In "Fahrenheit 451", what is the purpose of the long description of the river, the woods, and the sky?

One reason that this is a long, descriptive passage is that it gives Montag a chance to reflect on his life.  He remembers a time when he was a child and he was brought to the country to visit a farm.  The innocence amd simplicity of that time are what he feels he needs to get back to - away from the parlor's TV walls and away from mechanical hounds.  He imagines a beautiful young woman sitting in a window braiding her hair as, again, a return to a simpler and better time. This is what he yearns for.  The description also lets the reader know that this simpler world is a much better one than the world Montag is fleeing.  Even though he is alone as he drifts down the river and passes the countryside, the reader gets the sense that Montag is less alone now than he was when he was on the crowded train with its blaring commercials.  The society he is leaving isolated people, discouraging people from talking to one another and getting to know one another.  He has the chance now to think, an opportunity the noisy train with the constant "Denham's Dentifrice" jingle denied him.  The peace and beauty of the countryside is a sharp contrast to the noisy, war-riiddled world Montag leaves behind.