Improvements in Instruments for Measuring and Adjusting Magnetic Force.
Year: 1891

page_text: Date of Application, 16th Mar., 1891
Complete Specification Left, 18th Jan., 1892-Accepted, 12th Mar., 1892
PROVISIONAL SPECIFICATION.
Improvements in Instruments for Measuring and Adjusting
Magnetic Force.
1, WILLIAM MAYES of 43 Tressillian Road, St. Johns in the County of Kent,
a retired Captain in the Royal Navy do hereby declare the nature of my invention
to be as follows :-
My invention relates to improvements in instruments for measuring magnetic
force and adjusting the same on board ship and has for its object the arrangement
& construction of such an instrument in a simple and inexpensive form so as to be
used instead of the two expensive instruments now in use riz. one instrument for
measuring the horizontal component of the force and another for measuring the
vertical component of the same.
These two results I can obtain from my improved instrument, in such a manner
that I can exactly measure the horizontal component of the force and the vertical
component as far as it is necessary for the purpose of compass adjustment.
I carry out my invention as follows:-
Within a suitable box having a transparent lid or cover I arrange a central
pivot or support having a sharp point preferably of iridium.
Upon this said point I mount a magnetic needle of special construction.
This needle has a jewelled cap preferably of sapphire at its centre and is so
mounted on this said cap as to be capable of movement about a horizontal axis in
a vertical plane.
Near the centre of the needle I arrange upon each half of the needle an
adjustable balance weight, these may be nuts threaded upon a screw thread.
These balance weights can be so adjusted as to balance the needle horizontally.
When so balanced under the effect of terrestrial magnetism any dipping of the
needle indicates the presence of another magnetic force if the instrument is the
same latitude as when originally balanced or if in another latitude an alteration in
the vertical component of the terrestrial magnetic force.
On the bottom of the box is placed a circle divided at the circumference into
degrees by means of which the direction of the ship's head may be known by the
position of the needle relative to the scale in the usual manner.
When not required for the before mentioned purposes the needle is placed in
rests situated on the sides of the box so as not to unnecessarily wear the points.
When this situated the instrument may be used to measure horizontal force
at a compass by the amount of deflection caused therein by the needle of the
instrument.
The transparent lid or cover may be capable of revolution on the top of the box,
and have engraved or cut diametrically across it a straight line for the purpose of
ascertaining the compass bearing of any object by referring it to the direction of
the needle.
I use my improved instrument as follows:-
When the needle is resting on its pivot and is brought horizontal by the adjust-
ment of the balance weights at any place on shore, it indicates that the earth's
vertical force is counteracted by the balance weights.
When placed on board ship at the same place, and in the position of any compass,
if the needle dips from the horizontal, it indicates that there is a vertical force due
to the ship which would cause heeling error.
By bringing the needle again horizontal by means of a vertical magnet under it
this force will be counteracted.
For this purpose the needle may be used on its own pivot or on the compass
pivot, but in any case the correcting magnet must be situated at the same distance

page_text: from the compass needles as it was from the instrument needle when the latter was
brought horizontal.
If the position of the correcting magnet be thus determined in two places wide
apart in latitude, its position in any intervening latitude may be approximately
known.
The needle may be used on its own pivot in the instrument or in any compass to
measure horizontal force by vibration.
The zeros on the bottom of the box being placed fore & aft by means of the line
on the lid, the position of the needle shows the bearing of the ship's head.
Also if the instrument be placed on a compass with the needle in its rests and
at right angles to the compass needles horizontal force may be measured by
deflection.
Dated this 16th day of March 1801
FELL & WILDING,
1, Queen Victoria Street, London, E.C., Agents for the Applicant.
COMPLETE SPECIFICATION.
Improvements in Instruments for Measuring and Adjusting
Magnetic Force.
I, WILLIAM MAYES of 43 Tressillian Road St. Johns in the County of Kent, a
retired Captain in the Royal Navy, do hereby declare the nature of my invention
and in what manner it is to be performed to be particularly described and
ascertained in and by the following statement:
My invention relates to improvements in instruments for measuring magnetic
force and adjusting the same on board ship, and has for its object the arrangement
and construction of such an instrument in a simple and inexpensive form, so as to
be used instead of the two expensive instruments now in use, viz. :-one instru-
ment for measuring the horizontal component of the force, and another for
measuring the vertical component of the same.
These two results I can obtain from my improved instrument in such a manner
that I can exactly measure the horizontal component of the force, and record by
balance of the needle the vertical component, as far as it is necessary for the
purpose of compass adjustment.
In order that my invention may be the better understood I will now describe it
in relation to the drawings hereunto annexed, reference being had to the letters and
figures marked thereon
Fig. 1 is a plan of my instrument with the needle suspended on its pivot.
Fig. 2 is a vertical section of the same.
Fig. 3. is a plan of the instrument with the transparent lid removed, and the
needle supported in its rests.
I carry out my invention as follows :-
Within a suitable box A having a transparent lid or cover BI arrange a central
pivot C having a sharp point preferably of iridium.
Upon this point C I mount a magnetic needle D of special construction.
This needle D has a jewelled cap E (preferably with a sapphire) at its centre,
and, the needle D is mounted upon its cap E so as to be capable of movement
about a horizontal axis in a vertical plane, which I effect by pivots F which pass
loosely through the side lugs G of the needle situated upon each side of the
hole which is formed in the centre of same, the said pivots F being supported in
the cap E.
Upon each side of the centre of the needle DI arrange an adjustable balance
weight K which I prefer to make in the form of a nut running upon screwed pins,
situated within the hole II, the said screwed pins being attached to the extremities
of the hole H and extending inwards towards the centre of the needle.
By these means the needle can be balanced horizontally.

page_text: When so balanced under the effect of terrestrial magnetism in one particular
place, any subsequent dipping indicates the presence of another magnetic force
such as that due to the proximity of magnetic material if the instrument is in the
same latitude as when originally balanced, or if in another latitude, an alteration
in the vertical component of the terrestrial magnetic force.
Around the case AI arrange a ring L divided into degrees or other divisions by
means of which the direction of the ship's head may be known by the position of
the needle relative to the scale, in the usual manner.
When not required for the before mentioned purposes, the needle D is placed
upon supports situated on the sides of the box, so as not to unnecessarily wear
the pivot C.
When thus situated the instrument may be used to measure horizontal force
at a compass by the amount of deflection caused therein by the needle of the
instruinent.
The transparent lid or cover may be capable of revolution on the top of the
box, or may have a definite position thereon, and have engraved or cut diametrically
across it one or more straight lines M, coinciding with the cardinal points on the
ring, for the purpose of ascertaining the compass bearing of any object by
referring it to the direction of the needle.
I use my improved instrument as follows:-
When the needle D is resting on its pivot C and is brought horizontal by the
adjustment of the balance weights K at any place on shore, it indicates that the
earth's vertical magnetic force is counteracted by gravity, through the balance
weights K.
When placed on board ship in close proximity to the same place and in the
position of any compass, if the needle dips from the horizontal it indicates that
there is a vertical force due to the ship which would cause heeling error.
By bringing the needle again horizontal by means of a vertical magnet under
it, this force will be counteracted.
For this purpose the needle may be used on its own pivot or on the compass
pivot but in any case care must be taken that the correcting magnet is at
the same distance from the compass needles as it was from the instrument needle
when the latter was brought horizontal.
If the position of the correcting magnet be thus determined in two places wide
apart in latitude, its position in any intervening latitude may be approximately
known.
The needle may be used on its own pivot in the instrument or in any compass to
measure horizontal force by vibration."
The zero marks on the ring being placed fore and aft, by means of the line on
the lid the position of the needle shows the bearing of the ship's head.
Also, if the instrument be placed on a compass with the needles in its rests
and at right angles to the compass needles, horizontal force may be measured by
deflection.
Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed I declare that what I
claim is
1st. An instrument for measuring magnetic force consisting of a case with a
transparent lid having a line or lines diametrically across the face, a pivot within
the said case, and a magnetic needle adapted to turn upon the said pivot and also
about a horizontal axis in a vertical plane, the said needle having means for
adjusting its balance.
2nd. In such an instrument for measuring magnetic force a needle having a
pivotting cap pivotably attached to it, so as to allow the needle to rotate about a
horizontal axis in a vertical plane and a balance weight or weights mounted as
nuts on screwed supports on the needle substantially as described.
3rd. In such an instrument for measuring magnetic force, a needle as claimed

page_text: in Claim 2 in combination with a graduated ring around the case within which the
necale is pivotted, and a transparent cover having lines diametrically disposed
across its face, substantially as described.
4th. The construction and arrangement of an instrument for measuring magnetic
force, substantially as described and illustrated in the accompanying drawings.
Dated this 18th day of January 1892.
FELL & WILDING,
1, Queen Victoria Street, London, E.C., Agents for the Applicant.