of its components; and thus a globe with a solid crust was formed, the
surface of which was partly dry and partly occupied by water, and
diversified by the abundant production of the various earths, gases,
metals, and other substances with which we are familiar. These
substances, in time, and by the slow action of their own laws and
properties, combined or separated and produced further forms. But to
come at once to the important part of the theory, we must at once direct
our attention to four substances; these would certainly, it is said (and
that no doubt is quite true) be present; they are oxygen, hydrogen,
nitrogen, and carbon. The first three would be, when the earth assumed
anything like its present conditions of temperature and air-pressure,
invisible gases, as they are at present; the fourth is a substance which
forms the basis of charcoal, and which we see in a nearly pure form
crystallized in the diamond.

Now, if these substances are brought together under certain appropriate
conditions, the oxygen and hydrogen can combine to form _water_; the
carbon and the oxygen will form _carbonic acid_; while nitrogen will
join with hydrogen to form that pungent smelling substance with which we
are familiar as _ammonia_. Again, let us suppose that three compound
substances--water, carbonic acid, and ammonia--are present together with
appropriate conditions; it is said that they will combine to form a
gummy transparent matter, which is called _protoplasm_. This protoplasm
may be found in small shapeless lumps, or it may be found enclosed in
cells, and in various beautifully shaped coverings, and it is also found
in the blood, and in all growing parts or organs of all animals and
plants of every kind whatsoever.

Protoplasm, then, is the physical basis of life. Simple, uniform,
shapeless protoplasm, combined out of the substances just named, first
came into existence; and as, however simple or shapeless, it always
exhibits the property of life, it can henceforth grow and develop from
simpler to ever increasingly complex forms, without any help but that of
surrounding circumstances--the secondary causes which we see in
operation around us.

If some readers should say they have never seen _protoplasm_, I may
remind them where every one has, at some time or another, met with it.
If you cut a stick of new wood from a hedge, and peel off the young
bark, you know that the bark comes off easily and entire, leaving a
clean whi