ble to unite
with ammonia, or other alkaline bases; and it soon became evident that
the idea of the clay as a whole, being the cause of the absorptive
property, was inconsistent with all the ascertained laws of chemical
combination."

After a series of experiments, Prof. Way came to the conclusion that
there is in clays a peculiar class of double silicates to which the
absorptive properties of soil are due. He found that the double silicate
of alumina and lime, or soda, whether found naturally in soils or
produced artificially, would be decomposed when a salt of ammonia, or
potash, etc., was mixed with it, the ammonia, or potash, taking the
place of the lime or soda.

Prof. Way's discovery, then, is not that soils have "absorptive
properties"--that has been long known--but that they absorb ammonia,
potash, phosphoric acid, etc., by virtue of the double silicate of
alumina and soda, or lime, etc., which they contain.

Soils are also found to have the power of absorbing ammonia, or rather
_carbonate_ of ammonia, from the air.

"It has long been known," says Prof. Way, "that soils acquire fertility
by exposure to the influence of the atmosphere--hence one of the uses of
fallows. * * I find that clay is so greedy of ammonia, that if air,
charged with carbonate of ammonia, so as to be highly pungent, is passed
through a tube filled with small fragments of dry clay, _every particle
of the gas is arrested_."

This power of the soil to absorb ammonia, is also due to the double
silicates. But there is this remarkable difference, that while either
the lime, soda, or potash silicate is capable of removing the ammonia
from _solution_, the _lime_ silicate alone _has the power of absorbing
it from the air_.

This is an important fact. Lime may act beneficially on many or most
soils by converting the soda silicate into a lime silicate, or, in other
words, converting a salt that will not absorb carbonate of ammonia from
the air, into a salt that has this important property.

There is no manure that has been so extensively used, and with such
general success as lime, and yet, "who among us," remarks Prof. Way,
"can say that he perfectly understands the mode in which lime acts?" We
are told that lime sweetens the soil, by neutralizing any acid character
that it may possess; that it assists the decomposition of inert organic
matters, and therefore increases the supply of vegetable food to plants:
that it decomposes the remains of