Virginian-pilot. (Norfolk, Va.) 1898-1911, 1900-03-22
SEA NAVIGATION
How Ships Find Their Way Across
the Trackless Ocean.
Tho Captain and His scxtant John IInrri-
son and the Important Invention OF tho
Chronometcr.
(New York Evening Post.)


to-day knows that an important. i'm
posing parsonage is the brass bound
skipper. q very different creature is
he on the deck of his ship from the
modest scattering man we meet on land,
clad for the time being In his shore
going toys. But the captains dignity
Is not all brass buttons and gold braid.
lie has behind him the powerful sup
port OF deep, delightful mystery. He
1t is who takes the sun" ut noon, and
iinds out the ships path at sea. And,
experiment, the guiding of vessel
across the unmarked, trackless ocean
mas lew equals within the whole range
OIL human knowledge. 1t is the purpose
oil this brief article to explain the man
ner i'll which this seeming ilnpossibilitv
Is accomplished. We shall not be able
10 go sufficiently into details to enable
MN VINO reads to run and navigate n
magnificent steamer. But we hone to-
diminish somewhat that part of the
captains vast dignity which depends
upon his mysterious operations with
the scXtant.
10 begin. then. with the scxtant it,
self. 1t is nothing but an Instrument
Win winch we can measure how hiuh
up the sun Is in the sky. Now. every
one knows that the sun slowly climbs
tne SKY IN the morning. reaches its
slowly sinks again In tho afternoon.
Inc captain simply begins TO watch the
sun through the seXtant shortly before
uooI. ana Keeps at 1t until he discovers
mat the sun is just beginning to de-
scelu. Ihat is the instant of noon on
o"e snip. Inc captain quickly chances
"t the cnronometer, or calls out ''nnon',
10 an officer who is near that fnstr,,-
mcnt. And so the error OF the chrono.
meter becomes known then ana thrro
without any further astronomical cal
ulations whatever.
viii, Nc , me captain also notes
WIN inc seXtant how hish the SIM ,vas
IN inc SKY at noon. He has in his mvete~
IlouS cnart room some printed as
economical tables. which tell him in
what terrestrial latitude the sun viii
nave precisely that height on that par-
..oui.l Gay OF the year. Thus the Ter
rcstrial latitude becomes known eosiiv
enough. and if only the captain couiI
get ms longitude. too. he would know
noOn ""s a.
we have seen that the sextant oh
serNallons furnish the error OF the
chronometcr according to ship's time
Wt noon. In other words. the contair
Is IN possession OF the correct local
tne In the place where the shin nctu-
any is. Now, if he also had the correct
,ihe at mat moment OF some wolf
hho"n place on shore, he would know
the difference in time between ihot
piace on shore and the ship. But every
Traveller by land or sea is aware that
there are always differences OF time
petWeen different places on the Garth
II a watch be right on leaving New
nork' Tor instance. it will be much too
1aSt on arriving at Chicago or San
francisco: the farther you go the
larger becomes the error of your watch
In iact. If you could find out how
Hluch 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
10 correct Greenwich time" on shore
before the ship leaves port His oh
servauons having then told him how
much this is wrong on that particular
day. and in that particular SPOT where
the ship is, he knows at once lust how
far lie has Travelled east or west from
S Si,' IN other words he knows
his longitude from Greenwich" for
longitude is nothing more than dis
lance from Greenwich in an east-and-
west direction. Greenwich observatory
IS selected as the beginning of things
for measuring longitudes. because that
worthy monarch. Charles II. (who
sec ms to have done one wise thing).
established it at date preceding the
foundation OF all other existing astro-
nomical observatorics
One OF the most interesting bits of
astronomical history was enacted in
connection with this matter of longi-
tude. From what has been said it is
clear that the ships longitude will be
obtained correctly only if the chronom-
eter has kept exact time since the de-
parture Of the snip from port. Even n
very small error OF the cnronometer
Will throw out the longitude n good
many miles, and we can understand
readily that ii must be difficult in the
extreme to construct q mechanical con-
trivance capable of keeping exact time
when subjected To the rolling and pitch
ing of Il vessel at sea.
1t was as recently as the year 1886
that the frs. instrument capable OF
keeping anything like accurate time at
sea was successfully completed. 1t
was the work of an English watch
maker named John Harrison. and is
one of the few great improvements in
matters scientific which the world owes
TO Il desire for winning n money prize
Ii appears hat in l11i Il committee was
appointed by the House of Commons,
with no less person than Sir Isaac
Newton himself some OF its members,
TO consider the desira bility of Offering
governmental encoura cement of the
invention of some means of finding the
longitude at sea. Finally the British
government offered a reward of $50. 900
for an insrument which would find the
longitude within sixty miles: $4,000. il
within forty miles. and $4,000 if with
in thirty miles. Harrison's chronome-
ter was finished in 1895. but did not re-
ceive the final payment of his prize
until 1864.
We have no space to enter into an
account of the veXatious delays and
official procedures TO which he was
forced to submit during those twenty
ainhf L. n ~