Epigraphs are like little appetizers to the great entrée of a story. They illuminate important aspects of the story, and they get us headed in the right direction.
On its appearance in 'Household Words,' this tale was obliged to conform to the conditions imposed by the requirements of a weekly publication, and likewise to confine itself within certain advertised limits, in order that faith might be kept with the public. Although these conditions were made as light as they well could be, the author found it impossible to develope the story in the manner originally intended, and, more especially, was compelled to hurry on events with an improbable rapidity towards the close. In some degree to remedy this obvious defect, various short passages have been inserted, and several new chapters added. With this brief explanation, the tale is commended to the kindness of the reader;
'Beseking hym lowly, of mercy and pite,
Of its rude makyng to have compassion.'
What's up with the epigraph?
This is a pretty hilarious epigraph, in our humble opinion.
Basically Gaskell is saying "Hey dudes. I wrote this novel under strict deadline. I couldn't make it quite as good as I wanted to, because I needed to hurry it along, because some people (like one editor guy whose name rhymes with Harles Pickens) made me work too fast. So I added some stuff to make it better. Don't judge me too harshly, guys. Here's a rhyme about how you should not judge me. Like, seriously. My novel could be way better."
Basically, this is the world's weirdest literary humblebrag.