Geology Canals: The Making of a Nation

This is the story of how canals changed and shaped our modern world.

Carrying huge volumes of goods and fuel,

they were a stimulus to Britain's great Industrial Revolution.

But they also gave us much, much more

and their legacy lives on today in surprising ways.

My name's Liz McIvor

and I've spent my life studying and talking about history.

And now I think it's time for us to take a different look

at our inland waterways.

Back in the late 1700s,

carving up our landscape with canals

brought to light fresh discoveries about the earth below.

The new waterways gave us clues

into the mysteries of our planet's creation,

decades before Darwin's theories took hold.

So how did this happen?

How did canal building give us a deeper understanding of the Earth

and help create the new science of geology?

Just off London's Piccadilly,

behind the doorway of the Geological Society

is a very special and very important document...

..one which had a profound effect on our economic growth,

our scientific knowledge and our understanding of our planet.

And amazingly it's all the work of just one man.

This map had its origin

some 100 or so miles to the west of here in Somerset.

And to understand how it was created,

and why it's so significant,

we need to return to a time when canals were being carved

through the British landscape.

This is the Kennet and Avon, 87 miles long

and one of the jewels of Britain's canal network.

Getting this canal built was a seriously tough challenge

and it was partly down to the fact that geological knowledge

was so limited at the time.

The canal was given the go-ahead

during the period of frenzied building in the 1790s

known as Canal Mania.

By linking the Kennet navigation at Newbury with the Avon at Bath,

it would open up a route between London and Bristol.

Horse-drawn barges would be able to get between the cities

in just ten days,

potentially halving the transport costs by road.

The man hired to plot the route

and oversee construction of the new canal

was a rising star of civil engineering,

the Scotsman John Rennie.

However, he only had limited experience of canal building.

Construction work got under way in October 1794

when the first sod was cut at Bradford on Avon,

six miles to the east of Bath.

In time, the wharves here would handle the canal's main cargoes -

coal, grain and Bath stone.

The stretch of canal from Bradford on Avon to Bath

provides a fantastic location for pleasure boaters today.

But for John Rennie and his construction teams in the 1790s,

the local landscape proved a major headache.

Geologist Dr Janet Sumner

understands all about the treacherous lie of the land

in this part of the world.

The rocks in this area consist of limestone,

which was laid down in shallow tropical seas,

sandstone and layers of shale and mud.

Now the sandstone and the limestone are really hard,

but permeable rocks,

which wouldn't be a problem but for the layers of mud.

And what happens is one particular layer that they call fuller's earth,

which is a type of clay,

when the water reached the fuller's earth layer,

it couldn't get through, it was impermeable.

So it waterlogged the clay and it turned it into something

with the consistency of, like, tomato ketchup,

which meant that the overlying layers of sandstone and limestone

simply used it as a lubricant

and just slid down into the cutting

in a series of huge landslides.

What kind of damage are we talking about?

Well, in terms of scale, you know,

there's an estimate the equivalent of an area of seven football pitches

came sliding down the side into the canal cuts.

And that meant that on this stretch,

parts of the canal had to be repeatedly drained

and then shored up with planks.

The damage caused by the area's unstable geology

had big cost implications for the canal.

In 1800, Rennie reported that the landslips and other expenses

would add more than £270,000 to the bill.

With the science of geology still very much in its infancy,

early canal engineers like Rennie really were flying blind.

The basic problem that they had, Liz,

was they didn't have a geological map.

They had no idea about the different types of rocks

and how the rocks were lying.

And they really needed a map, but they hadn't got one.

All they'd got was information from things like boreholes,

which, in some cases, were miles apart.

So they knew nothing about the geology in between.

So the canal building crews

frequently encountered problems like the landslips,

natural springs, you know,

hitting hard rock that needed blasting,

having to dig tunnels that they thought, perhaps, would have been through earth

and then finding out they were chipping through solid rock.

So there were lots of problems like that that, you know,

all added time and expense to the bill.

-Bye.

-See you.

In spite of the challenges of the landscape,

Rennie and his teams of navvies forged on

and the Kennet and Avon began to take shape.

But more geological problems lay in wait.

To the west of Bradford,

Rennie constructed an impressive aqueduct at Avoncliff.

But it was blighted by poor construction materials.

John Rennie wanted to build the aqueduct in brick,

but the canal company overruled him and insisted on Bath stone.

They wanted local quarry owners to feel obliged to use the canal

to transport their goods.

But Rennie later regretted not putting his foot down.

Bath stone looks lovely, but it becomes easily frost-damaged

if not properly treated after quarrying.

As soon as the aqueduct was completed in 1801,

its central arch started sagging

and not surprisingly the whole structure has had to be repaired

many times over the years,

with bricks helping to sure up the damaged stone.

All these problems started taking their toll

and Rennie's canal dream threatened to turn into a nightmare.

But was his luck about to change for the better?

The truth of the matter was that the early canal builders

had very little clue about what they would encounter

when digging the trenches and tunnels.

A lot was left to chance.

Sometimes it would be slips and leaks,

but at other times they'd get lucky

and a fluke of geology would lend a helping hand.

And that's exactly what happened here at Caen Hill,

just outside the important trading centre of Devizes.

For the canal to climb the hill,

Rennie planned a series of 29 locks

and the dramatic central section of these

is one of the steepest flights on the whole canal network.

The reason that the locks are here

is because here you're climbing up the greensand,

up to the level of Salisbury Plain

and then the chalklands beyond.

And that's why there's such a steep flight.

Because of Caen Hill's steepness,

there wasn't space to use the normal arrangements of water chambers

between the locks.

So Rennie had to build unusually large side ponds

to replenish the water in each lock after use.

Unlike on the Bradford stretch,

this time fortune favoured the bold

and the canal builders had a stroke of good geological luck.

They were building the canal

and halfway up on the right-hand side they found clay,

gault clay, which is absolutely fantastic for brickmaking.

They'd hit a real problem with the canal

because lots of the locks were built of stone.

But that was suffering very badly from frost.

So they switched to bricks,

they established a brickworks just up there on the right-hand side.

And it was a major undertaking,

because not only were they using bricks in the flight of locks that you can see,

but also, 15 miles to the east,

they were building a tunnel called the Bruce Tunnel.

The landowner, the Earl of Aylesbury, he was happy for the canal to go through,

but he didn't want to be able to see it, so they had to build a tunnel

and they used over two million bricks in its construction.

It's absolutely incredible.

And it's an incredibly expensive way

-to hide a piece of engineering, isn't it?

-Absolutely.

-It was very much a case of not in my backyard, wasn't it?

-Absolutely. Nothing changes!

How long were the brickworks open for?

It was actually open into the 1960s

and there were still people around who worked there.

Of course, it's left its legacy throughout Devizes

with the handmade bricks that are still in many buildings in the town today.

The clay bricks were a big help in getting the canal up Caen Hill

and then under the Earl of Aylesbury's estate.

But Rennie encountered another problem further to the east

at Crofton, the Kennet and Avon's highest point.

There was no natural water supply to feed the summit of the canal

and it looked as if another expensive tunnel would be required.

But, instead, Rennie decided to use a huge pump

to keep the canal topped up.

We're going through limestone here, quite different to Caen Hill.

He had a geological challenge here -

how to get water to the top level where the rock is porous

and there was no natural supply up there.

And behind us over here is the pumping station,

where the oldest beam engine in the world,

the Boulton and Watt beam engine,

draws water up in this gigantic piston.

Each draw draws one tonne of water each time it rotates.

And that lifts water just under 50 foot up

to the highest point in the canal.

The steam-powered pump could keep the summit topped up,

but it still needed to be fed by a water supply at its base.

Once again, though, Rennie struck lucky,

this time by finding some springs nearby.

The canal didn't supply enough water for what he needed on its own,

because you've got to keep the canal in water, as well as taking water out of it.

So he then built a reservoir

and the springs fed the reservoir

and that provided sufficient backup volume of water

to keep the whole system working.

The Crofton Pumping Station was completed in 1809,

allowing the Kennet and Avon Canal to open for business the following year.

Rennie may have found solutions to all the engineering challenges the landscape had posed,

but the Kennet and Avon had still taken 16 years to complete

at a final cost of almost £1 million,

more than four times its original estimate.

But even though geology presented canal builders with major stumbling blocks,

it's worth remembering that some canals were only ever built

because of the local geology and the minerals to be found within the landscape.

100 miles to the north of Bath,

the Dudley Canal Tunnel in the West Midlands Black Country

is a labyrinth of over three miles of underground passageways.

They were carved out in the 1770s

to transport limestone which was being mined

to feed the new blast furnaces of the Industrial Revolution.

The canal linked the mines to the wider national waterways network.

Limestone was a really useful rock.

It was used as a flux for smelting iron,

which made the iron a lot purer.

It was used for agricultural reasons - they used to spread it on fields.

It was also turned into quicklime

and put into things like lime mortar, which created a waterproof mortar

that they could use in building canals, in fact.

There were lots of uses for limestone,

which made it one of the key ingredients, really,

of the Industrial Revolution.

Exploiting the limestone rock seams

may have been the whole purpose of the Dudley Canal.

But, as with many other canals of the era,

patchy geological knowledge left construction teams

literally stumbling in the dark.

The construction of the tunnel was long and laborious,

a very difficult job.

It involved digging out the rock with hand tools, pickaxes, things like that.

They constructed the tunnel by sinking construction shafts down from the surface

and then when they got to the bottom,

went out in two directions with miners going each way.

And then they met up, hopefully, some times better than others.

There's a few kinks in the tunnel where they didn't quite get it right.

And, of course, they were digging through completely foreign geology.

They had no idea what they were going to encounter.

As well as the limestone which was what they were looking for,

there are various volcanic rocks down under here,

mud, shales, all sorts of things

that meant that the terrain for them underground was very variable

and they could go from a very soft rock one minute

to a very hard, difficult rock the next.

'Right, now the tunnel we're going into is the second longest...'

Despite these geological challenges,

the canal tunnel became a big success once it was built.

In 1853 alone,

more than 41,000 boats carried limestone

through these tunnels from the caves.

At its height, these mines would have been absolutely packed with people,

miners at the rock faces digging away the limestone,

others loading the boats.

You were talking about ten boats an hour running through the tunnel,

so it would have been really busy,

sort of like the motorway of its time.

'Good morning. Look to the left and we have...'

The Dudley Canal Tunnel may have been a triumph,

but other canals were nearly ruined by unexpected geological problems.

It took eight years and three attempts

to complete the Blisworth Tunnel in Northamptonshire.

Test boreholes failed to detect a dip in the strata

that created an underground reservoir, causing serious flooding.

And navvies on the Harecastle Tunnel in Staffordshire

spent nine long years inching slowly through everything

from hard granite and millstone grit

to treacherous quicksand.

The fact that the early canal engineers

had such a basic grasp of geology was a big drawback.

But one canal man was about to unlock the secrets of the rocks beneath our feet.

Secrets which would, in time,

transform our entire understanding of the planet.

William Smith was the son of an Oxfordshire village blacksmith,

who taught himself surveying as a teenager.

He may have come from humble beginnings,

with limited formal education,

but he had a real knack for reading the landscape.

In 1793, whilst still in his early '20s,

he was hired by the Kennet and Avon's engineer, John Rennie,

to work as the surveyor for a new waterway

linking the main canal to a fresh coalfield in Somerset.

This is the Dundas Aqueduct.

And it's over there at the Dundas Basin

where the Somersetshire Coal Canal joins the Kennet and Avon,

particularly important because coal made up the lion's share

of the Kennet and Avon's traffic.

The Coal Canal has been long abandoned

and parts have been redeveloped and filled in.

Much of the course of the canal can still be traced, though,

and this is the route that William Smith devised back in 1794.

Professor Hugh Torrens is one of the world's leading experts on Smith's life

and first explored the landscape around Bath

as an undergraduate geologist in the 1950s.

Is this the type of thing that William Smith would have used to survey

-the Somersetshire Coal Canal?

-Yes. A theodolite.

It's a horizontometer trying to measure exact horizontality.

This is a later model of the sort of thing that was standard fare,

beautifully made, beautifully adjustable,

fantastic piece of equipment.

And, of course, the crucial thing about canals

with this wonderful series of locks we're going through

is that you can't make water run uphill or downhill.

You have to have it absolutely horizontal,

though it was a very interesting early experiment for Smith.

He was a land surveyor and I think was very good at, basically,

the lie of the land.

They plotted the entire topography of this beautiful part of the world,

most of it would have been on foot,

just walking, walking,

measuring, measuring, surveying, surveying,

with an assistant to check the other end was at horizontal...

measurement, you need somebody to hold a board up or a site up.

And, I think, the fact that these locks are built so beautifully

is a proof of their achievement.

The excavation of the Coal Canal from 1795

gave Smith an opportunity to test theories about rock strata

that he'd been developing while looking at coal seams.

By cutting open a long slice of the Somerset countryside,

he would be able to see exactly how layers of rock were lying underneath the ground.

He realised that there was an order of the strata that the rocks were in.

This is a clay unit we're in here, above it's a limestone,

and so you can put them in an order or a sequence.

And when he was asked by people what he'd discovered

and trying to get across the complexity of geology, a new science,

he used the analogy of bread and butter.

He used to get a pile of bread, slice it up,

then put them in layers and tip them over and say,

"This is what the rock strata are like and it's the same with geology."

And in his ordering of strata,

he actually alphabetised 22 rocks in the Bath area.

The top one was the chalk, the bottom one was the coal.

Where would we be indexing books or knowledge without an alphabet?

Knowing where letter A is, and how letter L relates to it?

For the first time in English history,

and probably other countries' history,

it was the first time the rocks had been ordered.

It's really atmospheric, isn't it,

to be able to walk through this old canal

and look at the weathering and the damage to the stonework?

Yes, one forgets how intense the building of the thing was.

You have the remains of the lock gates here.

These big oak doors and the pins, wrought iron pins to prove it.

And this is...210 years since it was opened in 1805,

so it's an incredible achievement.

As well as showing Smith how the rock layers were ordered,

building the Coal Canal gave him an opportunity to gather fossil specimens,

which he realised were the key to identifying exactly which strata rocks were part of.

The important thing about the rocks are - these are Bath Oolite, Great Oolite -

these rocks have fossils in them and, of course,

he was collecting fossils all the time he was building the canal.

And as you go up and down the rock strata,

you see some are rich in fossils, some are not rich in fossils.

But it means as soon as you find a fossil,

you can place it in your sequential order

and identify the stratum that you've reached.

The fossils that Smith unearthed while the Coal Canal was being dug

can still be seen at the Natural History Museum in London.

The fossils are kept in the order of strata

in which William Smith kept them

and displayed them in his home in the Strand.

He would invite people to come and see them.

He would even order other people's collections

because people had been collecting fossils for a long time,

but they didn't realise their significance.

He would put them in the natural order in which they occurred and say,

"Well, these ones are younger and these ones are older

"and this is how you should arrange them,

"because this is how they'll be useful."

Smith was a highly practical man

and the main application of his discoveries about strata and their fossils

was to predict the location of mineral wealth under the ground.

He was able to advise landowners

what the likelihood of finding coal on their land was.

People had wasted huge amounts of money thinking that they would be close to coal,

but William Smith could identify that this was the Oxford Clay,

for example, and they had no chance of finding coal on their land.

Crucially, if Smith hadn't been working as a canal surveyor,

he wouldn't have had the opportunity to properly test

and develop his theories of strata.

There's a lot of guesswork in geology.

When you actually have a cutting like they did for the canal,

you have the evidence in front of you...

The different strata,

their lithology and their fossils are there before your eyes.

You might think, well,

"I wonder if this layer of rock is outcropping over there."

But until you have the cutting, you don't know for sure.

And he had a beautiful cutting all along the length of the Somerset Coal Canal.

Smith's ground-breaking table of the rock strata around Bath

and their fossils was written down in 1799,

giving birth to the area of geology known as stratigraphy.

His discoveries are commemorated in Jerry Ortman's

stone column sculpture,

located near the ruins of the Coal Canal.

It features the same types of rocks that Smith first sequenced

over 200 years ago.

So, Hugh, what was it about the West Country landscape

that was particularly important for Smith's discoverers?

I think the first point is that Bath was a social centre.

If you wanted to come to find a mistress, take drugs, alcohol,

relax, you know, all the features of a modern holiday,

Bath was the social scene.

Which meant that if you had a discovery,

it was a good place to try and publicise it.

Bath is a wonderful place to start geology

because you can see, as you go round,

that the top is very nicely horizontal,

but the valleys are deeply incised.

So just wandering around you can see

that there's going to be a possibility of seeing things above and below.

And this ordering of the strata around Bath, 1799,

is a really rather crucial document.

And he said, "People say that I have produced the birth of a new science.

"If I have, I'd like to claim that Bath was its cradle,"

which is a rather nice way of saying that if it hadn't been a Bath,

he wouldn't have been able to do what was done, cos it wouldn't have been possible.

You have to come to a place like this to see the rocks staring you literally in the face.

Smith's discoveries earned the nickname of Strata Smith

and he spent many years in the early 19th century

continuing to study rock layers and their fossils,

while working all over Britain as a mineral surveyor and drainage engineer.

In 1815, he put all his findings together

and produced something of colossal importance -

the world's very first national geological map,

now celebrating its 200th birthday.

It took him 15 years on his own,

tramping all over the British Isles,

to create a picture,

not just of the pastures and the meadows and the mountains,

but the hidden underneath,

the subterranean marvels of the complexity of England and Wales.

The thing about this map which makes it so extraordinary is that,

from looking at that,

you can predict where things are...underneath.

Previously, if you were mining coal,

you only did so where it appeared at the ground.

Smith was able to say, from looking at the dip of the coal

and where it was likely to be underground,

that, you could say, at this point,

under Sheffield, say,

"I predict that 4,500 feet below me will be coal."

And so they dug a hole and indeed coal was found.

And so the whole British mining industry

was created on the basis of geological maps like this.

So whenever any mineral resource is found anywhere in the world,

underground,

be it oil or be it uranium

or be it platinum,

we owe an enormous debt to this map and this man,

because, more than anything,

this man enabled us to predict where the treasures of the world will be.

Smith's work also had a big influence on later thinkers,

including Charles Darwin.

He began this map in 1800 effectively,

when the common belief was that the Earth was only 6,000 years old,

but Smith said, "This isn't possible.

"I mean, these creatures that I'm finding in the walls of the canals that I'm digging

"are evidence that the world is hugely older than that."

And that the variation within, let's say,

a particular type of brachiopod or a particular type of ammonite

was such that it triggered in Darwin,

what, 50 years later when he was doing his work,

that variation that led to natural selection

which led to his book in 1859, The Origin Of The Species.

That, essentially, Darwin's theories, and discoveries

were rooted in what Smith discovered.

Smith's 1850 map was an extraordinary feat for a single individual,

but he endured some rocky patches in his personal life.

Poor budgeting and bad business decisions

left his finances in a precarious state.

And when the sales of his map were damaged by plagiarised rivals,

he was pushed into financial ruin.

He lost his house and ended up in a debtors' prison.

Gradually, though, his achievements began to gain more official recognition.

The Geological Society, who initially turned their noses up at this interloper,

born with limited education and no family connections,

awarded Smith an honorary medal in 1831.

Eventually, he was able to retire to Yorkshire on a government pension.

He died in 1839.

Not for nothing is William Smith called the father

of not just English geology, but the father of world geology.

I think he's a remarkable, remarkable figure,

and a terrible tragedy, I think, that he's so unsung.

He should be more famous than Brunel.

Brunel just built ships. Give this guy a break!

And perhaps one day he will be.

The discoverers of men like Smith certainly gave a big boost

to the youthful science of geology.

And throughout the 19th century, there was a growing interest

from specialists and the British public in rocks and fossils.

The Dudley Canal and its limestone mines

became one of the nation's most geologically significant sites.

The rocks here are 420 million years old.

They're from the Silurian period.

They formed on a shallow seabed.

That means that the rocks that we've got are absolutely full of fossils.

There are thousands of different species here.

There's a particular type of trilobite that's even known as the Dudley Bug,

because it's found so much around here,

that it's sort of become synonymous with the area.

By the mid-19th century, the canal tunnel

had gained an international reputation for its geology.

Because what they found in here was so interesting and so unique,

it became a very interesting place for geologists to come and study.

Amongst the mining that was still going on,

you'd get, sort of, pleasure cruises almost,

of interested scientists, philosophers, engineers

who would come and look at the marvel that was underground here.

The massive caverns that had been taken out

almost became a bit of a tourist attraction

for the scientists who were interested in this new science of geology.

Geological forces produce the mineral riches

that drove much of the activity during the Industrial Revolution.

And it was no accident that the science of geology

took great strides forward at the same time that canal men

like John Rennie and William Smith

were grappling with geological challenges.

It's amazing to think that the canal age didn't just shape the visible landscape around us,

it helped us to gain a deeper understanding

of what lies beneath our feet

and a great debt is owed to canal pioneers like William Smith.