slight personal disfigurement? It might be so; or there might be some
further motive. It was impossible to say.

Turning this question over, I suddenly remembered the peculiarity of Mr.
Weiss's spectacles. And here I met with a real poser. I had certainly
seen through those spectacles as clearly as if they had been plain
window-glass; and they had certainly given an inverted reflection of the
candle-flame like that thrown from the surface of a concave lens. Now
they obviously could not be both flat and concave; but yet they had the
properties peculiar to both flatness and concavity. And there was a
further difficulty. If I could see objects unaltered through them, so
could Mr. Weiss. But the function of spectacles is to alter the
appearances of objects, by magnification, reduction or compensating
distortion. If they leave the appearances unchanged they are useless. I
could make nothing of it. After puzzling over it for quite a long time,
I had to give it up; which I did the less unwillingly inasmuch as the
construction of Mr. Weiss's spectacles had no apparent bearing on the
case.

On arriving home, I looked anxiously at the message-book, and was
relieved to find that there were no further visits to be made. Having
made up a mixture for Mr. Graves and handed it to the coachman, I raked
the ashes of the surgery fire together and sat down to smoke a final
pipe while I reflected once more on the singular and suspicious case in
which I had become involved. But fatigue soon put an end to my
meditations; and having come to the conclusion that the circumstances
demanded a further consultation with Thorndyke, I turned down the gas to
a microscopic blue spark and betook myself to bed.