The framing section of this narrative creates a sense of comfort and peacefulness through the depiction of the four men on board the cruising yawl at the end of the day and the description of how both it, and the men on it, had "come to rest." In addition, the narrator speaks in an almost hypnotic voice with a clear, definite rhythm that lulls and soothes. Note the opening paragraph of this story:
The Nellie, a cruising yawl, swung to her anchor without a flutter of the sails, and was at rest. The flood had made, the wind was nearly calm, and being bound down the river, the only thing for it was to come and wait for the turn of the tide.
Note how the details of the image created in this sentence help to reinforce the peaceful atmosphere: there is not even a "flutter" in the sails, and the wind was "nearly calm," and all that can be done is to wait in an atmosphere of peace and quiet. Of course, what slightly contrasts with this atmosphere is the brooding sense of imminent darkness that grows throughout the tale.