Why is Huck first elated, then depressed?

I'm not sure exactly what you are getting at here. I'm thinking that he is elated because the King and Duke are finally discovered to be frauds and depressed because he has to leave Mary Jane .

I know where you are comming from with this question but Huck seems to be depressed thought the whole bookseeb with his use of the word "lonesome" which he starts using in episode 1 and then he starts saying "I most wish I was dead" I think this might relate to his missing of Tom Sawyer.