Oh, hang on, Simpson has just met David Waldie. So, the experiments with chloroform cannot be far off.
Again, I'm finding this aspect of the story much more interesting than the actual underlying murder mystery. Tho, we don't even know whether there is a murder mystery. There have been suspicious deaths...but there has been no investigation of any of them, and almost 60% into the book, I might suggest this is a bit late to start looking into that aspect of the book.