The City and South London Railway (C&SLR) was the first deep-level underground "tube" railway in the world, and the first major railway to use electric traction. The railway was originally intended for cable-hauled trains, but owing to the bankruptcy of the cable contractor during construction, a system of electric traction using electric locomotives—an experimental technology at the time—was chosen instead. Given the small dimension of the tunnels as well as the difficulty of providing sufficient ventilation, steam power, as used on London's other underground railways, was not feasible for a deep tube railway. Like Greathead's earlier Tower Subway, the CL&SS was intended to be operated by cable haulage with a static engine pulling the cable through the tunnels at a steady speed. Section 5 of the 1884 Act specified that: