In the frame story part of the book, what details does Conrad include to create a sense of comfort and peacefulness?

The comfort comes from the detached narrator content with the lack of knowledge and the ability to put the knowledge in perspective at the end of the story. Check this out,

http://www.gradesaver.com/heart-of-darkness/q-and-a/discuss-the-structure-of-heart-of-darkness-and-how-it-affects-meaning-64393/