James Watt

The concept of Power was developed by James Watt for the purpose of advertising steam engines for pumping water out of tin mines in Cornwall in England.

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Horsepower

Watt had a friend estimate how much a horse could lift from a given depth in a day. He found that his engine would replace two horses (was two Horsepower). Watt's Horsepower is 746 Watts - a little more than the average horse can actually produce over a full working day.

 Manpower

A 'manpower' was defined by finding how much a glass polisher could do over a working day. The polisher pushed a pad backwards and forwards over the glass which was laid on a flat table. The pad was forced against the glass with a bent stick jammed up under the roof.

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