e that
whatever else had been dusted in this room this shelf had not. The
accumulation of days, if not of months, was visible from one end to
the other of its unrelieved surface save where the handkerchief had
lain, and--the greatest discovery yet--where five clear spots just
to the left of the center showed where some man's finger-tips had
rested. Nothing but the pressure of fingertips could have caused
just the appearance presented by these spots. By scrutinizing them
closely I could even tell where the thumb had rested, and at once
foresaw the possibility of determining by means of these marks both
the size and shape of the hand which had left behind it so neat and
unmistakable a clue.

Wonderful! but what did it all mean? Why should a man rest his
finger-tips on this out-of-the-way shelf? Had he done so in an
effort to balance himself for a look up the chimney? No; for then
the marks made by his fingers would have extended to the edge of the
shelf, whereas these were in the middle of it. Their shape, too,
was round, not oblong; hence, the pressure had come from above
and--ah! I had it, these impressions in the dust of the shelf were just
such as would be made by a person steadying himself for a close look
at the old picture. And this accounted also for the overturned
chair, and for the handkerchief used as a duster. Some one's
interest in this picture had been greater than mine; some one who
was either very near-sighted or whose temperament was such that only
the closest inspection would satisfy an aroused curiosity.

This gave me an idea, or rather impressed upon me the necessity of
preserving the outline of these tell-tale marks while they were
still plain to the eye. Taking out my penknife, I lightly ran the
point of my sharpest blade around each separate impression till I
had fixed them for all time in the well worn varnish of the mahogany.

This done, my thoughts recurred to the question already raised. What
was there in this old picture to arouse such curiosity in one bent on
evil if not fresh from a hideous crime? I have said before that the
picture as a picture was worthless, a mere faded sketch fit only for
lumbering up some old garret. Then wherein lay its charm,--a charm
which I myself had felt, though not to this extent? It was useless
to conjecture. A fresh difficulty had been added to my task by this
puzzling discovery, but difficulties only increased my interest. It
was with an o