The ordinary open grate is too familiar to need any description, but it is wasteful of fuel to a degree that could only be tolerated in a mild climate where fuel was cheap. As a matter of fact, only some 10-12 per cent. of the heat generated in an open grate is utilized, the remainder going up the chimney. But this very fault is in one sense a virtue, in that it performs the ventilation of the apartment in an eminently satisfactory manner. By the addition of a contrivance for regulating the combustion in an open grate, the fuel consumption is much reduced, the combustion is rendered more perfect (diminishing or preventing smoke), the radiated heal is much increased, while the appearance of an open grate is retained, though it is in reality converted into an open stove.