Turn from Byron to Shelley. From the infernos of introspection to the Edens of space. From the majesty of Cain to Israfel mounted on Pegasus. From Manfred to the Witch of Atlas.
Shelley, divine interstellar flaneur, musical, mystical avatar, runner from Antares to a goal-post set in the Infinite, whose fast feet set suns to singing, whose hair was woven by the seven daughters of Atlas and Pleione, whose eyes were plebescites of the Eternal: Shelley the ethereal melodist, a winged Prometheus nailed to the Caucasus of Time!
Poets are intercalations. A Poet is an eagle with the rainbow in his talons. In the reign of the Ugly they are interregnums. Among all the countless children of the Unimaginable Spirit only poets reach aesthetic puberty—and then die. They reach the threshold of the wonder-day of Beauty, and their lives are stanched in their sockets. A few—Shelley among them—have raped Aphrodite and Helena. The others marry the strumpet Muses.
What is the natal country of the poets? That country bounded by Nowhere and reached by staying home—the Imagination. The Imagination, a marvelous multi-colored drugget that covers the rough and splintered floor of Reality; a haunted chateau; a vestibule between Time and Eternity; the red Pantheon of Lucifer; the candle-gleam of Science; the flambeau of the lover;  the glistering west-dust of a hidden, innominate Sun; the seignory of the untrammelled instincts; the fief of unsanctified dreams; the palfrey that carries us toward nebulous spiritual hells; the plasma of gods; Puck strapped to the back of Balaam’s ass; the Shelley of mental faculties; the avatar of the emotions; a golden key that unlocks the Bastiles of logic; a ladder to the Fourth Dimension.
Men are only men; but poets are poets, and at birth they are given in marriage to Ariel and Lilith and they live with them in the unacred Imagination.
Three things mark Shelley: lyrical ecstacy, the ethereal imagination and the revolution spirit. His ecstatic lyricism would have struck music from a shadow. His ethereal imagination was so rarified and of such a degree of potency that at its touch all matter exhaled its soul and fell away into flakes of light and scintillant atomic pulsations. His rebellion was so deep rooted and imperious that to sound the tocsin to the planet he seized for cymbals Time and Space, planted his red standard on the North Star—and then, divine lover that he was, sat down and wept and sang.
In the sublime war of man against Reality man has but one weapon, the imagination. The ethereal imagination is the highest form of the evolution of the transfiguring and sublimating power of images. It marks the boundary line between the mystery of matter and the mystery of spirit. It is the fine, volatilized plasma  of an esoteric dimension, of a world where the truths hinted at by the x-ray and radium are true for the human mind and body.
In the realms of the ethereal imagination—a realm in which Shelley took the highest sustained flight—we are remote from home, which is matter. It is the exit from the shanty of place to a palace in the moon. We roll the stone of reality away and climb the steps of the air, hallucinated by light, horizoned by the ecliptic of formless worlds. Everything is fulgurant and lacinating in Shelley’s poems. He forged bolts of lightning with an infinite number of moonbeams. With units of light and color captured from remote moods moulded his characters.
Shelley’s mind was primitive. He saw the world with the startled eye of the child. From the cocoon of the familiar he liberated the Butterfly with the million-striated wings. The trailing mane of his imaginative memory swept through nebulæ and foreworlds. He had a will-o’-the-wisp in his brain. From Queen Mab to The Triumph of Life is an evolution of the mirages of the unreal. On the ruins of Reality rose the sublime thousand-winged chimeras of his fancy and through the smoke and flame of assaulted wrongs his face glows like a bethlehemic light set in the heart of a night of storm. From the stem of Reality images detach themselves in showers and float in the azure of his imagination. Apparitions woven of imponderable stuffs rise in the empyrean and fade against marmoreal  dawns and firmaments of jasper and porphyry. The precipices of the wind knew him and the thundercloud halved itself like the Red Sea so that he might pass through.
Swinburne celebrated the death of Charles Baudelaire in an immortal poem and Shelley in Adonis deified Keats, but no one has or ever can sing the song that shall deify Shelley. Like Shakespeare and Hugo his is an auto-apotheosis.
To have written the Prometheus Unbound Shelley must have gathered his impetus in the Infinite for a march on the Eternal. It is the highest imaginative altitude yet taken by the human mind. From the opening speech of Prometheus to the finale of Demogorgon there is the urgent and precipitated flight of a god incandescent with passionate inspiration. The mighty forces of the knowable universe are held in the knotted grip of that mind as Jupiter holds the thunderbolts. He fords the ether from constellation to constellation. He walks the platform of trans-ethereal silences. Echoes and voices of his own creation stream to the summit of his godhood and a tongue is put in the Wound of the earth and the spirits of the dead oceans of the Moon crawl to his eye to slake their thirst in its beams.
Shelley’s creation of Prometheus is Shelley himself, and the whole of Prometheus Unbound is the soul history of Shelley himself; the hypostatic union of the Poet with the soul of Nature. 
He had never been born unto Reality, but reigned an unconceived god in the womb of the Eternal Mother. And his poems are measured in the perpetual rise and fall of her bosom.
Benjamin de Casseres.
Source: The Poetry Journal, July 1916, Vol. 6 No. 1, pp. 19 – 23