reluctantly from his pocket, hurrying away with another volume.
Sometimes he would deliver to the clerk the title of a work written
on a slip of paper: an unheard-of book; to be ordered--perhaps from
the Old World. For one great book inevitably leads to another. They
have their parentage, kinship, generations. They are watch-towers
in sight of each other on the same human highway. They are strands
in a single cable belting the globe. Link by link David's
investigating hands were slipping eagerly along a mighty chain of
truths, forged separately by the giants of his time and now welded
together in the glowing thought of the world.

Not all of these were scientific works. Some were works which
followed in the wake of the new science, with rapid applications of
its methods and results to other subjects, scarce conterminous or
not even germane. For in the light of the great central idea of
Evolution, all departments of human knowledge had to be reviewed,
reconsidered, reconceived, rearranged, rewritten. Every foremost
scholar of the world, kindling his own personal lamp at that
central sunlike radiance, retired straightway into his laboratory
of whatsoever kind and found it truly illuminated for the first
time. His lamp seemed to be of two flames enwrapped as one; a
baleful and a benign. Whenever it shone upon anything that was
true, it made this stand out the more clear, valuable, resplendent.
But wherever it uncovered the false, it darted thereat a swift
tongue of flame, consuming without mercy the ancient rubbish of the
mind. Vast purification of the world by the fire of truth! There
have been such purifications before; but never perhaps in the
history of the race was so much burned out of the intellectual path
of man as during the latter half of the nineteenth century.