100 EXPERIMENTAL GENERAL SCIENCE 



17.j[How does the chimney keep a lamp from smoking? 



18. In a hot-water heating system which pipes do you infer are lower, 

 those which carry the water from the heater or those which bring it 

 back? Why? 



19. The bottom of the ocean, even in the tropics, is known to have a 

 temperature only a few degrees above freezing. How do you account 

 for this? 



20. In what general direction do you infer the water moves at the 

 bottom of the ocean? 



21. When a fire is lighted out of doors, why do the sparks fly upward 

 as soon as it is burning well? 



22. Why do factories which burn coal secure a better draught by the 

 use of tall chimneys? 



23. When the fire is first lighted the stove may smoke. Why? 



