After the French Revolution, France was changed and changing. Old units of measurement were too linked to the previous regime, they had to be thrown out. Lengths varied region to region and country to country, but that was old France; in 1790, just one year after the French Revolution, they started – on a surprisingly long journey – to find a universal length. The metre.
The first idea was a pendulum which would swing to and fro in a total time of 1 second, the length of the pendulum would become the metre. The length was close to other lengths in use such as the English Yard. Unfortunately a pendulum that performs a full swing in 1 second in Paris would do the same motion in a different time if moved. A pendulum in London moves at a different speed to one in Paris. The idea did not gain traction.
June 17 1771 King Louis XVI charged a commission chosen by the Academy of Sciences to pursue and create the metre. The commission was a group of 12 dedicated scientists and mathematicians, the leader was Jean Charles de Borda. Jean-Charles de Borda was an eminent French Mathematician, physicist and fan of decimalisation. He detested the idea of the second-pendulum because of both its errors and a more personal gripe, the second was a unit of time, and time wasn’t measured in units of ten, it just wasn’t decimal enough. He preferred the system of 10 hours to a day, 100 minutes to an hour and 100 seconds to the minute and so on. Unfortunately for him this decimal time system was being used in exactly 0 countries, so he and the 11 others looked into alternatives.