An Improved Military Sketching Instrument.
Year: 1895

page_text: Date of Application, 29th Apr.,
1895
Complete Specification Left, 14th Jan., 1896-Accepted, 29th Feb., 1896
PROVISIONAL SPECIFICATION.
An Improved Military Sketching Instrument.
The Hon. GILBErt Legh, 8 Cadɔgan Square, London S.W. Captain Grenadier
Guards, HENRY WALLICH MACLEAR Major Retired Pay 42 Holbein House
Sloane Square London, S.W. do hereby declare the nature of this invention to be
as follows:-
A protractor-transparent or opaque-semi-circular in shape; containing a
declination compass, and six or more scales on the diameter edge, let into the
protractor, but moveable.
The above combined with a hinged ruler facilitates the taking of bearings, and
also enables the observation of vertical angles to be taken.
The ruler is hinged about the centre and about 1 foot in length—contains a
mirror and spirit-level, together with scales.
THE HON. GILBERT LEGH,
Captain Grenadier Guards,
8 Cadogan Square, London, S.W.
H. W. MACLEAR,
Major, Retired Pay,
Holbein House, Sloane Square, London, S.W.
We, The Hon. Gilbert Legh, 8 Cadogan Square, London, S.W. Captain
Grenadier Guards, HENRY WALLICH MACLEAR, Major Retired Pay, 42 Holbein
House, Sloane Square, London, S.W. do hereby declare the nature of this inven-
tion and in what manner the same is to be performed to be particularly described
and ascertained in and by the following statement :-
This invention relates to a portable military sketching instrument consisting of a
protractor and a hinged ruler, the latter being in the form of a case to contain the
protractor and to hold it for surveying purposes, as we shall describe referring
to the accompanying drawings.
Fig. 1 is a perspective shewing the case closed, Fig. 2. shews it open in condition
for observing an azimuth or bearing.
Fig. 3 is a plan and Fig. 4 a transverse section of the protractor.
Fig. 5 is a plan shewing the protractor in the case with guide bar set; and
Fig. 6 is a perspective shewing the protractor and case applied as a clinometer.
In a case A which may be of wood provided with a lid B hinged to it, we
accommodate a protractor C preferably made of transparent material such as
celluloid, and having mounted on it a magnetic needle cover which is a glass c¹
marked with two diametral lines N S and W E crossing each other at right angles.
The glass so marked is held in a rim which can be turned round, so as to bring
the line W E, when required, to coincide with a line c³ marked on the protractor.
P

page_text: The degree divisions are preferably numbered both ways for convenience of
reading from both ends. In the straight side of the protractor we accommodate
three scales e, any one of which can be brought to the front. These being
graduated on both sides furnish 6 scales for plotting or reading maps or plans,
There might however be a greater or less number of such scales, which are held
in plan by a turn buckle c.
The case A has pivotted on one side a bar D with a pin d projecting upwards
from its middle on which when turned so as to cross the case as shewn in Fig. 2,
ean be engaged an eye provided at the centre of the straight side of the
protractor.
At the front of the case is pivotted an eye piece F which can be turned up to
take a vertical position when the lid is raised as shewn in Fig. 2. The lid B itself
has a long central slot with a wire or thin metal strip b stretched along it to form
a sight line, and on each side of the slot is fixed a mirror 6. For taking a
bearing or azimuth a sight is taken through the eye piece F and past the
sight line and the protractor is turned on the pin d until the needle points to N as
can be seen by the observer in the mirror b. The bearing of the object is then
determined by the graduation of the protractor which coincides with the fiducial
line a.
As shewn in Fig. 5 the bar D can be set to any graduation of the protractor
while the needle points to N, so that the operator can proceed in any determined
direction.
In order that he may thus be guided at night the bottom of the case is lined
with paper or other material coated with luminous paint. For employing the
instrument as a clinometer as shewn in Fig. 6, the eye c of the protractor is
engaged on a pin 2 projecting from the lid, the ends of the protractor are held
between the finger and thumb, leaving the lid and the case to hang freely while a
sight is taken along the straight edge of the protractor at an object, the depression
or elevation of which is determined by the graduation which coincides with the
sight line b.
The observations taken by the instrument can readily be plotted, using the
protractor and its scales for that purpose.
Having now particularly described and ascertained the nature of this inven-
tion and in what manner the same is to be performed, we declare that what
we claim is:
A military sketching instrument comprising a protractor provided with a
magnetic needle and a hinged case substantially as described.
Dated this 14th day of January 1896.
ABEL & IMRAY,
Agents for the Applicants.