Therewith the Angel left him, and Desiderius was aware of but the walls and pillars of the cloister, and the bright vast plain, and, far away, the city of Sarras glittering, and the smoke sleeping like a small blue cloud above it.  And the coming and going of the Angel was after this manner.  Desiderius perceived him, bright in the brightness of the sunshine, as one perceives a morsel of clear ice floating in clear water; and when Desiderius saw him no more it was as though the clear ice had melted into the clear water.