Nelsons Column under Construction, Trafalgar Square, London, April 1844.

UNITED KINGDOM - MAY 16: Nelson's Column under Construction, Trafalgar Square, London', first week of April 1844. Salt paper print from a calotype negative by William Henry Fox Talbot (1800-1877). This image suggests industrious advances in the construction of the column. However, when Talbot took this photograph the building work had actually been halted while the government took over the project from the building committee whose funds had run out. Talbot invented the negative/positive process for making photographs between 1835 and 1839. Any number of prints could be made of a single image from the negative. Dimensions: 225mm x 187mm. (Photo by SSPL/Getty Images)