Improvements in Instruments for Measuring Angles.
Year: 1892

page_text: Date of Application, 20th Aug., 1892
[Complete Specification Left. 20th May, 1893-Accepted. 29th July. 1893
PROVISIONAL SPECIFICATION.
Improvements in Instruments for Measuring Angles.
I, CHARLES ARTHUR ALBERT BARNES, at present residing at 1, Grove Hill,
Lordship Lane, in the County of Surrey, Assistant Colonial Surveyor of the Gold
Coast Colony, West Africa, and Associate Member of the Institution of Civil
Engineers, do hereby declare the nature of this invention to be as follows:-
This invention relates to instruments for measuring angles; its objects being,
first, to provide a light and portable instrument specially adapted for work abroad
or for military purposes, secondly, to so construct the instrument that it can be
readily taken apart to enable a portion of the same to be detached and used
for plotting angles on paper, and, thirdly, to render fewer divisions necessary on the
scales of the instrument, thus effecting economy.
An instrument constructed according to my invention comprises a protractor
furnished with a boss which screws into an annular projection on a perforated plate
connected to the ball-joint of the tripod. This plate can be turned in a horizontal
plane, and can be clamped in any desired position. The vernier-quadrant is secured
to the protractor by means of a flanged ferrule, which is passed through a central
hole in the boss of the protractor and screwed into the boss of the vernier-quadrant ;
the latter being attached to its boss by means of radial. arms. The vernier-
quadrant is fitted with a suitable clamp. A worm-sector is formed on or attached
to the boss of the vernier-quadrant; a worm on a spindle turning in bearings on
the protractor and also furnished with a thumb-piece_engaging, with the sector.
Between the bearings, a spirit-level may be arranged. The telescope is mounted in
a holder consisting of a piece of metal having a projection on its under side which
screws into the upper end of a short tube provided with a central flange. The
lower end of the tube is passed into the ferrule of the vernier; a plug with a
milled head which bears against the ferrule being screwed into this end of the tube in
order to hold the telescope securely in position. The telescope is an inverting one
provided in the usual way with crossed hairs; one hair being horizontal and the
other vertical. The tube into which the telescope is screwed is provided with a
feather which fits in a feather-way in the ferrule, or equivalent means are employed
for ensuring that the telescope shall always be in the right position, namely, with
its axis over the ninetieth degree when the vernier is at zero. On the top of the
holder there is a casing containing a mirror placed in the vertical plane which
passes through the axis of the whole instrument and lies at an angle of 45° to the
vertical plane in which the axis of the telescope lies. Thus, if the eye-piece of the
telescope face the south, the mirror faces the south east. The casing, contains a
perforation for admitting light to the mirror; a cover being provided for closing
the perforation when necessary. A second mirror in a plane lying at an angle
of 45° to a vertical plane at right angles to the axis of the telescope is placed at
that end of the perforated casing which is nearer the eye-piece. An object-glass
is put between the two mirrors. A third mirror is fitted inside the telescope below
the second. This mirror may be fixed or it may be hinged. and provided with
a handle so that it can be raised until it is parallel with the second mirror.
ordinary magnetic compass is placed on the top of the casing; the axis of the
compass coinciding with that of the whole instrument. The north and south poles
lie over the axis. of the telescope; the south being toward the eye-piece.
A. coloured glass shade may be attached to the eye-piece end of the telescope for
use in taking altitudes; this shade being hinged so that it can be turned in or out
of the line of sight as required. The pedestal of the ball-joint is screwed'on to a
An

page_text: projection of the ordinary kind on the top of the tripod. The upper end of the
pedestal is concave, and contains a convex cap; the interior of the latter being
concave. A hole is drilled longitudinally through the pedestal, and a larger hole is
made in the bottom of the cap. The ball is formed on the head of a pin, which
passes loosely through the hole in the cap, but fits in the longitudinal hole in
the pedestal. A screw-thread is cut on the lower end of the pin; this screw-
thread engaging with a corresponding thread in the end of an arm, which projects
through a slot in the pedestal. The head of the pin is covered by a plate fastened
by screws to the pedestal-cap; this plate also serving to hold the perforated plate
carrying the annular projection into which the protractor is screwed. The first
ninety degrees of the protractor are fully divided; the remainder being marked
with the main divisions only. Or, the first one hundred and eighty degrees may
be fully divided, and the remainder marked with the main divisions only.
The arm on the joint-pin having been moved so as to free the joint, the instrument
is levelled. The arm is then pushed back so as to draw down the pin and lock the
joint. The vernier being clamped at zero, the telescope is then directed toward
one of the points it is desired to determine, and the whole instrument is then locked
by clamping the perforated plate. The vernier-clamp is thereupon released, and
the vernier-thumb-piece turned as to direct the telescope toward the other point;
the angle between the two points from the instrument being then read by means of the
vernier. The latter moves with the telescope. If the angle exceed ninety
degrees, the image of the second point is reflected from the first mirror through the
object-glass to the second mirror, and thence to the third mirror, on which it is
intersected by the vertical hair of the telescope. In reading an angle with the
mirrors, ninety degrees are added to the number of degrees denoted by the vernier.
When it is required to plot angles on paper, the protractor is unscrewed from
the annular projection on the perforated plate pertaining to the joint. The thumb-
plug is then unscrewed out of the end of the tube which supports the telescope;
thus permitting the protractor and the telescope to be separated. A plug or
centre-piece made of metal or transparent material and marked with a centre line
is then placed in the hole which was originally occupied by the tube above
referred to. Any desired angle can then be marked off with the aid of the vernier,
which can still be worked by the thumb-piece attached to the protractor. Angles
of less than ninety degrees can be marked off with the greatest accuracy by means
of the vernier. Angles of more than ninety degrees can be marked off with the
aid of the quadrant and the vernier; it being merely necessary to set the vernier
to shew the difference between the angle and ninety degrees. To facilitate
marking off the angles, the quadrant may have two bevelled radial projections
ninety degrees apart; these projections corresponding with the zero and the ninety
mark on the protractor.
It will be obvious that the vernier and the protractor may be divided and
subdivided according to any suitable scale; the subdivisions being, however,
rendered unnecessary on part of the protractor.
Dated the 20th day of August 1892.
COMPLETE SPECIFICATION.
Improvements in Instruments for Measuring Angles.
1, CHARLES ARTHUR ALBERT BARNES, of Accra, West Africa, Assistant
Colonial Surveyor of the Gold Coast Colony, and Associate Member of the
Institution of Civil Engineers, do hereby declare the nature of this invention and 5
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 instruments for measuring angles; its objects being,

page_text: first, to provide a light and portable instrument specially adapted for work abroad
or for military purposes, secondly, to so construct the instrument that it can be
readily taken apart to enable a portion of the same to be detached and used for
plotting angles on paper, and, thirdly, to render fewer divisions necessary on the
scales of the instrument, thus effecting economy.
An instrument constructed according to my invention is represented in the
accompanying drawings, whereof
Fig. 1 is a side elevation.
Fig. 2 is a view partly in end elevation and partly in section on the line *, *
(Fig. 1).
"
Fig. 3 is a vertical section corresponding with Fig. 1; some of the parts being,
however, omitted.
Fig. 4 is a plan, drawn to a larger scale, of the protractor and vernier detached.
Fig. 5 is a separate view of part of the vernier.
Fig. 6 is a diagram representing, in side elevation, the mirrors for enabling a
point to be seen in a plane at right angles to the axis of the telescope.
Fig. 7 is a corresponding plan.
The protractor A is furnished with a boss A' which screws into an annular
projection C on a perforated plate C connected, preferably by a treble screw
adjustment, to the ball-joint (hereinafter described) of the tripod. The boss may
be made separately, as shown; or the boss and the protractor may be in one piece.
The plate C can be turned in a horizontal plane, aud can be clamped by the
screw in any desired position. The vernier-quadrant D is secured to the
protractor by means of a flanged ferrule E, which passed through a central hole
in the boss A' of the protractor and screwed into the vernier-quadrant-boss D'.
The vernier-quadrant is attached to its boss by radial arms d, and is fitted with a
suitable clamp D³. A worm-sector D³ is formed on or attached to the boss D¹ of
the vernier-quadrant; this sector being acted upon by a worm F on a spindle F',
which turns in bearings F and F (Fig. 4) and is furnished with a thumb-piece F¹.
Between the bearings, a spirit-level F may be arranged. The telescope G is
mounted in a holder H consisting of a piece of metal having a projection / on its
under side, which projection screws into the upper end of a short tube .J
provided with a central flange j. The lower end of the tube J is passed
into the ferrule E; a plug K with a milled head K' which bears against
the ferrule being screwed into this end of the tube in order to hold the.
telescope securely in position. The telescope is an inverting one provided in
the usual way with crossed hairs; one hair being horizontal and the other
vertical. The tube J is provided with a feather which fits in a feather-
way E' in the ferrule E, or equivalent means are employed for ensuring that the
telescope shall always be in the right position, namely, with its axis over the
ninetieth degree when the vernier D is at zero. On the top of the holder there is
a casing M containing a mirror N placed in the vertical plane which passes through
the axis of the whole instrument and lies at an angle of 45° (see Figs. 6 and 7) to
the vertical plane in which the axis of the telescope lies. Thus, if the eye-piece. G¹
of the telescope G face the south, the mirror N faces the south-east. The casing
also contains a perforation or aperture M¹ (visible in Fig. 3) for admitting light to
the mirror; a cover (not illustrated in the drawings) being provided for closing
the perforation or aperture when necessary. A second mirror N¹ in a plane
lying at an angle of 45° to a vertical plane at right angles to the axis of
the telescope is placed at that end of the perforated casing M which is nearer the
eye-piece G. An object-glass (represented in dotted lines in Fig. 1) is put
between the two mirrors N and N¹. A third mirror N' is fitted inside the
telescope G below the mirror N¹. The three mirrors N, N¹ and N are shown
in dotted lines in Fig. 1. The mirror N' may be fixed or it may be hingel
and provided with a handle so that it can be adjusted until it is parallel
with the mirror N'. An ordinary magnetic compass Y is placed on the top
of the casing M; the axis of the compass coinciding with that of the whole

page_text: instrument. The north and south poles 'lie over the axis of the telescope; the south
being toward the eye-piece 'G!. The pedestal 0 of the ball-joint is screwed on to
a projection of the ordinary kind on the top of the tripod. The upper end of 'the
pedestal is concave, and contains an inverted cap Q; the interior of the latter forming
a bearing for the ball R. A hole is drilled longitudinally through the pedestal O,
and a larger hole is made in the bottom of the cap Q. The ball 'R'forms 'the head
of a pin R', which passes loosely through the hole in the cap Q, but fits in the
longitudinal hole in the pedestal O. A screw-thread is cut on the lower end of the
pin R¹; this screw-thread engaging with a corresponding thread in the end S of an
arm or lever, which projects through a slot T in the pedestal. A perforated plate U
is screwed on to the cap Q. This plate is furnished with three adjusting screws V,
V₁ and V. These screws take into lugs on the plate U, and have ball-heads
.engaging in recesses in a plate C. The head of each screw is held in place by a
hinged clip, such as W, or equivalent device. A rocking pin X, which has a
rounded head X¹ engaging with the plate U, is screwed into the plate C. This
hend is also hollowed out to receive the top of the ball R. The head of the
pin X is covered by a plate C³ fastened by screws to the plate C2; this, plate C³
also serving to hold in place the perforated plate C carrying the annular pro-
jection C. The first ninety degrees of the protractor are fully divided, and the
remainder may be marked with the main divisions only. Or, the first one hundred
and eighty degrees may be fully divided, and the remainder marked with the main
divisions only.
The arm S on the joint-pin R' having been moved so as to free the joint, the
instrument is roughly levelled. The arm S is then pushed back so as to draw down
the pin R' and lock the joint. The levelling of the instrument is thereupon com-
pleted by turning one or more of the screws V, V₁ and V. The vernier D being
clamped at zero, the telescope G is then directed toward one of the points it is
desired to determine, whereupon the whole instrument is locked by clamping the
perforated plate C by means of the clamp C¹.
released and the vernier-thumb-piece F* turned so as to direct the telescope G
The vernier-clamp D' is now
toward the other point; the angle between the two points from the instrument being
then read by means of the vernier D. The latter moves with the telescope. If
the angle exceed ninety degrees, the image of the second point is reflected from the
first mirror N through the object-glass to the second mirror N₁, and thence to the
third mirror N2, on which.it is intersected by the vertical hair of the telescope. 'In
reading an angle with the mirrors N, N¹ and N³, ninety degrees are added to the
number of degrees denoted by the vernier D.
When it is required to plot angles on paper, the protractor A is unscrewed from
the annular projection Cx. The thumb-plug K K is then unscrewed out of the
end of the tube J; thus permitting the protractor A and the telescope G to be
separated. A plug or centre-piece made of metal or transparent material and
marked with a centre line is thereupon placed in the hole which was originally
occupied by the tube above referred to. Any desired angle can then be marked
off with the aid of the vernier D, which can still be worked by the thumb-piece F4.
Angles of less than ninety degrees can be marked off with the greatest accuracy
by means of the vernier. Angles of more than ninety degrees can be marked off
with the aid of the quadrant and the vernier; it being merely necessary to set the
vernier to show the difference between the angle and ninety degrees. To facilitate
marking off the angles, the quadrant may have two bevelled radial projections D³
and D ninety degrees apart; these projections corresponding with the zero and the
ninety mark on the protractor A.
It will be obvious that the vernier D and the protractor A may be divided
and subdivided according to any suitable scale; subdivisions being, however,
rendered unnecessary on part of the protractor.
The protractor 'A may be furnished with a removable handle so that it can be
held in the hand and used for taking altitudes. Part of a handle is shown in
dotted lines in Fig. 3. Or, for taking altitudes, a block may be interposed between

page_text: the tripod and the pedestal; the block being screwed on to the projection on the
tripod and having a corresponding projection at right angles to the projection on
the tripod, on which corresponding projection the pedestal is screwed.
Having now particularly described and ascertained the nature of this invention
and in what manner the same is to be performed, I claim :-
-
1. The improved instrument for measuring angles, constructed substantially as
described and illustrated in the accompanying drawings.
2. The improved portable surveying instrument adapted for work abroad or for
military purposes and constructed so that a portion of the same can be detached
and used for plotting angles on paper, substantially as described with reference to
the accompanying drawings.
3. The improved instrument for measuring angles, constructed substantially as
described, and comprising a protractor A, a vernier D, a telescope G, and a series
of mirrors N, N' and N.
4. The improved ball-joint for surveying instruments, the same comprising a
pedestal O, a ball R, a pin R¹ projecting from the ball, an arm or lever S, and a
cap U to which the instrument is connected, substantially as described.
Dated the 18th day of May 1893.
CHARLES A. A. BARNES,
Per J. W. S.