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."
"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, I shall hand the facts over to the police, and waste no more time over the case."
"I am looking for an elderly Japanese, wearing a new hat or, more probably, a cap, and having a bruise on his right cheek or temple. I am also looking for a cab-yard; but here we are at the works, and as it is now close on the dinner-hour, we will wait and see the hands come out before making any inquiries."