imates of the
digested food, and the _soluble_ parts of the ash.

THE BREATH contains the _first class_ of proximates, those which contain
carbon, hydrogen and oxygen, but _no nitrogen_.[W]

FOOTNOTES:

[V] This account of digestion is not, perhaps, strictly accurate in a
physiological point of view, but it is sufficiently so to give an
elementary understanding of the character of excrements as manures.

[W] The excrements of animals contain more or less of sulphur, and
sometimes small quantities of phosphorus.

CHAPTER III.

WASTE OF MANURE.

[What are the first causes of loss of manure?

What is _evaporation_?]

The loss of manure is a subject which demands most serious attention.
Until within a few years, little was known about the true character of
manures, and consequently, of the importance of protecting them against
loss.

The first causes of waste are _evaporation_ and _leaching_.

EVAPORATION.

[Name a solid body which evaporates.

What takes place when a dead animal is exposed to the atmosphere for a
sufficient time?

What often assist the evaporation of solids?]

Evaporation is the changing of a solid or liquid body to a vapory form.
Thus common smelling salts, a solid, if left exposed, passes into the
atmosphere in the form of a gas or vapor. Water, a liquid, evaporates,
and becomes a vapor in the atmosphere. This is the case with very many
substances, and in organic nature, both solid and liquid, they are
liable to assume a gaseous form, and become mixed with the atmosphere.
They are not destroyed, but are merely changed in form.

As an instance of this action, suppose an animal to die and to decay on
the surface of the earth. After a time, the flesh will entirely
disappear, but is not lost. It no longer exists as the flesh of an
animal, but its carbon, hydrogen, oxygen, and nitrogen, still exist in
the air. They have been liberated from the attractions which held them
together, and have passed away; but (as we already know from what has
been said in a former section) they are ready to be again taken up by
plants, and pressed into the service of life.

The evaporation of liquids may take place without the aid of any thing
but heat; still, in the case of solids, it is often assisted by decay
and combustion, which break up the bonds that hold the constituents of
bodies together, and thus enable them to return to the atmosphere, from
which they w