62 LIVING IN AN OCEAN OF AIR 



tube B some of the liquid comes out of B; as the pressure 

 is decreased inside the tube, atmospheric pressure on the 

 surface of the liquid inside the container pushes it up 

 through C. When this liquid meets the current of air 

 from the bulb, it is caught and separated into a spray of 

 finely divided particles which are carried along with the 



How does the liquid rise from C to B? What causes the fine spray above A? 

 What is the use of the valve y ? 



current of air. Many spray-guns for spraying liquids to 

 kill garden insects and house moths work on this same 

 principle, but use a cylinder and piston instead of the 

 rubber bulb to produce the current of air. 



The Air Pump. The hand air pump used to fill bicycle 

 and auto tires has a piston with a leather facing so 

 arranged that when the cylinder is full of air and the piston 

 is pushed in, the air inside is compressed and pushes the 

 leather against the cylinder wall so tightly that none can 

 escape there. The outlet pipe is coupled to the tire stem. 

 There is a valve in the tire stem which allows air to go 

 into the tire but prevents it from coming out. When the 

 air in the cylinder is under greater pressure than the air 

 in the tire, it will pass from the cylinder of the pump 

 into the tire. A basket-ball or a football pump must 

 have a valve because there is no valve in the tube of 

 the ball. 



