IMPROVEMENTS IN THE INSTRUMENTS USED FOR MEASURING DISTANCES
Year: 1882

page_text: PROVISIONAL SPECIFICATION left by the said John Philip Nolan at the
Office of the Commissioners of Patents on the 17th March 1882.
JOHN PHILIP NOLAN of Ballinderry, Tuam IMPROVEMENTS IN THE INSTRUMENTS
USED FOR MEASURING DISTANCES
The object of this invention is to construct a novel and peculiar instrument or
instruments for ascertaining distances other than astronomical
The Instrument comprised in these improvements consists of two half instruments
fixed at the ends of a base of known length, or more generally of two half instru-
ments capable of being attached to the ends of a base; this base may be fitted to
receive the attachments of such half instruments or if the base is not so specially
fitted the half instruments will be specially fitted with attachments to enable these
half instruments to be affixed to some particular kind of base.
The improvements also consist of moveable fittings capable of being attached to
a base and made so that a half instrument can be attached at will to such a
fitting.
One half instrument called the "Pointer" is composed of a telescope (best a
refracting erecting) to which is rigidly fixed at right angles to it another telescope
(best inverting) I call the former the "sighting" and the latter the aligning
telescope
By the expression rigidly fixed I do not mean to exclude the power of making
an adjustment but I mean that the angle between the telescopes cannot be used
or altered for the purpose of measuring an angle other than a right angle
The sighting telescope should contain in its focus cross wires or a thin point'or

page_text: thread of metal it is best that these cross wires, web, or other substance should
be provided with a horizontal adjustment to rectify accidents or defects of
workmanship.
'
The aligning telescope must also be provided with cross wires.
The second half instrument I call the "Reader" it consists of a telescope (best)
inverting) which I call a sighting telescope to which is rigidly fixed at right angles
another telescope (best inverting) which I call an aligning telescope and which is
provided with cross wires.
The sighting telescope of the Reader contains a special scale in its focus
In considering the two half instruments together it is to be noted, that the
aligning telescope of either half may make on the object glass side more than a
right angle with its sighting telescope provided the excess is small and is
exactly balanced by an equal defect in the angle similarly made in the other half
instrument.
The base may consist of a rod, a tube, or other bodies; it is specially contem-
plated that for military or sporting purposes it should consist of a rifle; the supply
of means for fitting the instrument to a rifle is part of the improvements.
If the base consists of a rod or tube it is intended that the "Pointer " half
instrument should be provided with a metal tongue or slip, which should slide into
a metal box placed at one end of the base and that the Reader" should be
similarly capable of attachment to the other end of the base.
"
When so fixed the sighting telescopes will be perpendicular or roughly so to the
base and the aligning telescopes parallel to the base.
The object glasses of the sighting telescopes would both face in the same
direction while the object glasses of the aligning telescopes would point towards
each other.
To obtain distances it is absolutely necessary that the cross wires of the sighting
telescope of the "pointer," & the scale of the Reading telescope should be in the
same optical plane also that a line called the Infinity line traced on the scale
should be exactly parallel to the cross wires centre of the pointer or in other words
that the focii of the two sighting telescopes should be parallel and in the same
plane when the half instruments are affixed to the base.
To supply means to effect this constitutes a part of the improvements
The "Pointer" should be capable of moving for purposes of adjustment to the
right or left on the tongue which connects it with the base; also for purposes of
adjustment it should be capable of revolving for about five degrees round the axis
of the sighting telescope; this is easily effected by inclosing the tube of this
telescope in another tube.
The "Reader" half Instrument should also possess these adjustments and in
addition should be attached to its tongue by a spring which being pressed by a
screw would move the axis of its sighting telescope up or down at will.
The two sighting telescopes had better be focussed for a long distance and then
permanently fixed at this focus by screws.
16
The aligning telescopes must be so focussed that if placed opposite to each other
and if a man looks through the aligning telescope of the
"
Pointer he can
distinctly see also the cross wires of the aligning telescope of the "Reader" this
will theoretically take place when both telescopes are focussed for an infinite
distance; it should also be determined by trial.
To give light to the wires of the." Pointer" aligning telescope a prism should be
provided capable of being placed over the aperture of its eyepiece.
The special scale in the sighting telescope of the "Reader" is engraved or
otherwise described on glass and consists of a line called the infinity line and of
other lines drawn at distances from the infinity inversely proportional to certain
selected distances and directly proportional to the length of the base and to the
focal length of the telescope containing the scale
I give the distances on the scale from the infinity line for lines to represent

page_text: In addition to the fittings at either end of the base a third fitting either fixed or
capable of attachment should be provided, to be placed when used, or left, about a
foot from the "Reader" fitting
This third fitting is used solely for testing by supplying a very small base.
To test the Instruments The Reader Half instrument is placed at one end of
the base and the "Pointer " half instrument is attached to the third fitting
Then by the adjustments described the two sighting telescopes are brought into
the same horizontal plane and the cross wires of the aligning telescopes are made to
apparently touch each other so that their centres will apparently coincide
Then the Infinity line is directed to a distant object say ten miles distant, then
the centre of the cross wires in the sighting telescope of the "Pointer " should be
found on the object; if there is a small horizontal error it is now corrected by the
adjustment provided in the "Pointer" sighting telescope.
The "Pointer "Half instrument should now be shifted to the other end of the
base, and if a distance is required the cross wires of the aligning telescopes are
again brought on each other and the two sighting telescopes are again brought into
the same plane
The cross wires of the sighting telescope of the "Pointer " are now brought on
the object and then the object will appear in the scale of the "Reader" touching the
line which represents the true distance or between two lines in true proportion to
the distance.
When a rifle is used as the base a slide box is attached to the stock and the
"Reader" half instrument is fitted to a bayonet socket; a ring to grip the barrel
about a foot from the muzzle-which ring has a slide box-is also provided.
One of the cross wires of the aligning telescopes had better be formed slanting
like an X the other pair of wires being straight as is usual.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said John Philip Nolan in the Great Seal Patent Office on the
18th September 1882.
JOHN PHILIP NOLAN of Ballinderry, Tuam
MENTS USED FOR MEASURING DISTANCES
"
"IMPROVEMENTS IN THE INSTRU-
My said Invention relating to Improvements in measuring Instruments has for
its object to attain the more speedy and convenient measurement of distances
such as is required for Military Civil Engineering Marine and other similar
operations.
The said Improvements consist in an arrangement of fittings on a convenient
base such as a rod tube or framework or other suitable body or support also of two
half instruments of peculiar construction as hereinafter described and of an
additional fitting to assist in supplying a small base for adjusting the instruments
truly which fitting may be attached permanently to the regular base or may be
capable of attachment to it by the same socket slide or other contrivance by which
one of the half instruments is attached to the support or it may be capable of
independent attachment to the base.
And in order that my said Invention may be fully understood I shall now
proceed more particularly to describe the same and for that purpose shall refer to
the several figures on the annexed Sheet of Drawings the same letters of reference
indicating corresponding parts in all the corresponding figures.
Figure 1 of the accompanying Drawings represents (drawn to a small scale) the
aforesaid base formed of a rod or tube and carrying three slide boxes or receivers
in accordance with one part of my Invention. Figure 2 is a detail shewing an
enlarged end view of one of the receivers, Figure 3 is a view of the half instruments
arranged on a small base for testing and correcting purposes. Figures 4 and 5
represent respectively a plan and elevation of the Pointer or sighting instrument,
and figures 6 and 7 represent respectively a plan and elevation of the reading
instrument. Figure 8 is a sectional detail of the gripping apparatus employed in
connection with the sighting telescope. Figure 9 represents (drawn to a greatly
enlarged scale) a special scale for the sighting telescope of the "reader" half
instrument Figures 10 to 13 shew modified constructions of the instruments as
hereinafter described and figures 14 and 15 represent respectively a detail view of
a slide box and Stock fitting adapted for use where a rifle is employed as a base
instead of a special rod or tube. The views of the instruments are drawn
to a larger scale than the other figures, (with the exception of the Scale shewn
at Figure 9).
When the aforesaid base is in the form of a rod or tube it is fitted as shewn in
figure 1, with three slide boxes A, B, C, to receive the tongues or feet N¹, N¹¹.
which form part of the half instruments.
There is nothing peculiar in the actual construction of each slide box and
other contrivances may be substituted to grasp the said half instruments and fix
them to the base.
The novelty consists in the fact that while two of the slide boxes A and C are
far apart that is at either end of the optical base, two, A and B, are close together,
Four such boxes might be used, two far apart and two close together. Also two
fittings only might be used if one were moveable so that it could be made to
approach the other or two such fittings might be made fixtures and a third made

page_text: detachable or an extra small base might be provided with two such fittings. The
three boxes, as first described and shewn are the best plan of furnishing the desired
small base to be used for testing purposes only. The small base may be usefully
an exact and determined fraction (as one twenty fifth) of the larger, this is how-
ever not absolutely necessary. Of the two half instruments one is used for pointing
at the object, the distance of which is to be ascertained or measured and the other
half instrument is used for reading such distance.
The first half instrument above referred to I call "the pointer." It is composed
of a telescope D¹. preferably an erecting "refracting" telescope to which is rigidly
attached at optical right angles thereto another telescope E'. preferably an
inverting instrument. I call the former the sighting and the latter the aligning
telescope although such telescopes as the latter are often called collimating
telescopes.
These two telescopes may be attached together by a piece of Metal QQ (See
figures 4 and 5) in which two cylindrical holes have been bored at right angles to
each other so as to fit the tubing of the telescopes.
The sighting telescope of the pointer should contain in its focus cross wires or a
pointed pin or filament of metal placed horizontally with the point at or about the
centre of the field. Provision should be made to give a fine horizontal movement
of adjustment to such cross wires or filament which may be effected by a pin and
gearing similarly to the mechanism for winding up a watch and protected by the
guard O worked by a detachable key or the adjustment may be effected by two
adjusting screws or in other similar known ways.
The aligning telescope should be inverting and contain something fine and
distinguishable in its focus, for example, slanting or diagonal cross wires like an X
or a thin metal plate covering half the field and placed in the focus with a fine
notch in the centre thereof are effective contrivances.
It is a great advantage to fasten this aligning telescope (as also that of the
"reader") to its sighting telescope close to the object glass of the sighting telescope
so that the axis of the two sighting telescopes can be approached very closely for
testing purposes.
A cover of thin metal K¹ is placed over the front of the aligning telescope as a
guard and Sunshade. It also may carry a weight to counterpoise the eye piece and
of the aligning telescope so that the system balances round the axis of the sighting
telescope.
The sighting telescope is surrounded for a portion of its length by a tube F¹. F¹.
or by two short tubes in which it can be rotated a little for occasional adjustment.
The tube F. F¹. is attached by brazing or otherwise to a block of metal M
which may be of considerable thickness as shewn in figure 5 of the drawings but
such dimensions may be varied according to requirements.
The block is attached so that it can when desired make a horizontal movement
relative to the tongue of metal N'. N. through the intervention of a pivot screw L
and clamping screw T both screws being conveniently countersunk in the said
tongue piece. The necessary play is allowed and effected by a slot left in the
socket of the screw T in the tongue N¹. so that the pointer can be occasionally
moved a little to the right and left on its tongue N¹. according to requirements
and then by tightening the said screw or both the above mentioned screws it can
be retained or fixed in any desired position.
A strip of metal x is firmly attached to F¹. and can be clamped by the screw, y,
to Q, play being allowed for this screw, so that the sighting telescope can be
rotated for about five degrees in F¹. or by tightening, the screw can be firmly
clamped to F¹.
On the eyecup of the aligning telescope E' is placed a right angled prism R
which can at will be brought over the eye piece aperture or pushed out of the
way.
In the former position it will give the sky as a background to the wires of the

page_text: aligning telescope of the pointer when looked at through the aligning telescope of
the reader in the latter position it permits of the aligning telescope being looked
through
The "reader" half instrument (see Figures 6 and 7) is made up of two telescopes
preferably inverting with means for adjustment and of attachment to the base.
The sighting telescope of the reader is contained in a tubular frame work F¹¹ in
which it has a little rotatory play and also a very fine and easy horizontal play or
adjustment. The two adjustments or the double play are obtained by gripping
the sighting telescope in front by the ring I and in rear by the bent spring J by
the little rounded bar V and by the screw H. The spring presses the tube both
on the top and the side (see detail at Figures 8 and 8A Figure 8 being a side view
and Figure 8A an end view with tube in position). The ring plays or works in
gimbals G G. The sighting telescope can be made to rotate by turning it by band
inside the said ring I and between the spring J screw H and rounded bar v. The
stops Z Z are provided to limit or control such motion. The sighting telescope
can be moved finely and freely by the screw H to the right and left this
adjustment being frequently employed.
The tubular framework F1 F1 is attached by screws to the broad rectangularly
bent spring S. This spring can be compressed or relieved by turning the screw U
which acts against a fulcrum formed by a projecting portion of the tongue N"N"
coming up through a slot or hole in the said spring the lower end of the spring
being securely fastened to the said tongue. The screw U practically screws into
a part or connection of N11 which has a screw hole tapped in it so that by turning
the said screw the axis of the telescope D¹¹ is elevated or depressed at pleasure and
consequently can thus be brought at will into the same optical plane with the
axis of D¹.
N is furnished with a side spring to retain it firmly in its slide box The
aligning telescope E" of the reader is furnished with perpendicular and horizontal
cross wires as before explained.
The aligning telescope E" is fastened to the sighting as in the "pointer" but in
the reverse direction. A case K" similar to K' of the pointer with a counterpoise Wi
is also provided K should however be either much larger or smaller than K¹ 80
that in testing one case may fit inside the other and permit of the axes of D¹ and D¹¹
being brought close to each other The sighting telescope D" of the reader has in
its focus a special scale Figure 9 placed horizontally This scale is engraved or
.otherwise inscribed on glass or some other substance usually employed for such
purposes and consists of a line called the infinity line and of other lines drawn at
distances apart inversely proportional to certain selected distances such as One
bundred Two hundred Three hundred yards and directly proportional to the
length of the base and to the focal length of the "Reader" sighting telescope
containing the said scale
By way of example I give the distances on the scale from the infinity line for
lines to represent One hundred yards to One thousand yards for a base of four feet
and a focal length of ten inches

page_text: A modification in the construction and arrangement of these instruments may be
made for the sake of convenience and portability. Optically such modifications
are slightly inferior 'as there is some loss of light and additional complication.
These modified arrangements are illustrated at Figures 10 to 13 of the Drawings.
The modification consists in providing both the aligning telescopes with prisms
P P best placed in front of the object glasses as shewn
When the said prisms P¹ P¹¹ are so placed the tubing of the aligning telescopes
will run along the sighting telescopes D¹ D" to which E' E" are attached by rings
QQ The axis of the sight of the aligning telescopes will still be at right angles
to the sighting telescopes D' D¹¹ as the prisms will bend the rays of light entering
the object glasses of the former (of which the prisms now form an essential part)
and the wires of the pointer aligning telescope can be seen through the Reader
aligning telescope.
In this case the guards K' K" are transferred to the position as shewn no
counterpoise being necessary in this arrangement.
This Invention is especially applicable to the use of a rifle as a base
When this
is the case a slide box C (See figure 14) is attached to the stock X on the right side or
that away from the firer. The true position for the box is found by fitting the
"reader" to the muzzle of the rifle and then placing the "pointer" in the box and
seeing that when the box is in its true position the two instruments or rather the
axes of D¹ and D" are parallel and at the intended distance apart
Other similar fittings instead of a slide box might be used or the pointer might
be affixed by a clamp and so attached at will to the stock but the last mentioned
plan is cumbersome and inconvenient
In the reader half Instrument I make the following modification. Instead of
fastening the spring S to a tongue 1 fasten it to a bayonet socket making the screw
enter into the top or shank of the socket which serves for the fulcrum. The
bayonet socket may be of any kind usually employed but should fit well and
accurately
If the Rifle should not be quite the desired length a shallow false piece of wood
may be added between the wood of the stock and the heel plate
A small slide box B (Figure 15) should be provided for gripping the rifle by
means of a cut or bent ring and screws near the muzzle so as to furnish a small
base for testing purposes. Instead of this arrangement a small slide box may be
fitted for the same purpose to the bayonet socket to which the reader is attached
as shewn in Figure 12 of the Drawings.
It should be ascertained by trial that when the pointer is in the slide box then
the axis of the sighting telescope of the "Pointer" will be approximately parallel
to that of the Reader when the aligning telescopes are directed on each other.
If this is found not to be the case the fit of the slide box should be altered until
a rough parallelism is attained. True parallelism can only be attained by the use
of the "Reader" adjustments
The Reader half instrument may also be fitted to a bayonet or a rod with a
bayonet socket but fitting it near the muzzle is best
I will now briefly describe the manner in which the instruments would be
used.
The instruments should be tested to commence with-The "Reader" is for this
purpose placed in the slide box A. The Pointer" in that of B. A point is
chosen in the distance which ought to be ten miles distant if A is about a foot
from B but if A is so near C that the axes of the sighting telescopes are under two
inches apart two miles will generally be far enough and even one mile if very
accurate testing is not necessary. The instruments are now by means of their
adjustments brought so that looking through the aligning or collimating telescopes
of the Reader the wires of the two aligning telescopes will appear to touch so that
the two crosses will appear to form an eight pointed star It should be noted
that a slight error of vertical adjustment is of little consequence in well made

page_text: .
instruments but the lateral or horizontal adjustment should be accurate. I use the
word horizontal all through this my Specification in only a general sense exact
levelling not being usually required with these instruments.
The sighting telescopes are brought into the same plane by the screw U then
the infinity line of the scale is brought in a point of the distant object by
moving the base with the instruments then the cross wires (or the point of the
pin or filament) or whatever other optical object is in the focus of the sighting
telescope is brought on the same point of the object by means of the lateral
adjustment for the cross wires which is worked by the detachable key from O.
As moving one of the adjustments may derange others it should be carefully noted
that at the end of the operation the wires of the aligning telescopes should appear
to touch truly and also that the infinity line of the "Reader" and the wires of
the "pointer" sighting telescopes should be on the same distant point.
On first testing it is probable that the horizontal adjustment of the "Pointer"
on N and also its rotating adjustment in the tube F¹ will have to be used but
when however the first testing has been effected the screws L T and y are
tightened and the "Reader" adjustments alone are generally sufficient for any
further delicate adjustment. The adjustments of the Pointer are only occasionally
used in cases of accidents or to meet little errors of workmanship.
To take a distance the pointer is removed to C and the wires of the sighting
telescope of the pointer are brought on the distant point by moving the base and
whole system then the scale is brought by the screw U on the point to get the
axes of the sighting telescopes in the same plane and the wires of the aligning
telescopes are brought on cach other. Then the wires of the pointer being still
on the distant point that point will be seen on the scale of the "Reader" touching
a line representing a given distance or between two lines at an apparent distance
from each in true proportion to the real distance of the point from the observer.
If the true distance be Eight hundred and sixty yards then the point will appear
between the Eight hundred and the Nine hundred lines but about One tenth
nearer to the Nine hundred line.
In the above operation the adjustment of the "pointer" is seldom required
except the first time the instrument is employed or after an accident while the
vertical adjustment of the Reader" obtained by rotating it in F is also not
often used.
"
During "testing and distance taking" the base may be rested on almost any
support and the pointing done by hand.
Elaborate stands of various kinds may also if desired be used fitted or not with
rotating gear or with suitable known arrangements for holding the base.
"
In the above descriptions I have supposed the "Pointer" to be on the right of
the base and the "Reader on the left. The instruments may however be
manufactured to fit in the reverse manner.
Mirrors may be employed instead of the prisms described but the latter I find
preferable.
The sighting telescopes may have a double concave glass between the eye piece
and the object glass in which case the focal length of the "Reader" sighting
telescope will in calculating the scale be taken as that of the corresponding simple
or ordinary telescope that is a simple refracting telescope of the same magnifying
power (with the same eye piece) as is possessed by the telescope of which the
magnifying power is increased by the concave glass.
The sighting telescopes should be focussed for a long distance say two miles or
for an infinite distance. The aligning telescopes should be focussed for an infinite
distance. This focussing should be permanently retained by fastening by screws
the drawers to the body of the telescope or otherwise. The aligning or collimating
telescopes should be carefully tried before this fastening, to see that the wires of
the pointer Aligning Telescope can be distinctly seen from that of the Reader

page_text: when the object glasses optically face each other with or without the intervention
of prisms.
Having now described and particularly ascertained the nature of my said
Invention and the manner in which the same is or may be used or 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 hereinbefore in part
recited Letters Patent is:-
First The use for the purposes of testing instruments or apparatus for measuring
distances of the type hereinbefore described of a prepared base smaller than that
used for purposes of observation substantially as and for the purposes hereinbefore
described with reference to the accompanying Drawings.
Second. The use of such prepared smaller base as set forth in the preceding
claim in combination with that portion of the instruments which permits of the
axes of the sighting telescopes being placed closely together also the use therewith
of the infinity line on the special scale substantially as herein before described with
reference to the accompanying drawings.
Third-The use of a special horizontal or approximately horizontal scale in the
focus of one of two telescopes attachable to a fixed base provided with means of
insuring their parallelism relatively to each other by bringing the wires (or
equivalent arrangement) of a telescope to correspond to the wires or equivalent
arrangement in the focus of another telescope substantially as hereinbefore
described with reference to the accompanying Drawings.
Fourth-The use of the infinity line traced for purposes of testing on such scale
as referred to in the preceding third claim in combination with the smaller base
and also the scale in combination with the adjustment for readily placing the axes
of the two sighting telescopes in the same plane during observations substantially
as hereinbefore described with reference to the accompanying Drawings.
Fifth-The use of the spring arrangement or equivalent fine adjustment which
can be used easily and simultaneously with the observation for the purpose of
bringing the axis of one of a pair of parallel telescopes into the same optical plane
with the axis of the other telescope substantially as and for the purposes herein-
before described and illustrated more especially in Figures 7 and 13 of the
accompanying Drawings.
Sixth-The general combination of the adjusting mechanism and clamps
substantially as and for the purpose herein before described with reference to the
accompanying Drawings.
Seventh: The use or employment of the prism or mirror for securing the sky
as a back ground to the wires of the pointer aligning telescope when used in
combination with instruments substantially as hereinbefore described with reference
to the accompanying Drawings.
Eighth The general construction and arrangement of the half instruments
permitting of the axes of the sighting telescopes being placed close together for the
purpose of testing the instrument substantially as herein before described and
illustrated in the accompanying Drawings.
Ninth The combination of an erecting sighting telescope in the Pointer with
an inverting sighting telescope in the "Reader" substantially as hereinbefore
described with reference to the accompanying Drawings.
Tenth-The modified arrangement of the aligning telescopes with the pointer
and Reader instruments substantially as and for the purposes herein-before
described with reference to Figures 10 to 13 of the Drawings.
Eleventh-The application of parallel telescopes of the type hereinbefore
described to rifles such telescopes being capable of being kept parallel by the
collimation of wires or their equivalents substantially as and for the purposes
herein before described with reference to the accompanying Drawings.
Twelfth-The use and combination of the bayonet socket with such instruments
as above set forth for the attachment of one of the half instruments to a rifle

page_text: substantially as hereinbefore described and illustrated in Figures 14 and 15 of the
accompanying Drawings also the stock fitting or attachment for holding the other
half instrument as described and illustrated.
In witness whereof I the said John Philip Nolan have to this my Specifi-
cation set my hand and seal this twelfth day of September One thousand
eight hundred and eighty two.
JOHN PHILIP NOLAN, (LS.)