Rectangular Cupola
This style of cupola is not often met with at this day, the common round or oval one having taken its place almost everywhere. The sides of these cupolas were usually composed of four cast-iron plates which rested vertically on a solid foundation of stone or brick, and were held together by bolts at the corners. The widest plates were about one third longer than the others, and it is one of these wide plates which faces the foundry, being provided with a breast-hole at the bottom, which answers for tap-hole, and furnishes means for raking out when done melting. In order that the greatest quantity of metal possible might be gathered on the bottom before a tap was made, it was customary to pierce each side with several holes about 8 inches apart, one above the other, so that by means of a flexible hose or a sliding pipe the tuyeres might be raised as the metal accumulated, the blast being suspended during the process of raising the pipe and making the lower holes good with suitable plugs. The height of these cupolas was about three times the length of the long side, and the hole was lined with ordinary square fire-brick, the bottom being made with sand as now. See CUPOLA; BREAST-HOLE.