COSMOS, VOL. II - World eBook Library

THE AEABS. 591
before Berthold Scliwarz, a species of gunpowder was used to
blast the rock in the Ilammelsberg, in the Harz mountains.
The invention of an air thermometer is also ascribed to
Avicenna from a notice by Sanctorius, but this notice is very
obscure, and six centuries passed before Galileo, Cornelius
Drebbel, and the Academia del Cimento, by the establishment
of an exact measurer of heat, created an important means for
and com-
penetrating into a world of unknown phenomena,
prehending the cosmical connection of effects in the atmosphere,
the superimposed strata of the ocean, and the interior of the
earth; thus revealing phenomena whose regularity and
periodicity excite our astonishment. Among the advances
which science owes to the Arabs, it will be sufficient to
mention Alhazen's work on refraction, partly borrowed,
perhaps, from Ptolemy's Optics, and the knowledge and first
application of the pendulum as a means of measuring time,
due to the great astronomer, Ebn-Junis.*
*
Laplace, Precis del"Hist, de VAstronomic, 1821, p. 60; and Am. Sedil-
Memoire sur les Instrumens astr. des Ardbes, 1841, p. 44. Thomas
Young (Lectures on Natural Philosophy and the Mechanical Arts,
1807, vol. i. p. 191) does not either doubt that Ebn-Junis, at the end of
the tenth century, applied the pendulum to the measurement of time, but
lie 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-Iiaschid, or rather the Caliph Abdallah, sent,
two hundred years earlier, from Persia to Charlemagne at Aix-la-
Chapelle, Eginhard distinctly says, that it was moved by water, (Horologium
ex aurichalco arte mechanica mirifice compositum, in quo duodecim
horarum cursus ad clepsidram vertebatur); Einhardi Annales,
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 G&rmanicorum scriptorum, t. ii.
Francof. 1584; Bouquet, Recueil des Historians des Gaules, t. v. pp.
333 and 354. The hours were indicated by the sound of the fall of small
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 clockwork of Ctesibius, under
Ptolemy Euergetes II., which marked the (civil) hours throughout the
year at Alexandria, was never known, according to Ideler, under the
common denomination of K\e;}/vdpa. (Idelev's Handbuch derChronoiogie,
1825, bd. i. s. 231.) According to the description of Vitruvius Oib. ix.