ni,
Laskowsky, Strehl, Pillnitz, Peters, W. Wolff, Lehmann, and Biedermann.

_Bases and Acids fixed by Soil._

From these experiments it may be taken as proved beyond doubt that soils
have the power of fixing, to a greater or less extent, the following
bases: ammonia, potash, lime, magnesia and soda; as well as the two
acids, phosphoric and silicic. The order in which the different bases
are fixed is an important point. It would seem that the soil has a
greater affinity for the more valuable manurial substances, such as
ammonia, potash, and lime, and that these substances are first fixed.
That in fixing any one of the above-mentioned bases from its solution,
it can only do so at the expense of another base. Thus, in fixing
potash, either lime, magnesia, or soda must be given up. Further, when a
base in solution, as sulphate or chloride, is absorbed by a soil, the
base is alone fixed, while the sulphuric acid or chlorine is left in
solution. Lastly, the amount of base absorbed by a soil depends on the
concentration of its solution, on the nature of its combination, and the
temperature. Way found in his experiments that a clay soil has more
power than a peaty soil, and that a peaty soil has more power than a
sandy soil.

_Causes of this Fixation._

So much for the fact of soil absorption; as to the cause or causes of
this absorption, a great number of theories have been put forward. Those
may be divided into two classes--those accounting for it as due to
physical properties of the soil; and those, on the other hand,
explaining it as due to chemical action.

To the latter class Way's belonged. He explained it as due to the
formation in the soil of hydrated double silicates, consisting of a
silicate of alumina, along with a silicate of the base fixed. Bruestlein
and Peters, on the other hand, were of the opinion that it was purely
physical in its nature. A theory has been advanced that it is due to the
formation of insoluble ulmates and humates, formed by the union of ulmic
and humic acids, along with the bases fixed. Among others who devoted
investigation to this interesting question, may be mentioned Rautenberg
and Heiden.

On reviewing the evidence, it seems to be pretty well established that
it really is mainly a chemical act, due chiefly to the formation of
double silicates, and doubtless to a certain extent to the formation of
insoluble humates and ulmates. Heiden's experiments would seem to
indicate, howe