Page:Popular Science Monthly Volume 3.djvu/313

Rh oven, hot-plate, and front of the fire. For this reason, the combined apparatus can never be so economical in fuel as separate apparatus; while, however, apparatus of this class, if not very carefully worked, waste fuel, they, to some extent, save trouble to the cook.

I have already mentioned several points of detail where fuel could be saved in our kitchen-ranges, viz., by great attention to the close fitting of the ash-pit and fire-grate doors, the use of double covers to saucepans and boilers, the use of sand on the hot-plate to prevent the escape of so much heat from that part; and, beyond these, an important point in securing economy is the separation of those culinary processes which require different gradations of heat. The three main parts of the ordinary cooking apparatus are the oven for baking and roasting, and the boiler, and the hot-plate. If the boiler is to be of the form most effectual in saving fuel, the flame and gases from the fire should play under and round every part of it; the water should be kept at something under 212°, so that the gases, after leaving the boiler, may not enter the flue much above that temperature, and, inasmuch as that is a higher temperature than is necessary for the purpose of producing a sufficient draught in an ordinary chimney, the heat in these gases should be still further utilized. In the first place, they should be used to warm the water which will be required to replace what is drawn off from the boiler; and, in the second place, an economy can be obtained by employing the gases, which pass off into the chimney at a temperature above what is required for creating an efficient draught, to warm the air supplied to the fire for purposes of combustion. The experiments which I have made on the supply of warmed air to feed the fire have, unfortunately, not been worked out sufficiently to enable me to give them in a clear form with exact results; but an economy of from six to nine per cent, might be obtained from this source.

Then, as regards the oven. The baker's oven, of fire-brick, in which the fire is made inside the oven, and the whole heat retained in and reflected back from the sides and top and bottom, is a very economical instrument when in continual use. With iron ovens, attached to a kitchen range, the case is different. An oven which roasts requires a temperature of from 400° to 450° at least. Therefore, to maintain this temperature, the gases must pass off into the flue at a temperature even higher; when the oven is a roaster, a considerable volume of air is being continually passed through it to carry off the steam from the meat. This air, if admitted cold, as is the case with many ranges, acts so as to cool down the interior, and therefore additional fuel has to be consumed to counteract this cooling-down process. Now, however good may be the conducting power of the material used for ovens or boilers, a coating of soot diminishes the conducting power very rapidly, and consequently the temperature of the flue conveying heat to the oven will always exceed that of the inside of the oven. It is,