At last, by long and graduated changes, seas and lands, peninsulas and
islands, lakes and rivers, hills and mountains, were wrought out by
internal or external energies on the crust thus generally fashioned.
Evaporation from the oceans gave rise to clouds and rain and hailstorms;
the water that fell upon the mountain tops cut out the valleys and river
basins; rills gathered into brooks, brooks into streams, streams into
primaeval Niles, and Amazons, and Mississippis. Volcanic forces uplifted
here an Alpine chain, or depressed there a deep-sea hollow. Sediment
washed from the hills and plains, or formed from countless skeletons of
marine creatures, gathered on the sinking bed of the ocean as soft ooze,
or crumbling sand, or thick mud, or gravel and conglomerate. Now
upheaved into an elevated table-land, now slowly carved again by rain
and rill into valley and watershed, and now worn down once more into
the mere degraded stump of a plateau, the crust underwent innumerable
changes, but almost all of them exactly the same in kind, and mostly in
degree, as those we still see at work imperceptibly in the world around
us. Rain washing down the soil; weather crumbling the solid rock; waves
dashing at the foot of the cliffs; rivers forming deltas at their barred
mouths; shingle gathering on the low spits; floods sweeping before them
the countryside; ice grinding ceaselessly at the mountain top; peat
filling up the shallow lake--these are the chief factors which have gone
to make the physical world as we now actually know it.
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