Evening star., 1901-11-15
TIME FROM STARS

Continued from Seventeenth Page)
else." facetiously remarked Mr.. NJ e. Por-
| ter who is employed at the naval obser-
| vatory as computer in connection with the
| time service.
One observer will wait to push the button
| until he sees the line fully bisecting the
| spark. Then-so the psychologist tells us
| the impression on the eye must be con-
yeyed to the BRAIN The brain in turn, re-
| ceiving from the eye the Information that
| the star has arrived, judges that it is now
| time the key were pressed, and sends
message through the nerves OF the arm TO
| tho finger, commanding the latter to do the
| work, whereupon the finger gets its mus
/ cles into action and proceeds TO obey. And
| so II is not difficult to understand, from
| the PSYCHOLOGISTS very explanation of the
| mental process involved how that by this
| time the star has passed on somewhere
| else"
Another seeing the tiny sun approaching.
| thinks He will be there by the time i can
| press this button" Click" goes the key.
while the little stellar traveller Is still this
| side the line.
But the same observer will press too late
one time and too early the next; he does
| one or the other with approximate uniform
| ity. 1t Is a part Of his personal tempera-
| ment-a factor In the makeup of the man.
Mr.. Porter records the stars passage 10
| OF a second after the event has actually oc-
CURED. 1t has gone by .07 of a second
| before Prof Skinner OF the naval observa-
tory notes IT on the chronograph. Prof.
| Harkness, on the other hand, when he used
to observe meridian transits before his re-
tirement, would press the key IL Of a sec
ond before the celestial pilgrim came to the
crossing.
| Astronomy does not care whether an OBJ
server be exactly correct, or slow. or fast;
| it only wishes to know which and how
much. To determine this a simple mechan
ism causes an artificial star to pass before
| a small transit instrument, each passage
| automatically registering Itself on the
chronograph. The observer also records
these transits. and the average time be-
tween the key pressures thus made by him
and the automatic records Of the artificial
star constitutes his personal equation. II
he be found TO press the key too late, that
much Is subtracted from the readings of
the chronograph whenever he makes OBJ
| servation; If he press too early. 1t is added.
Accurate to a Hair-Breadth.
Nor will the punctillious star-gazer sat
isfy himself as to the exact moment when
Gamma Taur crossed the meridian until
| another factor Of possible error has been
accounted for. Atmospheric changes or the
| imperceptible heavings OF the earth may
have slightly altered the level Of the transit
| instrument. Or else the open window
yonder may have brought draft through
this slae OF the room, and the marble pier
| may have thus become somewhat cooler.
and consequently least bit shorter than
| the other. Should the east pier be thus
cooled and contracted, the telescope would
| lean toward the east, and the star would
! be seen before the true time; il the west
pier, the observation would be a little too
late.
Accordingly. after the star passages have
| been recorded, the observer turns the in
| Strument large end downward and mounts
a step-ladder. He is now looking through
| the telescope into q basin of quicksilver
| perfect mirror provided mother earth is
not for some reason restless tonight and
provided the electric cars. a quarter Of
mile away, are not running too recklessly
| down the hill. Looking closely. he sees
| eleven perpendicular spider lines-he sees
more than that; should he count them, he
would find just twenty-five. Half the
| number lie close each to another, and are
| less distinct. They are the images of the real
| lines reflected from the mercury mirror,
| and prove that the instrument is a little
| the images are reflected back directly
| against the lines themselves and therefore
cannot be seen at adj. The little distance
between the lines and their respective
and the observations are corrected so as
| to rectffy the error arising from this dis
turbance.
Delivering Time to the People.
At some convenient interval between the
| first and the last star observations each OF
| the two other astronomical clocks at the
observatory, whose business II is to help
| the sideriaI to keep time during long spells
| Of cloudy weather, Is switched into the
| chronograph with the siderial clock The
| chronograph Is now making two saw teeth
| to the second. one for each clock. So that
when the error OF the siderial clock has
been ascertained these joint chronograph
| records make it an easy matter to find
the errors Of the other clocks also
These clocks are seldom actually cor
rected by resetting; not until they are as
| much as a minute wrong For them to be
minute OF OF the true time Is considered
insufferable, and that much error does NOT
accumulate in a well-regulated astronom-
1cal clock oftener than two or three times
year. But from day to day when obser-
vations are made 1t Is usually sufficient Just
| to note how much too fast or slow each
clock is.
The standard transmitting clock, how
ever. Is corrected daily. About half-past
IL am. its pendulum beats are turned into
the chronograph with those Of one of the
others. Today, for instance, the chreno-
graph sheet shows that this clock sounds
it's ticks one-third OF a second too soon
The ball OF the pendulum is given a re-
tarding touch on its downward swing The
error Is lessened, though not eliminated.
Another touch in front Of the pendulum and
the chronograph writes the saw tooth on
the sheet Just where 1t ought to be writ
ten. The great time standard is now tick
ing in harmony with the stars all ready for
its high duty few minutes hence Of tell
ing three nations the time OF day auto
matically.
Moreover. the ticks that are ticked over
the telegraph wires throughout the CONT
nent are also licked onto the chronograph
and become part OF the official records of
the government. And II ever a lawsuit or
other important matter could hinge on the
question whether on a certain day the cleo
III fpry,r fta4 ~<,k
clocks was sent out exactly on the dot at
noon, or whether it was sent a fifth of a
second early or late. the necessary evidence
to establish the point could be found In the
archives of the naval observatory.
How They Met.
From the Youths Companion.
Bennet Burleigh the English war corre-
spondent. II authority for the following
strange story: One day last autumn two