ASTROLABE 315 ASTRONOMY applied to a bleeding wound they so contract the tissues as to stop the hem- orrhage. The contraction thus pro- duced is different from that effected by an ordinary stimulant, and from that caused by the administration of a tonic. ASTROLABE, in its etymological sense, any instrument for taking the altitude of a star or other heavenly body, a defi- nition which would include not merely the astrolabe, properly so called, but also the sextant, the quadrant, the equatorial, the altitude and the azimuth circle, the theodolite, or any similar instrument. A type of astrolabe was in use among astronomers at least from the early part of the 2d century A. D., if not even from the 2d or 3d century B. c. ASTROLOGY, originally a discourse concerning the stars; subsequently the true science of astronomy; now the pseudo science which pretends to fore- tell future events by studying the posi- tion of the stars, and ascertaining their alleged influence upon human destiny. Natural astrology professes to predict changes in the weather from studying the stars and judicial or judiciary as- trology to foretell events bearing on the destiny of individual human beings or the race of mankind generally. The Chinese, the Egyptians, the Chal- deans, the Romans, and most other an- cient nations, with the honorable excep- tion of the Greeks, became implicit be- lievers in astrology. It was partly the cause and partly the effect of the prev- alent worship of the heavenly bodies. The later Jews, the Arabs, with other Mohammedan races, and the Christians in medieval Europe, were all great cul- tivators of astrology. The ordinary method of procedure in the Middle Ages was to divide a globe or a planisphere into 12 portions by circles running from pole to pole, like those which now mark meridians of longitude. Each of the 12 spaces or intervals between these circles was called a "house" of heaven. The sun, the moon, and the stars all pass once in 24 hours through the por- tion of heavens represented by the 12 "houses"; nowhere, however, except at the equator, are the same stars uniform- ly together in the same house. Every house has one of the heavenly bodies ruling over it as its lord. The houses symbolize different ad- vantages or disadvantages. The first is the house of life; the second, of riches; the third, of brethren; the fourth, of parents; the fifth, of children; the sixth, of health; the seventh, of marriage; the eighth, of death; the ninth, of reli- gion; the tenth, of dignities; the elev- enth, of friends; and the twelfth, of enemies. The houses vary in strength, the first one, that containing the part of the heavens about to rise, being the most powerful of all; it is called the ascendant, while the point of the eclip- tic just rising is termed the horoscope. The important matter was to ascertain what house and star was in the ascend- ant at the moment of a person's birth, from which it was deemed possible to augur his fortune. Astrology still flour- ishes in Asia and Africa. ASTRONOMY, the science that treats of all the heavenly bodies, including the earth, as related to them. It is the old- est of the sciences, and the mother of those generally called exact mathema- tics, geodesy and physics. Astronomy may to-day be broadly di- vided into two branches, mathematical and physical, and these are almost sy- nonymous with two terms recently in- troduced, the old and the new asti'on- omy, as defined by the statement that the old tells us whei'e the heavenly bodies are, the new, what they are. The characteristic feature of the instruments and methods of the new versus the old astronomy is that the new deals with some special form of radiant energy, measuring or analyzing the vibrations transmitted throughout all space by means of the elastic medium called ether. Under the two broad divisions stated above, mathematical astronomy would include the following divisions, which are not, however, mutually exclusive: Spherical astronomy, which treats of angles and directions on the celestial sphere; practical astronomy, treating of the instruments, methods of observa- tion, and of calculation employed to get at the facts and data of astronomy; theoretical astronomy, which deals with the orbits, tables and ephemerides of the sun, moon, planets, and comets, includ- ing the effect of their mutual attrac- tions, and gravitational or mechanical astronomy, which treats of the forces (principally gravitation) at work in space and the motions resulting there- from. This last was formerly called physical astronomy, but the name has been monopolized by the new astronomy within the last few decades, and must now be reserved for it. This second branch, likewise called astronomical physics and astro-physics, attempts to answer the question of what the heav- enly bodies are, the nature and con- stitution of their interiors, surfaces, atmosphere, their temperatures and radi-
