Murray's Improventent.—It has doubtless been observed by most of our readers, that the very dense black smoke which issues from the chimneys of steam engines and other furnaces, is not constant ; that it commences at the time of putting on fresh fuer, and continues for a few minutes afterwards. At this time the air finds its way through the fuel with less opposition, and the evolution of dense smoke ceases until the next charge of coals. To supply the requisite quantity of air to burn this black smoke, the late Mr. Murray (the celebrated steam-engine manufacturer of Leeds), devised a very ingenious machine. It is described in a letter addressed to the Editor of the London Journal of Arts, dated February 15, 1821, wherein he observes,—" The most effectual method yet known for consuming smoke, is by the admission of a large quantity of air to the hottest part of the fire, at the time the smoke is bursting from the recent charging of coal The necessary quantity of air to be admitted ought not to be less than may pass through an aperture of four square inches for each horse power that the boiler or fire is equal to ; this will consume the smoke in from three to five minutes, according to the quantity and quality of coal put on at each time,—the times of charging being not more than five times in an hour, nor less than three. The air rushing into the flue is the moving force for giving motion to my new regulating machine, which continues in motion during the consumption of smoke, but no longer." The machine may be thus described, without the drawings given in the work before alluded to It consists of a light fan-wheel, from which proceeds a capacious tube, communicating with the fire-place, and containing a turning valve, which opens or closes the passage. When the fire-door is opened to take in fresh fuel, it discharges (by means of a slip catch connected to the door) a pall, which sets at liberty a suspended weight ; the descent of this, turns a ratchet wheel, which places the turn-valve edgeways against the current, and leaves a free communication between the atmosphere and the upper side of the fire. In this state of rest the machine remains until the fire-door is shut, when the current of air enters the machine, turning rapidly the fan-wheel, which having a pinion on its axis of only one tooth, gives a slight motion to a light spur-wheel of many teeth ; this wheel, through the medium of a catch-rod, and other simple mechanism, gradually closes the turn-valve. The smoke having been consumed, the fire continues burning until a fresh supply of fuel is necessary, when the fire-door is opened, which puts the machine in a state for measuring off the required quantity of air to be admitted to consume the smoke of each charge ; the operation is then repeated.
Prstcharirs Patent.—Mr. William Pritchard took out a patent in 1821 for the same object. He fixed a small cylinder in some convenient place con tiguous to the furnace, with an air-tight piston to rise and fall within it. At the upper end of the piston-rod a chain is attached, which passes over pulleys, and its reverse end is connected to the top of the fire door or air-flue doors, by means of which connexion, when the fire door is raised, the piston descends in the cylinder by its own gravity ; and when the fire door is shut down, the piston rises. On the outside of the cylinder is placed a branchpipe or channel, through which the air passes (as the piston ascends or descends) from the upper to the lower part of the cylinder, and vice versa. In the middle of this branch pipe is a valve or stop-cock, which may be so adjusted as to suffer the air to pass slowly, or by a very small stream, through the channel; by this means the ascent of the piston is retarded, and hence the entire descent, or closing of the fire doors, or air-flues, does not take place, until the air is nearly all expelled from the upper part of the cylinder, allowing time for the requisite quantity of atmospheric air to pass into the air-flues over the fire, for the purpose of con suming the smoke ; the time of closing the doors is regulated, as above, by the valve or stop-cock in the branch pipe.—London Journal of Arts.
Stanley's Patent.—This invention, which we have seen repeatedly and suc cessfully applied, forms a distinct appendage to the front of the furnace. At the upper part of the apparatus is a hopper, containing a supply of small coals adequate to an hour or two's consumption. Through an aperture at the lower extremity of this vessel, the coals drop between two grooved rollers, which revolve in opposite directions, and break those which are too large to pass without reduction between them ; they then fall upon a flat plate of iron, whence they are continually projected by the arms of a kind of revolving fanner, which scatters them evenly over the burning fliel on the grate, where it lies in a thin bed, in order that the air may pass upward through them the more easily. The apparatus is, however, usually adjusted to throw a larger proportion of the fuel near the fire bridge, so that it may lie there heaped up or in a thicker stratum, in order that the small quantity of smoke arising from the fresh fuel in front may be consumed in passing over the bridge.
Chapman's Furnace.—In 1824 Mr. Chapman received a reward from the Society of Arts for a different mode of introducing air into the furnace. He casts the grate bars hollow from end to end, so that they form a series of parallel tubes, which open into two boxes, one placed in front, and the other behind the grate. In the front box, directly underneath the tire door, there is a register to open and shut to any extent, at pleasure ; the other end is con nected with the brickwork, directly under the fire bridge, which fire bridge is made double, with a small interval between, about one inch, the interval to go across the furnace from side to side, and rather to incline forward, or towards the fire door, so as to meet and reverberate the smoke on to the ignited fuel in the grate, which causes it to inflame and become a sheet of bright fire under the bottom of the boiler. By this arrangement it will be perceived, that if the front register is open, or partially so, there will be a at draft of air through it, along the interior of the grate bars, thence into the flue of the fire bridge, and out of the orifice at top, which air will be heated in its passage through the bars before it comes in contact with the smoke, when it will give out its oxygen, and cause it to inflame. Mr. Chapman's mode of supplying the coals to the furnace is also simple and excellent, which will he expl lined with reference to the subjoined engraving. Fig. 1 is a section of the furnace, with a boiler fixed therein ; and Fig. 2 a view of the hollow bars as they open into the box i. a is the boiler; b the fireplace; c the feeding hopper, with a cover d, and its type or turning bottom, having a lever or counterpoise e, means of which the coals are delivered into the fire-place; f is a rake, by means of which the half-burnt coals are pushed forward previously to letting in a fresh charge; g a slit below the furnace door, through which the state of the fire is seen ; i i is an air-tight box, into the back of which the bars open, and in front of which is a register for the admission of air ; k one of the hollow bars, the whole of which are shown in Fig. 2 as they open into the box i above mentioned; / a flue in the fire bridge, through which the air having passed into the box i, and thence through the hollow bars k, enters into the furnace, and consumes the smoke. Hollow bars are said to be more durable than solid.