344

MODERN STEAM PRACTICE.

hopper valve, and re-opens the communication between the twocompartments X and Z. The speed is then accelerated until thebücket arrives near the receiving hopper Y, when it is again retardedbefore the grain is shot out. The motion of the bücket is regulatedby self-acting gear. These bücket elevators are intended to raise thegrain at the rate of 50 tons per hour, but they are capable of beingworked at a higher speed. The chain O of the crane is employedfor lifting the bücket of the elevator; but it has been found expedient,on account of the demands of the traffic, to make the elevators alsoindependent of the cranes, and therefore separate hydraulic cylinderswith their adjuncts have been supplied for working the formen

Trials have been made for lifting grain by means of dredgingmachines, and it has been found that with a dredger 30 feet long50 per cent. of the applied power proved effective. Experimentshave also been made for raising corn by air pressure or suction,and the results obtained are sufficient to prove that this Systempossesses certain advantages over the plan in use; but it is sur-rounded with difficulties and obstructions which must be removedbefore it can be employed with advantage upon a large scale.

Casks, bags, and other merchandise are raised or lowered eitherby hydraulic cradle hoists or by jiggers. There are twelve hydraulichoists of the ordinary construction, each capable of lifting a loadof I ton to the uppermost floor of the warehouses. They are foundalso serviceable in breaking out the cargoes from the fore and afthatchways of a vessel lying with its centre -hatch in line with thecrane or elevator. For this purpose the lifting chain is disconnectedfrom the cradle of the hoist, and led through a snatch block fastenedto some part of the vessel. The twenty single-acting outsidejiggers, originally constructed only for lowering loads by friction,have been supplied with auxiliary hydraulic power for lifting loadsfrom 6 to 7 cwts. Twelve double-acting jiggers, for loads up to10 cwts., have been added in the centre of the warehouses, for liftingor lowering goods to railway waggons; they are so constructed thatthey can be used singly or together, and for lifting or lowering.Both machines may be alternately lowering goods into Waggonsbelow from any of the floors of the warehouses, or by means of thewater pressure they may both be raising goods from the waggonsto any of the floors; or one side of the machine may be loweringwhilst the other is hoisting goods from the hatchways of vessels towhich the lifting chain has been led.