Improvements in Prisms for use in connection with Compasses for Taking Bearings or Observations at Sea or on Land.
Year: 1892

page_text: Date of Application, 12th May, 1892
Complete Specification Left, 13th Feb., 1893-Accepted, 8th Anr., 1893
PROVISIONAL SPECIFICATION.
Improvements in Prisms for use in connection with Compasses for
Taking Bearings or Observations at Sea or on Land.
I, GEORGE CHARLES LILLEY of 10 London Street in the City of London,
Optician and Compass Maker do hereby declare the nature of my invention to be
as follows:-
My invention relates to prisms which are used with compasses for bringing the
indications of the compass card into view in convenient proximity to a distant
object in taking bearings or observations at sea or on land. Such prisms as
hitherto made have the defect that they reverse the indications of the compass
card and therefore present them to the observer in a position in which it is difficult
to read them, and it is the object of my invention to remedy this defect and provide
a prism which will present the indications of the compass card in the correct
position so that they can be read with facility and the prism may also be provided
with means for magnifying the indications.
According to my invention I provide the prism with an additional reflecting
surface or surfaces by which the indications of the compass card are erected or
caused to be presented to the observer in correct position. If the indications are
to be magnified I provide the prism with a magnifying lens which may take the
form of a plano-convex strip cemented to the prism at the part where the indica-
tions are viewed I may for facility and cheapness of manufacture, in cases where a
prism of considerable width is required form it by placing two or more prisms
together side by side and if necessary cementing them together and then applying
one magnifying lens across the prisms so combined.
Dated this 12th day of May 1892.
J. H. JOHNSON & Co.,
47, Lincoln's Inn Fields, London, W.C., Agents.
COMPLETE SPECIFICATION.
:
Improvements in Prisms for use in connection with Compasses for
Taking Bearings or Observations at Sea or on Land.
1 GEORGE CHARLES LILLEY of 10 London Street in the City of London
Optician and Compass Maker do hereby declare the nature of my said invention and
in what manner the same is to be performed to be particularly described and
ascertained in and by the following statement:—
My invention relates to prisms which are used with compasses for bringing the
indications of the compass card into view in convenient proximity to a distant
object. In taking bearings or observations at sea or on land such prisms as have
hitherto been made have the defect that they reverse the figures of the compass
card and therefore present them to the observer in a position in which it is
difficult to read them unless the compass card is arranged with inverted or reversed
figures in which case it is inconvenient to read the same when used for ordinary
inspection and it is the object of my invention to remedy this defect and provide a
prism which will present the indications of the compass card in the correct or
direct position so that they can be read with facility the said figures on the compass
card being direct as an ordinary compass card is made and the prism may also be
provided with means for magnifying the indications.
In Figure 1 of the accompanying drawing I have shewn a prism made according
to my invention. I provide the prism with an additional reflecting surface or

page_text: surfaces (as at a) by which the indications of the compass card are erected or
caused to be presented to the observer in correct position. The line at 6
represents the compass card and the lines c indicate the lines of direction of the
rays from the card. If the indications are to be magnified I provide the prism with
a magnifying lens which may take the form of a plano-convex strip cemented to
the prism at the part where the indications are viewed (as shewn at d) I may for
facility and cheapness of manufacture in cases where a prism of considerable width
is required form it by placing two or more prisms together side by side and if
necessary cementing them together and then applying one magnifying lens across
the prisms so combined.
Figure 2 shews in sectional elevation and Figure 3 in plan a compass with a
prism made in accordance with my invention mounted in its box or casing and with
its adjuncts for taking an observation.
It is shewn as being mounted on a bar e which is provided with a pin f to fit
into an opening in the central stud g so that the device can be turned upon this
centre to bring it into position for making the observation but if desired the prism
and its adjuncts may be connected to a rim which can be moved round upon the
edge of the compass bowl above the card. h is the slitted standard at one end of the
bare through which the observer looks in taking the observation. ¿ is the casing
which holds the prism and
alignment the object observed
correct position by the prism.
at a considerable altitude and
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:-
:-
is the wire or thread which is used to bring into
and the indications of the compass card presented in
k is the receiving mirror for reflecting the sun when
are shades for use in strong sunlight.
A prism for use with compasses for taking bearings or observations at sea or on
land having an additional reflecting surface substantially as and for the purpose
herein before explained.
Dated this 9th day of February 1893.
J. H. JOHNSON & Co.,
Agents.