Evening star. [volume] (Washington, D.C.) 1854-1972, 1911-04-02
Power of a Man

MI scientific trend and were regarding
A'A with admiration one of the great en-
gines and generators in the metropolitan
power station.
"How many horsepower" l asked, yoic-
ing the question that comes naturally to
everyone at sight of an engine.
II should say five thousand he replied;
"but we can get better idea of it from the
capacity of the generator. Just glance at
that brass plate near you on the frame of the
dynamo"
Eighteen hundred amperes; two thou
sand volts" read, wondering what hat had
to do with horsepower.
1.-THE capacity of dynamo" continued
my friend, almost reading my thoughts, lis
given by the product of the amperes and the
volts, and is measured in terms of a unit
called the watt, or more generally in terms
of unit one thousand times larger, or the
kilowatt. The capacity of this machine is
three million six hundred thousand watts,
then, or thirty-six hundred kilowattS. Or,
as the kilowatt is one and one-third times as
large as the horsepower, this would make
some forty-eight hundred horsepower. Since
the engine that drives it is generally little
larger than absolutely necessary, its horse
power in this case will probably run between
five thousand and six thousand
What is a horsepower, anyway" l
asked. Il have used the term often
enough; but have never known just what it
meant"
This unit of power" he obligngly went
on to explain, "is, as its name indicates,
about the power that can be steadily fur
nished by good sized horse. More exactly,
it is defined as rate of doing work equal to
thirty-three thousand foot pounds minute,
or five hundred and fifty second. A foot
pound is the work done in lifting a pound
one foot high; so a horsepower engine could,
for example. lift one pound five hundred and
fifty feet high in one second, or ffty-fve
pounds ten feet high"
what would be the power of a man,
them" asked.
at is difficult to say. For steady work
it might not average much more than
tenth of a horsepower; but, strange as it
may seem, for short spurts man can do
more than horsepower. Thus, one hun
dred and fifty-pound man can run up stairs
for a few seconds at a rate of four feet verti-
cally second, or even more, and this would
mean six hundred foot pounds second, or
we'll over horsepower. If he was able at
the same time to make use of his arms, he
could probably increase this by half
But this must not be interpreted" he
went on to say, as meaning that man is
as strong as horse; for, just as a man can
exceed his normal power for short spurts,
so horse could generate several horsepower
for few minutes at time. So it is prob
able that an excited runaway team is nearly
if not quite the equal in power to a fair sized
automobile with its twenty rated horse
power" L. I. Rose
Human Sensitiveneas
EXPERIMENTS by Berthelot show that
- the nerves of smell are so sensitive that
the odor of iodoform can be recognized in
quantities as small as one hundred billionth
of gram. In such case the odor was
distinct, although hundreds of years would
be required for the substance to lose thou
sandth part of its weight.
This indicates that the delicacy of the
nerves of smell in detecting the presence of
minute quantities of emanations is of the
same order as that of the spectroscope, and
for this reason Berthelot has called attention
| to the risk of inferring from spectroscopic
examination of the change from one element
into another. The spectral lines of one ele-
ment might appear in the spectrum of an
other, owing to the presence of an infnitesi-
NAL impurity.
Sapience Wonderful