might have been one of a score of things. A jeweler can't say exactly how he gets on the track of fake stones. He can feel them. He can almost smell them. I worked with a jeweler once. That's how I got my knowledge of jewels. But, if you mean, can I prove what I say about this necklace, that's easy. There's no deception. It's simple. See here. These stones are supposed to be diamonds. Well, the diamond is the hardest stone in existence. Nothing will scratch it. Now, I've got a little ruby, out of a college pin, which I know is genuine. By rights, then, that ruby ought not to have scratched these stones. You follow that? But it did. It scratched two of them, the only two I tried. If you like, I can continue the experiment. But there's no need. I can tell you right now what these stones are. I said they were paste, but that wasn't quite accurate. They're a stuff called white jargoon. It's a stuff that's very easily faked. You work it with the flame of a blow-pipe. You don't want a full description, I suppose? Anyway, what happens is that the blow-pipe sets it up like a tonic. Gives it increased specific gravity and a healthy complexion and all sorts of great things of that kind. Two minutes in the flame of a blow-pipe is like a week at the seashore to a bit of white jargoon. Are you satisfied? If it comes to that, I guess you can hardly be expected to be. Convinced is a better word. Are you convinced, or do you hanker after tests like polarized light and refracting liquids?"