
The foundations of the piers were dug out inside wrought-iron caissons sunk 25 feet into the riverbed and filled with concrete.The piers, 70 feet wide and 185 feet long, were built with Staffordshire bricks with granite facings. They were built hollow, as they had to contain massive chambers for the counterbalanced ends of the bascules. The towers were built with a skeleton of steel girders, making them strong enough to take the strain of opening the central bascules, and were additionally braced by three landing floors and the iron walkways. The walkways consist of two 95-foot cantilevers, which support a central linking girder. The side spans are supported by steel suspension chains attached to the main towers and the abutment towers. All the steelwork was supplied and built by Sir William Arrol & Compamy. It was made in Glasgow and delivered by steamers to be assembled on site, using cranes, which were moved up as each stage was completed. Great care was taken at all times to prevent any tools or rivets falling into the river, as many boats, including pleasure steamers, were constantly passing through. So as not to obstruct the passage of ships, the bascules had to be built in the vertical position.