Fig. 1083. Flexible water-main, plan and section: 2 pipes of 15 in. and 18 in. interior diameter, having some of their joints thus formed, conduct water across the Clyde to Glasgow Water-works. Pipes are secured to strong log frames, having hinges with horizontal pivots. Frames and pipes were put together on south side of the river, and, the north end of pipe being plugged, they were hauled across by machinery on north side, their flexible structure enabling them to follow the bed.

Fig. 1084. Air-pump of simple construction. Smaller tube inverted in larger one. The latter contains water to upper dotted line, and the pipe from shaft or space to bo exhausted passes through it to a few inches above water, terminating with valve opening upward. Upper tube has short pipe and upwardly-opening valve at top, and is suspended by ropes from levers. When upper tube descends, great part of air within is expelled through upper valve, so that, when afterward raised, rarefaction within causes gas or air to ascend through the lower valve. This pump was successfully used for drawing off carbonic acid from a large and deep shaft.

Fig. 1085. Aeolipile, or Hero's steam toy, described by Hero of Alexandria, 130 years B.C., and now regarded as the first steam engine, the rotary form of which it may be considered to represent. From the lower vessel, or boiler, rise 2 pipes conducting steam to globular vessel above, and forming pivots on which the said vessel is caused to revolve in the direction of arrows, by the escape of steam through a number of bent arms. This works on the same principle as Barker's mill.

Fig. 108G. Brear's bilge ejector, for discharging bilge-water from vessels, or for raising and forcing water under various circumstances. D is a chamber having attached a suction-pipe B and discharge-pipe C, and having a steam-pipe entering at one side, with a nozzle directed toward the discharge-pipe. A jet of steam entering through A expels the air from D and C, produces a vacuum in B, and causes water to rise through . B, and pass through D and C in a regular and constant stream. Compressed air may be used as a substitute for steam.

Fig. 1087. Gasometer. The open-bottomed vessel A is arranged in the tank B of water, and partly counterbalanced by weights C, C. Gas enters the gasometer by one and leaves it by the other of the 2 pipes inserted through the bottom of the tank. As gas enters, vessel A rises, and vice versa. The pressure is regulated by adding to or reducing the weights C, C.

Fig. 1088. Hoard and Wiggin's steam trap for shutting in steam, but providing for the escape of water from steam coils and radiators. It consists of a box, connected at A with the end of the coil or the waste-pipe, having an outlet at B and furnished with a hollow valve D, the bottom of which is composed of a flexible diaphragm. Valve is filled with liquid, and hermetically sealed, and its diaphragm rests upon a bridge over the outlet-pipe. The presence of steam in the outer box so heats the water in valve that the diaphragm expands and raises valve up to the seat a a. Water of condensation accumulating reduces the temperature of valve; and as the liquid in valve contracts, diaphragm allows valve to descend and let water off.

Fig. 1089. Ray's steam trap. Valve a closes and opens by longitudinal expansion and contraction of waste-pipe A, which terminates in the middle of an attached hollow sphere C A portion of the pipe is firmly secured to a fixed support B. Valve consists of a plunger which works in a stuffing box in the sphere, opposite the end of the pipe, and it is pressed toward the end of the pipe by a loaded elbow lever D as fur as permitted by a stop-screw b and stop c. When pipe is filled with water, its length is so reduced that valve remains open; but when filled with steam it is expanded so that valve closes it. Screw b serves to adjust the action of valve.

Fig. 1090. Another kind of gasometer. The vessel A has permanently secured within it a central tube a which slides in a fixed tube b in the centre of the tank.

Fig. 1091. Wet gas meter. The stationary case A is filled with water up to above the centre. The inner revolving drum is divided into 4 compartments B, B, with inlets around the central pipe a which introduces the gas through one of the hollow journals of the drum. This pipe is turned up to admit the gas above the water, as indicated by the arrow near the centre of the figure. As gas enters the compartments B, B, one after another, it turns the drum in the direction of the arrow shown near its periphery, displacing the water from them. As the chambers pass over they fill with water again. The cubic contents of the compartments being known, and the number of the revolutions of the drum being registered by dial-work, the quantity of gas passing through the meter is registered.

Fig. 1092. Powers's gas regulator for equalizing the supply of gas to all the burners of a building or apartment, notwithstanding variations in the pressure on the main, or variations produced by turning gas on or off, to or from any number of the burners. The regulator-valve D, of which a separate outside view is given, is arranged over inlet-pipe E, and connected by a lever d, with an inverted cup H, the lower edges of which, as well as those of valve, dip into channels containing quicksilver. There is no escape of gas around the cup H, but there are notches b in the valve to permit the gas to pass over the surface of the quicksilver. As the pressure of gas increases it acts upon the inner surface of cup H, which is larger than valve, and the cup is thereby raised, causing a depression of the valve into the quicksilver, and contracting the opening notches b, and diminishing the quantity of gas passing through. As the pressure diminishes, an opposite result is produced. The outlet to burners is at F.

Fig. 1093. Dry gas meter. Consists of 2 bellows-like chambers A, A, which are alternately filled with gas and discharged through a valve B, something like the slide-valve of a steam engine, worked by the chambers, A, A. The capacity of the chambers being known, and the number of times they are filled being registered by dial-work, the quantity of gas passing through the meter is indicated on the dials.