HISTORY OF LIGHTING 



101 



Kerosene is another chemical compound contain- 

 ing the elements carbon and hydrogen. They unite 

 with oxygen from the air to form carbon dioxide and 

 water. As in the candle not all of the carbon is oxi- 

 dized. The particles of unburned carbon are heated 

 to glowing as they pass through the flame and give 

 off light. If the wick is kept well trimmed and never 

 turned too high, and the air holes of the burner are 

 kept open and clean, nearly all of the carbon is burned 

 before escaping from the flame. This makes the kero- 

 sene lamp much more efficient than a candle. 



A more modern type of kero- 

 sene lamp is shown in Figure 

 147. This lamp has a cylindrical 

 wick instead of the flat one found 

 in the common kerosene lamp. 

 Another difference is that air is 

 supplied through the base of the 

 lamp and is carried up to the 

 burner through a tube in the cen- 

 ter. This lamp provides better 

 light than the flat-wick type. 



Exercise. When a kerosene 

 lamp is first lit, a thin film of va- 

 por forms on the inside of the 

 globe and then disappears. Know- 

 ing the composition of kerosene 

 from your reading, establish a 

 reasonable cause for this. Why 

 does the film of vapor soon dis- 

 appear? Would you expect this 

 FIG. 147. CENTER DRAFT fil m to leave first from the base or 



KEROSENE LAMP 



fa 



Gasoline is also used for home lighting. In many 

 rural homes where gas and electricity are not avail- 

 able, gasoline has come into use to some extent. For 

 the most part, gasoline does not give as much light 

 as kerosene because the gas that is derived from gaso- 

 line contains very little solid carbon. Most of the gas 

 from gasoline burns with a nearly colorless flame. 

 To overcome this difficulty gasoline lamps are pro- 

 vided with a gauze mantle which is heated to incan- 

 descence by the intense heat of the flame and thus 

 throws out a soft, white light. Gasoline lamps are 

 commonly supplied with air pressure to force the li- 

 quid fuel to the burner. In the operation of this type 

 of lamp it is necessary to pump air into the fuel tank 

 with a pump. 



How is gas used for producing light? As early as 

 1800 gas lighting systems that were designed by Wil- 

 liam Murdock, an Englishman, were used in a few 

 English cotton and woolen mills. In this country at 

 the present time both natural and artificial gas are 

 used. In certain localities of the United States, a 



mixture of gases which is called natural gas comes 

 from the ground. The chief constituent of this gas is 

 methane, a compound of hydrogen and carbon, which 

 burns with a luminous flame. Artificial gas is made 

 from coal. It is sometimes made by passing steam 

 over red-hot coal. This form of artificial gas is called 

 water gas. 



Two kinds of gas burners are employed for produc- 

 ing light. The open flame is the simpler type. It is 

 simply a gas flame burning at the open end of a pipe, 



Gl 



shad 



Tubes in which 

 ir and gasoline 

 mixed 



Valve for filling 

 and for air pump 



FIG. 148. GASOLINE PRESSURE LAMP 



the supply of gas being regulated by a valve in the 

 pipe. As in the candle and the kerosene lamp, some 

 of the carbon in the gas is unburned. The particles be- 

 come heated, glow, and produce a luminous flame. 

 A fishtail flame spreader is frequently placed at the 

 end of the gas pipe to spread the flame so that more 

 light is produced. Gas lighting is greatly improved 

 by use of the gas mantle, invented by Welsbach. The 

 mantle is made of cotton treated with compounds of 

 two rare metals, cerium and thorium. It is placed on 

 the end of the gas pipe. When first lighted the cotton 

 burns away, leaving an ash of cerium and thorium, 

 which retains the appearance and form of the fabric. 

 While this mantle is in the gas flame, it glows with 

 great brilliancy, giving off an abundance of very 

 bright white light. 



How is electricity used for lighting? The first elec- 

 tric lamp was given to the world in 1879 by Thomas 

 Edison after many years of persistent research. Edi- 

 son searched diligently for a substance that could be 

 heated to incandescence by electricity and yet not 

 melt. His first lamp contained a carbon filament made 



