AN IMPROVED LOG OR Apparatus for Measuring THE SPEED OF VESSELS
Year: 1875

page_text: LETTERS PATENT to William Clark Russell, of Ramsgate, in the
County of Kent, for the Invention of "AN IMPROVED LOG OR
Apparatus for Measuring THE SPEED OF VESSELS
PROVISIONAL SPECIFICATION left by the said William Clark Russell
at the Office of the Commissioners of Patents, with his Petition,
on the 23rd July 1875.
I, WILLIAM CLARK RUSSELL, of Ramsgate, in the County of Kent,
do hereby declare the nature of the said Invention for "AN IMPROVED
LOG OR APPARATUS FOR MEASURING THE SPEED OF VESSELS," to be as
follows: :-
My Invention relates to an improved ship's log, which will instan-
taneously and without being timed indicate the speed of a ship, no com-
putation of any kind being necessary, neither is it requisite to haul the
log inboard in order to consult it, as in the case of other logs, the speed
being at once indicated by an instrument visible on deck. Moreover,
in this improved log the errors and disadvantages common to other logs
are avoided.

page_text: My Invention consists in the combination of a line to be towed astern
of a ship with an instrument fixed in any convenient position aft or
amidships for indicating the strain of the line towed, the said instru-
ment being constructed as hereafter described. The line may be of
any convenient length or size, but of a certain or known.weight (when
wetted), and the instrument is graduated to correspond with the position
assumed by the index under the varying strain of a rope of a certain
weight towed at different speeds, the graduation being effected either
from actual experiment or from calculations based thereon.
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A convenient form of instrument for the purpose is a spring or other
balance or dynamometer, and to enable the indications of the instrument
to be read with facility and to render it in a measure independent of the
rising and falling movements of the ship, which would otherwise cause
the index of the instrument to oscillate to and fro over the dial or scale
the index is not connected directly with the spring, but is operated by
an arm playing freely between pins on the index, which is thus made to
In the case of a
indicate the mean of the oscillations of the said arm.
dial instrument this arm would be fixed on an axis carrying a pinion
actuated by a rack connected to the spring to which the log line is
attached, but the instrument may be otherwise constructed.
SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said William Clark Russell in the Great Seal Patent
Office on the 22nd January 1876.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, WILLIAM
CLARK RUSSELL, of Ramsgate, in the County of Kent, send greeting
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Twenty-third day of July, in the year of
our Lord One thousand eight hundred and seventy-five, in the thirty-
ninth year of Her reign, did, for Herself, Her heirs and successors,
give and grant unto me, the said William Clark Russell, Her special
licence, that I, the said William Clark Russell, my executors, adminis;
trators, and assigns, or such others as I, the said William Clark Russell,
my executors, administrators, and assigns, should at any time agree
with, and no others, from time to time and at all times thereafter

page_text: during the term therein expressed, should and lawfully might make,
use, exercise, and vend, within the United Kingdom of Great Britam
and Ireland, the Channel Islands, and Isle of Man, an Invention
for "AN IMPROVED LOG OR APPARATUS FOR MEASURING THE SPEED OF
VESSELS," upon the condition (amongst others) that I, the said
William Clark Russell, my executors or administrators, by an instru-
ment in writing under my, or their, or one of their hands and scals,
should particularly describe and ascertain the nature of the said
Invention, and in what manner the same was to be performed, and
cause the same to be filed in the Great Scal Patent Office within sıx
calendar months next and immediately after the date of the said Letters
Patent.
NOW KNOW YE, that I, the said William Clark Russell, do hereby
declare the nature of my said Invention, and in what manner the
same is to be performed, to be particularly described and ascertained
in and by the following statement, reference being had to the accom-
panying Sheet of Drawings, and to the letters and figures marked
thereon, that is to say :-
My Invention consists of a ship's log, which without timing will at a
glance indicate the speed of the ship. The ship's speed is denoted by an
instrument placed on deck. This log is designed to replace the reel log,
from the errors and inconvenience of which it is entirely free.
My ship's log consists of a line and rope united by means of a swivelled
cone towed astern of the ship, attached to an instrument fixed in any
convenient place on the deck, bulwarks, or taffrail of the ship. By
means of the instrument on deck the amount of resistance which the
line meets with in its passage through the water is denoted.
I find that the resistance offered by a line towed astern of a ship
increases approximately in proportion to the velocity of the ship, thus &
line of a given length and diameter towed at the rate of 1 knot or
nautical mile an hour may offer resistance to the extent of 2 lbs.; towed
at 2 knots an hour it may resist to the extent of 4 lbs. 4 ozs. ; at 3 knots
an hour, 6 lbs. 7 ozs., etc Upon these data I base my Invention for
determining speed at sea.
The instrument for ascertaining this varying resistance may be con-
veniently in the form of a spring balance provided with a dial or scale,
and an index for denoting in knots the corresponding resistance in lbs.

page_text: of the line and rope towed
The length and diameter of the line and
rope may be modified 'according to the character of the vessel, a yacht,
for instance, requiring for convenience a smaller apparatus than a large
ship, and a small sailing boat a smaller apparatus than a yacht, but in
all cases where the line and rope differ in length and thickness the
instrument is indexed according to the resistance offered by the water to
that line and rope, the said resistance being always calculated by direct
experiment Any such variation in the size of the apparatus does not
affect the dynamical principle on which the Invention is based.
In order to arrest the vibratory action of the index (produced by the
action of the sea upon the line, the blow of waves, the movement of the
vessel, etc), which would render the indications undeterminable, and
consequently worthless, the instrument 16 provided with mechanism
which checks its sympathetic concurrence with any jump or vibration
of the line.
In order that my Invention may be more readily understood I will
now proceed to describe it with reference to the accompanying Drawings,
in which Figure 1 is a face view of the indicating instrument, Figure 2 is
a rear view of the same with the casing and part of the frame removed to
show more clearly the construction of the instrument, Figure 3 shows on a
greatly reduced scale the line and rope to be attached to the instrument.
A, A, are two spiral springs connected at one end to a fixed part of
the frame, and at the other to the ends of the cross bar B In the
middle of this cross bar is attached a pull rod C passing through a corre-
sponding guiding hole in the casing of the instrument, and terminating
in an eye C¹, to which the line is connected. D is a sector-shaped rack
working on a pivot at D¹, and connected to the cross bar B by a link E
jointed to cach The rack D is curved to the arc of a circle described
from centre D¹, and gears with and operates a pinion F fixed on the
axis of the index G By pulling on the eye O¹ the springs A will be
distended, and the index rotated over the dial His a toothed wheel
keyed on the axis of the index G, and forming the first of a train of any
suitable number of multiplying wheels and pinions I, J, K, L, M. On
the axis of the last pinion there is a fly N, which is set in rapid motion
through the train of wheels whenever the index spindle is rotated in
either direction. This fly serves to moderate or retard the action of the
instrument for the purpose above mentioned, P is an eye fixed to the
casing of the instrument diametrically opposite to the cyc C'. The

page_text: instrument when in use is suspended by the cye P from any convenient
point near the stern of the ship, and to the eye C₁ is attached a thin
line R, to the other extremity of which is connected a rope S
A conc-
shaped weight T of about 12 or 15 inches in length, and of finely tapering
proportions and burnished surface, is introduced between R. and S solcly
to prevent the latter rising out of the water when towed at high speeds.
This weight T is attached to line R by a swivel. The line R may be
made of wire, flax, silk, hemp, or a combination of these, so as to obtain
the smallest possible diameter with the greatest strength. This line R
varies in length according to the tonnage of the vessel, and
varies in length and diameter according to that of line R. Figure 4
shows a slight modification. In this case the rack D is straight, and is
rigidly fixed to the cross bar B in a position parallel or in a line with
pull rod C
The rack operates pinion F, as before, & being a guide stud
to keep the rack in gear with said pinion
the rope S
I would observe that I do not limit myself to tho procisc construction
of instrument described, as such may be varied more particularly as
regards the number of wheels employed for modifying the action of the
index, as well as in respect of the rackwork.
Having described the nature of my Invention and the manner of
performing the same, I declare that what I claim as the Invention to be
protected by the herein-before in part recited Letters Patent is, the
ship's log, substantially as herein described, consisting of a thin line, a
cone, and a rope united, and forming one length towed in the water, and
attached to an instrument mechanically contrived to express by an index
the exact resistance of the linc, cone, and rope at different speeds from
1 to 18 or 20 knots, the said instrument being provided with mechanism
for controlling the indications as described.
In witness whereof, I, the said William Clark Russell, have
hercunto set my hand and scal, this Twentieth day of January,
in the year of our Lord One thousand eight hundred and seventy-