Make a central hole in the bottom of
the receiver large enough to allow the funnel to pass through up to the
swell, and solder the rim of the funnel to the inside of the receiver,
using as little heat as possible.
If you select a tin of the self-opening kind, you must now cut away the top
with a file or hack-saw, being very careful not to bend the metal, as
distortion, by altering the area of the upper end of the tin, will render
the gauge inaccurate.
The receiver should be supported by another tin of somewhat smaller
diameter, and deep enough to contain a bottle which will hold 3 or 4 inches
of rainfall. In order to prevent water entering this compartment, tie a
strip of rubber (cut out of an old cycle air tube) or other material round
the receiver, and projecting half an inch beyond the bottom (Fig. 152).
All tinned iron surfaces should be given a couple of thin coats or paint.
The standard distance between the rain gauge and the ground is one foot.
The amount caught decreases with increase of elevation, owing to the
greater effect of the wind. The top of the gauge must be perfectly level,
so that it may offer the same catchment area to rain from whatever
direction it may come.
Pages:
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272