The Salt Lake herald. [volume] (Salt Lake City [Utah]) 1870-1909, 1899-08-31

graph. We shall give a brief account
of the methods now in use in New York
! City. and these may be taken as essen
TALLY representative of those employed
elsewhere.
Every day noon precisely an electric
signal is sent out by the United States
naval observatory in Washington. This
signal is regulated by the standard
clock of the observatory, of course tax
ing account of star observations made
on the next preceding fine night. This
signal is received in the central New
York Office of the telegraph company.
where il is used to keep correct very
fine clock, which may be called the time
standard of the telegraph company.
This clock in turn has automatic cleo
trio connections, by means of which 1t
is made to send out signals over what
are called time wires that go all over
the city. jewelers. and others who de-
sire correct time can arrange to have
small electric sounder in their offices
connected with the time wires. Thus
the clicks of the standard telegraph
company's standard clocks are repeat
ed automatically in the jewelers. shop
and used for controlling the exactness
of his regulator. This. in brief, is the
method by which the astronomers
careful determination of correct time is
transformed and distributed to the peo-
pie at large.
Having thus outlined the manner of
obtaining and distributing correct time.
we shall now consider the question OF
time differences between different
places on the earth. This is matter
which many persons find most perplex-
ing, and yet ii is essentially quite SIM
pie in principle. Travellers are of course
we'll acquainted with the fact that their
watches often need to- be reset when
they arrive at their destination. Yet
few ever stop to ask the cause. Let
us consider for a moment our meta
DDS of measuring time. We go by the
SUM- If we leave out of account some
small irregularities of the suns mo-
ton that are of no consequence Tor
our present purpose we may lay down
this fundamental principle: When the
sun reaches it's highest position in the
sky il is u o'clock, or noon. FOR the
sun. as we know, rises each morning
in the east, slowly goes up higher and
higher in the sky, and at last begins to
descend again toward the west. But
it is clear that as the sun travels from
east to west il must pass over the
eastern one of any two cities sooner
than the western one. When IL reaches
its greatest height over western city
it has therefore already passed It's
greatest height over an eastern one.
In other words, when it is noon, or u
O'Clock. in the western city it. is al
ready afternoon in the eastern city.
This is the simple and evident cause OF
time differences in different parts OF
the country. OF any two places the
eastern one always has later time than
the western. When we consider the
matter in this way there is not the
slightest difficulty in understanding
how time differences arise. They WILL
of course. be greatest for places that
are very far apart in an east and west
direction. And this brings US again to
the subject of longitude, which, as we
have already said, plays an important
mart in all questions relating 10 tlIne.
For longitude is used to measure the
distance in an east ana west uireclluh
between different parts OF the eartn
If we consider the earth as large ball
we can imagine a series of great CIR
cles drawn on it's surface and passing
directly from the south pole 10 the
north pole. Such a circle could be
drawn through any point on the earth.
If we imagine pair OF them Drawn
through two cities. such as New iork
and London. the longitude difference OF
these two cities is defined as the angle
AT the pole between the two great
circles in question. The size OF TINS
angle can be expressed in degrees. III
We then wish to know the difference IN
time between New York and London IN
hours we need only divide their iongi-
tude difference in degrees by the num-
Der Is. In just this way we can get
the time difference of any two places.
We can measure the longitude diner
ence on a map, and then divide by 10
to get the time difference.
These time differences can sometimes
become quite large. Indeed. for two
places differing $50 degrees in longitude,
the time difference will evidently be no
less than twelve hours. Most of the
civilized nations have agreed informally
TO adopt some one city as the funda-
mental point from which all longitudes
are to be counted. Up to the present
we have considered only longitude diff
ferences. When we speak of the longi-
tude of any city we mean its longitude
difference from the place chosen by
common consent IS the origin for meas
uring longitudes. The town almost
universally used for this purpose is
Greenwich. near London, in England
Here is situated the British royal OBJ
5ervatory,- one of the oldest and most
important institutions of it's kind in the
world. The great longitude circle pass |
ing through the center of the astro-