IMPROVEMENTS IN CONSTRUCTING AND TREATING SHIPS AND VESSELS TO CORRECT AND PREVENT COMPASS DEVIATIONS
Year: 1869

page_text: LETTERS PATENT to John Ward Girdlestone, of No. 37, Norfolk
Street, Strand, in the County of Middlesex, Civil Engineer, for the
Invention of "IMPROVEMENTS IN CONSTRUCTING AND TREATING SHIPS AND
VESSELS TO CORRECT AND PREVENT COMPASS DEVIATIONS."
Sealed the 10th August 1869, and dated the 27th March 1869.
PROVISIONAL SPECIFICATION left by the said John Ward Girdlestone
at the Office of the Commissioners of Patents, with his Petition,
on the 27th March 1869.
I, JOHN WARD GIRDLESTONE, of No. 37, Norfolk Street, Strand, in the
County of Middlesex, Civil Engineer, do hereby declare the nature of
the said Invention for "IMPROVEMENTS IN CONSTRUCTING AND TREATING
SHIPS AND VESSELS TO CORRECT AND PREVENT COMPASS DEVIATIONS," to be as
follows:-
This Invention relates to a novel method of correcting and preventing
the deviation of the compasses on iron and steel or composite ships or
vessels by polarizing on a regulated system such parts of the ship as
may be requisite. The compasses of such ships deviate from the earth's

page_text: magnetic meridian in consequence of the sole or joint magnetic influence
of the deck-beams and stringers, the rudder-head, stern-post, hull,
ribs, masts, or other masses of iron near to the compass. It is further
to be remarked that the character of the magnetism of such ships is
partially dependent on the position or bearing of the ship while on the
stocks.
A method sometimes employed for the purpose of correcting the
deviation of a compass has been by compensation, where small
magnets commonly of from twelve to thirty-six inches in length
made from flat bars of steel have been added to the ship and have
been so placed (either horizontally on or at about the level of the deck
or more or less vertically against the binnacle, mast, or some other
portion of the ship near to the compass) as to render the compass
accurate on one or more points, the error remaining on other points
being ascertained by swinging the ship and tabulated.
A method sometimes adopted for the purpose of counteracting the
influence exerted by the rudder-head or stern-post on the steering com-
pass has been by placing some few feet directly ahead of the compass a
vertical column or pillar of iron, the head of the column generally
being at or about the level either of the compass-card or of the deck
on which the compass stands, while the foot of the column usually
rests either on the lower deck or on the bottom of the vessel.
Again it has been proposed to correct the deviation of a compass by
the depolarization or demagnetization of the hull, stern-post, deck beams,
or such other portions of the vessel as in practice might be found to
be necessary by means of electro or horse-shoe magnets, and on the
same principle as that involved in the depolarization or demagnetization
of a polarized or magnetized bar.
According to the first part of my Invention when building or altering
iron, steel, or composite ships I introduce in the construction of the
deck either one or two concentric rings or segments of rings having
their centre immediately beneath that of the compass, the diameter of
the inner ring being of from five to ten feet, more or less, and that
of the outer ring, say, of some five or six feet more. Each ring may be
either intersected, met, or touched by one or more of the deck beams, to
which it may be united or of which it may be independent. These
rings, which I term deck-rings, may be formed of the same description
of iron or steel as that employed in the construction of the ship and

page_text: of a rectangular section or of a section similar to that of the deck-
beams or of any other convenient section. These deck rings, or either
of them, as also one or more longitudinal and transverse deck beams,
or either of them, may in some cases be advantageously introduced
in the construction of the deck of an iron, steel, or composite ship
where other beams or parts of such deck are formed of wood or of
any material other than iron or steel.
In proceeding to carry out the second part of my Invention I
generally and in the first place survey by the aid of suitable compasses
or other instruments the magnetic condition of the whole or part of
the hull, deck beams, steering gear, and other portions of the vessel
so far as I find requisite to enable me practically to ascertain the
prime or main cause or the causes of the deviation observed. I then
for the purpose of correcting and preventing the deviation of a compass
compensate, balance, or overcome the disturbing influence of the whole
or part of the polarized or magnetized iron or steel causing the deviation
by polarizing or magnetizing on a regulated system the whole or part
of either the deck rings above mentioned where these have been made
use of, or the deck-beams, or the ribs, or masts, or stern post, or rudder
head, or other parts of the vessel or any of them, in whole or part,
to such an extent and in such a manner as shall make the needle of
the compass point accurately at the bearing in which the vessel lies
during the operation, the proper direction having been previously
ascertained either by another compass unaffected by disturbing influences
or by taking no local bearings or by any other suitable means.
I carry out the same operation if requisite or advisable on one or more
fresh bearings. Any remaining deviation that may in any case appear at
any other bearing may be ascertained and tabulated on swinging the ship.
My mode of proceeding may be thus more fully described. When
the deviation of the compass (either previous to the commencement
of or during the operations) is primarily or in the main attributable
to the influence of one or more north poles ahead or at the one side
or of one or more south poles astern or at the other side of the
compass, or vice versa, or of one or more north poles ahead or at the
one side and of one or more south poles astern or at the other side
of the compass, or vice versa, the following method of treating the
ship may (either in whole or in part so far as may be requisite and
advisable) be employed for the purpose of correcting and preventing

page_text: the deviation, namely, by imparting either to portions of the above-
mentioned deck rings where these are used, or to the centres or
thereabouts of one or more of the transverse deck beams lying nearest
to the compass, or to the ends nearest to the compass or thereabouts
of one or more of the radial and longitudinal deck beams and stringers
lying nearest to but not running past the compass, or to the ends of
the longitudinal deck beams and stringers running past and lying
nearest to the compass or to the mast, stern-post, rudder head, and
stanchions at or about the level of the compass, or to such of the above
specified portions of the ship as may be constructed of either iron or
steel and may affect the compass when poles are imparted to them at
the parts indicated, south poles if alıcad or at the one side, and north
poles if astern or at the other side of the compass, or vice versa.
When carrying out my above-described Invention by applying my
system of polarization I use either horse-shoe or permanent magnets
or electro-magnets with battery or an electric spiral or spirals with
battery, such as described or referred to in the Provisional Specification
of Letters Patent applied for by Frederick Arthur Paget, and dated
1867, 13th September, No. 2592.
In some cases for the purpose of correcting and preventing the
deviation of a compass my system of polarization may be employed in
combination with that of "depolarization" or "demagnetization," that
is to say, a compass may be rendered accurate by polarizing or
magnetizing one portion and depolarizing or demagnetizing another
portion of the same ship.
In other cases for the purpose above named my system of polarization
may be employed in combination with the column or pillar of iron to
which I have already made reference with or without the system of
depolarization.
SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said John Ward Girdlestone in the Great Seal Patent
Office on the 27th September 1869.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, JOHN
WARD GIRDLESTONE, of No. 37, Norfolk Street, Strand, in the County
of Middlesex, Civil Engineer, send greeting.

page_text: WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Twenty-seventh day of March, in the
year of our Lord One thousand eight hundred and sixty-nine, in the
thirty-second year of Her reign, did, for Herself, Her heirs and successors,
give aud grant unto me, the said John Ward Girdlestone, Her special
licence that I, the said John Ward Girdlestone, my executors, adminis-
trators, and assigns, or such others as I, the said John Ward Girdlestone,
my executors, administrators, 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, an Invention for "Iк-
PROVEMENTS IN CONSTRUCTING AND TREATING SHIPS AND VESSELS TO CORRECT
AND PREVENT COMPASS DEVIATIONS," upon the condition (amongst others)
that I, the said John Ward Girdlestone, 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.
NOW KNOW YE, that I, the said John Ward Girdlestone, do hereby
declare the nature of the 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, that is to say :-
This Invention relates to a novel method of correcting and preventing
compass deviations in iron, steel, or composite ships or vessels by
polarizing on a regulated system such parts of the ships or vessels as may
be requisite, and by the simultaneous employment in some cases of soft
iron, as and in the manner herein-after directed.
In my Provisional Specification I have briefly referred to the cause of
compass deviations and to a circumstance upon which this cause in part
depends. With a view to explaining more fully the particulars of my
Invention as herein-after described these points may be now conveniently
entered into at greater length.
It is generally understood, (1), that the deviations of the compass from
the magnetic meridian are due to the magnetism of the ship; (2), that
the deviations observable by the aid of a horizontal needle when the ship

page_text: is on an even keel consist of two principal parts termed "semicircular"
and "quadrantal." with the addition in some cases of a small part
termed "constant;" (3), that the "semicircular" deviation consists of
two parts, one arising from vertical induction (which in a well placed
compass is but small), the other arising from the permanent magnetism
of the ship and varying in character with the position of the ship when
on the building slip; (3), that the "semicircular" deviation is caused
by a force acting in a particular direction in the ship, which force may in
general be conveniently resolved into two forces, one acting in the fore
and aft line of the ship, and the other acting athwart-ship; (1), that the
"quadrantal" deviation is caused by horizontal induction; (5), that tho
"constant" deviation arises mainly from two causes, namely (a) hori-
zontal induction in soft iron unsymmetrically arrangod, and (6) instru-
mental error; (6), that besides the deviations observable on an even keel
there is likewise the "heeling 'deviation, which is caused as to the
greater part by the vertical force of the ship (i.e., by vertical permanent
magnetism and by vertical induction in vertical iron), and as to the lesser
part by vertical induction in transverse iron.
"
In my Provisional Specification I have referred to two methods
sometimes adopted for the purpose of correcting compass deviations.
With a view to explaining more fully the particulars of my Invention
as herein-after described, the means sometimes employed for the purpose
of correcting compass deviations may bo now conveniently entered
into at greater length.
The semicircular deviation is sometimes corrected either by means of
a magnet placed horizontally in the direction of the force which causes
the deviation, or by means of two magnets placed horizontally, one
directed athwart-ship, the other fore and aft. But in some cases a
vertical column or pillar of soft iron is employed to correct the part of
the deviation arising from vertical induction, one or two magnets being
at the same time employed as above referred to for the purpose of
correcting the part arising from the permanent magnetism of the ship.
The "quadrantal" deviation is sometimes corrected by means of soft iron
rods, cylinders, or chains placed athwart-ship at the level of and at each
side of the compass. The "heeling" deviation when considerable is in
some few cases corrected by means of a magnet placed vertically imme-

page_text: «
"
With a view to explaining more fully the practical details of my
Invention as herein-after described it may be convenient next to describe
a process (to which process as a separate part of my Invention I make no
claim) whereby bars of hard iron or steel (including the deck-beams and
other portions of a ship) may be converted into magnets of two classes,
which may be termed "simple" and "compound." By "simple"
magnets I here mean those that have two end poles of opposite names.
By compound" magnets I here mean those that have a central pole of
one name and two end poles of the opposite name. Simple" inagnets
may be divided into two classes, 1st, those having their right hand (or in
nautical phraseology their "starboard") ends north poles; 2nd, those
having their right hand (or "starboard") ends south poles. "Compound"
magnets may be likewise divided into two classes, 1st, those having
cach a central north pole; 2nd, those having each a central south
pole. I now describe a process of producing "simple" magnets of the
1st class: Let a, b, Figure 1, be the bar proposed to be polarized; place
thercon at or towards either of its ends the horse-shoc magnet x so
that its poles may be parallel with the longitudinal axis of the bar, its
north pole being turned towards the intended south pole of the bar;
then pass the magnet x from end to end of the bar a, b, when that
end of the bar towards which the south pole of the horse-shoe magnet
was turned will be a north pole and the other end of the bar will be a
south pole. By repeating this operation and by regulating the strength
of the horse-shoe magnet the strength of the bar magnet thus produced
may be regulated, and if from any cause the requisite strength should
be exceeded then by reversing the operation the strength of the bar
magnet may be reduced. "Simple" magnets of the 2nd class may be
produced by reversing the operation above described for the production
of "simple" magnets of the 1st class. Figure 2 is drawn in illustration
of a mode of producing "simple" magnets of the 2nd class. I will
next describe a mode of producing "compound" magnets of the
1st class: Let a, b, Figure 3, be the bar proposed to be polarized; place
thereon between the centre (shewn by the intersection of two dotted
lines) and one of the ends of the bar, and close either to the end or to
the centro of the bar, the horse-shoe magnet x so that its poles may be
parallel with the longitudinal axis of the bar, its south pole being turned
towards the intended central north pole of the bar; then pass the
magnet between the end and the centre of the bar; next remove the
horse-shoe magnet from the half of the bar thus treated and place it

page_text: on the other half of the bar so that its poles may be parallel with the
longitudinal axis of the bar, its south pole being turned towards the
intended central north pole of the bar; then pass the magnet r
between the end and the centre of the bar, when the centre of the
bar will be a north pole and the ends thereof will be south poles. The
strength of the bar magnet thus produced may be regulated on the
same principle as that described with reference to the regulation of the
strength of "simple" magnets of the 1st class. "Compound" magnets
of the 2nd class may be produced by reversing the operations abovo
described for the production of "compound" magnets of the 1st class.
Figure 4 is drawn in illustration of a mode of producing "compound
magnets of the 2nd class,
When polarizing a bar of iron or steel or a deck-beam of a ship,
I usually employ either a permanent magnet or an electro magnet,
and I usually place the magnet with which I operate in contact with
the bar; but if from any cause I find this course either impracticable
or inexpedient I place the magnet as near to the bar as may be
practicable or expedient and proceed with the operation as if the
magnet were in contact with the bar. I therefore when polarizing
a deck-beam of a ship either bring the magnet with which I operate
into contact with the beam, or I mark or chalk out on the deck
immediately above the said deck-beam the exact position of the beam
and pass the magnet along the line thus indicated as if along the
beam itself.
In the case of a ship whose deck-beams are constructed of any material
other than iron or steel it may be found necessary, for the purpose of
correcting and preventing compass deviations, to introduce beneath the
deck and near to the compass two or more deck-beams of iron or steel.
In reference to my Diagrams or Figures numbered 5 to 53 inclusivo
(which Figures are drawn in illustration of some specific modes of
correcting under different conditions, referred to hereafter as leading and
secondary, the deviations of any compass placed on or near to the midship
line of a vessel), I would remark that in each Diagram or Figure a circle
represents the compass, and, further, that in each Diagram or Figure
each thin horizontal line represents a deck-beam of either iron or steel
which I convert into a "simple" magnet of the 1st or 2nd class, and each
thick horizontal line represents a deck-beam of either iron or steel which
I convert into a "compound" magnet of the 1st or 2nd class, according

page_text: as it may be necessary to effect the conversion in order to correct the
deviations of the compass as and in the manner herein-after described.
error
The "leading" conditions under which my system of "polarization"
may be most favorably carried out are the following:-(1.) When the
ship's head is placed successively on two of the four cardinal points,
namely, at north or south and at cast or west. (2.) When the
ship's head is placed on one only of the four cardinal points. In
proceeding to carry out my Invention under the first of these two
conditions I place the ship's head in the first instance (by preference)
cast or west (correct magnetic). The force causing the " heeling"
deviation may be then observed by comparing the times of vibration
of a dipping needle in a plane at right angles to the meridian on board
ship and on shore, the dipping needle being placed on board ship
exactly over a deck-beam in a position suitable for a ship's compass
(a mode of observation to which I make no claim as forming a separate
part of my Invention). I correct when advisable the "heeling
by correctly proportioning the times of vibration on board ship and on
shore (through the application of Rules I. and II., which rules with
the others below referred to are herein-after set forth); also I correct
that part of the "semicircular" deviation which is caused by a force
acting in the fore and aft line of the ship (through the application of
Rules III. and IV.); I next place the ship's head north or south
(correct magnetic), and (through the application of Rules V. and VI.)
correct that part of the "semicircular" deviation which is caused by
a force acting athwart-ship. If from any cause the operations have to
be commenced when the ship's head is placed north or south (correct
magnetic), the force causing the "heeling" error may be observed by
the aid of a dipping needle as directed above; and should the error be
such as to need correcting I place the compass over a deck-beam and
(through the application of Rules V. and VI.) correct that portion of
the "semicircular" deviation which is caused by a force acting athwart-
ship, reserving as a rule the correction of the "heeling" error until the
ship's head is placed cast or west (correct magnetic), at which bearing
(through the application of Rules III. and IV.) I likewise correct that
part of the semicircular deviation which is caused by a forec acting in
the fore and aft line of the ship. In some cases a vertical column or
pillar of soft iron may be employed for the purpose of correcting that
part of the "semicircular" deviation arising from vertical induction;

page_text: and when the ship's head is on one of the quadrantal points the "quad-
rantal" deviation may be corrected by means of soft iron rods, cylinders,
or chains placed athwart-ship at the level of and at each side of the
compass. But I make no claim either to the use of such vertical
columns or pillars of soft iron, or to the use of such soft iron rods,
cylinders, or chains as forming a separate part of my Invention. In
proceeding to carry out my Invention under the second of the two
conditions above stated I place the ship's head (by preference) east or
west (correct magnetic); also I correct when advisable the "heeling"
deviation as already directed; also I correct (through the application
of Rules III. and IV.) that part of the "semicircular" deviation which
is caused by a force acting in the fore and aft line of the ship. The
force acting athwart-ship and causing the other part of the "semi-
circular" deviation may next be observed by comparing the times of
vibration of a horizontal needle on board ship and on shore (a mode of
observation to which I make no claim as forming a separate part of
my Invention), and I correct the deviation by correctly proportioning
the times of vibration on board ship and on shore. When the ship's
head is cast and the times of vibration on board are too small in number
as compared with the times of vibration on shore, or when the ship's
licad is west and the times of vibration on board are too great in number
as compared with the times of vibration on shore, it is inferable that
with the ship's head north there would be an casterly deviation, and
that with the ship's head south there would be a westerly deviation;
and I then effect the correction through the application of rule V.
When the ship's head is cast and the times of vibration on board are
too great in number as compared with the times of vibration on shore,
or when the ship's head is west and the times of vibration on board
are too small in number as compared with the times of vibration on
shore, it is inferable that with the ship's head north there would be
a westerly deviation, and that with the ship's head south there would be
an casterly deviation; and I then effect the correction through the
application of Rule VI. If from any cause the operations have to be
carried out when the ship's head is placed cither north or south (correct
magnetic), I correct when advisable the "heeling" error by correctly
proportioning (through the application of Rules I. and II.) the times of
vibration of a dipping needle in a plane at right angles to the meridian
on board ship and on shore; also I correct (through the application of
Rules V. and VI.) that part of the "semicircular" deviation which is

page_text: caused by a force acting athwart-ship. The force acting in the fore and
aft line of the ship and causing the other part of the "semicircular "
deviation may be then observed by comparing the times of vibration of a
horizontal needle on board ship and on shore; and I correct the deviation
by correctly proportioning the times of vibration on board ship and on
shore. When the ship's head is north and the times of vibration on
board are too great in number as compared with the times of vibration
on shore, or when the ship's head is south and the times of vibration on
board arc too small in number as compared with the times of vibration
on shore, it is inferable that with the ship's head east there would be
an easterly deviation, and that with the ship's head west there would be
a westerly deviation; and I then effect the correction through the
application of Rule III. When the ship's head is north and the times
of vibration on board are too small in number as compared with the
times of vibration on shore, or when the ship's head is south and the
times of vibration on board are too great in number as compared with
the times of vibration on shore, it is inferable that with the ship's head
east there would be a westerly deviation, and that the ship's head west
there would be an easterly deviation; and I then effect the correction
through the application of Rule IV. Here too a vertical column or pillar
of soft iron may be sometimes employed for the purpose of correcting
that part of the "semicircular" deviation arising from vertical induction;
and when the ship's head is on one of the quadrantal points the "quad-
rantal" deviation may be corrected by placing soft iron rods, cylinders,
or chains athwart-ship at the level of and at each side of the compass.
I now give the six rules to which I have already made reference. Of
these rules I employ those numbered I. and II. in conjunction with
Figures 5 to 18 inclusive, and I employ those numbered III., IV., V.,
and VI. in conjunction with Figures 5 to 53 inclusive.
RULES. I. When the times of vibration on board ship are too great in
number as compared with the times of vibration on shore, convert the
deck-beam beneath the compass, if represented on any Figure by a thick
line, into a compound magnet of the 1st class.
II. When the times of vibration on board ship are too small in
number as compared with the times of vibration on shore, convert the
deck-beam beneath the compass, if represented on any Figure by a thick
ine, into a compound magnet of the 2nd class.

page_text: III. When the ship's head is east and the deviation east, or when the
ship's head is west and the deviation west, convert every deck-beam
represented on any Figure by a thick line into a "compound" magnet of
the 1st class if alıcad of the compass, and into a "compound" magnet
of the 2nd class if astern of the compass.
IV. When the ship's head is cast and the deviation west, or when
the ship's head is west and the deviation cast, convert every deck-beam
represented on any Figure by a thick line into a "compound" magnet of
the 2nd class if ahead of the compass, and into a "compound" magnet
of the 1st class if astern of the compass.
V. When the ship's head is north and the deviation cast, or when the
ship's head is south and the deviation west, convert every deck-beam
represented on any Figure by a thin line, whether ahead, bencath, or
astern of the compass, into a "simple" magnet of the 1st class.
VI. When the ship's head is north and the deviation west, or when
the ship's head is south and the deviation east, convert every deck-beam
represented on any Figure by a thin line, whether ahead, beneath, or
astern of the compass, into a "simple" magnet of the 2nd class.
The "secondary" conditions under which my Invention may have to be
carried out are various, but they will be fully understood and my Invention
will be readily adapted to them by any competent person conversant with
the subject and acquainted with the details of this Specification. It will
be perceived that the deck-beams shown on the Figures vary in number
and that the compass is represented in various positions with regard to
these beams. In some cases, owing in part to the number of available deck-
beams being limited, and in part to their position relative to the compass
being from different circumstances immutably fixed, there will be found
practically little or no room for the exercise of choice as to which of the
different arrangements herein referred to it may be best to adopt. When
however there are no such limitations, or when these occur only in part,
it may be well to bear in mind the two following points:-(1.) That it is
of more importance to have a considerable number of deck-beams on
which to operate when the deviations of a compass are great than when
they are small. (2.) That, according as that portion of the deviation
caused by a force acting athwart-ship is great or small in comparison
with that portion caused by a force acting in the fore and aft line of the
ship, the beams available for conversion into "simple" magnets should, as
compared with those available for conversion into "compound" magnets,

page_text: have (1) the advantage, or (2) the disadvantage, either (a) in number,
or (6) in proximity to the compass.
If, previous to correcting the deviations of a compass, I find that the
deck-beam or beams that I purpose polarizing in order to correct what
may be here termed the second part of the "semicircular" deviation
(i.c., that part thereof which I correct second) are so strongly magnetized
as to affect the compass, or if, in cases when the "heeling" deviation
has to be corrected after the correction of what may be here termed the
first part of the "semicircular" deviation (i.c., that part thereof which
I correct first) has been effected, I find that the beam I purpose
polarizing in order to correct the " liccling" crror is so strongly
magnetized as to affect the compass, I in some cases before proceeding
to correct the first part of the "semicircular" deviation so far tem-
porarily depolarize theso said beams (adopting the same principle as
that involved in the depolarization of a polarized bar) as to destroy
temporarily their effect on the compass.
In my Provisional Specification I have described certain improvements
in the construction of ships and vessels consisting of the introduction
(for the purpose of correcting and preventing compass deviations) of
either one or two concentric rings or segments of rings into the structure
of the decks of such ships or vessels, but in further developing the
working of my system I have found that the object I had in view may
be more economically and effectually accomplished without the employ-
ment of such rings or segments of rings and by the employment of the
means herein-before described.
In my Provisional Specification I have described a mode of employing
(for the purpose of correcting and preventing compass deviations) my
system of polarization in combination with that of depolarization; but
in further developing the working of my system I have found that the
object I had in view may be more economically and effectually accom-
plished without the employment of the above referred to system of
depolarization in combination with my system of polarization and by
thic employment of the means herein-before described.
Having now described my system of correcting and preventing the
deviations of a compass I would have it understood that although I have
defined a mode of proceeding through the application of certain rules,
which mode of proceeding will, I believe, suffice to meet the generality
of the conditions under which my system may have to be carried out,

page_text: still there may be other conditions which are not precisely provided for
in the foregoing description and diagrams; in all such cases however the
description and diagrams herein-before given will readily enable any
competent person to adapt my system to these other conditions; and I
therefore claim as my Invention,―
The process of treating iron, steel, or composite ships or vessels to
correct and prevent compass deviations by polarizing on a regulated
system such parts of the ships or vessels as may be requisite.
In witness whereof, I, the said John Ward Girdlestone, have here-
unto set my hand and seal, this Twenty-fourth day of September,
in the year of our Lord One thousand eight hundred and sixty-
nine.
JOHN WARD GIRDLESTONE. (L.S.)