This advertisement made it as clear as day.

I would go as cabin-boy.
I had taken Pepper into my confidence again; I had told him the story of my love for Miss Glentworth, with all its harrowing details; and now conceived it judicious to confide in him the change about to take place in my life, so that, if the Rawlings went down in a gale, my friends might have the limited satisfaction of knowing what had become of me.
Pepper shook his head discouragingly, and sought in every way to dissuade me from the step.

He drew a disenchanting picture of the existence of a cabin-boy, whose constant duty (according to Pepper) was to have dishes broken over his head whenever the captain or the mate chanced to be out of humor, which was mostly all the time.

But nothing Pepper said could turn me a hair's-breadth from my purpose.
I had little time to spare, for the advertisement stated explicitly that applications were to be made in person within four days.

I trembled to think of the bare possibility of some other boy snapping up that desirable situation.
It was on Monday that I stumbled upon the advertisement.