I'm in the middle of Sharp's Triumph and came upon your statements about mad hatters ("...no one knew why hatters were mad ..."). While you may know this, hatters would cure their felt in a mercury solution and size the hats by pulling them onto their own heads, over time absorbing enough through their scalps to develop toxic encephalopathy.
Stephen Hull
I had heard that, and thank you for reminding me! But Sharpe didn't know and I think I was trying to tell it from his point of view.