SEGMENT of a Lire*, in geometry, that part of the circle contained between a chord and an arch of the same circle.
Samuer of u sphere, is a part of a sphere terminated by a portion of its sur face, and s'plane which cuts it off, pass ing somewhere owt of the centre ; being more properly called the section of a sphere. The base of such a segment, it is evident, is always a circle. And the con vex surfaces of different segments arc to each other as their altitudes or versed sines. And as the whole convex surface of the sphere- is equal to four of its great circles, or four circles of the same diame ter; so the surface of any segment is equal to four circles on a diameter equal to the chord of half the arc of the segment. So that if d denotes the diameter of the sphere, or the chord of half the circum ference, and c the chord of half the arc of any other segment, also a the altitude or versed sine of the same; then,
.3.1416d' is the surface of the whole sphere, and 3.1416c', or 3.1416d the surface of the segment.
For the solid content of a segment there are two rules usually given ; viz. 1. To three times the square of the radius of its base, add the square of its height ; multiply the sum by the height, and the by 5236. Or, 2dly, From three times the diameter of the sphere, subtract twice the height of the frustrum ; multi ply the remainder by the square of the height, and the product by .5236.
SEGUlEillA, in botany, so named in honour of Jean Francois Seguier, a genus of the Pulyandria Monogynia class and order. Essential character : calyx, five leaved ; corolla none; capsule, one-seed ed, terminated by a large wing, having small lateral ones. There are two species, viz. S. Americana and S. Asiatics.