Bedford Level experiment

From Wikipedia, the free encyclopedia

The Bedford Level Experiment is a series of observations carried out along a six-mile (9.7 km) length of the Old Bedford River on the Bedford Level, Norfolk, England, UK, during the nineteenth and early twentieth centuries. It was an attempt to determine …


3 thoughts on “Bedford Level experiment

  1. *I don’t know why I bothered*

    …. the shape of the Earth. Early results seemed to prove the Earth to be flat, but most later attempts to reproduce the observations firmly support that the Earth is a sphere.

    At the point chosen for all the experiments the river is a slow-flowing drainage canal running in an uninterrupted straight line for a six-mile (9.7 km) 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 (0.91 m) higher than the poles at each end was finally accepted as a new proof that the surface of the earth was indeed curved.

    Earth’s curvature
    Below is the method that Samuel Birley Rowbotham used for calculating the rate at which the spherical earth curves.

    “If the earth is a globe, and is 25,000 English statute miles in circumference, the surface of all standing 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 following diagram:

    Earth’s rate of curvature
    “Let the distance from T to figure 1 represent 1 mile, and the fall from 1 to A, 8 inches; then the fall from 2 to B will be 32 inches, and from 3 to C, 72 inches. In every mile after the first, the curvature downwards from the point T increases as the square of the distance multiplied by 8 inches. The rule, however, requires to be modified after the first thousand miles.
    “The following table will show at a glance the amount of curvature, in round numbers, in different distances up to 100 miles.
    Statute Miles Away Maths = Drop
    1 1 x 1 x 8 = 8 Inches
    2 2 x 2 x 8 = 32 Inches
    3 3 x 3 x 8 / 12 = 6 Feet
    4 4 x 4 x 8 / 12 = 10 Feet
    5 5 x 5 x 8 / 12 = 16 Feet
    6 6 x 6 x 8 / 12 = 24 Feet
    7 7 x 7 x 8 / 12 = 32 Feet
    8 8 x 8 x 8 / 12 = 42 Feetmultiply Feet
    9 9 x 9 x 8 / 12 = 54 Feet
    10 10 x 10 x 8 / 12 = 66 multiply
    “To find the curvature in any number of miles not given in the table, simply square the number, multiply that by 8, and divide by 12. The quotient is the curvation required.”

    Rowbotham’s use of the formula
    The diagram on the right shows the rhetorical use he often made of these numbers to demonstrate in this case that Great Orme Head would be 872′ below the horizon as seen from the Isle of Man. Note that the sloping lines are drawn from sea level not from the hills or the observer….

    *theres more, of course, but I’m not going to add it here. L*


  2. I don’t know if it is just me but when I come over to read your posts I can only see the first five or six lines?! The above, for example, finishes with:

    “…It was an attempt to determine…”

    And yes, I have clicked to make sure it isn’t just a ‘read more’ situation 😉

    Thought I would let you know *smiles*


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