Christopher Wren’s vision for the rebuilding of London after the Great Fire of 1666 was an unashamed product of its era, a rational grand plan based on modern scientific principles that would sweep away the fetid tangle of medieval lanes that had enabled the fire to cause such devastation. But the proposed city layout was only ever realized in small part. The vistas that Wren imagined stretching from Ludgate in the west to Aldgate and the Tower in the east, and the great piazzas with their octagonally radiating streets, never materialized–such grandiose Parisian-influenced designs stank too highly of a royal absolutism unbearable so soon after the Restoration of the monarchy. At the heart of the plan, St Paul’s Cathedral was rebuilt to Wren’s design, and serves now as a token of the ideal city that the architect saw in his mind’s eye, one that might justly have laid claim to be a modern-day Rome.
Wren studied the world’s greatest domed buildings, taking inspiration from Italy as well as Byzantine and Islamic architecture, including works such as the Hagia Sophia basilica in Constantinople, in order to devise a means of raising the largest dome that he could. Greatest of all was the concrete dome of the Pantheon in Rome, whose bronze covering was looted in 1625 by Pope Urban VIII for more pressing projects. For the weather-tight covering of London’s new cathedral, Wren concluded in favour of pure copper, which could be beaten thinner than other metals to create a lightweight roof that needed fewer supporting columns and would therefore allow a maximum quantity of light to percolate through the vast interior.
For Wren, copper had a visual and symbolic advantage as well as structural benefits. Over time, the metal would acquire a pale green patina that would make the dome the most conspicuous feature of the recreated city. Among the stone towers and spires of other churches, St Paul’s would stand out as the beacon of a new age of science. However, the architect’s preference for copper met with opposition in Parliament, as had his city plan before. Daniel Defoe, who once personally supplied Wren with building materials from his Tilbury brickworks, describes in A Tour through England and Wales how the discussion proceeded in true English fashion along resolutely practical lines: in response to those who thought ‘the copper covering and the stone lanthorn’ too heavy for the massive columns below, Wren insisted that his structure could support not only the roof but ‘seven thousand ton weight laid upon it more than was proposed’. As for himself, Defoe admired the ‘unashamedly continental (and High Church) design’ of Wren’s dome that may well have been the real bone of contention.
Wren also wanted to see copper embellishment of the Monument, the commemorative Doric pillar that he and the scientist Robert Hooke designed for the spot near St Paul’s where the Great Fire had started. Apparently oblivious of the irony, the architect proposed to top the monument off with ‘A Ball of Copper, 9 foot Diameter…by reason of the good appearance at distance, and because one may goe up into it; & upon occasion use it for fireworkes.’ But copper once again proved too revolutionary. In the end, the chosen design was based on an earlier idea favoured by the king of a ‘large Ball of metall gilt’.
The dome of St Paul’s was finally built with a sheath of grey lead, requiring much rethinking on Wren’s part as to how the metal sheets would be attached and how their greater weight would be supported. The fact that the lead roof weighed in, by some estimates, at 600 tons heavier gives the lie to the practical argument made against Wren’s preferred copper. Wren may have got his calculations right, but he seems on this occasion to have made a fatal misjudgment of English character. Three hundred years later, it is impossible to imagine this familiar landmark capped either in the metallic red of new copper or the green that would have gradually taken its place as the acid from the city’s fires rained down upon it. The lead umbrella seems so right in a country characterized by grey skies that we seldom think of what might have been.
Copper did eventually find its way on to the dome of St Paul’s in a small way. In 1769, Benjamin Franklin, famous for his proposal to fly a kite in a thunderstorm in order to demonstrate that lightning is electrically generated, visited Britain and personally oversaw the installation of lightning conductors on the building. These were of the kind that he advocated generally for buildings and ships, based on a long rod or bar of iron. Three years later, the cathedral was struck by lightning, and the iron was observed to glow red hot as it struggled to transmit the charge to earth, and the great cathedral was once again threatened with destruction by fire. After this, Franklin’s lightning conductor was replaced with a more expensive copper one that would conduct electricity more efficiently and pose less of a fire hazard.
Copper possesses a unique portfolio of properties, identified and exploited at different periods in its long history. Between them, they have ensured that the element has never slipped from its prime position since it began to be worked by man more than 6,000 years ago. The most immediately striking of these is of course its colour. It is the only red metal. This gave copper a special status in relation to gold, the only other coloured metal. In the New World, European explorers such as Cabot in the north and Cortés in the south found the metal used for jewellery and devotional purposes. The Florentine navigator Giovanni da Verrazzano believed copper was ‘esteemed more than gold’ by the natives. The contrast of colour between the pure red metal and its watery blue and green salts was widely felt to be significant too. This embodiment of opposites was regarded as symbolic in cultures as diverse as the Aztecs and the Dogon of Mali, for whom the accretion of green corrosion on the brown metal symbolized the return of vegetation after rain.
The first of copper’s useful properties to be exploited was its malleability. It was soft enough to be hammered and beaten into useful artefacts yet hard enough that these items would be serviceable. The ancient Egyptians used copper to make swords and helmets and even drain pipes. Being abundant as well as malleable, copper was more practical for coins than gold and silver, but sometimes raised objections from the people among whom it was circulated because of the obvious disparity between its face value and its actual worth. Henry VIII came to be known as Old Coppernose because he introduced so much copper into the silver coin of the realm that raised parts, such as the king’s nose, would turn red as they wore down. Later innovations meant that copper could be machine-rolled into thin sheets, producing the now familiar roofing material used for the domes of European cathedrals and, in due course, the new capitol buildings of North America.
The metal’s ready conduction of both heat and electricity were the next properties to be recognized. The American patriot Paul Revere achieved fame with his copper-bottomed cooking pots and pans at the beginning of the nineteenth century. At the same time, scientists investigating electricity found that copper would carry an electric current better than any other material apart from silver. Alessandro Volta made his first electric pile from layers of zinc and silver, but thereafter most batteries used copper.
But it is one final property, its ductility, that has given copper its greatest role in transforming our world. It is the fact that copper can not only be beaten into a sheet but also drawn into a wire, a wire furthermore that conducts electricity, that led to the creation of what can fairly be described as the first worldwide web.
The cabling of the world relied on a number of key breakthroughs made in a relatively short space of time–batteries that could deliver a steady current; galvanometers that could detect an electrical signal and show it by the deflection of a needle; copper refined to sufficiently high purity to conduct electricity efficiently; and the discovery of the insulating properties of gutta-percha, a resinous rubber-like substance obtained from Malayan sapodilla trees.
The first primitive electric telegraph line was built in the 1790s by Francisco Salva and was capable of transmitting sparks from Madrid to Aranjuez fifty kilometres away. Salva proposed a separate wire for each letter of the alphabet with the arriving spark briefly illuminating letters in turn in order to spell out messages. (He apparently also considered connecting a per
son to each wire and having them shout out the letter when they received an electric shock.) Many equally eccentric schemes were essayed in the years that followed, spurred on by the obvious need for a more effective means of communication than the visual methods of flags and lights used by relays of signalmen during the Napoleonic Wars. But efforts were held back by a poor basic understanding of electrical phenomena. It was not until 1831, when Michael Faraday first wound copper wire round an iron ring to demonstrate electromagnetic induction, that the relationship between various kinds of electricity and conducting matter was better understood.
Charles Wheatstone and William Fothergill Cooke demonstrated a more practical telegraph in 1837 when they built a two-kilometre connection along the railway between Euston and Chalk Farm in London, itself then newly laid. A similar trial connection established on the Great Western Railway between Paddington and West Drayton two years later was extended to Slough in 1843. This telegraph caught the public imagination soon after its installation when John Tawell, having murdered a woman in the town, boarded a London-bound train thinking to make his escape. He failed to allow for quick-witted station staff who telegraphed ahead. The police arrested him when he duly disembarked at Paddington.
In 1838, meanwhile, the American inventor Samuel Morse was in England seeking a patent for his own telegraph system. Wheatstone used his connections to ensure that his competitor’s application was rejected, and Morse had to content himself with a seat in Westminster Abbey, where he witnessed the coronation of Queen Victoria before returning to the United States to obtain a patent there for the coded telegraphic method that still bears his name.
Progress was rapid from these modest beginnings as the inventors set themselves the target of bridging successively wider chasms. The greatest challenges were the same as they would be for powered flight fifty years later: first the English Channel, and then the Atlantic Ocean. Undersea cables posed far greater challenges than land lines, which could simply be buried or carried overhead on poles. The wire had to be prefabricated in long lengths and wound on to rolls so that it could be spooled out at sea from specially adapted ships. In 1850, Jacob and John Watkins Brett successfully laid a gutta-percha-insulated copper cable between Dover and Calais, but the connection broke after a day. According to one story, the fisherman who dredged up the severed cable saw the gleaming metal at its core and thought he had struck gold. A cable of four independently insulated wires, protected by layers of hemp and tar and strengthened with iron wire, that was laid the following year proved more durable. In the following decade, England was joined to Ireland, Denmark to Sweden, and Italy to Africa via Corsica. Newfoundland was linked to Nova Scotia across the Cabot Strait and thence overland to New Brunswick, Maine and the rest of North America. All that remained now in order to complete the cable connection of Europe and America was to make the link from Ireland to Newfoundland across nearly 2,000 miles of the Atlantic Ocean.
The technical requirements for this far longer and deeper undersea connection were colossal. There was no possibility of boosting the signal at intermediate points along the cable, as there was with cables on land, so the copper conductor had to function as a single length. This made it critical that the engineers minimized signal losses due to resistance in the wire and the effects of immersion in seawater, itself a highly conductive medium. The Scottish physicist William Thomson, later Lord Kelvin, who was appointed as a scientific consultant to the Atlantic Telegraph Company, delighted in a problem that allowed him to deploy his mastery of the new theories of electromagnetism for a practical end. He wrote to his friend Hermann von Helmholtz:
It is the most beautiful subject possible for mathematical analysis. No unsatisfactory approximations are required; and every practical detail, such as imperfect insulation, resistance in the exciting and receiving instruments, differences between the insulating power of gutta-percha and the coating of tow and pitch round it…gives a new problem with some interesting mathematical peculiarity.
Thomson advocated the use of a thick copper wire, running small currents through it which could be picked up with sensitive detectors, but he was outmanoeuvred by company men who favoured the cheaper option of pushing stronger signals through narrower-gauge wire.
The first attempt to make the crossing was set for the summer of 1857, the same year that the world’s largest copper-domed roof was completed over the Reading Room at the British Museum. In August, the massive HMS Agamemnon and the United States frigate Niagara accompanied by a flotilla of support vessels set sail from Valentia on the west coast of Ireland carrying 1,200 two-mile lengths of copper wire, pre-joined into eight 300-mile lengths. The cable weighed about a ton per nautical mile, most of which was accounted for by the outer strengthening of steel wires and insulation; the copper made up only 107 pounds per mile of the overall weight in wire no thicker than a pencil lead.
As the final plans were laid for the voyage, Thomson made a crucial further discovery that the purity of the copper greatly affected its conductivity. Practically his last action before boarding ship was to read a paper to the Royal Society, ‘On the Electrical Conductivity of Commercial Copper of Various Kinds’, in which he revealed his important new findings. Nobody had given this matter any consideration. Despite his scientific misgivings, Thomson dutifully sailed aboard the Agamemnon in his capacity as a director of the Atlantic Telegraph Company, while Samuel Morse battled with seasickness and a leg injury aboard the Niagara.
It might never have worked properly in any case, but only 400 miles out from Valentia, the cable broke, and the task was given up for the winter. The following summer, two more attempts were made to complete the job using the same ships and picking up the same cable. The first was defeated by unseasonal gales. The second attempt seemed successful, but celebrations proved premature when the connection was lost after less than a month. Recriminations were followed by an inquest, which showed that the cable had been fatally damaged by attempts to boost the signal strength through the application of higher voltages than those for which it had been designed–exactly the mishap that William Thomson had feared.
Anglo-American relations deteriorated during the American Civil War to the extent that President Lincoln preferred to make overtures to Tsar Alexander II, suggesting a cable from Alaska to Siberia and through Russia to the cities of Europe, rather than persist with the Atlantic project. However, a permanent transatlantic cable was finally laid in 1866 by Brunel’s steamship Great Eastern. A correspondent from The Times likened her to ‘an elephant stretching a cobweb’. In addition, a cable abandoned the previous year was also finished, providing a spare line and reassurance to sorely tried shareholders in the telegraphic enterprise that this time the connection really would last. The design of these cables had been modified along the lines that Thomson had previously proposed, using three times the amount of copper in seven wires–365 tons in all–with every length tested in advance for purity and conduction.
After the cable went operational, one of the engineers performed a simple test on the line at Valentia. He cabled to ask that the two lines be electrically connected at the Newfoundland end, and proceeded to make a little electrolytic cell using a piece of zinc and a splash of acid in a thimble. The zinc was then connected to one copper end of the cable while the other copper end was dipped in the acid. The single volt generated by this makeshift battery was enough to drive a current 3,700 miles across the ocean and back.
Further cables across the Atlantic and elsewhere were swift to follow, backed by many national governments, while Britain sought to link all of its dominions. In 1901, at the end of Queen Victoria’s imperial reign, the Cable Steamship Britannia laid parts of a cable across the Pacific Ocean from Australia and New Zealand via Norfolk Island, Fiji and the remote Fanning Island to Vancouver–completing the union of the pink nations on the world map by pink copper.
The world today is cocooned in copper wire and, notwithstanding the advent of optical fibres and satellites and wi-fi, mo
re than half the copper mined is still drawn into wire or otherwise employed in communications and electrical applications. Though largely hidden from view, copper has become the symbol of civilization that Wren believed it to be when he thought to use it to cover the dome of St Paul’s.
Au Zinc
Nobody has put their stamp on the city of Berlin more thoroughly than the Prussian architect Karl Friedrich Schinkel. Though he could do Gothic if asked, he is celebrated for his development of a Greek-influenced neoclassical style that tempers its monumentality with superb detailing. It was in this idiom that he designed many of the cultural edifices that give Berlin its austere grandeur today–the Schauspielhaus, the Altes Museum, the Singakademie–as well as churches and villas, and buildings for his patrons, King Frederick William III and his heir, at nearby Potsdam.
These buildings are forthright and impressive, as they were required to be in order to express Prussia’s recently regained independence from Napoleon’s armies and the accompanying influence of the fussy French Beaux Arts style. But appearances are sometimes deceiving. Schinkel began his career designing theatre sets–he devised the still famous hemispherical backdrop of stars for a production of The Magic Flute–and was sometimes more concerned to achieve the right effect than with authenticity. Thus, the statues that punctuate the cornices and pediments of his buildings are not always the stone or bronze they appear to be but are in fact sometimes hollow zinc. Schinkel also designed the Iron Cross, Germany’s highest military decoration, but, belying its name, even this medal was sometimes partly made of zinc.
Zinc was the first useful metallic element to come to light since iron, lead and tin, discovered thousands of years before. A thirteenth-century Indian text describes how the metal was made by heating calamine, a traditional medicament which is principally zinc oxide, with organic matter. This makes zinc the only element with an attributable date of discovery where Western science cannot claim to have made the running. News of the metal came to Europe via China, which was first to exploit zinc on a large scale. The renowned alchemist Paracelsus reported rumours of the new metal in the sixteenth century, and, not long after, samples of zinc wares were brought to the West on trading ships. It was not until the eighteenth century that deposits of ore were located that enabled the metal to be smelted in Europe.
Periodic Tales Page 23