Stephenson had large wrought-iron boiler plates available and he also had the courage of his calculations... The idea found its best-known expression in the Menai railway bridge opened in 1850. Stephenson's beams, which weighed 1,500 tons each, were built beside the Straits and were floated into position between the towers on rafts across a swirling tide. They were raised rather over a hundred feet up the towers by successive lifts with primitive hydraulic jacks. All this was not done without both apprehension and adventure; they were giants on the earth in those days.