_Open Grate._--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 utilised, 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 au open grate, the fuel consumption is much reduced, the combustion is rendered more perfect (diminishing or preventing smoke), the radiated heat is much increased, while the appearance of an open grate is retained, though it is in reality converted into an open stove. It would not be out of place to explain the cause of draught. After a chimney has been used, the brickwork surrounding and forming it becomes warmed and retains its heat for a very considerable period even if no fire is lighted; this heat is slowly radiated, and warms the air contained in the chimney, rendering it lighter and causing it to rise and flow out at the top; this is immediately replaced by cold air from below, which is warmed and rises as before, and so continues, causing an up current of air to be passing through the flue, its swiftness varying with the heat. The more intense the heat produced by the fire, and the greater the height of the chimney, the more swift is the current of air known as the “draught”; and when once the draught is established it will remain for a very long time without any fire being lighted. A good draught is not to be despised, as can be certified by those who have suffered from the annoyance of a smoky chimney; yet too strong a draught is a disadvantage, as consuming the fuel too rapidly, robbing the fire and apartment of its heat, and causing draughts of another kind, which materially cool the room and tend to cause discomfort; this only applies to the old form of grate, as all or nearly all modern grates have a means of regulating the draught; even the common and old form of grate is provided with a “register” or flap at the back, immediately over the fire (certainly not an economical position for it), through which the smoke passes into the chimney. This flap is provided with the view of having it full open to assist combustion when fire is first ignited, and afterwards partially closing it when fire is established, and so prevent undue loss of heat, but although this “register” is provided with every stove of its kind, _it has not, nor never has had, any means of regulating it_. If the reader has one of these stoves in his residence, as most probably he has, for they are still used in the upper rooms of nearly every building, he can by a simple experiment experience the benefit of regulating this flap. By placing a piece of coal, or stone, or metal, with the tongs, after the fire is