Whatever the type of cooker, there are several underlying principles which must always be heeded in the carrying on of successful fireless cookery: First, all utensils to be used for boiling, pot roasting or stewing must be equipped with tightly fitting covers. Second, any food to be boiled must be cooked for at least ten minutes before putting into the cooker. Third, if radiators are not used the food must be placed in the cooker while still boiling. Fourth, the cooker must be thoroughly cleansed with soap and water, and dried and aired before each cooking process, as, otherwise, the odors of stale food will affect the cooked product. Sixth, when two radiators are used the length of time to be allowed is the same for baking as in a coal range; for pot-roasting or braising a trifle longer. Seventh, without the radiators the time for boiling, simmering or stewing is doubled.

Eighth, foods to be cooked without radiators should be in quantities of at least two quarts, to make possible the retention of heat, otherwise a vessel of boiling water should be put in the cooker at the same time to form the necessary amount of heat.

The Possible Saving of Fuel. The question is often asked whether or not the fireless cooker is really practical. If intelligently used, there can be no doubt about it. From the standpoint of economy in money the saving is considerable, especially when used to supplement a gas or oil range. When gas is eighty cents per thousand cubic feet, for instance, the maximum costs per hour for operating the burners are as follows: a large top burner, 1 1/2 cents; a small top burner, 1 1/3 cents; the oven, 3 cents a burner, or 6 cents when both are used. A good sized pot roast should be cooked on a range from five to six hours. The cost, with the burner reduced almost half, would be from three to four cents. If prepared in the cooker, the cost is reduced to the length of time it takes to heat the radiators. It takes about three cents worth of gas to make medium-sized loaves of bread, yet they can be done in the cooker with no further expenditure than the heating of the radiators. Boiled cabbage with salt pork is a cheap dish when the ingredients are considered, but it becomes decidedly more expensive when the cost of the oil or gas is taken into account. The same is true of casserole dishes, baked beans, coddled apples, old-fashioned baked peaches and apple sauce, or stewed dried fruits and vegetables.

The cost, then, of cooking by the fireless simmers down to the length of time needed to heat the radiators and to carry on any preliminary preparation. The following table is adapted to gas range heat, but in using oil, alcohol, coal or wood equally good results may be obtained by increasing about one-half the length of time for heating the radiators. The most accurate method for testing the heat of the radiators is by a fireless thermometer, but, if one is not at hand, a little flour sprinkled on the stones will give the approximate heat.