290 FUEL AND LIGHT 



consists of two carbons about the size of a lumberman's lead 

 pencil. When the current of electricity is made to pass from 

 one carbon to the other, a bright light is given off. Another form 

 of electric light is the mercury vapor lamp, which consists of a 

 long glass tube exhausted to a high vacuum. The electric cur- 

 rent is carried by the mercury vapor from one terminal to the 

 other and gives off a yellow-greenish light of dazzling brilliancy. 



Electricity is used for heating in the electric furnace, for cooking, 

 and for heating laundry irons. It is serviceable in cities, but not 

 economical in the country except near large electric power plants. 



EXERCISES 



1. Visit the coal dealer and ascertain the price of coal per ton and com- 

 pare this with the cost of wood in your locality. 



2. Compare the cost and efficiency of soft coal and hard coal. 



3. Compare the cost of soft coal and natural gas for fuel, when the 

 gas can be had at the rate of twenty-five to thirty cents per thousand, 

 for two stoves, and sixteen thousand feet of natural gas are used during the 

 month. 



4. Compare the cost of coal and gasoline for a cooking range. 



5. Compare the cost of lighting four rooms for three hours per day for a 

 month by kerosene, gas, and electricity when all three may be had. 



QUESTIONS 



1. Define fuel. 



2. Name the general classes of fuels. 



3. Discuss (a) wood, (6) charcoal. 



4. Describe (a) peat, (6) lignite. 



5. Discuss (a) bituminous coal, (6) cannel coal, (c) anthracite, (d) coke. 



6. Describe (a) water gas, (6) coal gas. 



7. Discuss natural gas. 



8. Discuss (a) acetylene, (6) gasoline. 



9. Give the history of the discovery of petroleum. 



10. Describe petroleum. 



11. Name some of its distilled products. 



12. Discuss alcohol as a fuel. 



13. Discuss (a) candles, (6) electricity. 



REFERENCES 



Physics, Hoadley. 



Chemistry Chapter on Fuels, Wurtz. 



Domestic Science Chapter on Fuels, Lucy L. Wilson. 



Commercial Geography, Gannett, Garrison, and Houston. 



