The Old Bedford Level
The Old Bedford Level (or River) is one of the great drainage channels through the Cambridgeshire fens into Norfolk. In 1838, Samuel Birley Rowbotham ["Parallax"] made observations along a six mile stretch of this, between Welney and Old Bedford Bridges, which he claimed to show the earth was flat, leading to the formation of the 'Flat Earth Society' which survived until the 1980s! (I'm not sure where Old Bedford Bridge is, but the description seems to imply it is to the south-east of Welney Bridge, though the Old Bedford River runs from south-west to north-east.) Indeed some of the observations were confusing, probably due to ignorance about refraction caused by the air. If one sights along a level stretch of water, the curvature of the earth will conceal objects near the water surface, but Rowbotham regularly saw (with a telescope) barges and other objects at water level six miles away. He described these in his Zetetic Astronomy. In 1870, one of his followers, John Hampden of Swindon, bet £500 that a new experiment would demonstrate the flatness of the earth and Alfred Russel Wallace, the evolutionist, took up the bet, encouraged by Charles Lyell, the geologist. The first experiment was unsatisfactory. They then set up three equally spaced markers at the same height above the water and sighted from the first to the last. The middle marker clearly appeared about 5 ft above the line of sight. Unfortunately the two parties drew different conclusions from this observation, with the 'planists' thinking the position of the telescope crosshair indicated the observer's position. The resulting arguments wound up in court in 1876 where the judges carefully avoided deciding the shape of the earth and ruled that such wagers were not legally binding. Rowbotham explained the observation as a trick of perspective. Hampden became obsessed and conducted a life-long campaign against Wallace, leading to several prosecutions for libel and several prison sentences. In the early twentieth century, Elizabeth Anne Mould Williams, Lady Blount, took up the planist philosophy. In 1904 or 1905, she led an expedition to the Old Bedford Level to disprove Wallace's 'three pole trick'. She hired a competent photographer with a telephoto lens. This was set up two feet above water level and the photographer was surprised to see and photograph an object at water level six miles away and even its reflection in the water. [John Michell, Eccentric Lives and Peculiar Notions, Thames & Hudson, 1984 / Cardinal (Sphere), 1989, pp.21-30, 32 & 34-35.]
Similar observations elsewhere convinced other groups that the earth was curved upward and we were on the inside of a hollow sphere