"The cards, you observe," said he, "are printed from type, not from a
plate. I would note that fact. And tell me what you make of that."

He handed me the pencil, which I examined with concentrated attention,
helping myself even with the lamp and my pocket lens. But even with
these aids I failed to discover anything unusual in its appearance.
Thorndyke watched me with a mischievous smile, and, when I had finished,
inquired:

"Well; what is it?"

"Confound you!" I exclaimed. "It's a pencil. Any fool can see that, and
this particular fool can't see any more. It's a wretched stump of a
pencil, villainously cut to an abominably bad point. It is coloured dark
red on the outside and was stamped with some name that began with
C--O--Co-operative Stores, perhaps."

"Now, my dear Jervis," Thorndyke protested, "don't begin by confusing
speculation with fact. The letters which remain are C--O. Note that fact
and find out what pencils there are which have inscriptions beginning
with those letters. I am not going to help you, because you can easily
do this for yourself. And it will be good discipline even if the fact
turns out to mean nothing."

At this moment he stepped back suddenly, and, looking down at the floor,
said:

"Give me the lamp, Jervis, I've trodden on something that felt like
glass."