Fun Fact: Drawing even this very simplified map of London took one thousand years! Boy I wish I could hire a prop designer! Or a layout artist!
The trip Lanyon refers to is Jekyll's research trip prior to creating the transformation formula. He went all over the place in search of esoteric alchemical knowledge and ingredients. There was a version of Jekyll's conversation in Chapter 6 with Frankenstein--in which Frankenstein tries to trip him up on his alchemical knowledge to expose him as a "fake science boy"--where Jekyll skims over just how far he went in pursuit of this research, from crumbling chapels in remote villages to seaside tidepools with just the right mix of minerals. It ended up being a bit wordy--you only need so much of two nerds trying to out-nerd each other--so it was cut.