THE TOWER BRIDGE.
Further communication across the Thames at this point had been urgently needed for many years. The necessary Act was passed in 1885, the foundation-stone laid by the Prince of Wales on June 21, 1886, and the work completed, at a cost of about a million sterling, in 1894. The bridge, designed by Mr. Wolfe Barry, CB., is of somewhat peculiar construction, the low-level passage being on the "bascule" principle i.e., the centre span of 200 feet is divided into two, each half being pivoted and furnished with a counterpoise, and hauled upward and back against the towers when the waterway is opened; the bridge is shown thus opened in the view. A high-level footway is also carried across nearly at the top of the towers, access to this being afforded by lifts in the latter. The side spans are on the suspension principle.
source: The Queen's London : a Pictorial and Descriptive Record of the Streets, Buildings, Parks and Scenery of the Great Metropolis, 1896