SECOND

, in Geometry, or Astronomy, &c, the 60th part of a prime or minute: either in the division of circles, or in the measure of time. A degree, or an hour, are each divided into 60 minutes, marked thus′; a minute is subdivided into 60 Seconds, marked thus ″; a Second into 60 thirds, marked thus ‴; &c.

We sometimes say a Second minute, a third minute, &c, but more usually only Second, third, &c.

The Seconds pendulum, or pendulum that vibrates Seconds, in the latitude of London, is 39 1/8 inches long.

SECONDARY Circles of the Ecliptic, are circles of longitude of the stars; or circles which, passing through the poles of the ecliptic, are at right angles to the ecliptic.

By means of these Secondary circles, all points in the heavens are referred to the ecliptic; that is, any star, planet, or other phenomenon, is understood to be in that point of the ecliptic, which is cut by the Secondary circle that passes through such star, &c.

If two stars be thus referred to the same point of the ecliptic, they are said to be in conjunction; if in opposite points, they are in opposition; if they are referred to two points at a quadrant's distance, they are said to be in a quartile aspect, if the points differ a 6th part of the ecliptic, they are in sextile aspect, &c.

In general, all circles that intersect one of the six greater circles of the sphere at right angles, may be called Secondary circles. As the azimuth or vertical circles in respect of the horizon, &c; the meridian in respect of the equator, &c.

Secondary Planets, or Satellites, are those moving round other planets as the centres of their motion, and along with them round the sun.