Cloud study, c 1840.
© National Media Museum / Science & Society Picture Library
Waxed paper negative by Sir John Herschel (1792-1871). Herschel, an English astronomer, mathematician and chemist, was the son of Sir William Herschel (1738-1822). He introduced 'hypo' (thiosulphate) as a photographic fixative and discovered the cyanotype or blueprint proces in 1842.