LIGHT 245 



4. When was petroleum discovered? By whom? Where? 



5. Why do kerosene lamps sometimes smoke? 



6. What kind of incandescent bulbs are most economical? 



7. Why does a carbon filament light bulb become hotter in 

 use than a Tungsten light bulb? 



8. How did the manufacture of cheap glass advance civili- 

 zation? 



9. What is a fuse plug? 



10. Explain how to read your gas meter. Your electric meter. 



