Sector

( Secteur, Fr. ) A mathematical instrument of great use in finding the proportion between quantities of the same kind, as between lines and lines, surfaces and surfaces, . for which reason the French call it the compa of proportion. The great advantage of the sector, above common scales, . is, that it is adapted to all radii, and all scales. The sector is founded on the fourth proposition of the sixth book of Euclid. The sector consists of two equal legs, or rules of bra , . riveted together, but so as to move easily on the rivet; on the faces of the instrument are placed several lines; the principal of which are: the line of equal parts, line of chords, line of sines, line of tangents, line of secants, and line of polygons. To SECURE , in a military sense, to preserve, to keep, to make certain. As to secure a place, to secure a conquest. In the management of the firelock, it signifies to bring it to a certain position, by which the locks are secured against rain. Hence