In 1673 French astronomer Jean Richer established that pendulum clocks calibrated in Paris, lose 2 min 28 sec per...
In 1673 French astronomer Jean Richer  established that pendulum clocks calibrated in Paris, lose 2 min 28 sec per day on the equator. The French were stumped, just like everybody else.

British scientist Issac Newton in 1697, in "Principia Mathematica" explained that gravity on the equator was effectively smaller due to rotation of the Earth, and together with Universal Attraction, this makes the Earth flattened at the poles by 1/230. 

50 years earlier René Descartes (Latinized form Cartesius) published his theory of planetary vortices (alternative to Universal Attraction), from which later French scientists deduced that that the Earth is elongated at the poles, like a cigar, a contradiction to Newton's theory.

This difference was not only a clear prediction that could be measured, but  could establish supremacy of the French scientists, so they launched a major expedition to the equator  in South America to measure the length of 1 degree of latitude and a minor one to the Arctic circle to do the same.

At the equator, over a distance of 215 miles (tilted 14 deg from the meridian), difference between 2 geodesic teams was 58 meters.
The angle between 2 observatories, at the ends of this distance, was 3°7'1". Reduced (to sea level) distance between them was 176,940 toises [1]), making one degree of latitude at the equator equal to  56,767 toises [2], 38 meters larger than modern value.

Measurements at Paris was 57,060 toises/deg (3 meters larger than modern value).

Measurements taken at Arctic circle [3] was 57,437 toises/deg (430 meters larger than modern value), 

This confirmed that Newton was right, and was one of the first major confirmations of his laws. I read somewhere that they did not have enough precision, and simply confirmed their bias. Clearly it's BS.

The story is surprisingly similar to the 1919  Arthur Eddington's expedition to South America to measure light deflection by the Sun, testing General Relativity. There were lots of accusations of confirmation bias there as well, but wikipedia says it was all kosher.

Modern value of one degree of latitude at the pole is 111.694 km, at the equator 110.574 km, for the difference of 1.120 km or 1%.

[1] 1 toise = 1.949 meters http://en.wikipedia.org/wiki/Toise
[2] The book says 56,753, the difference of  7 meters. Don't know why.
[3]  At Gulf of Bothina, in Lapland, the site of today's  Finnish-Swedish border.

http://books.google.com/books?id=G_xhdpclfRYC
http://en.wikipedia.org/wiki/French_Geodesic_Mission
http://en.wikipedia.org/wiki/Latitude#The_length_of_a_degree_of_latitude
http://en.wikipedia.org/wiki/Pierre_Louis_Maupertuis
http://en.wikipedia.org/wiki/Tests_of_general_relativity#Deflection_of_light_by_the_Sun
http://books.google.com/books?id=G_xhdpclfRYC

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