2. THE SOIL AND SOIL WATER. 



Illustrative material: An oil lamp, a narrow-neck bottle, two 

 other bottles, and some candle wicking. 



Prepare the soil lamp, Figure 5, by filling a small, narrow- 

 neck bottle about one-third full of kerosene oil, and then filling 

 the bottle to the top with small fragments of dry earth. If the 

 oil does not saturate the earth to the top, add a little more oil. 



Prepare the experiment shown in Figure 6, using a small lamp 

 wick or candle wicking. Add water to the left hand bottle, and 

 wet the wick before putting it in place. 



Oil and the Lamp Wick. In a lighted oil lamp, the 

 oil passes upward through the wick as fast as it burns. 

 The oil passes through the wick because the wick contains 

 a number of small spaces or pores 

 that connect with one another. It 

 would rise through almost any very porous 

 substance as a sponge, a piece of blotting 

 paper, a piece of brick, or of porous 

 earth. 



Dry Earth as a Wick. Figure 5 shows 

 a lamp made of a bottle filled with dry 

 earth, which answers for the wick. The 

 oil rises through the earth because 

 the earth is porous. It creeps from 

 one particle of the earth to another at the 

 FIG. 5. Earth points where the particles touch one an- 

 other. The larger the particles are, after 

 they pass a certain size, the slower will the oil rise, because 

 the points where the particles touch are fewer. 



13 



