To make a forecast, it is essential from what we have already written,
to know the direction of the wind, and to determine the direction we
must have a weather vane. It is real important that the vane should be
sensitive to the slightest movement of the wind and give actual wind
directions. At the same time it must possess the property of steadiness,
so that when it is set up it will be rigid.
Fig. 34 shows the standard weather vane used at all United States
Weather Bureau Stations and Fig. 35 shows the Gilbert Weather Vane.
Fig. 35. The Gilbert weather vane consists of a metal arrow pointer and
a metal rod eight inches long and five thirty-seconds of an inch in
diameter. The rod is fastened by means of a few staples to the side of a
pole, or whatever is to be used as a support for the vane. About three
inches from the top of the rod is a collar with set screw, which is
tightened, and the vane itself is then placed on the rod, the rod
passing through the small angles A and B, between the sides of the vane.
It will be found that the vane will swing freely on this support, and by
constructing two crosspieces with letters N, S, E, and W at each end of
the pieces, of course having N pointing directly north, the vane will
swing around and show the direction of the wind.
[Illustration:
Fig. 37
]
The standard United States Weather Bureau type hardly needs explanation,
as the illustration clearly shows all parts. It is the old, reliable,
standard iron, combined wind vane and anemometer support complete,
twenty feet high; iron contact box near base, improved roller bearings
for six-foot vane; latter, with electrical contacts shown enlarged at
the right. The vane is fastened securely to the roof of the building and
held in a perfectly vertical position.