A Treatise on Meteorological Instruments: Explanatory of Their Scientific Principles, Method of Construction, and Practical UtilityNegretti, Enrico Angelo Lodovico
Science
A Treatise on Meteorological Instruments: Explanatory of Their Scientific Principles, Method of Construction, and Practical Utility
Negretti, Enrico Angelo Lodovico
Meteorological instruments; Meteorology; Scientific apparatus and instruments
=110. Howard's Rain-Gauge.=--It consists of a copper funnel, a stout glass
or stone bottle, and a measuring glass. The bottle is to be placed upon
the ground, with the funnel resting on its neck. A brass band or cylinder
fixed upon the outer surface of the funnel envelops the neck of the
bottle, and the pipe of the funnel extends nearly to the bottom of the
bottle; so that loss by evaporation is avoided as much as possible. The
receiving space of the funnel is formed by a brass ring, five inches in
diameter, very accurately turned. The measuring vessel enables the
observer to note the rainfall in inches, tenths, and hundredths of an
inch.
[Illustration: Fig. 84.]
=111. Glaisher's Rain-Gauge.=--The rain-gauge designed by Mr. Glaisher,
the well-known meteorologist, and used by most observers of the present
day, is arranged for the reception of the water which falls upon its
receiving surface only, and for the prevention of loss by evaporation. The
rain is first collected in a funnel, _B_, (fig. 84,) the receiving surface
of which is turned in a lathe. The conical surface of the funnel slopes to
the pipe, _E_, at an angle of 60 deg. from the horizontal receiving surface.
The tube, _E_, is of small aperture, and is bent up, in order to retain
the last few drops of rain, so that the only opening for the escape of
vapour may be closed as long as possible. The funnel, _B_, fits upon the
cylinder, _A_, tightly in the groove, _D_. A copper can is placed inside
the cylinder, _A_, to receive the rain from the funnel. Once or twice a
day, or after a shower, this can should be taken out, and the water
measured in the glass measure, _C_, which is graduated to hundredths of an
inch, according to the calculated quantity of water, determined by the
area of the receiving space. In use, this gauge should be partly sunk in
the ground, so that the top may be about five inches above it. Thus
situated, there will be little or no evaporation from it during any month
of the year; and the readings need not be taken daily, although desirable.
=112. Rain-Gauge with Float.=--In this construction the graduated glass
measure is dispensed with. The cylinder of the gauge is made less in
diameter than the funnel, and a hollow, very flattened spheroid of copper
forming a float, and carrying a vertical graduated boxwood scale which
moves through the orifice of the funnel, is placed in it. As the rain
accumulates the float rises, and the amount of rain in the gauge is read
upon the scale from the top of the gauge, a bar, having a hole at the
centre for the passage of the scale, being fixed diametrically across the
receiving space of the funnel. The gauge is provided at the bottom with a
brass cock, by which the water may be allowed to flow out of it whenever
necessary.
This form of gauge is not very suitable for the measurement of small
quantities; but is admirably adapted for localities where the rainfall is
excessive.
[Illustration: Fig. 85.]
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