IMPROVEMENTS IN THE MARINER'S COMPASS
Year: 1875

page_text: LETTERS PATENT to David Baker, of the City of Boston and State
of Massachusetts, in the United States of America, for the Inven-
tion of "IMPROVEMENTS IN THE MARINER'S COMPASS.”
Sealed the 15th June 1875, and dated the 29th April 1875.
COMPLETE SPECIFICATION filed by the said David Baker at the Office
of the Commissioners of Patents, with his Petition and. Declaration
on the 29th April 1875, pursuant to the 9th Section of the Patent
Law Amendment Act, 1852.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, DAVID
BAKER, of the City of Boston, and State of Massachusetts, in the United
States of America, send greeting.
WHEREAS I am in possession of "IMPROVEMENTS IN THE MARINER'S
COMPASS," and have petitioned Her Majesty to grant unto me, my
executors, administrators, and assigns, Her Royal Letters Patent for
the same, and have made solemn Declaration that I am the true and
first Inventor thereof.

page_text: NOW KNOW YE, that I, the said David Baker, do hereby declare
that the following Complete Specification, under my hand and seal,
fully describes and ascertains the nature of the said Invention, and
in what manner the same is to be performed, in and by the following
statement thereof, reference being had to the accompanying Drawings
and the figures and letters marked thereon, that is to say :-

page_text: as usual.
when it expands and contracts by changes of temperature. This conical
disc retards any any momentum imparted to the liquid within the bowl.
L is an outer casing of metal containing the weight M, which retains
the compass bowl in an upright position when suspended in the gimbals
The interior of the bowl G is lined with paper or cloth
secured thereto with paste or other adhesive material. I make the
vertical mark T upon the inside of the compass bowl G (known as the
*"lubber's line" shown in Figure 3, in or near the vertical plane of the
axis of the outer gimbal, thus changing its position about ninety degrees
from the point where it has heretofore been located. By this construc-
tion the axis of the outer gimbals are placed "fore and aft” when in
use for marine purposes, the "lubber's line" remains steady, at all times
indicating the true course of the ship, as she is "heeled" upon one side
when rising and falling over the sea.
The compass bowl being constructed shallow only a small quantity of
liquid is required to fill it, thus reducing the variations between its
expansion and contraction so as to require but a single flexible bottom..
I fill the compass bowl with a light clear oil, such as kerosene, or
similar product of petroleum. The cover S is retained on the case R
by projections P formed on the gimbal bearings V.
Having now described the nature of my Invention and in what
manner the same is to be performed, what I claim is,―
Firstly. A liquid compass in which the liquid that comes in direct
contact with the pivot, card, and magnets, is oil, or a liquid in which
oil predominates sufficiently to prevent the magnets and pivot from
becoming oxidized as herein-before set forth.
Secondly. The constructing of the frame of the compass card of wood,
and providing the card with letters and points of similar color, as
shown in the Drawings, and as herein-before described.
Thirdly. The constructing of the compass bowl with a bottom com-
posed of a single curved disc of thin sheet metal sufficiently flexible to
allow for the expansion and contraction of the liquid with which it is
filled, as herein-before described.
Fourthly. The constructing of a conical disc provided with a short
pivot, upon which the card rests and turns as herein-before described.

page_text: Fifthly. The constructing of the cap ring and its attachment to the
flange of the bowl by means of screws passing up through the flange
into the cap ring, as herein-before described.
Sixthly. The lining of the interior of the compass bowl with paper
secured thereto with paste or other adhesive material, as herein-before
described.
Seventhly. The constructing of a mariner's compass, with means of
indicating the "lubber's line "placed in or near the vertical plane of the
axis of the outer gimbal, as herein-before described.
Eighthly. The constructing of the fixed gimbal bearings or supports,
with projections for securing the cover in position on the case, as herein-
before described.
In witness whereof, I, the said David Baker, have hereunto set
my hand and seal, this Seventh day of April, in the year of
our Lord One thousand eight hundred and seventy-five.
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