Jewels thrown into a gorge
I am positive there is a short story in which some jewels (probably paste ones) are thrown out of a train as it passes over a gorge. I think it's because the real jewels are stolen earlier in the story and paste ones are left in their place, and then, following a murder, these jewels have to be got rid of for some reason, so someone chucks them out of the window. I read The Blue Train for the first time, and I was sure I'd read it before. Some researching led me to The Plymouth Express, which is basically The Blue Train in an earlier form, but this isn't the short story I was thinking of (and I hadn't read it before I read The Blue Train). Does anyone know what I'm talking about?