ed out my watch. "Yes," I
said, "there is no doubt about it, I think; but I must be off. Anstey
urged me to be in court by 11.30 at the latest."

With infinite reluctance I collected my notes and papers and departed,
leaving Thorndyke diligently copying addresses out of the Post Office
Directory.

My business at the court detained me the whole of the day, and it was
near upon dinner-time when I reached our chambers. Thorndyke had not yet
come in, but he arrived half an hour later, tired and hungry, and not
very communicative.

"What have I done?" he repeated, in answer to my inquiries. "I have
walked miles of dirty pavement, and I have visited every pearl-shell
cutter's in London, with one exception, and I have not found what I
was looking for. The one mother-of-pearl factory that remains, however,
is the most likely, and I propose to look in there to-morrow morning.
Meanwhile, we have completed our data, with Polton's assistance. Here is
a tracing of our friend's skull taken from the mould; you see it is an
extreme type of brachycephalic skull, and markedly unsymmetrical. Here
is a transverse section of his hair, which is quite circular--unlike
yours or mine, which would be oval. We have the mother-of-pearl dust
from the outside of the hat, and from the inside similar dust mixed with
various fibres and a few granules of rice starch. Those are our data."

[Illustration: TRANSVERSE SECTIONS OF HUMAN HAIR: _A_, OF A NEGRO; _B_,
OF AN ENGLISHMAN; _C_, OF THE BURGLAR. ALL MAGNIFIED 600 DIAMETERS.]

"Supposing the hat should not be that of the burglar after all?" I
suggested.

"That would be annoying. But I think it is his, and I think I can guess
at the nature of the art treasures that were stolen."

"And you don't intend to enlighten me?"

"My dear fellow," he replied, "you have all the data. Enlighten yourself
by the exercise of your own brilliant faculties. Don't give way to
mental indolence."

I endeavoured, from the facts in my possession, to construct the
personality of the mysterious burglar, and failed utterly; nor was I
more successful in my endeavour to guess at the nature of the stolen
property; and it was not until the following morning, when we had set
out on our quest and were approaching Limehouse, that Thorndyke would
revert to the subject.

"We are now," he said, "going to the factory of Badcomb and Martin,
shell importers and cutters, in the West India Dock Road. If I don't
find my man there,