IMPROVEMENTS IN THE MEANS OF AND APPARATUS FOR INDICATING THE DIVERGENCE OF MAGNETISED NEEDLES
Year: 1883

page_text: LETTERS PATENT to George Colleton Cooke of Sutton in the County of Surrey.
for an Invention of "IMPROVEMENTS IN THE MEANS OF AND APPARATUS FOR
INDICATING THE DIVERGENCE OF MAGNETISED NEEDLES
PROVISIONAL SPECIFICATION left by the said George Colleton Cooke at
the Office of the Commissioners of Patents on the 1st May 1883.
GEORGE COLLETON COOKE, of Sutton, in the County of Surrey, " IMPROVE-
MENTS IN THE MEANS OF, AND APPARATUS FOR, INDICATING THE DIVERGENCE OF
MAGNETISED NEEDLES."
"
My invention relates to magnetic and electro magnetic needles, whether used for.
compasses or telegraphic or other scientific instruments, and is designed to provide
inter alia an automatic indicator either of the abnormal divergence of such
magnetic or electro magnetic needles when caused by magnetic disturbance, as is
frequently the case; or of changes in electric or magnetic currents whether in
their character, force, or direction; or for relays on such electric or magnetic
circuits etc.
It is known that when two magnets are closely approximated to one another.
that, their like poles mutually react and produce a so-called astatic condition, but
to carry out my
invention I use one or more subsidiary magnetic needles, carried:
beyond this astatic influence from a main magnetic needle or needles, so that the
main and subsidiary needles all similarly point with like poles to the true
terrestrial magnetic meridian, when unaffected by any magnetic or local
disturbance.
I find moreover that there is a zone surrounding any magnet in which subsidiary
magnets will be affected by a contrary induced polarity to that of the main magnet,
when caused by any magnetic or local disturbance.
My invention thus consists of the combination of a subsidiary magnet or magnets
with a main needle or needles so that the said subsidiary needle or needles lie in
this zone of contrary induced polarity, to that of the main magnet, and shall be,
affected by a divergence opposite to or distinct from that of the main needle or
needles, caused by any magnetic or local disturbance. Thus, by a co:nparison
of the said opposite or distinct divergences, the true terrestrial magnetic meridian
may still be deduced with certainty, and further the said contrary divergences
caused by a passing current may be utilized for a variety of purposes.
C

page_text: My apparatus is susceptible of various applications in a variety of alternative
forms, by which the action and re-action as above described between the main and
subsidiary magnets may be utilized, but the following arrangements may be taken
as examples.
I may use a single subsidiary magnetic needle or combination needle, floating or
exactly pivoted at its centre of gravity upon the usual needle point, concentrically
above the main single or combination magnet, which is suspended or similarly
floated in the usual way.
The upper subsidiary magnetic needle or needles, may if necessary, or convenient,
be made of a lighter and smaller bar or bars, having their dimensions throughout
smaller than those of the main magnet. This upper subsidiary magnetic needle is
supported by any convenient frame at a distance above the main magnet, which
must in every case be accurately found by direct experiment, and can be set by
screw or other adjustments in the framing.
ht
In this arrangement the effect of magnetic disturbance is to deflect both the main
and subsidiary needles through equal angles in opposite directions to the magnetic
meridian.
The true magnetic meridian can then be readily found at all times by taking
the mean of the two readings indicated by the main and subsidiary needles.
'I may alternatively arrange the subsidiary magnet concentrically with, but
below, the main magnet, in which position also opposite deflections of the two
needles will be produced by magnetic disturbance.
Again I may use two subsidiary magnets, smaller if convenient, than the main
magnet, arranged above or below and one on each side of the centre of the main
magnet, so that the three magnets are situated at the corners of a vertical triangle,
the main magnet being at the single apex vertically downwards or upwards, at
a vertical distance, as before described.
In this case also the angles of deflection of the subsidiary needles, when
disturbed by magnetic induction, are individually distinct from that of the main
magnet, and will allow of an accurate deduction as to the position of the true
magnetic meridian."
5"
And further, I may suspend two principal magnets below or above the subsidiary
magnet, the two principal magnets set at a suitable distance apart, so as to form
with the subsidiary magnets a triangle as just described; or I may set two sub-
sidiary magnets one on either side of the centre principal magnets at the proper
distance apart, but all three magnets in the same horizontal plane.
It will be seen from my fore-going description, that so long as subsidiary magnets
are placed in the zone of opposite polarity to that of the main magnet, a variety of
various distinctive readings may be obtained, according to the number and position
of the subsidiary magnets in that zone.
+
I do not therefore confine myself to the number and exact position, in the zone
of opposite polarity, of the subsidiary magnets, which I may employ in combination
with the main magnet, to give distinctive readings from any magnetic disturbance,
from which the true terrestrial magnetic meridian may be deduced, inasmuch as
any such arrangement produces an equivalent operation and means of deduction
with any of those that I have described for the sake of example.
In electric or magneto-electric current indicators and relays, the helices may be
wound in the various manners proper to such instruments, either both in the same
or opposite directions, and in series, or both in the same or opposite direction and
in parallel circuit, so as to produce the required induced field of opposing polarity
whereby the divergence of the needles is effected; and in relays the needles would
be provided with the needful contact points, and would be duly insulated.
I

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said George Colleton Cooke in the Great Seal Patent Office on the
31st October 1883.
GEORGE COLLETON COOKE, of Sutton, in the County of Surrey,
" IMPROVE.
MENTS IN THE MEANS OF AND APPARATUS FOR INDICATING THE DIVERGENCE OF
MAGNETISED NEEDLES
."
My invention relates to magnetic and electro magnetic needles, whether used
for compasses or telegraphic or scientific instruments, and it is designed to provide
inter alia an automatic indicator either of the abnormal divergence of such
magnetic or electro magnetic needles when caused by magnetic disturbance as is
frequently the case, or of changes in electric or magnetic currents, whether in
their character force or direction.
It is known that when two magnets are closely approximated to one another
that their like poles mutually re-act and produce a so-called astatic condition, but
to carry out my invention I use one or more subsidiary magnetic needles, carried
beyond this astatic influence from a main magnetic needle or needles, so that the
main and subsidiary needles all similarly point with like poles to the true
terrestrial magnetic meridian when unaffected by any magnetic or local
disturbance.
I find moreover that there is a complete enveloping zone surrounding any
magnet, of limited extent and defined position beyond that of mutual astatic
influence, in which subsidiary magnets will maintain their usual polarity, indicative
of the terrestrial meridian when unaffected by local or magnetic disturbance, but
which will be affected by a contrary induced divergence to that of the main
magnet, when influenced by any magnetic or local disturbance.
In order that my invention may be the better understood I append drawings
hereto, illustrative diagrammatically of the variety of arrangements in which the
effects of the zone of contrary divergence may be utilized, and giving also one
convenient practical form in which my improved device may be applied, for ships'
purposes, as a standard compass to indicate and measure magnetic disturbance,
when placed at a convenient distance above the hull, so that the disturbing force
may be below the main magnet.
Figure 1 shows diagrammatically an end view of a magnet A surrounded by a
definite though limited zone of induced opposite divergence shown by the two
circles B B. At C, C, C³, &, we show subsidiary magnets, which it is evident
may be placed at any point in the said circular zone, where their usual polarity
indicative of the terrestrial meridian when unaffected by local magnetic disturbance
remains the same as that of the main magnet A, but they are all similarly affected
by a contrary induced divergence to that of the main magnet when influenced by
any magnetic local disturbance.
My invention thus consists of the combination of a subsidiary magnet or magnets
with a main magnetic needle or needles, so that the said subsidiary magnet or
magnets lie anywhere in this zone of opposite induced divergence, outside the area
of mutual astatic influence, and shall be affected by a divergence opposite to, or
distinct from, that of the main needle or needles, caused by any magnetic local
disturbance. Thus, by a comparison of the said opposite or distinct divergences,
the true terrestrial magnetic meridian may still be deduced with certainty, the
meridian being usually, when the correct position in the exterior zone has been
arrived at, exactly a mean between the said opposite divergences. Should
however the subsidiary needle or needles have a larger or smaller ratio of

page_text: divergence than that of the larger needle in the opposition direction, that ratio can
be conveniently determined by experimental disturbance, and the true measure of
departure of the main needle from the meridian thus deduced and indicated.
My apparatus is susceptible of various applications in a variety of alternative
forms, by which the action and reaction as above described between the main and
subsidiary magnets may be utilized, but the following arrangements may be taken
as examples.
ہے
At Figures 2 and 3 I show, in sectional elevation and plan, a convenient
arrangement for a Standard Ship's Compass. A is a main single or combination
magnetic needle, suspended in a swinging frame D, upon a needle point E. The
said needle point E is the termination of a rod F, screwed or otherwise attached
to the elongated cylindrical case or frame G. This case G is dropped into the
ordinary compass bowl H, swung between gimbals, and covered with a transparent
glass plate K.
* 1
The frame D of the lower needle A. terminates in a screwed spindle L, upon
which a cap M is screwed, carrying another, needle point O and an annular dial N
engraved with the usual compass points. Upon the needle point O is floated a
subsidiary magnetic needle or needles P, which may conveniently be of the same
or lighter section and about one third the length of the magnet A. To the
needle Pis attached the dial Q, also marked, with the usual compass points or
otherwise graduated as necessity may require.
'
"
By reason of the screw attachment L the upper magnet P can be accurately
adjusted, by trial to the exact position within the zone of contrary induced
divergence surrounding the main magnet, A.:
"
"
+91
1.
By the arrangement adopted of the dial, N being supported on the cap L, the
adjustment of the plane of the upper magnet, relatively to the lower one, does not
disturb the relative, levels of the two. dials...:
... 3442 "
II.
1
When the needles are, unaffected by magnetic, disturbance, both needles and
dials coincide in their indication, of, the magnetic meridian. But 180, soon..as
contrary divergences are induced by, magnetic disturbance the distinctive readings
on the two dials are strikingly obvious, from their juxta-position in one plane, and
the deduction as to the true meridian is thus easily made..
I may alternatively arrange the, subsidiary magnet concentrically with, but
below, the main magnet, as at A and C, Figure 1, in which position also similar
opposite deflections will be caused by magnetic disturbance.
Again, I may use two subsidiary magnets, conveniently smaller than the main
magnet, arranged above or below and one on each side of the centre of the main
magnet, so that the three magnets are situated at the corners of a vertical triangle,
the main magnet A, Figure 1, being at the single apex vertically downwards or
upwards, and with the two subsidiary magnets as at C, C, or at C₁ C7, at the
other corners in the zone B, B' of opposite induced divergence.
In this case also the deflections of the subsidiary needles, when affected by
magnetic disturbance, are parallel to each other, and opposite to that of the main
magnet, allowing of an accurate deduction as to the position of the true magnetic
meridian.
L
Again I may set two subsidiary magnets C, Ca, Figure 1, one on either side of
the centre principle magnet in the same horizontal plane, the subsidiary magnets
being as before in the required zone and giving parallel and distinctive opposite
divergences to that of the main magnet.
It will be seen from my foregoing description that so long as subsidiary magnets
are placed in the zone of opposite divergence to that of the main magnet, and more
remote than the main magnet in the direction of disturbance, a variety of
distinctive readings may be obtained according to the number, and position of the
subsidiary magnets in that zone.
I do not therefore confine myself to the number and exact position in the zone
of opposite divergence of the subsidiary, magnets, which I may employ, in combi-
pation with my main magnet, nor do I lay claim to any employment of subsidiary

page_text: magnets inside or outside the before described zone, as for instance where the
subsidiary needles are astatically governed by the main needle so as to have their
poles reversed or neutralized whilst unaffected by disturbance, as this I am aware
has been already used, but what I claim and desire to protect by Letters
Patent is :-
First. The combination of a main magnetic needle or needles with a subsidiary
magnetic needle or needles, the latter placed in a defined zone of opposite induced
divergence, their polarity indicative of the magnetic meridian when undisturbed
remaining the same, but their divergence. being opposite to that of the main
magnet upon magnetic disturbance taking place, substantially as and for the
purposes specified.
Second. The construction and method of adjustment of the combination
Standard. Compass, substantially as described in relation to Figures 2. and 3
In witness whereof I, the said George Colleton Cooke, have hereunto set my
hand and seal this twenty ninth day of October in the year of our Lord One
thousand eight hundred and eighty three.
213
2
Witness:
RICHARD A. HOFFMANN,
23 Rood Lane
London E.C.
GEO. C. COOKE