The 17th-century Roots of the Metric System

Episode Transcript
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Speaker 1 (00:01):
Welcome to Stuff You Missed in History Class, a production
of iHeartRadio. Hello, and welcome to the podcast. I'm Holly
Frye and I'm Tracy V. Wilson. This is one of
those episodes born of personal curiosity in that way that
things will happen in your world and eventually your brain

(00:24):
will go, huh, yeah, I did that. Why is that
a thing? And one of those things we don't really
answer in this episode, but we'll talk about it in
the behind the scenes because it's a Bob's Burgers thing
where they're talking about the metric system sort of in
Tina mentions that Britain still uses miles and she goes, yeah,

(00:46):
we learned about it in school, and I was like, oh, yeah,
why is that? And then something else happened with a
friend of mine when we were traveling and we were
talking about the transition from imperial to me when we
were in in London, and so I was like, oh, yeah,
I should investigate how that'll happen and why some people

(01:08):
have some things and some don't. So we have a
little bit of that, but really what started to become
interesting to me as we as I started researching it
is that there there were a lot of people trying
to figure out how to get everybody on the same
page kind of literally in terms of how to measure things.
But there are two guys in particular that are like,

(01:28):
I have a plan, and so we're going to talk
about them. There were these two men. They worked separately
but simultaneously on the issue of standardized measurement. They're each sited,
depending on where you look, as the originator of the
idea of the metric system. This also leads to some
occasional rivalry of what country is the birth of the

(01:53):
metric system in One of these men we have actually
talked about at length on the show before, and that's
John Wilkins, because in twenty nineteen we did an episode
on his books about the moon and his ideas about
possibly traveling to it. Yeah, we're going to put that
on as a Saturday Classic, not immediately but soon. Yeah,

(02:14):
and today we're going to have a little bit of
overlap with that episode because we just want to be
able to explain without anybody having to listen to the
other episode. How Wilkins got to a point where he
had the interest, the time, the resources, and the credibility
to propose a complete overhaul of the way England was
handling units of measure. That's something we didn't talk about

(02:35):
at all in the twenty nineteen episode because we were
focused on his moonwork, which we'll mention briefly here just
because of timeline. But then we're also going to talk
about his French contemporary who proposed a similar system, and
then how it took so very long for any country
to adopt what became the metric system. Uh. And then
we will talk about the fact that even though both

(02:56):
of these men wrote about theoretical ways a universal system
of measure could be developed, no one did the work
to make that happen. As we said, it took so
very long, for more than one hundred years. So John
Wilkins was born on February fourteenth, sixteen fourteen, in the
County of Northamptonshire, England. His father, Walter, was a goldsmith

(03:19):
and his mother was Jane Dodd Wilkins. Walter Wilkins died
when John was a child, and Jane remarried. Her second
husband was Francis Pope. In this second marriage, Jane had
another son, Walter Pope, who became a writer and an astronomer.
Because John's father, Walter, had died. John's grandfather was the
family member who kind of managed his education, and after

(03:42):
some preliminary lessons at home, he went to a private
school in Oxford, although John is said to have not
found this especially stimulating. He moved on to the New
Inn Hall for kind of the equivalent of what would
be high school in our perception when he was thirteen,
and then to Maudlin Hall to earn his bachelor's degree
in sixteen thirty one, and he stayed there to gain

(04:04):
his master's degree. He got that three years later in
sixteen thirty four. He worked first as a tutor at
Oxford and then as a minister. He had a parish
in Fowsley, Northamptonshire, but realized being a vicar in a
parish was not the right fit for him. He thought
he would do better as a chaplain in a private setting,
working for the nobility, where he would have time to

(04:26):
also work on the various philosophical and scientific projects that
he was interested in. He went through a series of
these positions while writing his first book Yeah. He realized, like,
if I'm a vicar in a community parish, I will
also have to do things with the community that take
up all my days. I'd like some reading time, please.

(04:46):
So that's how that worked. I have to say that
sounds like a good gig. There might be a reason
that we have just figured out that a lot of
religious figures are the ones that were advancing science during
this period of time. That book that he worked on
was published anonymously in sixteen thirty eight. This is one
we've talked about before. It was a scientific work that

(05:07):
laid out the case that the Moon could be inhabited
and could potentially be inhabited by humans if we got there.
He wrote a second edition examining the possibility that people
could fly to the Moon, and then his next work,
which was published in sixteen forty, examined the likelihood that
Earth was indeed a planet. If that sounds weird, remember
the Moon had only been seen through a telescope a

(05:28):
little more than twenty five years before this, so scientists
were still in the early phases of working out how
the solar system was arranged and how celestial motion might work.
They had some broad strokes, but details were still a
little elusive, and so while the idea of Earth as
a planet had been in the mix, for almost one
hundred years. At the point of Wilkins writing about Earth,

(05:49):
a heliocentric solar system was not a universally accepted truth.
One of Wilkins's important contributions to the world of science
was as a founding member of the Royal Society. His
work as a private chaplain had taken him to London,
and while he was there he often met with other
scientific and philosophical thinkers of the day in weekly gatherings.

(06:12):
This group was described in the writings of John Wallace
as quote diverse worthy persons inquisitive into natural philosophy and
other parts of human learning, and particularly of what hath
been called the new philosophy or experimental philosophy. This group
is one of the precursors to the Royal Society, as
is a similar group that Wilkins gathered in Oxford after

(06:36):
his next move, because in sixteen forty eight he became
warden of Oxford's Wadham College. This is tied closely to
his political standing, as he had sided with the Oliver
Cromwell led Parliamentarians in the English Civil War, and the
parliamentarians had secured a victory in the second phase of
that conflict. In sixteen forty eight. Wilkins was instrumental in

(06:59):
growing Wanham, which gave him a great deal of notoriety,
and he simultaneously grew his political standing, and Cromwell named
him as a chancellor in sixteen fifty two. Wilkins also
married Cromwell's sister, Rabina French in sixteen fifty six. She
had previously been married to Peter French before she was widowed.
Though his parliamentarian leanings were well known, Wilkins ran Wadham

(07:22):
with an ideology of tolerance and fairly progressive values for
the time, something incidentally that Wadham continues to be known
for today. Because of this, even families with Royalist loyalties
enrolled their sons there, and a lot of those families
were or became close friends with Wilkins. Many of his
students went on to great acclaim, including Christopher Wrenn. When

(07:46):
Wilkins began having his own gatherings of intellectuals there, his
group had a lot of crossover, both in attendance and
in correspondence with the London group that we mentioned a
moment ago. In September sixteen fifty nine, Wilkins left Wadham
after Parliament appointed him the mastership of Trinity College, Cambridge,
but when the monarchy was restored with the return of

(08:09):
King Charles the Second in the spring of sixteen sixty,
Wilkins lost that mastership, although he did have a lot
of supporters, both parliamentarian and royalists, who made the case
that he really should remain in the position. His good
name among members of the court soon led to new
appointments and a rise to success during Charles the Second's reign,

(08:29):
although he was not reinstated at Trinity. But it's during
these years of turbulence that he worked on more formally
establishing the gatherings of thinkers that he had been part
of in London and Oxford into a more formalized society.
In sixteen sixty he was appointed chairman by his peers
of the new group, referred to as a quote College

(08:50):
for the promotion of physico mathematical experimental learning. The King
not only approved the society's founding, he also wanted to
be a member, and in July sixty sixty two, the
Royal Society was officially incorporated. Wilkins served as the first
secretary of the newly founded society throughout the sixteen sixties.
Wilkins was busy moving in the scientific circles of England,

(09:13):
and it sounds like having a lot of fun doing it.
John Evelyn wrote of him in his diary pretty often.
One entry from July of sixteen fifty four offers a
pretty good sketch of where Wilkins was and his life.
Quote thirteenth July sixteen fifty four. We all dined at
that most obliging and universally curious doctor Wilkins's at Wadham College.

(09:37):
He was the first who showed me the transparent apiaries
which he had built like castles and palaces, and so
ordered them one upon another as to take the honey
without destroying the bees. These were adorned with a variety
of dials, little statues, veins, et cetera. And he was
so abundantly civil, finding me pleased with them, to present

(09:59):
me with one of the hives which he had empty,
which I afterward had in my garden at Says Court,
where it continued many years, and which his Majesty came
on purpose to see and contemplate with much satisfaction. He
had also contrived a hollow statue which gave a voice
and uttered words by a long concealed pipe that went
into its mouth while one speaks through it at a

(10:22):
good distance. He had above in his lodgings and gallery
a variety of shadows, dials, perspectives, and many other artificial,
mathematical and magical curiosities. A way wiser, a thermometer, a
monstrous magnet, conic, and other sections, a balance on a
demi circle, most of them his own. Evelyn's accounts also

(10:45):
showed that Wilkins was still working as a minister quote
tenth February sixteen fifty six. I heard doctor Wilkins preach
before the Lord Mayor in Saint Paul's showing how obedience
was preferable to sacrifice. He was a most obliging person
who had married the Protector's sister, and took great pains
to preserve the universities from the ignorant, sacrilegious commanders and

(11:07):
soldiers who would fain have demolished all places and persons
that pretended to learning. Samuel Peeps also mentioned Wilkins with
some frequency, but doesn't appear to have been wowed by
him as a preacher. In February sixteen sixty four, he
wrote quote twelfth Lord's Day up and to church to
Saint Lawrence to hear doctor Wilkins, the great scholar for

(11:30):
a curiosity, I having never heard him, but was not
satisfied with him at all. The two men did appear
to become friends despite this early disinterest on Peeps's part. Yeah,
you're kind of a letdown. Coming up, we're going to
talk about Wilkins's writing about how a standardized way to
measure things might be devised, But first you will take

(11:52):
a little sponsor break. During the sixteen sixties, Wilkins worked
on a proposal to overhaul the messy way that things
were measured and install a universal approach to it. He

(12:12):
included this in a writing in which he called for
the development of a universal language that people should use
in addition to their own native language to make science,
international relations, in global trade simpler. That work, titled an
Essay Towards a Real Character and a Philosophical Language, included
a section on measures, in which he wrote, quote, the

(12:33):
several nations of the world do not more differ in
their languages than in the various kinds and proportions of
these measures. And it is not without great difficulty that
the measures observed by all those nations who traffic together
are reduced to that which is commonly known and received
by any one of them, which labor would be much
abbreviated if they were all of them fixed to and

(12:55):
one certain standard. Wilkins actually thought this new system should
be an octal numbering system that is based on eight.
We'll talk about this in the behind the scenes, but
it breaks my brain to think about it a little bit.
He also concedes, though, that nobody will likely adopt that system,
and that the decimal approach is heavily favored. He discusses

(13:16):
that using a measuring system based on the division of
degrees on the Earth would be impractical and eventually settles
on the pendulum as the best approach. He credits Christopher
Wren with coming up with the idea, and here's how
he described this quote. The most probable way for the
affecting of this is that which was first suggested by

(13:36):
doctor Christopher Wren, namely by vibration of a pendulum, time
itself being a natural measure depending upon a revolution of
the heaven or the earth, which is supposed to be
everywhere equal and uniform. If any way could be found
out to make longitude commensurate to time. This might be
the foundation of a natural standard. If you're thinking, I

(13:58):
know there are some flaws in that, we're getting to that.
Obviously there can be pendulums of differing links. Wilkins thought
that a pendulum with a half beat of one second
was the perfect unit to use, which he called a standard.
That half beat or half period is the time it
takes for the pendulum to swing from one extreme to
the other. And then he kind of describes how anyone

(14:20):
could set up their own ruler, essentially by hanging a
ball on the end of a string that has no
stretch and then carefully calibrating it so its natural swing
takes one second. He continues, quote, Let this length therefore
be called the standard. Let one tenth of it be
called a foot, one tenth of a foot, an inch,
one tenth of an inch a line, and so upward

(14:41):
ten standards should be a perch, ten perches, a furlong,
ten furlongs, a mile, ten miles, a league, etc. He
goes on to explain how the same approach could be
applied to volume. Quote, and so for measures of capacity,
the cubicle content of the standard may be called the bushel,
the tenth part of the bushel, the peck, the tenth

(15:03):
part of a peck a court, and the tenth of
that a pint, And so for as many other measures
upwards as shall be thought expedient for use. He also
included similar explanatory systems for weight and even money. But
Wilkins wasn't saying this was how things should be done.
He said, at the end of all of his proposed

(15:23):
ways to measure things, quote I mention these particulars not
out of any hope or expectation that the world will
ever make use of them, but only to show the
possibility of reducing all measures to one determined certainty. This
was the last book Wilkins published in his lifetime. There
were others, but they came out posthumously. The same year
that this book came out, he was made Bishop of Chester,

(15:46):
and he served in that role until his death four
years later in November of sixteen seventy two. In France,
another religious man with a serious interest in science also
worked on the idea of a universal approach to measurement
during the sixteen sixties. That was Gabrielle Muton. We don't
know as much about his early life as we do

(16:07):
about Wilkins. Mouton was born in Lyon, France, in sixteen eighteen.
He lived there his entire life. When he was four
years old, he joined the children's choir of Saint Paul's
Church in Leon, and you could also say he stayed
there his whole life. He remained deeply involved with Saint
Paul's and it ultimately became the place where he worked.

(16:28):
After receiving his degree in theology and taking holy orders,
he was given the title of Vaquier perpetuel at Saint Paul's,
literally the permanent Minister. He received his divinity degree in
the sixteen forties and worked as a spiritual and community
leader there for almost five decades. During his time as

(16:49):
a theology student, Gabriel had also developed a strong affinity
for mathematics and astronomy, and he studied those on his
own time, and then when his formal education ended, he
continued to work on his own projects in these areas
of interest, and it is through this work that he's
known today. In sixteen seventy, so, two years after Wilkins

(17:09):
wrote out his version of a possible unifying system of measurement,
Mouton wrote up his idea to solve the problem. Although
Wilkins thought that using the measurement of the Earth as
a basis was problematic, Muton thought it was the right solution.
He wrote a paper about it, which translates to observations
of the apparent diameter of the Sun and Moon, and

(17:31):
he shared the methods he had developed to calculate the
size of a celestial body. His estimate of the Sun's
diameter was quite accurate, and he also put forth the
idea that a fraction of the Earth's meridian should be
used as the basis of a system of measurement. But
Mouton did not abandon the pendulum. He figured out that
a pendulum that had a half beat of one second

(17:53):
at a given latitude would not work the same at
a different latitude. The length would have to be different.
That means you couldn't use that. That's because coriolis force,
which would not be named until the twentieth century after
French engineer gesbarg Corioli shifts the way a pendulum moves
as the Earth rotates. In the northern hemisphere, a pendulum
moves slightly to the right each time it swings, and

(18:15):
in the southern hemisphere slightly to the left, shifting the
length of the pendulum swing. The slight difference in the
Earth's radius as you move toward either pole also has
an effect on gravitational acceleration. So while Wilkins had an
interesting idea with his pendulum measurement, everyone would also have
to agree on the pendulum measure being taken at one

(18:35):
consistent latitude, so that doesn't really make it a universal standard.
Mudon believed that measurements of pendulums at different latitudes could
be used to calculate the Earth's meridian, and then a
fraction of that number could form the basis of a
unit of length that would be universal. This was a
degree one minute of longitude, which he proposed would be

(18:57):
called the meal. Then, like Wilkins, he gave a list
of names for the fractional divisions of that number centuria, decuria, virga, virgula, decima, sentissima,
and Milesimal units multiplied by the meal were the stadium, funiculus, virga, virgula, digitus, granum,
and punctum. So here's an interesting tidbit. We don't actually

(19:21):
know if Mouton knew about Wilkins's work or not. Wilkins
was not the first person to suggest a pendulum for
a unit of measure, although he was one of the
first to really lay out how it might be used
as a basis for a comprehensive system. But the concept
had been kicking around Europe since Galileo first wrote about
pendulums in the fifteen eighties. In sixteen fifty six, more

(19:44):
than a decade before Wilkins wrote his measuring example out,
Dutch mathematician Christian Huygens had invented a pendulum clock. So
there was a lot of discussion of pendulums in the
scientific community, and it's certain that Muton read about them,
whether he specifically read will Dilkins's work or not. And
a lot of people were trying to think of a

(20:04):
way that measurement could be unified in one system around
the globe, because it was very difficult for people from
different places to communicate concepts when they couldn't even agree
on what the numbers they might use in a paper mint,
so to kind of zoom in a little. Even within
one country, there could be variations and there still are,

(20:25):
Like in Britain, a dry gallon means a measurement of
grain and that was larger than a liquid gallon. As
the US adopted the British system, we still technically have
a dry gallon and liquid gallon. It's different measurements. So
if you said you had a gallon of a thing
and it wasn't clear if that was dry or liquid goods,

(20:46):
those could mean very different things, so easy to get confused,
and it still is mootl outlived Wilkins by quite a bit.
He died on September twenty eight, sixteen ninety four. He's
buried in the chapel at Saint Paul's, where he worshiped
and led the congregation throughout his entire life. But even
though a lot of the scientific community received his work

(21:08):
with a great deal of interest, he still did not
live long enough to see any of his ideas implemented.
In a moment, we'll talk about the many steps that
actually took for France to get a metric system set
up and how that went. First, though we will hear
from the sponsors that keep the show going. It actually

(21:35):
took a lot of time and refining amongst the European
scientific community to get Mutu's theoretical measuring ideas to a
place that was considered workable more than a century. On
the one hand, there just weren't real world measurements that
verified his theoreticals, and even the tools needed to do
so took some time to figure out, and then there

(21:56):
were just also the usual issues of international conflicts. This
slowed things down. Ultimately, France was the first country to
implement the metric system, but that transition was not instant.
By the seventeen nineties, France had a variety of problems
with its measurement of things, just like a lot of
other countries around Europe. It became such an issue that

(22:18):
in seventeen ninety one, after Statesman Charles Maurice to Telerom
began a debate about the issue, the National Assembly tasked
the Academy of Sciences with figuring out something better. And
one of the ways they sought to ensure that the
basis of their system would not have problems of variability
based on things like location or custom was that it

(22:38):
had to be based on a measurement from nature that's
a lot like what Wilkins and Mutton had written about.
It was decided that one ten millionth of one quarter
of Earth's meridian, so through the polls would be the
basis of the entire system. A different way to describe
a quarter of the meridian is to say the distance

(23:00):
from the equator to the north pole. Additionally, that calculated unit,
which was to be called a meter, would also be
used to determine a standard measure of weight using a
cubic meter of water. So a leader is one one
thousandth the weight of a cubic meter of water. Once
this whole plan had been made by the Academy of Sciences,

(23:20):
the Assembly signed off on it, and then it moved
to King Louis the sixteenth for approval, and after meeting
with a group of scientists and mathematicians, Louis gave the
measurement plan the royal seal of approval. This is actually
a strange part of Louis the sixteenth legacy. The day
after he had that meeting, he tried to leave France
as the growing tensions between the monarchy and its people

(23:43):
threatened his and his family's safety. He didn't make it
out of the country, of course, he was imprisoned, but
he still gave a directive from prison to set the
wheels in motion for a scientific survey to get an
official measurement for the meter, and it was on the
base of that directive that Jean Baptiste Josef de Lambre
and Pierre Machan set out to do just that. They

(24:06):
traveled in opposite directions from Paris along the meridian that
runs through that city. They went up to Dunkirk in
the north and down to Barcelona in the south to
form the basis for this measurement. Yeah, it's kind of
a complicated thing where they went in those directions, and
then they came back measuring the same way, and were

(24:26):
meeting up to compare all of their stuff and then
extrapolate their bigger measure. The work of de Lambre and
Mechamp took seven years. It had been planned as a
one year project. It is quite a tale in its
own rate, and if you are interested in its twists
and turns, including an error made in calculations early on
that was covered up. There is a really fun book

(24:46):
about it that is The Measure of All Things. It's
written by Ken Alder. Ultimately, Delambre and Michamp did conclude
their work with the length of the meter established as
thirty nine point three seven zero zero eight inches, and
from there various divisions of the meter were calculated, as
well as those of weights. The prefixes for multipliers of

(25:07):
the meter were from Greek so decca, hector, kilo, and miria.
The divider measures took their prefixes from Latin so desi,
senti mili. We mentioned in our episode on the French
Republican calendar that when that ultimately failed calendar system was
put into practice, it used a base ten approach to
marking the passage of the day. Each day had ten hours,

(25:29):
and each hour was one hundred minutes. Each minute was
one hundred seconds, And that was tied to some extent
to this idea of adopting the metric system. Yeah, it
was a very popular concept at the time. In seventeen
ninety nine, France declared this new system the legal standard
for measures. But just as there had been resistance to

(25:49):
a new calendar, people did not want to suddenly toss
out all the various measuring systems they had been using
up to that point. Listen, change is difficult. I read
one account that's suggested that there were actually people like
from the government going to people's homes to try to
be like, no, you got to start using the Napoleon

(26:10):
tossed the new metric system entirely in eighteen twelve, though
at that point enough people had started using it that
the probably exasperated Emperor just decided people could use whatever
they wanted. He was busy trying to invad Russia that year,
he had other stuff on his mind. Finally, in eighteen forty,
the metric system was reinstated as the official system of

(26:30):
the country. It took a long time for other countries
to get on board with metrication. Belgium, Luxembourg and the
Netherlands adopted it right behind France, but it's been a
very slow progression. Britain didn't get to it until the
nineteen seventies, although even now there are some systems that
have not changed over Today, you'll often see the statistic

(26:54):
that there are only three countries in the world that
don't officially use the metric system. There's being Liberia, mar
and the United States. That doesn't mean that it isn't
used in those countries, though. Elizabeth Benham, writing for the
National Institute of Standards and Technology in October of twenty twenty,
made the case that the US is actually using the

(27:14):
metric system all the time. Benham states that in the
write up quote, it is impossible to avoid using the
metric system. In the United States. All our measurement units,
including US customary units you're familiar with, feet, pounds, gallons, fahrenheit,
et cetera, are defined in terms of the SI, and mass, length,
and volume have been defined in metric units since eighteen

(27:37):
ninety three. The SI's influence is pervasive and even felt
if most people don't know it. I envisioned US metric
practice like a huge iceberg above the water's surface. US
customary units appear to still be in full effect in
actuality below the water surface. We find that all measurements
are dependent on the SI, linked through an unbroken chain

(28:02):
of traceable measurements. So SI in that statement, is the
shortening of another name for the metric system, the international system,
and an international system was what Wilkins and Mutaal had
been after this whole time. Yeah, incidentally, Mutal's MIA was
adopted sort of, it became the nautical mile. Oh, there's

(28:24):
so much more of the metric system. This is definitely
high level, But I really like talking about how these
two men were really onto the same concept, and to
me it's such a heady idea to go a fraction
of the meridian, like what is that? Yeah? I have
some listener mail related not at all to metrics, but
to Mary Somerville. This is from our listener Catherine, who writes, Hello,

(28:46):
Holly and Tracy. You probably had a dozen of these,
just in case not. I'm sending over a picture of
a Scottish banknote which features recent podcast subject Mary Somerville.
I've only ever got as far as wondering if she
is any relation to current Scottish government Minister Cabinet Secretary
for Social Justice Shirley and Somerville. Nothing on Google indicating
she is one. I have not gotten a dozen of

(29:09):
those two. I haven't done any research on that either,
so I don't know three banks. Catherine goes on three
banks issue notes here in Scotland, so there are a
lot of different designs to enjoy. I especially like the
one with otters. Yes, the cute water sausage animals. Now
I can know a bit of context on the Mary
Summerville ones too. They are legal to use around the
whole UK, but harder to get accepted the farther south

(29:32):
in England. You go fair enough when folks aren't familiar.
But the typical protest is that's legal tender, which is
another thing I've pondered the meaning of and not looked up.
I think they are legal to use, not illegal to refuse.
There are some weird rules I know in the US
about what you can and can't refuse regarding tender, but
I don't know them in Scotland or England. She included

(29:54):
a cat tax. This is Nissa working hard. Thanks for
the many hours of company. I listen while I work
and then re listen to favorites on road trips, I e.
Moonbeavers in the history of Margarine. Best wishes Catherine. It's
such a pretty bank note. I have to say I'm
obsessed with this because she is a Domino kitty. She's

(30:16):
black and white, and she's very pretty. I love a
black and white cat. I love all the cats. It's
pretty hard to find a cat. I don't enjoy it.
Thank you so much, Catherine. You are, like I said,
as far as I know, you're the only person that
send us a picture of that bank note, so I
am deeply appreciative because it looks very pretty. If you
would like to write to us and send us pictures,

(30:36):
of your banknotes or anything else. You can do that
at History podcast at iHeartRadio dot com. You can also
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(30:57):
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Stuff You Missed in History Class News

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Holly Frey

Tracy Wilson

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.css-14f5ked{margin:0;word-break:break-word;display:-webkit-box;-webkit-box-orient:vertical;box-orient:vertical;-webkit-line-clamp:2;overflow:hidden;}The 17th-century Roots of the Metric System