Hollow COLUMN, that which has a spiral stair-case withinside, for the convenience of ascending to the top; as the Trajan column, the stair-case whereof consists of 185 steps, and is illumined by 43 little windows, each of which is divided by tambours of white marble. The monument, or fire-column, at London, has also a stair-case; but it does not reach to the top. These kinds of columns are also called columnæ coelides, or cochlides.