humb-print so that detection is impossible. You
have also stated that the thumb-print on the paper found in Mr. Hornby's
safe is a forgery. Do you mean that it _may_ be a forgery, or that it
actually is one?"

"I mean that it actually is a forgery."

"When did you first come to the conclusion that it was a forgery?"

"When I saw it at Scotland Yard. There are three facts which suggested
this conclusion. In the first place the print was obviously produced
with liquid blood, and yet it was a beautifully clear and distinct
impression. But such an impression could not be produced with liquid
blood without the use of a slab and roller, even if great care were
used, and still less could it have been produced by an accidental smear.

"In the second place, on measuring the print with a micrometer, I found
that it did not agree in dimensions with a genuine thumb-print of Reuben
Hornby. It was appreciably larger. I photographed the print with the
micrometer in contact and on comparing this with a genuine thumb-print,
also photographed with the same micrometer in contact, I found that the
suspected print was larger by the fortieth of an inch, from one given
point on the ridge-pattern to another given point. I have here
enlargements of the two photographs in which the disagreement in size is
clearly shown by the lines of the micrometer. I have also the micrometer
itself and a portable microscope, if the Court wishes to verify the
photographs."

"Thank you," said the judge, with a bland smile; "we will accept your
sworn testimony unless the learned counsel for the prosecution demands
verification."

He received the photographs which Thorndyke handed up and, having
examined them with close attention, passed them on to the jury.

"The third fact," resumed Thorndyke, "is of much more importance, since
it not only proves the print to be a forgery, but also furnishes a very
distinct clue to the origin of the forgery, and so to the identity of
the forger." (Here the court became hushed until the silence was so
profound that the ticking of the clock seemed a sensible interruption. I
glanced at Walter, who sat motionless and rigid at the end of the bench,
and perceived that a horrible pallor had spread over his face, while his
forehead was covered with beads of perspiration.) "On looking at the
print closely, I noticed at one part a minute white mark or space. It
was of the shape of a capital S and had evidently been produced by a
d