--for I
suppose he did murder him?"

"I think there is no doubt of it," replied Thorndyke.

"Then," said Marchmont, "we will hear the rest of the argument, if you
please."

"Very well," said Thorndyke. "As the evidence stands, we have proved
that Jeffrey Blackmore was a prisoner in the house in Kennington Lane
and that some one was personating him at New Inn. That some one, we have
seen, was, in all probability, John Blackmore. We now have to consider
the man Weiss. Who was he? and can we connect him in any way with New
Inn?

"We may note in passing that Weiss and the coachman were apparently one
and the same person. They were never seen together. When Weiss was
present, the coachman was not available even for so urgent a service as
the obtaining of an antidote to the poison. Weiss always appeared some
time after Jervis's arrival and disappeared some time before his
departure, in each case sufficiently long to allow of a change of
disguise. But we need not labour the point, as it is not of primary
importance.

"To return to Weiss. He was clearly heavily disguised, as we see by his
unwillingness to show himself even by the light of a candle. But there
is an item of positive evidence on this point which is important from
having other bearings. It is furnished by the spectacles worn by Weiss,
of which you have heard Jervis's description. These spectacles had very
peculiar optical properties. When you looked <i>through</i> them they had the
properties of plain glass; when you looked <i>at</i> them they had the
appearance of lenses. But only one kind of glass possesses these
properties; namely, that which, like an ordinary watch-glass, has
curved, parallel surfaces. But for what purpose could a person wear
'watch-glass' spectacles? Clearly, not to assist his vision. The only
alternative is disguise.

"The properties of these spectacles introduce a very curious and
interesting feature into the case. To the majority of persons, the
wearing of spectacles for the purpose of disguise or personation, seems
a perfectly simple and easy proceeding. But, to a person of normal
eyesight, it is nothing of the kind. For, if he wears spectacles suited
for long sight he cannot see distinctly through them at all; while, if
he wears concave, or near sight, glasses, the effort to see through them
produces such strain and fatigue that his eyes become disabled
altogether. On the stage the difficulty is met by using spectacles of
plain w