Wood County reporter. [volume] (Grand Rapids [i.e. Wisconsin Rapids], Wis.) 1857-1923, 1898-11-24
THE SPEED OF A SHIP.
Methods Employed in the Navy foa
Measuring 1t - The Use of
the Log.


How do you ascertain the speed OF
a vessel?" is a question frequently adj
dressed to naval men, and an explana-
ton will therefore probably be of in
terest to many readers. There are sew
eral methods, the commonest and
most ancient being by the use of the
log" This instrument consists Oh
three PARASITIC Iogship, the line, and
the marks. The logship is piece OF
wood about half an inch thick, and
shaped like a quadrant, with a piece
Of lead let in round the circular edge
TO make it float perpendicuIarly in the
water. II is slung by lines at each
angle, the three lines being joined to-
gether about two feet from the log
ship. Two Of the lines are securely
fixed to the ship" and the other has
a bone peg at the end, which, being
pushed into a hole in the ship, temper
arily fastens it there. From the point
of juncture of the three lines a suffi-
cient 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 a piece of bunting. From the
bunting is measured AZ feet inches,
and the line marked here with a piece
of leather. Then another At feet 8
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
logiine 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
Qength oil sandglass), $3.50 feet (num-
Der of feet in a nautical mile); length
Of line required-which works out to
~ feet inches.
To use the log four persons are re-
CURED; two men to hold the reel on
which the line is wound; the quarter
master, to hold the glass; and the mid
shipman Of the watch. to heave the
log. The last-named puts the peg firm
~ in the logship, and then gathers
three or four coils of line in his hand,
sufficient to admit of the logship be-
ing thrown we'll clear of the ship. He
asks, CLEAR glass, quartermaster? ?"
Clear glass, sir!" comes the reply,
and overheard goes the logship and
line, the reel rapidly revolving. Pres
emily the MILDLY feels the piece of
bunting passing through his hand, and
he gives the order: Turn" The quar-
termaster 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, "Stop!" cries the quarter
master. The midshipman grasps the
line, assisted by the other reeler, and
looks for the nearest knot, finding a
single one close to his hand. Then the
line is hauled in, and four knots ap-
pear, which signify that the ship is
going AZ 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 is going over four knots,
14second glass is used, the speed be-
ing double that shown by the knots on
the line.
Another method in use is the patent
log. This is altogether mechanical,
and consists of a long cylinder with
clockwork inside it, and four fins on the
outside; it is towed astern of the ship
by a line made fast to swivel in the
head of it. AS it is dragged through
the water the four fins make it revolve.
actua ting the clock work inside, which
registers on a series of dials the num-
Der of knots run. This log has to be
hauled in every time one wants to read
it. But there is another kind where
the fan is towed astern, and the dial
is a fixture in the ship. This is called a
"cherub.'
These logs are not always accurate,
and are constantly verified when near
land by cross-bearings. That is, the
bearings of two well-known points are
taken, and the position so obtained is
marked on the chart, the time of OBJ
servation being noted, and the reading
on the patent log. After an interva!
has elapsed the position of the ship is
again taken by cross-bearings, when
the straight line joining the two places
on the chart will show the direction Of
the course steered, and its length the
distance run. A comparison with the
readings by patent log will give the
error of the machine.
To finish, here is a patent log yarn
as told by an old messmate. l give it
in his own words: ''When in the
Crocodile in the Red sea, just after
taking the reading one night at eight
o'clock, the quartermaster reported:
Shark taken the patent log, sir!'
got another one over at once. At
$3.50 next morning we stopped for half
an hour. To amuse the ladies [ tried
for and caught a shark. On opening
him we found our patent log, and" he
added, gravely, strange to say, it reg
istered the same as the one in use
The line had damned between his
teeth, the fan working all the time he
followed the ship. He had swum just
1872 10 miles. Army and Navy Illus
trated.
COMMODORE PHILIPS CALLERS