Wichita eagle., 1890-01-04
SAILING THE CIRCLE.
COMPARATIVE PERFECTION OF THE
ART OF NAVIGATION.
Shortening the Sailing Courses of Ships
Long Voynges-Straight and Curved Lines
the Chart-Important Work of tho
photographic Office

|
on the Chart-Important Work of the
photographic Office.
The art of navigating ships across seas and
oceans from the port of one country to that
of another is one of which the world in gen
eral outside the nautical and Autographed
professions knows little or nothing, and yet to
the progress and comparative perfection
which have been achieved in it are largely
due the extent and success of the vast COM
merce between the nations of the earth
which make of the oceans great interna-
tional highways over which are carried the
! products of all climes to ali other chimes
The older maritime nations that propelled
! their vessels with oars and had only the sun
| by day and stars by night to guide them
rarely steered their galleys far from land
| but Rugged the shore The introduction Of
/ the mariners compass to European nations
| about 600 years ago-though the Chinese
claim to have used it hundreds of years earli-
Grand the substitution OF sails for oars,
made it practicable to strike out boldly into
the ocean and steer fixed course, subject, to
| be sure, to the alterations from the existence
! of ocean currents and the occurrence Of
head winds. 1t was the mariners compass
that enabled Columbus to steer westward
from Spain and discover the American con-
tinent
MERCAToR's CHART.
For some time after the introduction Of
the mariners compass navigation was still
very imperfect, in consequence OF the mac
curacies of the plane chart which was the
only one then known and not much was
done until the publication of Mercator's
IL Ia
on the subject of navigating the ocean The
method OF constructing charts on Mercators
projection depends upon the development of
cylindrical surface, by which means they
have the parallels of latitude and circles of
Longitude respectively represented by paral-
lei straight lines. But while this was a
great improvement over former charts, and
is the chart in common use today, until quite
recently it could not be depended upon by
the mariner to shape course by the shortest
route between two distant points without in
volving extensive mathematical calculations
on his part. For the present purpose, then
it may be said that the first thing the navi-
gator does on going on long voyage after
making his otflng, as it is termed-that Is,
getting clear of lands to shape his course
to the point of destination or to some land
mark on Inc cceSU neUT 10 IL. tie LOOKS over
his chart to see if there are shoals or rocks or
other dangerous places, and if there be he di-
reefs his course primarily so as to avoid
them; if not, the difference in latitude and
longitude between the two ports being taken,
the distance and course can be obtained by
the aid of tri gonometry.
The shortest way TO any two places on the
face of the globe is not found by following q
line upon ordinary Mercato; charts drawn
between those places 1t is found on the line
of the arc of the great circle, so called, which
on an ordinary chart would form a curved
line, the arch Of which would incline north
ward at the north side Of the equator and
southwark to the south of it. What is termed
the terrestrial meridian is the great circle
formed by the intersection Of the surface OF
the earth by the plane passing through the
poles and the spot which the spectator
may be standing, and the first meridian is
the meridian from which longitudes are reck-
oned
WORKING OUT GREAT CIRCLE ROUTE
Now, the idea of great circle sailing is to
secure the shortest route between any two
points between which long eIpanses of sea o..
ocean intervene. Heretofore it has been a
very serious matter to work out a great cir
to go through great number of nathemat-
ical calculations in order 10 obtain the vari-
Gus points for the processes of the route On
an o! binary chart, as already said, . great
circle line would appear as 4 curve Sup
pose q course was to DE shaped from the
Grand banks of Newfoundland to Cape Clear,
on the west coast of Ireland. Let straight
line be drawn on the map for the course II
fnllA lic+ap ,1,II l.
tween the two points would be much longer
than if sailed on the line OF the great circle, /
going considerably south of the latter This
is the fault OF the method by which the chart
has been projected.
To give an illustra ton of how a line over a /
convex surface may be . straight one, as well /
as a straight line over plane surface may
be convex one, as shown, it may be stated /
that II the spectator were placed at the CEN !
Ger OF the earth, every great circle on its sur
face is bound TO cut his eye, aid viii conse-
quently appear TO him as perfectly straight
lines, whereas, IN fact, they are really curved,
and the amount of their curvature varies &C.
cordin2 20 the distance from the equator
On the equator or on Tire meridian the
ships or Mercator track viii coincide with
the great circle track, and tie course II
south. 1t follows from this condition Of
things that, II chart could be obtained that
was projected on plane surface. on which
the lines were placed IL the exact positions
in which they could be seen By az observer
at the center Of the earth. we should have
chart on which every straight hne, no matter
In what direction i, was drawn. Is bound 10
be q great circle or segment Of The same.
Now soob chert-or rather series Of charts
embracing this idea Of const-oc.son-hes been
compiled BY tbs hydroSraphic Office CT the
United States in the past few years. and has
been Issued in series. the publication O. which.
as well, indeed, as the work Of computation, Is
sen IN progress, the intention being 20 make
the work as fully exhaustive a the exlgs1-
cies Of navigation viii ever Be likely 70 cal
for. That charts Of this nAsare have long
been nsedsd by navigators Is well known, and
the Lack o. sch aids heretofore nse operated
against tie general adoption az zee grcs; cir
Gle track method Of navlxat,o1L N other
words, the effect Of tire publication O; ,hese
charts VII be % shorten kong voyzTes by
making them or more dire: hines than oould
be run on IL. Euss o: Al ordinary pane
S,oaA
A CHILD BY EXPRESS