This poem gives a mythical account of how the Avon Gorge was formed. Renaissance texts, like Edmund Spenser's The Faerie Queene, are Chatterton's model. Chatterton extends stories of Sabrina, goddess of teh river Severn, to the Bristol Avon and metamorphoses Sabrina's mother, Elstrid, to Bristol's St. Vincent's Rocks. The giant who kills them he turns into Snowdon.
The shaping principle of the poem is to narrate a traditional legendary action, human in its interest, and ties it convincingly to the local scene—in this case the Avon gorge, the most striking feature of Bristol topography. The effect is to make one feel that one's own local place enjoys a close and ennobling connection with ancient legend and its subsequent rich development in literature. Here as elsewhere, Chatterton's imagination means that Bristol is made more glorious and magnificent.
[…] Forth from Sabrina ran a river clear, Roaring and rolling on in course bismare; From female Vincent shot a ridge of stones, Each side the river rising heavenwere; Sabrina's flood was held in Elstrid's bones. So are they called; the gentle and the hind Can tell that Severn's stream by Vincent's rock's y-wrynde. The burly giant, he who did them sle, To tell Guendoline quickly was y-sped; When, as he strode along the shaking lea, The ruddy lightning glistered on his head; Into his heart the azure vapours spread; He writhed around in dreary cruel pain; When from his life-blood the red gleams were fed, He fell an heap of ashes on the plain; Still do his ashes shoot into the light, A wondrous mountain high, and Snowdon is it hight.
Chatterton's extrapolations from the legendary material to Bristol topography are so smoothly handled that one is surprised he did not take the next step, transforming Brutus himself to Bristol, for in Turgot and Rowley's "Discorse on Brystowe" we learn that "Josephus de Ascown saieth Brystowe is come from Bruytstowe or the place of Bruyt."