WATER SCORPION 316 WATERTOWN initial impact, drives the wheel round, the upper part moving in the direction of the flow^ water. The water escapes below as each partition during the rota- tion of the wheel is turned face down- ward. The breast wheel acts very simi- larly, and is applicable to falls smaller than those for which the overshot wheel can be conveniently used. The upper circumference of the wheel is higher than the feeding channel of the water, which enters at a point usually a little above the center of the wheel. The undershot wheel is used where the momentum only of the current can be utilized, the impact of the water upon the floats forcing the wheel round. There is necessarily a considerable waste of power in the under- shot wheel, which was to a certain extent x-emedied by Poncelet when he introduced curved instead of plane floats. The turbine or vortex wheel is usually horizontal, rotating round a vertical axis. In the original form of turbine, invented by Fourneyron in 1823, water was in- troduced from above into a central cham- ber, from which it radiated through curved radial chambers. From these it was projected on the curved floats of the wheel, which was forced round by the reaction of the escaping water. Though it is from rivers and streams that we derive all the water power which is profitably used, there is no doubt that in the tides we have a great and remark- ebly constant source of energy, if it could be utilized. Suggestions have not been wanting as to methods for utilizing this energy, but as yet nothing practical has resulted. WATER SCORPION, the popular name of Nepa, a genus of hemipterous insects, the species of which inhabit ponds, etc. Some of them are powerul insects, tv70 or three inches in length. They receive their popular name from the scorpion-like form of the forelegs, with which they seize their prey. WATERSPROUT. a remarkable phe- nomenon occurring for the most part at sea, but occasionally on land, though generally in this latter case in the neigh- borhood of water. A waterspout at sea ia usually formed in the following manner: A dense cloud projects from its center a body of vapor, in form some- thing like a sugar loaf with the point downward. This cone is agitated by the wind till it assumes a spiral form, and gradually dips more and more toward the sea, where a second cone is formed having its point upward. The clouds above and the water below are violently agitated by the physical influences at work. Suddenly the descending and as- cending cones of water or vapor meet in mid-air, and form one united pillar which moves onward vertically in calm weather, but obliquely to the horizon when acted on by the wind. The junction of the two cones is generally accompanied by an electric flash. After continuing in this form for a short time the waterspout bursts, in some cases with terrific violence, and to the destruction of any- thing in the vicinity. Many a ship has been overwhelmed in this manner, and sunk in a moment with all on board. In November, 1885, five vessels were de- stroyed by a waterspout in the harbor of Tunis. Waterspouts on land are cones or pillars of vapor descending from the clouds. Land waterspouts are usually very destructive in their effects. On Aug. 30, 1878, the town of Miskolcz, in Hun- gary, was destroyed by a waterspout with considerable loss of life. These phenomena are, however, more common in India than in Europe. One which occurred at Dum-Dum, near Calcutta, was ascertained to be 1,500 feet in height, and it deluged half a square mile of territory to a depth of six inches. The cause of these phenomena has been assumed to be (1) electricity; (2) vortical motion; or (3) a combination of these causes. M. Weyher has, however, succeeded in producing them artificially, and his method shows that vortical mo- tion is the great factor in the production of waterspouts. By means of a rotating tourniquet placed over cold water, an aerial eddy is caused which draws up the water, in the form of a spout composed of drops, to a considerable height; when the water is heated a clearly defined waterspout is seen. With from 1,500 to 2,000 rotations per minute, the vapor from heated water condenses into a visible sheath, enveloping a clearly defined and rarefied nucleus, conical, and tapering downward. As in natural marine spouts, water drops are carried up and thrown out beyond the influences of the upward current. WATERTOWN, a towm of Massa- chusetts, which includes several villages, in Middlesex co. It is on the Charles river, and on the Boston and Main© railroad. It is chiefly a residential suburb of Boston, but has also impor- tant industries, including the manufac- ture of automobiles, rubber goods, stoves, soap, fui'naces, etc. It has a public library and is the seat of a United States arsenal. The town was settled and incorporated in 1630. Pop. (1910) 12,875; (1920) 21,457. WATERTOWN, a city and county- seat of Jeff'erson co., N. Y. ; on the Black river, and on the Boston and Maine rail- road: 69 miles N. of Syracuse. The
