OF ASPECT, ROTATION, LIBRATION, ETC. 161

10° as at to, instead of more than 15°, as is tliecase with the sun.

Next let us suppose that the descending node ofthe moon’s orbit is at W (fig. 53, Plate XIII.), theplace of the vernal equinox; thenWTOEm' is themoon’s orbit; e to and e to' are arcs of about 5° 9'; andwe see that the range of the moon north and south ofthe ecliptic is less than the range of the sun by theseequal arcs. Thus the moon when at to is about18° 18' north of the equator instead of 23° 27', andshe is about 18° 18' south of the equator when at to'.Thus she has a smaller range than the sun north andsouth of the equator. She never attains a greaterelevation above the southern horizon than about 56°as at m; but, on the other hand, her least elevationwhen due south exceeds 20°, as at ft (the sun’s greatestand least southing elevations, as at e and t, being re-spectively about 61° and about 15°).

Thirdly, let the rising node of the moon’s orbit benear e, the place of the summer solstice (fig. 54, PlateXIII.); then eMe'M' is the moon’s orbit, whichcrosses the equator at two points, M and M', inadvance of the equinoctial points W and E.* We see

* These points and the points m and m' are about 12J degreesfrom the points E and W, being determined by the relation thatthey are points on the equator about 5° 9' north of the ecliptic.If great nicety were required in the above explanation, we shouldhave to take into account the fact that the moon’s orbit has notexactly its mean jnclination to the equator when the nodes are onthe solsticial colure ; for the angle e M is not equal to the angle8 ® -E, the mean inclination in question. But considerations of

M.