Year: 1871

The use of the word horsepower Is
very common, yet few, except good me-
chaflics and engineers, attach definite
meaning to it, but regarding it as indi-
eating loosely about the power one horse
would exert. 1t is, however, when
used in the sense under consideration, as
definite as possible, and means the pow
er required to lift thirty-three thousand
pounds avoirdupois one foot high in one
minute. A horse hitched to the end Of
q rope, over pulley one foot in dame
ter, placed ever deep well, travelling
at the rate Of two and a half miles per
hour, or two hundred and twenty feet
per minute, will draw up one hundred
and fifty pounds the same distance he
travels. The force thus eXerted is call
ed in mechanics, horsepower" it be-
ing an approximation to the average OF
strong horse. II we multiply the
weight raised Zone hundred and fifty
pounds) by the number Of feet it was
moved per minute, two hundred and
twenty, the product will be the number
o. pounds which the same power would
raise only one foot high in the same


length of time, (thirty-three thousand
pounds). The dynamometer is an in
strument made for measuring power,
particularly that exerted in drawing.
Those used in testing the draft Of agri-
cultural implements are simply very
strong balances, or spring steelyards,
graduated to indicate the power requir-
ed to raise any weight, within any reas-
enable limits, at the rate of two and q
half miles per hour. When we apply the
dynamometer in ascertaining the draft
of machines, II the index indicates one
hundred and fifty pounds, it is shown
that the horse Is required to draw just
as hard as he would do if raising one
hundred and fifty pounds out of q well
with q rope over apulley one foot in di-
ameter, at the rate Of two and q half
miles per hour, and so for other weights.
The velocity at which team moves is
to be considered, as well as the weight
to be raised, or the load 10 be drawn.
Ifs horse travels faster than two and a
half miles in an hour, while raising one
hundred and fifty pounds out Of q well,
he exerts moro than one-horse-power.
If he walks slower than this, he does not
exert force equal to one-horse power
In ascertsining the draught OF plow or
reaper and mower, by driving faster than
two and o half miles per hour, the dyna-
mometer will indicate more than the
correct draught; and by driving slower
the draught would appear to be less
than it really is. In testing the draught
Of machines q team should always
move at the rate of two and half miles
An hour, or two hundred and twenty
| feet per minute, which is tho universal
accepted rate with reference to which
dynamometers are graduated, and an
easy one to which an approximate II
driving with almost anyI kind of rate


MANY persons have supposed that three
hundred ACKNOWLEDGEMENTS
represented the same force that a team
would exert when dragging three hun
dred pounds along the ground. A horst
can haul six hundred pounds on tn


hard ground, with :ease; but he coul'


not draw hard enough on the dynamo


meter to mark more than two hundreI


and flfty, or three hundred pounds OK


cent fora few minutes. The power of


man is estimated at one-fitth that Of


horsepower. -t-s