IMPROVEMENTS IN CARDS AND MAGNETIC NEEDLES FOR MARINERS' COMPASSES
Year: 1881

page_text: LETTERS PATENT to Herbert John Haddan, of the Firm of Herbert and
Company, Solicitors of Patents, of 67, Strand, in the City of Westminster,
Civil Engineer, for an Invention of " IMPROVEMENTS IN CARDS AND MAGNETIC
NEEDLES FOR MARINERS' COMPASSES." A communication from abroad by
John Lewis and Frederick Augustus Brown, both of the State of Massachusetts,
United States of America.
PROVISIONAL SPECIFICATION left by the said Herbert John Haddan at the
Office of the Commissioners of Patents on the 28th February 1881.
"
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HERBERT JOHN HADDAN, of the Firm of Herbert and Company, Solicitors of
Patents, of 67, Strand, in the City of Westminster, Civil Engineer. IMPROVEMENTS
IN CARDS AND MAGNETIC NEEDLES FOR MARINERS' COMPASSES.' A communication
from abroad by John Lewis and Frederick Augustus Brown, both of the State of
Massachusetts, United States of America.
The first part of this Invention relates to the magnetic needle of the mariners”.
compass card, and consists in constructing such needle tapering at its poles and
rectangular between them and slotted in its body between such poles and the
pivotal bearing of such needle. The inventors have found by experiments that a
magnetic needle when so made is highly sensative, or quicker in action, and very.
reliable in comparison with many other forms of such needles.
The second part of this Invention is for the purpose of preventing the needle
from being affected by local attractions or by a mass of iron when in its vicinity,
and this is accomplished by combining with the needle and the card or circular:
plate to which the needle is attached a series of "U magnets," or a series of sets
of "U magnets," arranged at proper distances apart with their axes in lines
radiating from the centre of the card, and with the north pole of each of such
magnets toward the south pole of the needle.
The inventors have found that when the two magnets or sets which are at right
angles to the needle are stronger in their magnetic power than each of the flanking
magnets, not only are the effects of local attraction neutralized, but the card or
magnetic needle becomes quicker to operate and more sensitive and accurate.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said Herbert John Haddan in the Great Seal Patent Office on the
26th August 1881.
HERBERT JOHN HADDAN, of the Firm of Herbert and Company, Solicitors of
Patents, of 67; Strand, in the City of Westminster, Civil Engineer. "IMPROVEMENTS
IN CARDS AND MAGNETIC NEEDLES FOR MARINERS' COMPASSES." A communication
from abroad by John Lewis and Frederick Augustus Brown, both of the State of
Massachusetts, United States of America.
Reference being had to the accompanying Drawing, which denotes an
underside view of a compass card with this Invention applied to it. The
first part of this Invention relates to the magnetic needle of the mariner's
compass card, and consists in constructing such needle tapering at its poles, and
rectangular between them and slotted in its body between such poles and the
pivotal bearing of such needle, the inventors having found by experiments that a
magnetic needle when so made is highly sensitive or quicker in action, and very
reliable in comparison with many other forms of such needles. The second part of
this Invention is for the purpose of preventing the needle from being affected by
local attractions or by a mass of iron when in its vicinity, and this is accomplished
by combining with the needle and the card or circular plate to which the needle is
attached a series of "U magnets" or a series of sets of "U magnets," arranged at
proper distances apart with their axes in lines radiating from the centre of the card,
and with the north pole of each of such magnets toward the south pole of the
needle, all being substantially as shown in the aforesaid Drawing, in which A
denotes the magnetic needle; a, a, the longitudinal slots thereof; B, the card or
. divisional plate, which in this case is shown as a flat annulus; D, D, etc., are the
sets of auxiliary "U magnets," there being six of such sets in all, which in practice
the inventors have found to be generally sufficient. The number however may be
increased if necessary, and there may be two or more of such magnets in each set.
The inventors have found that when the two magnets or sets which are at right
angles to the needle are stronger in their magnetic power than each of the flanking
magnets, not only are the effects of local attraction neutralized, but the card or
magnetic needle becomes quicker to operate and more sensitive and accurate.
While the inventors do not pretend to explain the causes of such, they have found
such results to be obtained in practice. In the Drawing two "U magnets are
shown to each set, except at the east and west points of the card, where there are
three of such magnets in each of the sets, the magnets being marked m. Through
tests of a compass card made in accordance with this Invention the inventors have
proved it not affected by local attraction, such as it would be ordinarily subjected
to on land or shipboard. I am aware that a magnetic needle having a lozenge
form, having a triangular opening in each arm is not new. Also that it is not new
to have to a compass-card and its needle a series of bar or plate magnets arranged
radially and at equal or about equal distances apart, and having their north poles
toward the south pole of the needle, their south poles being toward the north pole
of the magnet. There are distinctive differences between such and this Invention,
as in carrying out the latter the inventors employ "horseshoe" or "U magnets
with the two poles of each at the circumference of the circle of compensatory
magnets, whereby all the poles of the magnets as well as those of the needle are
brought in one circumference, and not only this, but the south pole of each magnet
or set of magnets is placed between two north poles of the next adjacent sets, all
of which the inventors have found in practice to be productive of results
unattainable from bar or plate magnets arranged radially on a card and flanking
its needle. I would also remark that a magnetic needle made as is theirs, viz., of
a rectangular bar tapered at its poles, and having a rectangular slot in each arm, is
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page_text: preferable to the lozenge needle as above mentioned, it being capable of being
magnetized much stronger at its poles:
What I claim is as follows, viz. :-
1. A magnetic needle tapering at its poles, and rectangular in shape between
them and slotted in its body, as set forth.
2. A mariner's compass-card having a magnetic needle and provided with
"horseshoe" or "U magnets" arranged on the card circumferentially, and with all
their poles in or about in the circumference of a circle, concentric with the card,
and having the north pole of each magnet toward the south pole of the magnetic
needle of such card.
3. A mariner's compass-card having a magnetic needle, and provided with
"horseshoe" or "U magnets" arranged on it, the said card, circumferentially, and
with all their poles in or about in the circumference of a circle concentric with the
card, and having the north pole of each magnet toward the south pole of the
needle, and the magnets of the east and west points stronger in their magnetic
power than either of the others or sets thereof, all being essentially as specified.
In witness whereof, I, the said Herbert John Haddan, have hereunto set
my hand and seal, this Eighteenth day of August, A.D., 1881.
H. J. HADDAN. (L.S.)