68 LABORATORY MANUAL 



Examine the standard barometer. How does the 

 height of the column of mercury in the tube compare 

 with that of the barometer ? The principle upon which 

 each is constructed is essentially the same. The barom- 

 eter is an instrument used for measuring atmospheric 

 pressure. 



Exercise 41. Siphon. 



Object: To demonstrate the action of a siphon. 



Apparatus 



Rubber tubing Battery jars 



Directions: Fill a battery jar with water and place 

 it on top of the desk. Immerse a piece of rubber tubing 

 about 3 feet long into the jar of water. When the tube 

 is filled with water, close one end of the tube by 

 pinching between the fingers. Place a second battery 

 jar on a chair or on the floor below, but near, the first 

 jar. Quickly remove the closed end of the rubber tube 

 and put it into the lower vessel. Release the tube. 

 What happens ? What caused the water to run ? How 

 long does the water run? What causes the water to 

 rise in the first part of the tube ? What pulls it down 

 into the longer arm? 



Instead of immersing the rubber tube in water to fill 

 it, place one end in the jar of water. Then suck the 

 air out of the tube until it is filled with water. Then 

 remove the mouth and note the result. 



Can you suggest any uses for the siphon? 



