How does Mark Twain use imagery in Life on the Mississippi?

Life on the Mississippi is set along the Mississippi River. Twain's descriptions focus mainly on the area between Saint Louis and New Orleans, which is the stretch of the river (covering about half of it) which he studied under the direction of Mr. Bixby. During the first part of the book, Twain focuses on the river itself: its peculiarities, its directions, its islands, and so on. As he returns twenty-one years later, Twain focuses more on the islands and the towns lining the banks of the river. He also blends this with descriptions of the area as it was earlier, providing contrast for the reader. Towards the end of the book, he writes about the Upper Mississippi, taking the reader north into Minnesota, to describe the river there.