Losh's Patent.—The entire specification of this gentleman's improvements is inserted in the Repertory of Art., and is deserving of perusal by those who are interested in the subject ; the leading arrancents may however be un derstood by the following extract. The plan arranges " the furnace bars as near as possible under the middle of the boiler, or other vessel's bottom, and to have the aperture or apertures for the escape of the rarefied air and smoke above the door through which the fuel is put in, so that the heated air and gases, by their expansive force and diminished specific gravity, shall pre vent the cold air of the atmosphere from penetrating beneath the bottom of the boiler, in order that the cold air admitted at the door where the fuel is intro duced, shall, in its passage to the chimney, have no tendency to mix with the heated gases until after have ceased to act upon such parts of the boiler as are required to be submitted to their action alone. A division of cast plates, extending from the ends of the bars next to the door, separates the grate-room from the ash-hole and air-duct, and prevents any air from passing into the grate-room which does not pass through the ignited fuel" Another peculiarity in Mr. Losh's arrangements, consists m the employment of two fires, which we will call A and B, with a wall between them, which supports the middle of the boiler across its width. Each of these fires has a common flue, which termi nates in the chimney, and they communicate with each other by means of an open arch under the partition wall; each fire is supplied alternately with fuel ; and the arrangement of the dampers is such, that the gas from the fresh fuel in A shall be compelled to descend, pass under the arch of the division wall, and through the grate bars of the fire B, along with the fresh air that supplies it where the smoke is consumed ; the current of heated air from both, thus united, takes its course around the flue into the chimney. By the time that the fuel in A has burned bright, that in B requires replenishing ; the dampers are then reversed, which removes the current to the chimney ; then the gas from the fresh fuel in B descends under the beforementioned arch up through the grate bars of A, along with the fresh air of supply, and being there ignited, is conducted to the chimney. In this alternate manner the operation of feeding is continually repeated.
Steel's Iteprovensent.—Mr. Steel's fire-place was of a circular form, and made to revolve on an upright axis by a gear connected to its lowest extremity ; motion was also given, at the same time, to a fluted roller, turning in bearings underneath a hopper filled with coals ; this roller broke or crushed the coals to a sufficiently small size, and projected them down an inclined shoot, which dis tributed them over the circulargrate as it turned round, as represented in the annexed section. o o o shows a pressure tubular boiler, set in masonry ; s i is the ring or rim which surrounds the circular grate, made somewhat deeper than the bars, and turning round in an iron trough 3 3, filled with sand, which prevents the air from passing by the rim ; N is a metallic plate to receive the ashes which fall ; D a toothed wheel, turned by any convenient means in the step at C, and in a cross bar at L above. At F is the receptacle for the fuel ; E the breaking and supplying roller, which projects them down the inclined shoot G R, into the revolving grate, which, continually presenting fresh surfaces, the fuel is pretty uniformly distributed thereon. The grate is made to turn in
such a direction that the fresh coals are, immediately after they are deposited, presented to the fire door contiguously situated, where, by the due admission of air, vivid combustion immediately takes place, and the fresh fuel is in bright ignition before more is thrown on the same part, the revolution of the grate being low.
Brunson's Patents.—Mr. Brunton had a patent in 1819 for a revolving fire grate of a similar kind ; but whether Mr. Steel's was antecedent to it (as would appear from the dates given, together with the circumstances), we do not know. Mr. Brunton has, however, the credit of carrying his apparatus into successful use, and of having rendered it very complete. Among many judicious con trivances, may be noticed a revolving scraper, which gathered up the ashes as they fell upon the ash plate. In the following year, 1820, Mr. Brunton took out a second patent for improvements upon the former ; these chiefly con sisted in a mode of raising or lowering the furnace at pleasure, so as to diminish or increase the heat of the boiler as required ; also in a new mode of feeding the fire. The shaft of the circular fire-grate upon which it revolves, is made to pass through a hole in a bearer of iron, built in the brickwork, and receives its support at bottom upon another bearer of iron, which is capable of sliding up and down in grooves, so as to elevate or depress the fire, by means of a rack and pinion, acted upon by a lever or winch. Round the periphery of the cir cular grate is a double rim of sheet-iron, rising up three or four inches, the space between being filled with sand, so that when the grate is raised, another ring of iron, attached to the wall of the furnace, may fit into the groove and form a sand valve, to prevent the passage of air, and i check the transmission of heat. Two or more passages, provided with sliding doors, are made through the brickwork, for the purpose of admitting a current of air to the top of the fire, in order to assist in igniting the smoke, if necessary. The fire feeder is shaped like a hopper, placed over the hole, and the delivery aperture at bottom is capable of contraction or expansion, as may be required. Below this is a plate of iron, placed in an inclined position, and suspended upon pivots for the pur pose of being agitated, in order to distribute the fuel equally upon the grate; there is also a shovel upon rollers, moved by means of a rod and chain actuated by the engine. By the very equal distribution of the coal upon the grate, a thin fire and a sharp draft is maintained, owing to every piece of coal upon the grate being successively exposed to a current of the fire passing constantly in one direction across the grate ; the continual dropping of the coal in minute quantities, instead of opening the door to charge as usual, produces a great advantage in convenience, besides a saving of fuel. The introduction of the coal is likewise completely governed by the steam generated, so as to admit no more for combustion than Is actually needed for the due performance of the work of the engine. The whole apparatus acted independently of the skill or of the carelessness of the fireman. Small coal, of greatly inferior cost to that generally used, answers well with a furnace of this kind, and thereby effects an important saving. A thin fire with a sharp draft produces the maximum effect, because the greater the quantity of oxygen brought into contact with the coal in combustion, the greater heat is obtained.