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