How do you know Huck and Jim are friends by the end of Chapter 11?

By the end of Chapter 11, it is quite clear that Huck and
Jim are friends (at least from Huck's perspective -- we do not really know yet what is
in Jim's mind in this regard).  We can see this quite clearly because of how Huck has
come to be protective of Jim.

Here are two examples from
Chapters 10 and 11.

• When Huck causes Jim to get
  bitten by the snake, he does not admit he did it.  This may not sound friendly, but it
  shows Huck's concern for Jim's feelings.  He knows Jim's feelings will be hurt if he
  finds out Huck's prank was what caused him to be bitten.  Huck does not want that and so
  he stays silent.


• Huck hurries back from the town to warn
  Jim and to get away when he finds out Jim is suspected of killing him.  Moreover, he
  doesn't even think of saying that the people are after Jim -- he thinks they are after
  both Jim and himself.  This shows he is identifying himself with Jim just as a friend
  would.