and satellites, is the vital order in full career.  It may yet linger upon Mars, but it is evidently waning.  On the inferior planets it probably had its day long ago, while it must be millions of years before it comes to the superior planets, if it ever comes to them.  What a vast, inconceivable outlay of time and energy for such small returns!  Evidently the vital order is only an episode, a transient or secondary phase of matter in the process of sidereal evolution.  Astronomic space is strewn with dead worlds, as a New England field is with drift boulders.  That life has touched and tarried here and there upon them can hardly be doubted, but if it is anything more than a passing incident, an infant crying in the night, a flush of color upon the cheek, a flower blooming by the wayside, appearances are against it.

We read our astronomy and geology in the light of our enormous egotism, and appropriate all to ourselves; but science sees in our appearance here a no more significant event than in the foam and bubbles that whirl and dance for a moment upon the river’s current.  The bubbles have their reason for being; all the mysteries of molecular attraction and repulsion may be involved in their production; without the solar energy, and the revolution of the earth upon its axis, they would not appear; and yet they are only bubbles upon the river’s current, as we are bubbles upon the stream of energy that flows through the universe.  Apparently the cosmic game is played for us no more than for the parasites that infest our bodies, or for the frost ferns that form upon our window-panes in winter.  The making of suns and systems goes on in the depths of space, and doubtless will go on to all eternity, without any more reference to the vital order than to the chemical compounds.

The amount of living matter in the universe, so far as we can penetrate it, compared with the non-living, is, in amount, like a flurry of snow that whitens the fields and hills of a spring morning compared to the miles of rock and soil beneath it; and with reference to geologic time it is about as fleeting.  In the vast welter of suns and systems in the heavens above us, we see only dead matter, and most of it is in a condition of glowing metallic vapor.  There are doubtless living organisms upon some of the invisible planetary bodies, but they are probably as fugitive and temporary as upon our own world.  Much of the surface of the earth is clothed in a light vestment of life, which, back in geologic time, seems to have more completely enveloped it than at present, as both the arctic and the antarctic regions bear evidence in their coal-beds and other fossil remains of luxuriant vegetable growths.