Compared with the flash-flue copper, the wheel-flue is a primitive and costly arrangement. It is much less easily heated, and therefore requires more coal than a flash-flue copper, and, moreover, it cannot be cleaned out without taking the brickwork down to get at the flue. Herewith are illustrations of a flash-flue copper. In building the copper, set the door-frame on the second course of bricks and proceed as indicated in the illustrations. Set the slab plate next to the door-frame, 4 in. wide, and bars 12in. long by 9 in. wide will be quite large enough for a boiler of this size, which will boil in half an hour, with much less coal than a wheel-flue, which would take two hours to boil. When flash-flue coppers get choked up at the bottom of the chimney, it is only necessary to lift out the copper, clean it out, replace it, and point round the top with a little lime putty; the copper is then ready for use again. A 6 in. sanitary pipe makes a good and cheap chimney for this size of boiler furnace. It is best to cut either a stone or a firebrick quarrel to fit round the top of the copper, which makes a little projection, and sets the work off a little.

The illustrations represent, respectively, Fig. 1, front elevation; Fig. 2, plan; Fig. 3, transverse section; Fig. 4, longitudinal section.

Fig. 2.

Fig. 3.

Fig. 4. Flash-flue Washing Copper.