Oxford Democrat. [volume] (Paris, Me.) 1833-1933, 1900-03-13
NAVIGATION.
HOW SHIPS FIND THEIR WAY ACROSS
THE TRAcKLEss OCEAN.

HOW Shifts FIND THEIR Wal ASuoSo
THE TRACKLEss OCEAN.
Any one who has ever been passen-
ger on great transatlantic liner OF to-
day knows what IN important imposing
parsonage ID the brass-bound skipper.
A very different creature Is he on the
deck Of his ship from the modest seafar-
Ing man we meet on land, clad for the
time being 10 his shore-going toys. But
the captains dignity 10 not oil brass but
tons aud gold braid. He has behind him
the powerful support OF deep, delight
full mystery. He 1t Is who takes the
sun" at noon, and finds out the ships
path ut sea. And, In truth, regarded
merely ~ . scientific experiment, the
guiding OF vessel across the unmarked,
trackless ocean has few equals within
the whole range of human knowledge.
II 10 the purpose Of this brief article to
explain the manner In which this seem
ing impossibllity Is accomplished. We
shall not be able to 60 sufficiently into
details to enable him who reads TO run
and navigate magnificent steamer. But
we hope to diminish somewhat that part
Of the captains vast dignity which de-
ponds upon his mysterious operations
with the sextant.
To begin, then, with the sextant itself.
IL Ia nothing but an instrument with
which we can measure how high up the
sun IL in the sky. Now, every one knows
that the sun slowly climbs the sky In
the morning, reaches Its greatest height
at noon, and then slowly sinks again In
the afternoon. The captain simply be-
gins to watch the sun through the SEX
tant shortly before noon, aud keeps at 1t
until he discovers that the sun Is just be-
ginning TO descend. That is the instant
OF noon on the ship. The captain quickly
Rlances at the chronometer, or calls out
moon" To an officer who Is near that
instrument. And so the error OF the
chronometer becomes known then and
there without any further astronomical
calculation whatever.
Incidentally, the captain also notes
with the sextznt how high the sun was
In the sky at noon. He has In his mys-
terious "cLxrt room" some printed AS
Economical tables, which tell him 10
what terrestrial latitude the sun will
have precisely that height on that par
ticular day of the year. Thus the ter
restrial latitude becomes known easily
enough, and II only the captain could
get his longitude, too, he would know
just where his ship Was that day at
noon.
We have seen that the sextant obser-
vstions furnish the error OF the chronom-
eter according to the ships time ut
noon. In other words, the captain IL In
possession OF the correct local time 10
the place where the ship actually is.
Now, II he also had the correct time at
that moment OF some well-known place
on shore, ne would know the difference
In time between that place on shore and
the ship. But every traveller by land or
sea Is aware that there are always differ
ences OF time between different places on
the earth. II watch be right on leav-
ing New York, for instance, II will be
much TOO fast on arriving ut Chicago or
San Francisco; the farther you go the
larger becomes the error OF your watch.
In fact, II you could find out how much
your watch had gone into error, you
would In a sense know how far east or
west you had travelled.
Now, the captains chronometer Is set
TO correct "Greenwich time" on shore
before the ship leaves port. His obser-
vations having then told him how much
this IL wrong on that particular day,
and In that particular spot where the
ship IL, he knows 1t once just how far
he has travelled east OF west from Green
wIch. In other words, he knows ''long-
itude from Greenwich for longitude is
nothing more than distance from Green
witch In an east and west direction, just
~ latitude IL only distance from the
equator measured In north and south
direction. Greenwich observatory Is
selected as the beginning OF things for
measuring longitudes, because that
worthy monarch, Charles III (who seems
to have done one wise thing, established
IL at date preceding the foundation OF
all other astronomical observstories.
One of the most interesting bits OF as
Economical history was enscted In con-
nection with this matter OF longitude.
From what has been said, II is clear that
the ships longitude will be obtained cor
rectly only II the chronometer has kept
exact time since the departure OF the
ship from port. Even very small error
of the chronOmeter will throw out the
longitude q good many miles, and We
can readily understand that II must be
difficult in the extreme TO construct
mechanical contrivance capable OF keep
ing exact time when subjected 10 the
rolling and pitching OF vessel at sea.
IL was as recently as the year 1896 that
the first instrument capable OF keeping
ANYTHING like accurate time At sea was
successfully completed. IL was the work
OF an English matchmaker named John
Harrison, and IL one OF the few great
improvements In matters scientific which
the world owes 10 desire for winning q
money prize. IL appears that 10 liza =
committee Was appointed by the house
OF commons, with no less . person than
Sir Isaac Newton himself Ne one OF the
members, To consider the desiraoility OF
offering governmental encouragement
for the invention Of some means of find-
ing the longitude az sea. Finally the
British government offered reward OF
60. coo for an instrument which would
find the longitude within sixty miles
SIS. 600. IL within forty miles, and $780,
600 II within thirty miles. Hsrrisop's
ehronometer Was finished In 1895, bat he
did rot receive the dual payment Of his
prize until l7ei
We have not space 10 enter Into m ac-
count Of the vexstioas delays and official
procedures 20 which he WAS forced 10
submit during those twenty-eight long
wears. IL IL q matter OF satisfaction that
Harrison lived 20 receive the money
which he hi so thoroughly earned. He
had the genius 20 plan and mister intri-
cate mechanical details, but perhaps he
lacked 10 some degree the ability Of
tongue and pen TO bring them home TO
others. This may be the reason he IL 80
little known, though Il was his fortune
10 contribute so large and essential =
part to the perfection Of modern nsviga-
ton. Let Us hope that this brief men,
ton NAV serve 10 recall his memory
from oblivion even for heeting mo-
ment; that we may not have written In
vain OF that longitude IN which his life
was giyen.-New York Evening Post.
HIS EXPERIENCE WITH SOUND
The man with the piece Of plaster