Stanza 1

The title "The Chambered Nautilus" refers to a sea creature that lives in the western Pacific and the Indian oceans and has a hard external shell, or exoskeleton. The creature lives in and is able to withdraw into the outermost compartment of its shell, which consists of sealed sections and is one of nature's best examples of a logarithmic spiral, one that grows at an exponential rate and appears to expand while it grows. Line 1 calls the nautilus a "ship of pearl," which combines a comparison to a human-made sailing vessel with a description of the pearly finish of the nautilus shell. The speaker then notes that "poets feign," or pretend, that the nautilus "Sails the unshadowed main," or the wide-open waters.

Lines 3, 4, and 5 continue the conceit, or extended comparison, of the nautilus to a ship, creating an image of a "venturous," or adventurous, wooden ship whose "purpled wings," or sails, fly on the "sweet summer wind." This description sounds like some kind of magical fairyland, and the speaker notes that the ship, or nautilus, sails to enchanted "gulfs." A gulf is a large, partially enclosed body of water, and the word gulf has a secondary meaning of "chasm" or "abyss." The speaker notes that "the siren sings" in these gulfs. This image refers to the beautiful and seductive water nymphs of ancient Greek mythology that sang so beautifully as to lure sailors to be destroyed on the rocks surrounding their island. Lines 6 and 7 continue this imagery, describing coral reefs that "lie bare." This image refers to the beautiful yet dangerous reefs that can destroy a ship but is also vaguely suggestive of the nude "cold sea-maids" who lie in the sun and dry their "streaming hair."

Stanza 2

Stanza 2 discusses the nautilus's wreckage and death in the past tense. In line 8, the speaker's conceit continues and expands as the nautilus is said to have "webs of living gauze," or sails. It is important to consider which part of the nautilus refers to the sails and which indicates the "ship of pearl." Logic would suggest that the sails, or "purpled wings" and "webs of living gauze," are the tentacles and head of the creature and that the pearly ship is the shell. In this stanza, however, the sails do not "unfurl," because the ship is "Wrecked" and the nautilus is presumably dead.

In lines 10 through 14, the speaker describes the nautilus's empty shell, continuing to use the comparison of a ship. The speaker discusses "every chambered cell," referring to the compartments and rooms of a ship as well as the sections of the nautilus's exoskeleton, which it makes as it grows larger, closing off old compartments and moving into new ones. The speaker describes these abandoned cells as expired locations where the nautilus's "dim dreaming life" used to dwell. Line 12 refers to the nautilus as a "frail tenant" constructing "his growing shell." Line 13 refers to the reader as "thee," suggesting that the empty shell lies directly in front of the reader. Line 14 describes the inside of the empty shell as having an "irised," or rainbow-colored, ceiling that has broken open and let the elements into what used to be a "sunless crypt," or coffin.

Stanza 3

Stanza 3 backtracks from the preceding description of the nautilus's death to describe in the past tense its lifelong "silent toil" to create protective compartments in its spiral shell. In this description, the speaker seems to abandon the comparison of the nautilus to a ship, although Holmes's choice of words is characterized by terms of human construction, such as "coil," "archway," "door," and "home."

Lines 15 and 16 emphasize the laborious repetition of creating the "lustrous" shell, and the following two lines state that each year the nautilus abandons its previous chamber in favor of a new one that it has created to accommodate its larger size. Line 19 describes this process as stealing, or moving sneakily, "with soft step" through the "shining archway" that divides the chambers, as though the nautilus were human. This process of personification, or assigning human qualities to an animal or object, continues in lines 20 and 21. The speaker describes the seal that the nautilus forms to block off its old chamber as an "idle door" ("idle" probably means "unused" in this context, as opposed to "useless" or "unproductive"). In line 21, the speaker explicitly compares the nautilus to a person, describing it as "Stretched in his last-found home" and noting that it "knew the old no more," or has shut out its past.

Stanza 4

In stanza 4, which changes to the present tense, the speaker addresses the nautilus directly and describes its effect on him. Line 22 thanks the nautilus for the "heavenly message" it has brought, and line 23 describes the creature as a "Child of the wandering sea," which is a mysterious image because it is difficult to envision the sea itself as wandering. Line 24 suggests that the nautilus is wandering or "forlorn" and has been cast from the lap of the sea as though the sea were its mother.

In line 25, the speaker reminds the reader that the nautilus is dead, but at the same time, he produces an image of a "note" coming from its "dead lips." The next line continues this thought by stating that the note born from the lips of the nautilus is clearer than that which "Triton" has blown from his "wreathèd horn." Triton is an ancient Greek demigod—or a being more powerful than a human but less powerful than a god—whose father is the sea god, Poseidon. Triton is usually portrayed as a merman, or a creature with the upper body of a man and the tail of a fish, although the name "Triton" came to be used for a host of other mythological mermen and mermaids. The "wreathèd horn" refers to Triton's great conch shell, which he blows like a trumpet to command the waves. In line 27, the speaker says that he listens to the clear note of the nautilus ring in his ear. In line 28, the speaker states that he hears the sound of the nautilus as a "voice that sings" in "deep caves of thought," which is an interesting image that ties to the description of the nautilus's many chambers.

Stanza 5

In the fifth stanza, the speaker addresses himself instead of addressing or describing the nautilus. In line 29, the speaker urges his "soul" to "Build thee more stately mansions," implicitly comparing the nautilus's chamber-building to the process of building expensive houses. Line 30 exclaims that the speaker should build the mansions amid the swiftly changing seasons, or because time rolls along rapidly. In line 31, the speaker tells himself to leave the "low-vaulted," or low-ceilinged, "past," and in the next line he wishes that "each new temple," a new and important metaphor suggesting the religious holiness of the chamber or house, be "nobler than the last."

Line 33 uses the phrase "Shut thee from heaven," which emphasizes the separation of the house or temple from the elements and from God, but the speaker paradoxically goes on to describe the ceiling as "a dome more vast" that increases until the speaker is "free." Line 34 suggests that the speaker achieves this ultimate freedom by releasing himself into heaven, or dying. The final line reinforces this interpretation, noting that the speaker, like the nautilus, will leave his "outgrown shell," which refers to the speaker's body as well as a house, "by life's unresting sea," as though the speaker's spirit will rise out of the shell of his body and into heaven.