Fig. 22.—A disk electric stove. Courtesy of Landers, Frary and Clark.
Oven thermometers.—A thermometer is furnished set in the door of many ranges. While these are guides after one has learned to use the oven, they are not really accurate by scale. For exact work in testing oven temperature, a hole must be bored in the side of the oven, and a chemical thermometer inserted, protected by asbestos and metal.
Simple tests for oven temperature will be found in Chapter XI.
EXERCISES
1. Why is the question of the cost and kind of fuel important?
2. What is the difference between hard and soft coal? Between red and white ash?
3. Why are certain fuels in more common use than others?
4. Explain the advantage of gas over coal. Over kerosene.