IMPROVEMENTS IN RANGE FINDERS OR APPARATUS FOR MEASURING DISTANCES
Year: 1875

page_text: LETTERS PATENT to John Henry Johnson, of 47, Lincoln's Inn
Fields, in the County of Middlesex, Gentleman, for the Invention
of "IMPROVEMENTS IN RANGE FINDERS OR APPARATUS FOR MEASURING
DISTANCES."-A communication from abroad by General Hiram
Berdan, of Paris, in the Republic of France.
Scaled the 13th July 1875, and dated the 25th May 1875.
PROVISIONAL SPECIFICATION left by the said John Henry Johnson
at the Office of the Commissioners of Patents, with his Petition, on
the 25th 'May 1875.
'
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1
I, JOHN HENRY JOHNSON, of 47, Lincoln's Inn, Fields, in tho
County of Middlesex, Gentleman, do hereby declare the nature of the
said Invention for "IMPROVEMENTS IN RANGE-FINDERS OR APPARATUS FOR
MEASURING DISTANCES," a communication-to-me-from-abroad-by-General
Hiram Berdan, of Paris, in the Republic of France, to be as follows:―
This Invention relates to various improvements in range finders or

page_text: mark the points corresponding to the last differences are sufficiently far
apart to enable them to be plainly distinguished:
B-
In carrying out this Invention the apparatus is composed of two
telescopes mounted upon a frame at a suitable distance apart, one of
which, say for example the right-hand glass is stationary, whereas the
left-hand glass is free to move horizontally on pivots in pivot sockets
attached to the forward end of the same. The 'glasses are connected by
means of a combination of rods or tubes or a parabolical shaft, the
transverse section of which is cruciform, together with rings encircling
the telescopes and connecting arms. The shaft or the main rod of the
combination is supported in journal boxes provided one at each end of
the frame. The left-hand journal box is formed by means of a bearing
which revolves upon a vertical pivot, and in which the centre of the
left journal of the shaft can turn on the rounded point of a pivot attached
vertically to the journal box.

page_text: In order to enable the cross hairs with which the two telescopes aro
provided to be adjusted, so that they perfectly correspond horizontally,
two adjustable screws aro attached to one of the encircling rings of the
right-hand glass, which screws move the said glass vertically.
The method of fastening the said glass at the other end permits a
revolution around the centro pivot of the other oncircling ring in a
vertical direction.
"
Both of the telescopes are provided with a moveablo ocular for short
and long distances, which is operated by means of a rack and pinion.
The glasses so arranged are thus moved simultaneously both horizontally
and vertically, but in addition to the combined motion of the two glasses.
the right hand glass is also capable of moving on the pivots which are
attached to its forward end..
The chief principle of the instrument is to place the perpendicular of
the cross hairs of the fixed glass exactly by the side of a stationary
object, the distance of which is to be measured, after which the vertical
hair of the cross hairs of the other glass is placed exactly upon the same
point. If the glasses were so placed before these operations were com-
menced that the cross hairs of the glasses corresponded perfectly with
each other, and exactly covered the same point which was taken at the
- shortest distance, then the arc described by the left hand glass in.
revolving on its pivots must be measured if the distance of any object is
required to be ascertained.
'
The measurement of the arc. or the differences of the arcs may bo
determined by means of either a differential screw or micrometer screws,
as desired. A spiral spring is employed to press the steel point attached,
to the left hand glass continuously against the centre of a steel plate
secured to a wheel or drum or the point of a micrometer screw.. The.
wheel moves on the micrometer screw which is attached to the arm so
as to be capable of motion in the arm, in order to ensure the exact
adjustment of the wheel or drum at the shortest distance. One revolution
of a screw head or of the wheel or drum on the micrometer screw is
equal to the longest arc, and causes the left hand glass: to move simul-
taneously the same distance.
As already mentioned above the circumference of the screw head or

page_text: pointer is employed to indicate immediately the distance corresponding
with the arc traversed by the instrument.
.
The wheel or drum of the artillery instrument may indicate the
elevation as well as the distance, in order to save the time necessary for
referring to the tables at present in use for artillery. These divisions
may be either determined by measuring the ground at known distances,
or by mathematical calculations.
The instrument may be transported either by hand by two men, the
case having handles like a stretcher, or it may be placed on a cart,
which may be attached to an artillery caisson. The apparatus is
contained in a case, the ends of which may be turned on hinges, and
thus be opened and thrown back when the instrument is to be operated..
The case is also provided at its lower part with legs, jointed, and so
arranged as to enable them to be turned up; by this means the apparatus
may be readily moved from place to place.
When the apparatus is to be used all that is required is to turn down
the legs, which assume an inclined position, by resting against strong
stops fixed thereto, so as to form a firm and invariable foundation for the
instrument. Three fixed legs may also be attached to the case, the
instrument being then suspended under the axle.
The artillery instrument is mounted by preference on four wheels, and,
may be attached to a caisson or drawn by a horse.
an⚫
The ends of the case which are held by the joints are first opened;
the cross hair of the right hand glass is then adjusted to the side of
object which is, say, 300 yards distant, and the cross hair in the other
glass is then adjusted so that it exactly corresponds with the cross hairs
of the right hand glass. When this arrangement is completed the cross
hairs are also made to correspond perfectly horizontally by operating. the
two nuts on the screw pivot of the ring, as before mentioned.. After this
preliminary adjustment the instrument is perfectly ready for use. The
cross hair of the right hand glass is now placed by the side of an object,
and the cross hair in the other glass adjusted so as to exactly correspond.
with the former by turning the wheel or screw head.
At the preliminary adjustment of the instrument the index was placed
at, say, 300 yards as the shortest distance; therefore by turning the

page_text: exactly corresponds with that of the other glass the pointer will show
the distance of the object.
The details of the apparatus may be varied, and it may be applied to
recorders of different arrangements without departing from the principle
of this Invention; as for example, the arc traversed by the movable
glass around its pivots may be measured by means of a circular disc in
which a number of screws corresponding to the number of distances to
be measured are so fixed that the length of each of these screws corres-
ponds with each of the distances to be measured. The ends of these
screws produce a spiral curve, the upper horizontal surface of a
cylindrical revolving case or box in which the said circular disc is
placed being graduated according to the different distances to be
measured.
The arc traversed by the glass may also be measured by means of.
an eccentric disc, which operates against a friction roller attached to the
glass. The eccentricity of this disc should be equal to the distance
traversed by the glass. If the flat side of the disc is provided with
graduations corresponding to the difference of the arcs the distance can
also be measured by turning the eccentric disc and reading direct from
the same; or a wedge operated between a friction roller attached to the
glass and a stationary guide may be employed.
The recorders may also be applied directly to the base of a range
finder, in which the two glasses are fixed to the base in a rigid and
invariable manner, the Invention consisting essentially in a range finder
constructed with two glasses connected by a rigid baso, and with a :
recorder as before mentioned.
SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said John Henry Johnson in the Great Seal Patent
Office on the 25th November 1875.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, JOHN 80
HENRY JOHNSON, of 47, Lincoln's Inn Fields, in the County of
Middlesex, Gentleman, send greeting.

page_text: Lord One thousand eight hundred and seventy-five, in the thirty-eighth
year of Her reign, did, for Herself, Her heirs and successors, give and
grant unto me, the said John Henry Johnson, Her special license that
I, the said John Henry Johnson, my executors, administrators, and
assigns, or such others as I, the said John Henry Johnson, my executors,
administrators, or 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
Ohannel Islands, and Isle of Man, an Invention for "IMPROVEMENTS IN
RANGE FILDERS OB APPARATUS FOR MEASURING DISTANCES," a communication
to me from abroad by General Hiram Berdan, of Paris, in the Republic
of France, upon the condition (amongst others) that I, the said John
Henry Johnson, by an instrument in writing under my hand and
seal, 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 Seal Patent Office within
six calendar months next and immediately after the date of the said
Letters Patent.
NOW KNOW YE, that I, the said John Henry Johnson, do hereby
declare the nature of the said Invention, and in what manner tho
same is to be performed, to be particularly described and ascertained in
and by the following statement, reference being had to the accom-
panying Drawings, and to the letters and figures marked thereon, that is
to say:-
The said Invention relates to various improvements in range finders
or instruments for measuring distances, such improvements having for
their object the production of an apparatus which shall be free from the
defects of those hitherto employed. ->
The essential condition to be fulfilled by a range finder, especially for
infantry and light artillery is to give the distance in a few seconds and
with sufficient accuracy; it is necessary therefore that the distance
should be measured without reference to tables or calculations. This
necessity for rapidity in measuring operations is explained by the
excessive mobility of the troops on the battle field, and also by the rapid
firing arms now employed. Instruments, which are either difficult of
adjustment or which require too long a time for each operation, can be

page_text: operation of measuring with such instruments is not sufficiently rapid
for them to be of any value upon a field of battle.
As herein-before stated, the essential condition to be fulfilled by a
range finder intended for the use of troops on the battle field is rapidity
in the observations. It is further requisite that the distances be
measured with sufficient accuracy corresponding to the graduation on
the sights, and the measurements should be given directly by the
apparatus, and be read with facility. These conditions are fulfilled by
the improved apparatus, which consists essentially of two glasses con-
nected together by a fixed base, one of the glasses being moveable
without changing the base. The movement of the glass is effected by
means of a recorder, which indicates at first sight the distance or the
degree of elevation as soon as the cross hair in the second glass has been
made to correspond with that in the stationary glass.
'
The whole apparatus can be carried on a hand truck.
The mechanical part of the instrument is so arranged as to produco
extremely fine differences or movements, which are made measurable in
a manner which is readily understood.
The measurement is effected by means of a micrometer screw,
which has a thread equal to the difference of the arcs x to x. This
screw is provided with a proportionally large head, or a wheel of corre-
sponding large diameter is screwed on to the micrometer scrow. Each
revolution of this wheel or screw produces a movement equal to x to x.
If the circumference of this wheel or screw head be now divided
into n parts, according to the ratio of the difference of the arcs x-£₁,
,, the problem of measuring
distances and reading the same, direct without the aid of tables or
arithmetical calculations is solved in the simplest and most correct
manner by taking a wheel of such diameter that the lines which mark
the points corresponding to the last difference z to z. are sufficiently
far apart to enable them to be plainly distinguished.
•
•
•
•
I shall now proceed more particularly to describe the construction of
the improved apparatus, and for that purpose shall refer to the several
Figures-on-the-accompanying-two-Sheets of Drawings.
Figure 1, Sheet 1, of the Drawings shows as before. mentioned tho
outline of different rectangular triangles with a fixed base, the heights

page_text: of which represent the distances to be measured, and Figure 2. the
manner in which these distances are measured and indicated by the
improved apparatus.
Figure 3 shews a sectional plan of the range finder.
J
Figure 4, Sheet 2, is a longitudinal vertical section, the extremities of 5
the case being opened and the apparatus ready to be operated.
Figure 5 is a side elevation shewing the case closed and the range
finder ready to be transported from one place to another.
Figures 6, 7, 8, 9, 10, and 11 (Sheet 1) show on an enlarged scale the
principal parts of the apparatus.
1
Figures 12, 13, (Sheet 2) show wooden legs or supports, the object of
which is to provide a firm basis for the apparatus when in use.
The apparatus is composed of two telescopes A and B constructed and
fitted out in the best possible manner, as far as optics are concerned,
one of which, videlicit, the right-hand glass (B) in the example shewn 1
in the Drawings is stationary, whereas the left-hand glass (A) is free to;
move horizontally on the pivots a, a, in the pivot sockets attached
to the forward end of the same.
-The glasses A and B are connected by means of a combination of rods,
or tubes O', 0¹, and a parabolical bar or tube C (the transverse section 20
of which is cruciform), and by means of the rings b, c, d, e, and the
arms fand g. The bar C, which is the main rod of the combination, is
supported in the journal boxes D and E. The journal box D is formed.
by means of a journal support, which revolves round the pivot h, and in
which the centre of the left journal of the bar O can turn on the round 25
point of a pivot attached vertically to the journal box. The box E is an
ordinary covered journal box.
In order to prevent any lateral motion the bar or tubo O is provided
with two flanges.
The journal box E with the bar C, or the combination of rods, is 30
capable of turning around the vertical axis of the pivot of the journal
box D.

page_text: against the upper moveable part of the foot or support H, to the lower
part of which the nut K is secured. By means of this arrangement the
micrometer screw L moves the upper part of the foot or support H with
the journal of the main rod O of the combination on the upper surface
5 of the lower part of the foot H, and for this purpose the upper part of
the foot H is provided with two friction rollers 1, 1, which operate on the
said upper horizontal surface of the lower part of the foot or support H.
This lower part of the foot H is provided with three friction rollers 2, 2,
which work on the surface of the arc or segment I, and can be firmly
O attached to the said arc by means of a pressure screw Z. At the
opposite side of the foot H is a cylinder M, in which a spiral spring R'
is fixed. The pin N of this spring presses against a steel plato arranged
opposite thereto. A pressure screw ○ is screwed into the journal
box E..
5.
To enable the cross hairs of the two telescopes to be adjusted, so that .
they perfectly correspond horizontally, two adjustablo scrows k, k,.
are attached to the ring e of the glass B, which move the said glass.
vertically.
The method of fastening the said glass at the other end permits a
O revolution around the centre pivot of the ring d in a vertical direction.
Having thus described the principal mechanical parts of the range
finder I shall now proceed to explain the method of operating the same,
and placing it in position, as well as the application and utilization of
the mathematical principla.
Both of the telescopes are provided with a moveable ocular for short
and long distances, which is operated by means of a rack and pinion,
and both glasses are fitted with perfectly made and accurately adjusted
cross hairs. The glasses A and B being connected by the bar O or the
combination of rods or tubes C', and the journal support D being capable
) of turning around the pivot h, and the journal box E with the foot H
being guided in the arc of a circle I, of which is the axis, the
glasses A, B, are moved simultaneously both horizontally and vertically.
These simultaneous movements are of the greatest importance; they
ensure a quick and certain result combined with the simplest con-
-struction.

page_text: glass A is also capable of moving on the pivots a', a', which are attached
to the forward end of the glass A.
The chief point to be observed in using the instrument is to place the
perpendicular of the cross hairs of the fixed glass B exactly by the side
of a stationary object the distance of which is to be measured, and when
this operation is completed to place the vertical hair of the cross hairs of
the glass A exactly upon the samo point. If the glasses were so placed
before these operations were commenced that the cross hairs of tho
glasses corresponded perfectly with each other, and exactly covered the
same point which was taken at the shortest distance, then the are
described by the glass A in revolving on the pivots a', a³, must be
measured if the distance of any object is required to be ascertained.
The measurement of the arc or the differences of the aros may bo
effected either by means of a differential screw or by means of micrometer
screws, as shown in the Drawing. The spiral spring R' presses a stcel
point attached to the glass A continuously against the centro of a steel
plate attached to the wheel or drum T or the point of the micrometer
screw S. The wheel T moves on the micrometer screw S, which is
attached to the arm f. This screw S is capable of moving in the arm ƒ to
ensure the exact adjustment of the wheel or drum T at the shortest
distance. One revolution of the screw head V or of the wheel or drum T
_ on the micrometer screw is equal to the differences of the arcs x to x,
and causes the glass A to move simultaneously the same distance.
As already mentioned the circumference of the screw head or tho
wheel T is divided in proportion to the differences of the arcs, and a
pointer U is employed to indicate immediately the distance corresponding
with the arc traversed by the instrument. The divisions are equal to a
distance of 50 meters as the sights for small arms and the elevation for
cannon are divided into 50 meters.
The wheel or drum of the artillery instrument may be so arranged as
to indicate the elevation as well as the distance, in order to save tho
time necessary for referring to the tables at present in use for artillery.
These divisions may be determined either by measuring the ground at
known distances or by mathematical calculations.
The instrument can be transported either by hand by two men, the caso
having handles like a stretcher, or it may be placed on a cart, which may
be attached to an artillery caisson, as represented in the Drawing. The

page_text: screw head until the cross hair of the glass A covers or exactly cor-
responds with that of the glass B, the pointer will show the distance of
the object.
The apparatus shewn in the Drawing has a two meter base; it
measures and records the different distances from 300 to 1,800 metres 5
with an approximation of 25 meters, and up to 3,000 meters with an
approximation of 50 meters.
According to the above it will be seen that the dimensions of the
different instruments will have to be arranged so as to correspond with
the distance that is required to be measured for the different classes of 1
weapons.
The time required to place the instrument in position ready to take
the distance is about 10 seconds, but the instrument is supposed to be in
this condition all the time on the battle field. The actual time required
to measure any distance within the power of the instrument is from 10 1
to 15 seconds.
It will readily be understood that with a fixed base a very much.
shorter base may be used than with detached instruments, for the reason
that the cross hairs being always in the same plane they cut the object
at the same point, which when the object the distance of which is to be 2
determined is of an irregular form or in an inclined position, as generally
occurs in practice, is a most important point to obtain, since the position
of the perpendicular hairs to the side of the object immediately above or
immediately below the horizontal hairs has alone to be observed.
The arrangement of apparatus herein-before described is that which 2
has given the best results in practice. The description of recorder
applied to the apparatus may however be varied, whilst still retaining
the essential features of the instrument, and effecting the object attained
by the arrangement herein-before described.
The following experiments have been made by the communicator of 8
this Invention with several systems of recorders, viz. :—
First. The arc traversed by the glass A around a¹, a³, has been
measured by means of a circular disc, in which a number of screws
corresponding to the number of distances to be measured were so fixed
that the length of cach of these scrows corresponded with each of the 3

page_text: constructed with two telescopes, a fixed base, and a recorder, substan-
tially as and for the purpose herein set forth.
In witness whereof, I, the said John Henry Johnson, havo to this
my Specification set my hand and scal, this Twenty-fifth day of
November, One thousand eight hundred and seventy-five.