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| Fig. 1.—PERSIAN ASTROLABE (c. 1712) INSCRIBED IN ARABIC. | |
| Front, showing the Rete or Spider, a network of starpointers. Beneath the Rete, in a hollow, are four thin brassdiscs, called Tables or Climates, engraved with projections of thesphere for different latitudes. | Back, showing graduations, parallelogram for measuring heights;and other tables, together with the Rule with sights (A)held by a moveable pin (B), known as the Horse or Wedge. |
Fig. 2.—Principle of the Astrolabe. If a solid circle be fixed in any one position and a tube be pivoted on its centre so as to move; and if the line C D be drawn upon the circle pointing towards any object Q in the heavens which lies in the plane of the circle, by turning the tube A B towards any other object P in the plane of the circle, the angle BOD will be the angle subtended by the two objects P and Q at the eye. |
| From Exercises, by T. Blundeville. |
| Fig. 3.—Mariner’s Astrolabe, A.D. 1594. Made of brass, or of heavy wood: it varied in size from a few inches to 1 ft. in diameter. |
The two forms of the planispheric astrolabe most widely known and used in the 15th, 16th and even 17th centuries were: (1) the portable astrolabe shown in fig. 1 (Plate). This originated in the East, and was in early use in India, Persia and Arabia, and was introduced into Europe by the Arabs, who had perfected it—perhaps as early as A.D. 700. It combines the planisphere and armillae of Hipparchus and others, and the theodolite of Theon, and was usually of brass, varying in diameter from a couple of inches to a foot or more. It was used for taking the altitudes of sun, moon and stars; for calculating latitude; for determining the points of the compass, and time; for ascertaining heights of mountains, &c.; and for construction of horoscopes. The instrument was a marvel of convenience and ingenuity, and was called “the mathematical jewel.” Nevertheless it passed out of use, because incapable of any great precision.
(2) The mariner’s astrolabe, fig. 3, was adapted from that of astronomers by Martin Behaim, c. 1480. This was the instrument used by Columbus. With the tables of the sun’s declination then available, he could calculate his latitude by meridian altitudes of the sun taken with his astrolabe. The mariner’s astrolabe was superseded by John Hadley’s quadrant of 1731.
Authorities.—Chaucer, Treatise on the Astrolabe (Skeat’s edition of Chaucer); J.J. Stöffler, Elucidatio Fabrice ususque Astrolabii, &c.; Thomas Blundeville, His Exercises (1594); F. Ritter, Astrolabium; W.H. Morley, Description of Astrolabe of Shah Husain; M.L. Huggins, “The Astrolabe” (Astrophysical Journal, 1894); Penny Cyclopaedia, article “Astrolabe;” R. Grant, History of Physical Astronomy.
(M. L. H.)
ASTROLOGY, the ancient art or science of divining the fate and future of human beings from indications given by the positions of the stars (sun, moon and planets). The belief in a connexion between the heavenly bodies and the life of man has played an important part in human history. For long ages astronomy and astrology (which might be called astromancy, on the same principle as “chiromancy”) were identified; and a distinction is made between “natural astrology,” which predicts the motions of the heavenly bodies, eclipses, &c., and “judicial astrology,” which studies the influence of the stars on human destiny. Isidore of Seville (d. 636) is one of the first to distinguish between astronomy and astrology; nor did astronomy begin to rid itself of astrology till the 16th century, when, with the system of Copernicus, the conviction that the earth itself is one of the heavenly bodies was finally established. The study of astromancy and the belief in it, as part of astronomy, is found in a developed form among the ancient Babylonians, and directly or indirectly through the Babylonians spread to other nations. It came to Greece about the middle of the 4th century B.C., and reached Rome before the opening of the Christian era. In India and China astronomy and astrology are largely reflections of Greek theories and speculations; and similarly with the introduction of Greek culture into Egypt, both astronomy and astrology were actively cultivated in the region of the Nile during the Hellenistic and Roman periods. Astrology was further developed by the Arabs from the 7th to the 13th century, and in the Europe of the 14th and 15th centuries astrologers were dominating influences at court.
Even up to the present day men of intellectual eminence like Dr Richard Garnett have convinced themselves that astromancy has a foundation of truth, just as there are still believers in chiromancy or other forms of divination. Dr Garnett (“A.G. Trent”) insisted indeed that it was a mistake to confuse astrology with fortune-telling, and maintained that it was a “physical science just as much as geology,” depending like them on ascertained facts, and grossly misrepresented by being connected with magic. Dr Garnett himself looked upon the study of biography in relation to the casting of horoscopes as an empirical investigation, but it is difficult in practice to keep the distinction clear, to judge by present-day text-books such as those of Dr Wilde (Primer of Astrology, &c.). Dr Wilde insists on there being “nothing incongruous with the laws of nature in the theory that the sun, moon and stars influence men’s physical bodies and conditions, seeing that man is made up of a physical part of the earth.” There is an obvious tendency, however, for astromancy to be employed, like palmistry, as a means of imposing on the ignorant and credulous. How far the more serious claim is likely to be revived in connexion with the renewal of research into the “occult” sciences generally, it is still too early to speculate; and it has to be recognized that such a point of view is opposed to the generally established belief that astrology is either mere superstition or absolute imposture, and that its former vogue was due either to deception or to the tyranny of an unscientific environment. But if the progress of physical science has not prevented the rehabilitation of much of ancient alchemy by the later researches into chemical change, and if psychology now finds a place for explanations of spiritualism and witchcraft which involve the admission of the empirical facts under a new theory (as in the case of the divining-rod, &c.), it is at least conceivable that some new synthesis might once more justify part at all events of ancient and medieval astromancy, to the extent of admitting the empirical facts where provable, and substituting for the supposed influence of the stars as such, some deeper theory which would be consistent with an application to other forms of prophecy, and thus might reconcile the possibility of dipping into futurity with certain interrelations of the universe, different indeed from those assumed by astrological theory, but underlying and explaining it. If this is ever accomplished it will need the patient investigation of a number of empirical observations by competent students unbiassed by any parti pris—a difficult set of conditions to obtain; and even then no definite results may be achieved.