**Note:**Do not rely on this information. It is very old.

# Cylinder

Cylinder, the surface formed by a line moving parallel to itself so that it shall always pass through a given closed curve. Usually the curve is a circle, and the line moves at right angles to it. In this case the volume of the cylinder is swept out by a rectangle revolving about one edge. The volume of a sphere is two-thirds that of the cylinder exactly enclosing it.