52 SCIENCE OF HOME AND COMMUNITY 



the water. Why does the water remain in the tube ? Remove 

 your finger. Why does the water fall ? 



3. Fill a tumbler with water. Over the top place a piece of 

 paper and press it down firmly on the rim. Hold the paper 

 on with one hand and invert the tumbler with the other. Re- 

 move the hand from the paper. What keeps the paper up ? 



4. Submerge a piece of rubber tubing about a foot and a half 

 long in a dish of water till the tube is full of water. Pinch one 

 end of the tube with the thumb and finger and bring it out over 

 the edge of the dish into another empty dish placed a little lower 

 than the first. Remove the hand. What makes the water 

 flow? Raise the second dish higher than the first, keeping the 

 end of the tube under water and note what happens. A tube 

 used in this way is called a siphon. 



5. Light a piece of paper and drop it into a pint milk bottle. 

 After the flame goes out, put. a hard-boiled egg with the shell 

 removed in the mouth of the bottle. How do you explain what 

 happens ? 



6. Do these experiments help you to explain the working of 

 a fountain-pen filler and why it is possible to drink soda water 

 by means of a straw ? 



LABORATORY EXERCISE 8 



Purpose. To show how a pump works. 



Apparatus. A small cistern pump or a glass model of a lift 

 pump. 



Directions. Operate the pump and note carefully how it 

 works. Take it apart and examine the various parts. Make 

 a drawing of the pump and explain how each part works. 



Lift pump. If the well is deeper than thirty-two feet, a 

 lift pump is used. In this kind of pump, both valves are in 

 a movable cylinder, which may be placed in a large pipe, 

 within thirty-two feet of the surface of the water. The 

 pressure of the air forces the water up to the cylinder, and 

 from here it is lifted by means of a rod attached to the 

 cylinder at one end and to the pump handle at the other. 



