In The Adventures of Huckleberry Finn, how does the river permit physical variety?

The river is used as a narrative device to move the action of the story from one place to another. Thus, the physical setting of the story moves as Huck and Jim travel down the Mississippi River. This enable Twain to incorporate a variety of episodes, each with a different theme, and each helping Huck to mature in different ways. For instance, in the Grangerford episode, Huck encounter his first real experience with death when his friend Buck is killed. This helps him mature and see the consequences of fighting that , for many, represents the Civil War. In the Wilks episode, Huck sees the consequences of real con artists. Huck has been a small con artist all his life, but when he gets a crush on Mary Jane Wilks, he finds a conscience and sees the result of hurting people without thought of the consequences. Each of these episods take place in a different physical place and allow Huck to learn different lessons about life. Instead of keeping the action in one place like St. Petersburg, where Huck would learn the same values over and over, Twain physically moves the characters so he can experience different values and learn from them.