An Improved Apparatus for Attaching to Sextants for Finding the True Horizon in Foggy or Hazy Weather.
Year: 1893

page_text: Date of Application, 31st Oct., 1893
Complete Specification Left, 31st July, 1894-Accepted, 29th Sept., 1894
An Improved Apparatus for Attaching to Sextants for Finding the
True Horizon in Foggy or Hazy Weather.
I FREDERICK JOHN JEFFERSON, of 65 Blake Street, Hull, in the County of
York, Marine Officer, do hereby declare the nature of this invention, to be as
follows:-
The object of this invention is to construct a simple contrivance for affixing to
sextants to produce an artificial horizon when in hazy or foggy weather the true
horizon is obscured.
I construct my invention as follows :-
I employ a piece of metal or the like which consists preferably of a flat plate
having two projections or prongs at right angles, these prongs being parallel to each
other, a pendulum being also employed and being preferably attached to the flat
plate.
This plate is movable and works on a pivot or pivots, and is arranged so that the
parallel prongs work over the horizon glass of the sextant, one at each side, just
below the centre; the pendulum attached to the plate swings backwards and
forwards thus moving the plate and prongs.
For the purpose of fixing the pendulum in position to agree with the height of
the observer above the sea level, I employ an arc marked off in suitable divisions,
such divisions preferably representing feet, this are may be recessed or double, for
the purpose of allowing the pendulum to move between the two arcs thus formed,
so that when the observer knows his height above the sea level, he sets the
pendulum to that number of feet indicated on the arc, by means of a set screw or
the like, thus when the pendulum is set to indicate the number of feet the observer
is above the sea level, he places the telescope of the sextant to his eye and moves
the sextant until one of the parallel prongs is hidden exactly behind the other, the
prongs then being in a line form an artificial horizon which is equivalent to the
true horizon which the haze or the like hides.
The said arc may be single and not recessed or double; when single the pendulum
works preferably behind it and has still the same effect.
For the purpose of supporting the arc I may employ stays from each end of the
parallel prongs, and for the purpose of easily discerning when the prongs are in a
correct line, une hiding the other, they may be painted different colors.
This contrivance is attached to the sextant in any position to allow of the prongs
working over the horizon glass near the centre, so that by means of this invention
the true horizon may be obtained in hazy or foggy weather.
Dated this Thirtieth day of October 1893.
JOHN E. WALSH,
Savile Street, Hull, and Crossley Street, Halifax,
Agent for the Applicant.

page_text: COMPLETE SPECIFICATION.
An Improved Apparatus for Attaching to Sextants for Finding the
True Horizon in Foggy or Hazy Weather.
I, FREDERICK JOHN JEFFERSON of 65 Blake Street Hull in the County of
York, Marine Officer, do hereby, 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:-
The object of this invention is to construct a simple contrivance for fixing to
sextants to provide an artificial horizon when in hazy or foggy weather the true
horizon is obscured.
DESCRIPTION OF DRAWINGS.
Fig. 1. is a front view of part of frame of sextant showing improvements attached
to horizon glass.
Fig. 2. is side view of horizon glass with my improvements attached in a modified
manner when the sextant is held vertically.
Fig. 3. is a plan of my contrivance.
Fig. 4. is a front view of Fig. 2 showing part of my contrivance shewing bracket
with recesses and knife shaped pivots.
Fig. 5. shows cap with bar across for fitting on to telescope.
I construct my invention as follows:-I employ a simple contrivance which
consists preferably of a flat plate A, having two projections or prongs B, B, at right
angles, these prongs being parallel to each other, a pendulum C being also
employed, and being preferably attached to the flat plate A.
This plate A is movable and works on a pivot or pivots D; and is arranged so
that the parallel prongs B, B, work over the horizon glass E of the sextant F, one
at each side, quite in the centre; the pendulum attached to the plate swings
backwards and forwards thus moving the plate and prongs. The said pivot D
works in a bracket G on the frame of the horizon glass E, the pivot has pointed
ends one of which fits in a cup on the said frame, and the other end working in a
cup on the end of the screw H passing through the bracket G, this screw holding the
contrivance in position, and by the unscrewing of which the contrivance can be
easily removed from the sextant.
For the purpose of fixing the pendulum in position to agree with the height of
the observer above the sea level, I employ an arc J marked off in suitable divisions,
such divisions preferably representing feet, this are may be recessed or double for
the purpose of allowing the pendulum to move between the two arcs thus formed,
so that when the observer knows his height above the sea level, he sets the
pendulum to the number of feet indicated on the arc, by means of a screw or the
like K, thus when the pendulum is set to indicate the number of feet the observer
is above the sea level, he places the telescope L of the sextant to his eye' and
moves the sextant until one of the parallel prongs B is hidden exactly behind the
other, the prongs then being in a line form an artificial horizon which is equivalent
to the true or visible horizon which the haze or the like hides. The said arc J
may be single and not recessed or double, when single the pendulum works
preferably behind it and has still the same effect, a small pointer M being turned
up in front to mark where the pendulum is set at.
For the purpose of supporting the arc I may employ stays N from each end of
the parallel prongs, and for the purpose of easily discerning when the prongs are in
a correct line, one hiding the other, they may be painted different colours.
In place of attaching the contrivance to the frame of the horizon glass as shown
at Fig. 1, I may employ a separate pedestal G see Fig. 4 attached to the frame F
of the sextant, this pedestal is screwed or attached in any suitable manner, and is

page_text: carried on the underside (holding the sextant vertically) and over the top E of the
horizon glass, and bent over forming a bracket G', this bracket has holes in it for
the pivot which is of the knife shaped kind to work in. The said bracket has
recessed sides D' see Fig. 4. so that when placing the contrivance on the sextant,
the pivot on the bar or plate A is simply shipped into the said recesses and the
contrivance is suspended, there being no screw required for holding it in position,
the contrivance being simply shipped in and lifted out without any trouble
whatever.
For the purpose of getting a more correct view from the telescope, I employ an
extra cap O for attaching to the far end of the telescope from the eye, this cap has
a hole in it to which is fixed a very thin bar or wire P across the direct centre of
the hole, by getting the three bars in line it assists in getting the artificial horizon.
This contrivance is attached to sextants in any suitable position to allow of the
prongs working over the horizon glass near the centre, so that by means of this
invention the true or visible horizon may be obtained in hazy or foggy weather.
The action is as follows:-
The pendulum is set on the arc, which is divided or set off to scale of 50 or
60 feet at each side from the centre. The higher the person using the sextant is
above the sea level, the more the pendulum swings to the left to be perpendicular
to the horizon which it must always be, supposing the person is 20 feet above the
sea level, the pendulum C is moved to the point marked 20 feet to the left of the
arc J from the centre, and by means of a screw K is secured in that position,
the pendulum being weighted, then falls by gravity into a perpendicular position,
simultaneously moving the top bar A, and its parallel bars B. B, and by getting
these parallel bars in a line, on looking through the telescope L, the artificial
horizon is obtained, as the angle of the tilt is equal to the difference in the line
of sight caused by the person, using the sextant being 20 feet above the level of
the sea.
In place of fixing the contrivance to the horizon glass frame as shown at Fig. 1,
it is preferable to employ a separate pedestal or bracket as shown at Fig. 2, as, if
fixed to the frame of the glass, it weighs the glass down and a correct horizon
cannot be obtained.
Having now particularly described and ascertained the nature of this inven-
tion, and in what manner the same is to be performed, I declare that what I
claim is:
In apparatus before described the movable plate or bar A upon pivots D, with
prongs, projections or parallel bars B. B. working upon each side of the horizon
glass, bracket G, pendulum C, working upon arc J, adjustable by means of the
screw K, substantially as shown and described.
Стпа
JOHN E. WALSH,
Saville Street, Hull, and Crossley Street, Halifax,
Patent Agent for the Applicant.