Abstract: A furnace or furnace-and-pot heating system comprises an inner shell, an outer shell surrounding the inner shell to form a duct between the two shells for preheating combustion air flowing down the duct to enter a combustion chamber within the inner shell. A container or pot for heating material such as water or foodstuffs may be supported inside the inner shell and above a combustion zone, such pot to be of diameter to form with the inner shell an annular flue for escape of combustion products. Draft control means are provided to regulate the amount of combustion air entering the combustion chamber.

Abstract: A heating chamber is defined by canted side walls in inverse pyramidal configuration, the base of the pyramid being open for admission of sunlight and the tip of the pyramid being truncated by a bottom plane. The chamber is adapted to positioning with the aperture plane generally normal to the rays of sunlight so that the canted walls may be fully and simultaneously exposed to sunlight. The inner wall surfaces are dull-blackened to enhance conversion of shortwave solar energy to long-wave or infrared energy whereby the walls are heated so as to radiate infrared (heat) energy for transfer of such heat energy to objects or materials which may be positioned within the heating chamber. The chamber aperture is closed by translucent material such as glass for enhancing the heating effect of the black interior wall surfaces. The aperture closure may rest freely over the aperture or may be hinged along one edge for convenience of opening for access to the interior of the chamber.

Abstract: 11. In a torpedo guard, a cable, a series of explosive units strung on the able, and individual proximity fuses positioned on said cable for each of said explosive units, the proximity fuse for any given explosive unit being adapted to fire said given unit upon the approach of a torpedo within a predetermined distance from said given unit.