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appearance as seen from the earth. This will appearobvious as we proceed.)
The moon’s equator-plane is inclined 1° 30' 11" tothe plane of the ecliptic, and is always so placed thatwhen the moon is at the ascending or descendingnode of her orbit, the equator-plane is turned edge-wise towards the earth, and is inclined descendinglyor ascendingly (respectively) to the ecliptic. In otherwords, if e M e' (fig. 61, Plate XIV.) represent theecliptic, M being the rising node of the moon’s orbit,M M', then the moon’s equator is in the positionE E'; while, if M is the descending node (fig. 63), thenthe equator is in the position EE' (fig. 63); theangle eME in both cases being one of 1° 30' 11".Since the average inclination of the moon’s orbit tothe ecliptic is nearly 5° 9', it follows that the angleE M M' has a mean value of about 6° 39'; but thisangle varies as the inclination of the moon's orbitvaries, and is sometimes as great as 6° 44',* sometimesas small as 6° 34'.
Now the effect of this inclination of the moon’s axisto the plane of her orbit about the earth correspondsprecisely to the seasonal variations of the earth’s pre-sentation towards the sun. Thus we see that as themoon passes away from the position shown in fig. 61>
* I find commonly 6“ 47' set as the value of this angle. Thisseems to he obtained by adding the moon’s maximum orbit incli-nation 5° 17' to the inclination of her axis to the ecliptic. But themoon is always near a node when her orbit attains its maximuminclination, whereas the maximum opening due to her inclination isattained when she is farthest from her nodes.