IMPROVEMENTS IN APPARATUS FOR THE ADJUSTMENT OF MAGNETIC NEEDLES
Year: 1875

page_text: LETTERS PATENT to George Tomlinson Bousfield, of Sutton, in the
County of Surrey, for the Invention of " IMPROVEMENTS IN APPARATUS
FOR THE ADJUSTMENT OF MAGNETIC NEEDLES."-A communication from
abroad by George Iles, of the City of Montreal, in the Province of
Quebec, Canada.
PROVISIONAL SPECIFICATION left by the said George Tomlinson
Bousfield at the Office of the Commissioners of Patents, with
his Petition, on the 24th June 1875.
I, GEORGE TOMLINSON BOUSFIELD, of Sutton, in the County of
Surrey, do hereby declare the nature of the said Invention for "IK-
PROVEMENTS IN APPARATUS FOR THE ADJUSTMENT OF MAGNETIC NEEDLES,” to be
as follows:-
The object of this Invention is more particularly to afford an easy,
quick, and certain means of adjusting the compasses of any ship in
which may exist a disturbing influence on the magnetic needle, whether

page_text: such influence be due to the material of which the ship is constructed,
its cargo, or machinery, or their movements. It enables the exact
amount of the deviation at any particular time from the above-mentioned
causes to be at once ascertained and compensated for, so that the
navigator may place perfect confidence in his compasses, especially in 5
fog, and such times when they are most needed, and be able with the aid
of his charts to "lay" his course exactly. The necessity for swinging
the ship in port is also done away with.
Although primarily adapted to compasses on ships my Invention may
be applied to those used in exploration, surveying, &c., and to magnetic 1
needles of any kind, for whatever purpose they may be employed.
-
The means which I adopt to attain these objects are as follows :-
Above or below an ordinary compass needle, and having its centre
coincident with that of the needle, is delicately poised a bar of practically
non-magnetic metal, preferably provided with a bell cap over it to 1
prevent vibration in a vertical plane. Upon this bar are fitted in any
suitable way at right angles across it as many minute magnets of like
poles together as may come together without undue mutual influence
between themselves, the bar thus arranged being practically a magnet
pointing E. and W., and in its normal condition at right angles with the 20
compass needle. It is absolutely necessary that the three planes of
division of this bar shall bisect equal quantities in bulk, weight, and
magnetic force, and it is also desirable that the amount of magnetic
force in this bar and the compass needle shall be equal.
The operation of the Invention may be thus illustrated:-Supposing 20
a disturbing object to be N.E. of the compass, the N. pole of the needle
will incline in that direction, as also the E. end of the bar, thus making
the angle formed by the bar and needle in the N.E. less than a right
angle.
An iron or steel compensator suitably placed either at 8.E. or N.W. 80
will restore the parts to their normal position, the compensator as it is
smaller than the disturbing object requiring to be nearer the axes of the
bar and needle in the inverse ratio of the square of the distance. This
apparatus may be attached to any approved kind of compass, such for
instance as that termed the "spirit immersion compass."
85

page_text: 4953
Patent Office on the 23rd December 1875.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, GEORGE
TOMLINSON BOUSFIELD, of Sutton, in the County of Surrey, send
greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Twenty-fourth day of June, in the
year of our Lord One thousand eight hundred and seventy-five, in the
thirty-eighth year of Her reign, did, for Herself, Her heirs and suc-
cessors, give and grant unto me, the said George Tomlinson Bousfield,
Her special license that I, the said George Tomlinson Bousfield, my exe-
cutors, administrators, and assigns, or such others as I, the said George
Tomlinson Bousfield, 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 "IMPROVEMENTS IN APPARATUS FOR THE ADJUSTMENT OF MAGNETIC
NEEDLES," a communication to me from abroad by George Iles, of the
Oity of Montreal, in the Province of Quebec, Canada, upon the condition
(amongst others) that I, the said George Tomlinson Bousfield, my exe-
cutors 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 George Tomlinson Bousfield, 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 :—
The Invention has reference to means used to ascertain more par-
ticularly in mariners' compasses the aberration of any magnetic needle
due to local attraction in the ship, its cargo, or machinery, and also for

page_text: and the reason that it is by preference built up to carry a large number
of small magnets is that the magnetic force may be distributed over its
whole body, instead of being as in the ordinary needle concentrated at
one or two points.
A
very convenient construction of this needle is shown in Figures 1,
2, and 8, in which the needle A is formed of two parallel bars a, a, of
aluminium or other practically non-magnetic metal, joined together by
transverse bars a', a', of like substance, carrying both on their upper
and under edges the magnets 6, as above described.
D is a bar of non-magnetic metal, as just described, pivotted on any
suitable axis concentrically with the needle A, and being in its normal
position exactly at right angles to it. Upon this bar D are secured any
required number of small magnets d-with like poles pointing one way
placed across the bar as closely together as possible without undue
influence between themselves. It is absolutely necessary that the
amount of the magnetic force in the bar D should be equal to that of
the needle A, and that in this bar D also the three planes of division
shall bisect equal quantities in weight, bulk, and magnetic force.
Immediately above D and at right angles to it may be secured a
wire E, shown in Figure 3, of aluminium or like metal of equal length
with the bar D, and serving for more convenient comparison with the
bar or needle A. The distance between the bar D and needle A is to
be as little as may be left without causing undue influence between
them.
F, F, are bell caps placed, as usual, respectively above the needle A
and bar D to prevent vertical vibration, G being a compass bowl of any
ordinary construction and hung in the usual way; H is the dial plate
divided as usual and placed most conveniently between the needle A
and transverse bar D.
The operation of the Invention will be easily understood, and may be
thus explained:-Presuming that the cause of disturbance lies in
the N.E. the needle will be deflected in that direction, i.e., eastwardly,
and the transverse bar D, which is practically a magnet pointing E.
and W., will also turn towards the disturbing cause, thus making the
angle between the needle A. and bar D in that direction and the one
opposite to it less than a right angle.

page_text: The way in which it is proposed to compensate for this attraction and
to restore the bar or needle, not only to their normal angle of 90°, but
also to their former position, is by means of a steel compensator placed
when in use so that similar or repelling poles of the compensator or
compass are nearest together. This compensator is brought toward the
axis of the compass along a radial line 1 bisecting either acute angle
until 90° is marked, the relative movements of the needle A and bar D
being noted. The compensator is then gradually moved towards the
more inert point 90°, being maintained until lines drawn from centre of
repulsion (marked O) to each of the two immediately affected halves of
the bars shall be found to correspond as the square root of the original
aberration of such point. Thus if N. has been found to have been
disturbed before compensation 4°, and E. 1°, the centre of compensator
must be joined by lines of the proportions shown by Y, Z, (i.e., as 1
and 2) drawn to the two bar halves.
In very rough weather if the longitudinal bar or magnetic needle A
and the transverse bar D are found to be exercising undue influence over
each other one may be removed and the aberration of the other com-
pensated for, and vice versa, by the rules already given. This device
may be used in combination with any approved form of compass, and if
desired the bars may be made hollow and immersed in spirit, as in
Ritchie's compass.
It must be clearly understood that it is not proposed to ascertain and
.compensate for the deviation of the magnetic needle due to earth currents
or other cosmical influence, but what is claimed as the Invention and
desired to be secured by Letters Patent is as follows :―
First. The transverse bar D carrying many minute magnets placed
with like poles one way, and being practically a magnet pointing E.
and W. attracted towards a piece of iron like an ordinary magnetic
needle, as shown and described.
Second. In combination with any compass the longitudinal bar
carrying many minute magnets of like poles pointing one way, and
acting as a magnetic needle, as shown and described.
Third. In any compass the combination of the longitudinal bar A.
and transverse bar D equally attracted by any object, substantially as 3
described.

page_text: Fourth. The use in combination with the longitudinal bar or needle A
and transverse bar D of a compensator, working as described according
to known rules, the whole as set forth.
In witness whereof, I, the said George Tomlinson Bousfield, have
hereunto set my hand and seal, this Twenty-second day of
December, in the year of our Lord One thousand eight hundred
and seventy-five.