Passage I

Sliding Stones to the Forbidden City

[1]

The Forbidden City, built in the fifteenth and sixteenth centuries in Beijing, China, is a complex consisting of the imperial palace and 980 surrounding buildings. A large number of massive stones were used in its construction, some of them featured elaborate carvings. Because China had developed sophisticated wheeled vehicles two thousand years before construction on the city began, scholars assumed that workers had used carts to transport the stones to the site. However, a document translated by researchers Jiang Li, Haosheng Chen, and Howard Stone, in 2013 revealed that workers used a surprising means of transportation; a sledge pulled on ice.[A]

[2]

The document that was later translated by Jiang, Haosheng, and Stone stated that in January 1557 a team of men hauled a 123-ton stone to the Forbidden City on a sledge(a platform with wooden runners). [B] The men pulled the sledge forty-five miles in twenty-eight days, moving about twenty feet per minute.Jiang, Haosheng, and Stone wondered why the workers chose to slide the stones on sledges instead of using carts.[C] They calculated that the city's largest stones—some weighing up to: 300 tons—were too heavy for sixteenth-century carts to carry. In addition, the rough, bumpy roads of the time made maneuvering the carts difficult. Sledges were easier, smoother, and more reliable.

[3]

But how could a team of men only drag a heavy sledge forty-five miles in a few weeks?[D] The researchers discovered that to confront friction, the workers created artificial ice paths that poured water on the ground. They let the winter air freeze the water and then pulling the sledge over the ice. The workers also dug wells along the route so they could pour fresh water over the ice, thereby further reducing friction. The combination of the hard, icy surface and water lubrication were to mean that a small team of workers could move the massive stones quickly and safely. These artificial ice paths made possible the construction of the Forbidden City, one of China's most enduring landmarks.