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.

http://www.spartacus.

Horsepower

Watt had a friend estimate how much a horse could lift from a given depth in a day. From this he ascertained that his engine would replace two horses - ie. was two Horsepower. In modern terms Watt's Horsepower is 746 Watts - a little more than the average horse can actually produce over a full working day.

.

Manpower

At around the same time a 'manpower' was defined by finding how much 'work' a glass polisher could do in a day. Polishers forced a pad backwards and forwards over the glass, laid on a flat table. The pad was pushed against the glass with a bent stick jammed up under the roof. The unit did not come into common use.

Next