IMPROVEMENTS IN LOCAL MAGNETIC ATTRACTION INDICATORS."
Year: 1872

page_text: LETTERS PATENT to Henry Glover, of Brooklyn, in the State of New
York, United States of America, for the Invention of "IMPROVEMENTS
IN LOCAL MAGNETIC ATTRACTION INDICATORS."
PROVISIONAL SPECIFICATION left by the said Henry Glover at the
Office of the Commissioners of Patents, with his Petition, on the
7th March 1872.
I, HENRY GLOVER, of Brooklyn, in the State of New York, United
States of America, do hereby declare the nature of the said Invention
for "IMPROVEMENTS IN LOCAL MAGNETIC ATTRACTION INDICATORS," to be as
follows:-
Marine and other compasses are very often deflected by local attraction
from the magnetic meridian, and these deflections frequently lead to
grave errors in calculations and often to accidents. This is particularly
the case with iron vessels, and the various compasses on such vessels
are tested and the local influence allowed for, but as this influence some-
times varies and may change according to the course the ship is running
it becomes of the utmost importance to obtain an instrument that will
indicate the extent of local attraction.
Compasses have been made with a variety of appliances, such as

page_text: primary and secondary needles and magnets, but in consequence of the
varying positions of the parts to the local attractions and magnetic
influences they frequently become changed in the extent or polarity.
My improvement is not a compass, its construction is such as to
absolutely preclude its use as such; my instrument is simply an
indicator to ascertain local attraction in order that in reckoning by the
ordinary compas the local attraction may be allowed for, and this
nstrument is so constructed that it may be adjusted from time to time,
and when positioned near an ordinary compass or in the place to be
occupied by such compass will indicate the number of degrees variation
that will be produced in that compass by the local attraction.
I make use of two needles or magnets, one a swinging needle or
indicator, the other a fixed but adjustable needle or controlling magnet,
and the power of the latter is just sufficient to reverse the polarity of
the swinging needle and hold it in any position to which the case and
fixed magnet may be turned when the indicator is only exposed to one
influence from the magnetic current. The controlling magnet being
adjusted horizontally or vertically, or both, is to be positioned relatively
to the swinging needle so that the magnetic influences are harmonized or
balanced, and the indicating needle will point to the zero of the case
in all positions when influenced by local attraction. When this indicator
is subjected to the compound influence resulting from local attraction
and the magnetic current, a variation is indicated by the swinging needle
equal in amount to the variation to which a compass will be exposed
inder like circumstances. The variation indicated by my instrument
is probably due to the reversed polarity of the fixed magnet and the
swinging needle as influenced by the two forces of local and magnetic
currents, for my indicating instrument will denote in degrees the force
of local attraction generally, regardless of the position of the instrument
to the true north and south lines.
SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said Henry Glover in the Great Seal Patent Office on
the 27th August 1872.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, HENRY
GLOVER, of Brooklyn, in the State of New York, United States of 35
America, send greeting.

page_text: WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent bearing date the Seventh day of March, in the year of
our Lord One thousand eight hundred and seventy-two, in the thirty-
fifth year of Her reign, did, for Herself, Her heirs and successors, give
and grant unto me, the said Henry Glover, Her special licence, that I,
the said Henry Glover, my executors, administrators, and assigns, or
such others as I, the said Henry Glover, 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 LOCAL MAGNETIC
ATTRACTION INDICATORS," upon the condition (amongst others), that I,
the said Henry Glover, my executors or administrators, by an instru-
ment in writing under my, or their, or one of their hands and scals,
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 Henry Glover, do hereby declare
the nature of my said Invention, and in what manner the same is to be
performed, to be particularly described and ascertained in and by the
following statement, reference being made to the Drawing hereto
annexed, and to the letters and figures marked thereon (that is to
say):
Marine and other compasses are very often deflected by local attraction
from the magnetic meridian, and these deflections frequently lead to
grave errors in calculations and often to accidents. This is particularly
the case with iron vessels, and the various compasses on such vessels
are tested and the local influence allowed for, but as this influence
varies and may change according to the course the ship is running, it
becomes of the utmost importance to obtain an instrument that will
indicate the extent of local attraction.
•
'
Compasses have been made with a variety of appliances, such as
primary and secondary needles and magnets, but in consequence of the
varying positions of the parts to the local attractions and magnetic
influences they frequently become changed in the extent or polarity.

page_text: My improvement is not a compass, its construction is such as to
absolutely preclude its use as such; my instrument is simply an indicator
to ascertain local attraction, in order that in reckoning by the ordinary
compass the local attraction may be allowed for, and this instrument is
so constructed that it may be adjusted from time to time, and when
positioned near an ordinary compass or in the place to be occupied by
such compass will indicate the number of degrees variation that will
be produced in that compass by the local attraction. I make use of
two needles or magnets, one a swinging needle or indicator, the other a
fixed but adjustable needle or controlling magnet, and the power of-the
latter is just sufficient to reverse the polarity of the swinging needle
and hold it in any position to which the case and fixed magnet may be
turned when the indicator is only exposed to one influence from the
magnetic current. The controlling magnet being adjusted horizontally
or vertically, or both, is to be positioned relatively to the swinging
needle, so that the magnetic influences are harmonized or balanced, and
the indicating needle will point to the zero of the case in all positions
when uninfluenced by local attraction. When this indicator is subjected
to the compound influence resulting from local attraction and the
magnetic current, a variation is indicated by the swinging needle, equal
in amount to the variation to which a compass will be exposed under
like circumstances. The variation indicated by my instrument is probably
due to the reversed polarity of the fixed magnet and the swinging
needle as influenced by the two forces of local and magnetic currents,
for my instrument will denote in degrees the force of local attraction
· generally regardless of the position of the instrument to the true north
and south lines.
In the Drawing Fig. 1 is a vertical section of said indicator; Fig. 2
is a plan of the fixed magnet; Figs. 3 and 4 are plans of modifications
in the shape and mode of adjusting the fixed magnet; and Fig. 5 is a
section of the indicating instrument with the needle between two glasses.
The bowl or case a is of suitable size or shape and contains a pintle b
for the indicating needle; c and d is the controlling magnet that is
sufficiently powerful to reverse the needle c and hold it in line with
itself when the compass is placed in any position relatively to the
meridian line and free from local attraction. The needle d may be in
the form shown in Figs. 1 and 2, where an opening is provided in the
needle d sufficiently large to allow for the pintle b to pass and the
needle d to be adjusted to such a point that the neutral magnetic center

page_text: of d shall coincide with the pintle b, and thereby the action of the
magnet d will be uniform on the needle c in any position. The end of d
may project through the case so as to be moved in adjusting the
needle d, or the needle d may be provided with a sleeve passing over
the pintle and secured by a clamp screw i, so as to correctly position
the needle as in Fig. 3. With a needle of the character aforesaid it is
important that an adjustment laterally should be provided; I therefore
make a transverse slot in line with the pivot, and secure the needle
when adjusted by a set screw o, as seen in Figs. 4 and 5. A disk of
non-conducting material may be employed as at m to lessen the action
of one needle on the other; this may be of mica or glass. In Fig. 5
I have shown this sheet of non-conducting material as a glass to which
the pivot or pintle b is attached. The distance vertically between the
magnet d and needle c may be varied so as to regulate the force of the
controlling magnet d upon the needle c. By adjusting the parts of this
instrument when free from local attraction as aforesaid, the same
becomes a true indicator of the local attraction when exposed to the
same, so that compasses can be rated and the variations allowed for.
What I claim as my Invention and desire to secure by Letters Patent
is, the local attraction indicating instrument made with the adjustable
magnetic needle d having sufficient power to reverse and hold the
indicating needle c when free from local attraction, in combination
with said indicating needle c, substantially as and for the purposes set
forth.
In witness whereof, I, the said Henry Glover, have hereunto set
HENRY GLOVER. (L.S.)
Witnesses,
CHAS. H. SMITH, 121, Nassau St., New York.
GEO. T. PINCKNEY,
دو
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