2,200-Year-Old Chinese Cast Iron Troughs
In 1986, an ancient bridge site, with 112 timber bridge piles covering a field over 300m long, was unearthed in Shaanxi Province. Using carbon-14 dating, the piles were found to be about 2200 years old.
Combining this factor with other evidence, including the discovery in the nearby area of more than 100 artifacts made from bronze, iron or ceramic materials with the style typical to those unearthed from the tomb of First Emperor Qin, Chinese archaeologists concluded the bridge should be constructed during the age between the late Warring States Period and the early Qin Dynasty.
Yet the high probability of being the earliest timber bridge in the world is not the most amazing aspect of this ancient structure. What really extraordinary is the discovery made 3 years after the initial unearth of the bridge site.
In 1989, Chinese archaeologists further unearthed 7 iron troughs on the site, each measuring 6.5m long, 1m wide and 1m high, and weighing 3 tons.
On both ends of the troughs, iron rivets are clearly visible, which must be used to form a channel trough.
What the ancient Chinese were doing with the channel trough? To transport hot liquid iron to produce metal horses, as legend has it?