Why does Huck write Miss Watson? Then what does he do with the letter? Why?

Huck realizes that in an effort to make some money, the King had snuck back to the raft while he and the Duke had been searching for him, took Jim, sold him for forty dollars, and returned to the town to drink.

Huck sits down and contemplates his next move. He is torn between his friendship for Jim and his belief that helping a runaway slave is a sin. Huck finally writes a letter to Miss Watson explaining where Jim is. Not quite satisfied, he thinks about it some more, and, in one of the most dramatic scenes in the novel, rips apart the letter saying, "All right, then, I'll go to hell!"