The poem
'Tis not ev'ry day that I Fitted am to prophesy: No, but when the spirit fills The fantastic pannicles, Full of fire, then I write As the Godhead doth indite. Thus enraged, my lines are hurl'd, Like the Sibyl's, through the world: Look how next the holy fire Either slakes, or doth retire; So the fancy cools:--till when That brave spirit comes again.