"So far as his labors extended?" said I.

"Yes," said Dupin. "The measures adopted were not only the best of
their kind, but carried out to absolute perfection. Had the letter
been deposited within the range of their search, these fellows would,
beyond a question, have found it."

I merely laughed - but he seemed quite serious in all that he said.

"The measures, then," he continued, "were good in their kind, and
well executed; their defect lay in their being inapplicable to the
case, and to the man. A certain set of highly ingenious resources
are, with the Prefect, a sort of Procrustean bed, to which he
forcibly adapts his designs. But he perpetually errs by being too
deep or too shallow, for the matter in hand; and many a schoolboy is
a better reasoner than he. I knew one about eight years of age, whose
success at guessing in the game of 'even and odd' attracted universal
admiration. This game is simple, and is played with marbles. One
player holds in his hand a number of these toys, and demands of
another whether that number is even or odd. If the guess is right,
the guesser wins one; if wrong, he loses one. The boy to whom I
allude won all the marbles of the school. Of course he had some
principle of guessing; and this lay in mere observation and
admeasurement of the astuteness of his opponents. For example, an
arrant simpleton is his opponent, and, holding up his closed hand,
asks, 'are they even or odd?' Our schoolboy replies, 'odd,' and
loses; but upon the second trial he wins, for he then says to
himself, 'the simpleton had them even upon the first trial, and his
amount of cunning is just sufficient to make him have them odd upon
the second; I will therefore guess odd;' - he guesses odd, and wins.