Improvements in or relating to Mariners' Compasses.
Year: 1892

page_text: Date of Application, 30th Aug., 1892-Accepted, 31st Dec., 1892
Improvements in or relating to Mariners' Compasses.
1. EDWARD SAMUEL RITCHIE, of Newton in the County of Middlesex and
State of Massachusetts, United States of America, Gentleman, 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 :--
Of the accompanying drawings forming a part of this Specification,
Figure represents a vertical transverse section, and Figure 2 is a top view of a
mariner's compass provided with my azimuth circle.
Figure 3 is an enlarged copy of the section of the case E.
Figure 4 is a front view of the case E.
Figure 5 is a front view of the case E, and the front side plate removed.
Figure 6 is a front view of the mirror D and its frame d and support a.
Figure 7 is a vertical section, and Figure 8 is a horizontal section of the
mirror D and its frame d.
Figure 9 illustrates the course of rays from the sun to the card C.
Similar letters refer to similar parts through the several views.
The instrument comprises what is known as an azimuth circle used upon a
mariner's compass, for showing the direction of the sun by the compass card, at
the time of an observation; and the object of my invention is to show the direction
by throwing a line of solar light directly upon the compass and visible to one or
more observers, without inconvenience to them; whereas in the instruments
heretofore used the observer is obliged to look through an eye hole or slit, and to
note the position of a hair line on the card and also on the reflected image of
the sun.
The instrument consists of a ring A with a flange, to rest, and to be turned
round, upon, a mariner's compass bowl B. Attached to the ring A. I place a
support a holding the frame d of a concave cylindrical mirror D, which prefer
to make of a convex cylindrical lens, silvered on its convex side, the frame d is
held on its support a by axis or screws, allowing free motion in a vertical plane
passing through the centre of the ring A, with friction enough to hold it in any
position; the curvature of the mirror is such as will reflect solar rays to a focal
line at e; the frame has a back plate d¹. Directly opposite to the mirror D,
I place a square case E, fixed to the ring A., by a bracket f'; the side of the
case E facing the mirror D, has a narrow slit e; within the case E I place a right
angle prism F in position to receive the solar rays from the mirror D passing
through the slit e, and to reflect them vertically downward; near the lower end of
the case E, place a cylindrical lens, its central line being in line of the centre
of the ring A. Upon the bracket for on the ring A I place a spirit-level H.
The operation is as follows-Solar rays reflected by the mirror D to a focal line
passing through the slit e, are again reflected by the prism F vertically downward
through the cylindrical lens f, and are again brought to a focal line upon the
compass card C as shown in Figure 1. The march of the rays as affected by the
concave mirror D and convex lens is illustrated by Fig. 9; in which the prism F
is removed and the lens fis placed at the same distance in horizontal line; parallel
solar rays i reflected by the mirror D, are brought to a focal line at e, and again
diverge, and fall upon the lens f, and are refracted by it to a focal vertical line
at C. The prism reflector F simply changes the direction from horizontal to
vertical, at same distance, the dotted lines in Fig. 5 show the rays also.
I will remark that used on board a vessel and properly adjusted, the rolling

page_text: motion of the vessel will prevent a constant line of light; but the light will flash
upon the card at the times that the vessel passes the mean of the oscillation.
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. In a mariner's compass the combination of an azimuth circle with the
mirror D, the reflecting prism F, and the cylindrical lens f, substantially as
set forth.
2. In a mariner's compass the combination of an azimuth circle with the ring A,
the mirror D, the case E, and the slit e, substantially as set forth.
Dated this 4th day of August 1892.
EDWARD SAMUEL RITCHIE.
Haseltine, Lake & Co.,
45, Southampton Buildings, London, Agents for the Applicant.