1196

THEORY AND PRACTICE OF ENGINEERING.

Rook II.

S \—

Fig. 1800. C1IAPELET, ORLEANS RRIDGE.

The Persian Wheel is a double water-wheel, with float-boards on one side and a series ofbuckets on the other, which are movable about an axis above their centre of gravity : thewheel is placed in a stream, which puts it in motion by acting upon its float-boards: asthe wheel turns, the movable buckets dip in the water, and ascend filled with it: whenthey reach the highest point their lower ends strike against a fixed obstacle, so as to obligethem to empty themselves into a reservoir placed at the top of the wheel.

Drum or Persian Jfheel, employed by Perronet, raised the water 8 feet, but its productvaried according to the different depths at which it worked: when at 1 foot, 12 men,relieved every two hours, gave two turns in a minute, and at each turn 21 cells wereemptied, each containing 1 .V cubic feet, giving for the hour 4320 cubic feet, or 540 muids :

Fig. 186-2.

PERSIAN WHEEL, ORLEANS BRIDGE-

Fig. 1861.

when at 9 inches of depth the same number of men made 150 turns in an hour, but raisedonly 450 muids: when at 6 inches depth, they made 180 turns in an hour, and raised 405muids: when at 3 inches in depth 180 turns were made in an hour, and raised 270 muidsin an hour.

The Scoop Wheel is intended to raise water through a height equal to its semi-diameter,and consists of a number of semicircular partitions, which are open at both ends, viz. atthe circumference and at the centre of the machine : as the wheel turns round, thescoops take up the water, which gradually descends during the rotation of the wheel,till it runs into its hollow axle, which again discharges it into a spout.

Chain Pump, as the Spanish Noria , consists of an endless chain passing round a wheel,and after entering the w'ater to be raised, returns through a tube into a cistern: the chaincarries a number of flat cylindrical pistons, of nearly the same diameter as the tube, onehalf of each piston being received into openings in the circumference of the w’hcel; whenthe wheel is put in motion, the pistons enter the barrel, and pushing the water before them,raise it into a reservoir; and if the wheel is made to go round rapidly, the barrel is generallyfilled with w'ater. Pumps of this description when put in an inclined position will raisea considerable quantity of water ; the inclination in which their power is the greatest is