March 2021

11 Buckden Roundabout March 2021 Bedford Level Experiment Richard Storey, Secretary to the Buckden Local History Society When my son was a teenager one of his outdoor passions, apart from football, was geocaching. Thanks to his newly ac- quired GPS 1 device we would scour the local countryside or make deviations from journeys in the search of hidden caches of “ treasure ”. It took us to some interesting places but one that I always remember was out in the Fens, for it was here that we made an interesting discovery: thanks to the Fens it was proved that the earth is round! Believe it or not there were people in the 19th and well into the 20th century that still believed the earth was flat. One of the main proponents of this theory in the 1860s was Samuel Rowbotham (1816 - 1884). Rowbotham lived in the Fens and was an organiser of a socialist commune. It was here that Row- botham formulated his theories about a flat Earth and began to lecture on the topic. An eloquent and convincing speaker with good debating skills, Rowbotham consistently filled halls by charging sixpence a lecture. However, when challenged in Blackburn why the hulls of ships disappeared before their masts when sailing out to sea he failed to give an explanation and made a quick exit. In 1849 Rowbotham wrote a pamphlet called Zetetic Astronomy which drew upon the results of exper- iments he had conducted earlier. In his pamphlet he theorised the Earth is a flat disc centred at the North Pole and bounded along its southern edge by a wall of ice, Antarctica. The Sun and Moon were 3,000 miles (4,800 km) above Earth and that the "cosmos" was 3,100 miles (5,000 km) above the Sun and moon. Rowbotham wrote that “ If the earth is a globe, and is 25,000 English statute miles in circumference, the surface of all stand- ing water must have a certain degree of convexity—every part must be an arc of a circle. From the summit of any such arc there will exist a curvature or declination of 8 inches in the first statute mile. In the second mile the fall will be 32 inches; in the third mile, 72 inches, or 6 feet, as shown in the diagram below ”. ...After the first few miles the curvature would be so great that no difficulty could exist in detecting either its actual existence or its proportion... In the county of Cambridge there is an artificial river or canal, called the "Old Bedford". It is upwards of twenty miles in length, and ... passes in a straight line through that part of the Fens called the "Bedford Level". The water is nearly stationary—often completely so, and throughout its entire length has no interruption from locks or water - gates of any kind; so that it is, in every respect, well adapted for ascertaining whether any or what amount of convexity really exists ”. Rowbotham started his experiment in the summer of 1838. At this point the water is a slow - flowing drainage canal running in an uninterrupted straight line for 6 miles (9.7 km) to the north - east of the village of Welney. This makes it an ideal location to directly measure the curvature of the Earth. He waded into the river and used a telescope held 8 inches (20 cm) above the wa- ter to watch a boat, with a flag on its mast 3 feet (0.91 m) above the water, row slowly away from him. His diagram of the experiment is shown below: He reported in his writings that the vessel remained constantly in his view for the full 6 miles (9.7 km) 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 about 11 feet (3.4 m) below his line of sight. He sur- mised that the earth cannot be curved and therefore has to be straight. Unfortunately for him, however, he failed to take into account the laws of physics and the refraction of light. Had he been a sailor he would have known that one never took a fix on (Continued on page 12) Bedford Level Experiment 1 Global Positioning System The Old Bedford River, photographed from the bridge at Welney, Norfolk (2008); the camera is looking downstream, south - west of the bridge