sextain

[Lat., from sext us =six.] A stanza of six lines. *sex-tănş, s . [Lat., from sext us =sixth.] 1. Roman Antiq.: A coin, the sixth part of an as. 2. Astron.: The sextant (q. v.) sex-tant, s . [Lat. sextans (gen it. sextant is )=a sixth part; Fr. sextant ; Sp. sextante ; Ital. sestante .] 1. Math .: The sixth part of the circumference of a circle. 2. Surv . & Navig .: An instrument used in measuring angles, founded upon the optical principle that a ray of light twice reflected from plane reflectors makes, with the ray before reflection, an angle equal to twice the angle of inclination of the reflecting surfaces. It resembles a quadrant, but has an arc of about 65° The re flecting sextant is an improved form of the quadrant of reflection, invented by Newton in 1699 [QUADRANT], and is capable of measuring angles of 120° or more. It consists of a frame, generally of metal, but sometimes of ebony, stiffened by cro -braces, and hav Sextant. ing an arc embracing about 65° of a circle. This is divided into double the number of degrees actually embraced between the two extreme grad uations of the arc, as the fixed and movable gla es, owing to the double reflection, only form with each other an angle equal to half the angular distance between the two objects observed, one of which is seen directly and the other by reflection from the index-gla . 3. Astron.: Sextans; one of the constellations introduced by Hevelius. It extends a little more than from the equator to the ecliptic, between Regulus and Cor Hydræ .