LIMB

, the outermost border, or graduated edge, of a quadrant, astrolabe, or such like mathematical instrument.

The word is also used for the arch of the primitive circle, in any projection of the sphere in plano.

Limb also signifies the outermost border or edge of the sun or moon; as the upper Limb, or edge; the lower Limb; the preceding Limb, or side; the following Limb.—Astronomers observe the upper or lower Limb of the sun or moon, to find their true height, or that of the centre, which differs from the others by the semidiameter of the disc.