on the belief that the line bounding the bright part of the moon was an
exact straight line. The result was of course erroneous. He concluded
that the sun was 18 times as far as the moon, and not, as we now know,
400; but his conclusion, like his conception of the vast extent of the
sphere of the fixed stars, was far enough in advance of the popular
doctrine to subject him, according to Plutarch, to a charge of impiety.

Eratosthenes, again, contributed his mite to the treasure of human
science--his one mite; and yet by that he is better known than by all
the volumes which he seems to have poured out, on Ethics, Chronology,
Criticism on the Old Attic Comedy, and what not, spun out of his weary
brain during a long life of research and meditation. They have all
perished,--like ninety-nine hundredths of the labours of that great
literary age; and perhaps the world is no poorer for the loss. But one
thing, which he attempted on a sound and practical philosophic method,
stands, and will stand for ever. And after all, is not that enough to
have lived for? to have found out one true thing, and, therefore, one
imperishable thing, in one's life? If each one of us could but say when
he died: "This one thing I have found out; this one thing I have proved
to be possible; this one eternal fact I have rescued from Hela, the
realm of the formless and unknown," how rich one such generation might
make the world for ever!

But such is not the appointed method. The finders are few and far
between, because the true seekers are few and far between; and a whole
generation has often nothing to show for its existence but one solitary
gem which some one man--often unnoticed in his time--has picked up for
them, and so given them "a local habitation and a name."

Eratosthenes had heard that in Syene, in Upper Egypt, deep wells were