in architecture, that part of a column which lies immediately upon the capital, being the lowest member of the entablature, and so called from its representing the principal beam in timber-buildings. See Architecture.

Over a chimney, this member is called the mantelpiece; and over doors or windows, the hyperthyron.

ARCHIVOLT, in architecture, the inner centre of an arch, or a band adorned with mouldings running over the faces of the arch-stones, and bearing upon the imposts.