A CERTAIN IMPROVEMENT IN NAUTICAL COMPASSES
Year: 1867

page_text: LETTERS PATENT to Pierre Michel Albert Laurent, of St. Nazaire, Town
in the Empire of France, late an Officer of the Imperial Marine, for the
Invention of "A CERTAIN IMPROVEMENT IN NAUTICAL COMPASSES."
Sealed the 8th November 1867, and dated the 13th July 1867.
PROVISIONAL SPECIFICATION left by the said Pierre Michel Albert
Laurent at the Office of the Commissioners of Patents, with his Petition,
on the 18th July 1867.
I, PIERRE MICHEL ALBERT LAURENT, of St. Nazaire, Town in the Empire
of France, late an Officer of the Imperial Marine, do hereby declare the
nature of the said Invention for "A CERTAIN IMPROVEMENT IN NAUTICAL
COMPASSES," to be as follows:-
The object of my Invention is the prevention of oscillation of compass cards
in iron or other ships and in high seas. I obtain steadiness of the card by
inaking it in such manner that its weight shall be as far as possible from the
centre of suspension, that is to say, by making the card as light as possible in
the centre and carrying the weight to the circumference.
The object of this arrangement, which is to increase the inertia of the card,
can be obtained either by constructing the card in such manner that the
weight shall be as far as possible from the centre, or by attaching weights of
copper or other heavy material to an already constructed card so as to take
the weight from the centre. I find it most convenient to use circles or rings
of copper or other metal having a smaller diameter than the card, the rings
are fixed either on top of or underneath the card, as may be required, regard
being had to the species of card uséd. The rings are attached to the card by
screws, springs, hooks, or any other convenient appliance. These circles,

page_text: which I call inertia circles, should be of graduated weight from 1 to 4 ounces,
increasing by ounces from that nearest the centre to that nearest the cir-
cumference. The number and weight of the rings to be fixed to the card
will vary according to the cause of oscillation; two, three, or more circles
may be fixed to the card as required.
SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said Pierre Michel Albert Laurent in the Great Seal Patent
Office on the 21st December 1867.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, PIERRE
MICHEL ALBERT LAURENT, of St. Nazaire, Town in the Empire of France,
late an Officer of the Imperial Marine, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Thirteenth day of July, in the year of our Lord One
thousand eight hundred and sixty-seven, in the thirty-first year of Her reign,
did, for Herself, Her heirs and successors, give and grant unto me, the said
Pierre Michel Albert Laurent, Her special licence that I, the said Pierre
Michel Albert Laurent, my executors, administrators, and assigns, or such
others as I, the said Pierre Michel Albert Laurent, my executors, adminis-
trators, and assigns, should at any time agree with, and no others, from
time to time and at all times thereafter during the term therein expressed,
should and lawfully might make, use, exercise, and vend, within the United
Kingdom of Great Britain and Ireland, the Channel Islands, and Isle of Man,
au Invention for "A CERTAIN IMPROVEMENT IN NAUTICAL COMPASSES," upon the
condition (amongst others) that I, the said Pierre Michel Albert Laurent,
my executors or administrators, by an instrument in writing under my, or
their, or one of their hands and seals, 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 Seal Patent Office
within six calendar months next and immediately after the date of the said
Letters Patent.
1. NOW KNOW YE, that I, the said Pierre Micbel Albert Laurent, 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 thereof, reference being had to the Drawings
hereunto annexed, that is to say :-
The object of my Invention is to diminish or entirely obviate the oscillation
uf compasses and magnetic needles on board ships and vessels in a heavy sea.

page_text: My Invention is applicable to compass cards, to sets of magnetic needles,
and to single magnetic needles used on board all kinds of vessels, or on floating
or moving bodies. It applies to all forms, sizes, and arrangements, as well as
to all modes of suspension of compass cards or magnetic needles.
The same Invention can also be applied to render magnetic needles or
compass cards more sensitive when sluggish. That which characterizes the
present Invention and distinguishes it from all others having the same object
is that I obtain the stability of magnetic needles and compass cards by loading
them with weights placed as far as possible from the point of suspension, and
that, on the other hand, I obtain more sensitiveness by loading the compass
cards or needles with weights as near the centre as possible. Carrying out
tbis principle I have devised the following methods whether for rendering
compass cards or needles more steady or more sensitive.
To give more stability to compass cards or magnetic needles I diminish as
much as possible the weight at the part adjoining the point of suspension either by
thinning the needles at this part or by changing their form by making the
cap lighter and diminishing the weight of the central part of the compass
card, or by suppressing this central part and increasing the weight near the
circumference by giving to the extremities of the needle or needles an enlarged
form, and if necessary by adding near the extremity of the needles an additional
weight, such as a piece of metal, or a ring of metal on which the card is glued
or fastened. To render the needles or cards more sensitive I diminish as
much as possible the weight at the parts most distant from the point of sus-
pension by thinning the needles at their extremities, and I increase as much
as possible the weight near the point of suspension by enlarging the needles
at this part by increasing the weight of the cap, and if necessary by the
addition of several weighty pieces of metal for example.
The foregoing are the principal modes by which I render compass cards or
magnetic needles. more sensitive or more steady, but for rendering steady a
needle or a set of needles, or a compass card already constructed, I adopt the
following methods:-Suppose, for example, that it is required to render a
compass card or a set of magnetic bars or needles more steady I place weights
on opposite sides.of and as far as possible from the point of suspension, taking
care to place the weights equally so as to maintain the horizontal position.
The heavier these weights (which I call inertia weights) the more steady will
be the card or needle; the farther these inertia weights are placed from the
point of suspension the greater the stability, from which it follows that I
regulate the degree of stability of the cards and needles according to the
requirements of the weather and the sea; when, on the contrary, the inactivity

page_text: or sluggishness of the compass card or needles necessitates an increase of
sensitiveness I obtain it by weighting the card or needles as near as possible-
to the point of suspension, thus to increase the stability of a compass card,*or
a magnetic needle, or a set of magnetic needles I weight them as far as
possible from the point of suspension to increase the momentum of inertia,
while for increasing their sensitiveness I weight them on the contrary as near
as possible to the point of suspension to diminish the momentum of inertia.
The weights with which I weight the compass cards or needles, whether to
increase or diminish their stability, I call "inertia weights." I give the inertia
weights the form which best suits the arrangements of the instrument, thus
I employ inertia. weights having the form of a ring or a portion of a ring of
cubes, of cylinders, of cones, balls, or other convenient form; I employ for
the inertia weights any convenient substance, such as copper, brass, bronze,
lead, tin, platina, silver, or any other substance which does not possess
magnetic properties to influence the compass card or needle. The inertia
weights are according to. requirement fixed, adjusted, attached, or suspended
to the needles or compass cards by means of pins, screws, springs, books,
gum, flexible or rigid wire, or by any other method which renders them as it
were a part of the needles or card. They are fixed permanently, or are
movad such manner as to be taken away and changed at will, or are
placed in such manner as to be moved at will nearer to or farther from the
point of suspension.
In the accompanying Drawings Figure A represents an exterior view of a
compass card; Figure 1 shows a compass card on which is fitted an inertia
ring a, b, c, this ring is placed on the top of the compass card, where it is held
by three pins protruding from the card and entering three corresponding holes
in the ring at a, b, c. This arrangement is very convenient as it permits of
removing the inertia ring or of putting it in place without taking the compass
card off its pivot. I have a set of graduated rings and use a ring more or less
heavy as required.
Figure 2 represents the same arrangement, but placed underneath the card,
either on the needles or on the edge of the card; the inertia ring can be
suspended at a distance below the card by means of wires or rigid pins, or by
flexible wires.
Figure 3 represents a card furnished with 4 inertia weights a, b, c, d; these
weights are fixed on the card, and are held either by pins, as in Figure 1, or
by any other contrivance; either 4 or 2 only of these weights can be used
иs required; they can be fixed immediately underneath the card or be sus-
pended at a distance below it.

page_text: Figure 4 represents a card, the cap of which carries a diametrical bar a, b,
on which the inertia weights a and b can be adjusted.
Figure 5 is a vertical section of this system, which can be applied either
above or below the card.
Figure 6 shows a vertical section of another arrangement of movable inertia
weights.
Figure 7 represents à compass card weighted at its centre with an inertia
weight a, b, d, to give more sensitiveness to the card; this inertia weight
instead of being placed above the card can be fixed below it.
Figure 8 represents the under side of a compass card and shews one of the
arrangements which I apply to magnetic bars to render the card more steady
at sea. The magnetic needles, two or more in number, are bent as seen at d,
a, d, e, b, e, in such manner as to place them as far as possible from the
point of suspension; they are connected with the cap c by the rod a, b, and
can be carried by a metal ring d, l, o, d', n, m, to increase the weight near
the circumference. The extremities of the curved needles can be of the form
shewn in Figure 8, or of any other form advantageous to their magnetic
power.
And having now described the nature of my said Invention, and in what
manner the same is to be performed, I declare that I claim as my improve-
ment in nautical compasses, rendering compass cards and magnetic needles
more steady or more sensitive by regulating their weight near the circum-
ference and near the point of suspension according to requirement, substan-
tially by the means and in manner herein-before described and represented
in the accompanying Drawings.
In witness whereof, I, the said Pierre Michel Albert Laurent, have
hereunto set my hand and seal, this Sixth day of October, One thousand
eight hundred and sixty-seven.
P. M. A. LAURENT. (L.S.)
0 Witness,
CH. ARMENGAUD, Je.
Civil Engineer,
Boulevard de Strasbourg, 23,
à Paris.