The Wichita daily eagle. [volume] (Wichita, Kan.) 1890-1906, 1893-02-21
A KNOT AND A MILE.
How Navigators Compute Distanc
ssDaad RacEoDtng

How Navigators Compute Distance
! dead Reckoning"
! "Wil you please explain the difference
between a knot and a mile?" What is
the meaning of the term knot; as APP
piled to the great speed made by the
| City of PARISH" us not the term knot
simply unit for measuring the speed
of a vessel at sea, and has it anything
| to do with the actual distance that the
vessel makes in a specific time?' These
are only some of the questions asked
| by "a Subscriber" Constant Reader
and scores of others whose letters ar
rive by each mail and each requesting
reply, some inclosing slip of paper
and an addressed stamped envelope,
| some with stamps only and many
with neither stamps nor money,
| the writers having no thought
| that the answers to such correspond
ents involve not only expense 10 the
newspaper of employing persons to an
swer these letters, but there must also
be added the cost of stationary, post
age, etc. Some writer's also neglect to
| give their full names, others fail 10 give
| their address, SO that many letters can
not be answered. This latter class no
| doubt, charges the editor with indiffer-
ence, while the fault is entirely with
the writer who neglects 10 say to
whom and where the reply is to be
sent.
But what is the meaning of the word
'knot?" it is purely and wholly a
nautical term, having specific and d.
rect application to the speed and dis
tance made by vessel moving in
water The word knot is the
mariners term for nautical mile, and
its use is really derived from the log
line used by navigators of the
ocean when they wish 10 de-
termine the speed and the
distance that the ship has probably
sailed in a given time. The log line is
an important and a very necessary part
of a ships fittings; especially is this the
case when, for several days at sea, the
navigator is unable because of the sun
being hidden by clouds or thick
weather to get peep at it with his
sextant, from which the actual position
of the ship is worked out. With the
data taken by frequent heaving of
the log Ia small block or section of
wood with a long line attached and
run out from the stern of the vessel for
a specific number OF secondsj noting
the force and direction of the wind, the
possible currents, or other influences
acting favorably or against the progress
of the ship, the navigator is enabled to
calculate very nearly, in overcast or
foggy weather, about where his ship Is
at any hour of the day. This is called
working out the position of the ship
by dead reckoning"
Everyone who studied the geograpb-
ical table in his early school days viii
recall that part of the sing-song recita-
ton running like this: 80 10 statute
miles or 60 geographical miles equal
deg. of longitudea at the equator" Now,
the din ference between a statute mile
and nautical or a geographical mile
is that the latter is about sos feet
greater than the former. There are 90
geographical miles 20 each degree Of
latitude, or TO each degree Of longitude
at the equator, which divisions Of
miles are called minutes in the nau-
teal voca bulary. hence the old saying
"a mile a minute" As there are $50
dogs or meridians Of longitude. there
are 81 GOO minutes or miles in the entire
circumference OK the world at the
equator: and il mas been natbematic-
ally determined that orc minute-one
geographical ulile--at the equatorial /
circle is equal 70 6.os5 feet Bat Il
has been the practice Of mariners not /
20 be too exact on small fractions when (
measuring distance as great a. a mile, .
consequently the practice 81 defining 6
knot or nautical mile as eqBal % s os5 .
feet instead Of 6 Gsg7 feet, has been /
generally adopted
When the navigator desires % make s
q longtime by which 20 ascertain tas /
speed which his vessel Is making
through the water. re follows the con-
slant GO. A. the pumber q seconds
n an hour are 10 1850 feet 40 are TIE
number of seconds 10 the tirae-vlass 20
he usedl FOR measuring the ships speed