, light--results, from the incandescence of a portion struck off; and
sometimes this incandescence is associated with chemical combination.
Thus, by the mechanical force expended in the collision, at least five,
and often more, different kinds of changes have been produced. Take,
again, the lighting of a candle. Primarily this is a chemical change
consequent on a rise of temperature. The process of combination having
once been started by extraneous heat, there is a continued formation of
carbonic acid, water, &c.--in itself a result more complex than the
extraneous heat that first caused it. But accompanying this process of
combination there is a production of heat; there is a production of
light; there is an ascending column of hot gases generated; there are
inflowing currents set going in the surrounding air. Moreover, the
complicating of effects does not end here: each of the several changes
produced becomes the parent of further changes. The carbonic acid given
off will by and by combine with some base; or under the influence of
sunshine give up its carbon to the leaf of a plant. The water will
modify the hygrometric state of the air around; or, if the current of
hot gases containing it comes against a cold body, will be condensed:
altering the temperature of the surface it covers. The heat given out
melts the subjacent tallow, and expands whatever it warms. The light,
falling on various substances, calls forth from them reactions by which
its composition is modified; and so divers colours are produced.
Similarly even with these secondary actions, which may be traced out
into ever-multiplying ramifications, until they become too minute to be
appreciated. And thus it is with all changes whatever. No case can be
named in which an active force does not evolve forces of several kinds,
and each of these, other groups of forces. Universally the effect is
more complex than the cause.

Doubtless the reader already foresees the course of our argument. This
multiplication of effects, which is displayed in every event of to-day,
has been going on from the beginning; and is true of the grandest
phenomena of the universe as of the most insignificant. From the law
that every active force produces more than one change, it is an
inevitable corollary that during the past there has been an ever-growing
complication of things. Throughout creation there must have gone on, and
must still go on, a never-ceasing transformation of the homog