followed this barbarous execution, for the Arabians were not long before they perceived their irreparable loss, and that they had deprived themselves of the most precious fruits of their conquests. About the middle of the eighth century, the caliph Almansor gave great encouragement to astronomy, but among the Arabian princes who distinguished themselves for their love of the sciences, the most celebrated in history was Almamoun, of the family of the Abassides and son of the famous Aaron Rashid, so celebrated throughout Asia. Almamoun reigned in Bagdat in 814, having conquered the Greek emperor Michael III., he imposed on him, as one condition of peace, that he should have delivered to him the best books of Greece; the Almagest was among the number, he caused it to be translated into |
