IMPROVEMENTS IN MAGNETIC COMPASS CARDS FOR IRON AND OTHER SHIPS
Year: 1873

page_text: LETTERS PATENT to Frederick Arthur Paget, of 1, Seymour Chambers,
York Buildings, Adelphi, in the County of Middlesex, Civil and
Mechanical Engineer, for the Invention of "IMPROVEMENTS IN
MAGNETIC COMPASS CARDS FOR IRON AND OTHER SHIPS."--A communication
from abroad by Alexander Kalmar, Lieutenant in the Imperial
Austrian Navv.
PROVISIONAL SPECIFICATION left by the said Frederick Arthur Paget
at the Office of the Commissioners of Patents, with his Petition,
on the 1st January 1873.
I, FREDERICK ARTHUR PAGET, of 1, Seymour Chambers, York
Buildings, Adelphi, in the County of Middlesex, Civil and Mechanical
Engineer, do hereby declare the nature of the said Invention for
"IMPROVEMENTS IN MAGNETIC COMPASS CARDS FOR IRON AND OTHER SHIPS," to be
as follows:
'

page_text: which as is well known the deviations of the magnetic needles from the
correct magnetic meridian, due to local attractions, are considerable.
This card, termed "Kalmar's dromoscopic card," is formed in such wise
that the eye of the steersman or of the officer of the watch can at once,
without referring to tables note the deviation at any point from the
correct magnetic course, and steer in the true direction accordingly.
It is fixed on the compass needle in the same way, but instead of the
ordinary compass card. This compass card in its entirety is printed or
drawn with two concentric cards, a smaller one within the outer. The
outer one is intended to indicate the compass courses to be steered, the
inner one the corresponding magnetic courses resulting from the
deviations. For this purpose a white zone or annular space about one
or two inches in width is left between the two concentric cards, and
preferably from one-half point to another lines are drawn connecting the
magnetic courses of the inner card with the appropriate compass courses
on the outer card, as determined by swinging the ship or otherwise.
The use of the dromoscopic card is readily understood. The actual
magnetic courses, either as found from the map or as signalled by the
admiral in the case of a fleet can be at once steered from by being read
on the inner card, and by the corresponding line or space being followed
by the eye up to the point on the outer compass card touched by it. In
a similar manner, but reversely, the magnetic course steered may be at
once ascertained and marked on the map. It is evident that this
dromoscopic compass card can, like any ordinary compass card, be used
for taking bearings, and therefore has not the disadvantages of the well-
known "distorted" compass card.
The several half points on the two cards are preferably connected by
means of red lines on a white ground, when the compass is lighted from
above, or with a transparent card lighted from below; the lines are by
preference white on a black ground.
With ships causing considerable errors when heeling over, either to
windward or leeward, the errors due to average angles of from five to
seven degrees are to be determined, and lines of different colours marked
to appropriately connect the different points, as above indicated.
On the Drawing annexed the northern half of the card is shewn as it
would be printed or drawn for being lighted from above, the southern
half for being illuminated from below.

page_text: In case spare cards are not kept in stock, and that eventual changes
in the ship's magnetism take place, these have to be marked on a zone
of white paper stuck on the intermediate annular space, and it is then
preferable to print or draw the inner graduated circle within the inner
compass card, instead of on the white zone, and preferably with
extremely fine lines, in order not to disturb the view of the half and
quarter points of the magnetic compass card.
SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said Frederick Arthur Paget in the Great Seal Patent
Office on the 24th June 1873.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, FREDERICK
ARTHUR PAGET, of 1, Seymour Chambers, York Buildings, Adelphi,
W.C., London, in the County of Middlesex, Engincer, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the First day of January, in the year
of our Lord One thousand eight hundred and seventy-three, in the
thirty-sixth year of Her reign, did, for Herself, Her heirs and successors,
give and grant unto me, the said Frederick Arthur Paget, Her special
licence that I, the said Frederick Arthur Paget, my executors,
administrators, and assigns, or such others as I, the said Frederick
Arthur Paget, 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 Ircland, the Channel Islands, and Isle of Man, an
Invention for "IMPROVEMENTS IN MAGNETIC COMPASS CARDS FOR IRON AND
OTHER SHIPS," a communication from abroad by Alexander Kalmar,
Lieutenant in the Imperial Austrian Navy, upon the condition (amongst
others), that I, the said Frederick Arthur Paget, my executors or
adminstrators, by an instrument 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.
:

page_text: NOW KNOW YE, that I, the said Frederick Arthur Paget, do hereby
declare the nature of the said Invention, and in what manner the same
is to be performed, to be particularly described and ascertained in and
by the following statement :-
These improvements relate to the cards for the standard and steering
compasses used in iron, steel, composite, and armour plated ships, in
which, as is well known, the deviations of the magnetic needles from
the correct magnetic meridian, due to local attractions, are considerable.
This card termed "Kalmar's dromoscopic card" is formed in such wise
that the eye of the steersman or of the officer of the watch can at
once without referring to tables note the deviation at any point from
the correct magnetic course, and steer in the true direction accordingly.
It is fixed on the compass needle in the same way as but instead of
the ordinary compass card. This compass card in its entirety is
printed or drawn with two concentric cards, a smaller one within the
outer. The outer one is intended to indicate the compass courses to
be steered, the inner one the corresponding magnetic courses resulting
from the deviations. For this purpose a white zone or annular space
about one or two inches in width is left between the two concentric cards,
and preferably from one half point to another lines are drawn
connecting the magnetic courses of the inner card with the appropriate
compass courses on the outer card, as determined by swinging the ship,
or otherwise.
The use of the dromoscopic card is readily understood. The actual
magnetic courses, either as found from the map or as signalled by the
admiral in the case of a fleet, can be at once steered from by being
read on the inner card and by the corresponding line or space being
followed by the eye up to the point on the outer compass card touched
by it. In a similar manner but reversely the magnetic course steered
may be at once ascertained and marked on the map. It is evident that
this dromoscopic compass card can like any ordinary compass card be
used for taking bearings and therefore has not the disadvantages of
the well known "distorted " compass card.
The several half points on the two cards are preferably connected
by means of red lines on a white ground when the compass is lighted
from above, or with a transparent card lighted from below; the lines
are by preference white on a black ground.

page_text: With ships causing considerable errors when heeling over either to
windward or leeward, the errors due to average angles of from five to
seven degrees are to be determined and lines of different colours marked
to appropriately connect the different points, as above indicated.
On the Drawing annexed, the northern half of the card is shewn as it
would be printed or drawn for being lighted from above, the southern
half for being illuminated from below.
In case spare cards are not kept in stock, and that eventual changes
in the ships' magnetism take place, these have to be marked on a zono
of white paper stuck on the intermediate annular space, and it is then
preferable to print or draw the inner graduated circle within the inner
compass card instead of on the white zone, and preferably with
extremely fine lines, in order not to disturb the view of the half and
quarter points of the magnetic compass card.
In witness whereof, I, the said Frederick Arthur Paget, have
hereunto set my hand and seal, this Twenty-fourth day of June
in the year of our Lord One thousand eight hundred and
seventy-three.
FRED AT PAGET. (T.α)