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feed-water passes in jet-condensing engines are the sea-injection cock, passing through the ship's side to the rose-plate in the condenser, from which it is drawn off by the air-pump, through the foot-valve, and delivered to the hot well, from whence the quantity necessary is drawn by the feed-pump, and forced through the check-valves into the boiler.

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The above cuts represent a simple method of ascertaining whether a slide-valve is well proportioned or not, and whether the exhaust opens at the right time, too soon, or too late. Disconnect the valve from the rod or yoke, and take two parallel pieces, A A, about one-half inch thick and one inch wide; though the exact width or thickness is immaterial. Let one be the exact length of the valve in the direction of its travel, on which the width of the exhaust opening, C, in the valve-face may be marked by cutting notches with a penknife; then place the other parallel piece on the valve-seat, and mark the width of the steam-ports, B, and the exhaust, D. Then place the one representing the valve, A, in the centre of its travel, as shown in Fig. 1, and observe the inside and outside lap; next place it at the commencement of its stroke, as shown at F, Fig. 2, and observe the amount of exhaust opening.

If it should appear that the valve is well proportioned for the admission of the steam, and that the exhaust opens too late, the difficulty may be remedied by chipping out the exhaustopening in the valve-face; or, should it be found that the exhaust opens too early, it may be obviated by inserting some pieces of brass or copper, and securing them to the valve with some smalltap-bolts, the heads of which may be riveted down; after which the pieces may be filed and scraped down to correspond to the face of the valve.

Pipes.

The principal pipes connected with marine engines and boilers are the main steam-pipe, donkey-pipe, cylinder jacket-pipe, whistlepipe, the steam winch-pipe, ballast engine-pipe, feed-pipes, donkey feed-pipes, donkey suction-pipes, and a hot-well connection-pipe, circulating water-pipes, feed suction-pipes, air-pump discharge, bilge-discharge, bilge-suction, bilge-injection, cylinder drain-pipes, slide-jacket drain-pipes, and steam-jacket drain-pipes, blow-off- and scum-pipes, waste-steam pipe, cooling-pipe, water-service pipes.

The pipes, cocks, and valves used in connection with the locomotive are the arch-pipes, blast-pipes, connecting-pipes, oil-pipes, steam-gauge pipe, blower-pipe, feed-pipes, heater-pipes, lifting-pipe, sand-pipes, steam-pipe, throttle-pipe, blow-off cocks, check-valve, cylinder-cocks, feed-water cocks, frost-cocks, gauge-cocks, heatercocks, mud-cock, pet-cock, safety-valve, slide-valve, stop-cock, stopvalves, and throttle-valve.

The pipes, cocks, and valves used in connection with stationary engines are the steam-pipe, exhaust-pipe, feed-water pipe, blow-off pipe, drip-pipes from cylinder, drip-pipe from heater, steam-gauge pipe, slide, poppet, or rotary steam-valves, globevalves on steam- and water-pipes, check-valves, stop-cocks on blowoff pipe, bib-cocks, drips, etc.

Check-valves are placed on the connections between steamboilers and the pump or injector, by which they are fed to resist the pressure from the boiler.

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The Wells Two-Piston Balance-Engine.

The cut on opposite page represents the Wells Two-Piston Balance-Engine, which, the inventor claims, possesses features in point of efficiency and economy which place it on a par with some of the most improved engines in the country, as it may be run at a much higher velocity, and, in consequence of its greater capacity, is more efficient than any single-piston engine in use at the present day. The weight and momentum of the reciprocating parts being equal in opposite directions, the action is perfect without lead, which results in a great saving of steam; and as the force is applied on opposite sides of the shaft, and both cranks travel in the same direction, the thrust due to a single crank, is avoided. Moreover, because all the force of the steam on the cranks is exerted in torsion, there is no strain on the housing or foundation; hence it requires only a slight foundation. They have been frequently run at a piston speed of 1000 revolutions per minute, without any perceptible jar to the engine or vibration in the building.

It is further claimed that the advantages of high piston speed, and the benefits to be derived from expansion, are more fully realized in this engine; and that the condensation is less than it possibly can be in any single-piston engine. Besides, the weight of these engines is only about one-fourth that of ordinary engines of the same power; and, in consequence of the absence of all vibration while they are working, they can be placed in any room in a building without inconvenience or annoyance, and are peculiarly adapted to yachts and other pleasure boats. The cut on page 234 shows a section of the same engine: A A and B B designate the steam- and exhaust-ports; C C, the piston-heads; D, the middle piston-rod, which works through the middle piston-head; E E, the outside piston-rods; F, the middle connecting-rod; G G, the outside connecting-rods; HH, the middle crank-arms; II, the outside crank-arms; J, the shaft; K shows the line on which the opposing strains are exerted.

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Section of the Wells Two-Piston Balance-Engine.

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