HISTORY OF LIGHTING 



99 



FIG. 141 



Does anything happen to the limewater? This is a test for 



carbon dioxide. What are the products of a burning candle ? 



Record the notes of this experiment in your notebook. 1 



Experiment 67. Does oil rise in a wick? 



Try to light a dry lamp wick. Does 

 it burn? Suspend the wick over a 

 glass. Pour kerosene into the glass 

 so that about an inch of the free end 

 of the wick is covered. Does the oil 

 move up through the wick? What 

 is the name of the force that causes 

 the kerosene to rise through the 

 wick? Light the wick and compare 

 the flame with a candle flame. 



Record the notes of this experi- 

 ment in your notebook. 2 



Experiment 68. How does a kero- 

 sene lamp work? 



Examine a common kerosene lamp 

 (Fig. 146). Notice how the wick ex- 

 tends into the bowl of kerosene. How 

 does the kerosene rise to the top of 

 the wick ? How does air get into the 

 flame? What is the purpose of the 

 lamp chimney? Cover the top of the 

 lamp chimney with a piece of glass 

 while the wick is lighted. What happens? Explain. 



Record the notes of this experiment in your notebook. 3 



Experiment 69. What makes a gas flame give light? 

 Attach a Bunsen burner to a gas outlet. Close the air 



opening at the bottom and light the burner. Notice how 

 luminous the flame is. Hold a 

 white porcelain cup or crucible 

 in the flame. The black deposit 

 formed is unburned carbon which 

 glows when heated. 



Now open the hole at the bot- 

 tom of the Bunsen burner and 

 notice that the flame becomes 

 pale blue in color and is almost 

 non-luminous. Hold a white por- 

 celain cup in this flame. Does a 

 black deposit form? 



Light a candle and hold a white 

 object in the flame. What forms 

 on it? What makes a flame give 

 light? 

 Record the notes of this experiment in your notebook. 4 



Experiment 70. How is an electric-light bulb con- 

 structed? 



Secure an electric-light bulb that has a tip on the end. 

 One that is burned out will do for the experiment. Wrap 

 your hand in a towel, hold the bulb under water, and break 

 off the glass tip with a pair of pliers. What happened? 

 Explain. 



1 See workbook, p. 36. 

 1 See workbook, p. 36. 

 * See workbook, p. 36. 

 4 See workbook, p. 37. 



FIG. 142 



Examine the filament inside the bulb. Find out what it 

 is made of. 



Connect a very thin piece of iron wire between the two 

 terminals of a good dry cell. Notice how hot the wire be- 

 comes. This is because the wire offers resistance to the elec- 

 trical current. The filament in an electric-light bulb is so 

 highly resistant to electricity that it becomes white hot with- 

 out melting and gives off light. 



Record the notes of this experiment in your notebook. 5 



OTHER INVESTIGATIONS WHICH YOU CAN MAKE 



1. Make a study of the lives of Thomas Edison and Sir 

 Humphry Davy. 



2. Make a collection of candles, candlesticks, kerosene 

 lamps, gas lights, and incandescent bulbs. 



3. Make a study of the history of electric lighting. 



4. Make a study of the history of gas lighting. 



5. Make a miner's safety lamp. 



READINGS WHICH WILL HELP ANSWER 

 THE PROBLEM QUESTIONS 



How did the people of olden times light their 

 homes? Primitive peoples probably had no other 



Roman Lamp 



Cexnd)e<5, 

 Candlestick 



Frosted 

 Glob 

 Carbon 

 Ff 



Filament 



Electric Ldmps 



FIG. 143. THE DEVELOPMENT OF LIGHTING 



source of artificial light than the open fires they built 

 in their cave homes. Some time later the smoky pine 

 torch which could be carried from place to place was 

 discovered. The next important development was the 

 invention of the lamp filled with fat in which was 

 embedded some form of wick. These lights were very 

 crude and inefficient. They gave off much smoke and 

 ofttimes disagreeable odors. The candle, which was 

 more efficient than any of the preceding devices and 

 was made by embedding a wick in solid fats and later 



5 See workbook, p. 37. 



