March 2021

12 Buckden Roundabout March 2021 a star less than 20° above the horizon because the variation in density of the atmosphere deviated the light from a straight line, giving an apparent shift in the position of the object. Despite Rowbotham ’ s success as a public speaker, his experi- ments received little attention. 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 naturalist and qualified surveyor Alfred Russel Wallace 2 accepted the challenge. Wallace, by virtue of his surveyor's training and knowledge of physics recognised the errors of the preceding experiments and made some crucial changes as fol- lows: 1. He raised the entire experiment by 13 ft 3 in (4 m) above water. In contrast, Rowbotham did his experi- ment only 8 in (20 cm) above water. This reduced the effects of atmospheric refraction. 2. He added a pole with two discs in the middle of the canal that could be used to see the "bump" caused by the curvature of the Earth between the two end points. Wallace wrote: “ On this bridge I fixed a large sheet of white calico, six feet long and three feet deep, with a thick black band along the centre, the lower edge of which was the same height from the water as the parapet of Welney bridge; so that the centre of it would be as high as the line of sight of the large six - inch telescope I had brought with me. At the centre point, about three miles from each bridge, I fixed up a long pole with two red discs on it, the upper one having its centre the same height above the water as the centre of the black band and of the telescope, while the second disc was four feet lower down. It is evident that if the surface of the water is a perfectly straight line for the six miles, then the three objects—the tele- scope, the top disc, and the black band—being all exactly the same height above the water, the disc would be seen in the telescope projected upon the black band; whereas, if the six - mile surface of the water is convexly curved, then the top disc would appear to be decidedly higher than the black band, the amount due to the known size of the earth being five feet eight inches, which amount will be reduced a little by refraction to perhaps about five feet ” . The following figures show Wallace ’ s prediction. The top pic- ture is what would happen if the Earth is curved, and the bottom is what would happen if the Earth ’ s is flat. When seen through the telescope, the bridge and the pole in the middle appeared like this: It was clear that both discs were seen above the black band, and Wallace ’ s hypothesis was correct. These results were suffi- cient for an independent referee to declare that Wallace had proved the earth was round and that he had won the bet. This, however, was not the end of the story. Hampden de- clared that Wallace had cheated and following a number of court cases was imprisoned for threatening to kill Wallace and for libel. To settle the argument once and for all, Henry Old- ham, a reader in geography at King's College, Cambridge, re- produced Wallace's results in 1901. Oldham used 3 poles fixed at equal height above water level. When viewed through a theodolite, the middle pole was found to be almost 3 feet (0.91 m) higher than the poles at each end. Oldham had proved unequivocally that the earth was round and this ver- sion of the experiment continued to be taught in schools until photographs of the Earth from space became available. References: https://en.wikipedia.org/wiki/Bedford_Level_experiment https://www.theflatearthsociety.org/library/books/Earth% 20Not%20a%20Globe%20%28Samuel%20Rowbothan%29.pdf https://flatearth.ws/bedford - level (Continued from page 11) Bedford Level Experiment 2 Alfred Russel Wallace OM FRS (8 January 1823 – 7 November 1913) was a British naturalist, explorer, geographer, anthropologist, biologist and illustrator.He is best known for independently conceiving the theory of evolution through natural selection; his paper on the subject was jointly published with some of Charles Darwin's writings in 1858.