DOCK-GATE MACHINERY.

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in the closing ram 011 the other side of the lock, which (by meansof its valve) bas been put in connection with the exhaust. Forclosing the gates, the Operation is reversed. The ram-headsare carried by rollers on tram-plates. This arrangement issimple, and has very few wearing parts. The strain on thechain when the gate is moved is about 10 tons. The gates areopened in a minute and a half.

The illustration only shows the machinery on one side of thelock. The other is precisely similar.

The widest entrances to which hydraulic power has beenapplied are 100 feet at the Canada Dock, Liverpool , at theBarrow Dock, and at Birkenhead .

Sluices for removing mud at the entrances to locks can beconveniently worked by hydraulic machinery. Their move-ment up and down is effected by the application of direct-acting cylinders and pistons attached to the masonry to openand close the paddle against the pressure. A hand-pump isgenerally applied so as to be available in the event of thewater-pressure being accidentally cut off. The combination iseffected by a screw and gearing worked by a rotary hydraulicengine, so arranged that it can be worked by either hand orpower. The sluice cylinders are usually lined, and the rodscovered, with copper. Plate 33 shows an Elswick “Direct-Acting Hydraulic Sluice Machine.” At the Alexandra Docks,Newport , the hydraulic sluices are attached to the gates them-selves, instead of being placed on the masonry.

Lock-sluicing arrangements at dock entrances liave generallyfailed by reason of the scouring action of the water on the mudbeing limited to the mouth of the sluice. Deep holes are madethere, as the scouring force is not operative at any distancefrom the sluice. A solid apron should therefore be carried forsome distance beyond the mouth of the sluice to prevent theforce of the water from disturbing the floor (as it frequentlydoes). The current would then be directed with the best effect,and the formation of the upper eddies, which destroy the sluic-ing power of the water, would be avoided.