Re: Horsepower (was Re: Metric Time (was Re: Why not 13 months? (Was

Simon Mitchell (
Tue, 17 Oct 1995 19:40:56 GMT (I Johnston) wrote:

>Jacques Guy ( wrote:
>: Much later, I read (I think it was in New Scientist), that
>: a horse has a power closer to 12hp, early automotive
>: manufacturers having deliberately grossly underrated a
>: horse's strength to sell their wares.
>A confusion between two distinct fiddles:
>1) The power of a horse was originally measured by James Watt as 22,000 foot
> pounds per hour. However, he defined the horsepower as 33,000 so that
> mine owners who bought a 4hp steam engine (say) would be impressed at
> how easily it did the work of four horses. Thus was the horsepower
> overestimated.
The term horsepower comes from the ability of a strong horse to haul a
150 lb bag of coal straight up a shaft, four feet in one second. This
was observed by James Watt.