MANURES. 83 



hence it is a chemical manure. In other words, pot- 

 ash belongs to both classes described. 



It is important that this distinction should be well 

 understood by the learner, as the words " mechani- 

 cal " and " chemical " in connection with manures 

 will be made use of through the following pages. 



There is another class of manures which we shall 

 call absorbents. These comprise those substances 

 which have the power of taking up fertilizing mat- 

 ters, and retaining them for the use of plants. For 

 instance, charcoal is an absorbent. As was stated 

 in the section on soils, this substance is a retainer 

 of all fertilizing gases and of many minerals. 

 Other matters made use of in agriculture have the 

 same effect. These absorbents will be spoken of 

 more fully in their proper places. 



TABLE. 



MECHANICAL MANURES are those which improve 

 the mechanical conditions of 



CHEMICAL " soils are those which serve as 



food for plants. 



MANURES. 



ABSORBENTS are those substances which absorb and 



retain fertilizing matters. 



Manure may be divided into three classes, viz. : 

 organic, mineral, and atmospheric. 



