Picture Number:10314092 Credit:Science Museum/Science & Society Picture Library
This steelyard balance is a direct copy of an example excavated from the Roman town of Pompeii in Italy. The settlement is famous for being buried in ash after the nearby volcano of Vesuvius erupted violently in AD 79. Working on the lever principle the steelyard operates by moving the counterweight (woman's head) along the beam until the item being weighed is horizontal and hence in equilibrium. The weight is determined by the position of the counterpoise thread against the lines and divisions marks on the balance beam.