Page:The New International Encyclopædia 1st ed. v. 13.djvu/868

* MOON. 778 MOONCALF. in coiirse of time passes over or ocenlts cverj- star situated within 5° 24' of the eeliptic. The motion of tlic nodes is so rapid that they perform a complete circuit of the orbit in 18. ti years. Another important chanjje in the moon's orbit is the revolution of the line of apsides (q.v. ), by which the perigee and apogee are continually changing their position relative to the earth and sun. This revolution is more than twice as rapid as that of the nodes, being performed in 8.85 solar years. This motion is analogous to the perturbations of planetary orbits, and its nature and origin are treated in the article Perturba- tions. Its efTect upon the moon is to produce a variation in her distance from the earth, inde- pen<U'nt of that produced by licr elliptic motion. Among the further disturbances or perturbations of the lunar orbit we may mention the evection (q.v.), which may displace the moon'sposition in the sky 1° IC 27", the variation, which may amount to 30' 31", and the annual equation, whose maximum is 11' 9". See Lunar Theory. Eclipses. As the moon in lier course passes the sun once every month, and also places the earth Ix-twccn herself and the sun once a month, it is evident that if slie moved in the plane of the ccli|itic there would be either a total or an annular eclipse of the sun and a total eclipse of the moon every month. The inclination of her orbit, allowing her to pass the sun 5° 9' to the north or south of his track, jjrevents such a fre- i|uent occurrence of eclipses. See KcLIPSES. Rotation. The moon rotates on her axis with a velocity such that one complete revolution occupies precisely the same time needed for one revolution of the moon around the earth. As a consequence of this, the moon always turns the same side toward us. and we see only one-half her surface jilus a small additional amount brought into view by libration (q.v.). Physical Features. The surface of the moon, as seen from the earth, presents a most irregular grouping of light and sliade. The dark portions were named by the earlier astronomers as seas, lakes, etc., and still retain these names, although there is strong evidence against the suppositiun that the moon, or at least that portion of it presented to us. contains any water. The brighter parts of the moon arc mountainous, as is proved by the fact of their casting sliadows when the sun's rays fall upon, them obli<|Ucly, and also liy the ragged ajipearancc jirescntcd tiy the interior illuminated border of the moon, an appearance which can only be satisfactorily accounted for on the supposition that the siirfacc of the moon is not level, in which case the higlier portions will be illuminated some time before tlic light reaches the level parts; and it is obsen-ed that as the illumination proceeds, bright spots start up in advance of it. and when the moon is on the wane, these same spots continue to shine for some time after the surrounding surface is immersed in gloom. The mountains occur either singly, when they arc generally of a circular form, ami are called rratrrs, or in groups, which are mostly anniihir. and form n sort of wall inclosing a deep depressiim or plain, in which are situated one or more conical mouitains. The craters are not in- frequently 8 or 10 miles in diameter, and some measure more than 100 miles aeros-. Tlw prin- cipal mountains attain an altitude of about 20,- 000 feet, according to a micrometrie measure- ment of the length of their shadows. The moon everywhere presents traces of volcanic agency, but no active volcanoes have yet been discovered, nor is there any sign of recent volcanic action. Through the telescope, she presents a desolate appearance, without indications of animal or vegetable existence. She appears to be devoid of an atmosphere, or, if one exists, it nuist be of ex- ceeding rarity, or else concentrated into cavities within the moon's rockj' surfaces. Probabilities are in favor of a low surface temperature, not higher, perhaps, than that of ordinary ice. (For the influence of the moon ujion terrestrial tides, see Tides.) Recent theorists hold that very large lunar tides, caused by the earth, existed many thousands of years ago. when the moon was still in a semi-plastic condition. This tidal theory can be made to account for the reuuirkalde coin- cidence of the lunar axial rotation period with that of her revolution round the earth. The best lunar map is that of Beer and Maedler, which was published in 1837. This map is based upon visual observations, and will undoubtedly be replaced in time by the results of photographic work. At present (1003) an elaborate scries of lunar photographs is being published by the Paris Ob- servatory; and a very good set of drawings from photographs taken at the Lick Observatory is being made by Weinek of Prague. Superstitions Recarm.no tue Moon". The moon was anciently an object of wor.ship, and has remained to the present day the centre of many superstitions. The times for killing animals for food, gathering herbs, cutting down wood for fuel, sowing seeds of various kinds, were all regu- lated by the 'age' of the moon. There were simi- larly defined periods for taking particular medi- cines, and attempting the cure of particular dis- eases. In northern Eurojiean countries the wan- ing moon has been considered to have an evil in- fluence, and full or new moon to be the most auspicious season for commencing any enterprise. Farmers and sailors still believe in the influence of changes in the lunar phases on the weather. See Superstition. MOON, William (1818-94). An English phi- lanthropist, born in Horsemonden, Kent. He was educated in London, and in 1840 gave up his studies for the Church l)eca>ise of total blindness. Moon started a school for blind children, and find- ing that previous systems were too complicated, devised an embossed type f(U- the use of the l)lind with only nine letters, which, by v;iriation of position, made up a complete alpbabi't. Follow- ing the same method, he puldishcd pictures and maps for the blind. Jloon traveled in Euro))e and in the United States (1882) and established loan libraries of his books and schools for home in- struction. All his philanthropic elTorts were largely tinged with evangelistic mctho<ls. Con- sult Rutherford. Ifi7/m»i Moon and His Work for Ihe Wind (London, 1898). See Blind. Edu- cation or the. MOONBILL. . local name in the United Stale- for the ring-necked scaup duck. See Sua I p. MOONCALF. A .shapeless abortion, supposed to be caused by the indncnce of the moon, or, according to Pliny, to be engendered by woman only. The term is applied also to a doltish person.