The Red Cloud chief., 1896-06-05
VARIOUS KINDS OF TIME.
why the watch of IA Traveller Going West
seems TO hc Fast.

seems 10 lc Fast.
Turning upon its axis in the period
which we divide into twcnty-four
hours, the sun appears TO cross the
meridian Of each place on tho globe
once in that interval. The moment
at which it crosses tho meridian OF
any place j. termed local apparent
noon at that place. This would all
be very we'll if the earth and sun ro-
manned fixed in their relative posi-
tion>: or il the earth, completing as
1t does an annual revolution about the
sun. did 50 uniformly in u perfect cir
Gle and that circle were in the Same
plane with the motion Of daily rota-
ton. Then the successive intervals
between the meridian passages of the
sun at Greenwich would all be equal
and a perfect s~hronomcter set at Il
hours, . minutes, 0 seconds. when the
sun passes the meridian today, would
indicate precisely the same instant
for apparent neon every day.
But the oarth's path around the sun
is not a perfect circle; il is IN cllipsc.
and the motion in one portion of tho
ellipsc is more rapid than in another,
causing Il slight variation in the in
tcrvals between the solar passages.
Again. the plans of the carth's path
around the, elliptic. is inclined
%! degrees TO the plane of the ouua-
tor. in which the daily rotation tales
place and consequently twice "A wear
the intervals OF apparent noon" are
each about twenty seconds greater
and tw.ce "A year about twenty seconds
less than twcnty-fo ur hours. TO cy-
plain just why this result would re.
quirc more OF AN investigation into
Astronomical principles than is hero
contemplated, but it is so ncycrthe,
less and any text book will clucidatc
The rcasons a combination o. tho
two effects causes the sun apparently
10 slow fourteen minutes in Novem.
Der: But in the curse Of II year tho
average il preserved, and therefore a
mean solar day OF exactly twenty
o N hours is adopted in the ~almanacs
and is used for all purposes. This
accounts for the differences b,,wcen
mean time and sun time. A regulator
keeps the former; Il sun dial indicates
the latter.
few years ago every large city in
the tnited States had its W local
time, says the san Francisco Exam
liner and this was for each plrce the
true mean solar time obtained "a
above indicated. Consequently, n man
travelling westward from Washington
would find his watch fast as follows:
Al chicago " minutes; az Omaha
] hour. II minutes: at Denver. | hour
~ minutes; at Salt Lake City, 2 hours,
20 minutes. and finally mt San Francis.
co ) hours > minutes. ID will readilv
be recalled how much a%nnoyan both
To trainmen and travellers was occn.
stoned by all these various corrections
Within the last decade II great reform
was inaugurated. To-day a traveller
going westward finds his watch fast
from time II time, but only the hour
hand Is in error. Tho hour is changed
for each fifteen degrees of lonpi,ula.
Washington time is five hours slow of
Greenwich; Chicago six hours. Dem
vor, seven hours; and san Francisco,
eight hours, All the intermediate
cities and towns are run on one sys.
tom or the other, according 90 their
location in latitude the standard be.
Ing Eastern. Central, mountain oni
Pacific time. All tho timc-pieccs on
the coast are set by Pacific standard
time, which is eight hours Slow of
Greenwich moan time, Therefore n
watch which is set at San Francisco
solar time by means Of a corrected
sun dial is still . minutes f. cconds
slower than Il Pacific standard timo
because we are that much in longitude
west OF the l2oth meridian. which
forms the eastern boundary OF North.
ern California, and on which only is
the Pacific time coincisent with
local mean time"