"Why do you say that?"
"Because now I know this man Wilkins is a criminal of the worst type!"
"You know it?"
"Yes, I know it as well as I know I'm sitting at this table. And I can prove it."
"How?" demanded Van Tuyl.
"I'll show you how in a very few moments. And, on second thoughts, I'd have that maid Felice bring what you regard as valuable right to this dining-room—I mean your jewels and things."
"But this sounds so silly," demurred my still reluctant hostess.
"It won't sound half so silly as a Tiffany advertisement of a reward and no questions asked."
Beatrice Van Tuyl intercepted a footman and sent him off for the maid Felice. A moment later Wilkins was at our side quietly serving the café noir in tiny gold-lined cups.
"This method of mine for identifying the real pearl, as you will see," I blandly went on, "is a very simple one. You merely take a match end and dip it in clear water. Then you let a drop of water fall on the pearl. If the stone is an imitation one the water-drop will spread and lie close to the surface. If the stone is genuine the drop will stand high and rounded, like a globe of quicksilver, and will shake with the minute vibrations which pass through any body not in perfect equilibrium."