From its primal source in the Archaean rock, up through all the vast series of sedimentary rocks to our own time, what vicissitudes and transformations it has passed through; how many times it has died, so to speak, and been reborn from the rocks; how many times the winds and the rains have transported it, and infused invisible, life-giving gases into it; how many of the elements have throbbed with life, climbed and bloomed in trees, walked or flown or swam in animals, or slumbered for thousands upon thousands of years beneath the great ice-sheet of Pleistocene time!  A handful of the soil by your door is probably the most composite thing you can find in a day’s journey.  It may be an epitome of a whole geological formation, or of two or more of them.  If it happens to be made up of decomposed limestone, sandstone, slate, and basalt rock, think what a history would be condensed in it!

Our lawns are made up of ashes from the funeral pyre of mountains, of dust from the tombs of geologic ages.  What masses of rock does this sandbank represent! what an enormous grist in the great glacier mill do these layers of clay stand for!  Two feet of soil probably represent a hundred feet or more of rock.  Strictly speaking, the soil is the insoluble parts of the ground-up and decomposed rocks, after the rains and the winds have done their work and taken their toll of the grist they have ground.  Sometimes these mills take the whole grist and leave the rocks bare; but usually they leave a residuum in which life strikes its roots.  We do not see all that the waters take from the soil.  They have invisible pockets in which they carry away all the more soluble parts, such as lime, soda, potash, silica, magnesia, and others, and leave for the land the more insoluble parts.  These, too, in times of flood they carry away in suspension, in the shape of sand, silt, mud, gravel, and the like.  When the waters really digest the rocks, they hold the various minerals in solution, and run limpid and dancing to the sea; when they have an undigested burden, they run angry and turbid.

It is estimated that the Hudson River deposits in the sea each year four hundred and forty thousand tons of mineral matter in solution which it has taken from the land, and the Mississippi one hundred and twelve million tons.  Each carries away about four times as much in suspension.  The digestive or chemical power of water, then, is only about one fourth as great as its mechanical power.  Between the two the land is made to pay heavy toll to the sea.  But in time, in geologic time, it all comes back.  The suspended particles are dropped and go to make up the sedimentary rocks, while the solutes help cement the material of these rocks together, and also nourish the sea life from which limestone and other organic rocks are made.  When these rocks are again lifted to the surface and disintegrated into soil, then the debt of the sea to the land is paid.  This process, this cycle of soil loss and soil growth, has gone on