One starting point in examining the relationship between the ideas expressed in both of Hughes's works is to look at how he addresses African- American identity in the modern setting.
In Hughes's essay, he communicates how African- American artists should not stray from their racial identity. The opening of the young African- American artist who simply wants to be an "artist" provides the essay's thesis:
But this is the mountain standing in the way of any true Negro art in America--this urge within the race toward whiteness, the desire to pour racial individuality into the mold of American standardization, and to be as little Negro and as much American as possible.
Hughes suggests that artists of color must recognize that their own "racial world" is "as interesting as any other world." In these claims, Hughes suggests that being African- American has to be a source of pride for the artist of color.
This sense of joy about what it means to be African- American is communicated in "The Negro Speaks of Rivers." Hughes suggests that the soul of the African- American has "grown deep like the rivers." Such an identity has seen different stages of historical development. The Pyramids, the Nile, and Abraham Lincoln have come and gone. However, Hughes suggests that the "soul" of African- Americans still endures. African- American identity is a source of joy for Hughes. In this way, he creates a poetic complement to the idea in his essay. The need for pride in racial identity is a way to explore the relationship between the ideas in both of Hughes's works.