Suspension bridge types are present in the majority of larger suspension bridges. Although the earlier types of suspension bridges are suitable only for relatively short spans, all of the 14 longest bridges in the world are suspension bridges (see List of longest suspension bridge spans). Ignoring the possibility of pre-Columbian trans-oceanic contact, there were two independent inventions of the suspension bridge, in Eurasia (probably in China) and in Central and South America. Types of suspension bridge include the following: A pure suspension bridge is one without additional stay cables and in which the main cables are anchored in the ground. This includes most
Pontoon bridge points. The "Palsey Pontoon" lasted until 1836 when it was replaced by the "Blanshard Pontoon" which comprised tin cylinders 3 feet wide and 22 feet long, placed 11 foot apart, making the pontoon very buoyant. The pontoon was tested with the Palsey Pontoon on the Medway. An alternative proposed by Charles Pasley comprised two copper canoes, each 2 foot 8 inches wide and 22 foot long and coming in two sections which were fastened side by side to make a double canoe raft. Copper was used in preference to fast-corroding tin. Lashed at 10 foot centres, these were good for