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Rh efficiency of the Francis turbine being in this case 86% at full load and 77% at half load.

. 7.—Jonval Turbine. A recent form of the Jonval turbine is shown In fig. 7 This turbine was designed to give 1250 H.P. with a fall of 25 ft. and an efficiency of 77%. It is fitted with a suction pipe and a circular balanced sluice for admitting and cutting off the water-supply. The wheel is 12 ft. 3 in. in diameter, and has a speed of fifty revolutions per minute, and the power generated is transmitted through bevel-gearing to a horizontal shaft from which the power is taken

off for various purposes. When complete the turbine weighed about 140 tons. There is a regulating arrangement, by which one half of the guide-passages can be shut off in pairs from the water and at the same time air is freely admitted into these unused passages by pipes which pass through the hinges of the controlling shutter. Tests of a turbine of this slow-moving type showed an efficiency of 82% at full gate and one of 75% when half of the passages in the guide-blades were closed by the shutters, as described above.

As an illustration of the use of water-power, even at a considerable distance from a town, the case of Lausanne may be described The town has secured the right of using a waterfall of 113 to 118 ft. high, by impounding the Rhône near Saint Maurice. In dry seasons year 14,000 H.P. The plant in 1902 consisted of five turbines having horizontal axles, and each developing 1000 H.P. when running at 300 revolutions a minute. They drive electric generators, and the current so produced is taken at a pressure of 22,000 volts on overhead wires a distance of 35 m. to Lausanne, the loss being estimated not to exceed 10% in the long transmission. Near the town is a station for reducing the voltage, and current is distributed at 125 volts or lighting purposes and at 500 volts for use on the tramways and for other power purposes.

.—For further information concerning the construction and employment of water motors, the reader is referred to the following papers and textbooks:—''Proc. Inst. Mech. Eng.'' (1882), p. 119 (1889), p. 350 (1895), p. 353. (These papers contain full accounts of recent forms of lifts.)—Engineering, vol. lxvii. pp. 91, 128, 160, pp. 391-767. “Governing of Water Wheels.”—Proc. Inst. Civil Eng., vol lxxxvi. p. 60 “Mersey Railway Lifts”; vol. xciii. p. 596, “Experiments on Jonval and Girard Turbines at Alching”; vol. xcvi. p. 182, “Hydraulic Canal Lifts”; vol. cii. p.154, “Keswick Water-Power Electric Station” vol. cxii. p. 410, " Hydraulic Works at Niagara”; vol. cxviii. p. 537, “A 12-Mile Transmission of Power Generated by Pelton Wheels” vol. cxxiii. p. 530, “The Pelton Water Wheel”; vol. cxxiv. p. 223, “The Niagara Power Works”; vol. cxxvi. p. 494, “The Rheinfelden Power Transmission Plant”; vol. cxli. p. 269 Electric Transmission Plants in Transvaal, " p. 307, “Turbines” vol. cxlii. p 451, “Electrical Installations at Lausanne”; vol. cxlv. p. 423, “Water Power at Massena”; vol. cxlvii. p. 467, “Some Large Turbine Installations.”—Wood, Theory of Turbines; Bovey. Hydraulics; Björling, Hydraulic Motors; Blaine, Hydraulic Machinery; Bodmer Hydraulic Motors; Unwin, “Water Motors” (Lectures on Hydro-Mechanics, Inst. Civil Eng., 1885)

WATER-OPOSSUM, or (Chironectes minimus), the single representative of the genus. This animal is distinguished from other opossums by its webbed hind-feet, non-tuberculated soles, and peculiar coloration. Its ground colour is bright grey with four or five sharply contrasted brown bands passing across Its head and back, giving it a very peculiar mottled appearance; the head and body together are about 14 in. long, and the tail measures a little more. It is almost wholly aquatic in its habits living on small fish crustaceans and other water animals; its range extends from Guatemala to southern Brazil.

 WATER POLO, a game which has done much to advance swimming in popular favour and to improve the stamina of swimmers. It is played either in a bath or open water, the teams consist mg of seven a side. The field of play must not exceed 30 yds. or be less than 19 yds. in length, and the width must not be more than 20 yds. The ball used must be round and fully inflated, and must not measure less than 26, nor more than 28 in. in circumference. It must be waterproof, with no strapped seams outside, and no grease or other objectionable substance placed on it. The goals must be 10 ft. in width, with a cross-bar 3 ft. above the surface when the water is 5 ft. or over in depth, and 8 ft. from the bottom when the water is less than 5 ft. in depth; in no case must the water in which a game is played be less than 3 ft. Goal nets are used in all important matches The duration of a match is supposed to be 14 minutes, seven minutes each way. The officials consist of a referee, a time-keeper and two goal scorers, the first-named official starting the game by throwing the ball into the centre of the bath A goal is scored by the entire ball passing between the goal posts and under the cross-bar.

The players have to place themselves in a line with their respective goals, and are not allowed to start swimming to the centre of the bath until the word “Go,” is given. They are usually divided into 3 forwards, 1 half-back, 2 backs and a goalkeeper. To the fastest swimmer is usually assigned the place of centre-forward, and it is his duty to make all headway possible so as to reach the ball before the opposing forward of the other side, then pass rapidly back to the half or one of the backs and swim on to within close proximity of the opponent's goal and wait for a pass. The other forwards should rapidly follow him up and each man carefully shadow one of the opposing side. In handling the ball only one hand may be used, for to touch the ball with both hands at the same time constitutes a foul, as also does the holding of the rail or the side, during any part of the game, the standing on or touching of the bottom of the bath except for the purpose of resting, interfering or impeding an opponent in any way, unless he be holding the ball, holding the ball under water when tackled, jumping from the bottom or pushing off from the side (except at starting or restarting) in order to play the ball or duck an opponent, holding, pulling back or pushing off from an opponent, turning on the back to kick at an opponent, assisting a player at the start or restart to get a good push off, throwing the ball at the goalkeeper from a free throw or refusing to play the ball at the command of the referee after a foul or the ball has been out of the field of play. Dribbling or striking the ball is held to be not holding, but lifting, carrying, pressing under water or placing the hand under or over the ball when actually touching, is holding; dribbling up the bath and through the posts is permissible. There is a penalty area, 4 yds. from each goal-post, and the imaginary line across the bath is not allowed to be passed by the respective goalkeepers, otherwise they commit a foul. They may stand to defend their goal, touch the ball with both hands or jump from the bottom to play the ball, but in all other respects the same rules as to fouls apply to them as to other players. In any case they are not allowed to throw the ball beyond half-distance. If they do so the opposing side is awarded a free throw. For fouls which the referee considers to have been committed wilfully there are very severe penalties, and those guilty of them are ordered out of the water until a goal has been scored, thus for the time being crippling the side. Deliberately wasting time, starting before the word “Go,” taking up a position within 2 yds. of the opponent's goal, changing position after the whistle has blown for a free throw or other similar stoppage of play, or deliberately splashing an opponent in the face, are all held to be wilful fouls. Whenever the whistle blows for fouls the players have to remain in their respective places until the ball has left the hand of the player to whom the free throw was awarded. A player who has been wilfully fouled within 4 yds. of his opponent’s goal line is given a penalty throw, and the consequence is that a close match is often won by reason of a player deliberately breaking the rules when his goal is hotly assailed. In ordinary fouls the ball must touch another player before a goal can be scored, but in penalty throws it need not. Any player throwing the ball over his own goal line concedes a corner throw to the other side, but if an opposing player sends it over it is a free throw for the goalkeeper. After each goal is scored the players return to their respective ends, waiting for the word “Go,” and at half-time they are allowed a rest of three minutes, during which they leave the water. Fouls, half-time and time are declared by whistle, and goals by bell.

The game requires careful practice of smart and scientific passing, side and back-handed throws, and accurate shooting. For this purpose “throwing the water-polo ball” contests are commonly held by the leading clubs, who also engineer competitions on points for shooting at goal.