Final answer:
The purpose of the outside source is to illustrate Japan's isolation in the 1800s.
Step-by-step explanation:
The purpose of the outside source used in this excerpt is to illustrate Japan's isolation in the 1800s. The lines in the excerpt convey a sense of distance and separation, suggesting that Japan is disconnected from the world. This aligns with the historical context of Japan's self-imposed isolation during the Edo period. The outside source helps to emphasize this theme and enhance the reader's understanding of the isolation experienced by Japan during that time.
Learn more about Purpose of outside source in 'kusai's The Great Wave'