what happen in chapter 33?

The narrator ends his journal about the raft journey. The raft had capsized and Axel is saved by Hans Bjelke . They have lunch and try to consider where they are. They calculate that they are under the "Mediterranean itself.” The uncle takes out his compass and they are all shocked,

"during the tempest, there had been a sudden slant of wind, of which we had been unable to take any account, and thus the raft had carried us back to the shores we had left, apparently forever, so many days before! "