The volume of a **frustum** of a cone, for instance, can be expressed in terms of certain magnitudes by a certain formula; but not only will there be some error in the measurement of these magnitudes, but there is not any material figure which is an exact cone.

**FRUSTUM** (Latin for a "piece broken off"), a term in geometry for the part of a solid figure, such as a cone or pyramid, cut off by a plane parallel to the base, or lying between two parallel planes; and hence in architecture a name given to the drum of a column.

19 the blast orifice B is set much lower, and the steam is discharged through a **frustum** of a cone set in the upper part of the smoke-box into the short chimney.

Hence the area of an ellipse whose axes are 2a and 2b is Trab; and the volume of an ellipsoid whose axes are 2a, 2b and 2c is t rabc. The area of a strip of an ellipse between two lines parallel to an axis, or the volume of the portion (**frustum**) of an ellipsoid between two planes parallel to a principal section, may be found in the same way.

This pulley has fixed to one side, and concentric with it, a short **frustum** of a hollow cone.

This **frustum** is made always to turn along with the shaft by being fitted on a square portion of it, or by means of a rib and groove, or otherwise, but is capable of a slight longitudinal motion, so as to be pressed into, or withdrawn from, the hollow cone by means of a lever.

At a small distance from the pulley the shaft carries a short **frustum** of a solid cone accurately turned to fit the hollow cone.