The Bedford Level Experiment was a series of observations carried out along a six-mile length of the Old Bedford River on the Bedford Level, Norfolk, England, during the nineteenth and early twentieth centuries. It was an attempt to demonstrate that the Earth was flat. Early results seemed to prove this contention, but most later attempts to reproduce the observations firmly supported the conventional view that the earth is a sphere.
At the point chosen for all the experiments the river was a slow-flowing drainage canal running in uninterrupted straight line for a six-mile stretch to the north-east of the village of Welney. The most famous of the observations, and the one that was taught in schools until photographs of the Earth from space became available, involved a set of three poles fixed at equal height above water level along this length. As the surface of the water was assumed to be level, the discovery that the middle pole, when viewed carefully through a theodolite, was almost three feet higher than the poles at each end was finally accepted as a new proof that the surface of the earth was indeed curved.
The first investigation was carried out by Samuel Birley Rowbotham (1816-1884), the president of the Flat Earth Society, in the summer of 1838. He waded into the river and used a telescope held eight inches above the water to watch a boat with a five-foot mast row slowly away from him. He reported that the vessel remained constantly in his view for the full six miles to Welney bridge, whereas, had the water surface been curved with the accepted circumference of a spherical earth, the top of the mast should have been some eleven feet below his line of sight.
Rowbotham repeated his experiments several times over the years but his discoveries received little attention until, in 1870, a supporter by the name of John Hampden offered a wager that he could show, by repeating Rowbotham’s experiment, that the earth was flat. The noted naturalist and qualified surveyor Alfred Russel Wallace accepted the wager. Wallace, by virtue of his surveyor’s training, avoided the errors of the preceding experiments and he won the bet. Hampden, however, published a pamphlet alleging that Wallace had cheated and sued for his money. Several protracted court cases ensued, with the result that Hampden was imprisoned for libel.
In 1901 Henry Yule Oldham, a geography reader at King's College, Cambridge, conducted the definitive experiment described in Method, above.
The planists, however, were not yet defeated: On 11 May 1904 Lady Anne Blount hired a commercial photographer to use a telephoto lens camera to take a picture from Welney of a large white sheet she had placed, touching the surface of the river, at Rowbotham’s original position six miles away. The photographer, Edgar Clifton from Dallmeyer’s studio, mounted his camera two feet above the water at Welney and was surprised to be able to obtain a picture of the target, which should have been invisible to him given the low mounting point of the camera. Lady Blount published the pictures far and wide and, apart from some hypothesising concerning refraction, and dark hints of collusion between Blount and Clifton, these have not been explained.