Compound levers, c 1750.
© Science Museum / Science & Society Picture Library
This device in the foreground was made by George Adams, instrument maker to the king. A lever, one of the 'simple machines' known since antiquity, enables a heavier load to be lifted using a lighter one. This machine uses a series of three levers so that the weight to be lifted can be sixty times greater than the 'power' required to lift it. The rear instrument is another example of a compound lever, which belonged to Dr Stephen Demainbray (1710-1782), a scientific lecturer of the 18th century.