animal against another--heads I win, tails
you lose. Some plants spread both by seed and runners, this doubles
their chances; they are kept in check because certain localities are
unfavorable to them. I know a section of the country where a species of
mint has completely usurped the pastures. It makes good bee pasturage,
but poor cattle pasturage. Quack grass will run out other grass because
it travels under ground in the root as well as above ground in the seed.

XI. NATURAL SCULPTURE

We may say that all the forms in the non-living world come by chance, or
by the action of the undirected irrational physical forces, mechanical
or mechanico-chemical. There are not two kinds of forces shaping the
earth's surface, but the same forces are doing two kinds of work, piling
up and pulling down--aggregating and accumulating, and separating and
disintegrating.

It is to me an interesting fact that the striking and beautiful forms in
inorganic nature are not as a rule the result of a building-up process,
but of a pulling-down or degradation process. A natural bridge, an
obelisk, caves, canals, the profile in the rocks, the architectural and
monumental rock forms, such as those in the Grand Canon and in the
Garden of the Gods, are all the result of erosion. Water and other
aerial forces are the builders and sculptors, and the nature and
structure of the material determine the form. It is as if these striking
forms were inherent in the rocks, waiting for the erosive forces to
liberate them. The stratified rocks out of which they are carved were
not laid down in forms that appeal to us, but layer upon layer, like the
leaves of a book; neither has the crumpling and deformation of the
earth's crust piled them up and folded them in a manner artistic and
suggestive. Yet behold what the invisible workmen have carved out of
them in the Grand Canon! It looks as though titanic architects and
sculptors had been busy here for ages. But only little grains of sand
and a vast multitude of little drops of water, active through geologic
ages, were the agents that wrought this stupendous spectacle. If the
river could have builded something equally grand and beautiful with the
material it took out of this chasm! But it could not--poetry at one end
of the series and dull prose at the other. The deposition took the form
of broad, featureless, uninteresting plains--material for a new series
of stratified rocks, out of which other future Grand Canon