I took the little “restoration,” and, holding it up before my eyes, moved it to and fro as I looked through it at the window.

“It was not a lens,” I pronounced eventually.

“No,” Thorndyke agreed, “it was not a lens.”

“And so cannot have been a spectacle-glass. But the surface was curved⁠—one side convex and the other concave⁠—and the little piece that remains of the original edge seems to have been ground to fit a bezel or frame. I should say that these are portions of a watch-glass.”

“That is Polton’s opinion,” said Thorndyke, “and I think you are both wrong.”

“What do you say to the glass of a miniature or locket?”

“That is rather more probable, but it is not my view.”

“What do you think it is?” I asked. But Thorndyke was not to be drawn.