Passage 1: The Journey of the Bicycle
A Few inventions look as simple as the bicycle, yet its shape took almost a century to settle. In 1817 the German baron Karl von Drais built a wooden machine with two wheels in line, a steerable front wheel and no pedals. Riders sat on it and pushed along the ground with their feet. The machine, which became known as the draisine or running machine, was quick on smooth roads, and for a short time it was a fashionable toy in several European cities. The craze faded, partly because road surfaces were poor and partly because the machine offered little advantage over walking on rough ground.
B The next real advance came in the 1860s, when French workshops began to fit cranks and pedals directly to the front wheel. This made the machine faster, but it was also uncomfortable on stony streets, and because of its wooden wheels with iron rims it was nicknamed the boneshaker. To go faster still, makers enlarged the front wheel, since a bigger wheel carried the rider further with each turn of the pedals. By the 1870s the result was the high-wheeler, or penny-farthing, with a front wheel that could be more than a metre and a half across.
C The high-wheeler was thrilling to ride and dangerous to fall from. The rider sat high above the ground, almost over the front axle, and a sudden stop could throw them forward over the handlebars. It suited young, athletic men, but it was unsuitable for most people, including women, who in the fashions of the day wore long skirts. Clubs of high-wheel riders did, however, play an important part in cycling history: they campaigned for better roads and showed that cycling could be a serious sport.
D Engineers solved the problem of safety by changing how the power reached the road. In the 1880s the English maker John Kemp Starley produced the Rover Safety Bicycle, with two wheels of similar size and a chain that carried power from the pedals to the rear wheel. The rider now sat low, between the wheels, with both feet able to reach the ground. The basic design of the safety bicycle was so successful that most bicycles today still follow it.
E A second invention made the new bicycle comfortable. In 1888 a Scottish veterinary surgeon, John Boyd Dunlop, fitted his son's tricycle with air-filled rubber tyres to give a smoother ride. Pneumatic tyres soon became standard, and they allowed cyclists to travel faster over rough surfaces with far less effort. The same idea was later applied to motor vehicles.
F By the 1890s cycling had become a craze. Prices fell, and for the first time ordinary workers could afford personal transport. Many historians argue that the bicycle gave women new independence, because it let them travel without a chaperone or a horse. In the twentieth century the arrival of cheap cars reduced the bicycle's importance in some countries, but in others it remained the main means of getting about. Today it is enjoying a revival as cities look for low-cost, clean ways to move people.
Passage 2: How Cities Keep Cool
A Cities are often several degrees warmer than the countryside around them, a pattern known as the urban heat island effect. The main reason is the materials used to build them. Dark roads and roofs absorb sunlight during the day and release the heat slowly at night, while buildings block the wind that would otherwise carry it away. Heat from air conditioners, vehicles and factories adds to the problem. For residents the result is more than discomfort. In long heatwaves, hot nights stop the body from recovering, and the risk of illness rises, especially for older people.
B One obvious response is to plant trees. Trees cool in two ways: their leaves cast shade, and they release water vapour, which draws heat from the air as it evaporates. A street lined with mature trees can be noticeably cooler than a bare one. However, trees take years to grow, need water, and cannot be planted on every street, particularly in older districts where the space beneath the pavement is crowded with pipes and cables.
C Another option is to change the colour of surfaces. White or light-coloured cool roofs reflect much of the sunlight that would otherwise be absorbed, and cool pavements can be made with light aggregate or special coatings. These measures are cheap compared with large building projects, and some cities have offered grants to property owners who adopt them. A drawback is that reflective surfaces can add glare, and in cold winters they may slightly raise heating costs.
D Green roofs, covered with soil and plants, combine several benefits. They insulate the building below, absorb rainwater and provide a small habitat for insects and birds. Critics point out that they are heavy, so older buildings often need to be strengthened, and that they cost more to install than a conventional roof. Supporters reply that the extra cost is repaid over time through lower energy bills.
E Planners increasingly agree that no single measure is enough. The most successful programmes combine trees, lighter surfaces and open spaces with careful design of streets so that breezes can move between buildings. Involving residents is just as important. Programmes tend to work best where people understand why changes are being made, because householders control many of the roofs and gardens in a city. The writer suggests that cities that begin this work now will be better prepared for hotter summers in the future.
Passage 3: Learning That Lasts
A Most students know the feeling of studying hard for an exam and then forgetting much of the material within weeks. In the 1880s the German psychologist Hermann Ebbinghaus tested this experience on himself. He memorised lists of meaningless syllables, then measured how many he could recall after different delays. His results showed what is now called the forgetting curve: memory fades quickly at first, and then more slowly.
B Ebbinghaus also found that reviewing material reduced the speed of forgetting, and that reviews spread over several days worked better than the same time spent in one session. Modern researchers call this the spacing effect. Many later experiments, with school pupils as well as university students, have supported it. The effect is strongest when each review takes place just as the material is starting to be forgotten, because recalling it then takes effort, and effort strengthens the memory.
C Despite this evidence, many students still cram, studying in a single long session just before a test. Cramming can produce good marks in a test taken the next morning, which is why the habit persists, but the knowledge disappears rapidly. Teachers could help by planning courses so that important topics return at intervals instead of being taught once and then dropped.
D A related finding concerns testing. Trying to recall information from memory, instead of simply rereading it, has been shown to improve long-term retention. Researchers refer to this as the testing effect. Students often prefer rereading because it feels easier and more familiar, but this feeling of familiarity can be misleading, as it may make them overconfident. Short quizzes, flashcards and practice questions all make use of the testing effect.
E Technology has made it easy to put these ideas to use. Several language-learning applications now schedule reviews automatically, showing a word again after a longer gap each time it is remembered correctly. The writer cautions, however, that no application can replace motivation: a schedule helps only if the learner actually follows it. Used together, spacing and self-testing allow students to learn more in less time, though not without effort.