Wauwatosa news. [volume] (Wauwatosa, Wis.) 1900-1948, 1904-07-09
MEASURING PRESSURE OF WIND.
Unique Apparatus on the Eiffel Tower
Shows the Resistance of the Air.

Some very interesting experiments
upon the resistance of the air have been
recently made by NJ. e. Eifel at the
tower which bears his name, by means OF
an apparatus of his invention which may
be daily seen in operation when the air
Is; calm. At Il given signal a cylinder
carried by IL double spring falls with
great velocity from the second floor of
the tower THAT is to say. from Il height
OF about 80 feetl, along Il vertical cable.
and then progressively slows mp. AMI
stops without any shock at 3.2S feet from
the ground, remaining attached to the
cable. This cylinder, Il part of WHICH is
conical. carries in front Il plate which is
thrust backward by the pressure of the
wind during the fail. Such displacc-
ments compress an accurately tared
spring which measures the pressure and
lnScrlbeS 1t upon registering drum. the
revolution of which is regulated by the
fall itself The ordinary inscribing style
Is replaced by tuning fork that makes
q hundred vibrations Il second. When
the apparatus is opened there is, there
fore found inscribed upon the drum an
undulating curve that gives for every
point the height of fall. the pressure
acting at this moment, and the velocity,
within an approximation of hundredth
of second. This is the first time that
one and the same apparatus has contn-
ually Indicated these various results from
the zero velocity to that of 1870 feet q
second, which is that of the most violent
winds.
As the pressure device may be of any
form and size whatever (a normal or
oDllque plane, cone, sphere or cylinder.
ihe apparatus is capa BILE of giving more
accurate results than have hitherto been
obtained i'll experiments on the resistance
that the air offers to a moving body. and
which IS nothing else than the pressure
of the wind upon Il stationary body.
Such determination presents great
practical interest either as regards the
utilization of the pressure of the wind rs
a motor or the resisting of it, as becomes
necessary in the practice of the prOfeS-
Si0n of the engineer and in experiments
with dirigible balloons
In order to complete the description OF
the apparatus the principle of which has
Just been indicated it sutices to add that
in order to diminish the effect of the We
locity of this mass of 20 pounds moving
at the rate of 100 feet a second. say
nearly ninety miles an hour, the frame Of
the apparatus is carried by very power
full double spring, which slides freely
along the cable as far as to within sixty
five feet of the ground. at which point
the diameter of the cable progressively
widens and the double spring also is
forced to widen. and then exerts II pres
sure upon the cable, and through its fric-
ton gradually diminishes the velocity.
The experiments have shown that the
pressure of the wind is notably less than
that admitted up 10 the present. After
they have been finished this question,
which has hitherto been very uncertain.
will have made an important progress
and have demonstrated once again the
services that the Eiffel tower is capable
of rendering to science Scientific Amcri-
can.