How twisted strands are stronger than separate, & development of iron cable for use in coal mines, from 8 mins:
www.bbc.co.uk
The Secret Genius of Modern Life - Series 2: 6. Lift
Hannah goes behind the scenes to look at the technology behind the lift, entering a 246m high lift shaft to test everything from the brakes to her own fear of heights.
www.bbc.co.uk
