This short chapter is told from the perspective of Ahab’s internal monologue, and has him sitting alone in his cabin, reciting to himself that, although Starbuck appears worried about the Pequod’s new mission, Ahab will exact revenge against Moby Dick, and “dismember” his “dismemberer.” Ahab vows that “the path to his fixed purpose is laid with iron rails, whereon his soul is grooved to run,” meaning he will stop at nothing to achieve his goal of killing Moby Dick.
A beautiful sentence in the novel—that Ahab’s purpose “is fixed . . . with iron rails, whereon his soul is grooved to run.” One of the particularly exciting features of the novel is its insistence on densely-patterned, “poetic” language, in descriptions of internal states and external landscapes. This sentence is a grand example of Melville’s descriptive abilities (not to mention the importance of trains at the time of the novel's writing).