low and the wick short, the lamp may be made to continue burn- 

 ing by adding water to raise the oil within reach of the wick. 



Substances acting in this way are not fertilizers in the strict 

 sense of that term. They are amendments. 



20. Acid or sour soils are usually unproductive. — ^^They may be 

 made neutral or " sweetened " by means of lime or ashes. The 

 marked benefits sometimes secured by the use of ashes are owing 

 more to the sweetening of the soil than to the addition of plant- 

 food. 



The farmer may determine if his soil is sour by testing it with 

 blue litmus paper. Buy five cents' worth of this paper at the 

 drug store. Press it firmly against a fresh, moist surface of soil. 

 If the paper turns red, the soil is acid ; and the quicker and more 

 completely the color changes the sourer the soil. The test may 

 also be made by inserting the blue litmus paper in water with 

 which the soil is shaken up. A lump of frozen soil may be 

 thawed out in water, and the test applied. An alkali (like lye 

 or lime) will change the reddened litmus back to blue. 



Note. — For further information on fertilizers and plant-food problems, 

 read Voorhees' "Fertilizers." (The Macmillan Co. ) 



Lesson No. 4 will tell how the plant obtains its food from the soil. Let 

 the reader now place a few radish seeds between folds of heavy flannel, 

 and keep them warm and moist. They will then be ready to show the root- 

 hairs when Lesson No. 4 arrives. 



