A cylinder is a solid having as bases two equal parallel surfaces bounded by curved lines, and as its lateral face the continuous surface generated by a straight line connecting the bases and moving along their circumferences. The bases are usually circles and such a cylinder is called a circular cylinder, Fig. 77.
Fig. 77. Cylinder.
Fig. 78. Right Cylinder.
Fig. 79. Inscribed Cylinder.
A right cylinder, Fig. 78, is one whose side is perpendicular to the bases.
The altitude of a cylinder is the perpendicular distance between the bases.
A prism whose base is a regular polygon may be inscribed in or circumscribed about a circular cylinder, Fig. 79.