10 



Common Science 



way of telling at a glance 

 how full it was. One of 

 his workmen suggested 

 that he attach a long 

 piece of glass tubing to 

 the side of the tank, con- 

 necting it with an extra 

 faucet near the bottom 

 of the tank. A second 

 workman said, " No, that 

 won't do. Your tank 

 holds ever so much more 

 than the tube would hold, 

 so the oil in the tank 

 would force the oil up 

 over the top of the tube, 

 even when the tank 



FIG. 3. When the tank is full, will the oil was not full." Who was 

 overflow the top of the tube? rifrht ? 



SECTION 3. The sea of compressed air in which we 

 live: Air pressure. 



Does a balloon explode if it goes high in the air ? 



What is suction? 



Why does soda water run up a straw when you draw on 

 the straw? 



Why will evaporated milk not flow freely out of a can in 

 which there is only one hole ? 



Why does water gurgle when you pour it out of a bottle? 



We are living in a sea of compressed air. Every 

 square inch of our bodies has about 15 pounds of pres- 

 sure against it. The only reason we are not crushed 

 is that there is as strong pressure inside of our bodies 

 pushing out as there is outside pushing in. There is 



