From Julius Caesar Ibbetson’s ebullient watercolor of “Skaters on the Serpentine in Hyde Park”—their coats swaying as they glide over a swath of translucent ice, infusing the scene with a sense of immediate motion—to Édouard Manet’s textured monochromatic lithograph of a balloon, “In Celebration of Paul Mellon” is an exhibit whose scope reveals its benefactor’s profound impact. Mellon was a memorable 20th-century philanthropist and prodigious art collector, and the son of the great financier Andrew Mellon, who founded the nation’s art museum. After his father’s death, Paul Mellon assumed responsibility for the museum, presenting the collection to President Franklin Roosevelt in 1941. Today, as visitors gaze upon works like Paul Cezanne’s graphite self-portrait and Pablo Picasso’s stark and haunting “The Death of Harlequin,” they view the gifts of a man who firmly believed that the pieces belonged to all Americans. The rich collection conveys Mellon’s boundless generosity while also capturing the spirit of a man whose passion for art was so renowned. The exhibition is on view Mondays through Saturdays 10 a.m. to 5 p.m. and Sundays 11 a.m. to 6 p.m., to Sept. 18, at the National Gallery of Art, 6th Street and Constitution Avenue NW. Free. (202) 737-4215. nga.gov.