IMPROVEMENTS IN PREVENTING THE DEVIATION OF THE COMPASSES OF IRON OR STEEL SHIPS
Year: 1867

page_text: PROVISIONAL SPECIFICATION left by Frederick Arthur Paget at the
Office of the Commissioners of Patents, with his Petition, on the
13th September 1867.
I, FREDERICK ARTHUR PAGET, of 1, Seymour Chambers, York Buildings,
Adelphi, in the County of Middlesex, Civil Engineer, do hereby declare the
nature of the said Invention for "IMPROVEMENTS IN PREVENTING THE DEVIATION
OF THE COMPASSES OF IRON OR STEEL SHIPS," to be as follows:
This Invention relates to a novel process for preventing the deviation
usually produced by that magnetic state of the hull and other portions of iron
vessels which is caused during building. The needle of the ordinary mariner's
compass being a magnet delicately poised in order that it may set itself to the
magnetic meridian of the earth is necessarly deviated or tends to be deviated
by any magnetism in the hull or other parts of the vessel. The magnetism
which is excited in the iron and steel of the vessel during construction
is that known to be the most dangerous in its effects on the needle, on
account of its progressive diminution and consequent variability, while
the magnetism induced in the iron hull by the earth's magnetism has
little or no influence on a properly placed needle, or can at any rate be
easily corrected. Now it is well known that masses of iron can be
magnetised, and by action in a contrary direction can be yet more easily
demaguetised by means of any one of the following four processes:-Firstly,
magnetism can be induced in a neutral mass of iron by bringing it in
contact with a magnet; secondly, by stroking it with a magnet; thirdly,

page_text: by means of mechanical vibrations undergone by the mass of iron while under
the influence of magnetism, which is induced by process No. 1. The first two
processes are claimed in their application to iron vessels in the British Speci-
fication, No. 227, A.D. 1866; and the third is the action usually undergone
by iron vessels, necessarily always subject to the earth's magnetism, and by
which they are known to progressively lose in course of time most of the
magnetism they have acquired during construction, and to thereby render
useless the tables of errors or the compensating magnets by which it is sought
to correct the original deviations found in swinging such ships. The fourth
process consists in causing electric currents to encircle the mass of iron,
inducing magnetism at right angles to the direction of the electric current.
It is this fourth process and the means of carrying it out which I claim in
their practical applications to the demagnetisation of iron vessels, and of any of
the portions of or on such vessels, such as the steering gear. I first of all survey
the magnetic state of such an iron vessel and of its parts by means of a magnetic
needle, in order to determine the appropriate direction of the magnetism to
be temporarily excited in the hull; in the case of the hull I then temporarily
encircle the ship, preferably around and at right angles to the longitudinal
axis of the hull with an insulated wire or wires composed of any of the metals
known to conduct electricity; and insulated by any of the known means for
insulating such conductors. This insulated wire may either be laid in a con-
tinuous and regular spiral round the ship, or it may be laid in irregular spirals
connected together or in rings, afterwards connected together by any of the
usual means; an electric current, either continuous or interrupted, is then
conducted through this spiral. This electric current is either produced in any
one of the ordinary galvanic batteries or by means of a magneto-electric
induction apparatus, such as that, for instance, described in Specification,
No. 3209, A.D. 1866. The current of the galvanic battery can either be
employed directly; or it may serve to induce a current by means of an induction
apparatus, such, for instance, as that known under the name of Ruhmkorff's
induction apparatus. A rheostatic apparatus, a commutator, or any apparatus
by which the currents of electricity can be regulated and suddenly stopped or
changed in their direction may be employed. I prefer to operate on the hull
of the ship while it is on the stocks or in dry dock, or otherwise accessible.
In case however any such iron ship requiring to be so treated be afloat the
wire can be carried under the hull by divers, or slipped under the hull in form
of open rings, which are afterwards united together by any of the known
means for uniting such wires. The same operation can, if found necessary,
be carried out on any other parts, such as the steering gear, or any beams

page_text: employed in the construction of the vessel. This process may also be combined
should it ever be found necessary with that according to which the separate
plates composing the hull or the other parts of or on the ship are rubbed with
a permanent or an electro-magnet.
What I claim as novel is therefore,-
First. Demagnetising or altering the state of the magnetism of iron vessels
or any parts of or on such vessels by encircling the vessels or the parts of or
on such vessels with an electric spiral or spirals, as described above.
Secondly. The employment of any kinds of galvanic battery for the purpose
of supplying the electricity to such an electric spiral or spirals.
Thirdly. The employment of any kind of magneto-electric machine for the
purpose of supplying the electricity to such an electric spiral or spirals.
Fourthly. The employment of any kind of induction apparatus in com-
bination with a battery.
Fifthly. The employment of any commutator or any rheostatic apparatus
for regulating the currents from the battery, or from the magneto-electric
machine.
Sixthly. The employment of men with diving dresses for winding or
unwinding the insulated metalic wires round the hull.
Seventhly. The employment of the insulated wire in the form of open rings,
which are afterwards united together by any known means.
Eighthly. The combination of this process with that by which the plates
are rubbed with a permanent or electro-magnet, which later process however
I do not claim by itself.