AdvertisementImpressionists With Benefits? The Painting Partnership Of Degas And Cassatt07:18Download AudioResumeMay 23, 2014Susan StambergfacebookEmailIn a letter, Mary Cassatt describes working on Little Girl in a Blue Armchair (1878) with Edward Degas. An X-ray of the painting reveals brush strokes unlike Cassatt's regular strokes. (National Gallery of Art)