In the mid-19th century, an off-beat form of spirituality swept the U.S. People turned to mediums and seances, desperate to reach dead loved ones, especially those lost during the Civil War. Peter Manseau, curator of religion at the Smithsonian, describes how the advent of photography collided with the Spiritualist Movement, resulting in so-called “spirit photographs”. Manseau has written: “The Apparitionists: A Tale of Phantoms, Fraud, Photography, and the Man who Captured Lincoln’s Ghost”. Preserving memories through photos, Manseau says, offered new comfort to mourners...