Academic Reading — Test 181

Reading passage

For thousands of years, mariners have depended on fixed sources of light to mark the boundary between safe water and hidden danger. The earliest known structure built specifically for this purpose was the Pharos of Alexandria, completed in Egypt during the third century BC. Standing on a small island at the entrance to the city's harbour, it is thought to have reached a height of well over one hundred metres, making it among the tallest buildings of the ancient world. A fire was kept burning at its summit, and a polished metal mirror was reputedly used to project the glow far out to sea during daylight hours. The tower survived for many centuries before a series of earthquakes finally brought it down, yet its name passed into several languages as the very word for a lighthouse. In the medieval period, the lighting of coasts was often an informal affair. Monasteries and local communities sometimes maintained beacons on prominent headlands, partly as an act of charity towards sailors and partly because shipwrecks could be turned to profit by those who salvaged the cargo. Open fires of wood or coal remained the standard light source, but they were unreliable: rain could douse them, and the smoke they produced often obscured the very flame that ships were straining to see. The fuel also had to be hauled up the tower by hand, a laborious task that limited how brightly and how continuously a beacon could burn. The decisive change came not from a new building method but from a new way of handling light. In 1822 the French physicist Augustin-Jean Fresnel introduced a lens that bore his name. Rather than relying on a single thick piece of glass, which would have been impossibly heavy, the Fresnel lens was built from a series of concentric rings of glass arranged around a central core. This design gathered light that would otherwise have scattered uselessly in all directions and bent it into a narrow, concentrated beam. The effect was dramatic: a relatively modest flame could now be seen from far greater distances than before, and the beam could be made to rotate or flash in distinctive patterns. Because each lighthouse could be given its own rhythm of light, sailors were at last able to identify exactly which station they were looking at. Building the towers themselves posed problems of a different order, especially where they were needed most: on isolated rocks battered by the open sea. The English engineer John Smeaton tackled this challenge when he rebuilt the Eddystone Lighthouse, off the south-western coast of England, in the 1750s. Earlier wooden structures on the same reef had been destroyed by storms and fire. Smeaton turned to stone, shaping the blocks so that they interlocked with one another like the pieces of a wooden joint, and he modelled the wide, curved base of his tower on the trunk of an oak tree, which he reasoned would resist the force of the waves. He also experimented with a form of cement that would set even when submerged in water, a development that influenced later work in concrete. His tower stood for well over a century. The people who tended these structures led demanding and frequently solitary lives. A lighthouse keeper was expected to trim wicks, polish the lens, wind the clockwork mechanisms that turned the light, and keep meticulous records of weather and passing vessels. On remote offshore stations, keepers might be cut off from the mainland for weeks at a time, and the work demanded constant vigilance through the night. In some countries, the role became hereditary, passing from one generation of a family to the next, though the isolation was widely acknowledged to be a strain on those who endured it. In the twentieth century, technology gradually made the human keeper unnecessary. Electric lamps replaced oil flames, and automatic timers took over the task of switching the light on and off. By the closing decades of the century, the great majority of lighthouses around the world had been automated, their keepers withdrawn and their daily routines handed over to machines. The arrival of satellite navigation, which allows a vessel to fix its position with remarkable precision, raised the question of whether physical lighthouses were needed at all. Yet many have been retained as a reliable backup, since electronic systems can fail, and others have found a second life as museums or tourist attractions. The lighthouse endures, then, not only as a working aid to navigation but as a powerful symbol of guidance and safety.