SOILS. I5 



18. The farmer and planter are concerned with 

 only fourteen or fifteen of these elements, because 

 only this number enter into the composition of soil-, 

 generally, and are concerned in the growth of plant*- 

 These are as follows : 



Non-metallic Elements. Metallic Elements, 



1. Oxygen. i. Potassium. 



2. Hydrogen. 2. Sodium. 



3. Nitrogen. 3. Calcium. 



4. Carbon. 4. Magnesium. 



5. Silicon. 5. Aluminium. 



6. Sulphur. 6. Iron. 



7. Phosphorus. 



8. Chlorine. 



To these may be added manganese, iodine, and 

 fluorine, which are sometimes present in minute 

 quantities. 



19. Oxygen is by far the most abundant of the 

 elements. It forms about one half of the solid crust 

 of the earth, eight-ninths of all the water, and one- 

 fifth of the atmosphere. This element is easily pre- 

 pared by heating in a glass tube or flask either mer- 

 curic oxide (commonly called red oxide of mercury), 

 or potassium chlorate. Heat separates the oxygen 

 from these compounds. It can easily be collected 

 in suitable vessels and its properties examined. If a 

 small quantity of manganese dioxide (black oxide of 

 manganese) be mixed with the potassium chlorate, the 

 oxygen will be given off at a lower temperature. (4). 



