g
matters. There is a simple experiment by which this power can be shown.

Ex.--Take two barrels of pure beach sand, and mix with the sand in one
barrel a few handfuls of charcoal dust, leaving that in the other pure.
Pour the brown liquor of the barn-yard through the pure sand, and it
will pass out at the bottom unaltered. Pour the same liquor through the
barrel, containing the charcoal, and pure water will be obtained as a
result. The reason for this is that the charcoal retains all of the
impurities of the liquor, and allows only the water to pass through.
Charcoal is often employed to purify water for drinking, or for
manufacturing purposes.

[Will charcoal purify water?

If a piece of tainted meat, or a fishy duck be buried in a rich garden
soil, what takes place?

What is the reason of this?

How does charcoal overcome offensive odors?

How can you prove that charcoal absorbs the _mineral_ impurities of
water?]

A rich garden-soil contains large quantities of carbonaceous matter;
and, if we bury in such a soil a piece of tainted meat or a fishy duck,
it will, in a short time, be deprived of its odor, because the charcoal
in the soil will entirely absorb it.

Carbon absorbs gases as well as the impurities of water; and, if a
little charcoal be sprinkled over manure, or any other substance,
emitting offensive odors, the gases escaping will be taken up by the
charcoal, and the odor will cease.

It has also the power of absorbing _mineral_ matters, which are
contained in water. If a quantity of salt water be filtered through
charcoal, the salt will be retained, and the water will pass through
pure.

We are now able to see how carbon renders the soil retentive of manures.

1st. Manures, which resemble the brown liquor of barn-yards, have their
fertilizing matters taken out, and retained by it.

[How does charcoal in the soil affect the manures applied?

Why does charcoal in the soil cause it to appropriate the gases of the
atmosphere?

What fertilizing gases exist in the atmosphere?

How are they carried to the soil?

Does the carbon retain them after they reach the soil?

What can you say of the air circulating through the soil?

How does carbon give the soil power to absorb moisture?]

2d. The gases arising from the decomposition (_rotting_) of manure are
absorbed by it.

3d. The soluble mineral portions of manure, which might in some soils
leach down with water, are arrested and retained a