NEW OR IMPROVED APPARATUS FOR MECHANICALLY SOLVING PROBLEMS IN CONNEXION WITH THE RULE OF THE ROAD AT SEA
Year: 1875

page_text: PROVISIONAL SPECIFICATION left by John McFarlane Gray at the
Office of the Commissioners of Patents, with his Petition, on the
27th March 1875.
I, JOHN MCFARLANE GRAY, of York Grove, Queen's Road, Peckham,
in the County of Surrey, Chief Examiner of Engineers, Marine
Department, Board of Trade, do hereby declare the nature of the said
Invention for "NEW OR IMPROVED APPARATUS FOR MECHANICALLY SOLVING
PROBLEMS IN CONNEXION WITH THE RULE OF THE ROAD AT SEA," to be as follows:-
My Invention relates to apparatus for mechanically solving problems
in connection with the rule of the road at sea, which apparatus I con-
struct with discs or dials and sight arms or pointers, the discs or dials
being marked or cut in such manner that when one of the said discs or
dials is turned to the position corresponding to the direction of the wind
in relation to the vessel whereon the apparatus is being used, which
vessel I will for clearness call A, and another disc or dial is turned to
the position corresponding to the direction in which another ship which

page_text: I will call B is seen from A, the apparatus will then show according to
any rule of the road for which it is constructed which of the vessels A
or B has to keep clear of the other, and at the same time will indicate
the courses possible for either vessel, or it may be for both vessels, as
limited by the direction of the wind and by the light screens; in other
words, in the latter case the apparatus will show all that can be deduced
from these limitations on board A as to the courses possible to B, and on
board B as to the courses possible to A. A moveable compass card or
disc may be combined with the apparatus to indicate the directions
in relation to the cardinal points when that is required.
One arrangement of my apparatus is constructed with four discs as
follows A casing constructed as herein-after described is connected
by a neck or centre piece to a suitable backing.
Upon the neck or centre piece is arranged a compass card or disc
whose rim extends beyond the periphery of the casing. This compass
card or disc I will call disc No. 1. A second disc, which I will call
No. 2 has its rim marked for head, stern, beam, port, and starboard,
with intermediate divisions in points of a circle. This disc No. 2 with
a ring at the circumference and a complete back forms the casing above
referred to.
Disc No. 3 is a complete circle; its face is by marking divided into
two concentric portions of about equal width and two sets of divisions
being points of a circle are indicated each by an outline of a hull, in
plan those of the outer set pointing to the centre, and those of the inner
set pointing to the circumference of the apparatus. This No. 3 disc is
furthermore divided into three sectors, onc sector containing twelve
points of a circle made black or of a dark color, another sector con-
taining ten points made red, and the third sector containing ten points
made green; from left to right these divisions are in the order of black,
green, and red; in front of this disc and partly covering its face is disc
No. 4; it is divided into two concentric portions with the same radii as
those of No. 3 disc and is provided or marked with a wind index, vane,
or line. This disc is formed with a central circular portion through
which passes a centre piece or neck from No. 3 disc, which centre piece
carries the sight arm or pointer made to
turning No. 3 disc. The inner of the
disc at the side from which the wind
serve also as a thumb piece for
two concentric portions of No. 4
is coming and on which a wind

page_text: vane or pointer is shewn is marked black for six points of a circle on
cach side of the wind vanc, and the segment containing the other
twenty points is cut out to shew the marks on No. 3 disc. The outer of
the two concentric portions of No. 4 disc at the opposite side to the
wind vane is marked black for six points on each side of that diameter,
and the segment containing the other twenty points is cut out.
Between the two concentric portions of the disc is a narrow ring, and
there is another ring forming the periphery of the disc; discs Nos. 3 and
4 are embraced by the case, of which disc No. 2 is the face; the sight arm
or pointer on the centre of disc No. 3 is marked to point in the direction
in which any ship may be seen from vessel A; it points to the centre of
the black sector of its disc.
The narrow ring which is at mid radius of disc No. 4 is colored
through one semicircle to represent that the vessel B has to keep clear
of the vessel A, when the sight arm points over that portion of the circle
and the remainder of the ring is colored differently to indicate that when
the sight arm points over it the vessel has to take care of vessel B; there
is a break in the last mentioned or danger part of the ring signal;
through a portion of the are the danger ring is transferred to the cir-
cumference of the disc just inside of the general inner line of disc No. 2,
which has on the inside a projection extending over a certain are just
broad enough to cover the transferred or outer danger mark of disc
No. 4. When the position of the seen light and the direction of the wind
indicated by these respective parts are relatively such that there is little
chance of the vessels coming near each other, the transferred danger
mark will be hidden by the projection of disc No. 2. Disc No. 4 is
divided as much of it as remains in the same way as disc No. 3, and the
little hull outlines are put on it in the same fashion with numbers or
marks for convenience of setting and to distinguish the positions where
either vessel is close hauled and where it has the wind free; the hull
outlines shew the possible courses of the two ships; the inner set refers
to ship A, and the outer set refers to ship B.
My apparatus can be otherwise constructed to shew only which ship
has to keep clear without exhibiting the relative positions of the ships.
A disc which I will call No. 1 representing bearings from the ship A,
head, stern, beam, &c., in points, has a disc No. 2 centred on it. This
disc No. 2 has a wind vane line marked on it at one side to denote

page_text: the direction from which the wind is coming, and a diameter is drawn
to the circle at ten and a half points to the left of the wind when the
observer is facing the wind, and five and a half points to the right of the
wind vane.
A semicircle containing the wind vane is marked to shew
that vessels seen over that semicircle must take care of A, and the other
semicircle is differently marked to shew that vessels seen over that semi-
circle must be taken care of by A. The hull disc No. 1 carries a small
overlapping segment to cover the danger intimator over those positions
of the seen ship, where as described above there is the presumption that
the vessels will not come near each other; the overlapping arc extends
three and a half points on each side of right a head on the hull disc.
The danger semicircle is broken as has been already described with
reference to the other arrangement over a portion of two and a quarter
points on each side of the radius opposite to the wind vane; the omitted
part is there carried out to the circumference as in the former arrange-
ment to be overlapped by the projecting segment on the hull disc. This
apparatus may have combined with it arrangements resembling those of
the previously described apparatus for representing the possible courses
of the seen ship.
In some cases I construct my apparatus with a sight arm extended
rearwards and having jointed to its rearward part or extremity a hull
skeleton to represent the position of the vessel, by which the apparatus
is carried. The hull skeleton is so jointed that when the apparatus is
fixed in a vertical position the centre line of the hull skeleton shall be
parallel with the vertical centre line of the apparatus; thus with the
representation of the courses of the seen ship it will constitute a nearly
true representation in plan of the relative positions of the two ships,
thereby forming a guide to the best way of keeping clear of the seen
ship when that is indicated to be the duty of the vessel carrying the
apparatus.
The angles and arcs herein-before specified which apply to both
arrangements of my apparatus as herein described are given as my
rendering of the present international rule of the road at sea, but as
my Invention will have to be formally sanctioned by Government before
its indications can be taken as authoritative, I reserve the right to modify
those angles or arcs, should the proper authorities otherwise construe
the meaning of the present law or if they should alter the rule

page_text: Instead of having vessel B represented on the inner circle, and vessel
A on the outer circle, this arrangement can be reversed, other consequent
changes being made.
As is obvious the apparatus herein-before described may be otherwise
modified to suit circumstances without departing from the distinctive
character of my Invention, and the discs may in some cases be con-
structed of glass or transparent material and be illuminated at night.