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THE ACCTJMÜLATOK.

THE ACCUMULATOE.

Sir William Armstrong devised this simple means of obtain-ing pressure on a column of water by a weight instead of byelevation. The first accumulator (which is still in daily workat Elswick) has the ram attached to the ground, the cylinderrising and falling. The cylinder is encased with cast ironweights, which are held together by ironhoops. In the usual form of accumu-lator the ram rises instead of thecylinder, as is shown in vertical sectionby fig. 10. A cylinder A contains aram B, upon the top of which isattached a crosshead B', carrying aloaded case CC, which is suspended tothe crosshead by a series of wroughtiron straps bolted to it and also to thecase. The weight placed in the casecan be varied to suit the pressure re-quired, and as the weight rests on thetop of the ram it follows that whateverwater is pumped into the cylinder fromthe engine through the pressure pipe D,will be subject to that pressure. Astop valve E enables the water to becut off. When the ram has risen tothe top of the stroke (and the cylinderis full of water under pressure), it stopsthe engine by means of a chain con-necting with the steam throttle valve of the engine, and waterceases to be pumped into the accumulator. When the ramfalls (owing to the abstraction of water from the cylinder), thesteam throttle valve is opened, the engine works again, andwater is pumped into the accumulator.

The largest accumulator that has yet been made is at Liver-pool. It is 23 inches in diameter, and has a 40-feet stroke.