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Hereditary Genius
369
for all have, according to his views, sprung from common ancestry,
and therefore A and B having both descended from C, the lines of
descent might be remounted from A to C, and redescended from C to
B. Yet the changes are not by insensible gradations; there are many,
but not an infinite number of intermediate links; how is the law of
continuity to be satisfied by a series of changes in jerks? The
mechanical conception would be that of a rough stone, having, in
consequence of its roughness, a vast number of natural facets, on any
one of which it might rest in “stable” equilibrium. That is to say, when
pushed it would somewhat yield, when pushed much harder it would
again yield, but in a less degree; in either case, on the pressure being
withdrawn, it would fall back into its first position. But, if by a
powerful effort the stone is compelled to overpass the limits of the
facet on which it has hitherto found rest, it will tumble over into a
new position of stability, whence just the same proceedings must be
gone through as before, before it can be dislodged and rolled another
step onwards. The various positions of stable equilibrium may be
looked upon as so many typical attitudes of the stone, the type being
more durable as the limits of its stability are wider. We also see
clearly that there is no violation of the law of continuity in the
movements of the stone, though it can only repose in certain widely
separated positions,
Now for another metaphor, taken from a more complex system of
forces. We have all known what it is to be jammed in the midst of a
great crowd, struggling and pushing and swerving to and fro, in its
endeavour to make a way through some narrow passage. There is a
dead lock; each member of the crowd is pushing, the mass is
agitated, but there is no progress. If, by a great effort, a man drives
those in front of him but a few inches forwards, a recoil is pretty sure
to follow, and there is no ultimate advance. At length, by some
accidental unison of effort, the dead
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