A lonely boy was reading near a feeble fire'.
Theme: Isolation and Loneliness
The spirit takes him to past Christmases including seeing Scrooge alone at school.
The image of the 'lonely boy... near a feeble fire' reflects very closely the older Scrooge we have seen, alone eating gruel. Dickens uses the scene to allow the reader to feel sorry for the child 'Scrooge' whose loneliness was not by choice - although the adult Scrooge's is. Scrooge's sympathy for himself leads to sympathy for the carol singer from the night before.
We get a feeling that his adult life is shaped by his childhood, and that it is not all his fault.
The 'feeble fire' also shows how Scrooge may have previously felt the cold, but since then he has become unfeeling
The tri-colon 'long, bare, melancholy painfully mimics the childhood of Scrooge, tedious, lonely and sad.
The alliteration of 'feeble fire' makes it sound pathetic. While we sympathise with Scrooge, he does the same to Bob Cratchit, suggesting that Scrooge may have been influenced by his past, and is now coming to consider how he felt - leaving him with a feeling of guilt.
Setting stresses character traits. Earlier Scrooge was amongst a 'dingy cloud' and younger Scrooge is amongst 'lines of plain deal forms and desks' he was taught life is about facts, not emotions and human connection.