Evening star. [volume] (Washington, D.C.) 1854-1972, 1900-02-10
NAVIGATION ON THE SEA
How Ships Find Their Way Across the
Trackless Ocean.
The Captain and His sextant-.Iohn
Harrison and the Important In
vention of the Chronometer

From the New York Evening Post
Any one who has ever been a passenger
| on great transatlantic liner of today
knows what an important imposing per-
sonage is the brass-bound skipper. very
d 'ferent creature is he on the deck OF his
ship from the modest seafaring man We
meet on lani, clad for the time being in his
shore-goiny toys. But the captains dig
nifty is not all brass buttons and gold braid.
He has behind him The powerful support
of a deep. delightful mystery. He it is who
takes the SUM- at noon, and finds out the
ships path at sea. And, in truth. regarded
merely as a scientific experiment the
guiding of vessel across the unmarked,
trackless ocean has few equals within the
whole range of human knowledge It is,
the purpose of this brief article to explain
the manner in which this seeming impos-
siDillty is accomplished. We shall not be
aple TO go sufficiently into details TO enable
him who reads to run and navigate a mag
mhcent steamer, But we hope to diminish
| somewhat that part of the captains vast
dignity which depends upon his mysterious
operations with the sextant.
10 begin, then, with the sextant itself.
Ii Is nothing but an instrument with which
we can measure how high up the sun is 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 begins to watch the sun
| through the sextant shortly before noon
and keeps at it until he discovers that the
! sun Is just beginning to descend. That is
the instant OF noon on the ship, The cap
tam quickly slances 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 cal
ulations whatever.
incidentally. the captain also notes with
| the sextant how high the sun was in the
mo q m
tT'chart room" some printed astronomical
| tables, which tell him in what terrestrial
latitude the sun will have precisely that
height on that particular day of the year.
| Thus the terrestrial latitude becomes
known easily enough, and il only the cap
tain could get his longitude, too he would
| know just where his ship was that day at
noon.
We have seen that the sextant observa-
lions furnish the error of the chronometer
according to ships time at noon. In other
words, the captain is in possession of the
correct local time in the place where the
ship actually is. Now, If he also had the
correct time at that moment of some we'll
| known place on shore, he 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
differences of time between different places
on the earth. II a watch be right leav-
ing New York, fer instance, it will be much
too fast on arriving at Chicago or San
Francisco; the farther you go the larger
becomes the error of your watch. In fact,
if you could find out how much your watch
had gone into error, you would in sense
know how far east or west you had tray
eled.
Now, the captains chronemeter is set to
| correct Greenwich time" on shore before
the ship leaves port. His observations hay-
ing then told him how much this is wrong
on that particular day, and in that particu-
| lar spot where the ship is, he knows at
once just how far he has travelled east or
west from Greenwich. In other words. he
ta1at-rr ftRr.sA 49,
for longitude is nothing more than distance
from Greenwich in an east-and-west d.
rection. just as latitude is only distance
from the equator measured in a north-and-
south direction. Greenwich observatory is
selected as the beginning of things for
measuring lonSitudes, because that worthy
monarch Charles IL (who seems to have
done one wise thing established II at q
date preceding the foundation of all other
existing astronomical observatories.
One of the most interesting bits Of astro-
nomical history was enacted in connection
with this matter of longitude. From what
has been said, it is clear that the ships
longitude VIII be obtained correctly only if
the thermometer has kept exact time since
The departure of the ship from port Even
very snail error of the chronometer will
throw out the longitude good many miles,
and We can understand readily that it must
be difhcuit in the extreme to construct a
mechanical continuance capable of keeping
exact time when subjected to the rolling
and pitching of vessel at sea.
II WAS ds recently as the year lIS6 that
the hrst instrument capable of keeping any
thing like accurate time at sea was sue
cessfully completed. 1t was the work of an
English matchmaker named John Harrison
and is one of the few great improvements
IN matters scientific which the world owes
to desire for winning a money prize Ii
appears that in 1114 committee was APP
pointed by the house of commons with no
less a person than Sir Isaac Newton himself
as one OF It's members, TO consider the de-
sirablllty OF offering governmental encour-
agement for the invention of some means of
hndlnS che longitude at sea. Finally the
British government offered a reward of
SJo,oD Tor an instrument which would find
the longitude within sixty miles; S75ODD IL
WITHIN forty miles, and slo0.0O. If within
thirty miles. HarriSon's thermometer was
nnlshed in 1875. but he did not receive the
iinai payment of his prize until 1764.
we have not space to enter into an ac-
count of the vexatious delays and official
procedures to which he was forced to SUBJ
NIT during those twenty-eight long years.
II Is matter OF satisfaction that Harrison
llVed to receive the money which he had SO
thoroughly earned. He had the genius to
plan and master intricate mechanical de-
tails, but perhaps he lacked in some degrees
the ability of tongue and pen to bring them
nome to others. This may be the reason
he is so little known. though il was his
fortune to contribute so large and essential
a part to the perfection of modern nayiga-
ton. Let us hope this brief mention NAV
serve to recall his memory from oblivion
even for fleeing moment; that we NAV
not have written in vain of that Longitude
to which his life given.
An "American Duel" Mt HefdeIbery
From Science.
During my residence in Heidelberg a la