[Illustration: FIG. 154.--Gauge in case.]
Protection against the Weather.--A rain-gauge of this kind requires
protection against frost, as the freezing of the water would burst the
tube. It will be sufficient to hinge to the front of the support a piece of
wood half an inch thicker than the diameter of the tube, grooved out so as
to fit the tube when shut round it (Fig 154).
XXVIII. WIND VANES WITH DIALS.
It is difficult to tell from a distance in which direction the arrow of a
wind vane points when the arrow lies obliquely to the spectator, or points
directly towards or away from him. In the case of a vane set up in some
position where it will be plainly visible from the house, this difficulty
is overcome by making the wind vane operate an arrow moving round a
vertical dial set square to the point of observation. Figs. 155 to 157 are
sketches and diagrams of an apparatus which does the work very
satisfactorily. The vane is attached to the upper end of a long rod,
revolving freely in brackets attached to the side of a pole. The bottom end
of the rod is pointed to engage with a nick in a bearer, in which it moves
with but little friction.
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