The speaker in "Song of Myself" observes and participates in five American scenes. For the scenes other than the one about the martyr, describe...

The scenes you refer to are, I assume, the episodes at the end of the section about heroism. Whitman says, “I understand the large hearts of heroes, / The courage of present times and all times.” What he means is that heroism is just another part of the poet's universal co-mingling with all life. It is interesting to note, however, that the people he calls "heroes" are very different. Let's examine them one by one:

1. 
   The steamship skipper: He is a hero because he will not give up. Whitman evokes this through the use of telling detail: there is the "crowded and rudderless" deck of the derelict wreck he has come across, the chalkboard on which he writes, "be of good cheer, we will not desert you," the look of the people on the wreck, the "lank, loose-gown'd women" and "sharp lipp'd men." He saves the people on the wreck: Whitman says "All this I swallow, it tastes good, I like it well, it becomes mine, / I am the man, I suffer'd, I was there.” 


2. 
   The slave: Whitman describes a beaten slave, wincing "at the bite of the dogs," clutching at "the rails of the fence, my gore dribs, thinn'd with the ooze of my skin, / I fall on the weeds and stones.” The slave is a hero because of his forbearance and downtrodden state: Whitman says "I do not ask the wounded person how he feels, I myself become the wounded person,” an expression of the unlimited empathy of the poet.


3. 
   The fireman: Whitman describes a fireman, injured while fighting a fire—“Tumbling walls buried me in their debris”—yet he is saved by his comrades: “I heard the distant click of their picks and shovels, / They have clear'd the beams away, they tenderly lift me forth.” The fireman is a hero because he gave his all for his comrades; after he is saved, it is as if he is in heaven: “White and beautiful are the faces around me, the heads are bared of their fire-caps, / The kneeling crowd fades with the light of the torches.” 


4. 
   The artillerist: The artillerist recalls the siege of his fort: “I take part, I see and hear the whole, / The cries, curses, roar, the plaudits for well-aim'd shots, / The ambulanza slowly passing trailing its red drip,” details that recall the chaos of battle. The artillerist is a hero because of his coolness under battle.

The different characteristics of these heroes—faithfulness, forbearance, sacrifice, and bravery—are both an inspiration to the poet and qualities he already embodies. Each hero can be understood as another face of the poet.