Convicts' Cells

‘Point out my state-room, Sir,’ says Jonah now, ‘I’m travel-weary; I need sleep.’ ‘Thou lookest like it,’ says the Captain, ‘there’s thy room.’ Jonah enters, and would lock the door, but the lock contains no key. Hearing him foolishly fumbling there, the Captain laughs lowly to himself, and mutters something about the doors of convicts’ cells being never allowed to be locked within.