36 CHEMISTRY, GEOLOGY 



Pig. is. of soil to redness, 



on a strip of sheet 

 iron (see Fig. 

 15). over a lamp. 

 The soil first 

 x black ens, proving 

 the presence of 

 > carbon ; and, as 

 the carbonaceous matter burns away, the soil 

 becomes a gray -brown, or reddish color. (See 

 Appendix, 21.) 



The organic part is obtained from roots and 

 stems of decayed vegetable and animal matter, 

 and from dung and other manures. In peaty 

 soils, the organic part forms, often, three-quar- 

 ters of their whole weight ; but in rich and fertile 

 land it is not often more than from one-twentieth 

 to one-tenth of their weight. 



In our country, soils which do not contain a 

 full proportion of organic matter cannot yield 

 good crops. A rich soil should consist of at 



Questions. How can we prove that soil contains two 

 kinds of matter ? Which burns away ? Which part is not 

 consumed ? Whence does soil obtain its organic matter ? 

 What is its quantity in peat lands ? What in good soil ? 



