MOON 



299 



range from 10 to 20 miles broad. They pass right 

 on over mountains and plains, partaking of the 

 shape of the surface at all points, but distinct from 

 it in brightness. There are seven principal systems 

 of these inexplicable streaks. 



To denote the relative brightness of lunar forma- 

 tions a scale is used, the brightest being called 

 10, and the less bright 9, 8, &c., down to 0. 

 These formations are variously named. The 

 principal mountain ranges have teen named after 

 those on the earth. Tlie craters are named after 

 astronomers or philosophers, as Tycho, Plato, Aris- 

 totle, &c. The different parts of these, and smaller 

 objects near them, are known by Greek or lionian 

 letters, attached to the name of the chief object. 

 Greek letters are used for peaks and hills, Roman 

 letters for craters and depressions. Capital letters 

 imply measured objects. For rills the letters 

 4>i ^. Xr 0, and ij are chiefly used. But there 

 are occasional variation* from these rules, as in the 

 case of most astronomical nomenclature. 



These peculiar appearances, so different from 

 those around us on the earth, have much puzzled 

 astronomers. The usual theory attributes them to 

 volcanic action, combined with shrinkage of the 

 lunar globe on cooling. A recent theory explains 

 them as the result of slow glaciation, the craters 

 lieini: lakes, around whose margins the quickly 

 condensed vapour from their surfaces has fallen 

 in mountains of ice. The craters are vents for 

 water-vapour, and their cones masses of ice. To 

 this theory the extreme rarity of the lunar atmo- 

 sphere is favourable, but it cannot be said, any more 

 than the volcanic theory, to meet all the diHiculties. 

 No thoroughly satisfactory explanation has as yet 

 been proposed. 



The total amount of light given by the full 

 iiiiinii is probably less than rnoWoth "f the """. Its 

 photographic intensity, however, has admitted of 

 MYWal line photographs being taken, notably by 

 liuiherlord of New York, and recently by the 

 tine fl' j -co]>c of the Lick Observatory, California. 



Harvett-moon. At or about the time of har- 

 vest in the north temperate zone the sun in its 

 annual course is approaching the celestial equator, 

 which it crosses from north to south on September 

 '22. On that date it sets close to the exact western 

 point of tlie liori/on. If it happens to be then also 

 full moon, the moon rises that evening as the sun 

 .s.-t-. :md is at its rising opposite the sun, or close 

 to tli" exact eastern [mint of the horizon. Thus it 

 lupins to give light at sunset, ami continues to do 

 so until sunrise, when it sets opposite to the sun, 

 just as the latter rises. This arrangement holds 

 good without any great change for several day-, so 

 that there is practically no darkness, especially if 

 tin' weather lie fine. The full moon which thus 

 illumines the autumn nights is called the lmrri:it- 

 iiiniiii. No other full moon in the year rises for so 

 many days in succession so soon after sunset. If 

 the date of full moon lie not exactly September 22, 

 ."till the same phenomena occur, though not with 

 i he same perfection, and the longer the interval 

 I iet ween full moon and that date the less perfect 

 they are. This is Itecauae the full moon, being on 

 September 22, coincides with the time when the 

 moon (being at full moon necessarily opposite the 

 sun ) is crossing the celestial equator from south to 

 north, at which time its northward motion is most 

 rapid. The position of any body on the Celestial 

 Sphere (q.v.) determines the time of its rising at 

 any place in our latitudes, and, if that position lie 

 altered, the time of rising will he altered also. If 

 it moves southward the moon will tend to rise later, 

 if it moves northmtrd it will tend to rise rnrlnr. 

 We have seen that the moon's northward motion is 

 mii-t rapid whrn crossing the equator. Hence it 

 ]I;L- then a strong tendency to rise earlier each 



evening. But its motion towards the east (or 

 downwards, when it is on the eastern horizon ) gives 

 it a tendency to rise later. These opposite tend- 

 encies, in the case of the September full moon, 

 approach a balance, if the observer be in the lati- 

 tude of northern Europe. Therefore the moon in 

 that case rises only a few minutes later each even- 

 ing for about a week. Farther north, almut lat. 

 64J, a balance is attained, and for two evenings 

 the moon rises at the same time. Still farther 

 north it rises earlier the second evening. But the 

 most generally observed phenomena are of course 

 those to be seen between latitudes 40 and 60, 

 which consist in the nearly full moon rising but 

 little after sunset for several days in succession. 

 In these latitudes of the southern hemisphere 

 March enjoys the benefit of the harvest-moon, as 

 September does in the north. And as celestial 

 appearances are reversed to observers in different 

 hemispheres, it follows that, when we have most 

 benefit from the full moon, our neighbours at the 

 antipodes have least. 



The best charts of the moon's surface are those by 

 Lohrmann, Beer, and Madler, Schmidt of Athens (a 

 gigantic work }, and the Committee of the British Associ- 

 ation. For further information readers may consult I > f 

 amid, by Beer and Madler (1837); Tlie Moon, by Ed. 

 Neison (1876); The AToon, by Nasmyth and Carpenter 

 ( 1874; new ed. 1885) ; and for the lunar theory, popu- 

 larly treated, Airy's Gravitation, and Sir J. Herscbel's 

 Outline* of Aitronomy. 



Superstition* regarding tlie Moon. The moon was 

 anciently an object of worship, and even in the 

 17th century she was supposed by the common 

 people of England to exercise great influence over 

 human affairs. The times for killing animals for 

 food, gathering herbs, cutting down wood for fuel, 

 sowing seeds of various kinds, were all regulated 

 by the 'age' of the moon, and these set periods 

 were considered to be a necessary part of practical 

 knowledge, and ignorance or neglect of them 

 to l>e infallibly productive of loss. There were 

 similarly defined periods for taking particular 

 medicines and attempting the cure of particular 

 Many sued superstitions prevailed till 

 a recent period in the Highlands of Scotland, 

 favourable or unfavourable consequences from any 

 occurrence being predicted according to the age 

 of the moon at the time it happened. Through- 

 out Scotland the waning moon was considered to 

 have an evil influence, and full or new moon to 

 !>< tlie most auspiciou> season for commencing any 

 enterprise. The same opinion was held in Scandi- 

 navia and Germany, and the history of all nations 

 teems with similar superstitions. The special influ- 

 ence of the moon on persons of weak or wavering 

 reason is preserved in our words lunatic and moon- 

 struck, and is still an article of popular belief. 

 Amongst mere superstitions must be ranked iln> 

 old and widespread Indict' that the changes of the 

 moon influence the weather on the earth, bringing 

 about fair or rainy, settled or stormy weather ; so 

 that from the moon's periods predictions as to the 

 weather may be made. The only known weather 

 influence is a slight but appreciable tendency to 

 dispersion of clouds shortly after full moon. See 

 the article ECI.IPSKS. 



In the Edda we read that ' Mundilffiri had two 

 children a son, Mani( 'moon'), and a daughter, Sftl 

 ( ' sun ' ) ; ' and 1 in German the moon is masculine and 

 the sun feminine to this day. It was the same in 

 Anglo-Saxon, although modern English has in this 

 matter followed the classic mythology, in which 

 Phoebus and Sol are gods and Selene, Luna, and 

 Diana are goddesses ; Grimm (Deutsche Mytliologie, 

 p. 666) quotes an old invocation to the 'New 

 Moon, gracious lord' (Neuer Mon, Holder Herr), 

 for increase of wealth ; and down to recent times 



