In the 1820s Blake illustrated The Divine Comedy by the medieval poet Dante Alighieri. In this poem the pilgrim Dante, with Virgil (in blue), pass through hell and then climbs the Mount of Purgatory towards the Earthly Paradise on its summit.
The mountain was created when Satan fell from heaven into the earth’s centre. It rises at the opposite pole to the city of Jerusalem. Blake’s vision, in Jerusalem, of England in a fallen state has a parallel in Dante’s vision. Even seeing ‘clouds unfold’ is an optimistic sign of ultimate recovery from the fall.