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nace, between the fire doors and the bridge of the same, and employing two dampers, at or about the bridge, which are opened and closed alternately by certain levers and rods connected with the feeding apparatus." In

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fig 83.

addition, therefore, to acting as an automaton feed-apparatus to supply the furnace with fuel, it insures the combustion of the smoke and economisation of fuel. In fig. 84, we give an end view of a steam-boiler and furnace,

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fig. 84.

with the feeding mechanism applied; in fig. 85, a plan or horizontal section below the boiler; and in fig. 86, a transverse section in front of the bridge of the furnace. "a a is the foundation brick-work supporting the boiler, bb, cc the dead plate' of the furnace, dd the fire-bars. e is the main driving-shaft, to which motion is communicated (by the engine) by a strap passing round the pulley é at its upper-end, or by any other convenient means. Upon the main driving-shaft e is a pulley f, which, by means of the cross-belts g and n, drives alternately the shaft i of the right-hand feeding-apparatus, and the shaft j of the left-hand feeding apparatus. These shafts have each a fast and loose pulley at the upper-end; and the requisite shifting of the straps from the fast on to the loose pulley is effected

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in the following manner: A small crank k is caused to revolve by means of a worm on the driving-shaft e, actuating the worm gearing 1; this crank k has a lever attached to it, furnished with two studs, m and n, which, as the crank revolves, causes the strap lever o to vibrate, and throw one strap on the loose pulley, and the other on the fast one, thus alternately setting in motion and stopping each feeding apparatus. It will be seen in figs. 85 and 86, that there is a partition-wall p in the furnace, reaching from the fire-bars to the bottom of the boiler; and extending from the bridge about half way to the fire-doors; and that there are two dampers q and r behind the bridge of the same, one of which is open and the other closed. The dampers are connected to the strap lever o by cranks and levers, so that when one side of the feeding-apparatus is supplying fuel to the fire, the damper upon that side is closed, and the damper on the other side open, and vice versa. In the drawings the right-hand feeding-apparatus

of the furnace, and will thereby be consumed. It will be evident that, when by the revolution of the crank k, the feeding-apparatus and damper on the other side of the furnace are brought into action, the passage of the

is represented at work, and that upon the left hand as stationary. The right-hand damper being closed, the smoke, &c. from the fresh coal will have to pass round the partition-wall p, and over the fire at the left hand

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smoke will be reversed." The fuel is supplied to the hopper z, and is gradually spread over the furnace-bars from the centrifugal force generated by the revolving discs or plates.

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As a conclusion to the present division of our work, we give drawings and description of a high-pressure boiler with improved fittings, for which

fig. 88.

we are indebted to the courtesy of Mr. William Johnson. Fig. 87 is a "longitudinal section" of boiler, fig. 88 a "plan," and fig. 89 an "end elevation." The boiler of which these are drawings, is that adapted to the engine on the double cylinder principle which we have illustrated in figs. 38, 39.

The class of boilers of which this is a good example, are considered by a competent authority to possess numerous features of economy and safety in working; and as affording an example of what a good high-pressure boiler should be, we give it here. The length of boiler is 22 feet by 7 feet 4 inches diameter; it has two internal cylindrical flues, in the entrances to

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which are placed the furnaces 62 feet long by 3 feet wide. The flues are each three feet in diameter for a length of 12 feet from the front, after which they taper off to 2 feet 8 inches, as seen in the longitudinal section fig. 87, and by the dotted lines in the plan. The whole of the taper of the flues is given in the inside edges; this admits of a greater space between the two, for the entrance of a man to clean and repair. These flues act advantageously as longitudinal stays to the flat ends of the boiler; but as the points of connection are below the centre of the ends, the upper portions are stayed from the top of the shell by strips of boiler plate a a, 12 inches broad and inch thick, and riveted at each end by angle irons. The arrows in the plan point out the direction of the current of flame, &c. The flame from the internal flues returns back by the side flues bb, thence passing by the side openings c c in the brick division into the separate bottom flues dd, running beneath the whole bottom of boiler, finally joining the main

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