A LETTER TO THE STUDENT XI 



The second step is procedure : " How shall I go about it 

 to find out ? " 



The third is the condnsion : " What have I found out, or 

 proved ? " 



We should keep a notebook, in which to make a neat, 

 careful record of the experiments we perform. Here is an 

 illustration from a student's notebook, which shows about 

 how the exercises which follow should be recorded : 



EXERCISE 9 



Object. — To learn what effect plowing under a heavy 

 crop of straw has upon the rise of water in the soil. 



Procedure. — I stretched a piece of cheesecloth across the 

 bottom of a lamp chimney and tied it firmly in place. 

 Then I filled the chimney two thirds full of fine soil, added 

 one half inch of finely chopped straw, and added fine soil 

 again until the chimney was full. I put the lower end of 

 the chimney into a pan of water, and watched the moisture 

 rise through the soil. 



I filled another chimney exactly as I had filled the first, 

 except that I left out the layer of straw. I put the lower 

 end of this chimney into the water and watched the mois- 

 ture rise through the soil. 



Conclusion. — The water was drawn up through the soil 

 just as a lamp wick draws up the oil. In the first chimney, 

 the water rose as far as the straw, and there it stopped. 

 In the second chimney, it rose to the surface of the soil. 

 This must mean, then, that when any thing like a layer of 

 straw or weeds or perhaps even clods is plowed under, the 

 " wicks " or tubes ia the soil are broken. In this case, the 

 moisture could not rise to the roots of the young plants, 

 and they would be injured and perhaps die unless there was 

 plenty of rain. 



Exercises, such as this, will very often lead to a desire on 

 your part to perform the same work on a larger scale in the 



