What theme is being reinforced in the following paragraph from Chapter 19?
A little smoke couldn't be noticed, now, so we would take some fish off of the lines, and cook up a hot breakfast. And afterwards we would watch the lonesomeness of the river, and kind of lazy along, and by-and-by lazy off to sleep. Wake up, by-and-by, and look to see what done it, and maybe see a steamboat, coughing along up stream, so far off towards the other side you couldn't tell nothing about her only whether she was stern-wheel or side-wheel; then for about an hour there wouldn't be nothing to hear nor nothing to see- just solid lonesomeness. Next you'd see a raft sliding by, away off yonder, and maybe a galoot on it chopping, because they're most always doing it on a raft; you'd see the ax flash, and come down- you don't hear nothing; you see that ax go up again, and by the time it's above the man's head, then you hear the k'chunk!- it had took all that time to come over the water. So we would put in the day, lazying around, listening to the stillness. Once there was a thick fog, and the rafts and things that went by was beating tin pans so the steamboats wouldn't run over them. A scow or a raft went by so close we could hear them talking and cussing and laughing- heard them plain; but we couldn't see no sign of them; it made you feel crawly, it was like spirits carrying on that way in the air.