Akademik

   Wrought iron began to appear in India around 1800 BC, and iron smelting is first found in the Nok culture on the African continent by 1200 BC. Iron had gradually replaced bronze, probably after a tin shortage and the higher cost of copper required people to find a new material. Cast iron was then invented in AD 31 by a man named Du Shi, who worked in the Chinese Han Dynasty and created molds to mass-produce figurines, cannons, and pots. It was not until the advent of the Industrial Revolution, however, that superior production methods reduced the cost of cast iron, thus dramatically increasing its use as a major building material.

   Cast iron first appeared as the main structural component in the Severn River Bridge, built by Abraham Darby III in Coalbrookdale, England, in 1779. In this bridge, five parallel castiron arches supporting the roadway replaced the heavy stone voussoirs that would otherwise have formed the arch of the bridge. Iron provided a lighter, more flexible material that became widely popular and created its own aesthetic qualities. When Darby manufactured thinner iron pots at the Coalbrookdale Furnace, the iron industry grew dramatically, quickly filling the surrounding valley with worker housing and necessitating the increasing infrastructure. Thus, cast iron immediately moved from the construction of bridges to use for massive buildings, such as train stations, factories, and then schools and libraries.

   Interest in new materials and technological progress formed the impetus for the London Great Exhibition of 1851 held in the Crystal Palace, built by Joseph Paxton. Paxton, a gardener known for his greenhouse designs, used cast iron, glass, and wood to create in just six months a giant fusion between a greenhouse structure and a railway building. It was unprecedented in scale. The building featured a rectangular hall with side aisles and a barrel vault made of iron-framed glass planes that were almost 30 by 50 inches in size. Cast iron was used to create a structural skeleton into which the iron-framed glass panels could be fitted. Wooden ribs were used to reinforce the glass panes in the curvature of the vault. This building, even with the pre-dominance of glass, provided the largest enclosed interior in its day, with over 18 acres of exhibition space.

   Although cast iron was widely used in internal architectural supports that were then sheathed in more traditional stone or other materials, its bare aesthetic qualities became more highly valued through the 19th century, as it appeared much more visibly in such buildings as the reading room of the Bibliothèque Sainte-Geneviève, built in Paris in the 1840s by Henri Labrouste. The exterior of the building is constructed of masonry, and the entrance foyer has stone columns with cast-iron decoration. In the reading room, thin cast-iron columns with Corinthian capitals and tall concrete pedestals run down the middle of the room to support two flanking parallel barrel vaults. The vault then features curved cast-iron ribs decorated with a classical rosette design.

   It was the Eiffel Tower, built in 1887-1889 along the Seine River in Paris by Gustav Eiffel that really demonstrated to the broader public the incredible technical possibilities of cast iron. At first built only as a temporary structure and denigrated in the local newspapers as an iron monstrosity, the Eiffel Tower came to symbolize modern progress and human achievement. Today, as an observation tower with several restaurants, it is one of the most visited tourist sites in the world, and it also functions as a radio tower. Built for the 1889 Universal Exposition, the 984-foot-tall tower (now 1,063 feet with its radio spire) was the tallest structure in the world until New York's 1,047-foot-tall Chrysler Building was constructed in 1930. The innovative structural design of the Eiffel Tower, with its broad base curving upward gently into a pinnacle, allows it to sway slightly in the wind to withstand the effects of severe weather and time.

   Since cast iron was also used to reinforce concrete, it remained an important material in other major structures as well, in which its own aesthetic qualities were not so glorified. For example, the Beaux-Arts architect Charles Garnier used iron beneath the more traditional stone materials of his opera house in Paris, built in the 1860s. Iron was also used in the United States by architects such as Henry Hobson Richardson, who trained at the École des Beaux-Arts in Paris and worked in a modern historically inspired style, as seen in his Marshall Field Warehouse, built in Chicago in the 1880s. Soon thereafter, steel was introduced as a superior structural material and was subsequently used mainly in skyscraper buildings in the United States.