IMPROVEMENTS IN APPARATUS FOR RANGE FINDING OR ASCERTAINING THE DISTANCE OF AN OBJECT FROM AN OBSERVER, PARTS PARTS OF WHICH IMPROVEMENTS ARE ALSO APPLICABLE TO OTHER PURPOSES
Year: 1882

page_text: LETTERS PATENT to Charles McGuire Bate, of Woolwich in the County of
Kent for an Invention of "IMPROVEMENTS IN APPARATUS FOR RANGE FINDING
OR ASCERTAINING THE DISTANCE OF AN OBJECT FROM AN OBSERVER, PARTS
PROVISIONAL SPECIFICATION left by the said Charles McGuire Bate at
the Office of the Commissioners of Patents on the 13th October 1882.
CHARLES MCGUIRE BATE, of Woolwich in the County of Kent "IMPROVEMENTS
IN APPARATUS FOR RANGE FINDING OR ASCERTAINING THE DISTANCE OF AN
OBJECT FROM AN OBSERVER, PARTS OF WHICH IMPROVEMENTS ARE ALSO APPLICABLE
TO OTHER PURPOSES"
My invention relates to apparatus in which the distance of a remote object
from an observer is approximately ascertained by triangulation or measuring
the angles between the observer, the remote object, and a third object at right
angles more or less, from two points at different distances from such third
object.
I take a plate or base to which a binocular field glass, or telescope is fixed
rigidly, preferably by a screw so that its position can be readily altered for the
convenience of carriage, and in front of this glass I fix to the same plate a mirror
turning upon a vertical centre so that it can be adjusted in any position, within
sufficient limits from an angle of forty five degrees with the line of sight of the
glass. The lower edge of the mirror does not descend below the centre of the glass,
so that an observer can observe directly through the latter any distant object,
whilst above it he can see simultaneously the reflected image of any object at or
about right angles to the line of sight, and by turning the mirror sufficiently
round its axis vertical lines through the centres of the two objects can be made to
coincide.
Above the plate and rigidly connected to the axis round which the mirror turns
is a horizontal arm one edge of which passes through the axis of the mirror at an

page_text: angle preferably of forty five degrees with the reflecting surface of the latter, and
upon a fixed centre on the plate at a short distance from the axis of the mirror is
pivotted a graduated arm of considerable length a stud or knife edge upon the
lower edge of which, at a distance from its centre equal to the distance between
the axis of the mirror and the pivot of the arm, presses against the edge of the arın
upon the mirror axis.
By moving the graduated arm round its centre therefore the mirror can be
turned so that its reflecting surface forms a less angle than before with the centre
line of vision of the glass, and the two objects observed no longer coincide until
the observer has advanced a sufficient distance toward the third distant object
described, such distance depending upon the extent to which the mirror is moved.
A spring is provided by which the arm upon the axis of the mirror is constantly
pressed against the knife edge upon the graduated bar.
The outer end of the graduated bar is moved to the right or left by means of a
transverse screw which can be gradually turned round to the right or left by a
thumbscrew until the desired position of the mirror has been attained.
Or, the mirror itself may be adjusted by a screw of a similar kind, the knife
edge upon the graduated bar being brought against its arm when its position has
been so adjusted.
Upon the same centre as the graduated bar described I pivot a second
graduated bar, the graduated edges of the two both passing through the pivot, so
that they can be brought into contact or separated to any desired angle, and this
second bar can be clamped upon the plate in any position when adjusted.
Above the two graduated bars and across them at right angles to their graduated
edges when in their normal position, I arrange a transverse bar the ends of which
are fixed in guides or supports which slide upon the edges of the plate, and upon
this bar is fitted and slides an indicator having a projecting tooth of determined
width which, if the graduated edges are separated at an angle, can be inserted
between them and pushed forward with the sliding guides until it is stopped by
the narrowing angle between the bars, such angle being measured and indicated by
the graduation opposite to the point where the indicating tooth is detained, and
the angle between the bars being always twice the angle through which the mirror
is moved.
The apparatus described is used in the following manner.-The observer directs
the glass toward the third object as above described in front of him, which he sees
directly below the lower edge of the mirror. At the same time he sees, in the
mirror above, the reflected image of the object at right angles to him, the distance
of which is to be found, and he adjusts the angle of the mirror until the vertical
lines through the centres of the two objects coincide.
He then brings the edge of the second graduated bar up against the edge of the
first one, and clamps it in its position upon the plate.
He then walks forward a certain determined distance toward the third object,
and he re-adjusts the mirror by lessening the angle which its reflecting surface
makes with the line of vision until the centres of the two objects again coincide.
The indicating tooth is then introduced between the two graduated edges and it is
made to slide forward until its edges are stopped by the angle between the
graduated edges, and the distance of the object to be measured, or a space of which
that distance is a defined multiple, is then read off upon the graduated edge of
the bar.
The indicating tooth can be turned round upon the transverse bar upon which
it slides, so as to be out of the way whilst the bars are being adjusted.
In order to determine definitely the exact centre of the line of vision through
the binocular or other glass, I make a fine vertical scratch or line upon the front
object glass, and in order that this scratch or line may be seen distinctly when the
instrument is being used I fit inside the eyepiece of the instrument a disc or
semi-disc of thin metal or other opaque substance the upper horizontal diameter of

page_text: which cuts the centre of the lens and I make in it a narrow vertical slit or small
aperture. Through this slit or aperture the vertical scratch or line upon the front
object glass can be distinctly and easily seen. This method of arrangement may be
applied to theodolites or other optical instruments of the like kind, as well as to
the novel apparatus of the kind hereinbefore described.
When the observations, made in the way described, have been completed, the
screw holding the glass can be loosened and the latter turned round until parallel
with the base plate, when the whole apparatus can be readily put away in any
convenient compact case.
SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Charles McGuire Bate in the Great Seal Patent Office on the
13th April 1883.
CHARLES MCGUIRE BATE, of Woolwich, in the County of Kent "IMPROVEMENTS
IN APPARATUS FOR RANGE FINDING OR ASCERTAINING THE DISTANCE OF AN
OBJECT FROM AN OBSERVER, PARTS OF WHICH IMPROVEMENTS ARE ALSO APPLICABLE
TO OTHER PURPOSES
"
My invention relates to apparatus in which the distance of a remote object from
an observer is approximately ascertained by triangulation or measuring the angles
between the observer, the remote object, and a third object more or less at right
angles, from two points at different distances from such third object.
It has for its objects novel methods of constructing and arranging the parts of
such apparatus, so that it is very simple, portable, easily used, and accurate in its
indications.
In order to put my invention in operation, I take a plate or base to which a
binocular field glass, or telescope, is fixed rigidly, preferably by a screw so that its
position can be readily altered for the convenience of carriage, and in front of this
glass I fix to the same plate a mirror turning upon a vertical centre so that it can
be adjusted in any position, within sufficient limits from an angle of forty five
degrees with the line of sight of the glass. The lower edge of the mirror does not
descend below the centre of the glass, so that at the same time that an observer
observes directly through the latter any distant object, he can see simultaneously
the reflected image of any object at or about right angles to the line of sight, and
by turning the mirror sufficiently round its axis vertical lines through the centres
of the two objects can be made to coincide.
Above the plate and rigidly connected to the axis round which the mirror turns
is a horizontal arm one edge of which passes through the axis of the mirror at an
angle preferably of forty five degrees with the reflecting surface of the latter, and
upon a fixed centre on the plate at a short distance from the axis of the mirror is

page_text: pivotted a graduated arm of considerable length a stud or knife edge upon the
lower edge of which at a distance from its centre equal to the distance between the
axis of the mirror and the pivot of the arm, presses against the edge of the arm
upon the mirror axis.
By moving the graduated arm round its centre therefore the mirror can be
turned so that its reflecting surface forms a less angle than before with the centre
line of vision of the glass, and the two objects observed no longer coincide until
the observer has advanced a sufficient distance toward the third distant object
described, such distance depending upon the extent to which the mirror is
moved.
A spring is provided by which the arm upon the axis of the mirror is constantly
pressed against the knife edge upon the graduated bar, and the knife edge is itself
preferably made adjustable so that its exact position can be fixed.
The outer end of the graduated bar is moved to the right or left by means of a
transverse screw which can be gradually turned round to the right or left by a
thumbscrew until the desired position of the mirror has been attained.
Or, the mirror itself may be adjusted by a screw of a similar kind, the knife
edge upon the graduated bar being brought against its arm when its position has
been so adjusted.
Upon the same centre as the graduated bar described I pivot a second bar
which may also be graduated, the graduated edges of the two both passing
through the pivot, so that they can be brought into contact or separated to any
desired angle and this second bar can be clamped upon the plate in any position
when adjusted.
Above the two graduated bars and across them at about right angles to their
graduated edges when in their normal position, I arrange a transverse bar the ends
of which are fixed in guides or supports which slide upon the edges of the plate,
and upon this bar is fitted and slides an indicator having a projecting tooth or
gauge of determined width which, if the graduated edges are separated at an
angle, can be inserted between them and pushed forward with the sliding guides
until it is stopped by the narrowing angle between the bars, such angle being
measured and indicated by the graduations opposite to the point where the
indicating tooth is detained, and the angle between the bars being always twice the
angle through which the mirror is moved.
In the accompanying drawing, which is in illustration of my invention applied
to a binocular field glass in the manner described, figure 1 is a perspective view,
figure 2 on a smaller scale, a plan when closed, and figure 3 a plan when in use.
V is the vertical mirror, half the depth of the object glass A, and attached to the
lower side of the plate B by the axis E which bas the arm E, F rigidly attached
to it. One edge of this arm passes, if continued, through the centre of the axis E.
The two bars G, H, and G, I, are pivotted at G on the plate B, one G, H, being a
loose arm, and G, I, having a knife edged projection at K capable of minute longi-
tudinal adjustment so that the distance between G and K can be made exactly
equal to the distance between G and E.
The knife edge K and the centre E of the axis of the mirror are therefore
always on the circumference of a circle of which G is the centre.
The straight
edge of the arm E, F is kept in contact with the edge of the stud K which as the
arm G, I is moved, travels along it, keeping the point of contact on the circumference
of the circle described.
Since the angle subtended by an arc at the centre, is double that at the cir-
cumference (Euclid Book III prop: 20) the angular movement of the arm, is double
that of the mirror arm and as the mirror moves through only half of the observed
angle, the arm moves through an angle equal to that observed.
The plate is attached to the field glasses in such a manner that it can revolve
through the aro of a circle.
When closed for carriage the
glasses (as shewn in figure 2).
mirror is at the side of, and protected by the field
When ready for use the plate is swung round and

page_text: clamped in such a position that the mirror is in front of the object glass (as shewn
in figure 3) and-in its normal position-at 45° to the line of sight forming an
optical square.
The parallel motion N carrying the gauge S is placed (when the mirror is in its
normal position) at right angles to the arm G, I, so that any motion of the mirror
and consequently of the arm is shown by the angle which the gauge makes with
the arm.
Thus the gauge bar N being in a constant position the arm places itself at an
angle to the gauge, equal to the angle which the object seen in the mirror make
with the line of sight. The loose graduated arm G, H, is used when brought up to
the arm G, I, and clamped there, to mark the first position of the arm or first angle
taken while the second angle is being observed.
The gauge is a small piece of hard steel in the form of the letter H sliding freely
on a round bar N, which can be made to slide up and down the plate, guided by its
edges.
The narrow projections of the gauge are equal to one division of the graduated
arms. The broad ones equal two divisions. The whole width of the gauge is equal
to ten divisions. The only adjustment necessary in the instrument is the
movement of the knife edge stud, nearer to, or farther from, the axis G of the arm,
so that its distance shall be made exactly equal to the distance between the axis of
the arm and that of the mirror.
This is done preferably by means of a bowed spring M (free at one end K) fixed
to the side of the arm G, L. This spring is made straighter, or allowed to curve more,
by means of a screw L, which passes through the arm G, I, and is tapped into the
spring M. Thus the free end K can be thrown further from, or brought nearer to,
the axis G as the screw is tightened or loosened.
By this means if the instrument reads longer or shorter than the actual range, it
may be adjusted to read correctly.
The apparatus described is used in the following manner, as illustrated in
figure 4.
The observer directs the glass toward the third object D as above described in
front of him, which he sees directly below the lower edge of the mirror. At the
said time he sees, in the mirror above, the reflected image of the object A, the
distance of which is to be found, and he adjusts the angle of the mirror by means
of the screw P and spring T, until vertical lines through the centres of the two
objects coincide. He then brings the edge of the graduated bar G, H, up against
the edge of G, I and clamps it in its position upon the plate, the angle which it
makes with the centre line of the gauge being equal to A, B, D.
He then walks forward a certain determined distance toward the third object D
and he readjusts the mirror until the centres of the two object A and D, again
coincide, the angle which the bar G, I, makes with the centre line of the gauge
being equal to A, C, D. The indicating tooth or gauge is then introduced between
the two graduated edges and it is made to slide forward until its edges are stopped
by the angle between the graduated edges, and the distance of the object to be
measured, or a space of which that distance is a defined multiple, is then read off
upon the graduated edge of the bar, the angle between the bars being equal to that
subtended by the base B, C at A, or the difference between the first and second
angle measured.
The indicating tooth or gange can be turned round upon the transverse bar on
which it slides, so as to be out of the way whilst the bars are being adjusted.
Instead of one mirror only, two mirrors may be used as in the method ordinarily
adopted in sextants.
In order to determine definitely the exact centre of the line of vision through
the binocular or other glass, I make a fine vertical scratch or line upon the front
object glass, and in order that the scratch or line may be seen distinotly when the
instrument is being used I prefer to fit inside the eye piece of the instrument a disc
or semi-disc of thin metal or other opaque substance, and I make in it a narrow

page_text: This
vertical slit or a small aperture. Through this slit or aperture the vertical
scratch or line upon the front object glass can be distinctly and easily seen.
method of arrangement may be applied to theodolites or other optical instruments
of the like kind, as well as to the novel apparatus of the kind herein beforė
described.
When the observations, made in the way described, have been completed, the
screw holding the glass can be loosened and the latter turned round until parallel
with the base plate as shewn in figure 2, when the whole apparatus can be
readily put away in any convenient compact case. Instead of being fitted to a
binocular field glass as shewn the instrument may be fitted to any suitable
telescope, the necessary modifications in the details of its construction being made.
I do not confine myself to the precise form and arrangement of the several parts
of the apparatus, which may be varied to suit varying circumstances, but having
described my invention and the manner in which it is to be performed, I claim :-
The method of determining the angle through which the mirror is moved
between two successive observations, by means of the two moveable graduated bars
and the adjustable bar upon the axis of the mirror, such angle being equal to the
angle to be measured and being double the angle through which the mirror is
moved, substantially as described and shewn in the Drawing. Also, the method of
measuring the angle between the two graduated bars adjusted as described, by
means of the moveable sliding gauge of definite width, substantially as described
and shewn in the Drawing.
In witness whereof I, the said Charles McGuire Bate have hereunto set my
band and seal this thirteenth day of April in the year of our Lord 1883.
CHARLES MOCUIRE RATE