An Improved Surveying Instrument.
Year: 1894

page_text: Date of Application, 10th Mar, 1904
Complete Innria
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ABIL Ch
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Complete Specification Left, 19th Sec., 1994 Accepted, 16th Feb.,
1005
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PROVISIONAL SPECIFICATION.
An Improved Surveying Instrument.
We JOSEPH ANDREW WEBBER and WALTER HENRY JOSEPH WEBBER,
both of 87 Oxford Street, Swansea in the County of Glamorgan Jewellers, and
WEBBER & SON LIMITED, a company registered under the Companies Acts
and having its registered office at 87 Oxford Street, aforesaid do hereby declare
the nature of this invention to be as follows:-
This invention relates to an improved surveying instrument known as Я
circumferentor for use in prospecting work for plotting down the bearings of the
lines to be surveyed.
The object of the invention is to so construct the instrument that all the index
readings can be obtained directly from one standpoint, to avoid the necessity of
applying corrections for instrumental parallax, to provide means of obtaining both
forward and back sights over the same line so as to enable the accuracy of each
observation to be immediately checked from station to station, to approximate the
accuracy of the instrument to that of a theodolite, and to enable angles of altitude
to be measured and altitudes to be approximately ascertained by a simple
calculation.
The instrument comprises a magnetic compass arranged eccentrically to the
vertical axis of the instrument and consisting of a magnetic needle poised on a
centre within a divided ring, the casing of the compass being mounted on a
revolving bed-plate mounted on the vertical axis of the instrument and turning
with the sight-vanes over a stationary divided circle concentric with the axis
of the instrument, upon which circle the horizontal angles, through which the
instrument is revolved are read off (simultaneously with the compass readings)
by the aid of a vernier, through an aperture in the bottom of the compass casing
and within the compass ring, the revolution of the instrument about the axis of this
circle being effected either directly or through a pinion motion.
The optical axis of the sights intersects the vertical axis about which the
instrument rotates, and the sight vane carrier is mounted on a horizontal axis
intersecting the optical axis of the sights and the vertical axis of the instrument,
the said horizontal axis being supported on a standard rising from and removably
attached to the revolving bed-plate. The sight vane carrier is provided with an
arc (divided for versed sines and for altitudes) upon which the altitude angle of
the sights is read in degrees by means of a vernier.
The sights comprise an eye piece formed of a shutter with sight hole in
combination with double crossed wires or double crossed lines on glass enclosing
between them a small square field of view. These sights are duplicated so that
both a forward and a backward sight may be obtained over the same line without
altering the adjustment of the instrument. For this purpose each vane is formed
of a ring across which double cross wires are stretched or in which the glass with
double cross lines is fitted, a shutter with sight-hole being pivoted to each ring so
that it may be moved into or out of position. When in position for use as an
eye piece it covers the vane, its sight hole coinciding with the space enclosed by
the crossed wires or lines of that vane, the shutter of the other or object vane being
then turned aside to uncover the vane and enable an object to be sighted in the field
of the crossed wires or lines.

page_text: A level is provided upon the revolving base plate, and the axis about
which the base plate revolves and on which the divided circle is fixed, is supported
on a tripod.head provided with levelling screws, as usual in similar instruments.
The tripod stand is adapted for use as a walking stick and for this purpose a cover
forming the handle of the stick is adapted to fit over the levelling screws and thei
plates in which they work.
We, JOSEPH ANDREW WEBBER and WALTER HENRY JOSEPH WEBBER,
both of 87, Oxford Street, Swansea, in the County of Glamorgan, Jewellers, and
WEBBER AND SON, LIMITED, a company registered under the Companies Acts
and having its registered office at 87, Oxford Street Swansea aforesaid, 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 :-
This invention relates to an improved surveying instrument known as a
Circumferentor, for use in prospecting work for plotting down the bearings of the
lines to be surveyed.
The object of the invention is to enable all the index readings to be read off,
if not at a glance at least from one standpoint; to avoid the necessity of applying
corrections for instrumental parallax; to provide means of sighting both forwards
and backwards over the same line so us to enable the accuracy of each
observation to be immediately checked from station to station; to approximate the
accuracy of the instrument to that of a theodolite; and to enable angles of
altitude to be measured and altitudes to be approximately ascertained by a simple
calculation.
The instrument is illustrated in the accompanying drawings, forming part of this
Specification, and its construction will be described in detail with reference
thereto.
Figure 1 is a vertical sectional elevation on line 1-1 Figure 2; Figure 2 is a
side elevation; and Figure 3 is a plan of the instrument.
Figure 4 is a side elevation of the sights only, illustrating the mode of using the
instrument.
.
The same letters of reference denote like parts in all the figures.
The instrument comprises a magnetic compass arranged eccentrically to the
vertical axis 6 of the instrument and consisting of a magnetic needle a poised
on a centre a¹ within a divided ring a², the casing of the compass being mounted
on a revolving bed-plate B mounted on the vertical pivot 6 of the instrument and
turning with the sight-vanes C, C', over a stationary divided circle D carried
by a disc concentric with the axis b, upon which circle D the horizontal angles
through which the instrument is revolved are read off (simultaneously with
the compass readings) by the aid of a vernier d through an aperture in the
part of the bed-plate B which forms the bottom of the compass casing and
within the compass ring a², the revolution of the instrument about the axis
being effected either directly or through a pinion motion, as will be readily
understood.

page_text: The optical axis of the sights C, C', intersects the prolongation of the vertical
axis about which the instrument rotates, and the sight-vane carrier E is mounted
on a horizontal pivote whose axis intersects both the optical axis of the sights C,C¹,
and the vertical axis b of the instrument. As the line of sight passes through
both the horizontal and vertical axes, the instrument is free from the error due to
instrumental parallax which occurs in measuring angles in altitude with the ordinary
form of circumferentor wherein the line of sight does not intersect the horizontal
axis of the sight vane carrier. The said horizontal pivot e is supported on a
standard F rising from the revolving bed-plate B to which it is removably affixed
by a nut screwing on a stud f' fixed to plate B in order to render the instrument
more portable. The sight vane carrier E is provided with an arc G (divided at 9 for
versed sines and at g' for altitudes) upon which the altitude augle of the sights is
read in degrees by means of a vernier g', the readings being made from the side at
which the compass is situated.
C
The sights C, C, comprise an eye-piece carried by one vane and formed of a
shutter with sight-hole c' in combination with doubled crossed wires c³, (or it
may be doubled crossed lines on glass) enclosing between them a small square field
of view and carried by the other vane. In order that both a forward and a
backward observation may be obtained along the same line of sight without
instrumental parallax and without altering the adjustment of the instrument,
(ie. without turning the instrument about its vertical axis) the sights are
duplicated, that is to say each sight comprises an eye-piece and a field, each sight-
vane being formed of a ring c³ across which the double crossed wires c² are stretched
(or in which a glass with doubled crossed lines is fitted) a shutter c with sight-
hole c being pivoted to each ring so that it may be moved into or out of position.
When the shutter (say, of the sight C,) is in position for use as an eye-piece it
covers the aperture of the ring, its sight-hole c¹ coinciding with the space enclosed
by the crossed wires or lines of that vane which are then out of use, whilst the
shutter of the other vane C¹ is then turned aside in order to uncover that vane and
enable an object to be sighted in the field of its crossed wires or lines c².
taking an observation in the one direction all that is necessary is to throw back the
sbutter first looked through and put the other shutter in position to sight through
it the field of view of the other vane. Clamping screws, y, are provided for the
horizontal and vertical adjustments both of which may be effected by pinion motions,
a tangent screw being in any case provided if desired for fine adjustment as usual in
such instruments. A level H is mounted upon the revolving base plate B (or two
levels at right angles as usual in such instruments) and the pivot b about which
the base plate revolves and on which the divided circle D is fixed is supported
on a tripod head I provided with levelling screws i, as usual in surveying
instruments.
After
The tripod stand of the smaller instruments is adapted for use as a walking-
stick, and for this purpose a cover forming the handle of the stick is adapted to fit
over the levelling screws and plates which, in this case, are not detached from the
tripod.
Having now particularly described and ascertained the nature of the said inven-
tion, and in what manner the same is to be performed, we declare that what we
claim is :-
1. The improved circumferentor or like surveying instrument constructed for use
substantially as specified.
2. In a circumferentor or like surveying instrument, the combination of a
magnetic compass movable with the sight carrier over a stationary divided circle
about the vertical axis of the instrument, and of sights whose optical axis intersects
both the vertical and the horizontal axes about which the sights are adjusted,
substantially as specified.
3. In a circumferentor or like surveying instrument the combination of a
magnetic compass eccentric to the vertical axis of the instrument and movable

page_text: with the sight carrier about said axis and over a stationary divided circle-
concentric with said axis, and of sights movable about a horizontal axis intersecting
both the vertical axis and the line of sight, substantially as specified.
4. In a circumferentor or like surveying instrument, the combination of sights
formed by an apertured eye-piece on the one vane and a field of view enclosed by
double cross wires or lines carried by the other vane, substantially as specified.
5. In a circumferentor or like surveying instrument, the construction and
combination of the duplicated sights whereby forward and backward observations
may be obtained along the same line of sight without moving the instrument,
each sight comprising crossed wires or lines enclosing a field of view and an
eye-piece formed of a movable shutter having a sight hole adapted to coincide
in position with the space enclosed by the crossed wires for the time being
out of use, the field and eye-piece of one vane being respectively adapted for
use in conjunction with the eye-piece and field of the other vane, substantially as
specified.
Dated this 19th day of December 1894
A. M. & WM. CLARK,
53, Chancery Lane, London, Chartered Patent Agents.