Revolutionary France .281795.E2.80.931812.29 Units of measurement in France

a clock of republican era showing both decimal , standard time.

the french revolution , subsequent napoleonic wars marked end of age of enlightenment. forces of change had been brewing manifest across of france, including way in units of measure should defined. savants of day favoured use of system of units inter-related , used decimal basis.

there wish units of measure should people , time , therefore not dependent on artefact owned 1 particular nation. tallyrand, @ prompting of savant condorcet, approached british , americans in 1790s proposals of joint effort define metre. in end, these approaches came nothing , france decided go alone .

decimal time introduced in decree of 5 october 1793 under day divided 10 decimal hours , hour 100 decimal minutes , decimal minute 100 decimal seconds . decimal hour corresponded 2 hr 24 min, decimal minute 1.44 min , decimal second 0.864 s.

the implementation of decimal time proved immense task , under article 22 of law of 18 germinal, year iii (7 april 1795), use of decimal time no longer mandatory. on 1 january 1806, france reverted traditional timekeeping.

the paris meridian, passes through observatoire de paris. metre defined along meridian using survey stretched dunkirk barcelona.

the metric system of measure first given legal basis in 1795 french revolutionary government. article 5 of law of 18 germinal, year iii (7 april 1795) defined 5 units of measure. units , preliminary values were:

the metre, length – defined being 1 ten millionth of distance between north pole , equator through paris
the are (100 m) area [of land]
the stère (1 m) volume of firewood
the litre (1 dm) volumes of liquid
the gram, mass – defined being mass of 1 cubic centimetre of water

decimal multiples , submultiples of these units defined greek prefixes - myria , kilo , hecta (100), deka - , latin prefixes - deci , centi , milli . using cassini s survey of 1744, provisional value of 443.44 lignes assigned metre which, in turn, defined other units of measure.

the final value of metre had wait until 1799, when delambre , mechain presented results of survey between dunkirk , barcelona fixed length of metre @ 443.296 lignes. law 19 frimaire viii (10 december 1799) defined metre in terms of value , kilogram being 18,827.15 grains. these definitions enabled construction of reference copies of kilogram , metre, used standards next 90 years.

at same time, new decimal-based system angular measurement implemented. right angle divided 100 grads, in turn divided in 100 centigrads. arc on earth’s surface formed angle of 1 centigrad 1 kilometre.