S. W. Johnson on some points of Agricultural Science. 79 
_. Liebig in the paper before referred to remarks that “a clay or 
_ lime-soil poor in organic matter, withdraws all the potash and all 
the silicic acid from a solution of silicate of potash; whereas one 
_ rich in so-called humus (humic acid), extracts the potash, but 
_ leaves the silicic acid in solution,” 
xyd of iron and alumina, or some of their compounds which 
are present in all soils, are the most obvious means of fixing the 
ae acid of soluble phosphates, and Thenard (Compt. 
_ Rend. Feb. 1, 1858,) has experimentally demonstrated that they 
. do remove phosphoric acid perfectly from solutions of phosphate 
of lime in water saturated with carbonic acid. Déhérain (quoted 
in Landwirthschaftliches Centralblatt, 1859, i, 94,) has shown 
on the other hand that carbonate of lime and ferric phosphate 
. > . However complicated and obscure these reac- 
_ tions may be, it is plain, that, henceforth, the effect of a solution of 
_ one base in displacing other bases from native hydrated aluminous 
F view. 
' _ On the other hand Eichhorn in the paper already referred 
| found that pure distilled water Seka! Gem a soil a suigs 
* See also his “Letters on Modern Agriculture,” London, 1859, 
