Brick walls are sometimes built hollow, with the view of gaining one or more of the following objects, - (1) economy of materials, (2) equalizing the temperature and preventing damp in the apartment enclosed, (3) providing a flue for the passage of smoke. In Dearn's plan for a hollow wall, the bond is arranged as in Fig. 1330, rows of headers a alternating with rows of stretchers b set on edge, c being closers, and d the hollow spaces. Another plan is shown in Fig. 1331; where some of the stretchers o are 14 in. long, so as to break joint and avoid the use of closers.