• GEINE. 77 



volatile, or as it is termed by chemists, water of ammonia, 

 are added, the earth alumina will be let loose from the 

 alum, and it will immediately combine with, and precipitate 

 the geine, that is, little flocks fall down gradually in the 

 liquor. Hence is derived an important character. Geine 

 has a great affinity for alumina. If lime had been added to 

 the solution of geine, the same effect would have followed. 

 The same effect would be produced by magnesia, by oxide 

 of iron, and by manganese. 



112. Alumina, lime, magnesia, oxides of iron, and manga- 

 nese, will, therefore, in soil, immediately seize upon any sol- 

 uble geine, and, forming compounds with it, detain it there. 

 The air and water will have now little action upon it. 



113. But supposing that none of these elements (112) are 

 present in soil, the fact stated (110) shows that all soluble 

 geine, or solution of extract in water, soon passes to a mix- 

 ture of soluble and insoluble, forming a dark brown powder. 

 This is thus withdrawn, deep in the soil, from the immediate 

 action of the air, and undergoes no further change. It may 

 remain unchanged an indefinite time. If ploughed up, 

 exposed anyhow to the action of air or moisture, it again 

 becomes partly soluble in water, and exhibits its former 

 characters, viz. : great affinity for earths and metallic oxides. 

 In this state it is vegetable mould. 



114. Vegetable mould, then, is a mixture of the organic 

 and inorganic elements of soil. It is a compound of soluble 

 geine with earths and metals, mixed with soluble and insol- 

 uble geine. It is a chemical compound of organic with 

 inorganic parts of soil, mixed with a large portion of free 

 organic matter. 



115. The inorganic elements of mould are, 1st. The bases 

 found in the soil, produced by the decomposition of silicates, 

 as lime, potash, soda, magnesia, alumina, iron, <kc. 2dly. 



