Interestingly, the word nautilus is derived from the Greek word for sailor because Greeks thought this shell could really move on the surface of the water, using a membrane as its sail.  The first three stanzas, a meditation upon the life and death of the nautilus, employ the Greek definition of the nautilus as an extended metaphor.

• In stanza 1, the nautilus is compared to a "ship of pearl."  "
• In stanza 2, the "webs of living gauze" are compared to sails that no longer "unfurl."
• In stanza 3, the nautilus is compared to a person who has shut out the past:  "Stretched in his last-found home, and knew the old no more."
• In stanza 4, the poet begins an apostrophe.  Addressing the nautilus, he compares it to a "Child of the wandering sea" who is cast from the "lap" of its mother, the sea.  Another metaphor is "the deep caves of thought"
• In stanza 5, the speaker addresses himself rather than the nautilus.  urging his soul to build "more stately mansions," thus comparing the chamber building of the nautilus to a building of houses.  The religious holiness of the chambers is implied with the metaphor of "new temple."

The most important metaphor is that of comparing the soul to the nautilus that frees itself from its outgrown shell of his body when he rises to heaven. For, the nautilus brings a "heavenly message" that conveys how people should expand their lives just as the nautilus does its.  In the last lines of the poem, Holmes urges people to expand their horizons--"Leave thy low-vaulted past!"--and achieve spiritual freedom--"a dome more vast"