A NEW OR IMPROVED INSTRUMENT OR APPARATUS FOR ASCERTAINING OR DETERMINING THE LATITUDE AND LONGITUDE OF ANY PLACE, OR THE SITUATION OF SHIPS OR OTHER VESSELS AT SEA, AND THE DIP AND VARIATION OF THE MAGNETIC NEEDLE, WHICH NEW OR IMPROVED INSTRUMENT I INTEND TO DENOMINATE 'SHERWOOD'S MAGNETIC GEOMETER
Year: 1838

page_text: TO ALL TO WHOM THESE PRESENTS SHALL COME, I, RICHARD
MARCH HOE, late of New York, in the United States of America, but now
residing at the Office for Patents, 66, Chancery Lane, in the County of
Middlesex, Civil Engineer, send greeting.
WHEREAS Her present most Excellent Majesty Queen Victoria, by Her
Royal Letters Patent under the Great Seal of Great Britain, bearing date at
Westminster, the Eighteenth day of July, in the second year of Her reign,
and in the year of our Lord One thousand eight hundred and thirty-eight, did,
for Herself, Her heirs and successors, give and grant unto me, the said
Richard March Hoe, Her especial licence, full power, sole privilege and
authority, that I, the said Richard March Hoe, my executors, administrators,
and assigns, and such others as I, the said Richard March Hoe, my executors,
administrators, or assigns, should at any time agree with, and no others, from
time to time and at all times during the term of years therein mentioned,
should and lawfully might make, use, exercise, and vend, within England,
Wales, and the Town of Berwick-upon-Tweed, and Her Majesty's Colonies
and Plantations abroad, an Invention of "A NEW OR IMPROVED INSTRUMENT OR
APPARATUS FOR ASCERTAINING OR DETERMINING THE LATITUDE AND LONGITUDE OF
ANY PLACE, OR THE SITUATION OF SHIPS OR OTHER VESSELS AT SEA, AND THE DIP
AND VARIATION OF THE MAGNETIC NEEDLE, WHICH NEW OR IMPROVED INSTRUMENT I
INTEND TO DENOMINATE 'SHERWOOD'S MAGNETIC GEOMETER,'" being a communica
tion made to me by Dr. H. H. Sherwood, of New York aforesaid, a foreigner
residing abroad; in which said Letters Patent is contained a proviso, obliging
me, the said Richard March Hoe, by an instrument in writing under my hand
and seal, particularly to describe and ascertain the nature of my said Inven..

page_text: tion, and the manner in which the same is to be performed, and to cause the
same to be inrolled in Her Majesty's High Court of Chancery within six
calendar months next and immediately after the date of the said in part recited
Letters Patent, as in and by the same, reference being thereunto had, will
more fully and at large appear.
NOW KNOW YE, that in compliance with the said proviso, I, the said
Richard March Hoe, do hereby declare that the nature of the said Invention,
and the manner in which the same is to be performed, are particularly
described and ascertained in and by the following description thereof, reference
being had to the Drawings hereunto annexed, and to the letters and figures
marked thereon (that is to say) :-
This Invention of a new or improved instrument or apparatus for ascer-
taining or determining the latitude and longitude of any place, or the situation
of ships or other vessels at sea, and the inclination or dip and variation of the
magnetic needle consists of a philosophical instrument or apparatus furnished
with a magnetic dipping needle, and certain divided or graduated rings or
circles, and calculations or tables, whereby the latitude or longitude of any
place on land, or of a ship at sea, may be ascertained; and determined without
the aid of celestial observations, and also the dip or inclination and variation
of the magnetic needle ascertained (that is to say):-This new or improved
instrument is connected with a vertical ring accurately divided into degrees,
minutes, seconds, &c., with a magnetic dipping needle mounted therein, and
furnished or not, as thought desirable, with a counterbalanced. or magnetized
ring, by which magnetic bar or ring the dip or inclination of the needle may be
ascertained at any place or situation, and also with certain movable circles
divided into degrees (°), minutes ('), seconds ("), thirds ("), and hundreds (""),
or other suitable graduations, from which tables calculations are formed for the
purpose of ascertaining the latitude and longitude of any place on land, or
ship at sea; and I will proceed to describe the same in the language of the
Inventor as follows:-In investigating the phenomena of terrestrial magnetism,
I have found and determined the latitude and longitude of two magnetic poles,
one of which is in the northern and the other in the southern hemisphere.
The one in the northern hemisphere is in latitude 60° 32', or in the arctic
circle, and on the Fifteenth September, One thousand eight hundred and
thirty-seven, was in longitude 93° 16' 03" "04"" west of Greenwich, and the one
in the southern hemisphere is in latitude 66° 32', or in the antarctic circle;
and on the Fifteenth September last, or in the year One thousand eight hun-
dred and thirty-seven, was in longitude 86° 43' 56" 56", east of Greenwich.
I have also found and determined the longitude of the line of, no variation, in

page_text: latitude 42° 53' N., and on the terrestrial equator in the western hemisphere,
and its longitude in a number of intermediate latitudes, and have also traced it
round the globe. I have ascertained its angle with the terrestrial meridians,
and given a rule by which its angle between any two latitudes may be easily
ascertained. The longitude of this line in latitude 42° 53' N., on the Fifteenth
September, One thousand eight hundred and thirty-seven, was 80° 20' 03" 04",
and on the equator 69° 09′ 09" 55"". I have likewise found and deter-
mined that the magnetic poles move round the terrestrial poles in the arctic
and antarctic circles, and have found and determined the period in which
they make a complete revolution around the said terrestrial poles, which
is the term of 666 years less 36". I have also found and determined the
yearly, daily, and hourly rate of motion of the said magnetic poles, so that it
will be easy hereafter to find at any time the exact longitude of the magnetic
poles in their circles and the exact longitude of the line of no variation in
any latitude. I have traced the line of no variation by its rate of motion
from its longitude in One thousand eight hundred and thirty-seven back to
London in One thousand six hundred and fifty-seven, and Paris in One thousand
six hundred and sixty-six, when it passed through those cities. The yearly
rate of motion of the magnetic poles and line of no variation is 32' 26", i. e.,
2' 40" in 30 days, 37" 20" in seven days, 5' 20"" in twenty-four hours, 2"40"
in twelve hours, 1" 5/12 in one hour. I have found and determined the angle
of the magnetic with the terrestrial axis of the earth, and the angle of the
magnetic with the terrestrial equator, each being at an angle of 23° 28', and
have constructed tables and an instrument, called a magnetic geometer, by which
the angles of the magnetic with the terrestrial meridians in any latitude, and
the angles of the magnetic with the terrestrial latitudes may be easily found,
and the latitude and longitude thereby found and determined by the variation
of the needle and rate of motion of the magnetic poles. Finally, I find and
determine, and give rules for finding and determining, tho true variation at any
place on the globe with a dipping needle at any time without the aid of a
celestial observation.
Fig. 1 of the accompanying Drawings represents a side elevation of a
simple arrangement and construction of instrument which will serve to illus-
trate this Invention. It consists of a dipping needle and magnetic instru-
ment, called a geometer, for finding the dip and variation and latitude and
longitude of any place. The needle a, which is of steel, is suspended by
an axle, which rests in agate bearings fastened in the end of screws b,
which pass through a bar c on each side of the needle; as seen in the
Drawing. The needle swings within a circle d, divided into degrees and certain
parts of degrees. This circle- rests on another circle e, or bottom standard, as

page_text: may
seen in the Drawing, with its outer edge raised and divided into degrees and
parts of degrees. There is a movable circle f within this last circle, with
a nonus or vernier g, to find the smallest parts of a degree. There are besides,
first, six concentric movable circles marked A, to find the angle or value of
any dip in degrees, minutes, seconds, and thirds, from which to find the
latitude and variation of any place; and, second, there are six other concentric
moveable circles marked B, by which the value of any number or parts of a
degree of variation may be found, or the number of degrees or parts of degrees
of longitude for any degree or parts of degrees of variation, for the purpose of
finding the longitude of any place. The instrument is supplied with a cross spirit
level h at the top part, and adjustable thumb screws, feet, or standards at i, i,
by which means its perfect or correct level or horizontal and vertical situation
be determined. The series of the circles of the tables A and B may be
made movable, turning upon a centre, so as to bring the different figures
required in an addition or calculation one above the other, and so give a ready.
means of adding up the same, or they may be fixed or marked on one sheet,
and the different figures required selected by the observer, and placed on a
separate piece of paper, and added up afterwards. The instrument may also
be furnished with another series of nine circles, forming a table C, of the one-
half of the diurnal variation of the magnetic needle, as shewn in Fig. 2, which
is a plan view or copy of these three sets of figures, circles, or tables, the
arrangement or figuring of which is as follows:-The two dark lines shew the
divisions of the three tables, the different circles of each of which, for con-
venience merely, may be movable round a centre. These tables are placed on
the upper surface of the first horizontal circle, as shewn in Fig. 1, or under
the cross bars in Fig. 3, which bars are attached to the horizontal circle with
verniers. The first table, or that nearest the centre of the Figure, is a table
of one-half the diurnal variation in every latitude. The second or middle
table shews the declination of the needle from nothing to its maximum of
23° 28' at the terrestrial equator. The third table is that of the declination
of the magnetic axis, or line of no variation, in which the declination of the
needle from nothing to 90° is converted into degrees of longitude.
The following EXAMPLES shew the MANNER of WORKING the INSTRUMENT,
as furnished me by the Inventor.
I. FINDING THE VARIATION.
1. London, 1818. Captain Kater observed the dip
to be
Variation as then observed by him
Variation by the geometer, calculated from his
din
70° 34'
24°
30' 00" 00 W.
91°
30
1" DE!!!

page_text: 3. London, 1818. Kater observed the dip
Latitude as given by British astronomers
Latitude by geometer from Kater's dip
Difference

page_text: 5. St. Louis, June 15, 1819, by Dip'
Major Long
July 1, 1835, by Colonel Nicolet. Variation
Longitude as observed by Long
Longitude as observed by Nicolet
Longitude by unknown engineer in American
70°
30'
-Variation =
10° .47'
38" 00'
8º
49'
08"
90°
06'
15" 00
90°
19'
36"00"
almanack
89°
36'
00" 00"
Greatest difference of the three
-
43'
36" 00"
Longitude by the
geometer
From Long's dip
90°
00'
43" 16"
From Long's variation
90°
00'
00" 54"
From Nicolet's variation
89°
59'
59" 00"
Greatest difference of the three
44" 16"

page_text: I.-LONGITUDE of CHARLESTON, west of line of no variation. October 31st, 1837.
Variation observed by Capt. Mesroun and by Lt. Wilkes = 2° 54' East.
Latitude observed by Capt. M. = 32° 46' 20".
VIII-LONGITUDE of NEW YORK, from the variation found by Dr. Sherwood,
August 1837. Variation = 5° 44′ 45" 38"".
80° 20' 03" 04'' = longitude of the line of no variation, August 1837.
1
34 01 36
difference of angles of mag. and terr. meridian in 42° 53'
and 40° 42' 30" = 11 10 53 09-10 36 51 33.

page_text: 80 26 17 04 = long. of line of no variation in 42° 53', June 26, 1838.
|-01 01 59 05 = difference of angles of mag, and terr. merid. in 42° 53' and
38 55 30 10-11 10 53 09-10 08 54 04.
79 24 17 59
2 25 16 36 = variation.
76 59.01 23 = longitude.
77 01 48 00 = longitude by American almanac.
2 46 37 difference.
The difference is small, but Dr. Sherwood states that the dip was too
large by a few minutes before he began the calculations, and that the needle,
owing to its shape, threw the magnetic meridian one side of the axis of the
needle, and of course occasioned the point to descend below the true dip;
perhaps the most perfect shape of the dipping needle is that of the rhombus;
and the conjugate diameter must be of considerable width in proportion to the
transverse. The more improved instrument Fig. 3 is arranged and constructed
as follows:-The bottom A of the instrument is made of brass or other suitable
material, and is supported by thumb screws B, for the purpose of adjusting,
the levels C, placed on two pieces of brass at right angles with each other, and
connected with the brass circle, having the two verniers D one hundred and
eighty degrees apart, and movable within the graduated circle surrounding it.
On the centre of this circle is surmounted the brass graduated circle E at right
angles or perpendicular to it; and in the centre of this circle is suspended on

page_text: an axis with proper bearings a magnetized, ring F with two verniers G. The
magnetized ring has two poles, a magnetic axis, and magnetic equator, and
dips east and west and north and south in proportion to distance. The mag-
netized ring for this purpose may be an entire ring, with a cross piece of some
other material on which to place the axle, or it may be a wide ring or circular
plate, or it may be a needle without the ring. The axle rests on agate or
some other hard substance at a, with a knife edge or one approaching to it.
The axle is placed on the bar 6 at right angles with the circle in which the
ring moves by means of two forked pieces of brass 6, which are raised or
depressed by moving the slide C, which passes from the brass circle E.
This slide, with the pieces 6 extending across the circle, and that attached to it
on which the agate rests, are made of brass. For vessels at sea, the instru-
ment should be suspended by universal joints, or placed floating in a liquid
bath, to prevent the motion of the ship from disturbing the needle, and
allowing it to settle or adjust itself to a quiescent point.
Having now described and ascertained the nature of this Invention, and the
manner of carrying the same into effect, I would remark, that I do not mean or
intend to confine myself to the precise mechanical arrangement or construction
of the above-described new or improved instrument, as shewn in the Drawings,
nor the mode or method of putting the various parts together, as these may
be varied according to the will of the maker without departing from its prin-
ciple of construction, neither do I intend to confine myself to any particular
metal or materials of which the same is to be composed, as any competent
workman will choose such as are in his opinion best suited for the purpose,
and such as will not interrupt or interfere with the action of the magnetic
needle by any local attraction. And, further, the situation of the spirit levels
or other means used for adjusting the proper position of the magnetic needle
and its graduated ring, and the manner of supporting the ring, may be varied
at pleasure. And in conclusion I state, that what I claim as this Invention
secured to me by the above in part recited Letters Patent is, the new or
improved instrument above described and set forth, consisting of the magnetic
dipping needle or magnetized ring or plate, with its graduated circles for ascer-
taining the "dip" or inclination of the magnetic needle at any place or situation,
together with the series of numbered or figured circles of calculations or series
of tables, from which, or by means of which, calculations may be made
for ascertaining the latitude and longitude of any place or situation on land, or
of a vessel at sea, without the use of a quadrant, sextant, chronometer, or
celestial observation, and also whereby the variation of the magnetic needle
may be ascertained for any given place and time; and, further, the necessary

page_text: means or contrivances for a proper adjustment of the position of the instru-
ment, and the suspending it by univeral joints or in a liquid bath, for pre-
venting the motion of a ship or vessel affecting the proper working of the
needle.
In witness whereof, I, the said Richard March Hoe, have hereunto set
my hand and seal, this Fourteenth day of December, in the year of
our Lord One thousand eight hundred and thirty-eight.
RIC
(L.B.)
AND BE IT REMEMBERED, that on the Fourteenth day of December,
in the second year of the reign of Her Majesty Queen Victoria, the said
Richard March Hoe came before our said Lady the Queen in Her Chancery,
and acknowledged the instrument aforesaid, and all and every thing therein
contained and specified, in form above written. And also the instrument
aforesaid was stamped according to the tenor of the Statute made in the
fifty-fifth year of the reign of His late Majesty King George the Third.
Inrolled the Eighteenth day of January, One thousand eight hundred
and thirty-nine.