SILICON. 45 



reader. It is not our intention to write a 

 work on elementary chemistry; we give only 

 such general chemical facts as are required to he 

 known by the farmer, to render the subsequent 

 part of this book fully intelligible. 



ELEMENTS COMBINING WITH OXYGEN 

 TO FORM ACIDS. 



Silicon is never found as such in nature. It 

 was discovered by Humphry Davy, in 1813. It 

 presents the appearance of a brown powder, or 

 of scaly crystals resembling graphite. Silicon 

 when combined with oxygen in the proportion 

 of 53.34 of the latter, to 46.66 of the former, 

 forms an acid known as Silicic Acid, or simply 

 Silica. This acid occurs in nature both free and 

 combined : free, as quartz, flint and pure white 

 sand ; combined, as felspar, serpentine, etc. The 

 salts of silica are termed silicates, as silicates 

 of potash, lime and magnesia. These silicates 

 chemically combined with water are termed 

 hydrated silicates, which are present in all or 

 nearly all soils, and render a most valuable 

 service to vegetation, by storing up soluble plant- 

 food, and dealing it out when required. 



Silica is either crystallized or amorphous. 

 When crystallized, it forms six-sided, trans- 

 parent, colorless prisms, known as rock crystal ; 



