HOW WE GET WATER INTO OUR HOUSES 81 



Method and Results: (a) Fill the U-tube with water. Push the piston 

 three fourths of the way down one side of the U-tube. Place the 

 stopper in the other end, making sure that it is air-tight. Pull the 

 piston to the top of 

 the tube. Result? 

 (b) Repeat (a) and 

 leave the end of the 

 tube open. Result? 



Conclusion : Explain 

 why the water fol- 

 lows the piston to a 

 higher level in one 

 case than in the 

 other. 



Application: If the 

 tube were straight and dipped into a jar of water, would the water 

 follow the piston? Explain. Explain how one can drink soda water 

 through a straw. 



Let us apply this principle to the pump. If the tube 

 is placed in the water as in the diagram and we suck on 



the tube, we can pull 

 the water up. This 

 is because we have 

 removed the pres- 

 sure of the air in 

 the tube and this al- 

 lows the air outside 

 the tube to force the 

 water up the tube. 

 If we now substi- 

 tute for the tube the 

 The lift pump. pump, consisting of 



a piston (see diagram) containing a lifting valve, we see 

 that when this piston is raised the water is pushed into the 

 tube by the weight of the air pressing down on the water 



H.-WHIT. CIV. SCI. IN THE HOME 6 



