BLOG: When the Stones Held
My Dad was a civil engineer. He had won a trophy for his studies in geometry during high school. He was a chess champion, a superb mathematician, and pretty much excellent at everything I'm terrible at! But he instilled in me an appreciation of buildings and structure. He taught me to be amazed at the Pyramids when I went to Egypt. And he explained how the ancient world was far more sophisticated because of their building and engineering than the modern world can fathom.
As I researched in preparation for my Antonius Trilogy, I learned just how right he was. Builders of the Pyramids, Vetruvius, and so many others who remain unnamed, due to the vagueries of time and loss of historical records, were real heroes.
This week, I have a fantastic essay below written by David E. Owen. Owen's novel, WHEN THE STONES HELD is about an 18th century engineer, building a one-of-a-kind bridge in Wales. In reading this blog post, I was humbled at the intensity of Owen's research and in the plain, easy to comprehend way he has explained what an early engineer/stonemason was trying to accomplish.
For those of you who know as little about engineering and bridge-building as I do, prepare to have your eyes opened to the marvel of one bridge's construction. It's truly awe-inspiriing. So, a special welcome and gracious thanks to David E. Owen for visiting today with his research and I wish him the greatest success with his book.
Read ON, everyone!
Building an Arch That Would Stand: The Art of the Masonry Bridge
by David Owen
When we cross an old stone bridge today, it is easy to see it simply as part of the
landscape. The difficult part is imagining it before it was a bridge.
There was a river. There were two banks. There were blocks of stone, timber, ropes,
carts, tools and men. And somehow all of that had to become an arch capable of
supporting its own enormous weight.
That was the world I had to understand when I began researching When the Stones
Held, my novel about the eighteenth-century Welsh bridge builder William Edwards.
The principle behind a masonry arch is deceptively simple. Stone is immensely
strong when it is compressed. Shape individual stones into wedges and arrange
them in an arch, and the weight can be transferred through the curve towards the
supports on either side. Once complete, the stones effectively hold one another in
position.
The difficulty is getting them there.
Building Something That Cannot Yet Support Itself
An unfinished stone arch cannot stand by itself. Until the two sides meet, something
else must carry the weight.
The traditional solution was a temporary timber structure called centring. Carpenters
constructed a great wooden framework in the shape of the intended arch. The
masons could then build upon it, laying the wedge-shaped stones, known as
voussoirs, from the sides towards the crown.
This meant that building a masonry bridge involved two considerable structures.
There was the stone bridge everyone intended to keep, and beneath it the temporary
wooden structure without which the permanent bridge could not be built.
Accuracy mattered.
The stones had to be shaped and laid so that the forces would eventually pass
through the arch as intended. The abutments at either end had to withstand the
outward thrust. The centring had to support many tons of masonry without shifting
significantly while construction continued above it.
And then came the moment that fascinated me most as a novelist.
The timber had to be removed.
Until then, the centring was still helping to carry the bridge. Only when that support
was eased away would the arch take its full weight.
Today an engineer can model stresses, materials and loads with extraordinary
precision before construction begins. William Edwards had no computer, no modern
surveying equipment and no reinforced concrete hidden inside his bridge. His
knowledge came from geometry, accumulated experience, observation and an
intimate understanding of the materials with which he worked.
That makes the moment when the centring was removed particularly compelling.
However confident the builder might have been, theory was about to encounter
reality.
The River Was Part of the Problem
A bridge does more than carry people over water. It must survive what the water does
beneath it.
Many traditional bridges crossed rivers using several arches supported on piers. Smaller
arches were easier to construct than one enormous span, but placing piers in a river created
problems of its own.
Water pressed against them. Their foundations could be undermined. During floods,
branches, trees and other debris could become trapped against the structure, increasing the
force upon it.
For William Edwards, this was no theoretical danger.
He was commissioned in the eighteenth century to build a bridge across the River Taff at
Pontypridd, then known as Newbridge. His early attempt was destroyed by floodwater.
His eventual answer was audacious: cross the river in a single enormous leap.
With no intermediate piers standing in the Taff, the river could pass beneath the bridge
unobstructed. But the solution created a new engineering challenge. A single stone arch of
such a size brought immense weight and thrust.
Edwards had exchanged one problem for another.
Making Stone Lighter
The bridge for which Edwards became famous spans approximately 140 feet, around 43
metres. For an eighteenth-century masonry bridge, that was an exceptional distance, and
Edwards had already discovered how unforgiving such a structure could be.
An earlier great arch appears to have been completed before failing. Contemporary and later
accounts attempted to explain what had happened. The Gentleman's Magazine reported the
loss of an arch across the Taff measuring 144 feet, while a later discussion of the bridge
suggested that the problem lay in the distribution of weight: there was either too much upon
the haunches of the arch or too little upon its crown.
Edwards' answer can still be seen today.
Above each end of the great arch are three circular openings, six in all, decreasing in size as
they rise towards the roadway. Their purpose was structural rather than decorative. By
replacing solid masonry with open space, Edwards reduced the enormous weight pressing
down upon the haunches of the main arch.
Yet those holes also had to be built.
Each is effectively a small masonry arch passing through the body of the bridge. During
construction, the stones forming its curved upper surface could not support themselves until
the arch was complete. They therefore required their own temporary support, most probably
timber centring on a much smaller scale than that used beneath the enormous main span.
It creates an extraordinary picture of the bridge while it was being constructed. Beneath
everything stood the great timber centring supporting the principal arch. Above that, as the
spandrels rose, further temporary supports were required while the six smaller arches were
formed. The finished bridge might appear to be a single stone structure, but its construction
involved a succession of temporary structures that disappeared once their work was done.
And there may be more inside the bridge than we can see.
Historical accounts have suggested that Edwards created additional hidden voids within the
masonry, presumably as another means of reducing weight without weakening the external
form of the bridge. Whether those accounts are correct has remained uncertain because
discovering what lies inside a structure nearly three centuries old presents an obvious
problem: investigating it physically could damage the very bridge engineers are trying to
understand.
In 2026, that question led to a remarkable meeting of eighteenth-century engineering and
twenty-first-century science. Rhondda Cynon Taf Council commissioned specialists to
examine Edwards' bridge using muon tomography, a technique that measures naturally
occurring cosmic particles passing through a structure. Similar technology has been used to
investigate the internal structure of the Egyptian pyramids.
The detectors can identify variations in density inside the bridge without drilling into the
masonry. Engineers hope this will establish whether the hidden spaces described in historical
records really exist and reveal more about how Edwards constructed his great arch.
Almost 270 years after William Edwards finished the bridge, therefore, we still do not
completely understand everything he did inside it.
That seems particularly appropriate. The six great circular openings have become one of the
bridge's most recognisable features. What began as an ingenious attempt to solve a problem
of weight became part of its architectural identity. Now modern technology may reveal that
Edwards' solution was even more sophisticated than its outward appearance suggests.
The Men Behind the Bridge
Researching the construction also changed the way I thought about the people involved.
We naturally attach one name to a famous structure. We speak of William Edwards' bridge.
Yet a bridge of this kind depended upon many skills.
Quarrymen had to extract the stone. Masons had to shape it. Carpenters had to construct the
centring. Labourers moved materials using methods that demanded considerable physical
effort. Carts and horses brought supplies to the site. Men worked above moving water
without modern safety equipment.
And all of this had to happen with sufficient precision that, when the temporary support
finally disappeared, thousands of individual pieces behaved as a single structure.
That became important when writing When the Stones Held. I did not want the bridge simply
to appear in the background while the novel concentrated upon its famous builder. I wanted
the reader to feel something of the labour involved: the stone, timber, mud, cold, noise and
uncertainty.
Historical research can tell a novelist what people did. The more interesting question is often
what it might have felt like to do it.
When the Stones Held
William Edwards' bridge at Pontypridd still stands.
Modern traffic no longer crosses it, and another bridge was eventually constructed alongside
it, but the great stone arch remains. Nearly three centuries after the problems that confronted
its builder, you can still see the solution he arrived at.
Perhaps that longevity makes old masonry bridges seem inevitable. They have survived for so
long that we forget there was once a morning when each existed only as a plan, a collection
of materials and an act of confidence.
For me, that was where the history became a story.
A builder could calculate, measure and draw upon everything experience had taught him. His
masons could shape the stones. His carpenters could construct the centring. Everyone could
do his work correctly.
But eventually the temporary supports had to be taken away.
Then there was only the arch.
And the stones had to hold.
Images:
Newbridge, Unknown author. This image is in the public domain.
New Bridge, or Pont-Y-Prydd, Glamorganshire (engraved). Author, Neale, John Preston
1780-1847 & Woolnoth, William fl. 1785-1836 engraver. This image is in the public domain.
ALL ABOUT THE BOOK
When the Stones Held is a historical novel inspired by the remarkable true story of William Edwards, the self-taught Welsh stonemason who built one of the great bridges of the eighteenth century.
Growing up in rural South Wales, William lives in a world of hard physical labour, dangerous rivers and limited opportunity. From an early age, he develops an instinctive understanding of stone, balance and the possibilities hidden within the landscape around him.
As the coal trade begins to transform the valleys and the need for safer routes grows, William accepts an extraordinary challenge: to build a bridge across the River Taff at Pontypridd. He is twenty-seven years old and has never built a bridge before.
What follows will test far more than his skill as a stonemason. Flood destroys his first bridge. Later attempts bring new failures and new problems to solve. With his reputation, livelihood and family affected by every decision he makes, William must decide how much he is prepared to risk for something no one can promise will succeed.
Set against a South Wales beginning to experience profound change, When the Stones Held is a story of ambition, family, community and resilience, and of an apparently ordinary man whose determination would leave a legacy that survives more than two and a half centuries later.
ALL ABOUT DAVID
After decades spent teaching around the world—from the UK to the Caribbean, Africa, and the Middle East—I came to writing fiction later in life. I started with fantasy before finding my voice in fast-paced, real-world spy thrillers. My stories are grounded in current issues like corruption, gender bias, and power, but always emphasise pace, surprise, and character-driven tension.
I’ve visited over 80 countries, worked as a radio host in Abu Dhabi, directed Shakespeare for African audiences in the bush, and even survived a flash flood in Mali and an armed hold-up. I was arrested for drug-smuggling in Nigeria but was eventually released when I refused to pay off the police captain, and I was boat-wrecked alone on a desert island in the Arabian Sea (but no tree) and rescued through a police search. Now retired from teaching, I split my time between writing, photography, and trying to get fit (thanks to a stubborn rowing machine). My latest novel, Hate Machine, tackles misogyny and gender radicalisation — not typical thriller territory, but I like a challenge.
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~This book is also available on Kindle Unlimited.~
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