descending

a. Of or pertaining to descent; moving downwards. [ 1913 Webster ]

Descending constellations or
Descending signs (Astron.), those through which the planets descent toward the south. --
Descending node (Astron.), that point in a planet's orbit where it intersects the ecliptic in passing southward. --
Descending series (Math.), a series in which each term is numerically smaller than the preceding one; also, a series arranged according to descending powers of a quantity. [ 1913 Webster ]