dear Watson--yet another brain-wave! Had the volume been an
unusual one, he would have sent it to me. Instead of that, he
had intended, before his plans were nipped, to send me the clue
in this envelope. He says so in his note. This would seem to
indicate that the book is one which he thought I would have no
difficulty in finding for myself. He had it--and he imagined
that I would have it, too. In short, Watson, it is a very common
book."

"What you say certainly sounds plausible."

"So we have contracted our field of search to a large book,
printed in double columns and in common use."

"The Bible!" I cried triumphantly.

"Good, Watson, good! But not, if I may say so, quite good
enough! Even if I accepted the compliment for myself I could
hardly name any volume which would be less likely to lie at the
elbow of one of Moriarty's associates. Besides, the editions of
Holy Writ are so numerous that he could hardly suppose that two
copies would have the same pagination. This is clearly a book
which is standardized. He knows for certain that his page 534
will exactly agree with my page 534."

"But very few books would correspond with that."

"Exactly. Therein lies our salvation. Our search is narrowed
down to standardized books which anyone may be supposed to
possess."