18 HISTORY OF ASTRONOMICAL DISCOVERY. 



when a long train of camels entered the gates of Bagdad laden with volumes of imported 

 learning, the fruit of a treaty made with the emperor of the East which imposed upon 

 him the condition of furnishing copies of all the Greek authors. The medicine of Galen, 

 the metaphysics of Aristotle, and the astronomy of Ptolemy, thus came into the hands of 

 the caliph, and speedily appeared in the language of the caliphate. Arabian cultivation 

 commenced with the dynasty of the Abassides, or the middle of the eighth century. 

 Three princes in succession, Almansor, Alraschid, and Almamon, used every means in 

 their power to promote the growth of learning among their people, and the advantages sup- 

 plied by their fine climate were not lost upon the followers of the Prophet, when a taste for 

 astronomical science had been created ; for upon the same sites where the old Chaldeans, two 

 thousand years previously, had gazed with wonder upon the heavens, they entered upon a 

 course of observation, with all the ardour common to their impulsive character, guided by 

 the light of the Greek results. The work of Ptolemy was their text-book ; his system, 

 theirs : but instruments were constructed upon a larger scale ; his determinations were 

 subjected to a rigid examination ; and in many instances a more accurate conclusion was 

 obtained. The length of the tropical year was found within a few seconds of the truth. 

 A degree of the terrestrial meridian was measured in the Desert near Palmyra, to verify 

 the value obtained by Eratosthenes. The obliquity of the ecliptic was determined. The 

 great inequalities also of Jupiter and Saturn are marked in the tables of planetary motions 

 constructed by the Arab astronomers. Their observations, in general, of the celestial 

 bodies have a greater degree of accuracy than those of the Greeks, on account of the 

 necessary correction being made for the phenomena of refraction, which was observed with 

 reference to bodies near the horizon. Bagdad, however, was only the centre of a move- 

 ment in favour of science. The impulse extended as wide as the language and profession 

 of Islam, to Egypt, Morocco, and Spain ; and it long survived after the political power of 

 the Eastern caliphs, which had gleamed like a meteor, had as suddenly vanished. An 

 observatory was erected in the northern part of Persia, by a descendant of Gengis-Khan ; 

 and Ulugh Beg, a prince of the house of Timour, erected one at Samarcand, where he 

 compiled his now extant catalogue of the stars. The preface to this work states that 

 eight stars marked in the catalogue of Ptolemy could not then be found in the heavens. 

 This may have arisen simply from a mistaken entry in the first instance ; but, if a case of 

 real disappearance, it is far from being the only one, though a profound mystery. 



Arabian cultivation attained its meridian splendour in Spain at a period when the rest 

 of Europe was plunged in darkness. Through intercourse with the Moors of that country, 

 some gleams of light gradually radiated through the Continent ; and undoubtedly they are 

 to be regarded as having transmitted the torch of civilisation from antiquity to modern 

 ages. Among the first fruits of their influence, the construction of the Alphonsine tables 

 may be placed, a work of the king of Castile of that name, chiefly confined to a more 

 accurate determination of the motions of the sun and planets, and the length of the year, 

 the materials for which were derived from his Mahornmedan neighbours to 'the south. 

 There is little to detain us of any interest or importance in relation to astronomy, at this 

 era, in countries where it has now arrived at such marvellous perfection. Observers 

 abounded in the middle ages ; but their midnight watchings of the great canopy of heaven 

 had very generally only an astrological purpose in view. Speculatists were numerous 

 respecting the mechanism of the universe ; but blindly adhering to the doctrines of the 

 earth's immobility, and of the uniform and circular motions of the celestial lights, they 

 laboured hard, but in vain, to adjust observed phenomena with preconceived theory. The 

 Aristotelian notion of thq spheres was revived in all its grossness, and huge materialities 

 were conceived to constitute the eternal paths of the bodies composing the solar system, 

 necessary to the end of keeping them in place. To account for all the celestial move- 



