Figure 19 shows a well-constructed stove of the usual type. Notice the air space, and asbestos lining around the oven. The burner for heating the oven is at (1). Holes in the sides allow the heated air to pass outside of the oven at (2) and into the oven as indicated by the arrows. The heated current passes out of the oven at the back of the top, and passes out of the stove at (3), where it should be carried away by a pipe into a flue. The heat of the oven burner is also used for toasting and roasting underneath, on the movable rack at (4). The oven burner is lighted by a leader burner at (5). The top burners, five in number, are at (6). Below those is a removable pan at (7). The top of the stove is removable in sections, and the burners are easily removed when cleaning is necessary.
Fig. 19. - A modern gas range.
The gas burner (Fig. 20) is constructed on the principle of the Bunsen burner, which you may have used in the laboratory. There is an opening in the pipe, near the stopcock, which admits the air, that it may mix with the gas, and give the blue flame. If there is not enough air, the flame burns with a yellow color, and smokes. If there is too much air, there is a roaring sound, and the flame "pulls back" and burns with a smoky yellow flame, and disagreeable odor.
There is a valve always to regulate the air supply for each burner. Figure 20 shows a burner removed from the range. (1) is the hollow, star-shaped chamber which gives space for the thorough mixing of the gas with the air. The gas enters from the connecting pipe at (2), the air at (3), and (4) is the valve for regulating the air supply.
Gas ranges of this type are built in different sizes, and with varying arrangements of ovens and hot-closets. An oven above the stove is convenient. Ranges are built also for using either gas or coal. A range of the size pictured, with four large burners on the top, will serve for a family of five or six, if the work is well planned. The oven burner consumes 30 to 40 cubic feet per hour, the top burners 2 cubic feet each, and the simmering burner somewhat less. This is estimated for a burner turned on full.