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CHAPTER III.

THE moon’s CHANGES OP ASPECT, ROTATION,LIBRATION, ETC.

The moon’s motions in the heavens, as seen from theearth, are readily understood from what is known ofher actual motions. I propose now to enter into ageneral consideration of these apparent motions ofthe moon, and of the varying aspect which she accord-ingly presents to us. It would be possible to fill amuch larger volume than the present with the detaileddiscussion of these matters ; nor would such a volumebe wanting in interest, at least to those havingmathematical tastes. I do not indeed know of anysubject which a geometrician could better wish toexamine. It is full of neat and interesting problems,and might worthily occupy many years of labour.But in this volume such researches would be out ofplace. We must be content with such a considerationof the subject as shall leave none of its salient featuresunexplained. In passing it may be remarked thateven such a treatment of the moon’s apparent motionshas long been a desideratum, inasmuch as our text-