Читать книгу Terrestrial & Celestial Globes - Edward Luther Stevenson - Страница 10

Table of Contents

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

Calif al-Mansur, who began his reign in 754 AD, appears to have been the first to show a decided taste for astronomical science, and for many centuries following him this interest is strikingly pronounced among the people of his country.55 Scholars were eagerly attracted to the works of Ptolemy, which were many times translated into Arabic, and commentaries were written upon his description of the names and figures of the several constellations. The only alteration they allowed themselves to make in the names of the stars was to translate them into their own language, or to substitute for those they could not understand other names that conveyed an idea to their minds, applicable to the constellation before the eyes. Andromeda they called “The Chained Lady”; Cassiopeia they called “The Lady in the Chair”; Orion received the name “The Giant.” They followed in the construction of their armillary spheres and celestial globes the description laid down in Ptolemy’s ‘Syntaxis,’ modifying these astronomical instruments, from time to time, as their studies directed them.56

The list of califs interested in astronomy is a long one, both of those who remained in the original homeland, and of those who went to the new home in the Iberian Peninsula.57 The Mohammedan Hulagu Khan, for example, erected, about 1264, an observatory in his Mongol capital, Maragha, near Tabriz, which long remained a noted center for astronomical studies.58 This observatory, however, was but one of a number of similar institutions erected either by the Arabs or by the Persians. We are told that the construction of astronomical instruments was brought to a high degree of perfection by these peoples in the thirteenth century.59 The names of many of the Arabic astronomers who were particularly expert as globe makers are recorded, and there were many who wrote on the subject of celestial spheres, armillary spheres, and astrolabes, even before the tenth century.60 The author of the ‘Fihrist,’ Ibn Abî Ja’kûb an-Nadîm, tells us that Kurra ben Kamîtâ al-Harrânî constructed a globe which he himself had seen.61 This, he says, was made of unbleached material from Dabik, and colored, but that the colors were much faded. Ibn Alnabdi, who was known as a clever mechanic, mentions two globes which he had examined and admired for their excellency of execution, in the public library of Kahira, in the year 1043. One of these globes, he says, was made of brass, by Ptolemy himself; the other, of silver, was constructed by Abul Hassan Alsufi, for the immediate use of the king, Adad Eddoula.62

As a visible evidence of the interest of the Arabs in astronomical science, and of their skill in the construction of astronomical instruments, we have preserved to us, besides numerous astrolabes, no less than seven globes, known to have been constructed prior to the year 1600. The oldest one extant is now in the possession of the R. Istituto di Studi Superiori of Florence, Italy.63 This fine example of the skill which was attained by the instrument makers of Valencia, Spain, at one time a flourishing center of Arabic culture, appears to date from the second half of the eleventh century. According to an inscription on the globe, we learn that it was made at Valencia by Ibrahim Ibn Said-as-Sahli, in the year 473 of the Hegira, a date equivalent to 1080 AD This date Professor Meucci finds confirmed by a careful study of the position of the stars represented on the globe. He notes, for example, that the star Regulus had been placed at a distance of 16 degrees 40 minutes from the sign of Leo. Ptolemy, in the year 140 AD, gave this distance as 2 degrees 30 minutes. According to Albaregnius, this star advances about one degree every sixty-six years. Since 140 A.D. the star, therefore, would have moved 14 degrees 10 minutes, which fact would lead astronomers to place this star, about 1080, as it appears on the globe. The globe is of brass, 20 cm. in diameter, having engraved on its surface forty-seven constellations, as given by Ptolemy, omitting only the Cup, with 1042 stars, each with its respective magnitude indicated.

A second Arabic celestial globe, which dates from the year 1225, has been described in detail in a monograph by Assemani, which he issued in the year 1790.64 This remarkably interesting object belonged, at the time, to the extensive and celebrated collection of antiquities and curiosities of Cardinal Borgia, in Velletri, but may now be found in the Museo Nazionale of Naples. It is composed of two brass hemispheres, having both horizon and meridian circles, the whole resting upon four supporting feet. A Cufic inscription tells us that it was made by Caissar ben Abul Casem ben Mosafer Alabiaki Alhanefi, in the year of the Hegira 622. Caissar probably was an astronomer at the court of Cairo, and the Mohammedan date as given, translated into Christian reckoning, gives us the year 1225.

In the year 1829 Dorn published a detailed description of an Arabic globe which had been deposited in the museum of the Asiatic Society of London (Fig. 13) by Sir John Malcolm.65 It is of brass, has a diameter of 24 cm., and is furnished with a substantial mounting. The peculiar features of the figures which represent the several constellations suggest Persian workmanship. In the vicinity of the south pole is an inscription in Cufic characters, telling us that it was “Made by the most humble in the supreme god, Mohammed ben Helal, the astronomer of Monsul, in the year of the Hegira 674.” This year answers to the year 1275 of the Christian era, that is, it was constructed about the same time as the Borgian globe and that belonging to the Dresden collection, briefly described below. Forty-seven constellations are represented. On the horizon circle, in their respective places, we find engraved the words, “East,” “West,” “South,” “North.”

Fig. 13. Northern Hemisphere of Globe by Mohammed ben Helal, 1275.

The Arabic globe, to be found in the Mathematical Salon of Dresden (Fig. 14), has proved to be one of much interest and scientific value to students of astronomy.66 Bode, who described it in the year 1808, refers to its remarkably fine execution and to its Cufic inscriptions as being among the finest extant specimens of early Arabic writing. The sphere is of brass, having a diameter of 14 cm., and is composed of two parts, separable on the line of the ecliptic. It has a brass horizon circle, on which is engraved at the east the word “rising,” and at the west the word “setting.” It is not supplied with a movable meridian circle, but within the horizon circle, from north to south, and from east to west, there are two brass half circles, of the same diameter as the horizon circle and so adjusted as to form one piece with it. Through such an arrangement it is made possible to turn the globe in any desired direction, one half of it being at all times above the horizon. In addition to the above arrangement, there are two movable half circles, attached at the zenith point by a pivot. These half circles are graduated, and are movable, making it possible to find, by means of them, the declination and right ascension of any star. The base, which must be comparatively modern, consists of a circular plate, from which rise four turned support columns, attached at their upper extremities to the two half circles of brass, on which rests the horizon circle.

Fig. 14. Globe of Mohammed ben Muwajed el Ordhi, 1279.

The date of construction cannot be far from 1279, which is determinable from the position of the stars engraved thereon, relative, for example, to the equinoctial points. The maker’s name, “Mohammed ben Muwajed el Ordhi,” appears near the constellation Ursa Major, and is inlaid in silver. There appear, very artistically engraved, the lines representing the principal circles, the outlines of the several constellations, with their names, some of these being inlaid with silver, some with gold. The equator and the ecliptic are represented on the surface of the sphere, each by two engraved parallel lines, and are graduated, the graduation in each instance being represented by four short and one long line, alternating thus by fives throughout the entire three hundred and sixty degrees. The equator is inlaid with gold, the other circles with silver. The names of the twelve constellations in the zodiac are alternately inlaid with gold and silver, while all star names, except as indicated, are inlaid with silver. The constellations represented number forty-eight, the human figures all being clad, turning the front and right face toward the observer.

The Bibliothèque Nationale of Paris possesses two ancient Arabic globes, one of which, neither signed nor dated, has been thought to have been constructed in the eleventh century.67 This was obtained by Jomard, in Egypt, more than sixty years ago. It has a diameter of about 19 cm., is furnished with a horizon circle, which is upheld by four semicircular arms, these, in turn, resting upon a base composed of four flat and rather inartistic supports. The engraving on the surface of the brass sphere closely resembles that on the Dresden globe. A detailed description of this globe has not been obtainable.

A second Paris Arabic globe,68 like the preceding, belongs to the Bibliothèque Nationale (Fig. 15). It has a diameter of something less than 15 cm., and was constructed by Diemat Eddin Mohammed, in the year of the Hegira 981, which in the Christian reckoning corresponds to the year 1573.

Fig. 15. Globe of Diemat Eddin Mohammed, 1573.

The Imperial Library of Petrograd possesses an Arabic globe, constructed in the year 1701.69 It is described by Dorn as a fine example of the globe maker’s art, closely resembling, in its general features, the Arabic globe in the collection of the Royal Asiatic Society of London. It has a diameter of about 19 cm., rests upon an ornamental tripod base, and is adjusted to turn within a brass circle, which circle is fitted into a larger one, so marked and graduated as to represent four concentric circles. The first or inner circle, representing the horizon, is divided into thirty-six divisions of ten degrees each; on the second circle the degrees are indicated by letters; on the third circle appear the twelve signs of the zodiac and the four principal directions, east, west, north, south; the fourth circle is divided into thirty-six parts, formed by the extension of the lines which divide the first, or horizon circle, into thirty-six parts. On the last circle the names of one hundred and four cities and countries are given. Not far from the north pole is an inscription which gives us the name of the maker and the date of construction. Therein we read that it was completed in the year 1113 of the flight of the Prophet, or in the year 1701 of Christian reckoning, by Ridhwan, for Maulana Hassan Efendi, who, toward the end of the seventeenth century, was director of the astronomical observatory of Cairo, and gave substantial encouragement to makers of globes and of other instruments employed in astronomical studies. The equator, the ecliptic, and the parallels are represented, the first two by parallel circles which are crossed or joined by lines dividing them into seventy-two principal parts, each part being again subdivided into fifths. The close resemblance of this example to the earlier known Arabic globes suggests that there was little, if any, progress among those peoples in the art of globe construction since the eleventh century.

Fig. 15a. Anonymous Arabic Globe, 1635.