OF ASPECT, ROTATION, AND L1BRATION. 155

ecliptic in autumn, for then the new moon is, withthe sun, at or near the descending node of the ecliptic.Accordingly, in autumn, the difference between thehours at which the full moon rises on successivenights is small. It amounts, in fact, on the average,in our latitudes to rather more than twenty minutes(or about half an hour less than the mean interval).

But the inclination of the moon's orbit and themoon's variable motion due to the eccentricity of herorbit cause these results to be considerably modified.We can at once consider this feature (proposing pre-sently to discuss more particularly the moon’s motionon her inclined eccentric orbit). Let us suppose thatwhen at E, fig. 52, Plate XII., the moon is crossingthe equator, ascendingly or towards M', and is also atthe rising node of her orbit. Then, instead of followingthe course E M', she will travel along such a course asis shown by the dotted line E 1, or will be yet nearerthan M' to the horizon at the end of the twenty-fourhours,—in other words, the interval between succes-sive risings at this season will be yet more shortenedthan we have found it to be on the assumption thatthe moon moves on the ecliptic. In like mannerif when at E, and crossing the equator descendingly,the moon is at her descending node (which willobviously correspond to the period when she crossesthe equator ascendingly while near her ascendingnode) then, instead of following the course E M,she will follow the course E 4, or will be yetfarther than M from the horizon at the end of the