MOON. 



line of illumination, always even and without promi- 

 nences. Hence they are supposed to be plains, con- 

 sisting of a substance which has comparatively little 

 power of reflecting the sun's rays. That they are 

 seas, is not probable, since Huyghens observed great 

 depressions in them, and Schroter, in several of these 

 depressions, discovered evident traces of various hori- 

 zontal strata, lying one upon the other, and forming a 

 wall around them. Schroter, who measured several 

 of these depressions, found their diameter to be from 

 thirty feet to more than half a mile ; the diameter 

 of one, in fact, was above sixteen miles, and its depth 

 30,000 fathoms. The number of spots on the moon 

 was formerly considered to be 244. Schroter has 

 increased their number to 6000, and accurately ob- 

 served and described many of them. There is no 

 appearance of water in the moon. The depressions, 

 with their walls and surrounding mountains, Schroter 

 regards as craters. The large grey spots appear to 

 him regions which have suffered less, and in which, 

 perhaps, some vegetation exists. He has also ob- 

 served other changes on the moon's surface, which 

 he considered to be of volcanic origin. From all 

 appearances, it would seem that the surface of the 

 moon is still subjected to great revolutions. Perhaps 

 it is still torn open or thrown up in prominences by 

 violent volcanoes and earthquakes in the interior, 

 as may have once been- the case with our earth 

 also. Such revolutions have been. supposed to afford 

 a means of accounting for the fall of meteoric stones 

 on the surface of our earth, the power of a volcano 

 in the moon being supposed sufficiently great to 

 throw such masses out of the sphere of the moon's 

 attraction into that of the earth. (See Meteoric 

 Stones.) The shepherd Endymion, according to 

 Pliny, first observed the course of the moon and its 

 changes. Hence the story of Endymion and Diana, 

 Even the Chaldeans considered the moon as the 

 smallest among the heavenly bodies and the nearest 

 to the earth ; they knew that her light was borrowed, 

 fixed her periodical phases with much accuracy, and 

 attributed her eclipses to the shadow of the earth. 

 That the moon was inhabited, was conjectured by 

 Orpheus, or rather by the author of the verses which 

 exist under his name ; and Pherecydes of Scyros, a 

 contemporary of Servius Tullius, is said to have 

 determined the time of her revolution. The Pytha- 

 goreans affirmed that the moon contained mountains, 

 cities, plants, animals, and men. Anaximander 

 knew the size of the moon, its distance from the 

 earth, and that its light was borrowed from the sun. 

 The spots on its surface Clearchus considered to be 

 seas. In modern times, this planet has occupied 

 much of the attention of astronomers. The question 

 whether the moon has an atmosphere has been settled 

 by Schroter in the affirmative. See the article on 

 the moon's atmosphere, in the first volume of Geh- 

 ler's Physikal. JVdrterbuch (Leipsic, 1825). 



Doctor Francis von Paula Gruithuisen, professor of 

 astronomy at Munich, has, of late years, paid great 

 attention to the moon, and his discoveries and hypo- 

 theses, though wanting confirmation, have excited 

 much interest. In his opinion, the straight lines, 

 often of considerable length and a parallel direction 

 which have been observed on its surface, and which 

 are made up of objects resembling, in shape, a star, 

 an inverted Z, &c., are, in fact, roads, with cities, 

 temples, dwellings, &c. At present, however, these 

 conjectures can hardly be regarded as more than 

 creations of a lively imagination. The Topographii 

 der sichtbaren Mondoberflache, by W. G. Lohrmann 

 (Leipsic, 1824, 4to), represents the elevations anc 

 colours of the moon's surface with fidelity, and in 

 such a manner as not to be affected by the Jibration or 

 the different degrees of illumination. See also Dr< 



lisch's De vera Lunee Fignra, and his Symtjla ad 

 Selenographium mathematician (Leipsic, 1826). 



The various appearances which the moon periodi- 

 cally presents in the different parts of its revolution, 

 ire termed phases, and arise from the different posi- 

 ions which its opaque mass assumes in relation to the 

 sun and the earth. Every one knows that, at a cer- 

 ain period of the moon's revolution, it is invisible ; 

 at other times, it appears of a sickle shape, then 

 emicircular, and finally presents a complete circular 

 disk. When the moon is between the sun and the 

 arth (in which case the sun and moon are said to be 

 n conjunction), it presents its unillumined side to us, 

 and we can see nothing of it. In this state it is cal- 

 ed the new moon. Soon after, it recedes from the 

 sun, and a small part of its illumined surface becomes* 

 visible in the evening horizon. Four days after the 

 time of new moon, it has receded 45 from the 

 un ; and now a portion of its illumined surface is 

 seen in the shape of a sickle, with the horns towards 

 the sun. The moon now departs every day farther 

 from the sun, moving in a direction from west to 

 east, and therefore appears every evening nearer the 

 eastern horizon, and the sickle shaped figure grows 

 daily broader. After about eight days from the time 

 of new moon, it has departed 90 from the sun, and 

 now shows a bright semicircular disk. In this state 

 the almanacs say the moon is in its first quarter. 

 Departing continually farther, the illumined portion 

 continually increases, and assumes more and more 

 of a circular figure, until, about fifteen days after the 

 time of new moon, when it stands directly opposite 

 the sun, it presents a complete circular disk. In this 

 state we call it the f till moon. At this time, it rises 

 when the sun sets, and shines the whole night 

 through. From new moon to full moon, it is said to 

 wax (increase). From the day of full moon, it de- 

 creases, with each successive day, on the side most 

 distant from the sun, as it is now approaching the 

 sun at the same rate as it before departed. In the 

 course of seven or eight days, it has again arrived 

 within 90 of the sun, and now shows but half its 

 disk on the left side, and is said to be in its last 

 quarter. At this time, it rises at midnight. It now 

 shows less and less of its illumined surface, and 

 finally assumes the sickle shape, with the horns, how- 

 ever, turned from the sun ; rises later and later, and 

 at the end of about twenty-nine days from the time 

 of new moon again comes into conjunction with the 

 sun, disappears, and commences a new revolution. 

 From full moon to new moon, it is said to wane. The 

 moon, when new and full, is said to be in its syzygies, 

 and its appearances at the different quarters are cal- 

 led changes. As well before as after new moon, the 

 naked eye can discern a pale light on the portion of 

 the disk not illumined by the sun. This is reflected 

 from the earth ; for, at the time when it is most per- 

 ceptible, the sun has not yet set, in the afternoon, and 

 in the forenoon has been up for some time. The 

 inhabitants of the moon, therefore, at such times, see 

 our earth as an illumined disk in the heavens, four- 

 teen times larger than the moon appears to us. 



Age of the moon is the number of days since the 

 new moon, which is found by the following rule : 

 To the epact add the number and day of the mouth, 

 which will be the age required, if less than thirty ; 

 and if it exceed thirty, subtract this number from it, 

 and the remainder will be the age. See Epact. 



Harvest moon is a remarkabfe phenomenon relat- 

 ing to the rising of this luminary in tiie harvest 

 season. During the time she is full, and for a few 

 days before and after, in all, about a week, there is 

 less difference in the time of her rising between any 

 two successive nights than when she is full in any 

 other month of the year. By this means she affords 



