The Bedford Level Experiment

Did you know that canals helped measure the curvature of the earth? We unearth a story played out along a sleepy waterway in the east of England.

Bedford level experiment


Conspiracy theories, lawsuits and death threats aren’t the first things that come to mind when thinking of the Old Bedford River, that man-made offshoot of the Great Ouse. Yet for almost a decade – starting in 1838 when the writer, inventor and Biblical literalist Samuel Rowbotham tried to prove that the Earth was flat – that’s exactly what transpired.

Anyone familiar with the area won’t be surprised that Rowbotham chose the Cambridgeshire Fens for his tests. If you’ve looked across that vast expanse of eastern flatness you may also have wondered whether or not Earth is indeed round or an endless pancaked horizon. It was this perceived spherical fallacy that the 22-year-old set out to disprove one day in 1838 when the waters of the Bedford levels were typically stationary.

For his initial experiment, Rowbotham waded into a calm drainage canal and watched through a telescope, held at exactly eight inches above the water, as a small rowing boat with a flag on its mast travelled away from him towards the Welney Bridge, six-miles away. Based on the planet’s assumed circumference of 25,000 miles he had calculated that if the Earth were round then the vessel would fall from sight by eight inches in the first mile and continue to decline to 24 feet by the time it reached its destination, and therefore both flag and boat would have disappeared.

As he suspected, this was not the case. Rowbotham could still see the boat through his lens as it travelled under the bridge. Writing about the experiment years later in his book Earth Not a Globe (under the suitably eccentric pseudonym ‘Parallax’) he stated, “Every necessary condition had been fulfilled, and the result was to the last degree definite and satisfactory.” He conducted a number of similar experiments, all of which came to the same conclusion – Earth was indeed flat.

There was, however, one condition that he had failed to take into account and that’s the effect of atmospheric refraction – the deviation of light as it passes through the atmosphere, which can cause objects close to the ground to appear elevated.

John Hampden, the wealthy son of a Protestant rector and a supporter of Rowbotham’s work, also failed to consider this when confidently making a wager in 1870 in the journal Scientific Opinion that he too could prove that Earth was flat by roughly reproducing the same experiment. Alfred Russel Wallace, a qualified surveyor and the co-discoverer of the theory of evolution by natural selection, was happy to accept the bet in order to end the discussion and earn himself £500 in the process.

Hampden requested that the same stretch of water be used and Wallace accepted. Although unaware of Rowbotham’s previous effort, Wallace was aware of the laws of physics and thus made adjustments to counter atmospheric refraction. His version of the experiment involved a large sheet being fitted to the Old Bedford Bridge, which could be viewed from Welney Bridge, and crucially he set his sight line 13 feet above water. He also positioned a tall pole at the halfway mark so that the peak of the curve could be witnessed between the two points, and the sheet clearly below the sight line. An independent judge was happy that Wallace had successfully debunked the flat Earth theory.

So aggrieved was Hampden by his defeat that he continued to harass Wallace for more than a decade. He demanded the return of his wager, and subjected the British naturalist to years of threats, hounding the societies Wallace belonged to, his friends and even his wife. Hampden was eventually imprisoned for his threatening behaviour.

But this was not the end of the story. In the early 20th century both Henry Yule Oldham, a geography lecturer at King’s College, Cambridge and Lady Elizabeth Anne Blount used the Bedford Levels to recreate their own versions of the experiment. Oldham set out to prove the planet’s curvature and Blount, who would go on to be a key figure in the early day of the Flat Earth Society, to prove its flatness.

While neither side were ever convinced by each other’s arguments or scientific rigour, one thing we can be sure of is the importance of this particular stretch of water and its part in fuelling a debate that’s as old as the Earth is flat/round.

Joe Rampley