CHAPTER ONE

THE ABRAHAM DARBYS

AND

THE LITTLE IRON BRIDGE AT COALBROOKDALE

The little iron bridge across the Severn River near Coalbrookdale in Shopshire, about 25 miles northwest of Birmingham, England, may be the most historic man-made structure since the cathedrals of the Middle Ages. This cast-iron bridge, now more than two centuries old, was the first large structure ever built of metal. Its gossamer framework and circular symmetry make it beautiful as well as historic. Its span is only one hundred feet. By today's standards it is hardly enough to carry traffic over a small creek, but its significance in the 18th century was tremendous.

The story of this little iron bridge goes back to the earliest years of the 1700's and to a man named Abraham Darby. Darby is credited with being the first iron maker to successfully use coke processed from coal as the fuel in a blast furnace. This use of coke to make iron was of such importance that a modern historian of ironmaking during this period has written"...it is true to say that the industrial revolution started here."(1) By "here" he meant the "OLD FURNACE' belonging to Darby at Coalbrookdale.

Why would the successful replacement of coke for charcoal in making iron be so important that it might be the single most significant event in the Industrial Revolution? For hundreds of years wood and charcoal had been the major fuel for all industrial processes--shipbuilding, brick making, glass making, pottery, and even brewing. But a truly prodigious use of charcoal was in iron making. Charcoal not only produced the heat for the process, but also was the element (carbon) in the chemical reaction reducing the iron ore to iron. Blast furnaces were built wherever iron ore was found and woodchoppers would begin to strip the surrounding countryside of all standing timber. About one acre of woods was needed for each ton of iron produced. Iron making in an area stopped only when wood to fuel the furnaces was gone. By the beginning of the 1700's this created a serious shortage of timber in England, Scotland and Wales, as well as in countries on the European Continent. As a result, iron making had started to decline in England long before the Industrial Revolution. England became an importer of iron. The substitution of coke for charcoal was not accomplished for want of trying. Many iron makers had taken out patents with claims for success, but the end result was always the same --- poor quality iron. There is a serious question if England could have achieved her success in the Industrial Revolution without being, at the same time, a successful metalworking nation. We will never know because the Darbys and the little iron bridge at Coalbrookdale thrust the country into the lead as the world's maker of iron

IRON-MAKING AT NIGHT AT COALBROOKDALE BY PHILLIPP JAKOB LOUTHERBOURG (Wikipedia)

The first Abraham Darby came from a family of farmers. The Darby's were Quakers, a religious group that seemed to take naturally to business and industry. In his youth Abraham Darby was apprenticed to a maker of malt mills, brass equipment for brewing beer. Darby visited industries in Holland in 1704 where he saw coke being used as the fuel in a variety of industries, including brass foundries(2). Several years later he entered the brass business in Bristol, where he used coke for fuel. In 1707 he and John Thomas, another Quaker, took out a patent for manufacturing iron products. In the next year he founded the Bristol Iron Company to make cast-iron products in competition with brass.

In 1709 Darby moved his iron works up the Severn River from Bristol to Coalbrookdale where he leased an old furnace (circa 1638) that had been abandoned by the previous operators. He used coke in making cast-iron to manufacture pots and other wares of the local trade. He died in 1717, without the general iron-making industry being aware of his great technical achievement. Iron making continued at the Darby works under Mr. Ford, a son-in-law, until it passed on to Abraham Darby II about 1756 It was long believed that this second Abraham Darby, may have had more to do with the successful use of coke than had his father. It seems reasonable that the longer-range development of larger and taller blast furnaces, of greatly increased blowing power and of the efficient balance of iron ore, coke and limestone in the charge would have come gradually over a considerable time with careful experimentation on the part of the iron masters. Following Abraham Darby II, who died in 1763, the firm was again managed by a son-in-law, a Mr. William Reynolds, prior to the ascendance of Abraham Darby III.

By the 1770's the use of coke in iron making was becoming more common, though not universal. Iron masters other than the Darbys were becoming known for the quality of their products and for their astute business sense. Foremost among these outstanding iron masters was John Wilkinson, also of Coalbrookdale. Wilkinson's father, Isaac, may have been the first iron master to follow in the footsteps of the Darbys in the use if coke. John Wilkinson was the first iron master to install the new steam engine built by Watt. Wilkinson became a cast-iron crusader. He believed that cast iron literally could be used for everything. He may have developed cast-iron pipe and is reported to have supplied over forty miles of it for water mains for the city of Paris in 1788. He bolted cast iron plates together to build a boat, which he used on the Severn River to the wonderment of the local townspeople. They found it incredible that cast iron could float. Wilkinson knew the principle of Archimedes--- even his cast-iron boat would be "buoyed up" by a force equal to the water it displaced. He carried his enthusiasm for cast iron to his grave by being buried in a cast-iron coffin.

About the time the Revolutionary War was starting in the American colonies, Abraham Darby III and John Wilkinson proposed that the new bridge across the Severn at Coalbrookdale be made of cast iron. There was no precedent for using iron on such a scale and for such an important and costly a structure. The bridge was designed by a local architect by the name of Pritchard who died before the bridge was built. The design was considerably altered during construction, which took place between 1775 and 1779. Barrie Trinder, an historian of the Industrial Revolution in Shopshire has written: "Pritchard was an architect, a stonemason by training, and not an iron master, and there can be little doubt that the structure as it was finally realized was to a large extent determined by Abraham Darby III and his foundrymen."(3)

The metal was cast in the Darby Iron Works since Darby's shop was close to the construction site. In fact it is believed that the "Old Furnace" leased by Abraham Darby in 1709 was enlarged to increase its capacity for this project. Thus the greatest iron dynasty of the 18th-century England and the development of coke to replace charcoal in making high-quality cast iron brought forth one of those rare engineering accomplishments: a near perfect structure that was both useful and beautiful. No massive parts, no over-design to allow for doubt or ignorance, no excess material whatsoever. It was the marriage of a new material with a design reflecting a growing awareness of engineering possibilities. This little iron bridge is the ancestor of all present-day metal structures. Perhaps Trinder said it best when he wrote (4), "The Iron Bridge was no mere milestone in the history of civil engineering: it was the phenomenon of the age". In 1788 The Society of Arts awarded Abraham Darby III their gold medal for the magnitude and importance of the iron bridge.

THE IRON BRIDGE ACROSS THE SEVERN RIVER AT COALBROOKDALE (Peter Scholey/Robert Harding)

A CLOSER LOOK AT THE BRIDGE STRUCTURE(Wikapedia).

Technical advances came slowly two hundred years ago. It was nearly a generation before another major iron structure was built: then others rapidly followed. A second bridge of nearly twice the span of the Coalbrookdale bridge was constructed at Sunderland over the Wear River about 1795. The great Scottish engineer, Thomas Telford, incorporated cast iron bridges and aqueducts into his roads and canals. In fact, within 25 years after the construction of the little bridge, Telford completed his greatest achievement in canal building by carrying the Llangollen Canal in a cast-iron aqueduct over the River Dee in Wales for a span of 1000 feet at a height of 127 feet.

TELFORD'S CAST IRON AQUEDUCT(Wikipedia)

Cast iron continued to be used for major structures as late as 1850 when Robert Stephenson, the master railroad builder, spanned the Tyne River at Newcastle. Stephenson's bridge is still in use today carrying both railroad and highway traffic, even though the size and weight of vehicles have increased many times over in the intervening years.

The closing years of the 18th century and the opening ones of the 19th provided great opportunities for the "Iron Masters" of England. The Darbys supplied many of the cast-iron cylinders for steam engines from as early as 1723 for the Newcomen type engines and after about 1785 for the new Watt engines. They made the cast-iron beams and posts for the first fireproof textile building in 1797. Also the Darbys and their Coalbrookdale Company made the cast iron gates of the famous Crystal Palace Exhibition Hall in London in 1851. These gates are still in use today between Hyde Park and Kensington Gardens in London.

The last of the Darbys to be associated with the Coalbrookdale Company were Alfred and Abraham Darby IV who both retired in 1849 and Francis Darby, son of Abraham Darby III, who died in 1850. It was Francis Darby who supplied the artistic talent for making art castings that the company became known for in the 1840s. Thus, the Darby iron masters spanned the period in Shopshire from 1709 to 1850, almost 150 years. During most of these years the family had many partners. They seldom held complete control, but they always made significant contributions.

The iron trade declined in the Shopshire region throughout the 19th century, especially after 1850. Near the end (1871), a committee of the Iron and Steel Institute, including Henry Bessemer, visited to look for old documents and for surviving relics of Abraham Darby I. A local speaker told them that "Shopshire was somewhat in the position of a man who while conscious that his own best days were past, regarded with pride the race of giant sons which had grown up around him". (5)

Cast iron became low enough in cost to find widespread use. It was cast into such common products as post for roadway lamps and signs, church stoves, complex window frames and even tombstones (shades of John Wilkinson). It became fashionable by the mid-19th century to build the street side of public building and even private homes with cast iron for structural supports and decorative trim.

The Darbys, John Wilkinson and William Reynolds (the same Reynolds who managed the Darby Works as a son-in-law) of Coalbrookdale, along with other great "Iron Masters" such as the Crawshays of Cyfarthfa, Wales and John Roebuck of the Carron Works in the lowlands of Scotland laid the groundwork for the important metalworking segment of the coming Industrial Revolution. They and some of their descendents would continue to improve the technology and economics of basic iron making.

One of their colleagues, Henry Cort, developed the puddling process in 1784 to convert cast iron from the blast furnace into wrought iron. This puddling process was the most important development in metals for the coming 19th century. Wrought iron is free from the harmful carbon that renders cast iron brittle and weak in tension and bending. Furthermore, it can be shaped by hammering and rolling. Wrought iron was the workhorse metal for the high period of the Industrial Revolution in the 19th century. It made possible the application of power on a gigantic scale for trains, ships, and machinery.

Cast iron no longer is used in structures such as bridges and buildings and wrought iron production has ceased, completely displaced by steel. Nevertheless, our modern world of 100 story skyscrapers, the Golden Gate Bridge, 18-wheelers, Alaskan pipelines, and yes even 747's, can be traced directly to the Abraham Darbys and the "Little Iron Bridge at Coalbrookdale".

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