38 SCIENCE OF HOME AND COMMUNITY 



3. Light the wick and keep the chimney off. Fan the flame 

 gently. Put on the chimney. What difference does it make in 

 the flame? Fan the air near the chimney. How does the 

 effect differ from that when the chimney was off ? 



4. Push a piece of cloth up under the burner and cover the 

 small holes on the under side. What happens ? Why ? 



5. The method by which the oil passes up through the wick 

 is called capillarity. A few simple experiments will illustrate 

 this. Put a small tube in water. Compare the level of the 

 water inside with that outside. 



Put some water in a plate and add a little red ink. Place 

 two pieces of glass together and set them on edge in the plate. 

 Separate the two at one edge and insert a piece of toothpick 

 or match. Keep the opposite edges touching by means of a 

 rubber band. Hold the pieces in this position and notice how 

 the water rises between the plates. How do you explain the 

 curve assumed by the water between the pieces of glass ? 



Put the edge of a piece of blotting paper in ink and see how 

 far up the ink will rise. Hold the corner of a lump of sugar in 

 water and note results. 



Gas. The use of gas marks another advance in the 

 methods of lighting. The mantle flames give a stronger 

 light than the kerosene lamp ; and the gas fixtures are much 

 more convenient, as burners can be placed in each room and 

 connected with a common supply of gas. 



Two kinds of gas are commonly used, coal gas and water 

 gas. Coal gas is made by heating coal in an inclosed retort 

 so that it cannot burn. As a result combustible gases are 

 given off. These are purified and finally stored over water 

 in large tanks. Large pipes carry the gas to various parts of 

 the city, and small pipes from these lead to each house. The 

 pressure is kept up by the weight of these tanks, which rise 

 and fall according to the supply of gas they contain. 



Water gas is more commonly used. This is made by 

 passing steam over heated coal. As a result hydrogen and 

 carbon monoxid are formed, both being gases which burn 



