OF AGRICULTURE. 223 



action by intermixture of the finely ground 

 mineral with stimulants, such as Peruvian guano, 

 or ammonical salts. 



CHAPTEE VII. 



AN ADDITIONAL DESCRIPTION OF MINERALS. 



To have a clearer understanding of the facts, 

 illustrations and experiments presented in this work, 

 the author thinks it necessary to give a more 

 extended description of the minerals and acids. 



QUART z. 



Quartz is silica crystalized. When broken down 

 into fine grains, it forms sand, and this consolidated 

 or concentrated with silex, lime or oxydes of iron, 

 constitutes sand stones. When silica is fused with 

 bases it unites with them, playing the part of an 

 acid, and forming salts the silicates. 



Talc and Serpentine. Talc is the silicate of mag- 

 nesia. French chalk and soapstone are varieties of 

 talc, and are so soft that they may be worked with 

 the same tools as wood. Soapstone does not fracture 

 in the fire, and is used for lining fire places and 

 grates. It has a soapy, greasy feel, hence its name. 



Augite. Augite is a double silicate of magnesia 

 and iron, its prevailing color is some shade of green. 

 It*forms extensive barren ridges of magnesian rock. 



Horneblende. This mineral is the silicate of mag- 

 nesia, iron and lime. It is of a dark color, and exists 



