The other end of the bar has a lateral pin to
serve as a pivot for the end of a link F, its other
end being hinged to the upper end of a lever G,
which is pivoted to the post C, a short distance
below the hinged attachment of the link F, so
that the long end of the pointer which is constituted
by the lever G is below its pivot, and has,
therefore, a long range of movement.
A spring I between the upper end of the pointer
G and the other post B, serves to hold the pointer
at a zero position. A graduated scale plate J,
within range of the pointer will show at a glance
the pressure in pounds of the moving wind, and
for this purpose it would be convenient to make
the plane E exactly one foot square.
DETERMINING THE PRESSURE FROM THE SPEED.--
These two instruments can be made to check each
other and thus pretty accurately enable you to
determine the proper places to mark the pressure
indicator, as well as to make the wheels in the
anemometer the proper size to turn the pointer
in seconds when the wind is blowing at a certain
speed, say ten miles per hour.
Suppose the air pressure indicator has the scale
divided into quarter pound marks. This will
make it accurate enough for all purposes.
CALCULATING PRESSURES FROM SPEED.--The following
table will give the pressures from 5 to 100
miles per hour:
Velocity of wind in Pressure Velocity of wind in Pressure
miles per hour per sq.
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