SHEILA TERRY / SCIENCE PHOTO LIBRARY SHEILA TERRY / SCIENCE PHOTO LIBRARY
Steelyard balance. This instrument was used to weigh sacks of grain and animal carcasses. It works on the principle of the lever, having a counterbalance (centre) which slides along a calibrated arm away from the fulcrum (left). The steelyard was invented independently by both the Chinese and Romans around 200 BC. This one dates from the 19th century.
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