The Alchemy of Us: How Humans and Matter Transformed One Another

Chapter 2 discusses the properties of steel, its use in the production of railway lines, and the impact of these advances on commerce. When carbon reacts with iron, it releases two new materials that divide into layers. One layer has a high carbon content and is strong and rigid. The other layer has a lower carbon content and is soft and malleable. Together, the layers form steel. The combination of strength and malleability makes steel extremely versatile. Obtaining the right amounts of carbon to produce steel proved difficult until the English inventor Henry Bessemer made a critical discovery in 1855. Bessemer exposed pig iron (molten crude iron) to air. He blew air directly into the bottom of a molten metal bath with a pipe, resulting in a volcano-like eruption. The technique removed excess carbon from the pig iron, converted the material into malleable iron, and allowed Bessemer to reintroduce the precise amount of carbon to make steel.

By the 1860s, steel was widely used in a variety of industries, notably railways. Before this period, railway lines were made of iron that had to be replaced every two years. By contrast, steel rails can last 18 years.