[Illustration: FIG. 153.--Self-measuring gauge.]
Another Arrangement.--To simplify measurement, the receiver and tube may
be arranged as shown in Fig. 153. In this case the water is delivered
directly into the measure, and the rainfall may be read at a glance. On the
top of the support is a small platform for the receiver, its centre
directly over the tube. The graduations, first made on a rod as already
described, may be transferred, by means of a fine camel's hair brush and
white paint, to the tube itself. To draw off the water after taking a
reading, a hole should be burnt with a hot wire through the bottom cork.
This hole is plugged with a piece of slightly tapered brass rod, pushed in
till its top is flush with the upper surface of the cork.
If the tube has small capacity, provision should be made for catching the
overflow by inserting through the cork a small tube reaching to a
convenient height-say the 1-inch mark. The bottom of the tube projects into
a closed storage vessel. Note that the tube must be in position before the
graduation is determined, otherwise the readings will exaggerate the
rainfall.
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