The Springfield herald., 1897-02-19
HOW MUCH IS A KNOTT
Few LApdsmel Know Its Vsius E1presss
In Miles.

Few LApdsne, Know Its Vsius E1Presss
In Miles.
In l $ day of record breaking Dy
ocean steamers when every Dig steaM
er that comes into port Is expected 10
carry a record hung at yardar!n' 30
to speak, how many andsmen Know
the meaning of the term knot, IN
which rate of speed at sea Is chiehy
expressed? 1t is purely and wholly
nautical term, having specific applica-
tion to the speed and distance made by
a vessel moving In the water, says the
New York Herald.
The word knot" Is the mariners
term for a nautical mile, and Its use Is
really derived from the log line used
by navigators of the ocean when they
wish to determine the speed and the
distance that the ship has probably
sailed in given time. The log line
Is an important and 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 Mt 1t with
his sextant, from which the actual po-
sition Of the ship is worked out. With
the data taken by n 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 seconds) noting
the force and direction of the wind. the
possible currents, or other influences
acting favorably or against the prog
ress Of the ship, the navigator is en-
abled to calculate very nearly, in over
cast or foggy weather, about where his
ship is at any hour of the day. mis- is
called working out the position of the
ship by dead reckoning"
Every one who studied the geograph-
ical table in his early school days will
recall that part of the sing-sone recita-
tion running fike this "SiXty-nine and
one-si1th statute miles, or sixty geo.
graphical miles, equal one degree of
longitude at the equator" Now, the diff
ference between n statute mile and
nautical or geographical mile, is that
tue latter Is about S06 feet greater than
the former. There are sixty geograph-
ical miles to each degree of latitude, OF
to each degree of longitude at the equa-
tor, which divisions of miles are called
minutes in the nautical vocabulary,
hence the old saying. IA mile min
ute." As there are $3.50 degrees, or me-
ridians, of longitude, there are p, 900
minutes, or miles, in the entire circum-
ference of the world. at the equator;
and 1t has ben mathematically deter
mined that one minute-one geograph-
ical mile-at the equatorial circle is
equal to 6,0S67 feet. But 1t has been
the practice of mariners not to be too
exact on small fractions when measul.
Ing distance as great as mile, conse-
| quently the practice of defining knot
or nautical mile as equal to 6,0SO feet
instead of 6,0S6.7 feet. has been gen
orally adopted.
| When the navigator desires to make
a log-line by which to ascertain the
speed which his vessel Is making
through the water, he follows the con
stant 6,OSO. AS the number of seconds
| in an hour are to 6,OSO feet, SO are the
number of seconds in the time glass (to
be used for measuring the ships speed
| to the number of feet in each unit of
measurement marked Off on the log
line. II half-minute (thirty seconds)
| glass is to be used. the knots must be
other, and the number Of these knots
which pass from the reel over the
stern while the sand is running from
| the top bulb to the lower bulb of the
| glass is equal to the number of knots
or nautical miles that the vessel would
make In an hour, providing the same
conditions for speed continue.
For instance. If the engines of
| steamship continue to make the same
speeu uuFllS tle uoNF, OT IL lue loICe
of wind and spread of canvas of a sail
ing vessel continue the same, the num-
Der of knots on the line passing from
the reel while the sand is running
through the thirty-second glass is as
good an actual measurement of the
vessels speed through the water as
could be obtained, except that the
course should be measured by an act,
ual survey with Instruments If it was
shown that the vessel was making ten
knots, she would cover ten geograph-
ical miles, or n little more than eleven
and one-half land miles. or eleven and
a half times $3.50 (5.2SO feet being
equivalent to a land mile. Hence, to
speak Of the City of Paris having made
626 knots of nautical miles in twenty,
four hours, she covers distance OF
6O41a land miles, as comprehended in
railroad distances or a rate of twenty.
five land miles an hour, which is faster
than most railrOad trains travel