IELTS Academic Reading Practice Test 442

Anyone who strikes a match today performs an action that was once genuinely dangerous. The first practical friction match was made in 1826 by John Walker, a chemist in the town of Stockton-on-Tees, who was experimenting with a paste of potassium chlorate and antimony sulphide. Walker began selling cardboard splints coated with the paste, together with a folded piece of sandpaper for striking them, and they were soon nicknamed Congreves, after a famous rocket. He never patented the idea, and others quickly copied it.

During the 1830s manufacturers in several countries began adding white phosphorus to the head of the match, since it ignites at a temperature only slightly above that of the human body. The results were cheap and spectacular. Matches nicknamed lucifers flared with a shower of sparks, produced clouds of acrid smoke and could be struck on almost any rough surface. They also ignited in the pocket, sometimes spontaneously, and the phosphorus coating was lethal to small children who chewed the heads. The workshops in which the matches were made were equally hazardous.

White phosphorus is a poison, and the vapour given off while matchsticks were dipped attacked the jawbones of the people who handled it. The condition, known as phosphorus necrosis or phossy jaw, began with toothache and swollen gums and could end in the surgical removal of part of the jaw. Those most exposed were young women and girls who worked in unventilated rooms for very low pay, and who had little choice but to accept the risk.

Their grievances brought about the celebrated strike at the Bryant & May factory in east London in 1888. The women who walked out were protesting not only at their pay but at the fines imposed for lateness and at the conditions in which they worked, and their cause was taken up by social reformers and by the press. The company eventually conceded most of their demands, and the dispute became a landmark in the history of British trade unionism. It did not, however, end the use of white phosphorus.

The solution was not a safer chemical but a different arrangement of the same chemistry. In 1844 a Swedish chemist named Gustaf Erik Pasch patented a match in which the phosphorus was removed from the head altogether and placed instead on a separate surface, a strip glued to the outside of a small box. The head of Pasch's match contained potassium chlorate, which supplies oxygen, while the strip contained phosphorus. A match could therefore be lit only by drawing it across the strip. Pasch's design was never a commercial success, partly because the head was attached to the splint too weakly and fell off, and partly because it was difficult to make in quantity.

The design was rescued by a Swedish manufacturer, Johan Edvard Lundström, who founded a match factory with his brother in the town of Jönköping in 1845. Lundström patented an improved safety match in 1855 and, with his brother, developed machinery and a manufacturing process that turned Pasch's fragile prototype into a reliable product. Later versions of the match used red phosphorus, a much less poisonous form of the element, on the strip instead of white. By the second half of the nineteenth century Jönköping had become one of the world's centres of match production, and Swedish safety matches were exported across Europe and beyond.

A modern safety match works as follows. The head is a mixture of potassium chlorate, sulphur or a sulphur compound, glue and an inert filler such as powdered glass or chalk. The strip on the box is coated with red phosphorus together with fine sand, which provides grip. When the head is drawn across the strip, friction generates a small amount of heat. A trace of the red phosphorus vaporises, ignites in the air and decomposes the chlorate, which releases oxygen. The sulphur then burns, and the flame is carried to the splint. The splint itself has been soaked in wax or paraffin so that it burns steadily.

Because the head contains no phosphorus, the match cannot easily be lit by accident, and a box of safety matches is safe to store, to carry and to drop. The older 'strike-anywhere' match, by contrast, kept its phosphorus — or, later, phosphorus sesquisulphide — in the head and could be struck on a boot or a wall. In countries where timber houses were common, the safety match had an obvious advantage, and it gradually displaced its rival for domestic use.

White phosphorus nevertheless persisted in the factories that made the strike-anywhere match. Reformers campaigned for decades, reporting on the victims of phossy jaw and pressing governments to act. In 1906 an international convention signed at Berne agreed to prohibit the use of white phosphorus in match manufacture, and Britain passed a law banning it in 1908. In the United States, where regulation was left largely to the tax system, a federal duty made white phosphorus matches uneconomic, and the industry converted to safer compounds.

The safety match has now largely been replaced by the disposable lighter, and the factories of Jönköping have closed, though a match museum preserves their history. Yet the little box remains a model of intelligent design. Its lesson is not that chemistry should be abandoned because it can be harmful, but that a hazard can often be designed out of an object, moved to a place where it does no harm, instead of being left to the care and caution of the user.

Oysters are bivalve molluscs. Yet a few species — among them the eastern oyster of the North American Atlantic and Gulf coasts and the flat oyster of European waters — are also builders. Where conditions suit them, they settle in enormous numbers and construct reefs of their own shells. These reefs are alive. They are living structures, riddled with crevices, that can stretch for kilometres along a shoreline.

An oyster's shell is secreted by the mantle, a thin fold of tissue that lines the inside of the valves. Cells in the mantle take carbonate and calcium from the seawater and deposit them, together with a protein, as crystals of calcium carbonate. The shell grows by adding layers to its inner surface and to its growing edge, and it records the animal's circumstances as it does so: growth is fast in warm water with plentiful food and slow in cold or crowded conditions. Older shells therefore preserve a record of past water conditions that scientists can read, rather like the rings of a tree. The shell is heavy because it must resist crabs, whelks and other predators that can crush or drill through it.

Reefs begin with reproduction. Adults release eggs and sperm into the water, and the resulting larvae drift as plankton for two or three weeks. A larva then has to find a hard surface on which to settle. Tests in tanks have shown that larvae settle far more readily on the shell of adult oysters than on stones, and that they respond to chemical traces released by the shells. This gregarious habit is what makes a reef possible: each generation builds on the last. Once a larva has settled, it cements itself in place and will never move again, and a single shell may carry dozens of young oysters, known as spat.

The reef itself grows upward because each generation of oysters settles on the shells of its predecessors. On soft mud the process cannot start without something hard — a stray shell washed in by a storm, a stone, or the remains of an old reef — and the first settlers often fail. Once a reef is established, however, it can build faster than the sea rises, provided that food is plentiful and that sediment does not bury it. Oysters raised above the mud escape being smothered, but they are exposed to drying air at low tide, to summer heat and to the birds that feed on them, while those lower down are safer from the weather but more likely to be buried.

A dense reef changes the water around it. Oysters feed by pumping water through their gills and straining out particles of algae, and in doing so they remove some of the excess nutrients that otherwise feed algal blooms. The reef's crevices, meanwhile, provide shelter for shrimps, crabs, small fish and worms, many of which are themselves food for larger species, and the whole structure acts as a breakwater that softens the waves reaching salt marsh and shoreline. For all these reasons, coastal managers increasingly regard reefs as infrastructure rather than simply as a fishery.

Yet the reefs have been destroyed on a vast scale. Dredges dragged across the seabed to collect oysters take the shell with them, and shell is precisely what the next generation of larvae needs; once the hard base has gone, a reef cannot renew itself. Harvesting also removed oysters faster than the animals could replace them, so the population fell long before the reefs themselves disappeared. Silt from cleared land and from rivers chokes the survivors, and two diseases caused by microscopic parasites have killed oysters over wide areas. One widely cited international assessment concluded that roughly 85 per cent of the world's oyster reefs had been lost, and that many of those remaining were too depleted to recover without help. In many estuaries, all that remains is a thin scattering of shell where a three-dimensional reef once stood.

Restoration is difficult and expensive. The usual method is to lay down a hard base. Shell left over from processing plants is often used, together with limestone or concrete blocks. Some modules, known as oyster castles, add height where the bottom is soft mud. Hatcheries rear larvae and encourage them to settle on fragments of shell, producing spat that is then returned to the sea. Because young oysters are easily lost, many projects place their reefs inside sanctuaries where harvesting is banned, and they monitor the site for several years. Such work depends on grants and donated shell as well as on paid labour, and even a small reef can consume large quantities of material. In New York Harbor, a project has aimed to restore a billion oysters to the estuary, using reefs built largely by volunteers and schoolchildren.

What remains uncertain is whether restored reefs will last. Warmer water carries less oxygen and encourages the parasites that cause disease, and the gradual acidification of the ocean makes it harder for any shelled animal to extract carbonate from seawater. Estimates of how much water a single oyster filters vary enormously, from a few litres a day to nearly two hundred, so claims about the cleansing power of a reef should be treated with caution. Nor is it clear whether a restored reef will reproduce enough to sustain itself once the initial planting is over. These are not reasons to give up, but they are reasons to measure results honestly rather than to announce success too soon.

For most of the twentieth century a university degree was unusual enough to be a passport. Today, in many wealthy countries, roughly half of young adults enter higher education, and participation has risen sharply in middle-income countries as well. The cost to the student has risen too. Universities in England charge domestic undergraduates around £9,500 a year in tuition fees, and in the United States outstanding student debt is generally reported to exceed one and a half trillion dollars.

Those who defend the degree point first to the labour market. Labour-market economists note that the earnings gap between graduates and people who left school at eighteen has proved remarkably durable, surviving the expansion of higher education and several recessions. Across the industrialised world, the Organisation for Economic Co-operation and Development reports that adults with a tertiary qualification earn substantially more than those whose education ended at upper secondary level. In some rich countries the gap has widened further, as the number of well-paid jobs for people without such a qualification has shrunk. On this view the fees are a modest down payment on a large return.

Others are less sure that graduates earn more because they have learned more. Economists who study signalling — a body of work associated with Michael Spence, who shared a Nobel prize for it — argue that education may chiefly reveal qualities that employers cannot otherwise observe. To finish a three-year course, a student must be organised, persistent and capable of meeting deadlines, and a degree certifies these attributes at a glance. Supporting evidence is that the earnings jump associated with a completed degree is larger than the years of study alone would predict; the certificate matters, not just the teaching behind it.

Employers, meanwhile, have their own reasons for demanding degrees. A degree is a cheap filter: instead of testing every applicant, a firm can simply exclude those without one. Some management researchers have argued that this habit has spread well beyond the jobs that need a degree, so that posts once filled by school-leavers now advertise for graduates. If that is right, part of the cost of a degree is not the teaching but the queueing: students pay for a credential that allows them to be considered for work they could have done at eighteen.

The average, moreover, conceals enormous variation. The return on a degree depends on the subject studied, the institution attended and the student's background. Researchers who model lifetime earnings have found that some courses leave their graduates barely better off than non-graduates once fees and lost earnings are taken into account, while others are worth a fortune. National statistics suggest that fewer than two-thirds of American students who begin a bachelor's degree complete it within six years, and a student who leaves with debt but no certificate has paid much of the cost and received little of the benefit.

Sociologists of education point to a further complication: the value of a degree is partly social. Universities bring students into contact with people and institutions they would not otherwise encounter, and a degree from a famous university carries a prestige that no examination result can confer by itself. Employers often recruit from a small number of institutions because it is easier, not because the teaching there is better. Part of what looks like a return on education may therefore be a return on the advantages a student already had before arriving.

Critics of mass higher education take a different view. They maintain that too many students are now enrolled in courses that neither they nor the economy needs, and that the expansion has diluted the value of a degree for everyone. Public money, they argue, would do more good if it were spent on technical and vocational training. Their case is weaker than it sounds. Apprenticeships and technical routes have expanded in several countries over the past decade, yet the evidence that they offer a cheaper path to secure, well-paid work remains mixed, and some of the new places appear to have replaced training that employers once provided.

My own view is that a degree is still worth its cost for most young people. The decisive argument is not that the average graduate prospers; it is that the alternative — entering the labour market at eighteen with only school qualifications — has become steadily less attractive as routine work has been automated. A degree is the safer of two imperfect options.

The question that matters is not whether degrees pay on average but whether a particular course at a particular university will pay for a particular student. The risk should be shared, through loans repaid in proportion to income, rather than loaded onto eighteen-year-olds and their families. And a degree should not be the only respectable route into a decent job.

Arguments about whether a degree is worth it are usually arguments about averages, and averages are the wrong tool. The more useful questions are narrower: which courses repay their cost, which students are most exposed if they do not, and how the burden can be shared when a gamble fails. Universities could answer the first by publishing detailed earnings data, and governments can address the second and third through the design of loans. Until they do, school-leavers will continue to make the most expensive decision of their lives on the basis of a single average and a great deal of family folklore.