The pneumatic pressure was designed to be in a diameter tube, with the engine at the Waterloo end both sucking and blowing 25-seat carriages, which acted as pistons within the tube.
Edmund Wragge served as the resident engineer. The railway was intended to cross the River Thames through a tunnel composed of four prefabricated tube sections, each long, laid in a trench dredged across the riverbed. These sections were to be joined by inserting their ends into junction chambers constructed within brick piers below the existing riverbed. The piers were also designed to bear the weight of the sections, which were made of three-quarter-inch boiler plate, encased by four rings of brickwork, firmly secured with cement and flanged rings riveted to the metal. Each section, at least one of which was completed, weighed nearly 1,000 tons. Prefabrication began at the
Samuda Brothers shipyard in
Poplar, five miles downstream. If completed, this railway would have been the first underground railway of its kind. ==Decline and abandonment==