El Paso herald. (El Paso, Tex.) 1901-1931, 1910-06-13
By
Frederic
]. HaSkin

! IheSe may be turned the smallest con-
! celVaDIe fraction of an inch, and while
! they are about Two feet in diameter
J IL IS necessary to have marks on the
rims so fine that they cannot be seen
/ by the naked eye. Four microscopes of
! considerable power are used to enable
1 the observer to see the lines in the sill
| yer on the rims, and 10 make sure that
/ the instrument is exactly set
Error Reduced to Minimum.
IN spite OF the greatest exactitude
that is ObtainabIe in the mounting
and operation of transit instrument
there is always remaining margin of
error; but il happens that this margin
OF error has a law of its own, and that
when the observations are made it may
be compensated for in the cOmputa-
tons
To reduce error to a minimum, how
ever, 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
pan of quicksilver and tinfOiI, 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. If the threads
in the field of the telescope exactly
coincide with their images in the quick
silver it is known that the telescope is
still in position.
Taking the Time.
When the observer wishes TO fix the
time he takes the transit of about five
clock stars As one looks through the
transit telescope he sees 10 very fine
lines across the lens, and two others
passing through them a right angles.
The instrument is so adjusted that the
star which is to be observed passes
r0rnr 4
between the two lines, crossing the
other lines as it goes.
Each time the star crosses one of
these lines the observer presses the
key of a chrOnOgraph, and the fact is
registered electrically. But even here
there is a margin of error because OF
the personal equation" One observer
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 cOmbina-
ton wheel TO a safe, and by turning its
wheels tranSits are recorded without
the Intervention of the personal equa-
tion- The drugery of the whole pro-
cedure comes when the observer has to
make his computations from his OBJ
servatiOns- These involve mathematical
calculations of vast proportions. The
spiders thread is the key to exact OBJ
servations with the transit telescope
and thus it 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 OBJ
servatory is the use of the infnitesimal
IN the penetration of the infinite
Ships. ChrOnOmeters Tested.
one OF the rooms at the observatory
which is full of interest is the chrome
meter teSting room Here dozens of in
struments are gathered together and
are watched for a period of six months,
so as to make sure 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 thermometers
If they carried only one there would
be no means of knowing when il went
into error. IF they carried only two.
hey could not know which was right
and which was wrong in case OF varia-
ton In the testing room it is aimed
TO keep the temperature as near 10 an
approximation of sea condition as may
be- Wet cloths are hung up around
the room for this purpose.
Historical Telescope.
The big 20 inch telescope, which has
the nOnOr OF being housed IN a dome
of its own, has some history attached
to it. 1t was through this instrument
that professor Asa Hill discovered the
moon of Mars. Many other studies Of
great interest have been made through
ii. The instrument was contracted for
about the same time that the reaper
king, Mccormick, contracted for his big
telescope. At first 1t seemed that the
government would have TO wait until
his instrument was built before it
would get its telescope made But Nc
COrmick generously agreed to waive
any advantage the priority of his con-
tract gave him, and so they were built
together.
that has been wrought by the work of
the Naval Observatory. Before stand
ard time was established in the United !
States, there were no less than 20 diff I
ferent standards. With the railway |
and the telegraph, it would be impos- |
sible for the country to do business on /
the old time basis.
To show how it would work, the time |
cannon in Paris affords an interesting !
This little gun is fired |
every day at high noon by the falling
of the rays of the sun on burning
glass. At different periods of the year,
the time of this gun-fire varies At !
one period the man who would set his
watch by it might be 10 minutes slow
er than the train he wished to take at /
the Paris station.
TOmOrrOw-Water for Thirsty Lands. /