e*s**r^r- . 



THE MOON. 



now, have occupied the same position throughout all human record. We have 

 already stated that the first and most obvious inference which this fact suggests, 

 is that the same hemisphere of the moon is always presented toward the earth, 

 and consequently, the other hemisphere is never seen, nor can we ever see it. 

 This singular characteristic which attaches to the motion of the moon round j 

 the earth, seems to be a general characteristic of all other moons in the 

 system. Sir William Herschel, by the aid of his powerful telescopes, as- 

 certained that the moons of Jupiter revolve in the same manner, each pre- 

 senting continually the same hemisphere to the planet. The cause of this pe- 

 culiar motion has been attempted to be explained by the hypothesis that the 

 hemisphere of the satellite which is turned toward the planet, is very elonga- 

 ted and protuberant, and it is the excess of its weight which makes it tend to 

 direct itself always toward the primary, in obedience to the universal principle 

 of attraction. Be this as it may, the effect is in the case of the moon, that 

 our geographical knowledge is necessarily limited to that hemisphere which 

 is turned toward us. 



If the moon were inhabited, observers upon it would have an extraordinary 

 spectacle presented to them by the earth. In their firmament the earth is an 

 object with a diameter four times, and a disk sixteen times, greater than that 

 which the moon presents to us. A spectator placed on the centre of the hemi- 

 sphere of the moon which is toward us, would see the orb of the earth pre- 

 senting the appearance of a gorgeous moon of immense magnitude, always in 

 his zenith : it would never rise, nor set, nor change its position at all in the 

 firmament ; it would, however, undergo all the varieties of phases of the moon 

 when the moon appears to us full, it would be new, and when the moon ap- 

 pears new, it would be full ; when the moon appears to us a crescent, it would 

 be gibbous, and vice versa. 



But what is the condition and character of the surface of the moon ? What 

 are the lineaments of light and shade which we see upon it ? There is no ob- 

 ject outside the earth with which the telescope has afforded us such minute 

 and satisfactory information. 



If, when the moon is a crescent, we examine with a telescope, even 

 of moderate power, the concave boundary which, is that part of the lunar 

 surface where the enlightened hemisphere ends and the dark hemisphere 

 begins, we shall find that this boundary is not an even and regular curve, which 

 it undoubtedly would be if the surface of the globe of the moon were smooth 

 and regular, or nearly so. If, for example, the lunar surface, resembled in its < 

 general characteristics that of our globe ; granting the total absence of wa- j 

 ter, and that the entire surface is land, that land had the general character- 

 istics of the continents of the globe of the earth ; then I say, that the inner 

 boundary of the lunar crescent would still be a regular curve, broken or inter- 

 rupted only at particular points. Where great mountain ranges, like those 

 of the Alps, the Andes, or the Himalaya, might chance to cross it, in such pla- 

 ces these lofty peaks would project vastly-elongated shadows along the adja- 

 cent plain ; for it will be remembered, that, being situated at the moment in 

 question, at the boundary of the enlightened and darkened hemispheres, the 

 shadows would be those of evening and morning ; which are prodigiously lon- 

 ger than the objects themselves. The effects of these would be to cause gaps 

 or irregularities in the general outline of the inner boundary of the crescent; 

 with these rare exceptions, the inner boundary of the crescent produced by a 

 globe like the earth would be an even and regular curve. 



Such, however, is not the case with the inner boundary of the lunar cres- 

 cent, even when viewed by the naked eye, and still less so when magniried 

 by a telescope. 



