ANNULUS

, a species of Voluta. See also Ring.

ANOMALISTICAL Year, in Astronomy, called <*>lso periodical year, is the space of time in which the <*>arth, or a planet, passes through its orbit. The ano- <*>nalistical, or common year, is somewhat longer than <*>he tropical year; by reason of the precession of the <*>quinox.

And the apses of all the planets have a like progresive motion; by which it happens that a longer time is <*>ecessary to anive at the aplielion, which has advanced <*> little, than to arrive at the same fixed star. For eximple, the tropical revolution of the sun, with respect

to the equinox, is	365da	5h	48m	45s;
but the sidereal, or return to the same star,	365	6	9	11;
and the anomalistic revolution is	365	6	15	20,

because the sun's apogee advances each year 65″ 1/2 with respect to the equinoxes, and the sun cannot arrive at the apogee till he has passed over the 65″ 1/2 more than the revolution of the year answering to the equinoxes.

To find the anomalistic revolution, say, As the whole secular motion of a planet minus the motion of its aphelion, is to 100 years or 3155760000 seconds, so is 360°, to the duration of the anomalistic revolution.