]That isn't made very clear in P&P2...

I thought Lizzy was think of it in one of the scenes at least, but I may be mistaken, or influenced by the book.

My book reads 'a gulf impossible', it is the first edition reading. And the note says 'The second and subsequent editions of the novel emend this to "a gulf impassable", but the phrase makes perfect sense and might even be a buried quotation.'