102 FIRST YE4R COURSE IN GENERAL SCIENCE 



and directed, and great destructive work otherwise. When 

 the steam boiler in a factory bursts, parts of the boiler are 

 sometimes thrown against the walls of the building, knocking 

 down the walls and often causing loss of life. 



In the process of "charging" the steel cylinder from which 

 the tank of a soda fountain is filled, a very great amount of 



compressed carbon dioxide is 

 forced into it. A cylinder that 

 holds five gallons at ordinary 

 pressure may have forty gallons 

 of gas forced into it. This 

 makes a pressure of one hundred 

 and twenty pounds on each 

 square inch of the inside of the 

 cylinder, while on the outside 

 the pressure of the air is only 

 fifteen pounds. If there is a 

 defect in the metal, this tremen- 

 dous inside pressure may cause 

 an explosion of the cylinder. 



111. The Siphon. A siphon 

 is a tube in the shape of an 

 inverted U but with unequal 

 arms. It may be made of glass 

 or of rubber or some other 



FIG. 49. SIPHONS 



The figure represents a jar 

 of liquid with sediment in the 

 bottom and two siphons. The 

 short arm of b is the vertical dis- 

 tance sb. The long arm of 6 is 

 the vertical distance be. 1. 

 Which is the short arm of a? 

 2. What is its length? 3. Under 

 what condition will the liquid 

 stop flowing through b? 4. 

 Through af 5. Which siphon 

 will remove more water? 6. Why 

 is b the better one to use in this 

 case? 



flexible material. It is used to carry liquids from a higher 

 to a lower level over an elevation, as in transferring from 

 one tank or barrel to another. One advantage in its use 

 is that sediment in the bottom of the tank need not be 

 disturbed during the removal of the liquid. 



To set a liquid flowing through a siphon, the air must first 

 be removed from the tube. To do this, fill the tube with 

 the liquid or with water, then cover both ends and invert the 

 tube. Place the shorter arm in the liquid to be transferred 

 and the long arm over the vessel which is to receive the 



