The "Flat Earth" Bedford Level Experiments

Introduction

Chronology

The Bedford Level Experiments

"The issue was the relatively straightforward one of whether the Earth was flat (as the Zetetics held) or round (the Globularists). It's tempting from the comfort of a 21st century scientific perspective to laugh at the Zetetics, but we should perhaps be inclined to a little humility. The Zetetic philosophy was essentially one of 'proceeding by inquiry', which meant that any proof that the Earth was round would have to be the result of an experiment, not simply calculation. The world looks flat (just as the sun seems to orbit the earth) so it should be presumed flat unless it could be demonstrated otherwise.

The first attempt at an experiment was in 1838, when one Samuel Birley Rowbotham ('Parallax') made observations along the Old Bedford Level, one of Vermuyden's finest drainage constructions and which, from Welney, runs dead straight for six miles. Rowbotham was a convinced flat-earthist, which may have influenced his observational technique.

But nevertheless, from Welney Bridge he clearly saw (through a telescope) barges on the river some six miles distant. In fact, because of the curvature of the earth, from ground level looking over a flat surface, you can see no more than three miles -- his barges should have been well below the horizon. The Zetetics concluded erroneously that the earth was flat, and everything went quiet until 1870.

There were doubtless many scientists around who could have pointed out that Rowbotham's results are comfortably explained by the refraction of light close to a warm surface, the basis of many desert mirages.

Note: John Harvey emailed in July 2018 saying that reference above to a warm surface is incorrect, and the explanation should read "by the refraction of light close to a cool surface (the water) which causes the light to be refracted downwards". John also gave a detailed explanation of this for which I'm grateful and which I'll make available later.

But no one seemed to have the stomach for more experimenting until Alfred Russel Wallace, noted for espousing the new theory of evolution and hence used to the impolite cut and thrust involved, set up a rather more elaborate experiment. In part, this was because one John Hampden of Swindon had underwritten a wager of some £500 that a new experiment would establish the flatness of the earth for all time.

Three barges were used, on each of which was erected a straight rod, all the same height. The barges were moored two miles from each other along the same stretch of water. The tops of the rods were thus all the same distance above the surface of the earth. Using a theodolite, Wallace sighted from the top of the first rod to the top of the third. If the earth was flat, the top of the middle rod would lie on the same line.

In fact, because the earth was curved, the third rod was lower than the second: the second marker was a clear 32 inches above the line from the first to the third (sometimes reported to be five feet -- doubtless to emphasise the clear victory for the Globularists). This makes the diameter of the earth 7920 miles -- pretty good for 1870, as we now believe that the earth's equatorial diameter is 7926 miles (the earth isn't a perfect sphere, and has different diameters at different places).

Unfortunately for Wallace, but fortunately for those of us who are enjoying the story, the Zetetics (also known as the 'planists', by the way) looked at the same results and somehow managed to convince themselves that a trick of perspective was involved and that this did, after all, prove that the earth was flat! John Hampden refused to pay up, and the matter went to court some six years later. In a wonderful instance of jurisprudential cunning, the presiding judge declined to rule on what might be deduced from the experiments and contented himself with adjudging that such wagers were not legally binding! Hampden responded badly to a verdict that had, after all, saved him £500. He became obsessed and conducted a campaign of vilification against Wallace for the rest of his life, which led to several prosecutions for libel and accompanying prison sentences.

As so often happens when people disagree, neither side ever managed to convince the other -- indeed, the Flat Earth Society continued in being until the 1980's. What happened thereafter was that newcomers simply repeated the experiment associated with what they wanted to prove. In 1901, H. Yule Oldham repeated the Wallace experiment pretty exactly and got the same result, which he reported to the British Association for the Advancement of Science. In 1904, a Lady Blount repeated essentially the Rowbotham experiment with the added value of new-fangled photography: at least her result was demonstrable, and didn't rely on hearsay. This time, she photographed a white sheet hanging two feet above the water, six miles away -- just as Rowbotham had (and for the same reasons) she could see the theoretically hidden bottom of the sheet, and what's more its reflection in the water!

We may laugh now, but it is hard to disbelieve the evidence of our eyes, and the Zetetics were not fools. One modern analogy might provoke some reflection. The Bedford Level experimenters used the river because it was flat and straight. As with us, they looked around and saw jagged mountains, ocean trenches and very little flatness -- the river was a godsend. But in fact, considering the scale, compared to a billiard ball the earth is several orders of magnitude smoother on its surface!"

Appendix