seen by reference to p. 100, all of
the substances contained in plants, though not always in the correct
relative proportions to each other. When decomposition commences, the
carbon unites with the oxygen of the air, and passes off as carbonic
acid; the hydrogen and oxygen combine to form water (which evaporates),
and the _nitrogen is mostly resolved into ammonia, which escapes into
the atmosphere_.

[Describe fire-fanging.

What takes place when animal manure is exposed in an open barn-yard?

What does liquid manure lose by evaporation?]

If manure is thrown into heaps, it often ferments so rapidly as to
produce sufficient heat to set fire to some parts of the manure, and
cause it to be thrown off with greater rapidity. This may be observed in
nearly all heaps of animal excrement. When they have lain for some time
in mild weather, gray streaks of _ashes_ are often to be seen in the
centre of the pile. The organic part of the manure having been _burned_
away, nothing but the ash remains,--this is called _fire-fanging_.

Manures kept in cellars without being mixed with refuse matter are
subject to the same losses.

When kept in the yard, they are still liable to be lost by evaporation.
They are here often saturated with water, and this water in its
evaporation carries away the ammonia, and carbonic acid which it has
obtained from the rotting mass. The evaporation of the water is rapidly
carried on, on account of the great extent of surface. The whole mass is
spongy, and soaks the liquids up from below (through hollow straws,
etc.), to be evaporated at the surface on the same principle as causes
the wick of a lamp to draw up the oil to supply fuel for the flame.

LIQUID MANURE containing large quantities of nitrogen, and forming much
ammonia, is also liable to lose all of its organic part from evaporation
(and fermentation), so that it is rendered as much less valuable as is
the solid dung.[X]

[When does the waste of exposed manure commence?

What does economy of manure require?

What is the effect of leaching?

Give an illustration of leaching.]

From these remarks, it may be justly inferred that a very large portion
of the _value_ of solid and liquid manure as ordinarily kept is lost by
evaporation in a sufficient length of time, depending on circumstances,
whether it be three months or several years. The wasting commences as
soon as the manure is dropped, and continues, except in very cold
weather, unt