A fire is set beneath it, and flues constructed of brickwork encircle it, so as to keep the flame and smoke in contact with the boiler for a sufficient time to absorb the heat.

Mr. Brunel's father, when he constructed the Thames Tunnel, lined it with brickwork foot by foot as he went on, and that lining sustained the heavy weight of the bed of the river and the river itself.

Q.How should the brickwork setting of a wagon boiler be built?