This intriguing word is found, for example, in Section 5 of this impressive poem that does so much to define America and the American spirit that we can see emerging from the founding of this country. In this section of the poem, the word "kelson" is used in the context of an epiphany that the narrator experiences after an erotic encounter with his own soul. Note what he says in the following quote:

Swiftly arose and spread around me the peace and knowledge that pass all the argument of the earth,
And I know that the hand of God is the promise of my own,
And I know that the spirit of God is the brother of my own,
And that all the men ever born are also my brothers, and the women my sisters and lovers,
And that a kelson of the creation is love...

The speaker experiences a profound religious understanding of how the world operates and that God is an intrinsic part of him. In addition, he feels a sense of unity and fellowship with all other humans. This epiphany culminates with the central idea that the "kelson" of all creation is the force of love. A kelson is a beam that help keeps a ship steady. Through this metaphor, Whitman is therefore stating that love is a force that helps keep the world steady.