A NEW OR IMPROVED MEANS OF AND APPARATUS FOR MEASURING OR ASCERTAINING DISTANCES TO INACCESSIBLE AND OTHER OBJECTS
Year: 1874

page_text: LETTERS PATENT to Francis Weldon, of Mominabad, Deccan, in India,
Captain of the First Cavalry, Hyderabad Contingent, for the In-
vention of "A NEW OR IMPROVED MEANS OF AND APPARATUS FOR
MEASURING OR ASCERTAINING DISTANCES TO INACCESSIBLE AND OTHER
OBJECTS."
Scaled the 18th September 1874, and dated the 25th March 1874.
PROVISIONAL SPECIFICATION left by the said Francis Weldon at the
Office of the Commissioners of Patents, with his Petition, on the
25th March 1874.
I, FRANCIS WELDON, of Mominabad, Deccan, in India, Captain of
5, the First Cavalry, Hyderabad Contingent, do hereby declare the nature
of the said Invention for "A NEW OR IMPROVED MEANS OF AND APPARATUS
FOR MEASURING OR ASCERTAINING DISTANCES TO INACCESSIBLE AND OTHER
OBJECTS," to be as follows:-.
L
The instrument consists of a bar, to which is hinged an arm or limb
0 of such length that when closed on the bar their two ends will come

page_text: together. To the end of the limb furthest from its joint is hinged an
index rod of suitable breadth and thickness, and of such a length as to
reach from the end of the limb when fully extended to the end of the
bar on which the limb closes. To that end of the bar is hinged one end
of a guiding rod, its other cnd being hinged to the index rod. The
guiding rod itself being of such length and hinged to the index rod in
such a place as to allow the limb to be opened or extended to the full
required distance, and also to be closed together with the index rod
along the length of the bar, thus forming them apparently into one.
On extending the limb the index rod will travel along the bar forwards
or backwards as the limb is extended or closed. The upper surface of
the bar over which the index rod travels is graduated as a scale and has
distances marked on it. The bar is furnished with a forc and a back
sight; the limb is also furnished with two sights, forc and back, or with
a telescope.
The instrument is used as follows:-Place the bar on a tripod and a
support or other convenient rest, and from it measure the length of baso
for which the instrument may have been graduated. At that distance
set up a staff to mark the exact spot at which an angle of ninety degrees
is subtended by the instrument and the object whose distance is to be
ascertained. This can be done with an optical square, reflecting
telescope, or other suitable instrument. On this staff direct the fore
and back sights of the bar, then without altering the direction of the
bar align the fore and back sights of the limb on the distant object";
and the distance indicated by the index rod on the graduated scale of
the bar will be the distance of the object from the staff.
The instrument is graduated as follows:-A level piece of ground
having been selected, on it is marked a range line of say three thousand
yards. Along the whole length of this line, commencing from its base,
intervals of say.fifty yards are accurately measured and marked. The
length of base line being now decided on, the instrument is set up at
that distance, say fifty or sixty yards, exactly at right angles to the
range line, and the back and fore sights of the bar are carefully aligned
on the staff which marks the base of the range line and the exact spot
subtended at an angle of ninety degrees by the instrument and all the
'intervals marked on the range line; then without altering the direction
of the bar the back and fore sights of the limb are aligned accurately

page_text: SPECIFICATION n pursuance of the conditions of the Letters Patent,
filed by the said Francis Weldon in the Great Seal Patent Office on
the 24th September 1874.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, FRANCIS
WELDON, of Mominabad, Deccan, in India, Captain of the First
Cavalry, Hyderabad Contingent, send greeting.
.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Twenty-fifth day of March, in the year
of our Lord One thousand eight hundred and seventy-four, in the thirty-
seventh year of Her reign, did, for Herself, Her heirs and successors,
give and grant unto me, the said Francis Weldon, Her special licence
that I, the said Francis Weldon, my executors, administrators, and
assigns, or such others as I, the said Francis Weldon, my executors,
administrators, and assigns, should at any time agree with and no others,
from time to time and at all times thereafter during the term therein
expressed, should and lawfully might make, use, exercise, and vend,
within the United Kingdom of Great Britain and Ireland, the Channel
Islands, and Isle of Man, an Invention for "A NEW OR IMPROVED MEANS
OF AND APPARATUS FOR MEASURING OR ASCERTAINING DISTANCES TO INACCESSIBLE

page_text: AND OTHER OBJECTS," upon the condition (amongst others) that I, the
said Francis Weldon, my exccutors or administrators, by an instru-
ment in writing under my, or their, cr one of their hands and scals,
should particularly describe and ascertain the nature of the said
Invention, and in what manner the same was to be performed, and
cause the same to be filed in the Great Scal Patent Office within six
calendar months next and immediately after the date of the said Letters
Invention, and in what manner the same was to be performed, and
cause the same to be filed in the Great Scal Patent Office within six
calendar months next and immediately after the date of the said Letters
Patent.
NOW KNOW YE, that I, the said Francis Weldon, do hereby declare
the nature of my said Invention, and in what manner the same is to be
performed, to be particularly described and ascertained in and by the
following statement:-
My Invention proceeds on the principle of first dividing into cqual
parts a straight line (which for convenience of reference I will call a
range line), and then selecting a point at right angles to that line and
at such a distance as to enable the observer to see distinctly each of the
divisions on the range line from beginning to end. All the divisions
being thus distinctly visible, the next operation is to make a scale, the
divisions of which shall correspond with the divisions of the range line;
this is done by setting up at the point of observation and at right angles
to the range line a bar having a pointer or limb hinged to it; this limb
when aligned on each of the divisions of the range line in succession
will exhibit a distinct movement, but as the movements of the limb
when brought to bear on the distant divisions must be very slight on
account of perspective, it is necessary to have some means of registering
this slight movement on an increased scale large enough for distinct
subdivision. This is effected by the arrangement of indicator and guide
rod in my instrument hereafter fully described.
The distance from the range line to the point from whence the
furthest division is clearly visible constitutes the base of my method,
which base will vary in proportion to the length of range for which it is
required; thus for a range of 1500 yards base of 50 yards would be
sufficient, while 4000 yards would require a base of 100 yards. This
length of base may seem very great as compared with that of other
methods, but it is not more than under ordinary circumstances of field
· service would be available, even the longest that would be required (100

page_text: yards) is not more than the frontage of a field battery in its normal
formation, and as the longer base is calculated to give more accurate
results advantaren nught to be taken of the available
yards) is not more than the frontage of a field battery in its normal
formation, and as the longer base is calculated to give more accurate
results, advantage ought to be taken of the space available.
3rd. Simplicity and non-Пlability to derangement.
As regards the first, accuracy.-The distances marked on the bar
having been carefully ascertained by actual measurement the instrument
has only to be placed under the same conditions, with reference to the
distant object as it was to the object from which the measurement was
previously obtained to give the same result, and those conditions are
that the instrument be set up at right angles to a staff and the distant
object at a certain predetermined distance from that staff.
Secondly. The time required to find the distance is the time a man
would take to run to the end of a line of from 50 to 100 yards long, and
with an optical square determine a right angle with the instrument and
the distant object, marking the spot with a staff; and while doing so the
sights of the bar can be brought to bear on the staff and the limb on the
distant. object, so that the determination of the right angle and tho
distance would be almost simultaneous.
Thirdly. The simplicity of the instrument, no part being liable to
derangement, whilst it possesses delicate accuracy combined with
strength, when closed it could be secured to the trail or any other
convenient part of a gun or limber instead of occupying the space
allotted to several rounds of ammunition, as the Nolan range finder
docs.
For infantry a rifle might be fitted with a light limb indicator and
guide rod to close along the barrel without adding very much to its
weight.

page_text: :
Presents only mentioned the bar as the place where the graduated scale
should be engraved, yet it might be engraved on the indicator..
My range finder is specially adapted for surveying, as the observer has
only to take the bearings and distances of any object within range of
his instrument to make a far more accurate plan than he could with the
prismatic compass alone, and that too without having to move beyond
the space required for his base.
It must also be borne in mind that my method is not restricted to the
measurement of 4000 yards or so, but may with the aid of telescopes
and a prolongation of base be extended to miles, according to the power
of the telescopes.
:-
My instrument above mentioned I will now more particularly
describe It, consists of a bar, to which is hinged an arm or limb of
such length that when closed on the bar their two ends will..come
together. To the end of the limb furthest from its joint is hinged an
index rod of suitable breadth and thickness, and of such a length as to
reach from the end of the limb when fully extended to the end of the
bar on which the limb closes. To that end of the bar is hinged one end
of a guiding rod, its other end being hinged to the index rod; the
guiding rod itself being of such length and hinged to the index rod in
such a place as to allow the limb to be opened or extended to the full
required distance, and also to be closed together with the index rod
along the length of the bar, thus forming them apparently into one.
On extending the limb the index rod travels along the bar forwards or
backwards as the limb is extended or closed. The upper surface of the
bar over which the index rod travels is graduated as a scale and has
distances marked on it. The bar is furnished with a fore and back sight;
the limb is also furnished with two sights, fore and back, or with a
telescope.
The instrument is used as follows:-Place the bar on a tripod and a
support or other convenient rest, and from it measure the length of base
for which the instrument may have been graduated. At that distance
set up a staff to mark the exact spot at which an angle of 90 degrees is
subtended by the instrument and the object whose distance is to be
ascertained; this can be done with an optical square, reflecting

page_text: telescope, or other suitable instrument. On this staff direct the fore and
back sights of the bar, then without altering the direction of the bar
align the fore and back sights of the limb on the distant object; and
the distance indicated by the index rod on the graduated scale of the
bar will be the distance of the object from the staff..
:
The instrument is graduated as follows:-A level piece of ground
having been selected, on it is marked a range line of say three thousand
yards. Along the whole length of this line, commencing from its base,
intervals of say 50 yards are accurately measured and marked. The
length of base line being now decided upon, the instrument is set up at
that distance, say 50 or 60 yards, exactly at right angles to the range
line, and the back and fore sights of the bar are carefully aligned on
the staff which marks the base of the range line and the exact spot sub-
tended at an angle of 90 degrees by the instrument and all the intervals
marked on the range line; then without altering the direction of the
bar the back and fore sights of the limb are aligned accurately on each
of the 50 yard interval marks in succession, and the spaces indicated by
the index rod are marked off and numbered on the upper surface of the
bar. These spaces can be subdivided and numbered afterwards. The
insturment is now ready for use.

page_text: Figure 2 is an elevation of the other side of the instrument showing
the limb hinged on to and closed upon the instrument.
Figure 3 is a plan of the instrument showing the limb extended and 5
the positions occupied by the indicator and guide rod when the limb is
so far extended, and also the scale of distances on the upper surface of
the bar.
Figure 4 is also a plan of the instrument showing the positions
occupied by the indicator and guide rod when the limb is partially 1
extended.
Figure 5 is a view in perspective of the instrument mounted on tripod
and support.
3
The same letters of reference refer to the same parts in all the
Figures.
The forc
A, B, is an extension of the bar to place on the support M, Fig. 5, or
to hold in the hand when the two sights Band H are aligned on the staff.
B and K are clasps working on pivots passed through the bar and used
to confine the limb C, D, E, when closed along the bar, together with
the indicator and guide rod, as shown in Figs. 1 and 2. The clasp B 2
when raised, as in Fig. 5, forms the back sight of the bar.
sight of the bar H, Fig. 5, can by a simple contrivance be raised or
depressed as the limb is extended or closed. The fore sight of the limb
at E may consist of a very finely pointed peice of wire pointing down-
wards, which when the limb is closed can be passed into a niche cut in 2
the bar to receive it and so protect it from injury when not in use. The
back sight of the limb is placed on the bar at N close to the joint of the
limb at C, so that when the limb is closed the back sight also is protected
from injury.
When the instrument is placed on the tripod and support, as shown 3
in Fig. 5, and the fore and back sights of the bar aligned on the staff,
as before explained, the observer looking through the back sight N,
Fig. 5, and moving the indicator or index rod D, F, I, Fig. 5, back-

page_text: wards or forwards with his right hand can align the fore sight E of the
limb C, D, E, Fig. 5, with great accuracy on the distant object.
Having now particularly described and ascertained the nature and
object of the said Invention, and in what manner the same is to bo
performed or carried out in practice, I hereby declare that I claim the
Invention for "A New. or Improved Means. of and Apparatus for
Measuring or Ascertaining Distances to Inaccessible and other Objects,"
as herein-before described and illustrated by the accompanying Drawings.
In being understood that I do not claim nor limit myself to the details of
construction shown by the Drawings, and herein described with reference
thereto.
In witness whereof, I, the said Francis Weldon, have hereunto set
Witness,
G. B. FARRINGTON,
1st. Cavalry, H. C.,
Mominabad,
Deccan,
India.
F. WELDON. (L.S.)
Capt. 1st. Cav., Hyd. Cont.