Question

"I see a vacant seat," replied the Ghost, "in the poor chimney corner, and a crutch without an owner, carefully preserved."

what do these lines mean?

Answer 1

Those line mean that if Scrooge doesn't help the Cratchit family, the boy will probably die. Tiny Tim has to walk using crutches because he is suffering from a terrible disease (probably polio) and the Ghost says that if he doesn't get the medical help he needs, he will probably die and leave 'a crutch without an owner.'