Smyrna times., 1898-11-09
THE SPEED OF A SHIP
METHODS BY WHICH ITS KNOTS PER
HOUR ARE MEASURED.

An Interesting Description of the |
Mechanism and Use of the Log, With
n Truthful Red Sen Shark Story At
tnchment.
"How do you ascertain the speed Of |
a vessel?" is a question frequently ad- |
dressed to naval men, and an explana-
tion will therefore probably be of inter-
est to many readers. There are several
methods, the commonest and most an
tient being by the use of the Clog"
This instrument consists of three parts
the logshiR the line and the marks.
The logship'is piece of wood about
half an inch thick and shaped like
quadrant, with a piece of lead let in
round the circular edge to make it float
perpendicularly in the water. 1t is slung
by lines at each angle, the three lines
being joined together about two feet
from the logship. Two of the lines are
securely fixed to the ship and the other
has bone peg at the end, which, being
pushed into hole in the ship, tempo
rarily fastens it there.
From the point of juncture of the three
lines sufficient length is measured,
generally about 100 feet, to take the
logship we'll clear of the ships wash.
This is called the "stray line' and is
marked with piece of bunting. From
the bunting is measured AZ feet
inches, and the line marked here with
a piece of leather. Then another AZ feet
inches is measured off and marked
with two knots, then another space
the same length, and marked with
three knots, and so ON as far as seven
knots. Halfway between each batch of
knots one single knot is made. The log
line is then ready for use
The space between the. knots is found
from the simple little rule of three sum:
As 5000 seconds (number of seconds in
an hour), % seconds (length of sand
glass;, 6,0S0 feet (number of feet in
nautical mile); length of line required
which works out to a! feet 8 inches.
To use the log four persons are re-
quired-two men to hold the reel on
which the line is wound; the quarter
master, to hold the glass, and the mid
The last named puts the peg firmly in
the logship and then gathers three or
four coils of line in his hand, sufficient
to admit of the logship being thrown
we'll clear of the ship. He asks, "Clear
glass, quartermaster?"
"Clear glass, sirl" comes the reply
and overheard go the logship and line,
the reel rapidly revolving. Presently
the MILDLY feels the piece of bunting
passing through his hand, and he gives
the order "Turn." The quartermaster
turns the glass and watches the sand
while one "reeler" holds the reel we'll
over his head, so as to give the line fair
| play. When the sand has run out,
"Stopp cries the quartermaster.
The midshipman grasps the line, as
sisted by the other reeler, and looks for
the nearest knot, finding a single one
close to his hand. Then the line is haul
ed in, and four knots appear, which
signify that the ship is going four and
half knots through the water. The
jerk of the line draws the peg from the
logship, which now floats ON its fiat
side and is easily hauled in. When a
ship isagoing over four knots, a IA Sec
ond glass is used, the speed being double
that shown by the knots on the line.
Another method in use is the patent
log. This is altogether mechanical and
consists of long cylinder with clock
work inside it and four fins on the out
side. 1t is towed astern of the ship by q
line made fast to a swivel in the head
of it. AS it is dragged through the wa
ter the four fins make it revolve, actu-
ating the clockwork inside, which regis
ters on a series of dials the number oi
knots run. This log has to be hauled il
every time one wants to read it, but
there is another kind where the fan il
towed astern and the dial is a fixture
in the ship. This is called "cherub. >
These logs are not always accurate
and are constantly verified when neal
land by cross bearings-that is, tn,
bearings of two well known points ar,
taken, and the position so obtained i
marked on the chart, the time of obser
vation being noted and the reading OF
the patent log. After an interval ha
elapsed the position of the ship is agail
taken by cross bearings, when tn
straight line joining the two places o.
the chart will show the direction of tn
course steered and it's length the distano
run. A comparison with the reading
by patent log will give the error of tn
machine.
To finish here is patent log yarn
as told by an old messmate. I give it j
his own words: "When in the Crocodil
in the Red sea, just after taking th
reading one night at 8 o'clock, th
quartermaster reported, Shark take
the patent log, sirl' 1 got another on
over at once. At 80 next morning W
stopped for half an hour. To amuse th
ladies I tried for and caught sharl
: On opening him we found our pater
log, and" he added gravely, "strane
to say, it registered the same as the OIL
in use. The line had jammed betwee
his teeth, the fan working all the tin
he followed the ship. He had swul
Just 1879 7-10 miles Navy and Arm
o illustrated.