foundations—­how did all the unguided erosive forces do it?  The secret is in the structure of the rock, in the lines of cleavage, in the unequal hardness, and in the impulsive, irregular, and unequal action of the eroding agents.  These agents follow the lines of least resistance; they are active at different times and seasons, and from different directions; they work with infinite slowness; they undermine, they disintegrate, they dislodge, they transport; the hard streaks resist them, the soft streaks invite them; water charged with sand and gravel saws down; the wind, armed with fine sand, rounds off and hollows out; and thus the sculpturing goes on.  But after you have reasoned out all these things, you still marvel at the symmetry and the structural beauty of the forms.  They look like the handiwork of barbarian gods.  They are the handiwork of physical forces which we can see and measure and in a degree control.  But what a gulf separates them from the handiwork of the organic forces!

VI

Some things come and some things arise; things that already exist may come, but potential things arise; my friend comes to visit me, the tide comes up the river, the cold or hot wave comes from the west; but the seasons, night and morning, health and disease, and the like, do not come in this sense; they arise.  Life does not come to dead matter in this sense; it arises.  Day and night are not traveling round the earth, though we view them that way; they arise from the turning of the earth upon its axis.  If we could keep up with the flying moments,—­that is, with the revolution of the earth,—­we could live always at sunrise, or sunset, or at noon, or at any other moment we cared to elect.  Love or hate does not come to our hearts; it is born there; the breath does not come to the newborn infant; respiration arises there automatically.  See how the life of the infant is involved in that first breath, yet it is not its life; the infant must first be alive before it can breathe.  If it is still-born, the respiratory reaction does not take place.  We can say, then, that the breath means life, and the life means breath; only we must say the latter first.  We can say in the same way that organization means life, and life means organization.  Something sets up the organizing process in matter.  We may take all the physical elements of life known to us and jumble them together and shake them up to all eternity, and life will not result.  A little friction between solid bodies begets heat, a little more and we get fire.  But no amount of friction begets life.  Heat and life go together, but heat is the secondary factor.

Life is always a vanishing-point, a constant becoming—­an unstable something that escapes us while we seem to analyze it.  In its nature or essence, it is a metaphysical problem, and not one of physical science.  Science cannot grasp it; it evaporates in its crucibles.  And science is compelled finally to drive it into an imaginary region—­I had almost said, metaphysical region, the region of the invisible, hypothetical atoms of matter.  Here in the mysteries of molecular attraction and repulsion, it conceives the secret of life to lie.