IMPROVEMENTS IN INSTRUMENTS OF ANGULAR MEASUREMENT, SPECIALLY APPLICABLE TO SURVEYING MINES
Year: 1878

page_text: LETTERS PATENT to John Whitelaw, of Edinburgh, in the County of Mid
Lothian, North Britain, for the invention of "IMPROVEMENTS IN INSTRUMENTS
OF ANGULAR MEASUREMENT, SPECIALLY APPLICABLE TO SURVEYING
MINES"
•
IN
Sealed the 15th October 1878, and dated the 20th April 1878.
PROVISIONAL SPECIFICATION left by the said John Whitelaw at the Office
of the Commissioners of Patents on the 20th April 1878.
JOHN WHITELAW, of Edinburgh, in the County of Mid Lothian, North Britain...
"IMPROVEMENTS IN INSTRUMENTS OF ANGULAR MEASUREMENT, SPECIALLY APPLICABLE.
TO SURVEYING IN MINES."
This Invention which relates to improvements in instruments of angular obser-
vation is more especially designed to be of service in surveying mines, pits, and
similar subterranean works.
It consists,―
First. In fitting the mining theodolite as now used with two arcs, one of which
is rigidly fixed to the compass box in the line of sight, and provided with the
usual graduations, the other being moveable on bearings at right angles thereto, and
free to radiate on its bearings. To the last-mentioned arc is attached the frame,
upon which are carried the sights, which may be of any well-known form, or a
telescope may be used instead or conjointly therewith. The said frame also carries
the vernier from which the angles of elevation and depression are read, the zero of
the vernier being in the central vertical plane of the instrument when the line of
sight is level. Angles of elevation or depression up to 90 degrees are read without
difficulty, and the bearings of the hinged are being as aforesaid in the sides of the
compass box, the compass and the under limb of the theodolite may be of the same
diameter, whereby greater accuracy and a more perfect system of check is obtained,
I Davies C71

page_text: The verniers of the under limb are brought conveniently near to the eye of the
observer.
Secondly. This Invention consists in attaching to the under side of the herein-
before mentioned rigid arc a spirit level by which any displacement of the hori-
zontal adjustment of the instrument in the direction of the line of sight during the
progress of the work is detected and checked.
The Invention further consists in piercing the opposite sides of the rigid arc
with slits, which slits being in the same vertical plane as the sights or telescope,
serve the purpose of ranging horizontal lines.
The improved instrument may be used for taking horizontal angles in the
manner of the miners' compass by using the magnetic needle only, the vernier
otherwise employed for this purpose being clamped. In this position it is in
addition available for taking angles of elevation or depression.
The improvements herein-before described may be applied to the miners'
compass.
Its lightness and compactness combined with the herein-before set forth advan-
tages render the improved instrument specially applicable for surveys below
ground.
SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said John Whitelaw in the Great Seal Patent Office on the 16th October
.1878.
JOHN WHITELAW, of Edinburgh, in the County of Mid Lothian, North Britain.
"IMPROVEMENTS IN INSTRUMENTS OF ANGULAR MEASUREMENT, ESPECIALLY APPLIC
ABLE TO SURVEYING IN MINES."
My said Invention relates to improvements in instruments of angular observa-
tion, and is more especially designed to be of service in surveying mines, pits, and
similar subterranean works.
It consists,
First. In fitting the mining compass or theodolite as now used with two arcs, one of
which is rigidly fixed to the compass box in the line of sight or direction of observa-
tion, instead of on the side of the compass box or to one side of the line of sight, and
moveable. The said rigid arc is provided with the usual graduations for taking
angles and reductions from hypotenusal to horizontal distances. The other of the
two arcs is free to turn on bearings at the side of the compass box and in a line
at right angles to the line of sight. To the upper part of this moveable arc is
attached the frame, upon which are carried the sights, which sights may be of any
well-known form; or a telescope may be used in place thereof or conjointly there-
with. The said frame also carries a vernier, from which the angles of elevation
and depression, and the reductions from the graduations on the fixed are are read,
the zero of the vernier being in the central vertical plane of the instrument when
the line of sight is level.

page_text: The Invention consists, secondly, in attaching a spirit level to the under side of
the herein-before mentioned rigid arc, by which level any displacement of the
horizontal adjustment of the instrument in the direction of the line of sight during
the progress of the work is detected and checked.
The Invention further consists in piercing the opposite sides of the rigid arc with
slits, which slits, being in the same vertical plane as the sights or telescope, serve
the purpose of ranging horizontal lines.
And in order that my said Invention may be properly understood, I now proceed
more particularly to set forth the system, mode, or manner in or under which the
same is or may be used or practically carried into effect, reference being had to the
accompanying Drawings, and to the letters and figures marked thereon, that is to
Bay :-
Figure 1 is a side elevation of a five-inch theodolite for surface or underground
surveys to which my improvements are applied; Figure 2 is a plan of the same;
and Figure 3 is a section of the compass box and lower limb, the other parts being
removed.
Figure 4 is an end elevation, but in the arrangement here represented the vernier
works inside the compass box. Without an internal vernier and the clamp D this
Figure would represent an ordinary dial with my improvements applied thereto.
The compass box is marked A and the graduated lower limb B. To the side of
the compass box is rigidly fixed the graduated arc R in the line of sight. The
are R¹ is free to turn on bearings r at the side of the compass box in a line at
right angles to the line of sight. Attached to the said arc R¹ and sliding upon the
upper part of the arc R is the frame F, which carries the sights S and holders C for the
telescope T. The frame F also carries a vernier V (see Figure 1) for reading angles
and reductions from the graduations on the fixed arc, the zero (v) of the vernier
being in the central perpendicular plane of the instrument. The screws at f are
for fixing the frame F in any position to which it may be brought upon the fixed
arc. Inside the frame F is fixed a spring, which bears on the top of the rigid are
with sufficient force to retain the frame F with the sights and telescope in the
positions to which it may be brought in use, the screw f being only used for
security; when changing the stations the studs 81, 81, (see Figure 4) are for the
purpose of preventing the frame descending below ninety degrees.
A spirit level L is attached to the under side of the rigid arc R for detecting dis-
placement of the horizontal adjustment of the instrument in the line of sight. When
fixed at zero of the rigid vertical are, it can be used as an ordinary level. Slits
are pierced in the opposite sides of the rigid arc R in the same vertical plane as the
sights and telescope, and serve for ranging horizontal lines. One of these slits is
seen at 8, in Figure 4, the other slit being in a corresponding position at the opposite
side of the arc R.
With my improved instrument angles of elevation or depression up to ninety
degrees are read without difficulty, thereby making it suitable for the connected
working of surface and underground surveys. The bearings of the hinged arc R¹
being as aforesaid in the sides of the compass box A, the compass and the under
limb B of the theodolite may be of the same diameter, whereby greater accuracy
and a more perfect system of check is obtained; and the verniers V₁ of the under
limb are brought into the position shewn by the dotted lines in Figure 2, and con-
veniently near to the eye of the observer, by preference at an angle of twenty to
thirty degrees to the right of the line of sight.
The improved instrument may be used for taking horizontal angles in the manner
of the miners' compass by using the magnetic needle only, the lower limb B other-
wise employed for this purpose being clamped. In this position it is also available
for taking angles of olevation or depression and the reduction to the horizontal.
The improvements herein-before described may readily be applied to the existing
miners' compass.
The lightness and compactness of the improved instrument, combined with the

page_text: herein-before set forth advantages, render it specially suitable for undergronnd
surveys.
Having now described and particularly ascertained the nature of my said In-
vention, and the system, mode, or manner in or under which the same is or may be
used or practically carried into effect, I would observe in conclusion that what I
consider to be novel and original, and therefore claim as the Invention secured to
me by the herein-before in part recited Letters Patent is,-
First. The general arrangement and construction of parts constituting the herein-
before described instrument for angular measurement.
Second. Providing the compass box of instruments of angular measurement with
a rigid graduated arc fixed to the sides of the said box so as to cross over the centre
of its face in the direction of the line of sight, and with a moveable arc turning
upon bearings in the sides of the compass box in a line at right angles to the line of
sight, the said moveable arc carrying at its top, above the said rigid arc, a frame
provided with sights, or a telescope, or both, all essentially as herein-before described,
and illustrated in the accompanying Daawings, whereby the said instruments are
rendered capable of working to an angle of ninety degrees.
Third. The combination with the rigid arc referred to in the preceding claiming
clause, of a level, as herein-before described, and illustrated in the accompanying
Drawings.
Fourth. Forming slits in the sides of the aforesaid rigid arc, in the direction of
the line of sight for the purpose of ranging horizontal lines.
In witness whereof, I, the said John Whitelaw, have heréunto set my hand
and seal, this Seventh day of October, in the year of our Lord One thousand
eight hundred and seventy-eight.
JOHN WHITELAW. (L.S.)