IELTS Academic Reading Practice Test 492

An escalator is a simple idea: a continuous staircase that carries people between floors. There are thought to be well over a million of them in the world, yet few people look at them twice. Their history, however, is stranger than their appearance suggests. The escalator began not as building equipment but as a fairground attraction, and the arguments that surrounded its early years have never entirely disappeared.

The first person to describe such a machine in a patent was an American, Nathan Ames, who in 1859 registered a design for what he called 'revolving stairs'. His idea was an endless belt of steps running on an inclined track, and on paper it contains most of the elements of the modern machine. No model was ever built. For the next thirty years the moving staircase remained a drawing, partly because the technical obstacles were considerable: a device of this kind needed a power source compact enough to fit inside a building.

The first working version was the work of Jesse Reno, an engineer who had been experimenting with moving belts. Having patented his idea in 1891, he installed an inclined moving walkway at the Old Iron Pier on Coney Island, New York, in 1896. It was not an escalator in the modern sense. Passengers stood on a cleated belt and were carried up a slope, and there were no steps at all. But the machine worked, and it proved that the public would accept being transported by machinery that never stopped. Reno went on to build similar devices in other American cities.

A rival had appeared by then. Charles Seeberger had been working on a design with individual steps rather than a continuous belt, so that passengers could board and leave in the ordinary way. He took his machine to the Paris Exposition of 1900, where it carried visitors up a slope beside a fixed staircase and won a prize. Seeberger also gave the invention its name, joining the Latin word for steps, scala, to part of the word 'elevator'. The name became so widely used that in 1950 a court in the United States ruled that it had passed into ordinary language.

Each design had weaknesses. Reno's belt was awkward to fit into a building, while Seeberger's steps were difficult and expensive to manufacture. By 1911 the Otis Elevator Company, which dominated the lift business, had acquired the rights to both, and its engineers produced a machine that combined them: Seeberger's individual steps, mounted on an endless chain, together with a moving handrail that passengers could hold. The result established the form that is still built today.

The machine's early reputation was made in department stores rather than stations. In 1898 Harrods, in London, installed a moving staircase based on Reno's design and is said to have offered customers brandy at the top to steady their nerves, while a uniformed attendant stood by to help anyone who lost their balance. Passengers in long skirts and leather soles were stepping onto machinery that moved continuously and could not be halted quickly, and early installations were staffed by an operator to start and stop the machine.

Escalators became part of ordinary urban life when the London Underground began to use them. The first was installed at Earl's Court station in 1911, and the company advertised the device as a substitute for lifts, which carried fewer passengers and required people to queue. A deep station, with crowds arriving in bursts with each train, was exactly the place where a continuous stream of moving steps made sense, and other networks soon followed. The escalator changed the design of stations as well as the experience of travelling through them.

Safety came to depend less on attendants and more on engineering. The most important change was the flattening of the steps at the top and bottom of the run, which allowed passengers to stand level before and after the ride, and the addition of a handrail that moved at the same speed as the steps and could be gripped. The treads were given a comb whose teeth mesh with grooves in the step, so that anything caught is pushed clear. Modern machines add yellow markings at the edges of the steps, enclosed sides and an emergency stop button at each end.

Not every escalator runs in a straight line. A spiral design was patented in the early twentieth century and installed at a London Underground station, though it was soon taken out. Curved escalators became practical only much later, when manufacturers developed chains that could turn corners, and they remain rare and expensive. Length, too, has become a mark of prestige. The longest outdoor escalator system, in the Central district of Hong Kong, climbs about 800 metres up a steep hillside and carries commuters to work each morning.

Modern machines face a question that their inventors never considered: what to do when nobody is riding. A motor that runs continuously wastes energy, so many escalators now slow down or stop when a sensor finds that no one is approaching. The saving is substantial, though a stationary staircase can surprise a passenger who expects it to be moving. Behaviour, meanwhile, has proved harder to engineer than the machinery. In London, travellers are asked to stand on the right and walk on the left, a rule enforced not by the machine but by the disapproval of strangers.

Water is a demanding medium for any animal that needs oxygen. It is roughly 800 times denser than air and far more viscous, so a fish must spend a good deal of energy simply moving a litre of it across its body. The reward is modest. A litre of seawater may contain only about 8 milligrams of dissolved oxygen, whereas a litre of air holds more than 200. A fish must therefore pass an enormous volume of water over its respiratory surfaces, and much of its anatomy is shaped by that single requirement.

The organs that do the work are the gills, typically four arches on each side of the throat, supported by curved bones or cartilages. From each arch hang two rows of filaments, and every filament carries hundreds of thin plates called lamellae. The arrangement packs an immense surface into a small space: in a moderately active fish the total area of the lamellae may be several times the area of the animal's skin. It is across the walls of these plates, only thousandths of a millimetre thick, that oxygen passes from the water into the blood.

Efficiency comes from the direction of the blood. Inside each lamella, blood flows from the base of the filament towards its tip, while water passing over the gills moves the other way. Because the two streams run against each other, blood that is already rich in oxygen meets water that is still fully charged with it, and oxygen continues to diffuse inwards along the whole length of the plate. A fish can take up as much as 80 per cent of the oxygen from the water it ventilates; a system in which blood and water flowed in the same direction could extract far less.

Water has to be pumped, and most fish use a double pump. The mouth cavity expands and draws water in; then the mouth closes and the bony flaps covering the gills, the opercula, open so that water is pushed across the gill filaments. The stages overlap, so the flow over the plates never quite stops. Pumping is expensive, and estimates of the share of a fish's energy budget it consumes vary widely. Fast-swimming predators such as tunas and some sharks avoid the cost: they hold their mouths open and rely on the water forced through by their own forward motion, a strategy called ram ventilation. Several species cannot breathe in any other way and suffocate if they stop swimming.

Gills are not only respiratory organs, and this creates a conflict. They are the main site at which fish regulate the salt and water content of their bodies and release nitrogenous waste as ammonia, so the surface must remain permeable to more than oxygen. A membrane thin enough to absorb gas is inevitably exposed to whatever else the water carries, which is one reason why fine sediments and chemical pollutants can harm fish so quickly. The design of a gill is therefore a compromise between breathing and the other business of staying alive.

Some fish have partly escaped the problem by breathing air. Gouramis and their relatives possess a folded chamber above the gills, the labyrinth organ, which is rich in blood vessels and absorbs oxygen from air gulped at the surface. Several other groups use a modified swim bladder for the same purpose, and mudskippers, which spend much of the day out of water, exchange gases through the skin and the lining of the mouth. In most cases the ability is a supplement to gill breathing rather than a replacement for it.

Where oxygen runs short, behaviour changes first. In shallow tropical pools, fish may swim repeatedly to the surface and gulp the layer of water in contact with the air, a behaviour known as aquatic surface respiration; species that do this often tend to have a flatter head and a more upward-facing mouth. Elsewhere the adaptation goes further. In parts of the Amazon, fish survive in water so low in oxygen that other species cannot enter it, and some Antarctic fish of the family Channichthyidae have lost red blood cells and haemoglobin altogether, relying on oxygen dissolved directly in the blood plasma, an arrangement that works only because cold water holds so much more of it.

Much remains uncertain. Researchers can measure how much oxygen a fish takes up in a laboratory tank, but they cannot easily follow the same process in a muddy river or on a reef at night, and the metabolic demands of wild fish are inferred rather than observed. Nor is it clear how far species can adjust. As the ocean warms it holds less dissolved oxygen, and the low-oxygen zones of the open sea have been expanding; whether fish will move to cooler depths, alter the shape of their gills or simply decline is a question that computer models still disagree about, and it matters for fisheries as much as for the animals themselves.

Few questions in education policy are asked as often, or answered as carelessly, as whether apprenticeships should be valued as highly as degrees. In England the ambition has been official for years. A levy on the payroll of larger employers, introduced in 2017, was intended to fund a great expansion of apprenticeship training, and ministers have repeatedly promised what they call parity of esteem between the two routes. Yet the two continue to be spoken of in different registers: the degree as an investment, the apprenticeship as a fallback for those who cannot manage anything else. The question is usually posed as a contest in which one side must win. That framing, I will argue, is the first thing that needs to change.

Economists who study labour markets have most to say about the returns to each route, and their findings are less tidy than the headlines suggest. Averaged across a working life, graduates in most countries earn considerably more than people whose highest qualification is a vocational one taken at the same age. But an average is a poor guide to an individual decision. Studies in several countries have found that a substantial minority of graduates earn less than the typical holder of a technical qualification, and that the subject studied and the institution attended matter as much as the bare fact of holding a degree. A degree, on this evidence, is not one product but many, sold at very different prices.

The choice is not made on level ground either. Young people from poorer families are more likely to be steered towards vocational routes and less likely to have the contacts that make an unpaid internship in a fashionable profession possible. Researchers who study vocational education have found repeatedly that systems sorting children into academic and vocational tracks at an early age tend to reproduce existing social differences rather than reduce them, however good the individual programmes are. Urging more young people into apprenticeships in the name of equality may therefore be premature.

Employers' organisations have a point, though a different one. When the levy was designed, many firms found that money they had previously spent on training was now collected as a tax and could be reclaimed only by registering courses as apprenticeships. Critics argued that existing induction programmes were accordingly relabelled, some of them lasting a few weeks, while genuine craft training with a structured syllabus and an independent assessment became harder to finance. A label that can be attached to almost any course soon tells an applicant nothing, and it is the ambitious school-leaver who suffers most when it does.

Vocational educators make a stronger claim for their own route. Learning on the job, they argue, gives knowledge a context that a lecture theatre cannot: a young cook who has worked through a busy service understands why timing matters in a way that someone reading about it does not. The best apprenticeship alternates between supervised practice and teaching away from the workplace, so that each reinforces the other, and it is assessed by people who do the work themselves. On this view an apprenticeship is not a lesser degree but a different kind of education, with intellectual demands of its own.

University administrators approach the question from the direction of money. The expansion of higher education has been financed largely by shifting costs onto graduates through fees and loans, and universities argue that the real issue is not prestige but who bears the cost of each route and on what terms. Because apprenticeship training is funded by a levy on employers while degrees are funded by a loan repaid from future earnings, the two are discussed as if they were competing products, when the financial rules under which they operate are entirely different.

None of this means that the routes are equivalent, or that either should be abolished. It means that the comparison is the wrong instrument. A degree and an apprenticeship develop different capabilities, and most people will need more than one kind of learning during a working life that may last fifty years. What matters is whether a route leads somewhere: whether employers recognise it, whether it permits further study, and whether a person can change direction without beginning again. A poorly designed apprenticeship, like a poorly designed degree, can cost a young person three years and leave them with a certificate that no employer will pay for.

My own view is that parity of esteem, as usually understood, is an empty slogan. Esteem cannot be legislated, and a route does not become respectable because a minister says that it is. What can be built is a system in which the two connect at several points: a young person who begins an apprenticeship at eighteen should be able to enter the second year of a degree, and a graduate who wants to learn a craft should be able to train without starting from the beginning.

Apprenticeships also need defending from their friends. A scheme that lasts a few weeks and rebadges existing training damages the brand for everyone, and minimum durations, independent assessment and a genuine element of off-the-job teaching are the price of credibility. Above all, the argument should be about the quality of what is offered and about who pays for it, not about which route carries more status.