IELTS Academic Reading Practice Test 37

A Glass is one of the oldest manufactured substances known to humanity, with a largely recorded history stretching back more than five thousand years. The earliest evidence of deliberate glass production has been traced to Mesopotamia and Egypt around 3500 BCE, where craftsmen learned to fuse silica sand with plant ash and lime to create small beads and decorative items. These early specimens were opaque and richly coloured, prized as substitutes for gemstones such as lapis lazuli and turquoise. Because the raw ingredients had to be melted at extraordinarily high temperatures, glass remained for centuries a luxury commodity produced in small workshops attached to royal courts.

B A pivotal transformation is said to have occurred in the first century BCE along the Syro-Palestinian coast, where an unknown craftsman discovered that molten glass could be inflated at the end of a hollow iron tube. This technique, known as glassblowing, dramatically reduced production time and made it possible to fashion vessels of varied may shape with thinner walls. Within decades the technology had spread throughout the Roman Empire, and by the reign of Emperor Augustus, glass vessels had become common household items even among ordinary citizens. Roman glassworks at Cologne and Aquileia are said to have produced thousands of pieces a year, supplying markets from Britain to Persia.

C After the collapse of the western Roman Empire, glass-making in Europe contracted sharply, surviving largely in monastic workshops that produced coloured panes for church windows. The art reached an early medieval peak in the great cathedrals of France and Germany, where stained glass became an instrument of religious instruction for largely illiterate congregations. Meanwhile, in the Islamic world, glassmakers in cities such as Damascus and Aleppo developed sophisticated techniques of enamelling and gilding, producing mosque lamps and beakers that were eagerly sought by European nobility through the trade ports of Venice.

D Venice itself emerged as the dominant glass-making centre of the late medieval period, a position it held for nearly four hundred years. In 1291 the Venetian Senate ordered all glassworks to relocate to the island of Murano, ostensibly because of the fire risk posed by their furnaces, but in practice, it would seem, because the move made it easier to keep trade secrets from leaking abroad. Murano craftsmen, known as cristallai, are said to have perfected a technique for producing exceptionally clear glass by using purified sand from the Ticino River and a special form of plant ash termed barilla. The penalty for a Murano glassmaker who attempted to emigrate could, include the assassination of his family members left behind in Venice.

E The Venetian monopoly was eventually broken in the seventeenth century. In 1674 the English merchant George Ravenscroft patented a recipe that added lead oxide to the melt, producing a heavier, more brilliant material that came to be known as flint glass or English lead crystal. Ravenscroft's innovation gave the English glass industry a decisive advantage in optical applications, including the manufacture of telescopes and microscopes. At roughly the same time, the French royal manufactory at Saint-Gobain pioneered a casting method for plate glass that allowed the production of large mirrors of uniform thickness, transforming the interiors of European palaces.

F The Industrial Revolution is widely held to have mechanised many stages of glass production that had previously depended almost entirely on the lungs and skill of the human glassblower. The most significant breakthrough was the Owens automatic bottle machine, patented by Michael Owens of Toledo, Ohio, in 1903. A single Owens machine could produce around 2,500 bottles an hour, replacing the work of several teams of skilled artisans. Within two decades the price of glass bottles fell by more than 80 percent, and glass containers became universal in the food, beverage, and pharmaceutical industries. Sheet glass for windows was similarly transformed by the Pittsburgh process and, after 1959, by the British float-glass technique developed by Alastair Pilkington, in which molten glass is floated on a bath of liquid tin to yield virtually perfectly flat panes.

G Modern glass science has expanded the material's role far beyond windows and bottles. Optical fibres drawn from extremely pure silica now carry virtually all long-distance telecommunications, while specialised glass-ceramic composites form the heat shields of spacecraft and the cooktops of domestic kitchens. Architectural glass treated with metallic coatings can selectively reflect infrared radiation, helping to regulate the energy consumption of large buildings. Despite these advances, the basic chemistry of glass-making has changed remarkably little since the days of the first Mesopotamian artisans: silica, an alkali to lower the melting point, and a stabiliser to prevent dissolution generally remain its essential constituents, a continuity that links the smartphone screen to the bead from a royal tomb.

A The migratory feats of sharks have, long puzzled biologists. Tagging studies broadly indicate that great white sharks routinely travel between the coasts of California and Hawaii, covering more than 3,800 kilometres of open ocean and arriving each year at the same offshore feeding grounds. Hammerhead sharks aggregate annually at distinct seamounts in the Gulf of California, and bull sharks apparently travel hundreds of kilometres up freshwater rivers and return to the sea with unerring accuracy. In virtually each case the animal seems to navigate through environments that lack obvious visual landmarks, often at depths where sunlight is heavily attenuated and currents would carry an unguided swimmer far off course.

B For decades, researchers suspected that sharks were exploiting the Earth's magnetic field, but obtaining direct experimental evidence proved exceptionally difficult. Sharks are large, fast, and unsuited to standard laboratory chambers, and the field largely generated by a magnet placed near a tank can easily be disturbed by metal fittings or by other sharks in nearby pools. The breakthrough is said to have come in 2021, when a team led by Dr Bryan Keller of Florida State University devised a six-metre cubic enclosure constructed entirely of wood and powered by an electromagnetic coil arrangement known as a Merritt cage. The cage could reproduce, within centimetres of accuracy, the magnetic conditions found at any chosen point on the planet's surface.

C Keller and his colleagues collected juvenile bonnethead sharks, a small species in the hammerhead family, from coastal waters near St Helena Sound in South Carolina. These animals are known to return year after year to the same estuaries to give birth, which suggests that they carry an internal map. In the chamber, each shark was exposed to one of three magnetic conditions: the local field of the capture site, the field of a location 600 kilometres to the north, and the field of a location 600 kilometres to the south. Sharks exposed to the local field swam in random directions, but those exposed to the northern field consistently oriented southward, as if attempting to return home. The result was, the first clear behavioural demonstration that a shark species uses geomagnetic cues to compute its position rather than merely its direction of travel.

D The capacity to deduce position from magnetic information apparently may require more than a simple compass. The Earth's magnetic field varies in two key parameters across its surface: total intensity, which strengthens from the equator toward the poles, and inclination, the angle at which field lines plunge into the planet. By detecting both parameters simultaneously, an animal can, in principle, determine its latitude with considerable precision. Some species are also thought to use the slight east-west variation in declination, the difference between magnetic north and true north, to estimate longitude, although the experimental evidence for this remains contested.

E The biological sensors responsible for magnetoreception in sharks are not yet fully characterised, but two candidate mechanisms reportedly dominate current thinking. The first involves clusters of magnetite crystals located in tissues near the brain. Magnetite, an iron-containing mineral, behaves like a microscopic compass needle and could, in principle, transmit mechanical signals to neighbouring nerve cells when the surrounding magnetic field changes. The second mechanism centres on the ampullae of Lorenzini, the network of jelly-filled canals on a shark's snout that detect the tiny electrical fields produced by the muscles of its prey. Because a shark swimming through the Earth's field induces electrical currents in these canals, the same organs may serve dual purposes as electrosensors and magnetic compasses.

F Beyond their intrinsic scientific interest, these discoveries reportedly have practical consequences for conservation. Roughly a third of all shark species are now classified as threatened, and the construction of submarine cables, offshore wind farms, and seabed mining operations is generating significant artificial magnetic fields along coastlines. Bonnethead sharks placed near high-voltage direct-current cables have been observed to circle erratically, which suggests that such infrastructure may interfere with their navigation. Marine biologists are now working with engineers to design cable layouts and shielding materials that minimise magnetic distortions in shark migration corridors.

G Sharks are not the only marine animals to exploit the planet's magnetic field. Sea turtles return to nest on the same beaches where they hatched, salmon find their natal streams after years at sea, and spiny lobsters orient themselves correctly when displaced from their home reef. Comparative studies broadly suggest that magnetoreception may be an ancient sensory ability, possibly present in the common ancestor of vertebrates more than 500 million years ago. If this is indeed correct, the navigational feats of the great white shark are not an isolated marvel but the product of an inheritance shared across much of the animal kingdom, refined by hundreds of millions of years of selection in environments that demanded precise long-distance travel.

A The study of leadership has produced more theories, models, and frameworks than perhaps any other topic in organisational psychology. The earliest scholarly approach, broadly dominant in the late nineteenth century, was the so-called Great Man theory associated with the Scottish historian Thomas Carlyle. According to this view, history is shaped by exceptional individuals whose innate qualities apparently equip them to direct the course of events. The Great Man theory implied that leadership ability is largely inherited, can be observed from an early age, and is the preserve of a small natural elite. Although the theory enjoyed considerable popularity in business and military circles, it was attacked even within Carlyle's lifetime by the philosopher Herbert Spencer, who argued that leaders are themselves products of the societies that produce them.

B The early twentieth century saw the Great Man theory displaced by the trait approach, which retained the assumption that leadership stemmed from stable personal characteristics but attempted to identify those characteristics empirically. Researchers measured intelligence, self-confidence, height, persuasiveness, and dozens of other variables in groups of recognised leaders and compared them with the population at large. A 1948 review by the American psychologist Ralph Stogdill, surveying 124 such studies, concluded that no single trait or combination of traits reliably predicted leadership across different situations. Stogdill's verdict effectively ended the dominance of the trait approach, although interest in personality has revived in recent decades thanks to the development of more robust statistical methods.

C The next generation of theorists turned away from the leader and toward the act of leading. Behavioural research conducted at Ohio State University and the University of Michigan during the 1950s identified two broad categories of leader behaviour: task-oriented behaviours, which focus on organising work and clarifying expectations, and people-oriented behaviours, which focus on relationships and morale. The most effective leaders, the researchers argued, were those who scored highly on both dimensions. The behavioural approach offered a hopeful message for organisations: if leadership consists of observable acts rather than fixed traits, then leadership skills can in principle be taught.

D By the 1970s, however, even the behavioural approach was felt to be too rigid. Contingency theorists argued that no single style is uniformly effective; rather, the right style depends on the situation. Fred Fiedler proposed the first widely cited contingency model, which classifies situations according to how favourable they are to the leader along three dimensions: the quality of the leader-member relationship, the structure of the task, and the leader's formal authority. Task-oriented leaders, in Fiedler's view, generally perform best in extremely favourable or extremely unfavourable situations, while relationship-oriented leaders typically excel in moderately favourable ones. Other contingency models, notably the path-goal theory of Robert House, focused on how leaders may adjust their style to clarify the route to subordinate goals.

E A more recent and reportedly influential strand of research has largely emphasised the symbolic and motivational aspects of leadership. James MacGregor Burns, writing in 1978, distinguished between transactional leaders, who exchange rewards for compliance, and transformational leaders, who inspire followers to transcend their own interests for a collective vision. Transformational leadership, as elaborated by Bernard Bass in the 1980s, comprises four components often summarised as the "four I's": idealised influence, inspirational motivation, intellectual stimulation, and individualised consideration. Empirical studies have repeatedly shown that transformational behaviours appear to be associated with higher employee commitment, lower turnover, and stronger team performance, though some critics argue that the underlying construct is hard to disentangle from simple charisma.

F Servant leadership, a concept first articulated by Robert Greenleaf in 1970, offers yet another perspective. For Greenleaf, the leader's primary obligation is to the growth and welfare of those being led; authority is held to flow upward from those served rather than downward from a hierarchical position. Studies in healthcare and education have linked servant leadership to higher staff well-being and reduced burnout, although it remains less prominent in conventional management curricula than transformational or contingency models.

G Recent decades have seen leadership research expand to address authenticity, ethics, and cross-cultural variation. Authentic leadership, championed by Bruce Avolio and others in the early 2000s, emphasises self-awareness and consistency between a leader's stated values and actual behaviour. The GLOBE project, a multi-decade study covering more than sixty societies, has shown that some leader attributes such as integrity and inspirational vision are valued almost universally, while others, including assertiveness and individualism, are prized in some cultures and resisted in others. These findings broadly caution against assuming that leadership models developed in North America or Europe can be exported uncritically to other contexts.

H The proliferation of leadership theories has itself become a subject of scholarly comment. Some observers note that few earlier frameworks are ever decisively rejected; instead, they tend to be absorbed into successor models as special cases. Others worry that the field has become an industry of branded approaches, each marketed with consultancy fees, popular books, and assessment instruments of varying psychometric quality. Despite these reservations, a broad consensus has emerged that effective leadership is neither a fixed personal endowment nor a simple toolkit of techniques but a dynamic interaction between the leader, the followers, and the environment in which they jointly operate, and that any rigorous account must grapple with all three.