Improvements in Nautical Reckoning or Indicating Instruments.
Year: 1893

page_text: Date of Application, 7th Jan., 1893
Complete Specification Left, 9th Oct., 1893-Accepted, 18th Nov., 1893
[Communicated from abroad by NORMAN R. OLIVER, Her Britannic Majesty's
Consul for Portuguese India, of the British Consulate, Goa.]
Improvements in Nautical Reckoning or Indicating Instruments.
I, GEORGE CROYDON MARKS, of 13 Temple Street, in the City of Birmingham,
Engineer and Patent Agent, do hereby declare the nature of this invention to be as
follows:-
This invention relates to instruments employed for finding the latitude and
longitude, or for ascertaining a ship's position at sea.
The object of my invention is to construct an instrument that shall lessen the
calculations required when ascertaining the latitude and longitude, and also be free
from the errors likely to arise when employing the present ordinary methods and
calculations.
In carrying my invention into effect I construct a number, preferably seven, of
flat and circular or other shaped discs or rings, of brass or other suitable material.
These discs or rings I mount upon or about one common central column or axis in
such manner that whilst a portion of them can be turned or revolved about this
axis when required, the remainder are fixed rigidly to or in connection with the
axis and prevented from turning upon or about it.
The surfaces of the three uppermost discs or rings, are raised slightly above the
surface of the remainder of the instrument, and such upper discs are connected
entirely with the operations relating to the ascertainment of latitude. The four
lower discs or rings, which I preferably form with their upper surfaces on the
same plane or level, are entirely connected with the operations related to longitude.
The central column or axis is either a part of, or rigidly attached to the lowest or
the base disc.
In the uppermost disc I form a central hole or eye suitable for passing over the
upper portion of the central column or axis, so that the disc may be revolved upon
the axis when required. From opposite sides of the disc an arm projects, the
outer ends of such arms being bevelled down, and suitably cut or divided that they
may be employed as verniers for accurately reading the latitude and decliuation
divisions cut upon the disc or ring beneath. This uppermost disc is turned or
revolved by means of a small pinion or tooth wheel, provided with a milled head
suitable for turning with the fingers, and gearing into the teeth cut or formed in
the disc or ring immediately beneath. The two uppermost rings are clamped
tightly together when required by means of a thumb screw and nut, or other
suitable and well known clamping or securing device.
The second disc, or that immediately beneath the uppermost, is also mounted
freely upon the central column or axis in such manner that it can be turned or
revolved about it when required. The working or reading edge of this disc is
divided for rather more than one-half the circumference into degrees and half-
degrees. In conjunction with one of the verniers, herein before described, on the
uppermost disc, these divisions are employed for reading declination, either north
or south. A smaller portion of the working or reading edge is more finely divided,
to be employed as a vernier for reading the true meridian altitude on the disc
beneath it, hereinafter to be described. The extreme edge or periphery of the
second disc for a distance extending to rather more than half the circumference,
has teeth cut or formed upon it for engaging the teeth of a fixed revolving pinion
attached to the disc beneath it. On either side of the centre of the disc a circular
slot or groove is formed, one of which is for the reception of the clamping nut or
screw of the uppermost disc, whilst the other is adapted to the travel of the pinion

page_text: or tooth wheel of the upper disc; its concave surface having teeth formed to suit
the teeth of the pinion.
The third disc consists of a flat ring firmly secured to the disc immediately
beneath it. The face of the disc is divided into four equal major divisions or
quadrants, three of these being sub-divided up to their reading edge into degrees
and half degrees, and lettered and figured to allow of reading the south and north
latitude by the aid of one of the verniers on the uppermost disc, and also for
reading the true meridian altitude in conjunction with the vernier formed on the
second disc as hereinbefore described. The remaining quadrant is not sub-divided,
but in or about the centre of its length is carried or supported the pinion or tooth
wheel, which gears into the teeth formed on the periphery of the second disc.
The fourth disc is fixed securely to the central column or axis in such manner
that it cannot be turned or revolved. I preferably make the central eye or core of
a square form or shape, and make the section of the axis at this part to correspond,
also forming a supporting ridge or shoulder upon the axis immediately beneath the
boss or central portion of the disc. In this manner I securely support and fix the
disc to the central column or axis. The third disc is securely fixed to this fourth
disc as before described, and the second disc is also partially and sometimes wholly
supported by it. The whole of the circumference of the lower half of the disc has
teeth cut or formed upon it, which are engaged by the pinion carried on a lower
disc hereinafter described. The face of the disc is graduated or divided into
degrees and half degrees for reading in conjunction with a vernier attached to a
lower disc, either the east or west longitude.
The fifth disc consists of four portions, preferably formed separately, but all
rigidly secured together. The uppermost part consists of a flat ring having such
an internal diameter as to enable it to fit over the upper portion of the fourth disc
herein before described. This flat ring is secured by screws, rivets or other means
of attachment, to the second portion of the disc immediately beneath it, and it
carries or supports the pinion or tooth wheel, operated by a finger head, which
gears into the teeth formed on the circumference of the fourth disc. By the
turning of this pinion, the whole of the fifth disc is caused to revolve upon the
central column or axis. The face of the uppermost part of the disc is divided into
two circles. The outer circle is graduated up to its outer edge into twenty four
main divisions, representing hours, and each hour is sub-divided into sixty parts
representing minutes of Greenwich time. The inner circle is blank with the
exception of a small portion which is finely divided as a veruier for reading the
longitude in conjunction with the graduations on the fourth disc. The second
portion of the fifth disc is in the general form of a circular dish or trough, the
central portion having an eye formed to suit the central column or axis which
passes through it. The lower part of the periphery has teeth cut or formed round
the entire circumference. This second portion is securely attached by screws or
otherwise, to the third portion or the base of the fifth disc. The fourth portion
consists of a ring secured to the base of the disc, and having an internal circular
rib forming a circular shoulder, which together with a shoulder formed by the base
of the disc, provides a bed or seat for the sixth disc or part of the complete
instrument. This sixth part consists of a ring which is turned or revolved by the
operation of a pinion or tooth wheel, carried by the ring, and gearing into the
teeth formed on the periphery of the second portion of the fifth disc. The time
vernier for accurately reading the Greenwich time graduations or divisions on the
fifth disc, and the local time on the seventh disc, is cut upon or carried by the sixth
disc or part of the instrument.
The seventh disc forms the base and side covering of the complete instrument,
and consists of a circular dish or trough with the central column or axis projecting
from its centre, and its upper portion projecting and forming an internal circular
rib, the face of which is graduated into twenty four major divisions representing
the hours of the local time, each hour division being sub-divided into sixty divisions
to represent minutes.'"

page_text: The
In finding the latitude by the aid of my reckoning instrument it is necessary to
first obtain in the usual and ordinary manner the true meridian altitude of the sun
or of a star, and the true declination thereof for the moment of observation.
declination vernier of the instrument is then set and securely clamped at the given
declination, after which the true meridian altitude vernier is set to the given altitude.
The latitude vernier will now indicate the required latitude to the nearest minute.
In finding the longitude it is necessary to first obtain the local time and the
corresponding Greenwich or chronometer time. The time vernier is then set and
clamped to the given true Greenwich time, and its zero point is afterwards set to the
given local time; when this is accomplished the longitude vernier will indicate the
required longitude to the nearest minute.
When converting the longitude in time into longitude in arc, the zero of the time
vernier is clamped to the zero of the Greenwich time graduations. The time
vernier together with the Greenwich time and longitude vernier graduations are
then together turned or revolved, until the time vernier zero indicates the given
time on the local time graduations of the instrument. The longitude vernier will
then indicate the longitude in arc.
To convert longitude in arc into longitude in time, the time vernier zero is first
clamped to noon on the Greenwich time graduations, and the longitude vernier is
then set to the given longitude in arc, when the time vernier will indicate on the
local time graduations the longitude in time.
To assist in the more accurate reading of the verniers, I sometimes mount a
microscope at the upper extremity of the central column or axis of my instrument,
in such manner that it can be turned and focussed over either of the verniers as may
be required.
I do not limit myself to any particular form or arrangement of my reckoning or
indicating instrument but modify its details and general configuration to suit
varying requirements without departing from the essential features of my
invention.
MARKS & CLERK,
13, Temple Street, Birmingham, Agents for the Applicant.
COMPLETE SPECIFICATION.
Improvements in Nautical Reckoning or Indicating Instruments.
I, GEORGE CROYDON MARKS, of 13 Temple Street, in the City of
Birmingham, Engineer and Patent Agent, do bereby declare the nature of this
invention and in what manner the same is to be performed, to be particularly
described and ascertained in and by the following statement :-
This invention relates to instruments employed for finding the latitude and
longitude, or for ascertaining a ship's position at sea.
The object of my invention is to construct an instrument that shall lessen the
calculations required when ascertaining the latitude, and longitude, and also be
free from the errors likely to arise when employing the present ordinary methods
and calculations.
In order that my invention may be the more clearly understood, I append here-
unto eight sheets of explanatory drawings to be hereinafter referred to.
Sheet 1 shows a plan and elevation of an instrument made in accordance with my
present invention.
Sheet 2. represents sectional views of the instrument, showing the internal
construction and arrangement.
Sheets 3 to 8 inclusive, represent the various parts of the instrument in detail.
The same letters and figures in the different views or illustrations represent the
same parts.
In carrying my invention into effect I construct a number preferably seven, of

page_text: flat and circular or other shaped discs or rings, of brass or other suitable material such
as A, B, C, D, E, F and G in Figure 1 Sheet 1, and in Figures 4 and 5 Sheet 2,
and also as shown in detail from Sheets 3 to 8 inclusive. These discs or rings I
mount upon or about one column or central axis, such as G' in Figure 5 Sheet 2,
in such manner that while a portion of them can be turned or revolved about this
axis when required, the remainder are fixed rigidly to, or in connection with the
axis, and prevented from turning upon or about it.
The surfaces of the three uppermost discs A B and C are raised slightly
above the surface of the remainder of the instrument, and such upper discs are
connected entirely with the operations relating to the ascertainment of latitude.
The four lower discs D E F G, which I preferably form with all their upper or
working or indicating surfaces on the same plane or level, are entirely connected
with the operations relating to the ascertainment of longitude. The central column
or axis G'Figure 5 is either a part of or rigidly attached to the lowest or the base
disc G.
In the uppermost or top disc A shown on Sheets 1 and
and also in detail on
Sheet 3 Figures 6 and 7, I form a central hole or eye Figures 6 and 7, suitable to
allow the upper circular portion of the central column or axis G¹ Figure 5 to pass
through and form a pivot, upon which the disc may be revolved when required.
From opposite sides of the disc the arms bb' project, suitably bevelled down and cut or
divided at their edges, in order that they may be employed as verniers for
accurately reading the latitude and declination divisions cut upon the discs or
rings B and C beneath A, Figure 5 Sheet 2. The disc A is turned or revolved by
means of the small pinion or tooth wheel 1 Figures 4 and 5 provided with a
milled head suitable for turning with the fingers, and gearing into the teeth cut or
formed in the disc or ring B as shown in Figures 4 and 5. The ring or disc A is
tightly clamped to the disc B when required by means of the thumb screw and nut
shown at 2, Figures 4 and 5, or by other suitable and well known clamping or
securing device.
The disc B immediately beneath A which is shown in detail at Figures 8
and 9, is also mounted freely upon the central column or axis in such manner that
it can be turned or revolved about it when required. The working, reading, or
indicating edge of this disc, is divided for rather more than one half the circum-
ference into degrees and half degrees as shown to the right hand in Figure 1. In
conjunction with the vernier b on the disc A, herein before described, these divisions
on B are employed for reading declination either north or south. A smaller portion
of the working or reading edge is more finely divided to be employed as a vernier
for reading the true meridian altitude on the disc C, to be hereinafter described.
The extreme edge or periphery of the disc B for a distance extending to rather
more than one half its circumference has teeth cut or formed upon it for engaging
the teeth of a fixed revolving pinion attached to the disc C. Within the disc B
I form two slots or grooves, one of which as shown to the left hand in Figures 8
and 9, and in the sectional view Figure 5, is for the reception of the clamping nut
or screw 2 of the disc A. The slot shown to the right hand in the figures is
adapted to the travel of the pinion or tooth wheel 1 of disc A, its concave surface
having teeth formed upon it to suit the teeth of the pinion.
The face
The disc C shown in detail by Figures 10 and 11, Sheet 3, consists of a flat
ring and is firmly secured to the disc D beneath it, see Figure 5.
of C is divided into four equal major divisions or quadrants, three of these being
sub-divided up to their reading edge into degrees and half degrees, and lettered
and figured suitably for reading the north and south latitude by aid of the
vernier on the disc A, and also for reading the true meridian altitude in con-
junction with the vernier formed on the second disc as herein before described.
The remaining quadrant is not sub-divided, but in or about the centre of its
length is carried or supported the pinion or tooth wheel 3, Figures 1, 2, 4 and 5,
which gears into the teeth formed at the periphery of the disc B as herein before
describe:l.

page_text: The disc D shown in detail by Figures 12 and 13 Sheet 3 is securely fixed to
the central column or axis. I preferably make the central eye or core of a square
form or shape, and make the portion of the axis fitting into the eye of a square
section to suit the same, also forming a supporting ridge or shoulder upon the axis
immediately beneath the boss or central portion of D as shown at Figure 5.
The
disc C is securely fixed to the disc D as before described, and the revolving disc B
is partially and sometimes wholly supported by D. The whole of the circumference
of the lower part of the disc has teeth cut or formed upon it, which are engaged by
the pinion 4, Figures 1, 2, 4, and 5 on the disc E, to be hereinafter described.
The face of D is graduated or divided into degrees and half degrees, for reading,
in conjunction with a vernier formed on the disc E as hereinafter described, either
the east or west longitude.
The disc E illustrated by the detail views Figures 14 and 15, Sheet 4, is made
up of four parts preferably formed separately, but all rigidly secured together.
The upper part E', Figures 5 and 15 consists of a flat ring having such an internal
diameter as will enable it to fit over and on to the ring D for the purpose of keeping
the same in position in the manner indicated in Figure 5. E' is secured to the portion
of E immediately beneath it by screws or other suitable means of attachment, and it
carries or supports the pinion or tooth wheel 4, Figures 12, 4 and 5, operated by a
finger head piece, which gears into the teeth formed at the circumference of the disc D
as hereinbefore described. By the turning of this pinion the whole of the disc E is
caused to revolve upon the central column or axis G' Figure 5. The face of E is cut
or divided upon its outer circumference into twenty four main divisions, representing
hours, and each hour is subdivided into sixty parts representing minutes of Green wich
or standard time. The inner circumference is blank with the exception of a small
portion which is finely divided as a vernier for reading the longitude in conjunction
with the graduations formed upon the disc D as hereinbefore described.
sub-part E is shown in further detail at Figures 16, 17 and 18 Sheet 5.
The
The second portion E of the disc E is. in the general form of a circular dish or
trough as shown in the sectional view Figure 15, and in greater_clearness at
Figures 19 and 20 Sheet 5, which are detail views of the sub-part E. An eye
or circular hole is formed at the central portion of E2 to suit the portion of the
central column or axis which fits within it. The lower part of the periphery of E'
has teeth cut or formed around its entire circumference. E' is attached by screws
or otherwise to the portion or sub-part E³ which forms the base of the entire
part E as shown at Figure 15. The sub-part E3 is shown in detail by the
Figures 21 and 22, and the sub-part E by the Figures 23 and 24, Sheet 6.
E consists of a ring secured to the base E³, and having an internal circular rib
which together with the projecting rib or shoulder of the sub-part E³ provides a
double abutment against which the nut of the clamping screw at 6 Figures 4 and 5,
is tightly pressed when the screw is turned for the purpose of clamping the part E
and the part F, in order that they may revolve together as one piece for the purpose
hereinafter described. The part F, shown in detail by Figures 25 and 26, consists
of a ring which is turned or revolved by the operation of the pinion or tooth
wheel 5, carried by F, and gearing into the teeth formed at the periphery of the
sub-part E? hereinbefore described. The time vernier for accurately reading
the Greenwich or standard time graduations on the face of E and the local time
on the disc G, hereinafter described, is cut upon or carried by this part F of the
instrument.
The disc G forins the base of the complete instrument. As shown by Figures 27
and 28, Sheet 7, it consists of a circular dish or trough with the central column or
axis G' Figure 5, projecting from its centre, and its upper portion projecting to
form an internal circular rib, the face of which is graduated into twenty four
major divisions representing the hours of the local time, each hour division being
sub-divided into sixty divisions to represent minutes. I preferably construct the
part G of two sub-parts 1 and 2 securing them together by screws as shown in
Figures 27 and 28, or by other suitable method of attachment: The sub-part G'

page_text: is shown by Figures 29 and 30 and the sub-part G2 by Figures 31 and 32
Sheet 8.
Details of the form of clamps, and pinions or tooth wheels with their milled
finger heads, which I preferably employ, are shown by the illustrations at
Figures 33 and 34 Sheet 7.
The clamps 2 and 6 and the pinions 1, 3, 4 and 5 are not shown in the exact
positions in Figure 5, Sheet 2, but for the sake of clearness in showing the mechanism,
they are drawn as if all were situated on the line a b Figure 4.
In finding the latitude by the aid of my reckoning instrument, it is necessary to
to first obtain in the usual and ordinary manner the true meridian altitude of the
sun or of a star, and the true declination thereof for the moment of observation.
The declination vernier of the instrument is then set and securely clamped at the
given declination, after which the true meridian altitude vernier is set to the given
altitude. The latitude vernier will now indicate the required latitude to the nearest
minute.
In finding the longitude it is necessary to first obtain the local time and the
corresponding Greenwich or chronometer time. The time vernier is then set and
clamped to the given true Greenwich time, and its zero point is afterwards set to the
given local time; when this is accomplished the longitude vernier will indicate the
required longitude to the nearest minute.
When converting longitude in time into longitude in arc, the zero of the time
vernier is clamped to the zero of the Greenwich time graduations. The time
vernier together with the Greenwich time and longitude vernier graduations, are
then together turned or revolved, until the time vernier zero indicates the given time
on the local time graduations of the instrument. The longitude vernier will then
indicate the longitude in arc.
To convert longitude in arc into longitude in time, the time vernier zero is first
clamped to noon on the Greenwich time graduations, and the longitude vernier is
then set to the given longitude in arc, when the time vernier will indicate on the
local time graduations the longitude in time.
To assist in the more accurate reading of the verniers I sometimes mount a micro-
scope at the upper extremity of the central column or axis of my instrument, in such
a manner that it can be turned and focussed over either of the verniers as may be
required. The form which I preferably employ is shown at Figure 2, and by the
plan at Figure 3.
I do not limit myself to any particular form or arrangement of my reckoning or
indicating instrument, nor to the particular form or methods of construction of the
various parts herein before set forth, and illustrated in the accompanying drawings,
but modify the instrument, its details and general configuration to suit varying
requirements without departing from the essential features of my invention.
Although I preferably combine all the parts necessary for the calculation of
latitude and longitude in the one complete instrument as herein before described, yet
I sometimes make separate and distinct instruments for the two separate operations.
Thus, in constructing an instrument for the calculation of latitude, I combine discs
or rings such as A B and C with the necessary operating mechanism and the
clamping device for securing A and B together when required, substantially as
hereinbefore described, and form the same into one complete and separate instrument.
In like manner I form a complete instrument for the calculation of longitude by
combining discs such as D, E, F, G, with mechanism for imparting the required
movements, and other parts substantially as hereinbefore described and illustrated
in the accompanying drawings.
Having now particularly described and ascertained the nature of my said inven-
tion, and in what manner the same is to be performed, I declare that what I
claim is :-
1. The construction of nautical reckoning or indicating instruments, having a
series of discs or rings, suitably divided or graduated, with the mechanism for

page_text: giving the necessary relative movements, for calculating the latitude and longitude,
or for ascertaining a ship's position at sea, substantially as herein before described
and as illustrated in the accompanying drawings.
2. The combination and arrangement of divided or graduated discs, or the like
parts, with tooth gearing or other mechanism for giving the necessary relative
movements to such discs or like parts, and clamps or other securing devices for
rigidly connecting the same together when required, substantially as and for
the purposes hereinbefore described and as illustrated in the accompanying
drawings.
3. In a latitude and longitude calculating instrument, the arrangement of a series
of discs about a central column or axis substantially as and for the purposes herein-
before described, and as illustrated in the accompanying drawings.
4. In a longitude, or latitude and longitude calculating instrument, the construc-
tion of a disc such as G forming the base of the instrument, having a central
column or axis formed upon it or attached thereto carrying other discs or rings, and
having its outer face graduated for indicating the local time, substantially as herein-
before described and as illustrated in the accompanying drawings.
5. In a longitude, or latitude and longitude calculating instrument, the construc-
tion of a disc such as E for indicating on its outer face the Greenwich or standard
time, and capable of supporting and securing other discs substantially as herein-
before described, and as illustrated in the accompanying drawings.
6. In a latitude, or latitude and longitude calculating instrument, the construction
of a graduated disc such as B having circumferential teeth, and having an internal
segmental rack or series of teeth formed therein, and a groove or channel for
receiving the tightening or securing device, substantially as and for the purposes
hereinbefore described and as illustrated in the accompanying drawings.
Dated this 6th day of October 1893.
MARKS & CLERK,
13, Temple Street, Birmingham, Agents for the Applicant.