The document discusses photography during the Civil War. It describes how the daguerreotype, invented in 1839, was the first widely used photographic process but was later replaced by the wet-collodion process in 1851, which used glass plates. The document also outlines how photographer Mathew Brady pioneered photojournalism during the Civil War by gathering a team of photographers to document scenes from the war, including images of fallen soldiers, which shocked the American public and helped establish photography as an important new medium.