[315] SCIENTIFIC MANUAL. 2 



not contribute materially to the direct nutrition of plants, 

 its mechanical influence upon the soil, and its absorbtive 

 and retentive power for moisture, ammonia and other fer- 

 tilizing matters, make it an important agent in agriculture. 

 When pure, it is extensively used in manufactures. The 

 pure, white alumina, called " kaolin/* is found in consider- 

 able quantities in Georgia, and is being used in the manu- 

 facture of earthenware. 



Corundum, also found in Georgia, another form of pure 

 alumina, possesses a high value as a polishing material. 

 The sapphire, emerald, topaz and ruby are also forms of 

 alumina. 



The paint, yellow or red ochre y is clay, colored with 

 iron. 



Alum is a double salt of sulphuric acid with alumina and 

 potash. It is used in dyeing, to unite with the coloring 

 matter, and fix it in the fibre of the cloth. 



Chlorine is a gas occurring only in combination with 

 other elements, chief among which is sodium, forming 

 common salt, chloride of sodium. The chief import- 

 ance of chlorine is in its bleaching effects. For this 

 purpose, it is combined with lime, or calcium and oxygen, 

 forming chloride of lime, or bleaching powder. Veg- 

 etable colors only are effected by it, and the presence 

 of water is necessary. It is also largely used as a disin- 

 fectant, to remove poisonous vegetable gases. Chlorine, 

 combined with hydrogen, forms hydrochloric, or muriatic 

 acid. 



Iron occurs most abundantly diffused over the earth, be- 

 ing found, in somejform, in plants, minerals, soils, waters, 

 and even in the blood of animals. Soils are colored with 

 it, and it even floats in fine particles in the atmosphere. 



That it is the most useful of all metals, and possesses 

 properties exactly suited to the wants of man, is not ques- 

 tioned. 



Pure metallic iron is not found occurring naturally. Its 



