'Tis lovely in S--

I need to call upon the wisdom of my readers to answer a question I have had for years, but never really asked about. As you know, I am reading Jane Eyre again. It's an older book, a classic even, and the source of my puzzlement is generally found only in classic literature. Reading along, I came across this fragment: "away we rattled over the 'stony street' of L--" There isn't even a period to finish the sentence, I guess the dash nulls the period? But that isn't the main question, the main question is why do they only put in the dash at all? Do they not wish to name any cities? Does it make it so the book can take place where ever the reader's imagination desires? I asked Clark about it and he has also noticed it, and noticed that it only occurs with place names. I would love any input that you could provide.