220 COSMOS. 



Although the purity and rarely-disturbed transparency of 

 tho sky of Arabia must have especially directed the attention 



Arts, 1807, vol. i., p. 191) does not either doubt that Ebn-Junis, at the 

 ond of the tenth century, applied the pendulum to the measurement of 

 time, but he ascribes the first combination of the pendulum with wheel 

 work to Sanctorius, in 1612, therefore forty-four years before Huygens. 

 With reference to the very elaborately constructed clock included in 

 the presents which Haroun Al-Raschid, or, rather, the Calif Abdallah, 

 sent, two hunlred years earlier, from Persia to Charlemagne at Aix-la- 

 Chapelle, Egiuhard distinctly says that it was moved by water (Horo- 

 fogium ex aurichalco arte mechanica mirifice compositum, in quo duo- 

 decim horarum cursus ad clepsidram vertebatur) ; Einhardi Annates, 

 in Pertz's Monumenta Germanice Historica, Scriptorum,t. i., 1826, p. 

 195. Compare H. Mutius, De Germanorum Origine, Gestis, &c. 

 Chronic, lib. viii., p. 57, in Pistorii Germanicorum Scriptorum, I. ii., 

 Francof., 1584 ; Bouquet, Recueil des Historiens des Gaules, t, v., p. 

 333 and 354. The hours were indicated by the sound of the fall of 

 gmall balls, and by the coming forth of small horsemen from as many 

 opening doors. The manner in which the water acted in such clocks 

 may indeed have been very different among the Chaldeans, who 

 " weighed time" (determining it by the weight of fluids), and in the 

 clepsydras of the Greeks and the Indians ; for the hydraulic clock-work 

 of Ctesibius, under Ptolemy Euergetes IL, which marked the (civil) 

 hours throughout the year at Alexandria, was never known, according 

 to Ideler, under the common denomination of KXetpvSpa. (Ideler's 

 Handbuch der Chronologic, 1825, bd. i., s. 231.) According to the de- 

 scription of Vitruvius (lib. ix., cap. 4), it was an actual astronomical 

 clock, a " horologium ex aqua," a very complicated " raachina hydrau- 

 lica," working by toothed wheels (versatilis tympani denticuli sequales 

 alius alium impellentes). It is therefore not improbable that the Arabs, 

 who were acquainted with the improved mechanical constructions in 

 use under the Roman empire, may have succeeded in constructing an 

 hydraulic clock with wheel-work (tympana quae nonnulli rotas appel- 

 lant, Graeci autam ireplToxa. Vitruvius, x., 4). Leibnitz {Annates Im.' 

 perii Occidentis Brunsvicenses, ed. Pertz, t. i., 1843, p. 247) expresses 

 his admiration of the construction of the clock of Haroun Al-Raschid 

 {Abd-Allatif, trad, par Silvestre de Sacy, p. 578). The piece of mech- 

 anism which the sultan sent from Egypt, in 1232, to the Emperor Fred 

 eric II., seems, howevQr, to have been much more remarkable. It was 

 a large tent, in which the sun and moon were moved by mechanism, 

 and made to rise and set, and show the hours of the day and night at 

 correct intervals of time. In the Annates Godefridi Monachi S. Panta- 

 leonis apvd Coloniam Agrippinam, it is said to have been a " tentorium, 

 in quo imagines solis et lunae artificialiter motae cursum suum certis et 

 debitis spaciis peragrant, et boras diei et noctis infallibiliter indicant." 

 {Freheri Rernm Germanicarum Scriptores, t. i., Argentor., 1717, p. 398.) 

 The monk Godefridus, or whoever else may have written the annals 

 of those years in the chronicle composed for the convent of St. Panta 

 leon at Cologne, which was probably the work of many different authors 

 (see Bdhmer, Pontes Rerum Germanicarum, bd. ii., 1845, s. xxxiv.- 

 xxxvii.), lived in the time of the great Emperor Frederic II. himself. 

 The emperor caused this curious work, the value of which was esti- 

 mated at 20,000 marks, to be preserved at Venusium, with other treas- 

 ures. (Fried, von Raumer, Gesch. der Hohenstaufen, bd. iii., * 430.) 



