The bridge mechanism is still driven by the original Armstrong hydraulic engines, although the steam pumps were replaced by small electric pumps in 1959. The pumps force water into the chambers of hydraulic accumulators, sunk down into the bed of the river. When the motors cut out, 60-ton weights above the chambers force water out under pressure which run the machinery to turn the bridge. The bridge now opens only very rarely and is controlled from the cupola above the superstructure.
The book is the story of how Tyne Commissioners:
... raised the Tyne from being a shallow stream, dangerous and intricate of navigation to vessels of modern days, into a stately and deep river, capable of accommodating the largest vessels afloat almost at all times of tide - a river, with its deep-water dock and other appliances, scarcely, if at all, surpassed by any of the great ports of the nation for carrying on a vast and expanding commerce.
As the largest work of its kind in England, the following measurements of the bridge may not be uninteresting :—The total length between the abutments is 530ft.; the width of roadway 22ft, and of the footpath 8 and 9ft. The six spans of the bridge are divided as follows : Two are in the centre to open by the swing, each giving 103ft. clear waterway; that on the north side is 99ft. span over the river, and that on the south 71ft. Another span on the Newcastle side for the quay extension is 30ft clear of the roadway, and the south, for the proposed Gateshead quay, 21ft 6in. clear roadway. The total length of the swing span is 278ft. 6in, and its weight 1,500 tons. There is a clear headway, above high water mark, under the swing at the highest point, of 16ft 10in. The elevation of the valve house platform above the roadway is 28ft, and to the top of the lantern exactly 49ft.The greatest depth of the main girders’ swing span is 25ft., of the fixed river spans 10ft., and there is a clear headway under the valve platform arch of 24ft. The swing bridge rests on 42 rollers, each 3ft. in diameter and 10in, wide. These travel on a "racer" or roller path 43ft. in diameter. To move this mighty structure only one hydraulic engine of 60 horse-power is required, the steam engine for pumping purposes possessing a third of that power. Both engines are laid down as well as the boilers, in duplicate, so that should an accident happen no delay in the traffic need take place. The roadway is laid with wood paving, and the sidewalks with green oak slip-pavement, excepting those portions on Gateshead Quay and Newcastle Quay sides.