Side-spar cable-stayed bridge of this type (supported by a spar), traveling through a much smaller arc, was one of the original proposals for the eastern span replacement of the San Francisco-Oakland Bay Bridge. Similar bridges, without the spar, could be supported by cables anchored in the canyon walls (where conditions are suitable). This subtype should not be confused with an asymmetrical single tower cable-stayed bridge, which possesses a single tower on one side of the gap to be crossed (see Rama VIII Bridge), nor with the cantilever spar cable-stayed bridge, which has span supporting cables on only one side of the tower along
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