IMPROVEMENTS IN AND RELATING TO MARINERS' COMPASSES
Year: 1879

page_text: LETTERS PATENT to William Robert Lake, of the Firm of Haseltine, Lake,
& Co., Patent Agents, Southampton Buildings, London, for the Invention of
"IMPROVEMENTS IN AND RELATING TO MARINERS' COMPASSES." A communi-
cation from abroad by Stephen Longfellow, of Philadelphia, Pennsylvania,
United States of America, Master Mariner.
COMPLETE SPECIFICATION filed by the said William Robert Lake at the
Office of the Commissioners of Patents on the 3rd July 1879.
WILLIAM ROBERT LAKE, of the Firm of Haseltine, Lake, & Co., Patent Agents,
Southampton Buildings, London. "IMPROVEMENTS IN AND RELATING TO MARINERS'
COMPASSES." A communication from abroad by Stephen Longfellow, of Phila-
delphia, Pennsylvania, United States of America, Master Mariner.
The first part of this Invention relates to certain improvements in methods of
and devices for preventing the deviation of the compass needle from its proper
direction caused by the effects of local attraction, and comprises:-First. The
arrangement around the compass-bowl of a series of curved bar-magnets which are
attached to the bowl in such a manner as to be capable of adjustment in three
directions, namely, circumferentially, horizontally, and vertically, and thus not only
prevent the effects of local attraction, but also prevent the dip of the needle and
maintain the compass card in a horizontal position. Secondly. Constantly main-
taining the needle whatever may be the force or forces exerted by the cause or
causes of local attraction under the influence of magnetic forces acting around the
circle described by the needle in its rotation, so that any force tending to cause a
deviation of the needle from the true north will be neutralized in its effect by an
opposing force by arranging a series of independent removable and radially
adjustable magnets in a circle around the compass-bowl in as near proximity to
each other as convenience of manipulation for the purpose of adjustment will
permit, so that they will neutralize each other's effect upon the compass-needle, and
by removing from or adjusting on said circle opposite to the source or sources of
local attraction, and on the side nearest to said source or sources of local attraction
such a number of said magnets that all the forces then acting (both those due to
n

page_text: the cause or causes of local attraction and those due to the remaining magnets) will
be the same in effect as far as regards causing a deviation of the needle as when no
-source-or-sources-of-local-attraction-exist, and the magnets_are_so_placed_that_the
needle will point to the true north. Thirdly. Constructing the compass-needle in
-two-parts,-one-part-being-of-some non-magnetic metal and the other part being of
-steel-or-of-hardened-iron,-and-the-two-parts being so connected that the south.pole.
-of-the-needle-will-be-near the pivotal-point of the needle, and therefore the effect
of local attraction upon the said south pole will be practically nil. And, Fourthly.
"The combination with the series of independent removable-and-radially-adjustable-
magnets herein before referred to of a compass-needle having one pole near the
pivotal point of the needle.
The second part of the said Invention relates to certain improvements in
weighting or ballasting the compass-bowl, and consists in the use, for this purpose,
of a hollow globe which is attached to the bottom of the compass-bowl, and contains
fine shot or other suitable weights, the quantity of which can be varied at pleasure,
so that the weight of the bowl can be perfectly regulated as necessity requires,
thereby rendering the same compass equally serviceable in light or in heavy
weather, and obviating the necessity of having two compasses, one heavy and the
other light.
The third part of the said Invention relates to the manner of illuminating the
compass-card, and consists in effecting this by means of lamps on each side of the
cover of the bowl, and by providing the interior of the cover with a reflecting
.surface.
In the accompanying Drawing,
Figure 1 is a view in elevation of the case containing the compass, and shows
the top or cover of the case in position.
Figure 2 is a perspective view of the case with the top removed, and shows the
compass-bowl contained in the case, and the azimuth circle and sight vanes attached
to the compass-bowl.
Figure 3 is an elevation of the compass-bowl detached from the case, and shows
the form of the bowl and the arrangement and manner of attaching the curved
magnetic bars.
Figure 4 is a detached view of one of the curved magnetic bars.
Figure 5 is a detached view of the spindle and weight.
Figure 6 is a sectional view through the line x, x, Figure 7, of a compass, in
which the effects of local attraction are prevented by the arrangement of a series of
removable radially adjustable magnets in a circle around the compass bowl, and in
which the needle is made in two parts, one being of brass or some other non-
magnetic metal, and the other of steel or of hardened iron; and
Figure 7 is a plan of the same form of compass.
Like letters indicate the same parts throughout the Drawing.
A-is-the-case-or-shell-containing-the-compass,-which-case-may-be_of_ovoid form,
as shown, or of spherical form if preferred, and is made in two parts B and C,
removable one from the other, but capable of being closely connected by any
suitable fastening device, as shown at a, Figures 1 and 2, so that a complete
protection from the weather is afforded for the compass contained therein. This
case may be mounted upon a suitable standard, and is then designed to take the
place of the present standard compass or of the ordinary wooden binnacle; or by
dispensing with the upper part B it can be placed in a box and used in the ordinary
manner.
C1, Figures 2 and 3, is the compass-bowl which is suspended within the case by
gimbals in the usual manner, D being a gimbal-ring, which in Figure 3 is shown
out of position in order that the magnetic bars may be clearly seen; E is the
compass-card; F, F¹, F, F, are the magnetic bars arranged around the bowl.
These bars are made of square iron hardened and thoroughly magnetized. They are
in the shape of a segment of a circle, and are in length equal to about one sixth
the circumference of the bowl.
:

page_text: Lach bar is inserted into a sleeve or socket G which is capable of being opened
longitudinally so as to admit of the easy removal of the bar, and when closed is
fastened by a pin b. Attached to this sleeve by a joint d is a short arm H at right
angles to the sleeve, and this arm is hinged at c to an oblong curved plate í. By
means of these plates the magnets are secured to the compass bowl in the following
manner Around the compass bowl and just below the gimbals are three parallel
bands K, K; K", separated from each other by a distance just equal to the width
of the plate, and by means of these bands grooves are formed for the reception of
the plate i.
The curve given to the plate i is such that when it is applied to the surface of
the bowl it fits closely and is kept against this surface by the bands, but can slide
in the grooves formed by the bands so that the bars can be moved to any position
in the grooves as may be desired, according to the force and direction of the local
attraction which it is desired to overcome.
The upper and lower bands K¹, K, do not extend entirely around the compass
bowl, there being a space the length of the plate i, as shown at L, Figure 3, and
this space permits of the insertion and removal of the plates i.
For the purpose of affording a more secure attachment of these plates their edges
may be bevelled off and the bands may be cut in so that the plates will dovetail
between the bands.
. I have adopted this manner of attaching the magnetic bars to the compass-bowl
as a convenient way of obtaining the facility of circumferential adjustment, but
other methods of attachment which will accomplish the same result may be adopted.
By means of the joints in the arms. H each of the curved magnetic bars may be
elevated to or above the plane of the card or depressed below that plane, and the
distance of each bar from the bowl can also be varied.
These different positions of the bars are shown at F and F in Figure 3. By
this simple device each bar is rendered adjustable in three directions, namely,
circumferentially, horizontally, and vertically, and consequently a perfect adjustment
of the needle to the true north and to a horizontal position can be obtained for
every form and degree of local attraction and in any latitude.
In order to prevent the magnetic bars from coming in contact with each other at
their extremities and thus change the distribution of magnetism in them, pear-
shaped pieces of glass or porcelain about one inch in length and three quarters of
an inch in diameter, as shown at M, are screwed on to each end of each of the
bars.
Another series of similar magnetic bars may be attached to the bowl by means
of the grooves K¹, K, and if desired a third series of magnetic bars may be used.
When this is done two or more magnets may be brought together, thus increasing
the power at any given point; and the power can be concentrated at will by the
removal of one or more magnets from the series.
.
In the Drawing a series of four bars is shown, but I do not confine myself to
this number as any other number may be used.
Instead of curved bar-magnets, as described, I can use a series of small straight
removable magnets arranged in a circle around the compass-bowl and capable
of independent radial adjustment. This arrangement of magnets is shown in
Figures 6 and 7.
Referring to these Figures a', a', a¹, a¹, are the straight magnets, each of which
is loosely mounted upon a pin b' extending radially from the compass bowl and
attached to a ring of metal which is sprung upon the compass bowl or otherwise
suitably attached thereto, or the pins b¹, b', may be attached directly to the bowl.
The magnets a¹, a¹, a¹, a¹, are made of steel or hardened iron, and should have a
diameter about equal to their length, and they should be placed as near to each
other as will admit of their being brought in contact with the compass bowl without
touching each other.
For the purpose of obtaining radial adjustment of the magnets there is a spiral
spring c on each pin b', which spring bears against the magnet on the pin and acts

page_text: to force the magnet outward from the compass bowl, and by means of a nut d¹ on
each pin; each magnet can be readily fixed at any desired distance from the bowl..
I have described-this-device-as-suitable for effecting the radial adjustment of the
magnets, but instead of this device any other may be used.
When this arrangement of magnets is used I prefer to make the compass needle
in two parts B2; C, the part-B2; which is the north pole of the needle, being of steel,
aud the other part C, being of brass or of some other non-magnetic metal. The
south pole of the needle is thus near the_centre_of_the_card,-and-therefore-the-
position of the needle is not affected by the influence of local attraction upon its
south pole.
-If the magnets a, a, a, a, are each-placed at an equal distance from the compass
card no effect will be produced upon the needle, for the reason that the forces exerted
by these magnets upon the needle are neutralized by each other, and consequently
if there is no source of local attraction acting upon the needle it will point correctly.
If however there is a deviation of the needle caused by local attraction, it can be
brought into the correct position by removing from or adjusting on the circle of
magnet opposite to the point or points from which the local attraction is exerted
such a number of the magnets a', à¹, a¹, a', as are equal in magnetic effect to the
cause or causes of local attraction, and if this removal or adjustment of some of the
magnets does not bring the needle to the correct position this can be effected by
adjusting nearer to or further from the compass bowl as may be necessary the proper
number of the remaining magnets of the circle, which number will be ascertained
by experiment.
In some cases it may not be necessary to remove any of the magnets from the
circle, but the proper correction can be effected by a radial adjustment of the
magnets.
It will thus be seen that all effects of local attraction can be neutralized and the
needle maintained in its proper position.
It is preferable to place the magnets in the same plane, and in the plane of the
card, as by this arrangement the dip of the needle is prevented.
The arrangement of magnets, and the manner of attaching them to and of
adjusting them on the bowl which I have thus particularly set forth, is described as
a suitable way of carrying the principle of my Invention into effect, but any other
form of magnets, or any other arrangement of them in relation to the bowl, or any
other method of rendering them removable or adjustable may be adopted whereby
the needle, whatever may be the force or forces exerted by the cause or causes of
local attraction will be constantly maintained under the influence of magnetic forces
acting around the circle described by the needle in its rotation in such a manner
that any force having a tendency to cause a deviation of the needle from the true
north will be neutralised by an opposing force, or in other words, any arrange-
ment of magnets maintaining the needle under the influence of magnetic forces-
which-permit the needle to point to the true north in the absence of causes of local
attraction, and which admits of the neutralization of the effect of any cause or
causes of local attraction by the removal or adjustment of such portion of said
forces as shall be equivalent in force or direction to the force or forces exerted by
the cause or causes of local attraction.
It will thus be seen that by this method of preventing the effect of local attraction
upon the compass needle, the earth's magnetic force is left free to direct the needle
to the pole, while every cause of local attraction is neutralized by an opposing force
independent of the earth's magnetism.
As shown in Figures 3 and 6 the compass bowl, instead of being of the usual
hemispherical form; terminates in an elongated neck, by which form increased
steadiness is obtained and a firm support afforded for the spindle which supports
the compass card. This spindle N is secured into the elongated neck of the bowl,
and to the lower end of this spindle is attached the weight used for ballasting the
compass. This weight consists of a hollow brass globe O constructed in two parts
connected by a screw thread and containing a quantity of fine shot or other suitable.

page_text: weights, the quantity of which can be varied at pleasure according to the amount
of ballast which it is necessary for the compass bowl to have, and thus the compass
can be kept perfectly ballasted and equally serviceable both in light and in heavy
weather.
By the manner of attaching the spindle to the compass bowl the former is kept
perfectly perpendicular to the plane of the compass card.
P is the azimuth circle which consists of a removable band encircling the bowl
just above the gimbals. It has attached to it two suitable sockets R opposite to
each other for the reception of the sight vanes S, S₁, one of which vanes is jointed
as shown at e so that the ray of light can be thrown directly across the face of the
compass, giving the exact bearing of the sun upon a circle T on the inner edge of
the bowl, just above the card, graduated to degrees and minutes. This band P fits
the bowl loosely so that the vanes are capable of being moved around the bowl for
the purpose of obtaining correct bearings of any object, which bearings are read
upon the graduated circle.
The cover B of the compass bowl is hemispherical in form, and has on each side a
tubular projection B', in which projections are fitted the lamp cases U, U. These
lamp cases are provided with ventilators X, X, doors W, W, and handles V, V. The
lamps, one of which is shown in dotted lines at E', Figure 1, are fitted with kerosene
burners and are adapted to burn heavy oil, and each is secured in its case by the
insertion of its oil receptacle into a hole in the bottom of the case.
The whole interior surface of the cover is nickel plated so that a strong light will
be reflected from the lamps upon every part of the compass card.
In the after side of the cover is a square pane of glass of a width about equal to
one sixth of the circumference of the cover, through which glass the compass card
can be seen when the cover is in place.
Having thus fully described the said Invention, as communicated to me by
my foreign correspondent, and the manner of performing the same, I wish it under-
stood that I claim,-
First. In a mariners' compass one or more series of removable curved magnetic
bars attached to the outside of the compass-bowl and capable of adjustment
circumferentially, horizontally, and vertically, substantially as and for the purpose
set forth.
Second. The combination of the magnetic bar F, the sleeve G, the double jointed
arm H, and the curved plate i, substantially as and for the purpose set forth.
Third. The combination with the curved bar maguets of the insulators, sub-
stantially as and for the purpose set forth.
Fourth. The combination with the compass bowl of the bands K, K¹, K", formed
and placed on the outside of the bowl, substantially as and for the purposes set
forth.
Fifth. The method, substantially as described, of preventing the deviation of the
compass-needle caused by local attraction .by constantly maintaining the ncedle
(whatever may be the force or forces exerted by the cause or causes of local
attraction) under the influence of magnetic forces acting around the circle described
by the needle in its rotation as set forth, so that any force tending to cause a
deviation of the needle from the true north will be neutralized in its effect by an
opposing force.
Sixth. The combination with a compass needle of a series of independent
detachable and radially adjustable magnets arranged in a circle about the compass-
bowl in as close proximity to each other as convenience of manipulation for the
purpose of adjustment will permit, substantially as and for the purpose set
forth.
Seventh. A compass needle constructed in two parts, one part being formed of
some non-magnetic metal, and the other of steel or hardened iron, and having the
south pole of the needle near its pivotal point.
Eighth. The combination with a series of independent detachable and radially

page_text: adjustable magnets of a needle having one pole near is pivotal point, substantially
as and for the purpose set forth.
Ninth. In combination with the compass-bowl the series of small straight
removable magnets, the projecting-pins, the spiral springs-on-the-said.pins,.and.the.
nuts, substantially as and for the purpose set forth.
Tenth. The combination with the compass-bowl of the spindle N and the
adjustable receptacle attached thereto containing removable weights, substantially
as and for the purpose set forth..
Eleventh. The combination with a mariners' compass of a concave reflector
-forming-a-casing above-the-card, and of side lamps arranged to throw the light
both on the card and on the reflector, substantially as and for the purpose set
forth:
In witness whereof, I, the said William Robert Lake, have hereunto set my
hand and seal, this Third day of July, in the year of our Lord One thousand
eight hundred and seventy nine. .
WM. ROBT. LAKE. (L.S.)