Over the course of the monologue, Crusoe uses a number of metaphors and similes to illustrate his desert island experience. For example, he compares his island to "a sort of cloud-dump" and its volcanic craters to "parched throats" that were "hot to touch." These comparisons make it clear that Crusoe has not found an island paradise: the weather's bad, and the landscape is dry, hot, and dangerous.
Elsewhere, metaphor conjures up exotic sights and natural phenomena, such as the "waterspouts" Crusoe witnesses at sea: "Glass chimneys, flexible, attenuated, / sacerdotal beings of glass." Readers who have never seen a waterspout (a tornado-like sea-storm) can probably picture a flexible glass chimney and have some idea of what Crusoe is describing. The second metaphor, "sacerdotal beings," compares the waterspouts to priestly figures. This may be because they are:
- tall and imposing
- quiet when witnessed from "far out"
- connected to the heavens (they have "their heads in cloud"
- made of water, which is symbolically linked with purity and holiness
Or all of the above!
Crusoe's figurative language also demonstrates his vivid imagination; he is, after all, a writer of sorts, one who's interested in "poems" and "philosophy." For example, he observes that the island's "Snail shells" visually resemble "beds of irises." Later, he converts this observation into a metaphor: "I tried / reciting to my iris-beds." His imagination seems to have changed one thing into another, transformed shells into flowers—and personified them as a conscious audience. He's even reciting them a poem about flowers! Maybe island solitude is playing tricks with his mind. Or to put it another way: maybe Bishop is implying that eccentric, "poetic" thinking is a product of extreme solitude.
Later, metaphors and similes illustrate Crusoe's growing fixation on islands—which, in turn, illustrates his deepening isolation. At night, he dreams of "islands spawning islands, / like frogs' eggs turning into polliwogs / of islands." Even in waking life, a whole cluster ("archipelago") of islands seems to swim in his "blood" and spring forth from his "brain." While these descriptions also attest to the vividness of Crusoe's imagination, they suggest that, after a certain point, he can imagine only more loneliness—only variations on his current solitude.