Improvements in Telemeters.
Year: 1890

page_text: Date of Application, 14th Aug., 1890
Complete Specification Left, 14th May, 1891-Accepted, 27th June, 1891
PROVISIONAL SPECIFICATION.
Improvements in Telemeters.
We, ARCHIBALD BARR, Professor of Engineering, in the University of Glasgow,
and WILLIAM STROUD, Professor of Physics, Yorkshire College, Leeds do hereby
declare the nature of this invention to be as follows:--
Our invention applies to that class of range finders in which the range is found
by two observers provided with two angular instruments at the ends of a known
base (or by one observer observing successively from the two ends of the base);
one of the instruments has attached to it in a direction perpendicular to the base
a graduated scale from the indications of which the range can be read directly or
calculated.
In one method of applying our invention two observers at a known distance apart,
say 25 yards (determined by a rod, string, or other mechanical connection, or
indicated by optical means) are each provided with an instrument for setting out a
constant angle of 90° or thereabouts which may be constructed according to any
of the known methods applicable to optical squares and may be provided with
telescopes.
The chief observer carries in addition a well defined mark attached to his
instrument; the assistant observer by shifting his position perpendicularly to the
base uses his instrument to align this mark with the distant object as is usual with
this class of range finder. Attached to the assistant observer's instrument in a
direction perpendicular or nearly so to the base and parallel or nearly so to the
line of vision to the distant object, is a graduated scale which the chief observer
sees, (in place of the usual mark) superposed upon the object whose range is
required, so that the object forms an index to mark the reading on the scale.
Instead of the assistant observer's instrument being formed as an optical square
for aligning a mark on the chief observer's instrument with the distant object it
may consist of a telescope provided with cross wires and a single reflecting mirror
or prism, or reflectors may be dispensed with altogether and the telescope be
attached to the base so as always to remain at the same angle to it. Any arrange-
ment of sight such as are used in surveying compasses and like instruments may be
substituted for telescopes with cross wires.
A modified method of carrying out our invention is the following the chief
observer's mark, instead of being attached to his instrument, as is customary, is
supported upon a staff fixed in the ground or upon a rifle or other support; the
assistant observer adjusts his position so that the image of this mark appears in
alignment with the distant object. The chief observer carries attached to his
instrument a graduated scale capable of longitudinal motion with reference to the
fixed mark in the direction of the line of sight to the distant object. By moving
his instrument backwards or forwards a mark attached to the assistant observer's
instrument can be brought into alignment with the distant object when a reading of
the position of the scale with reference to an index fixed relatively to the mark
will give the distance required. To facilitate the reading of the scale an inclined
reflector may be used.
It will be obvious that though convenient it will not be essential that the chief
observer's mark should be fixed to the ground. He may hold his instrument with
the attached scale in his hand and move his mark together with the index along
the scale.
Dated this 13th day of Avoust 1890
BOTTOMLEY & LIDDLE,
154, St. Vincent Street, Glasgow, Applicant's Agents.'

page_text: COMPLETE SPECIFICATION.
Improvements in Telemeters.
We, ARCHIBALD BARR, Professor of Engineering in the University of Glasgow,
and WILLIAM STROUD, Professor of Physics, Yorkshire College, Leeds, 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 :-
Our invention applies to that class of range finders in which the range is found
by two observers provided with two angular instruments at the ends of a base of
known length, (or by one observer observing successively from the two ends of the
base); one of the instruments has attached to it in a direction perpendicular to the
base a graduated scale from the indications of which the range can be read directly
or calculated.
In one method of applying our invention two observers at a known distance apart,
say 25 yards, (determined by a rod, string, or other mechanical connection, or
indicated by optical means) are each provided with an instrument for setting out
a constant angle of 90° or thereabouts which may be constructed according to any
of the known methods applicable to optical squares, and may be provided with
telescopes.
The chief observer carries in addition a well-defined mark attached to his
instrument; the assistant observer by shifting his position perpendicularly to the
base, uses his instrument to align this mark with the distant object as is usual with
this class of range finder. Attached to the assistant observer's instrument in a
direction perpendicular or nearly so to the base and parallel or nearly so to the
line of vision to the distant object, is a graduated scale which the chief observer
sees (in place of the usual mark) superposed upon the object whose range is
required, so that the object forms an index to mark the reading on the scale.
Instead of the assistant observer's instrument being formed as an optical squire
for aligning a mark on the chief observer's instrument with the distant object, it
may consist of a telescope provided with cross wires and a single reflecting mirror
or prism, or reflectors may be dispensed with altogether and the telescope be attached
to the base so as always to remain at the same angle to it. Any arrangement of
sights such as are used in surveying compasses and like instruments may be
substituted for the telescope with cross wires.
This method of carrying out our invention is illustrated diagrammatically at
Figure 1, where A and Bare the two instruments, each constructed to set out a constant
angle. The chief observer's instrument A carries a mark as above described, while
the assistant observer's instrument B has a scale of reciprocals Q' (shown also in
Figure 2) attached to it in a direction perpendicular or nearly so to the base, and
parallel or nearly so to the line of vision. The length of this scale between the
graduation corresponding to 500 yards and infinity bears the same ratio to the
distance between the scale and the chief observer's instrument as the distance
between the two instruments does to 500 yards. This scale and the mark are so
placed relatively to the assistant observer's instrument and the chief observer's
instrument respectively that when the assistant observer has aligned the chief
observer's mark upon the distant object the scale is seen by the chief observer
reflected so as to appear superimposed upon the distant object which then appears
at the graduation of the scale corresponding to its distance. Figure 2 represents
the scale as seen by the chief observer reflected upon the distant object O. In the
example shown the distance indicated is 750 yards.
Another method of carrying out our invention is illustrated in Figures 3 and 4.
Each observer carries an instrument for setting out a constant angle. The chief
observer's mark, instead of being attached to his instrument, is supported upon
à staff fixed into the ground, or upon a rifle or other support a, Figures 3 and 4.

page_text: The assistant observer adjusts his position so that the image of this mark appears
in alignment with the distant object O, Figure 3. The chief observer carries,
attached to his instrument, a graduated scale capable of motion in the
direction A O (with reference to the fixed mark c.) By moving his instrument
(which is adjusted to set out a constant angle B A O) backwards and forwards
the mark attached to the assistant observer's instrument can be brought into
alignment with the distant object O. A reading of the scale 7 with reference to
an index r fixed relatively to the mark will give the distance of the object O.
This scale is a reciprocal scale, calculated in a similar way to that just described
with reference to Figure 2. To facilitate the reading of the scale an inclined
reflector may be used so that the observer may read the scale without moving his
position.
It will be obvious that though convenient, it is not essential that the chief
observer's mark should be fixed; he may for instance hold his instrument with
the attached scale in one hand and the mark together with the index in the other,
and move the one relatively to the other.
Having now particularly described and ascertained the nature of our said inven-
tion and in what manner the same is to be performed, we declare that what we
claim is :-
1. A range finder or telemeter consisting of two optical squares or other
instruments for setting out constant angles, one of the instruments carrying a scale
of distances which is seen by the observer using the other instrument superimposed
on the distant object, substantially as described with reference to Figures 1 and 2.
2. A range finder or telemeter consisting of two optical squares or other
instruments for setting out constant angles, one of the instruments carrying a scale
moveable relatively to a mark and index, substantially as described with reference
to Figures 3 and 4.
Dated this 12th day of May 1891.
BOTTOMLEY & LIDDLE,
154, St. Vincent Street, Glasgow, Applicants' Agents.