Thus, by the original 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 set going by extraneous heat, there is a continued formation of carbonic acid, water, etc.—­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 currents established in the surrounding air.  Moreover the decomposition of one force into many forces 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 come against a cold body, will be condensed:  altering the temperature, and perhaps the chemical state, 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 it 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 results, 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 through all time there has been an ever-growing complication of things.  Starting with the ultimate fact that every cause produces more than one effect, we may readily see that throughout creation there must have gone on, and must still go on, a never-ceasing transformation of the homogeneous into the heterogeneous.  But let us trace out this truth in detail.

Without committing ourselves to it as more than a speculation, though a highly probable one, let us again commence with the evolution of the solar system out of a nebulous medium.[3] From the mutual attraction of the atoms of a diffused mass whose form is unsymmetrical, there results not only condensation but rotation:  gravitation simultaneously generates both the centripetal and the centrifugal forces.  While the condensation and the rate of rotation are progressively increasing, the approach of the atoms necessarily generates a progressively increasing temperature.  As this temperature rises, light begins to be evolved; and ultimately there results a revolving sphere of fluid matter radiating intense heat and light—­a sun.