THE PNEUMATIC TANK SYSTEM 83 



pressed so that it exerts great lifting power. Thus when 

 the tank is three fourths full of water the air is compressed 

 to one fourth of its original volume and the pressure 

 becomes four times that of the atmosphere, or four atmos- 



Pneumatic tank system of distribution of water. 



pheres. Such a pressure will easily force water higher than 

 the top of an ordinary house. 



Experiment. To demonstrate the use of the pneumatic tank. 



Materials: An eight-ounce, wide-mouth bottle. Two-hole rubber stop- 

 per. Glass tubes. Force pump. Ring stand. Rubber tubing. 



Method: Invert the bottle and support it on the ring stand. Make a U 

 bend at one end of a four-foot glass tubing. Insert this in the rubber 



