22S

TANKS AND GAS-HOLDERS.

method would be impracticable, as when a cast-iron tank stands above the surface of theground, and when the tank, and consequently the receivers or siphons, are at so great adepth that the condensed fluid cannot be pumped up conveniently, but that condition rarelyoccurs. In brick tanks of the ordinary depths there seems no objection to the plan, and theold Birmingham Gas Company have adopted it in all the new gas-holders they have erectedduring the last twenty years.

The purpose of having separate outlet and inlet pipes to each gas-holder is, first, to mixthe gas before it is distributed, and thus prevent the inequality in its illuminating powerthat might occur were the gas to flow directly from the station-meter to the street mains;and, secondly, to enable any particular gas-holder to be filled, or emptied, or shut off, asrequired. Mr. Cathels has introduced an alteration in gas-holder connections, by means ofwhich these objects may be accomplished with a single pipe in each gas-holder. To dothis, he applies one of his fourway disc valves, noticed at p. 209, to every two holders, in themanner shown in the accompanying woodcut, Fig. 79, in which two valves are representedconnected to four holders ; two of which are filling, and two are supplying.

Fig. 79 .

r^ajh

House.

OF VALVE OR

FLOOR

Yi

.V

TO COV

s

FROM METER

The advantages claimed for this arrangement are, that the gas is prevented from passingdirectly from the station-meter to the governor as it might otherwise do if one pipe only were