Hippolyte LeSight

Hippolyte LeSight

geodesist; maker of the metre

Hippolyte LeSight, after a memoir frontispiece. The repeating-circle and meridian arc are the work; the distrust was other men's.

Born	28 January 1771
Died	1844; grave measured twice, disputed once
Nationality	French (the whole difficulty)
Field	Geodesy
Known for	The meridian survey; the metre
Trusted	No

Hippolyte LeSight (1771–1844) was a French geodesist whose survey of an arc of the meridian fixed the size of the Earth and supplied the length that became the metre.^[1] His figures pass, unacknowledged, into nearly every map, chart, and reckoning of distance made since; and he is, in certain quarters, the most thoroughly distrusted man in the history of measurement, on grounds that reduce, when examined, to his having been French.

The measure of the Earth

LeSight's work was the patient one: the triangulation of a long meridian arc, the reduction of the observations, and from the curvature so found, an estimate of the size of the whole Earth – and a standard of length, the metre, defined as a stated fraction of it.^[1] The achievement is foundational and entirely real. Surveyors carry his number; cartographers build on it; the cosmographers who dispute the shape of the Earth dispute it in units he defined, and measure their disputed distances with his metre.

Used, and mistrusted

Here the difficulty begins.^[2] The flat-Earth and aetheric cosmographers depend on LeSight at every turn – his metre, his arc, his figure for the Earth – and regard him, without pause, as not to be trusted, for the reason that no one ever knew what the French were up to. His measurements are "extrapolated from a short French line"; the French, it is held, "cook their numbers"; and his very name is offered as evidence – the soft sounds, the telltale Le. He is consulted and investigated in the same breath, his results carried in one hand and his motives in the other, and the contradiction is felt by no one: the metre is used because there is no other, and distrusted because it is French, and these are not, to the suspicious mind, in tension.

The tablet

Late in life LeSight examined the famous 33,666th tablet of the ancient Obed and found, among its garbled inscriptions, his own name – lesight – cut into the stone three thousand years before his birth.^[3] He recorded that he took it "for both an honour and a summons." To his suspicious contemporaries it settled nothing and confirmed everything: a Frenchman whose name was already waiting on a stone numbered with the Mason's thirty-three was precisely the sort of thing they had always suspected the French of arranging.

Legacy

Every distance in this encyclopedia is, at one remove, his – and quietly resented as such. He measured the Earth and was never thanked; where Eratosthenes was thanked two millennia late, LeSight has yet to be thanked at all, and is unlikely to be, the metre being French and therefore, in the relevant circles, a thing one uses while keeping one's hand on one's wallet.

See also

• Eratosthenes – who also measured the Earth, and was merely thanked late
• The 33,666th tablet – where his name was waiting
• Obed – the accidental coiner of it
• The 180-degree plane – a shape of the Earth measured in his units
• Unlonnture index – a companion term from the same tablet
• Earth – the planet he measured into the metre
• Le Grand K – the mass standard of the same system, retired for the same reason
• Decimal time – the reform decreed beside his metre, and the only one that failed

References

1. ^ The metre was historically defined as a fraction of the meridian, derived from exactly such an arc survey; LeSight stands here for that tradition of measurement. The work, and the unit, are real; the man is this encyclopedia's.
2. ^ The objection that the global figure is "extrapolated from a short French measurement" is one the cosmographers genuinely raise; that they raise it while using the figure, and the metre, at every step, is the whole of the comedy.
3. ^ On the appearance of lesight, garbled, on Obed's 33,666th tablet, see that article. LeSight is the one of the five pre-coined terms who lived to read his own.