According to legend, Cassiopeia, Queen of Ethiopia, had angered the Nereids by boasting that she and her daughter Andromeda were as beautiful as they. To punish her presumption, Neptune sent flood waters and a sea-monster to ravage the land. Learning from an oracle that his daughter must be sacrificed to the monster in order to save his people, King Cepheus had Andromeda chained to a rock by the sea. The hero Perseus saw her and, moved by her beauty, rescued Andromeda, sweeping her skyward on his winged horse, Pegasus. The luminous heavens, illusionistically conceived to be seen from below, open to reveal Minerva and Jupiter seated on gold-tinged clouds.
The painting is a study for one of Tiepolo’s four ceiling frescoes in the Palazzo Archinto, Milan, which was destroyed by bombing in 1943. A fresco in the main salon, representing an Allegory of the Arts, bore the date 1731.
Source: Art in The Frick Collection: Paintings, Sculpture, Decorative Arts, New York: Harry N. Abrams, 1996.