The first bridges with a structure of load-bearing iron elements were suspension bridges. The idea of a suspended bridge is extremely old; the first known footbridge, using suspension chains, was constructed in China around 65 A.D. However, until the end of the 18th century, very few bridges were constructed from metal. The weight of the chains limited spans to around 20 m, and only the invention of chains made of articulated iron bars, known as eye bars and patented in England in 1817, allowed spans to substantially increase. The first important suspension bridge by the Englishman, Telford, was constructed over the Menai Straits in 1826 and is noteworthy for achieving a record span of 176 m. This bridge is still in service, the original iron chains having been replaced by articulated steel bars in 1938.