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. Land and sea,
coast and contour, hill and valley, dale and gorge, earth-sculpture
generally--all are due to the ceaseless interaction of these separately
small and unnoticeable causes, aided or retarded by the slow effects of
elevation or depression from the earth's shrinkage towards its own
centre. Geology, in short, has shown us that the world is what it is,
not by virtue of a single sudden creative act, nor by virtue of
successive terrible and recurrent cataclysms, but by virtue of the slow
continuous action of causes still always equally operative.

Evolution in geology leads up naturally to evolution in the science of
life. If the world itself grew, why not also the animals and plants that
inhabit it? Already in the eager active eighteenth century this obvious
idea had struck in the germ a large number of zoologists and botanists,
and in the hands of Lamarck and Erasmus Darwin it took form as a
distinct and elaborate system of organic evolution. Buffon had been the
first to hint at the truth; but Buffon was an eminently respectable
nobleman in the dubious days of the tottering monarchy, and he did not
care personally for the Bastille, viewed as a place of permanent
residence. In Louis Quinze's France, indeed, as things then went, a man
who offended the orthodoxy of the Sorbonne was prone to find himself
shortly ensconced in free quarters, and kept there for the term of his
natural existence without expense to his heirs or executors. So Buffon