[ "4 J 



run with high speed it is better adapted for driving machinery 

 of different kinds. The water is received at the supply pipe 

 (A), whence it is directed by curved guide-blades to the vanes 

 ot the wheel which revolves on a pivot. There is a screw ar- 

 rangement at (C) for raising this pivot. The wheel is rigidly 

 fixed at the bottom of a shaft (B) which communicates the 

 power to the machinery employed. The wheel and the guide- 

 plates are covered by a cast iron case or shell, and the wheel 

 is kept in an exactly horizontal position by a special cover 

 (D). The guide-blades are. also rigidly kept in position by 

 bell-cranks and coupling rods (E, E, E ). The water having 

 exp.ended its force] acting on the vanes at different points, 

 passes out of the centre both above and below. The turbine 

 m ty be placed close to an opening at the bottom of a tank or 

 reservoir of water, or the water may be led by a pipe into the 

 turbine which may be placed in the barn instead of at the 

 foot of the tank. The velocity of the wheel depends upon the 

 height of the fall. But even with a small fall the water has to 

 squeeze its way in different directions between the guide-plates 

 until it reaches the vanesof the wheel which it has to move be- 

 fore it can escape at the centre of the wheel above and below. 

 In the figure the wheel inside the case is barely visible to the 

 right of D, but the guide-plates are entirely hid from view. 



159. The advantages of water-power over other forms 

 of mechanical power are : (n its constancy, (2) its inexpensive- 

 ness and ^3) its simplicity. Water wheels and turbines do 

 not require skill to drive them and they do not readily get out 

 of order. (4) There is also less danger in using this mechanical 

 power than any other. A hurricane may bring down the wheel 

 of an aeromotor; steam may burst the boiler and the fuel may 

 burn the fire-box. Men and animals also do many kinds of 

 damage, and where their work can be wholly or partially re- 

 placed by the mechanical powers, work goes on more smoothly. 

 The importance of having a farm near a flowing stream of 

 water can never be overstated. 



