290 GENERAL SCIENCE 



times that man discovered petroleum, coal, and gas, and 

 learned how to get them out of the earth and use them. 

 During the latter half of the nineteenth century and the 

 beginning of the twentieth century, methods of artificial 

 lighting have progressed by leaps and bounds. The 

 candle was rapidly replaced with the oil lamp, which was 

 at first very imperfect and dangerous because the gasoline 

 could not be removed from the oil and hence lamps would 

 occasionally explode. Improvements were made in the 

 lamp and in the refining of the petroleum until it made 

 an almost ideal light. 



The discovery of natural gas led to the invention of a 

 gas lamp which was used extensively in regions where 



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ACETYLENE BURNER AND FLAME 

 Air enters the openings at B. 



gas was found. Gas lights were more convenient and 

 less expensive than oil lamps. After the discovery of 

 how to make gas out of coal, the gas lamp came into 

 common use wherever coal could be secured at reasonable 

 rates. The natural and coal gases were also used for cook- 

 ing and heating after gas stoves were invented. Acetylene 

 gas, a compound of carbon and hydrogen, is burned in 

 the same kind of lamp as other gases. Vaporized gasoline 

 "is also much used for lighting, being burned in gas lamps. 

 After the invention of machinery that would generate 

 an electric current, electric lights soon came into use. 

 With the improvements that have been made on the first 



