How Did Houdini Trick Conan Doyle?

Typical Sceptical view of it all as is the norm when anything appears about Houdini. However, the final trick he describes is fascinating. One wonders whay the way he achieved it was never reavealed to prove it was a magic trick and not genuine slate writing.

http://blogs.plos.org/retort/2011/03/24/how-did-houdini-trick-conan-doyle/

This one is a much nicer piece on one of Houdini's stage assistants
http://www.drewacorn.com/life-arts/from-the-archives-a-19-year-old-dorothy-young-appeared-with-houdini-on-tour-1.2123896