When he sees the trout moving about in the pools of the river, he feels an elation that he has not felt for a long time. Nick saw trout in the stream below the bridge; his "heart tightened as the trout moved." Then, leaving the burned town behind him, Nick "felt happy. He felt he had left everything behind, the need for thinking, the need to write, other needs. It was all back of him." These key ideas, then, are the essence of this story: Nick has escaped into his own world where the mere sight of trout influences his responses. He is at one with this world: "He did not need to get his map out. He knew where he was from the position of the river."
As Nick walks through Seney, he notices that even the surface of the ground has been burned. The black, sooty ruin of Seney represents the atrocities of war and its devastating effect on Nick's psycho-emotional well being. Here, he walks through it and notices that even the grasshoppers are covered with soot, much the same way that Nick himself is still covered with "soot" from the war.
However, note that Nick does not go to the river immediately. He wants to get as far upstream as he can in one day's walking. Even though he stops and instinctively knows that the river cannot be more than a mile north of where he is, being tired, he takes off his backpack and sleeps on the ground until the sun is almost down.
The description of Nick's putting up the tent, smoothing the ground, chopping stakes, pulling the tent taut, hanging cheesecloth over the front — all of these components coalesce and make Nick feel happy: "He had made his camp. He was settled. Nothing could touch him. It was a good place to camp."
