Chap. XXI.
LOCOMOTIVE ENGINES.
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chambers above the cylinders, in whichthe pistons work ; the uppermost rod,which passes longitudinally through thechamber of the boiler, where the steamis confined, has n handle at the end,which, when turned by the conductoror engine-tnan, moves the two discsalternately backwards and forwards,which cover the aperture of the twosteam pipes; and this can be easilyeffected. The discs being fixed upona horizontal rod, the cylinders can beeither opened or closed at pleasure :it is important that these discs shouldpress against the mouth of the pipes,which is partly effected by the steamand partly by spiral springs.
Safety-Valves -The boiler has two
safety-valves: their forms vary; themitre valve, when shut, prevents thesteam from escaping, and it remainsclosed as long as the steam is above thecommon pressure of the atmosphere,during which time it cannot escape:above the spiral spring is a plate at-tached to a perpendicular spindle, whichpasses through the top of the valve,where it has a screw-thread and nut;when this is turned it presses againstthe spring, and by forcing it downwardsopens the valve, and allows the steamto pass off; any pressure may be putupon this valve, and when the steam isbelow that pressure, the attendant uponthe engine observes the steam escape, andis then assured that it has not the re-quisite elasticity.
The Water Gauge , attached to theboiler, is for the purpose of ascertainingthe height at which the water stands ; buton the side of the boilers, which when t
generally a small cock is placed at various heightsurned indicates the level of the water. A glass
REGULATOR BOX.
Fig. 2045.
Fig. 2014.
REGULATOR.