Thought-provoking and intriguing, The Darker Side of Light: Arts of Privacy, 1850–1900, seen by this reviewer at the National Gallery of Art in Washington, DC, is the kind of exhibition museums should organize more often. It is primarily a works-on-paper show, featuring around one hundred prints, three drawings, four illustrated books, and ten sculptures. Including objects made during the last half of the nineteenth century, this display presents a broad range of artists: the French...