Nelson's Column construction. 1840s calotype salted paper print of scaffolding around the lower part of Nelson's Column in Trafalgar Square, London, UK. This monument was built to commemorate the death of Admiral Horatio Nelson at the Battle of Trafalgar in 1805. Designed by the architect William Railton, the monument was built between 1840 and 1843. Photographed in 1843 by British pioneer of photography William Henry Fox Talbot (1800-1877). Calotypes used paper coated with silver iodide to capture photographic images. Salted paper prints were produced using paper coated with silver chloride. Both processes were invented by Talbot.