The Indianapolis journal. [volume] (Indianapolis [Ind.]) 1867-1904, 1896-01-12
MEASURING SUNSHINE,
One OF the Interesting Duties of the
Weather Prophets.
Boston Globe.


Boston Globe.
Within the past few years the develop
ment CT the great signal stations situated
at points the Pacific or Atlantic coasts
and in the interior of this country, ana all
under the direction or the United states
Government Weather Bureau at Washing
ton, has been something phenomenal. Inc
increased interest Of the people IN the sell
ence of meteorology has gone great Way
In stimulating the weather observers at the
principal stations TO the devising of more
perfect instruments for indicating and re-
cording atmospheric conditions.
There is scarcely an hour OF the day when
the conditions Of the weather are not
changing. although this statement might,
So frequent and radical are these changes
that the advanced meteorolog>st can no
longer depend simply upon EYE obserya-
ton" and it is absolutely necessary in the
performance of his duty that he be provld-
ed with the most recently improved instru-
ments.
The progress in the perfection of these
delicate pieces OF mechanism has been so
great that the observers in the tower or the
federal building where the Boston station
OF the Weather Bureau is situated, are now
II is true. Not a day passes that the
amount, in hours minutes and seconds, OF
sunshine that has cheered the Hub is not
teiegraphed to Washington, and from there
across the continent to all the principal sta
tions. Away up on the very topnost part
OF the high tower on a bracket by Itself is
this delicate little instrument, ana so uiCeAy
is it adjusted that though day may be dark
and lowering clouds hover DER 1t let but
one tiny rift in their gloomy banks allow
the imprisoned sun rays to slip out put ,i tor
machine has its tape ready and record
is made OF "Old Soils solitary smile that
day.
Not only does it catch the amount, but.
through the help OF electricity. sends the
record buZzing down a wire into the main
office on the top floor OF the building and
puts Ii In figures that can't lie upon sheet
of paper.
The principle upon which this bit of deli
cate mechanism operates is essentially tnat
OF the Leslie differential air thermometer
in the form of a straight glass tube with
cylindrical bulbs at each end; the whole In
closed in projecting glass sheath; Mer-
curry Is used TO separate the air In the two
bulbs, a small quantity being inserted in
the bottom and stem OF the lower bulb,
which bulb Is smoothly coated on the out
side with ampblask, The .,s6 bulbs are nlled
ture OF about five degrees Fahrenheit, to
secure greater density of air.
tecting sheath is then perfectly exhausted
of air and is also sealed. In operation the
glass instrument is mounted on an adjust
able metallic base; to which It Is firmly at
are attached to electric wires connected
with the recording instrument in the office
and the recorder itself Is placed In suit
able location on the tower, where 1t has
free exposure to the sun at all seasons OF
the year and at all hours Of the day.
As already stated the principle upon
which this instrument works is essentially
that of a differential air thermometer; the
air in each bulb being separated by short
column of mercury. The lower bulb is COW
cred with a heavy coating OF lampblack,
and, when the instrument is exposed to the
direct rays of sunlight the air in this bulb
expands more than that in the upper bulb,
which has no coating OF lampblack any
substance to attract the heat rays and the
column of mercury is forced upward and
closes an electrical circuit through the
fused-in wires.
This circuit passes through the wire to
the registers and when the sun is shining
short marks at regular intervals are made
on the record sheet. During cloudy weather
toward the blackened bulb and breaks the
circuit, and the record on the sheet is
then straight line.
The idea of measuring and recording sun
shine electrically was first suggested by ID.
T. Maring. OF the United States Weather
Bureau. and afterward ii was developed by
Prof. c. F. Marvin into the simple and in
genious instrument described.
AS a matter of further explanation II. is
we'll to state that the register upon which
the record Is kept Is bass cylinder con-
nected with a clock works, and over this
cylinder a sheet of paper, upon which are
ruled lines. marked with the hours and min
utes OF the day, is placed. An automatic
pen connected with the sunshine recorder
by fine electrical wire marks the results
upon the paper as the cylinder is turned by
the clock
This record is removed at the close OF
each day. and the weather clerk enters il In
his book after telegraphing 1t to the main
Office at Washington, ID. c.
Not content with this achievement Pro-
fessor Marvin has designed still another
which is in operation at the first order sta
tons OF the service. II is known the
Photographic sunshine recorder"