LET. XXII. SUN AND MOON. , 385

sible; and they are now removed at as great adistance from the limits of eclipses as when theearth was at F.

The point X, where the moon’s orbit crossesthe ecliptic, is called the Ascending Node, be-cause the moon ascends from it above the eclip-tic ; and the opposite point of intersection V, iscalled the Descending Node, because the moondescends from it below the ecliptic. And whenthe moon is in the higher part of her orbitX Y V, she is said to have north latitude; andwhen sire is in the lower part V W Y, site is saidto have south latitude. It appears, also, fromwhat has been already observed, that when theearth is at E and G, the moon is about hernodes at new and full, and in her greatest northand south latitude at her quarters: but whenthe earth is at F or H, the moon is in her great-est north and south latitude at new and full, andin the nodes about her quarters.

If the line of the nodes were always carriedparallel to itself round the sun, there would bejust half a year between the conjunctions of thefun and nodes. But as the nodes shift back-wards, or contrary to the earth’s annual motion,about 19-!- degrees in a year, the fame node willcome round to the fun about nineteen dayssooner every year than upon the preceding one ;so that from the time when the ascending nodeX passes by the fun, as seen from the earth at E,C c there