Omaha daily bee. (Omaha [Neb.]) 187?-1922, 1910-06-13
Things You Want to Know
The Naval
Observatory.

prevent wear. At its side there are two
delicately adjusted wheels. or circles. These
may be turned the smallest conceivable
fraction OF an inch, and while they are
about two feet in diameter, a Is necessary
10 have marks on the rims 90 fine that
they cannot be seen by the naked eye. Four
microscopes Of considerable power are used
to enable the observer TO see che hines in
the silver on the rims. and TO make sure
that the instrument Is exactly set.
In spite of the greatest exactitude that IL
Obtaanable In the mounting and operation
OF transit instrument there Il always a
remaining margin of error; but II happens
that this margin Of error has law OF
it's own. and that when the observations
are made 1t may be compensated for In the
computations To reduce error to a min
imum, however, the transit telescope Is
watched with great care. There are many
tests made to insure that It is always in
plumb. One OF these Is by the use OF an
artificial horizon. This consists of a pan
of quicksilver and tinfoil, which gives an
absolute level. The telescope is stationed
in a vertical position. and the observer
looks down through It into the pan Of
quicksilver. IL the threads IN the field
OF the telescope exactly coincide with their
images in the quicksilver & Is known that
the telescope is stlll in position.
When the observer wishes to fix the time
he takes the transit of about o'clock
stars. AS one looks through the transit
telescope he sees ten very fine lines across
the lens. and two others passing through
them at right angles. The instrument is
50 adjusted that the star which is to be
observed passes down through the field OF
the telescope between the two lines cross
ing the other lines as It goes. Each time
the star crosses one of these lines the OBJ
server presses the key OF a chronograph,
and the fact Is registered electrically. But
even here there is a margin OF error be-
cause OF the personal equation" One OBJ
server may press the key the thousandth
part of a second later than another OBJ
server. Allowances must be made in the
computations for the personal equation. In
some of the newer transit instruments
there is an attachment at the eye piece
not unlike the combination wheel to a safe
and by turning its wheels transits are re-
corded without the Intervention OF the per-
sonal equation. The drudgery OF the whole
procedure comes when the observer has to
make his computations from his observa-
lions. These involve mathematical ealcu-
lations Of vast proportions The spiders
thread Is the key to exact observations
with the transit telescope, and thus Il may
be said that the worlds time hangs by
the filmy thread of natures first weaver
The secret of all the observations at the
Naval observatory is the use of the infin-
isemal in the penetration of the infinite
One OF the rooms at the observatory
which is full of interest is the chronometer-
testing room. Here dozens of instruments
are gathered together and are watched for
a period of six months 50 as to make suro
that they are as nearly accurate as they
can be made when they are delivered to
the ships which reckon their position by
them. Every vessel in Uncle Sans navy
must carry at least three chronometers. II
they carried only one, there would be no
means of knowing when 1t went into error
II they carried only two they could not
know which was right and which was
wrong in case OF variation. In the testing
room 1t ds aimed to keep the temperature
as near to an approximation of sea condi-
ton ais may be. Wet clothes are hung up
around the room for this purpose.
The big twenty six-inch telescope, which
has the honor OF being housed I'm a dome
of its own, has some history attached TO
it. 1t was through this instrument that
Prof Asa Hill discovered the moon of
Mars Many other studies OF great interest
have been made through d. The instrument
was contracted for about the same time
that the reaper king. Mccormick, con-
tracted for his big telescope. At first
It seemed that the government would have
TO wait until his instrument was built be-
fore 1t would get it's telescope made But
Mccormick generously agreed to waive any
advantage the priority of his contract gave
him, and so they were built together.
One can scarcely realize the change that
has been wrought by the work OF the Naval
observatory. Before standard time was es-
tabhshed in the United States. there werO
no less than seventy different standards
With the railway and the telegraph. It
would be impossible for the country to do
business on the old-time basis To show
how 1t would work. the time cannon in
Paris affords an interesting illustration.
This little gun is fired every day at high
noon by the falling of the rays Of the sun
on a burning glass At different periods
OF the year. the time of this gun-fire
varies. At one period the man who set his
watch by IT might be fifteen minutes slower
than the train he wished TO take at the
Paris station.
ny FREDERIO ]. HAsxIN.
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