158 cosmos. 



of the attractive force which she exercises in common with 

 the Sun, excites motion in our ocean — the liquid portion of 

 the Earth — gradually changes the surface by periodical floods, 

 and the outlines of continental coasts, by the destructive agen- 

 cy of the tides, hinders or favors the labor of men ; affords 

 the greater part of the material from which sandstones and 

 conglomerates are formed, and which are again covered by 

 the rounded, loose, transported detritus.^ Thus the Moon, 

 as one of the sources of motion, continues to act upon the ge- 

 ognostic relations of our planet. The indisputable! influence 



cet astre. Alors la Lune, sans cesse en opposition au Soleil, eUt decrit 

 autour de lui une ellipse semblable a celle de la Terre ; ces deux astres 

 se seraient succede l'un a l'autre sur l'horizon ; et comme a cette dis- 

 tance la Lune n'eut point ete eclipsee, sa lumiere aurait certainement 

 remplace celle du Soleil." " Several partisans of final causes have im- 

 agined that the Moon has been given to the Earth to light it during the 

 night ; in that case, nature would not have attained the object which 

 she had proposed, because we are frequently deprived at the same time 

 of the light of the Sun and Moon. To have attained this end, it would 

 have been sufficient in the beginning to place the Moon in opposition 

 with the Sun, in the same plane of the ecliptic, at a distance equal to 

 the hundredth part of the distance of the Earth from the Sun, and to 

 give to the Moon and the Earth velocities parallel and proportional to 

 their distances from that body. Then the Moon, constantly in opposi- 

 tion to the Sun, would have described an ellipse round it like that of 

 the Earth ; these two bodies would have succeeded each other in the 

 horizon, and as at that distance the Moon would never have been 

 eclipsed, its light would certainly have replaced that of the Sun." Liou- 

 ville finds, on the contrary, " Que, si la Lune avait occupe a l'origine la 

 position particuliere que l'illustre auteur de la Mecanique Cileste lui 

 assigne, elle n'aurait pu s'y maintenir que pendant un temps tres court." 

 " That if the Moon had occupied at the beginning the particular posi- 

 tion assigned to her by the illustrious author of the Mecanique Celeste, 

 she would not have been able to maintain it for more than a very short 

 time." 



* On the Transporting Power of the Tides, see Sir Henry de la Beche, 

 Geological Manual, 1833, p. 111. 



t Arago, Sur la question de savoir si la Lune exerce sur notre Atmo- 

 sphere une influence appreciable, in the Annuaire for 1833, p. 157-206. 

 The principal advocates of this opinion are Scheibler {Unter&nch. uber 

 Einfluss des Mondes auf die Vcrdnderun gen in unserer Atmosphdre, 1830, 

 p. 20); Flaugergues (Zicanzigjdhrige Beobachtungen in Viviers, Bill- 

 Universelle, Sciences et Arts, torn, xl., 1829, p. 265-283, and in Kastncr's 

 Archivf. die ges. Naturlehre, bd. xvii., 1829, sees. 32-50); and Eisenlohr 

 (Poggend., Annalen der Physik, bd. xxxv., 1835, p. 141-160, and 309- 

 329). Sir John Herschel considers it very probable that a very high 

 temperature prevails upon the Moon (far above the boiling-point of 

 water), as the surface is uninterruptedly exposed for fourteen days to 

 the full action of the Sun. Therefore, in the opposition, or some few 

 days after, the Moon must be, in some small degree, a source of heat 

 for the Earth; but this heat, radiating from a body far below the tem- 

 perature of ignition, can not reach the surface of the Earth, since it is 



