IELTS Reading: Table completion (Practice with Answers)

The decade 1840 to 1850 saw Britain consume more capital on railways than on anything before it. The mania followed a rhythm: a boom of promotion, a crash of confidence, and a slower consolidation that left the map redrawn.

The first boom, peaking in 1845, produced bills for lines surveyed across every county. Parliament approved what it could not properly examine; companies raised money on drawings alone. When the market broke in autumn 1845, the shares of half the schemes became waste paper within weeks. A second, stranger wave followed in 1846, and it too collapsed, this time dragging country banks down with it. The railway left standing after 1850, some 6,000 miles of track, had largely been built by the sober promoters who bought dead schemes out of receivership.

The social ledger balanced differently from the financial one. The navvies who cut the embankments, a workforce approaching a quarter of a million men at the peak, moved more earth than the pyramid builders and died at rates no actuary published. Farmers gained markets and lost hedgerows; the postal service, riding the new lines, cut delivery times in half; and the telegraph companies, invited to string wire along the routes, turned a transport network into a communication one almost by accident.

The rarest predictable event in astronomy once served as its most useful ruler. A transit of Venus, the planet crossing the face of the Sun, occurs in pairs eight years apart, with more than a century between pairs. Edmond Halley realised in 1716 that timing a transit from widely separated latitudes, and comparing the instants the planet touched the Sun's edge, would let astronomers triangulate the distance from Earth to Sun, the base unit of the cosmos.

Halley's method demanded observations from places Europeans could barely reach, and the transit pairs of 1761 and 1769 turned into the first great international scientific expeditions. Observers sailed for months to observe minutes. The French astronomer Guillaume Le Gentil missed the 1761 transit when war delayed his ship, stayed in the Indian Ocean for the 1769 event, and then cloud covered his chosen site. He returned to France after eleven years to find himself declared dead and his estate divided.

Captain Cook's first voyage carried official astronomers to Tahiti for the 1769 transit, and though their timings disagreed by more than hoped, the pooled results of all the 1769 expeditions fixed the Earth-Sun distance at about 153 million kilometres, within four per cent of the modern value. The method died with the century, superseded by radar and spacecraft telemetry, and the transits of 2004 and 2012, the last until 2117, were watched by millions as spectacle alone.

The twentieth century dammed the world's rivers with missionary confidence, and the ledger is now audited in both directions.

What large dams deliver is scale. A single reservoir can irrigate a province, and hydro's share of global electricity, though static for decades, still exceeds every other renewable combined. Pumped storage, water moved uphill cheaply and released at peak, remains the dominant form of grid storage by capacity, since dams are, in effect, batteries that landscape built.

What they cost took longer to count. Sediment, once free fertiliser for floodplains, stops behind the wall, starving deltas that sink as the sea rises. Migratory fish meet ladders that work for some species and fail most, and the reservoirs themselves, drowning vegetation, emit methane, a greenhouse contribution that in tropical basins can rival fossil plants for their first decades. The human account is starkest: dam resettlement displaced an estimated forty to eighty million people in the century, compensation records poor, outcomes often permanent.

The industry's response has been to shrink its ambitions. Small run-of-river schemes, generating without large storage, promise lower impact and deliver less firmness, since their output follows rainfall. Retrofits, adding turbines to existing walls and even to water pipes, extract energy without new concrete. The megaproject era survives mainly in Africa and Asia, where the unanswered demand is largest, and where the next auditors, environmental and social, are already waiting with the century's lessons.