[Illustration: The Egyptian Gnomon. _From pen drawing_] Chapter III Globes Constructed by the Arabs Followers of Ptolemy.—Early armillary spheres.—Interest of the Califs in globes and astronomical instruments.—The record of the ‘Fihrist.’—Ibrahim.—Caissar.—Mohammed ben Helal.—Mohammed el Ordhi.—The Paris globes.—Ridhwan Efendi. In passing from the period of classical antiquity to the so-called Christian middle ages, attention may first be directed to the activities of the Arabs in the field of astronomy and geography, in so far as their activities had to do with the construction of globes.[49] The information which we have, concerning their astronomical studies in particular, is more detailed than is that which has come down to us respecting any other peoples who may have been interested in these centuries in the same field of study. Doubt may be expressed at the outset that the Arabs were interested in the construction of terrestrial globes, since with the matter of descriptive geography they appear to have been very little concerned, a fact which their imperfect cartographical attempts clearly demonstrate.[50] Although the theory of a globular earth was early accepted by their learned men,[51] there is scarcely a trustworthy allusion in literature to Arabic terrestrial globes which can be cited. An occasional reference, however, has been made by modern writers to a globe said to have been constructed for King Roger of Sicily. Without citing his authority, Freyheer F. v. Zach states that “the oldest terrestrial globe which is known was made for King Roger II of Sicily in the twelfth century, and is especially remarkable for the value of the metal which was used in its construction, this being 400 pounds of silver. A knowledge of this globe would not have come down to our day had not Edrisi, a famous geographer of that time, given an especial description of the same, under the title Nothatol mostak (Pleasure of the Soul).”[52] It is probable that the reference here is to a circular disc made by Edrisi, or an armillary sphere, but not to a terrestrial globe.[53] As to Arabic celestial globes, a different situation presents itself. It is well known that the inhabitants of Arabia, long before the time of Islam, were in the habit of observing the stars, many of which, as Dorn has noted, they knew and designated by names taken from pastoral life, and several of which they worshiped as visible gods.[54]