IELTS Academic Reading Practice Test 49

By the third century AD, the city of Rome was served by eleven major aqueducts, constructed over a period of more than five hundred years. Together they brought a quantity of water into the city that few urban centres would match until the modern era, supplying public fountains, enormous bathing complexes and the houses of the wealthy. The aqueducts are remembered today chiefly for their monumental arches, which still stride across the countryside in many parts of the former empire. Yet the arches are misleading, for the great majority of every aqueduct's length ran through channels at or below ground level.

Rome's first aqueduct, the Aqua Appia, was built in 312 BC on the orders of the official Appius Claudius Caecus, who also gave his name to the famous road, the Via Appia. It was about sixteen kilometres long and almost entirely underground, which protected the water from contamination and made the supply difficult for an enemy to find and cut. Later aqueducts were far more ambitious. The Aqua Marcia, completed in the 140s BC, drew water from springs about 91 kilometres from the city and was celebrated for the coldness and clarity of its water.

The engineering principle behind every aqueduct was simple: water flowed by gravity alone, so the channel had to descend gradually and continuously from source to destination. Achieving this over long distances required remarkable precision. The aqueduct that supplied the Roman city of Nemausus, modern Nîmes in southern France, was about fifty kilometres long, yet it fell on average by only around twenty-five centimetres per kilometre.

Roman surveyors determined levels with instruments such as the chorobates, a long wooden table with a groove that was filled with water to show whether it lay perfectly horizontal. If the slope was too steep, fast-flowing water could damage the channel; if it was too gentle, the flow would slow and deposits would build up.

Natural obstacles demanded a range of solutions. Shallow valleys were crossed on walls or arches, and some of these structures were spectacular: the Pont du Gard, the bridge that carried the Nîmes aqueduct over the River Gardon, stands almost 49 metres high on three tiers of arches. Where a valley was too deep for a bridge, engineers sometimes built inverted siphons, in which sealed lead pipes carried the water down one side of the valley and up the other under pressure, a technique used to supply the city of Lugdunum, now Lyon. Hills were pierced by tunnels, which were dug from vertical shafts sunk at intervals along the route. These shafts also gave workers access for later inspection and repair.

On reaching a city, water usually passed through settling tanks, where the flow slowed and sediment sank to the bottom. It then entered a distribution tank, from which it was divided among different districts and users. At Nîmes, a circular basin of this kind still survives, with holes in its walls from which pipes once led to different parts of the city. Public fountains and baths had priority, while private households could receive a supply only with official permission and on payment of a charge. Pipes within cities were commonly made of lead, although the architect Vitruvius, writing in the first century BC, warned that lead was harmful to health and recommended clay pipes instead.

Running such a system required careful administration. In AD 97 the emperor Nerva appointed the senator Sextus Julius Frontinus as curator of the water supply, and Frontinus wrote a detailed treatise on Rome's aqueducts. Comparing the quantities entering the system with those delivered, he found large discrepancies, which he attributed largely to fraud. Farmers and tradespeople inserted unauthorised pipes into the channels, and some of the workers responsible for the system appear to have profited from illegal connections. Frontinus regarded the aqueducts as the greatest proof of Rome's power, and contrasted their usefulness with the pyramids of Egypt, which he considered pointless.

Maintenance was a constant task. The water of many springs was rich in dissolved calcium carbonate, which gradually built up as a hard deposit on the walls and floor of the channels. Unless it was regularly chipped away, this crust narrowed the channel and reduced the flow, and in some sections of the Nîmes aqueduct deposits several tens of centimetres thick accumulated over the centuries. When imperial authority weakened, such work was increasingly neglected. During the siege of Rome by the Goths in AD 537, the aqueducts were cut, and the city's population, already much reduced, relied increasingly on wells and the River Tiber.

Some Roman aqueducts nevertheless outlived the empire that built them. The Aqua Virgo, completed in 19 BC, was restored during the Renaissance and still supplies water to several of Rome's fountains, among them the celebrated Trevi Fountain. Elsewhere, ruined arches have become tourist attractions and symbols of national heritage. Perhaps the aqueducts' most lasting legacy, however, is the idea they embodied: that a reliable supply of clean water is a public responsibility, to be planned, financed and protected by the state.

In February 1977 the American research submersible Alvin descended about 2,500 metres to the Galápagos Rift, a section of the mid-ocean ridge system in the eastern Pacific. The scientists on board were geologists, searching for the hot springs that the theory of plate tectonics predicted should exist where the sea floor was spreading apart. They found the springs, which were emitting water only slightly warmer than its surroundings. What they had not expected was to find them surrounded by dense communities of animals: giant tube worms, large clams, mussels and crabs. The expedition had included no biologists, since nobody had imagined that there would be anything there to study.

Hydrothermal vents form where seawater seeps down through cracks in the ocean crust, is heated by hot rock or magma beneath, and rises again carrying dissolved minerals. In 1979 an expedition to the East Pacific Rise, off the coast of Mexico, found vents of a far more dramatic kind. Tall chimneys were pouring out fluid at around 350°C, which looked like black smoke. The colour came from metal sulphides that precipitated as the scalding fluid met the near-freezing seawater, and the same minerals had built the chimneys themselves. Despite such temperatures, the fluid does not boil, because of the immense pressure of the water above it.

The discovery of abundant life around the vents raised an obvious question. In the deep ocean there is no sunlight, and most deep-sea animals survive on a thin rain of dead organic material sinking from the surface, a food supply far too meagre to support the densities seen at the vents. The answer proved to be chemosynthesis. Certain microbes obtain energy not from light but from chemical reactions, particularly by oxidising hydrogen sulphide, which is abundant in vent fluid. They use this energy to make organic matter from carbon dioxide, much as plants do using light, and so form the base of an entire food web.

The most striking example is the giant tube worm, Riftia pachyptila, which can grow to around two metres in length. Its feathery plume is bright red because of haemoglobin, which captures oxygen and sulphide from the water. Puzzlingly, the adult worm has no mouth and no digestive system. The explanation was proposed by Colleen Cavanaugh, then a graduate student at Harvard University, after a lecture in which the worm's anatomy was described. She suggested that bacteria living inside the worm were producing its food, and a paper published in 1981 confirmed that an organ called the trophosome was packed with such bacteria, which the worm supplies with the chemicals they need.

Not all vents resemble black smokers. In December 2000 an expedition exploring an undersea mountain near the Mid-Atlantic Ridge, which had not set out to look for vents at all, came across a field of pale chimneys that has since been named Lost City. The tallest rise around 60 metres above the sea floor. Unlike black smokers, Lost City is not heated by volcanic activity. Its warmth is generated instead by chemical reactions between seawater and rock from the Earth's mantle, and its fluids are alkaline and rich in hydrogen and methane. The chimneys are made mainly of carbonate minerals, and they support dense communities of microbes rather than the large animals found at Pacific vents.

Vents such as Lost City have attracted attention far beyond marine biology. Some scientists have proposed that life on Earth may have begun at alkaline vents, where natural chemical differences between vent fluid and seawater could have provided the energy needed for the first metabolic reactions. The idea remains contested, and other researchers favour shallow pools on land. Vents have also become important to the search for life beyond Earth, since several moons in the outer solar system, among them Jupiter's moon Europa and Saturn's moon Enceladus, are thought to have oceans beneath their icy surfaces, in which hydrothermal activity may occur.

Today vent ecosystems face a new threat. The mineral deposits that form around vents can be rich in copper, zinc and gold, and they have attracted the interest of companies hoping to mine the deep sea. Biologists warn that many vent species are known from only a handful of sites. The scaly-foot snail, which protects itself with scales and a shell containing iron sulphide, has been found at only a few vent fields in the Indian Ocean, and in 2019 it was listed as endangered, partly because exploration licences for mining covered parts of its habitat. Vent communities often recover after volcanic eruptions destroy them, but scientists are uncertain whether they could recover from large-scale industrial extraction.

In 2015 Oxford Dictionaries chose as its word of the year not a word at all but a pictograph: the emoji known as Face with Tears of Joy. The decision delighted some observers and appalled others. To enthusiasts, emoji represent a new universal language, capable of crossing barriers between cultures. To pessimists, they are evidence of declining literacy, a slide back towards a primitive form of picture-writing. In my view, both camps misunderstand what emoji are and what they do, and the debate becomes clearer once we stop asking whether emoji are a language.

Pictorial symbols in digital text have a surprisingly long history. In 1982 the computer scientist Scott Fahlman, at Carnegie Mellon University, proposed that users of an online message board mark jokes with a sideways smiling face made of punctuation, so that humorous posts would not be taken seriously. Emoji proper emerged in Japan in 1999, when Shigetaka Kurita, working on a mobile internet service for the company NTT DoCoMo, designed a set of 176 simple symbols, each on a grid of just twelve by twelve pixels. In 2016 the Museum of Modern Art in New York added his original set to its collection. Their global spread followed the inclusion of emoji in the Unicode standard in 2010, which allowed the same symbols to be displayed on devices made by different companies.

Are emoji a language? The answer, I am convinced, is no. A language allows its users to say anything that can be thought: to describe the past and the future, to set out conditions and exceptions, to argue about abstract ideas. Emoji have no grammar capable of doing this. A sequence of pictures can suggest a simple story, but it cannot reliably express the difference between something that happened, something that might happen and something that should not. Attempts to translate entire novels into emoji have produced texts that are almost impossible to understand without already knowing the original.

This does not mean that emoji are trivial. The most convincing account of their role, in my view, comes from linguists such as Lauren Gawne and Gretchen McCulloch, who have argued that emoji work less like words than like the gestures that accompany speech. When we talk face to face, we rely constantly on facial expression, tone of voice and movements of the hands to show whether we are joking, sympathetic or annoyed. Written messages strip all of this away, which is one reason why short texts so often cause offence. A wink or a smile at the end of a sentence restores some of the missing information. Significantly, most emoji appear alongside words rather than replacing them, exactly as gestures accompany speech rather than substituting for it.

Seen in this light, the claim that emoji form a universal language looks particularly weak. Gestures are not universal; their meanings vary between cultures and even between individuals, and the same is true of emoji. In 2016 researchers at the University of Minnesota asked participants to interpret a range of popular emoji and found that people often disagreed about whether a symbol expressed positive or negative feeling. The disagreement was greatest when the symbol looked different on different devices: the same character can be drawn quite differently by each manufacturer, so that what one person sends as a cheerful grin may arrive looking like an awkward grimace.

Such ambiguity is not merely a social inconvenience. Courts are increasingly asked to decide what emoji mean. In 2023 a judge in the Canadian province of Saskatchewan ruled that a farmer who had replied with a thumbs-up emoji to a photograph of a contract for the sale of flax had accepted that contract, and ordered him to pay damages of about 82,000 Canadian dollars when the flax was not delivered. The decision was later upheld on appeal. The case shows that emoji can carry real commitments, but also that their meaning often depends on context, including the history of communication between the people involved.

What, then, of the fear that emoji are damaging literacy? Similar anxieties have greeted almost every change in how people write, from the telegram to the text message. When text messaging became popular, critics predicted that its abbreviations would corrupt young people's spelling, yet the linguist David Crystal argued in 2008 that the evidence did not support such fears. I see no reason to think that emoji are different. Someone who adds a smiling face to a message has not forgotten how to write a sentence, any more than a speaker who smiles has forgotten how to talk.

Emoji, in short, are neither the future of language nor a threat to it. They are a set of tools that allow writers to do something that writing has always done poorly: to convey the tone and feeling that, in conversation, we communicate without words. Like any tool, they can be used well or badly, and they can be misunderstood. But the remarkable speed with which billions of people have adopted them suggests that they meet a genuine need.