Ixviii NOTES. 



hydraulic clock with wheel-work (tympana qiue nonnulli rotas appellant, 

 Grseci autem vfpirpoxa, Vitruvius, x. 4). Leibnitz (Annales Imperil Occi- 

 dents Brunsvicensis, ed. Pertz, T. i. 1843, p. 24?) expresses his admiration 

 of the construction of the clock of Haroun Al-Raschid (Abd-Allatif, trad, par 

 Silvestre de Sacy, p. 578). A much more remarkable piece of skilful work 

 was that which the Sultan sent from Egypt, in 1232, to the Emperor 

 Frederic II. It was a large teut, in which the sun and moon were made to 

 move by mechanism, so as to rise and set, and to shew the hours of the day 

 and of the night at correct intervals of time. In the Annales Godefridi 

 Monachi S. Pantaleonis apud Coloniam Agrippiuam, it is described as " ten- 

 torium, in quo imagines solis et lurise artificialiter motse cursum suum certis 

 et debitis spaciis peragrant, et horas diei et noctis infallibilitcr indicant 

 (Freheri Rerum Germanicarura Scriptores, T. i. Argcntor. 1717, p. 398). 

 The monk Godefridus, or whoever else may have treated of those years in the 

 chronicle which was, perhaps, written by many different authors for the con- 

 vent of St. Pantaleon at Cologne (see Bohmer, Fontes Rerum Germanicarum, 

 Bd. ii. 1845, S. xxxiv. xxxvii.), lived in the time of the great Emperor 

 Frederic II. himself. The emperor had this curious work, the value of which 

 was estimated at 20000 marks, preserved at Venusium, with other treasures 

 (Fried, von Raumer, Gesch. der Hohenstaufen, Bd. iii. S. 430). That the 

 whole tent was given a movement like., that of the vault of heaven, as has 

 often been asserted, appears to me very improbable. The Chronica Monas- 

 terii Hirsaugiensis, edited by Trithemius, contains scarcely any thing more 

 than a mere repetition of the passage in the Annales Godefridi, without giving 

 any information about the mechanical construction (Joh. Trithemii Opera 

 Historica, P. ii. Francof. 1601, p. 180). Reinaud says that the movement 

 was effected "par des ressorts caches" (Extraits des Historiens Arabes relatifs 

 aux Guerres des Croisades, 1829, p. 435). 



C 350 ) p. 223. On the Indian tables which Alphazari and Alkoresmi translated 

 into Arabic, see Chasles, Recherehes sur 1'Astronomie indienne, in the Comptes 

 rendus des Se'ances de 1'Acad. des Sciences, T. xxiii. 1846, p. 846850. 

 The substitution of the sine for the arc, which is usually ascribed to Albateg- 

 nius, in the beginning of the tenth century, also belongs originally to the 

 Indians : tables of sines are to be found in the Surya-Siddhanta. 



p 1 ) p. 223. Reinaud, Fragments Arabes relatifs a 1'Iude, p. xii. xvii. 

 96126, and especially 135 160. Albiruni's proper name was Abul-Ryhan. 

 He was a native of Byrun in the valley of the Indus, was a friend of 

 Aviceuna, and lived with him at the Arabian academy which had been formed 



