The first half talks about his travels; he lists different experiences he has had. The first is going out hunting, "wandering amazed at my own lightness and glee" as he does. It is obvious that he loves being out in the mountains. Then he talks about being on a yacht, where he gives a "shout joyously from the deck". Next is when he went and digged clams with clam-diggers and "had a good time." The longest description in the first part is of a marriage between a trapper and a native american woman. He describes her "long eyelashes" and his "luxuriant curls and beard." All of these things he describes with joy, admiration, and an overall feeling of being happy to be alive and witness these things.
In the last section, Whitman describes how he heard a runaway slave outside of his door, and brought him into his own house. He drew up a bath for him, gave him some clothes to wear, a room "that enter'd from my own", and let him stay there for "a week before he was recuperated and pass'd north". Then, he states that the entire time the slave was there, he sat next to Whitman at the table, "my fire-lock lean'd in the corner." So, he sits at the same table with the slave, with no need for a gun, giving him his own clothes, and equal treatment.
I hope that helps! I've provided links below that might be useful also.