Gabriel Mouton

Gabriel Mouton (1618 to 1694) was a French abbot and scientist, a doctor of theology from Lyon who was also interested in mathematics and astronomy. His 1670 book Observationes diametrorum solis et lunae apparentium proposed a natural standard of length based on the circumference of the Earth, divided decimally, and it was influential in the later adoption of the metric system. Building on Riccioli's measurement of the Earth at 321,815 Bologna feet to the degree, he defined a unit, the milliare, as one minute of arc along a meridian, with sub-units descending by factors of ten. His virga, a thousandth of a minute of arc, was about 2.04 metres and close to the Parisian toise, which was meant to ease acceptance. He suggested tying the standard to a pendulum, so that a pendulum one virgula long in Lyon would beat 3959.2 times in half an hour. Jean Picard and Huygens supported the idea in 1673 and the Royal Society studied it, while Leibniz independently made similar proposals. His milliare equals a nautical mile.