Original subtitles

[narrator] What is this strange Roman device

that has baffled archaeologists for centuries?

[Dr. Abigail Graham] The Romans were meticulous administrators,

but we don't have any written accounts about these objects.

[narrator] Is a machine powered by blood-sucking leeches

the original weather app?

[Goodman] It's impossible. Mad ideas didn't seem so mad.

[narrator] Do these ancient scrolls

mark the locations of buried treasure?

By the time they did the complete tally,

it was something like 200 tons of gold and silver,

something worth billions of dollars today.

[narrator] These are the most remarkable and mysterious objects on Earth.

Hidden away in museums, laboratories and storage units.

Now, new research and technology can get under their skin

like never before.

We can rebuild them, pull them apart

and zoom-in to reveal the unbelievable,

the ancient and the truly bizarre.

These are the world's strangest things.

[narrator] This strange bronze artifact is one of the great mysteries

of the Roman Empire because we have no idea what it is.

We don't have any written accounts about these objects.

When we don't have a clear place to put fantastic objects like these,

we end up in a vast mire of speculation.

[narrator] As nothing is known about it,

archaeologists simply call it a Roman dodecahedron,

after its 12 sides.

It might be considered

nothing more than a curiosity if there was only one.

But incredibly, 116 of these dodecahedrons have been found.

No two are exactly alike.

They vary in size from one and a half inches to four and a half inches.

[Dr. Andrew Steele] A Roman dodecahedron takes a 12-sided shape

and has little spheres to each of the corners.

And that means you can stand it up nice and easily.

And also on the faces, there are holes,

and these holes are circles,

but they're different sizes on every one of those faces.

[Dr. Graham] When the bronze was polished,

it would have sheen or sparkle in the sunset

It would catch your eye.

[narrator] There are no numbers, no writing,

no other marks to explain what it is for.

Now a theory has emerged.

We may have been getting the purpose

of the dodecahedrons wrong for centuries.

So what is it really for?

Where does it come from?

What is this strange object?

One thing we know for certain, Romans were obsessed with gambling.

[Dr. Graham] It's a cuboid.

It could be used for games,

and the Romans loved their dice games.

Everyone played them.

And in the same way

that we see people on the tube playing Candy Crush

or a game on their telephone.

When you excavate buildings in Rome,

often major temples are riddled with game boards

where people just sat and played dice.

We have tons of archaeological evidence.

In Pompeii,

there's a famous wall painting that shows men fighting over a dice game.

Caesar, before he crossed the Rubicon,

is famous for saying, "Alea iacta est!"

"The die is cast."

"I'm throwing in my fate."

[narrator] Romans used dice in endless combinations

of shape and size to suit a multitude of games.

So, is it a dice?

Unfortunately, there are flaws to this theory.

You pick these things up and you try to throw them,

well, because they don't have a flat face,

They don't bounce correctly.

They don't land right and they don't have numbers on them.

[narrator] Magnifying it, it reveals that every hole is a different size,

so the weight of each side is different, which makes it a loaded dice.

So, the primary function of a die

isn't really adhered to by these objects, so that's a bit of a problem.

[narrator] Another suggestion is that it's a candleholder.

[Dr. Graham] I understand where the idea came from,

which is that, some traces of wax

have been found on the inside of one of these.

[narrator] But this theory also has serious flaws.

It would be a candleholder that didn't really work very well

in protecting your hands from getting burned or holding a very large candle.

If you've ever used a candlestick,

there's a grip and a long whim around the top of it

to stop the wax dripping onto your hand.

[narrator] It's even been suggested that it's a child's toy.

[Dr. Graham] The idea that you'd give your child

a small metal toy to play with,

my son would have had it in his mouth, in its ear.

He'd have probably tried to get it up his nose.

[narrator] So not a dice, not a candle holder, and definitely not a toy.

Is there a clue in the pattern of where these

mysterious artifacts have been found?

Every Roman dodecahedron discovered

is in the north and northwest regions of the empire,

where the weather is colder and generally less pleasant.

None are found in the sunny or southern regions,

which has led to a new theory.

So, one of the pervading theories

is that these were then used for knitting

and perhaps to knit gloves.

So to test this theory, someone has actually

printed out a 3D scan of one of these

and used it to knit a five-fingered glove.

I really like the idea

that these were for knitting gloves.

If it's not the sort of thing that

smart Archaeologists were scratching their heads over,

chatting to astronomers and mathematicians for decades,

but you show it to someone who knows how to knit.

And they go, "It's obviously for making gloves."

[narrator] But not everyone is convinced.

[Dr. Graham] I'm not saying that it's not possible

that it was used as a knitting device.

But gloves are kind of commodity item.

There are pre-existing instruments for weaving.

The idea that it was used generally to knit a pair of gloves,

it doesn't fit with how expensive these objects were to make and produce.

[narrator] The problem is that nearly every dodecahedron

is made of bronze.

And bronze doesn't come cheap.

It's made out of the same materials that money is made out of.

[narrator] The Roman technique for casting hollow bronze items

is still used today.

It's time consuming and difficult.

You start off with a clay core.

You coat this with wax.

In the wax, you carve the intricate details,

whatever shapes you want to make out of bronze.

[narrator] You then cover the whole thing again in clay, and bake it.

The wax melts out.

So, once you've done that, you've got a mold

that has got the negative space

of what you want to make out of bronze.

Then you get your bronze.

You melt it up to over a thousand degrees, so it's nice and runny.

It's like red hot metal now,

and you pour it into the molds,

bits in it sparks, and then you wait for that to cool down.

[narrator] This technique is far too expensive for everyday objects.

It doesn't, from a financial, economic point

or from a trade point, make a lot of sense

to take all the time and effort

to make one of these incredibly intricate, beautiful objects

for something that is really an everyday-use item.

[narrator] So what could justify the expense and effort

that goes into making one of these bizarre things?

After centuries of mystery, is there finally an answer?

[narrator] This Roman dodecahedron

has baffled archaeologists for centuries

and has led to a series of competing theories,

each of which has as many flaws as answers.

Now there is an idea that seems to fit perfectly.

One thing that is incredible about Rome is,

wherever you go in northern Europe

and actually across most of the Roman Empire,

and you look at a Roman military camp

and the way that it is laid out,

it is very similar across the Roman Empire.

They had an exact plan, and to put out those exact plans,

they needed to have a means of taking basic measurements.

How do you plan a road?

How do you set out your milestones?

What marks the Roman empire for me

is that they measured distances

and not only measured them but marked them out.

They had milestones along their routes

to record those distances, and they were accurate.

[narrator] The dodecahedrons might be one of the secrets to this accuracy.

It's all to do with the different sizes of the opposing holes.

[Dr. Steele] You look through it, because the holes are different sizes,

at a certain distance away,

at which the circles will appear to be the same size,

and that's always going to be the same fixed distance

away from your eyes.

[narrator] All you need then is an object of unknown size,

preferably one that can be carried high up off the ground.

[Dr. Steele] So, for example, you might get a Roman centurion

carrying it standing.

Then he could march off into the distance.

Place that standard down, when that standard

is exactly the same size as your two circles,

you know that he is a certain distance away.

[narrator] This theory also explains why all the holes are different sizes.

So just by rotating it,

you could measure a variety of different distances.

[Dr. Graham] If you're holding it,

you need to be able to manipulate it.

It explains the nodules.

It explains the different size holes.

It would even be a way of explaining the drawings outside of the holes

that are used to kind of line them up.

And it's also something that functionally fits with the needs of the Roman army.

[narrator] And the most essential need of all for the Roman army

is winning wars.

[Dr. Graham] They had to know when people were in range.

Not only for things like arrows, but they also had catapults.

And it's not just about having this technology.

It's about knowing when exactly is the right time to employ it.

So this sort of thing would have great functionality

in setting out roads, in setting up base camp,

but also in terms of actual fighting, in terms of knowing

when the enemy was in range, knowing when to fire their catapults.

[narrator] So, is that case closed?

Is it definitely a measuring device rather than a dice

or a glove making tool or a candle holder?

It certainly sounds convincing, but the truth is,

unless we find a written account or fresh archaeological evidence,

we may never know for sure. But it's fun guessing.

[narrator] In 1952, hidden in a cave in Israel,

archaeologists find some of the most controversial

and baffling objects ever uncovered.

Ancient strips of rolled up metal.

The copper scrolls.

There's nothing like them in the world.

They are 12 inches long

and two inches wide, corroded and brittle.

But stamped into them are traces of an ancient text

that has sparked a billion-dollar treasure hunt

and a passionate argument that is still raging today.

Is it a treasure map?

Isn't it a treasure map?

Now, new research may finally hold answers

to one of the greatest archaeological mysteries of the twentieth century.

Who made these one-of-a-kind scrolls?

Where do they come from?

Is there really hidden treasure in the desert?

Or is it just the dream of an enthusiastic archaeologist?

What are the copper scrolls?

1947, the northwest bank of the Dead Sea.

A young goat herd

was scrabbling around the rocky wilderness

near the village of Qumran, about 15 miles east of Jerusalem.

He entered a cave and discovered some jars

that seemed to have broken pieces of parchment and papyrus in them.

[narrator] These 2,000-year-old documents,

are some of the most important archaeological finds of modern times...

The Dead Sea scrolls.

Their discovery is a game changer for archeologists.

They include some of the oldest known fragments of the Hebrew Bible.

When scholars found these well-preserved scrolls,

they were really thrilled.

They had now some of the earliest biblical sources,

as well as community sources that would have described the region,

the kinds of practices that were going on

during this time of really tumultuous Jewish history.

For biblical archaeologist, this was the find

of a lifetime of the century, perhaps of a millennium.

[Dr. Altaweel] This gives us back a sense effectively, of a period

not far away from when the Bible,

or parts of the Bible, were written.

So this allowed scholars to really have a connection to a period

when a lot of the religious works in religious communities

that arose to create these works, uh, were developing.

[narrator] Just five years later, a team of archaeologists

are examining a nearby cave when they discover the copper scrolls.

And it's immediately obvious to them that these are something totally different.

[Dr. Graham] One of the most unusual things about the copper scroll

is in its name that it's a scroll,

but something that isn't made from parchment,

that is made from copper...

material that's far more valuable and also difficult to inscribe.

So this is something that distinguishes it

as probably an important document,

possibly a sacred one.

[narrator] What could be so important that it justifies

the effort of writing it on copper?

A few words visible on the outer layer

of the tightly-rolled scrolls catch the experts' eyes.

Those words include digging cubits, a measure of size, and gold.

Some archaeologists jumped to the very obvious conclusion.

We say not to judge a book by its cover, but this is every archaeologist's dream.

"I found a treasure map."

[narrator] The only way to be certain the copper scrolls

are a treasure map is to unroll them.

But that is very risky.

[Dr. Ploszajski] The problem with copper is that

if you leave it lying around for thousands of years,

it oxidizes.

And this oxidation makes it very brittle.

The copper is extremely thin, so if you were going to try and unroll it,

what would happen is the brittle copper would basically just snap.

[narrator] But one expert doesn't give up.

[Prof. MacDonald] In 1955,

John Allegro, a British archaeologist,

convinces the authorities in Jerusalem

to allow him to cut open the scroll

so that it could be translated properly.

[narrator] The problem is,

no machine capable of such specialized and precise work exists.

So Allegro asks Prof. Wright Baker at Manchester University

to invent one.

On the first of October 1955, using a machine bolted together

from a modified circular saw and a dentist's suction brush,

Wright Baker begins to cut open the two priceless 2,000-year-old scrolls.

One slip could be catastrophic.

Over the next three and a half months,

Wright Baker's machine breaks the scrolls down into 23 segments.

For the first time in 2,000 years,

their secrets are revealed.

So, is it a treasure map?

The references to hidden gold visible on the outside

turn out to be the tip of the iceberg.

[Altaweel] When they begin to put the scroll together

and translate the different parts,

they realize it's not really just a treasure map.

Rather, it sounds like a series of treasure maps.

[Prof. MacDonald] What was discovered is that, in fact, they were all originally part

of one single continuous scroll, eight feet long.

This scroll had 64 individual entries

for buried hoards of items ranging from coinage,

to valuable metal items, to various ritual holy objects.

The sheer amount of wealth that is represented in the document

was unimaginable.

[Altaweel] By the time they did the complete tally,

it was something like 200 tons of gold and silver,

something worth billions of dollars today.

So, a really mind boggling amount was buried in deserts.

[narrator] But something doesn't add up.

That amount of wealth just seems too large.

How can anyone 2,000 years ago gathered together

such an obscene amount of wealth or keep it secret?

So, is there a billion-dollar fortune buried in the desert?

[narrator] Some archaeologists believe that these unique copper scrolls

are the key to a hidden fortune

buried somewhere in the vast Judean desert.

But others struggle to accept this interpretation.

The problem is that the scholarship also connected this list

to the ASEAN community,

who were relatively austere mystic sect at the edge of the Jewish world.

[Altaweel] They're kind of poor people

on the desert dedicated to religious life.

Yet the amounts of gold and silver were thought to be

billions of dollars in worth of gold and silver.

So, you're looking at these guys who look like basically pauper monks

but yet they have the wealth of Elon Musk or something like that.

So it's not something you would expect.

[narrator] The treasure story splits the academic world in two.

John Allegro, the British archaeologist who sliced the scrolls open,

is convinced, the treasure is real.

The opposing camp is led by one of the team

that discovered the copper scrolls,

Biblical scholar and Catholic priest Jozef Milik.

Jozef Milik begins to look at this,

and he does the calculations and numbers,

and he realizes these numbers are far too much.

There's something wrong here.

[narrator] Milik doesn't just think

that this was too much wealth for the Essenes.

The numbers are so vast, he's convinced it's too much treasure

for the whole of the Qumran region 2,000 years ago.

John Allegro accepts that the initial estimates may be too high,

but he has an explanation for that.

It's a miscalculation.

The unit used in the text is 'talents', which can vary over time,

and sometimes it has different meanings to different communities.

So, which weight of talent are we looking at?

If we're looking at a relatively lighter weight,

then the value of these hoards could be significantly altered.

[Altaweel] So it's possible that the calculation used

to determine the amounts of modern day tons from a talent is incorrect.

Potentially, the translation of the units or the conversion of the units,

was quite different.

The community may have used a very different standard effectively for talent,

and so the amounts may have been far less.

[narrator] Allegro argues that valuing the treasure

in the millions rather than billions makes it historically credible.

But that still doesn't answer one crucial question.

Where does all this wealth come from in the first place?

15 miles from Qumran is Jerusalem's Wailing Wall,

a sacred site of Jewish prayer and pilgrimage.

It's the last remaining relic of a mighty structure

known as the Herodian Second Jewish Temple.

The Second Temple was the place of worship for Jews,

and when I mean 'the', is that it was practically the only place of worship,

and it would have had all the treasures and gold

of all of the Mainline Jewish believers.

So it would have been a very wealthy place.

Allegro believes this could explain the treasure.

John Allegro's argument was based upon the notion

that these were the treasures of the Second Temple,

stashed away for safekeeping during the time of the Jewish Civil War.

This is where coin hoards come from, things that are put away,

hopefully to be reclaimed in better days.

[narrator] Milik counters that the treasure never exists in the first place

and believes Allegro is misinterpreting the scrolls.

To resolve this, they need a complete translation of the text.

Officially, this is Milik's job.

But to Allegro's frustration, Milik delays publishing his translation.

With good reason.

[Prof. MacDonald] If he says that it's fake,

then he could be accused of a cover up.

If he says it's real, then there would be a descent of treasure hunters

into the region, trying to find these lost gold and other items.

So, naturally he delayed

and procrastinated as long as possible.

So, John Allegro goes ahead and publishes the list and caught media attention.

The result is a great deal of recrimination and bitterness between the two scholars.

[narrator] In 1962, to prove his theory,

Allegro leads an expedition in search of the lost treasure.

The search for lost treasures is a phenomenon which is back into humanity

over the centuries.

And leads many a person to ruin.

[narrator] Allegro doesn't find even a single nugget of gold,

and despite decades of searching by treasure hunters,

these incredible riches remain elusive.

So, is it simply a fable?

Now, new research may finally answer

the secrets of the copper scrolls,

and it's a total shock.

[narrator] New research now suggests a radical alternative explanation

for the 2,000-year-old copper scrolls.

In 2015, a new theory emerged.

Could the copper scroll have been merely an accountability list

of items which had been donated to the temple over time

and never actually all existed at any one given moment?

[Altaweel] There are other Jewish ancient Hebrew text

that effectively talk about a made up version of the treasure

that didn't actually exist, but rather a kind of

idealized number or value of a treasure that could have existed in the past.

[narrator] This idea may be connected to the ancient Greeks.

This is the Lindos Chronicle, an inventory of items

in a temple to Athena, written 200 years

before the copper scrolls.

[Dr. Graham] Towards the start of the text,

they actually say all these things

that we've been cataloguing weren't actually there.

They may have existed at one point,

but the idea was that I would give these items to Athena, the goddess of Athens,

as supplication, as a dedication to her,

even if I don't actually have those items.

To show the dedication that you would have to her.

So, it's a way to show how much you love the God, effectively.

[narrator] And there's a connection between lists like this

and the enigmatic copper scrolls.

The scroll is written in ancient Hebrew,

but a closer look reveals Greek letters at the end of some of the entries.

Greek inventories use similar notations, known as letter labels.

It's a simple cataloging system, like numbering an index card.

Is that what the Greek letters on the copper scrolls mean?

So, how do you present it to your God?

You have to organize it in some way.

And so using Greek letters might be the way that was done.

So, like the Lindos Chronicle, the scroll could be a record of wealth

for display in the temple, which may explain why it's made of metal.

[Prof. MacDonald] Why was it in copper?

Perhaps it was a matter of display.

Perhaps this was, rather than a scroll,

more of a plaque detailing on the wall of the temple,

all of the great items, all of the treasure,

which had been bestowed upon it over the years.

[narrator] There's just one problem.

Unlike the Lindos Chronicle, the copper scrolls

identify locations for the treasure.

Whether all this wealth is real or historic,

why would they advertise this for any treasure hunters to see?

The answer may lie in the final lines of the scroll.

Ironically, the last entry on the final sheet of the scroll

is a specifications about where you can find the list.

Probably another copper scroll which can decode the locations

for the items in the larger list.

So, effectively, not only the treasure is missing,

but the very means to locate them remains missing as well.

[narrator] But as long as the potential for real treasure exists,

treasure hunters will keep coming back to Qumran, to seek their fortune.

[narrator] Whitby, in the north of England.

Tucked away in the local museum is a replica of one of the strangest

and most bizarre inventions in history.

Standing over three feet tall, it looks like a model fairground carousel.

But it's not.

This is a Victorian cutting-edge scientific instrument.

It's an intricate contraption of polished mahogany, glass,

silver and brass, and it's designed to change the world.

There has never been anything like it before or since.

[narrator] This is the tempest prognosticator built to crack one of the greatest

and most challenging problems of the Victorian age...

the weather.

Using the power...

of leeches.

Twelve tiny leeches living in jars of water

that are trained to ring a bell.

[Prof. Tim Denison] In the presence of extreme weather,

the leeches would rise up

and kind of signal that inclement weather was coming to you.

[narrator] 150 years ago,

this is a serious idea.

People treat it seriously.

Who comes up with this bizarre device?

How's it supposed to work and why does anyone believe

a leech can tell them it's going to rain?

[thunder rumbling]

[narrator] The tempest prognosticator is an invention

designed to predict bad weather

using the power of leeches.

[bell dinging]

It sounds crazy now, but in the Victorian era,

anything seems possible.

[bell dinging]

Mad ideas didn't seem so mad.

[narrator] By the 1850s,

Victorians were making huge strides in technology and science.

New inventions like rubber tires,

photography,

and bicycles

are revolutionizing the way people live, work, and travel.

That's a very mid-era.

It's a time of enormous innovation,

of enormous social and physical and industrial and economic change.

Things are happening so fast, it would take your breath away.

[narrator] Business and trade are booming,

and that's where the weather comes in.

[thunder rumbling]

Increasingly, as trade became more important,

as there was more traffic on the seas, it became ever more important

to be able to predict storms and so forth.

[Goodman] There is more to be lost

when you've got huge fleets at sea

than there was when it was just a few boats in shore.

As the world became more connected and trade grew,

weather had more of an impact.

[narrator] Unfortunately, weather forecasting is stuck in the Dark ages.

There have always been all these sort of

folklore signs of the weather.

Things like, "Red sky at night, shepherd's delight."

"Red sky in the morning, shepherd's warning."

[narrator] But folklore doesn't sit comfortably

with the new Victorian age of science.

From electricity to magnetism to evolution,

nature is giving up its secrets.

One after another,

all sorts of mysteries are being cracked.

Could reliably predicting the weather be science's next, great conquest?

By the Victorian times, it began to look possible to bring weather

within the sort of remit of things that scientists could

measure and understand and predict.

But this was a science, really at its birth, and it's very early stages

and no one was really sure what would work and what wouldn't.

[narrator] Enter gentleman scientist, George Merryweather.

Merryweather was a doctor of Whitby, and it seems he had all kinds of side interests.

He was the curator of the local museum.

[narrator] Another of his side interests is invention.

In 1850, he produces his most famous

and groundbreaking creation, the leech-powered tempest prognosticator.

The core of his invention is a glass bottle

containing a few inches of water and a leech.

Hidden away at the top of each bottle

is a system of levers and chains connected to a bell.

[Dr. Ball] There was a little mechanism made from very fine boat

that would be triggered by the leech coming past, and that would ring a bell.

[narrator] Of course there's always a risk that one leech might misbehave.

But Merryweather has a plan for that.

His machine uses 12 of them.

[Prof. Denison] As opposed to relying on just one leech

and its wisdom on the weather report,

there was actually a ring of these jars

so that you could take more of a majority vote

on the activities of the leeches.

The more bells that rang, then the stronger your prediction was.

[narrator] It all sounds terribly rational, except for one thing.

Why does Merryweather believe leeches can predict the weather?

Animals often appear in the folklore of weather prediction.

There's a long history of looking at animal behavior

to try to anticipate changes in the weather.

[Goodman] Cows lying down in fields is supposed to be an indicator

that rain is on its way.

There are many of these across all cultures all over the world.

[narrator] In Germany, frogs are the go-to weather predictors.

Every German thinks

that you can predict the weather by putting a frog in a jar

with a little ladder in it, mostly made of wood,

and then depending on where the frog sits, you know

if it's going to rain or if it's going to be sunny.

[narrator] Merryweather goes for leeches.

An animal that holds a unique fascination to Victorians.

He claims that leeches can sense a change in the weather

and will rise up towards the surface of water

when rain is coming.

The leech looks like a really primitive thing, just kind of a slug.

But actually, it's an amazingly sophisticated creature.

[Dr. Benecke] They're worms. They're not slugs or snails.

They're beautifully colored.

They can have orange-green color pattern.

[narrator] But the principal attraction of leeches is their macabre dietary habits.

Leeches are very much like a worm vampires.

[Dr. Ball] It likes to drink blood

and in order to do that, it has two suckers,

so one sticks on to the host.

The other one is lined with teeth,

hundreds of teeth,

so they bite.

And as the leech sucks blood,

it gives out two chemicals.

One is, uh, kind of anesthetic

and the other one is an anti-coagulant,

a chemical that stops the blood from clotting,

so it can continue to drink.

Once it's gorged itself,

in this way, the leech can survive for up to a year without feeding again.

[narrator] This ability to draw blood is important to Victorians

because many of them believe human health

depends on maintaining balance between the four humors.

Black bile, yellow bile, phlegm and blood.

Most attention was given to blood

because either you had too much blood

or you had bad blood,

and in both cases, the medical leech could help.

[narrator] Medical leeches are wildly popular.

There were people whose profession was leech gathering literally, usually women.

Just rolling your skirts, right up and walking in the sorts of places

where leeches live, so that they would attach to your legs.

In fact, they were so much used,

that we pretty much fished them out of existence.

[narrator] According to Merryweather, inspiration for his prognosticator

comes from a poem written by vaccine pioneer, physician

and all-round science superstar, Edward Jenner.

So, the poem is called 'Signs of Rain' and it includes the lines,

"The leech disturbed is newly risen,

quite to the summit of his prison."

[narrator] And as a Victorian doctor,

Merryweather is probably quite keen on leeches already.

But is Merryweather right?

Can leeches really be trained to predict the weather?

Or is this a great Victorian scam?

[narrator] In 1850, George Merryweather invents a machine

that he claims can predict the weather

and change the world using the power of leeches.

But is this a giant leap in weather forecasting?

Or a con to steal from the gullible?

In the end, it all comes down to one question.

Can a leech really predict the weather?

[thunder rumbling]

Merryweather claims that leeches rise up when rain is coming,

and that might not be as crazy as it sounds

because bad weather is usually associated with a drop in air pressure.

[Dr. Benecke] One possible reason why leeches

may detect air pressure in the surrounding

is that they relate to the oxygen

because they need to breathe inside of the water.

[narrator] Leeches get oxygen directly through their skin,

from the water surrounding them.

They're very, very sensitive

to the concentration of oxygen in the water

and that will change if there's a change in atmospheric pressure.

[narrator] When air pressure drops, there's less oxygen in the water,

so the leeches rise closer to the surface, where oxygen levels are higher.

It's for them just a matter of survival, to get into an area

where there's enough oxygen or to sense

if there's enough oxygen already

and then they can dive deeper.

So that was the kind of mechanical principle behind the device.

[narrator] It seems Merryweather may be onto something.

The idea of Dr. Merryweather was not completely crazy at all.

It was a very nice experiment, and maybe there's some truth in it.

[narrator] But if his tempest prognosticator actually works,

why don't we see leech barometers everywhere?

What goes wrong with his brilliant plan?

Well, it certainly isn't a lack of self-belief.

He gave a lovely talk to the Whitby Literary

and Philosophical Society.

Went on for three hours, apparently,

about how successful it had been,

during which he compared himself to Galileo.

[narrator] But is the prognosticator really that good?

[Goodman] London Illustrated News, for example,

carried a story about his successful prediction

of a major storm, fifty-one and a half hours before it happened.

It's a fairly generous margin of error, isn't it?

Mmm.

[narrator] In 1851, Merryweather takes his revolutionary invention

to the prestigious Great Exhibition in London.

All the great scientists and inventors and manufacturers were present.

It was the sensation of the age.

And there he was with his leeches, in the middle of it.

That is just the most extraordinary piece of publicity.

Unfortunately, Merryweather doesn't need

public admiration to succeed, he needs government funding.

He said that the whole of the government should install them

all the way up and down the coast

for the benefit of sailors and merchant men right across the country.

But unlike the leeches, the government doesn't bite.

[Dr. Ball] The prognosticator didn't take off,

and it's probably no surprise that it didn't.

It would have been, for one thing, an expensive thing

to produce and to maintain,

you know, leeches would keep dying.

It wouldn't have been a terribly reliable instrument.

Had it come a hundred years earlier,

it would have been perfectly in keeping with the ideas of the time.

But actually it came at a time when an instrument like this

were starting to look like a device from another era.

By the early to mid-19th century,

scientific instruments weren't meant to look like,

you know, an aquarium with little swimming creatures in it.

[narrator] Stuck between a superstitious past

and a scientific future,

Merryweather's tempest prognosticator is simply mowed down by better inventions.

[Goodman] It's the telegraph that makes a big difference

because you can suddenly get very, very quick results

from weather stations posted all the way around.

So you can start mapping what the conditions are in one place or other.

And with those maps,

you can start to make more informed predictions

rather than just relying on the leeches.

[narrator] All that remains today of Merryweather's radical invention

is a replica that sits in the museum, where he was once curator.

Albeit lacking its blood-sucking stars.