Chapter 3: Page 15: Line 14 (105)

 "You'd appreciate Wapping High Street, then, — and, and Tyburn, of course! put that on your list."

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Line 105 Vulgarized:
"If you really like violence and gore, you should head down to Wapping High Street or Tyburn!"

Subtext:
Basically the shorthand for capital punishment was simply invoking Tyburn, made famous for hosting public executions for several centuries. Wapping also had its share of public executions being that it had an "Execution Dock" to hang pirates.

I felt like Dixon was being a bit sarcastic with his critique about how hard it was to get in a fight back in Bishop. Mason might have thought that too and so just continues the banter about the violence of London or, possibly, he takes him at face value and so suggests some violent tourist attractions. I like to think Mason isn't so naïve as to be suggesting these places earnestly and he's just having a bit of fun, as Dixon is, with how horribly violent the city can be. A bit of dark humor bonding the pair on their first meeting.