An Improvement in and relating to Divided Circles for taking Bearings and such like purposes.
Year: 1896

page_text: An Improvement in and relating to Divided Circles for taking
Bearings and such like purposes.
I, The Hon. GILBERT LEGH, of 8 Cadogan Square, London, S.W. Major Grenadier
Guards, do hereby declare the nature of this invention to be as follows:-
My invention relates to a method of dividing circles such as those for azimuth
compasses, theodolites or other instruments for taking sights or bearings in such a
manner that the subdivision can be readily seen without being magnified and can be
rendered visible in the dark.
For this purpose I divide an outer circle into a number of main divisions, say 36,
each being for 10°. I similarly divide a circle of smaller radius but so that its
divisions are exactly intermediate to those of the outer circle. Then dividing each
of the oblique lines which can be drawn connecting a division of the outer circle to
the next division of the inner circle into 5 equal parts I make holes at the points of
division each of which indicates 1º.
I provide the sight taking instrument which revolves about the centre of the
divided circles with a radius arm part of which exactly corresponds in length and
position with the radial distance between the outer and inner circles, and having
divided this part into 5 equal divisions I make holes at its extremities and its
divisions.
Now by turning this radial arm until one of its holes coincides with one of the
holes in the oblique lines of the circles, I can at once read to a degree the setting of
the arm. Thus, for instance if the arm were a little past the division of the outer
circle marked 30°, and in such a position that its hole 4 divisions from its outer end
coincided with a hole in the circle, then I should know that the arm was set at an
angle of 340
By placing under the divided circle paper or other material coated with luminous
paint, so that its light passes through the holes, the instrument to which my
invention is applied can be used in the dark.
Although I have described, by way of illustration, an outer circle having a division
for every 100, and the oblique line between each outer and inner division divided into
5, so as to mark each degree, obviously the nature of the divisions may be varied as
desired; thus for instance if the outer circle had divisions each for 20°, then the
interval between the holes of the oblique lines would correspond to 2°.
Dated this 4th day of September 1896.
ABEL & IMRAY,
Agents for the Applicant.

page_text: An Improvement in and relating to Divided Circles for taking
Bearings and such like purposes.
I, The Hon. GILBERT LEGH, of 8 Cadogan Square, London, S.W. Major Grenadier
Guards, 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:-
My invention relates to a method of dividing circles such as those for azimuth
compasses, theodolites or other instruments for taking sights or bearings in such a
manner that the subdivision can he readily seen without being magnified and can be
rendered visible in the dark.
For this purpose, I divide an outer circle into a number of main divisions, say 36,
each being for 10°. I similarly divide a circle of smaller radius but so that its
divisions are exactly intermediate to those of the outer circle.
Then dividing each of the oblique lines which can be drawn connecting a division
of the outer circle to the next division of the inner circle into 5 equal parts I make
holes at the points of division each of which indicates 1°.
I provide the sight taking instrument which revolves about the centre of the
divided circles with a radius arm part of which exactly corresponds in length and
position with the radial distance between the outer and inner circles, and having
divided this part into 5 equal divisions I make holes at its extremities and its
divisions.
Now by turning this radial arm until one of its holes coincides with one of the
holes in the oblique lines of the circles, I can at once read to a degree the setting of
the arm.
Thus, for instance if the arm were a little past the division of the outer
circle marked 30°, and in such a position that its hole 4 divisions from its outer end
coincided with a hole in the circle, then I should know that the arm was set at an
angle of 34°.
By placing under the divided circle paper or other material coated with luminous
paint, so that its light passes through the holes, the instrument to which my invention
is applied can be used in the dark.
Although I have described, by way of illustration, an outer circle having a division
for every 10°, and the oblique line between each outer and inner division divided into
5 so as to mark each degree, obviously the nature of the divisions may be varied as
desired; thus for instance if the outer circle had divisions each for 20°, then the
interval between the holes of the oblique lines would correspond to 2°.
The accompanying drawings shew by way of example the application of my
invention to a compass adapted for taking bearings, Fig. 1 is a plan with the lid open,
Fig. 2 shews part of the divided circle to an enlarged scale.
The compass and divided circle of star form are accommodated within a case A to
which is hinged on one side a glass cover, which can be opened, as indicated by the
dotted lines B, for the purpose of setting the divided circle. A lid C, also hinged to
the case A, can be opened as shewn for the purpose of taking sights. The compass
case and the divided circle D can be turned by means of a milled edge on the compass
case turning with it the pointer E. F is a fixed alidade to the edge of which any
point of the divided circle can be turned.
Instead of giving this alidade a straight radial edge as shewn, it may have an edge
notched with notches corresponding with the division holes of the divided circle; or
it might have holes in radial line corresponding with the holes of the circle.
For the purpose of taking bearings back-sights a and al are provided and the lid
C has a slit c with a central wire for a fore sight.
The compass needle can be rendered stationary in the usual way by moving an

page_text: external knob G. The bottom of the case A is preferably painted with luminous
paint or covered with paper or other material so painted, so that the division holes of
the divided circle can be seen at night. Also the sides of the slit c are preferably
made luminous.
Having now particularly described and ascertained the nature of this invention and
in what manner the same is to be performed, I declare that what I claim is :-
The herein described method of dividing a circle for taking bearings or such like
purposes.