HYDRAULIC PILE DRIVER. 1 43

Gear ” as applied to the Mikado (3000 tons). The apparatusconsists of two hydraulic single cylinder engines AA (figs. 1and 2), with rams 4f inches diameter and 19-inch stroke,coupled together and working in opposite directions. They areconnected by slide-rods B, from the boss C to the weigh-shaftlever D. Water is admitted to either of the cylinders byopening the slide-valve E by the handle F, which is centredat G, and has a detent rod and quadrant H. The reversinghandle F is connected to one end of the short double leverK, the other end of which is moved by a connecting-rod froma stud point J on the back of the weigh-shaft of the mainengines. The slide-valve spindle is attached to the doublelever K at an intermediate point. When water is admitted tothe lower cylinder by a downward movement of the reversinghandle, the slide-valve is raised, and the hydraulic rams aremoved in an upward direction, carrying with them the weigh-shaft lever D, and reversing the engines. By the same move-ment the stud point J upon the weigh-shaft is lowered, andcloses the valve again, so that the two rams are held fast inwhatever position they may be placed. This counteracting cut-off enables the engineer at once to place the reversing links ofthe main engines at any degree of expansion, and to hold themthere, by simply moving the reversing lever into the desiredposition in its quadrant. The rams follow at once into thatposition and stop there.

HYDBAULIC PILE DEIVER

In the construction of the Alexandra Docks, Hüll, Messrs.Lucas & Aird employed an hydraulic hoisting machine for thepurpose of driving piles. The machine thus utilised consistedof an ordinary grain hoist with the working chain-drumremoved. The monkey chain was worked direct from a ram