I tried sending something on these lines yesterday, but the copy I received
seemed to have encountered some computer glitch and arrived garbled and
unreadable, so here is another attempt:
I am not sure if this is entirely relevant, but may be related to Rick's
query re the "duty of an engine".
In a book I possess called "Practical Tunnelling" by Frederick Walter Simms,
published in 1844, he describes the driving of tunnels on one section of the
railway line from London to Folkestone, driven from numerous shafts along
the projected line, up which rock and water (more water than rock, he
comments) were hoisted using horse whims.
He decided that this contract would be a good time to check on the
performance of horses - the conclusion being that a horse could just about
work at the rate of one horse-power, but if it did, it tended to drop dead
at the end of the shift, a fact unpopular with the contractor supplying the
horses.
Simms mentions in his book that he had, in 1843, published a paper on his
results to the Institution of Civil Engineers. One day I went to their head
office and asked the librarian if I could look at their proceedings for 1843
and she kindly got the book down for me from the topmost shelf.
There, sure enough, was Simms' paper "Upon the Measurement of Horsepower"
and details of the ensuing discussion. One of those who made comments said
that one had to bear in mind that when Mr Watt defined a horsepower as
33,000 foot-pounds per minute (a figure I was taught in school in the 1940's
and still clearly remember!) he was in the business of selling steam
engines. Mr Watt, the speaker pointed out, sold his engines on a
"satisfaction or your money back" guarantee. "Being a Scotsman" the speaker
continued, "he wanted to make sure he never had to give the money back, so
he defined a horsepower at a level somewhat above what an ordinary horse
could do". This being so, when he sold an engine and quoted its strength in
horse-power, the new owner was pleased to find it could actually do more
work than the equivalent number of horses.
Tony Brewis
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