IMPROVEMENTS IN MARINERS' COMPASSES, AND IN APPARATUS CONNECTED THEREWITH
Year: 1884

page_text: .COMPLETE SPECIFICATION.
I GEORGE DOWNING, of 8 Quality Court, Chancery Lane, in the County of
Middlesex, Patent Agent, do hereby declare the nature of my said Invention
for "IMPROVEMENTS IN MARINERS' COMPASSES, AND IN APPARATUS CONNECTED
THEREWITH A communication from abroad by Robert, Lewis Sleator, of St. Johns,
Newfoundland Optician 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 invention is to effect improvements in the construction of
mariners' compasses, and in apparatus connected therewith.
I construct the compass card or dial of mica, glass, horn, mother of pearl,
vulcanite, brass, or other non-magnetic material. If made of metal or other opaque
material, the points are engraved and also indicated by means of saw-cuts, in order
that light may freely pass through the same; or the same may be bored with holes
for the same purpose, or a combination of holes and saw-cuts may be used. If
made of transparent material the points may be engraved, printed, painted,
photographed, or otherwise clearly indicated. The compass card may also be made
of a combination of such materials, the central portion being used for night service,
and the outer, annular portion for day service.
The card is mounted in the ordinary binnacle, or at the mast head, deck, or in
any other position available for reflecting the saine at night and observing the saune
by day. By mounting the compass just above the deck and providing for rays of
artificial light passing downwards through a hole in the deck, the position, and
bearings of the compass may be indicated, to a greatly enlarged scale, on the cabin
table, or in the chart room, or other convenient part of the ship for observation,
or by being reflected on a sheet of ground glass, the readings may be observed and
taken from both sides of such glass, simultaneously, and from different parts of the
vessel. By means of prisms the position and bearings of the compass may be
diverted and reflected at any angle to any suitable part of the vessel.
And in order that my said invention may be clearly understood, referenco is
hereby made to the accompanying drawings, in which similar letters of reference
indicate corresponding parts.
Fig. 1 is a sectional elevation of any Invention, as ordinarily fitted. a is the
compass card, bb are the usual gimbals, c is a plano-convex glass and c¹ is a convexo-
planc glass, which glasses c and c¹ together condense and concentrate the rays of
light from above to and through the double convex glass y and convex meniscus g¹
(forming a pair of objectives) to and, upon a table at i-The condenser glasses c
and c are surmounted by a reflector d d of the shape of a frustuin of a cone; and
this reflector is surrounded by a reservoir for oil or spirit from which the burners e

page_text: are fed, thus forming an overhead lamp. fis the chimney to the lamp. h is the
annular diaphragm or stop, through which the pencil of light passes.
The focus of the enlarged rays may be adjusted in the usual manner by
arranging the relative distances of the glasses say, from 1 foot to 30 feet, and, by
suitable arrangements of lenses, prisms, and reflectors may be directed to any part
of the vessel within rango.
The source of light may be derived from electricity, lime, oxyhydrogen, oxy-
calcium, ether-oxygen, magnesium, gas or oil.
The heat of combustion may be utilised in keeping the lenses sufficiently warm
to drive off moisture, more especially in foggy weather.
The upper part of the apparatus is or may be made moveable, so that it may be
'removed in the day time, to render it visible from the outside, and the whole is
well secured and protected against rough weather.
The centre (night) card may be set to indicate the true north point, and the
variation altered to suit different latitudes.
Fig. 2 shews one of my compass cards, the central portion (/) of which is made
of transparent material, and the points indicated as shown, or by means of colors or
otherwise, through which the rays of light may freely pass.
In Fig. 3 the central portion / is shewn provided with saw-cuts, as from m to n
to indicate the cardinal points, and shorter intermediate saw-cuts to indicate other
points of the compass.
In each figure (2 and 3) the outer portion forms a suitable card for day-service,
and the outer and inner portions together form one card and revolve together on
the ordinary centre.
The lower portion of the compass box is also made of transparent material.
One of the advantages, obtained from the use of my invention, is, that the points
may be sub-divided into a greater number of parts than heretofore, and the course
laid may be steered with greater accuracy, thereby shortening the course to be sailed.
The main points of the compass N. S. E. W. may be colored with distinctive
colors, as red, blue, yellow, and green, and that part of the are which is more
directly in use may be projected to an enlarged scale to indicate the course stecred.
The solid magnet alone may be used in a similar manner, with a prism to
project its direction on a card, painted and placed upright either stationary or
revolving on a pivot.
My invention renders a small compass available for all purposes, and this may
be pivoted through or in jewels, with glass on each side for a mast head; thus
rendering unnecessary the large and heavy compasses now in use.
Having now particularly described and ascertained the nature of my said
invention, and in what manner the same is to be performed, I declare that what
I claim is
1. The manufacture and use of compass cards constructed wholly or partially
of transparent or semi-transparent materials, or having holes, saw-cuts, or equi-
valent devices, formed therein, substantially as and for the purposes herein before
described and shown on the drawings Figs 1, 2, and 3.
2. The manufacture use and application of illuminating apparatus, substantially
as and for the purposes herein before described and shewn on the drawings.
3. The respective combinations of parts forming respectively my improvements
in Mariners Compasses and in apparatus connected therewith substantially as
herein before described and shewn on the drawings.