IMPROVEMENTS APPLICABLE TO MARINERS' COMPASSES
Year: 1874

page_text: LETTERS PATENT to John Clark, of 12, Silchester Road, Parish of
Kensington, County of Middlesex, Engineer, for the Invention of
"IMPROVEMENTS APPLICABLE TO MARINERS' COMPASSES."
.
•
Sealed the 2nd October 1874, and dated the 9th April 1874.
PROVISIONAL SPECIFICATION left by the said John Clark at the
Office of the Commissioners of Patents, with his Petition, on the
9th April 1874.
I, JOHN CLARK, of 12, Silchester Road, Parish of Kensington, County
of Middlesex, Engineer, do hereby declare the nature of the said Inven-
tion for "IMPROVEMENTS APPLICABLE TO MARINERS' COMPASSES," to be as
follows:
:-
The object of my said Invention is to place a mariner's compass a
such a distance from the ship as to be beyond the disturbing influence
to the compass needle which frequently arises in iron ships, or when
they are laden with a cargo of iron or steel.

page_text: In carrying out my said Invention in practice I float the compass in
a water-tight case in the make of the ship. The said case may be of
copper or other suitable non-magnetic material. I attach the said case
by a tow line of any determined length. I make the said tow line with
a core of spiral copper wire, and through said spiral core I pass a copper
wire so that by pulling said copper wire I release a spring inside said
case to fix the compass card in its position. By this means I obtain a
correct bearing of the said case without the disturbing influence of the
ship or its cargo, and by it can compare the deviation of the ship's
steering compass.
In a modification of my said Invention instead of releasing a spring
inside the said case by pulling a wire inside the tow line I fit inside the
said case a set of simple clockwork, which by unwinding in a determed
time, say 15 minutes, shall fix the compass card in a similar manner.
SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said John Clark in the Great Seal Patent Office on
the 9th October 1874.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, JOHN
CLARK, of 12; Silchester Road, Parish of Kensington, County of
Middlesex, Engineer, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Ninth day of April, in the year of
our Lord One thousand eight hundred and seventy-four, in the thirty-
eighth year of Her reign, did, for Herself, Her heirs and successors,
give and grant unto him, the said John Clark, Her special licence
that he, the said John Clark, his executors, administrators, and assigns,
or such others as he, the said John Clark, his 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 APPLICABLE TO MARINERS'
COMPASSES," upon the condition (amongst others) that he, the said John

page_text: Clark, his executors or administrators, by an instrument in writing
under his, 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 he, the said John Clark, do hereby declare
the nature of his said Invention, and in what manner the same is to be
performed, to be particularly described and ascertained in and by the
following statement:-
-
The object of my said Invention is to place a mariner's compass at
such a distance from the ship as to be beyond the disturbing influence
to the compass needle which frequently arises in iron ships, or when
they are laden with a cargo of iron or steel.
In carrying out my said Invention in practice I float the compass in
a water-tight case in the wake of the ship. The said case may be made
of copper, brass, zinc, gutta percha, wood, or other suitable non-magnetic
material. I attach the said case by a tow line of any determined length.
I make the said tow line with a core of spiral copper wire, and through
the said spiral core I pass a copper wire, so that by pulling the said
copper wire I can release a spring inside the said case to fix the compass
card in its position. By this means I obtain a correct bearing of the
said case without the disturbing influence of the ship or its cargo, and
by it can compare the deviation of the ship's steering compass. I make
the said case sufficiently heavy, by loading it with ballast or otherwise,
to sink, but I prevent it from sinking further than about 20 feet from the
surface by suspending it from a wire line attached to a small supple-
mentary floating buoy, my object being to keep the case below the
surface agitation of the water. I also propose to fit a keel, or ribs, or
fins to the said case to keep it in trim the better when dragged after the
ship.
In a modification of my said Invention, instead of releasing a spring
inside the said case by pulling a wire inside the said tow line, I fit inside
the said case a set of simple clockwork, which by unwinding in a
determined time, say 15 minutes, shall fix the compass card in a similar
manner.

page_text: In using my said Invention I lower the said case over the stern of the
ship and allow it to float astern for any determined distance, but
sufficient to place the needle beyond any disturbing magnetism induced
by the ship or its cargo. I then make fast the tow line and drag the
case in the wake of the ship a short time to allow the needle to settle to
the polarity of the earth. I then give the wire inside the said tow line
a smart pull, and thus release the spring inside the said case to fix the
compass card in its position. I then draw the case on board and
compare the floating compass with the ship's steering compass to correct
any deviation in the latter. Or if the said floating case is fitted with
the above described modification of clockwork I allow it sufficient time
L
Mind half a f— the cowl hofono nulling it on board
In using my said Invention I lower the said case over the stern of the
ship and allow it to float astern for any determined distance, but
sufficient to place the needle beyond any disturbing magnetism induced
by the ship or its cargo. I then make fast the tow line and drag the
case in the wake of the ship a short time to allow the needle to settle to
the polarity of the earth. I then give the wire inside the said tow line
a smart pull, and thus release the spring inside the said case to fix the
compass card in its position. I then draw the case on board and
compare the floating compass with the ship's steering compass to correct
deviation in the latter. Or if the said floating case is fitted with
the above described modification of clockwork I allow it sufficient time
to unwind itself and fix the card before pulling it on board.
any
Í now proceed to describe more particularly my said Invention,
reference being made to the accompanying Sheet of Drawings.
DESCRIPTION OF THE DRAWING.
Fig. 1 is an elevation of the said water-tight case about one-third
the full size. It is formed of a central part containing the compass and
clockwork for fixing the card, and with hollow conical ends for making
it drag casily through the water. The said tow line is fixed to a shackle
at or near the fore end.
Fig. 2 is a plan of the compass and gimballs, with the central part
of the case shown in section. The end "a" is securely soldered to the
body, and the conical ends of the case are securely soldered or otherwise
fixed to the central part. This and the two following Figures are shown
full size.
Fig. 3 is an elevation of the compass and wheelwork for fixing the
card "a," a glass eye piece for observing the position of the card;
"b," a bowl or rib for supporting wheelwork; c," case for concentric
spring for operating wheelwork. The spring I prefer to make of hard
German silver. "d," a milled hood or cover to be removed for winding:
up spring.
Fig. 4 is a longitudinal elevation in section of the central part of
the case and wheelwork. a, b, c, and d," refer to corresponding
parts in Fig. 3. "e," the sight piece to determine the bearing;
"f" the card and needle which may be suspended on the pin in any

page_text: .
approved manner; "g," a top bracket against which the card is pressed
by the spring and pad "h," when the card is fixed; i, a bracket for
holding the pin for swinging card; "k," centre spindle fitted with
socket at bottom for key to wind up spring. The spring is contained in
case "c." One end of spring is fixed to inside of case, and the other
end is fixed to the spindle "k." "1," a ratchet wheel fixed to the
spindle and in gear with a detent or pawl on wheel "m," "m, n,
o, p, q,” and “" is a train of wheelwork to accelerate the speed
of pinion "." On the top of "p" is a boss to which is fixed a light
spring which presses against the inside of the case "8" to retard the
unwinding of the said train of wheelwork to a determined time, say
15 minutes. "t" is a pinion fixed on spindle "k" in gear with
wheels "
u,' ," "w," to reduce the speed of wheel "w." The top
side of "
" is fitted with a camb which operates the step
"2
$6 and
spring and pad "h" to fix the compass card when required. On "w” is
also fixed a stop to regulate the limit of winding and unwinding. The
whole of the above fittings are carried on the gimballs and are con-
structed to swing round inside the said case freely, so that the compass
shall in any position of the said case remain in an upright position by
gravity.
20
33 66
In a modification of my said Invention I propose to dispense with the
gimballs and train of wheelwork described under Fig. 4, and fix the
compass card by the motion of a small screw propellor projecting from
the extremity of the said case. The said screw propeller has motion
imparted to it by the case being dragged through the water in the wake
of the ship.
Having now particularly described and ascertained the nature of my said
Invention, and in what manner the same is or may may be performed, I
also wish it to be understood I do not limit myself to the precise
arrangements or dimensions described or delineated, because from the
nature of my said Invention these may both be modified in practice,
but what I consider as novel and herein claim are—
First. Floating a compass in a water-tight case in the wake of the
ship, substantially as described.
Second. Fixing the compass card by the several methods proposed
and illustrated, when the said case is at a distance from the ship, sub-
stantially as described.

page_text: Third. The use of the means thereby obtained for ascertaining and
correcting the deviation of the ship's steering compass, substantially as
described.
In witness whereof, I, the said John Clark, have hereunto set
my hand and seal, this Eighth day of October, in the year of our 5
Lord One thousand eight hundred and seventy-four.