CYLINDER

(Gr. xvXmhiu, 1 roll.) In Geometry, a solid which may be conceived to be formed by the revolution of a rectangular parallelogram about one of its sides. The surface of a cylinder, not including the two ends, is equal to the rectangle formed by multiplying the circumference of its base into its altitude; and the solid content is equal to its^ altitude multiplied into the area of its base. The cone, the sphere, and the cylinder have S remarkable relation to each other, first discovered by Arch i me des: namely, that the cone is one third of the cylinder, having the same base and altitude; and the inscribed sphere two thirds of the cylinder; or the cone, the sphere, and the cylinder are to each other as the numbers 1, 2, and 3. [s. 324]