Perhaps, before going further, it is well to explain the meaning of single and three-heat. Let us suppose that you are operating one of the small disc stoves and that the stove will carry 600 watts of current. If that stove is equipped with a single heat, you will be using the full 600 watts whenever the switch is on. If it is equipped with a three-heat switch, it can be adjusted to 600 watts at full, 300 at medium and 150 at low, which means a great saving in current for most small cooking operations. Two Distinct Types of Heating Elements. There are two very distinct types of electric heating elements or burners, the disc or closed type, and the open-coil type. These two types operate on entirely different principles. The disc stove conveys the heat to the food by the principle of conduction, _i. e._, the heated metal top of the stove in turn conducts the heat to the metal of the dish and thereby heats the food within the dish. The open-coil type of element operates on the principle of radiant heat. The heat rays from the element are focused on the dish in which the food is being prepared. In the former style burner, sufficient time is required to heat the metal top of the stove before the heat can be utilized, while in the latter, the heat is almost instantaneously effective. Below the coils of the radiant type of grills and heaters shown in this section is placed a highly polished, nickeled disc which serves to reflect all the heat units that are directed downward, back to the dish in which the food is being prepared, thereby utilizing a maximum of the heat units produced. One very distinct advantage in the open-coil over the disc type is that in the former practically all the utensils found in the average home can be satisfactorily used, granite and enamel-ware being especially desirable, while in the disc-type stoves, it is necessary to have dishes with smooth, clean bottoms and that they fit very closely in order to make metallic contact over the entire surface.