an ingredient which gives them much of their strength.[D]

3. It is a strong agent in the decomposition of vegetable matter, and is
thus of much importance in preparing manures.

4. It roughens the smooth round particles of sandy soils, and prevents
their compacting, as they are often liable to do.

5. It is also of use in killing certain kinds of insects, and, when
artificially applied, in smoothing the bark of fruit trees.

The source from which this and the other inorganic matters required are
to be obtained, will be fully considered in the section on manures.

SODA.

[Where is soda found most largely?

What is Glauber's salts?

What is washing soda?

What are some of the uses of lime?]

_Soda_, one of the alkalies contained in the ashes of plants, is very
much the same as potash in its agricultural character. Its uses are the
same as those of potash--before enumerated. Soda exists very largely in
nature, as it forms an important part of common salt, whether in the
ocean or in those inland deposits known as rock salt. When combined with
sulphuric acid it forms sulphate of soda or _Glauber's salts_. In
combination with carbonic acid, as carbonate of soda, it forms the
common washing soda of the shops. It is often necessary to render soils
fertile.

LIME.

_Lime_ is in many ways important in agriculture:

1. It is a constituent of plants and animals.

2. It assists in the decomposition of vegetable matter in the soil.

3. It corrects the acidity[E] of sour soils.

4. As chloride or sulphate of lime it is a good absorbent of fertilizing
gases.

[How is caustic lime made?

How much carbonic acid is thus liberated?

How does man resemble Sinbad the sailor?]

In nature it usually exists in the form of carbonate of lime: that is,
as marble, limestone, and chalk--these all being of the same
composition. In manufacturing caustic (or quick) lime, it is customary
to burn the carbonate of lime in a kiln; by this means the carbonic acid
is thrown off into the atmosphere and the lime remains in a pure or
caustic state. A French chemist states that every cubic yard of
limestone that is burned, throws off _ten thousand_ cubic yards of
carbonic acid, which may be used by plants. This reminds us of the story
of Sinbad the sailor, where we read of the immense _genie_ who came out
of a very small box by the sea-shore, much to the surprise of Sinbad,
who could not believe his eyes, until the _genie_ changed