An Improved Surveying Instrument applicable for Measuring Distances and for other Purposes.
Year: 1893

page_text: Date of Application, 30th Mar., 1893
Complete Specification Left, 21st Apr., 1893-Accepted, 4th Nov., 1893
PROVISIONAL SPECIFICATION.
An Improved Surveying Instrument applicable for Measuring
Distances and for other Purposes.
I EDUARDO FALLETTI, of 24 Via Massimo d'Azeglio, Rome in the Kingdom of
Italy, Captain of Artillery do hereby declare the nature of this invention to be as
follows:
This invention relates to a pocket instrument denominated a telegoniometer for
rapidly measuring distances by the trigonometrical solution of any given triangle.
Referring to Figure 1 of the accompanying drawings forming part of this
Specification suppose it is desired to ascertain the distance d of a point P from a
point P by measuring the base b which is in line with a natural signal S and by
taking observations with the telegoniometer at the two stations P P. Since the
sides of any triangle are proportional to the sines of the opposite angles
the telegoniometer and at the second station P the second factor
obtained.
sin (y¹ - y¹¹)
In order that the arithmetical operation to be performed may be very rapid and
simple the reading on the instrument at the first station gives in hundredths the
complement to unity of the sine of the angle y'; let c be the number given by the
instrument.
In order to obtain the first factor sought 6 sin y¹ it is only necessary to
|multiply c by b, divide by 100, and subtract the quotient from the base b.
In the accompanying drawings
Figure 1 above referred to represents the triangle to be solved on the ground
whilst the other figures illustrate the instrument which is contained in a cylindrical
box having one cover fixed and the other revolvable about the axis of the instrument
by means of a small handle.
Figure 2 is a plan view of the instrument looking towards the fixed cover.
Figure 3 is a plan of the mechanism supposing the fixed cover removed and the
cylindrical case in section.
Fig. 4 is a cross section on line xx Figure 3 looking in the direction of the
arrow y.
Figure 5 is a similar view some of the parts being removed.
Figure 6 is a plan of the revolving cover side of the instrument.
Figure 7 is a view similar to Figure 3 some parts having been removed to show
others beneath.

page_text: Figure 8 is a detail section of the counter drawn to double the scale of the other
figures.
The same letters of reference indicate the same parts in all the figures.
A is the fixed cover or bottom of the case, B the revolving cover or disc turned
by a hinged handle C which folds down when the instrument is not in use. D is
the cylindrical part of the box provided with two sight apertures which are closed
as in Figure 3 when the instrument is not in use by a sliding shutter E which turns
on the centre of the bottom A and at same time serves to close the aperture F
therein, the segment of this sliding shutter which closes said aperture being
indicated in Figure 2 by dotted lines." At the centre of the rotating cover B is
fixed the spindle G which carries a worm H and pinion I which gears with a
wheel L in one with pinion M which gears with wheel N. The wheel N is cupped
and contains a spiral spring O (Figure 8) attached at one end to the frame A' and
at the other to wheel N, the purpose of said spring being to hold the teeth of the
gearing in contact even when worn. The face of wheel N is flush with the fixed
cover on which are the divisions corresponding to the reading at the first station P¹
before referred to.
As shown in Figure 8 at the centre of wheel N there is a counter disc Q held by
a spring R in engagement with the nut T, the counter disc Q being separated from
wheel N by a cup U fitting on a polygonal part of the spindle V which is round
where the wheel N and disc Q turn upon it. The worm H gears with the toothed
sector W to which the mirror X is attached, another mirror Y being pivoted to
the frame A on which all the parts are mounted. The exact position in which the
mirror Y is fixed is determined by a spring B₁ and adjusting screw C¹, whilst the
spring D' shown in dotted lines in Figure 5 serves to ensure contact of the teeth of
sector W with the threads of the worm H.
In front of mirror Y is placed a tube K guided by a pivot E¹ received in a
slot F', to carry a sighting device, either a diopter or telescope whose optical axis
should pass by the summit of the mirror Y. Another tube K' is placed within the
instrument and serves as a box for the telescope or diopter according as the one or
the other is used in the tube K. For this purpose the bottom cover A is provided
with an aperture which corresponds with the tube K' and is closed by a hinged
lid G¹.
At the top of the box a diaphragm H' is screwed to the frame A¹ a circum-
ferential groove being left in which is fitted to turn a ring J which is retained in 3
position by a spring wire J. On the diaphragm is fixed the pivot of the stop
wheel L' which has 14 teeth and a convex segment and with which gears the single
tooth pinion M' on the spindle G whereby the latter is prevented from making
more than fifteen revolutions. The mirror Y is fixed and the mirror X is movable,
the latter partaking in the motion of the toothed sector W about its pivot W¹.
These two mirrors make to one another an angle which may be made to vary to
the extent of 45°, from 22° 30' to 67° 30' by the rotation of the worm H which
gears with the toothed sector W. It follows that the angle made by the objects
sighted when the image of the one seen by direct vision coincides with that of the
other viewed by double reflection from the mirrors, may vary to the extent of 90°, +
from 45° to 135°, since the angle made by the mirrors is half that made by the two
lines of sight. The pointer; of the indicator N stands at zero of the graduated
scale when the angle of the lines of sight is 90°. The train of gear wheels I L M N
are so proportioned that the worm H makes 15 revolutions to one revolution of
wheel N.
1
5
The cover or rotating disc B is provided at the circumference with a graduation
corresponding to
for the first revolution of the disc; for the six and a
'sin (y-y")
half revolutions following the graduation is transferred to six and a half spiral turns
marked upon the disc." The index m has a vernier at each side." On the
circumference of ring J there are 200 divisions and one or more points of reference n¸ 5

page_text: which may be marked with letters or other signs. Upon the cylindrical part of the
case is engraved a line which corresponds with the pointer m when the pointer; of
the indicator N is at the zero of the graduation.
The mode of using the instrument for determining the distance (d) (Figure 1) is
as follows-The operator being at the station P' takes the instrument between the
thumb and fore-finger of the left hand so as to be able to turn the handle C with
the right hand. The pointer of the indicator N being at zero, the sliding
shutter E is moved so as to unclose the sight apertures in the circumference of the
casing D and the sight aperture F in the bottom A in order that the visual rays
may enter the instrument. The point P is sighted directly through the diopter or
telescope and the disc B is rotated in the direction of motion of the hands of a
watch until the signal S is also sighted in the same direction by the double reflection
of the mirrors X and Y. The number (c) at which the pointer; of the indicator N
now stands, is then read off on the graduated circle. The operator in passing from
the station P to the station P2 measures the base (6) which is selected of such
length as to contain a whole number of tens of units of length. By dividing (b) by
100 and subtracting the product of the quotient multiplied by the number (c) from
the base (6), the first factor sought, viz.-b sin y' is obtained. At the station Pl
the operator first places the stud 9 of the counter dise q opposite the index j, then
by turning the ring J a point of reference n is brought opposite the index m.
the instrument thus adjusted, the station P is sighted and the disc B rotated in the
opposite direction to the motion of the hands of a watch until the signal S is again
sighted by double reflection of the mirrors X and Y. This done, the number (c')
on the graduation of disc B which coincides with the point of reference n is read off
and this number is the second factor
1
With
which only requires to be multi-
sin (y'—y¹¹)
plied by the result of the previous operations, to obtain the distance (d). The
number () should be read upon the margin of the disc B if at the station P" but
one revolution of the handle has been made or upon the 1st, 2nd, 3rd, or following
convolutions of the spiral according as 1, 2, 3, or more revolutions have been made,
the number of said revolutions being denoted by the motion of the pointer j with
regard to the stud 7 of the counter Q.
It will be understood that by the arrangement and graduation of the principal
parts of the instrument that the number (c¹) obtained as above described has
reference to the difference between the angles comprised between 17-6 about, and
45°, but these differences are not necessarily comprised between these limits. The
factor (c) may in fact be obtained for differences of angles less than 176 by
dividing the number 1000 by the number of divisions of the ring J that the pointer
m is shifted from the point of reference n, since it will be remembered that the
smallest angles are proportional to their sines. In the present case, each division
corresponds to 36 of which the sine is about 0.001. The factor (c¹) may be
obtained for angular differences greater than 45° by arranging the instrument so as
to give such angles of collimation and reading off the number a denoted by the
pointer j, for c¹ =
6°
100
=
a
100
100-a
100
The instrument has been described as applied to the determination of the distance
of one point from another which is inaccessible this being usually the case and being
the purpose for which the instrument would be most generally used. But by a
careful examination of the way in which the instrument is arranged and graduated
it will be understood that it is capable of giving any angles and all the corresponding
trigonometric lines, so as to fulfil various military requirements for laying down or
surveying angles on the ground, for measuring distances and generally for the
solution of any geometrical tonographical problem. Finally, it will be understood
100
The instrument has been described as applied to the determination of the distance
of one point from another which is inaccessible this being usually the case and being
the purpose for which the instrument would be most generally used. But by a
careful examination of the way in which the instrument is arranged and graduated
it will be understood that it is capable of giving any angles and all the corresponding
trigonometric lines, so as to fulfil various military requirements for laying down or
surveying angles on the ground, for measuring distances and generally for the
solution of any geometrical topographical problem Finally, it will be understood
that by the simultaneous employment of two such instruments at two stations, the

page_text: distance of a moving body may be ascertained, which is very important for coast
defence, forts, and for war-ships.
Dated this 30th day of March 1893.
E. FALLEIII,
By A. M. & Wm. Clark,
53, Chancery Lane, London, Chartered Patent Agents.
COMPLETE SPECIFICATION.
An Improved Surveying Instrument applicable for Measuring
Distances and for other Purposes.
I, EDUARDO FALLETTI of 24, Via Massimo d'Azeglio, Rome, in the Kingdom
of Italy, Captain of Artillery, 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 :-
This invention relates to a pocket instrument or telegoniometer for measuring
distances by the trigonometrical solution of a triangle.
Referring to Figure 1 of the drawings accompanying my Provisional Specifica-
tion, suppose it is desired to ascertain the distance d of a point I from a point P
by observations with the telegoniometer, at the two stations P1 P at the
extremities of the measured base which is in alignment with a distant object or
signal S.
Since the sides of any triangle are proportional to the sines of the opposite
By means of the telegoniometer, the first factor 6 sin y₁ of this expression is
obtained at the first station P' and the second factor
is obtained at
the second station P".
sin (y' — y")
In order that the arithmetical operation to be performed, may be very rapid and
simple the reading on the instrument at the first station gives in hundredths the
complement to unity of the sine of the angle y'; let (c) be the number given by
the instrument.
ነሰስ (1
In order to obtain the first factor sought b sin y¹, it is only necessary to
multiply (c) by (b) divide by 100 and subtract the quotient from the base (b).
In the drawings,
Figure 1 above referred to represents the triangle to be solved whilst the other
figures illustrate the instrument which is contained in a cylindrical box having
one cover fixed and the other revolvable about the axis of the instrument, that is.
to say:
Figure 2 is a plan view of the instrument looking towards the fixed cover;
Figure 3 is a plan of the mechanism, supposing the fixed cover removed and the
cylindrical case in section;

page_text: 10oking the direction of the
arrow;
Figure 5 is a similar view, some of the parts being removed;
Figure 6 is a plan of the revolving cover side of the instrument;
Figure 7 is a view similar to Figure 3, some parts having been removed to shew
others beneath.
Figure 8 is a detail section of the counter, drawn to double the scale of the other
figures.
The same letters of reference indicate the same parts in all the figures.
A is the fixed cover or bottom of the case, B the revolving cover or disc turned
by a hinged handle C which folds down when the instrument is not in use, D is the
cylindrical part of the box provided with two sight apertures which are closed as
in Figure 3 when the instrument is not in use, by a sliding shutter E which turns
on the centre of the bottom A and at same time serves to close the sight aperture F
therein, the segment of this sliding shutter which closes said aperture being indicated
in Figure 2 by dotted lines. At the centre of the rotating cover B is fixed the
spindle G which carries a worm H and pinion I which gears with wheel L in one
with pinion M which gears with wheel N. The wheel N is cupped and contains a
spiral spring O attached at one end to the frame A' and at the other to wheel N,
the purpose of said spring being to hold the teeth of the gearing in contact even
when worn.
The face of wheel N is flush with the fixed cover on which are the
divisions corresponding to the reading (c) at the first station P¹ before referred to.
As shewn in Figure 8, at the centre of wheel N there is a counter disc Q held by a
spring R in engagement with the nut T, the counter disc Q being separated from
wheel N by a cup U fitting on a polygonal part of the spindle V which is round
where the wheel N and disc Q turn upon it. The worm H gears with the toothed
sector W to which the mirror X is attached, another mirror Y being pivoted to
the frame A in which all the parts are mounted. The exact position in which the
mirror Y is fixed is determined by a spring B' and adjusting screw C¹ whilst the
spring D', shewn in dotted lines in Figure 5, serves to ensure contact of the teeth
of sector W with the threads of worm H. In front of mirror Y is placed a tube K
guided by a pivot E' received in a slot F" and intended to receive a sighting device
which may be either a diopter or diaphragm with cross lines, or a telescope whose.
optical axis should pass by the summit of the mirror Y. Another tube K¹ is placed
within the instrument and serves as a box for the telescope or diopter, according as
the one or the other is used in the tube K. For this purpose, the bottom cover A
is provided with an aperture which corresponds with the tube K' and is closed by
a hinged lid G. At the top of the box a disc H' is screwed to the frame A¹, a
circumferential groove being left in which a ring J is fitted to turn freely under
the friction of a spring wire J. On the disc H is fixed the pivot of the stop-
wheel L' which has fourteen teeth and a convex segment and with which gears the
single tooth pinion M' on the spindle G whereby the latter is prevented from
making more than fifteen revolutions. The mirror Y is fixed and the mirror X is
movable, the latter partaking in the motion of the toothed sector W about its
pivot. W. These two mirrors make to one another an angle which may be made
o vary to the extent of 45°, from 22° 30' to 67° 30', by the rotation of the worm H
which gears with the toothed sector W. It follows that the angle made by the
bjects sighted, when the image of the one seen by direct vision coincides with that
of the other viewed by double reflection from the mirrors, may vary to the extent
f 90° from 45° to 135° since the angle made by the mirrors is half that made by
he two lines of sight. The pointer of the indicator N stands at zero of the
raduated scale when the angle of the lines of sight is 90°. The train of
wheels I, L, M, N, is so proportioned that the worm H makes fifteen revolutions
o one rovolution of wheel N.
gear
The rotating cover B is provided at the circumference with a graduation
orresponding to
cin
for the first revolution of the cover: for the six

page_text: and a half revolutions following the graduation is transferred to six and a half
spiral turns marked upon the cover. The pointer m has a vernier at each side.
On the circumference of ring J there are 200 divisions and one or more points of
reference n which may be marked with letters or other signs. Upon the cylindrical
part of the case is engraved a line which corresponds with the pointer m when the
pointer of the indicator N is at the zero of the graduation.
The mode of using the instrument for determining the distance (d) Figure 1 is as
follows: The operator being at the station P¹ takes the instrument between the
thumb and fore-finger of the left hand so as to be able to turn the handle C
with the right hand. The pointer of the indicator N being at zero, the sliding-
shutter E is moved so as to unclose the sight apertures in the circumference of the
casing D and the sight aperture F in the bottom A, in order that the visual rays
may enter the instrument. The point P is sighted directly through the sighting
device or telescope and the disc B is rotated in the direction of motion of the hands
of a watch until the signal S is also sighted in the same direction by the double
reflection of the mirrors X and Y. The number (c) at which the pointer; of the
indicator N now stands, is then read off on the graduated circle. The operator in
passing from the station P1 to the station P" measures the base 6 which is selected
of such length as to contain a whole number of tens of units of length. By
dividing (b) by 100, multiplying the quotient by the number (c) and subtracting
the product from the base (b) the first factor sought, viz. b sin y¹ is obtained. At
the station P the operator first places the stud q of the counter disc Qopposite the
pointer j, then by turning the ring J a point of reference n is brought opposite
the pointer m. With the instrument thus adjusted the station P is sighted and the
disc B rotated in the opposite direction to the motion of the hands of a watch until
the signal S is again sighted by double reflection of the mirrors X and Y. This
done the number (c¹) on the graduation of disc B which coincides with the point of
reference n is read off and this number is the second factor
1
which only
sin (y¹¹¹)
requires to be multiplied by the result of the previous operations to obtain the
distance (d). The number (c¹) should be read upon the margin of the disc B if
at the station P" but one revolution of the handle C has been made or upon
the 1st, 2nd, 3rd, or following convolutions of the spiral according as 1, 2, 3, or
more revolutions have been made, the number of said revolutions being denoted by
the motion of the pointer; with regard to the stud q of the counter Q.
It will be understood that by the arrangement and graduation of the principal
parts of the instrument that the number (c) obtained as above described has
reference to the differences between angles comprised between 17-6 (about) and 45°
but it may be obtained for differences not necessarily comprised between these
limits. The factor (c¹) may, in fact, be obtained for differences of angles less
than 17'6 by dividing the number 1000 by the number of divisions of the ring J
that the pointer mn is shifted from the point of reference n, since it will be
remembered that the smallest angles are proportional to their sines. In the present
6°
case, each division corresponds to 3'6 of which the sine is about 0.001. The
100
-
factor (c) may be obtained for angular differences greater than 45° by arranging
the instrument so as to give such angles of collimation and reading off the number a
denoted by the pointer :-

page_text: The determination of (e¹) for differences of angles greater than 45°;
(1) As regards the determination of the limit 17'6 it will be seen by examining
Figure 6 that the divisions of disc B commencing on the spirals and continuing to
the edge stop, at the number 200; beyond which limit they would be so close as to be
illegible. As these divisions give the factor (c) it is evident that the greatest
factor (c) that the instrument can give is 200. What then is the angle which
corresponds to ² = 200.
sin ẞ
It may always be so arranged that the lines of sight reflected by the mirrors shall
5 make an angle equal to ẞ; then as was done at the first station to obtain the
factor (c), we note the number indicated by the pointer; of disc N. Let a be the
number indicated by the pointer j, then

page_text: 100
The instrument has been described as applied to the determination of the
distance of one point from another which is inaccessible, this being usually the case,
and being the purpose for which the instrument would be most generally used.
But by a careful examination of the way in which the instrument is arranged and
graduated, it will be understood that it is capable of giving any angles and all the
corresponding trigonometric lines, so as to fulfil various military requirements for
laying down or surveying angles in the field for measuring distances and generally
for the solution of any geometrical topographical problem. Finally, it will be
understood that by the simultaneous employment of two such instruments at two
stations, the distance of a moving body may be ascertained, which is very important
for coast defence, forts, and for war-ships.
Having now particularly described and ascertained the nature of the said
invention and in what manner the same is to be performed, I declare that what I
claim is
1. An angle-measuring instrument or telegoniometer whose essential feature
consists of an inclined mirror Y opposite another one X which is oscillated by
turning the cover B of the instrument casing so that the doubly-reflected image of
the one signal can be brought to coincide with the image of the other signal
observed directly by means of a telescope or diopter whose optical axis passes the
edge of the mirror Y.
2. An instrument of the kind specified in Claim 1 in the form of a cylindrical
casing having a rotatable cover B attached to the axis G of a worm H and
pinion I, the worm gearing with a toothed sector W for adjusting the mirror X
whilst the pinion I simultaneously rotates a toothed indicator-wheel N provided
with a pointer whereby the measurement of the oscillation of the mirror can be
read off on a fixed circular scale.
3. In an instrument constructed as specified in Claim 2, a freely-rotating
registering disc Q carried on the axis V of the wheel N but not rotating with it,
whose index stud q can be placed opposite the pointer; upon the indicator wheel N
for the purpose of enabling the whole number of the revolutions made by the
cover B to be read off on the scale of the registering disc.
4. In an instrument of the kind specified in Clauses 2 and 3, (a) the contrivance
shewn in Figure 7 limiting the number of the revolutions of the cover B, which
consists essentially of a stop wheel L' journaled in the casing, having a convex
segment and one tooth less than the maximum number of revolutions and gearing
with a single-tooth pinion M¹ carried on the axis G of the cover B; (b) the train
of gearing I, L, M, N, so proportioned that the indicator wheel provided with
pointer rotates once when the cover B has made the maximum possible number
of rotations.
5. In an instrument of the kind specified in Claim 1 a ring J surrounding the
movable cover B rotating freely between it and the cylindrical casing carrying a
pointer and scale and one or more points of reference n.
6. In an instrument of the kind described for facilitating calculations in
measuring distances by observations at the ends of a base of known length (a) the
division of the circle on which the angle of inclination of the movable mirror, with
the aid of the pointer; upon the indicator wheel N, is measured in such a way that
the multiple of the difference (preferably in hundredths) between unity and the
sine of the angle formed by the direct lines of sight towards both signals can be
read off [c100 (1 sin y] (b) the division of the movable cover B in such a
manner that the reading off of the rotation of the cover B against a point of
-

page_text: reference n of the ring J surrounding it corresponds directly to unity divided by
the sine of the difference of the observed angles [e¹
=
1
sin. (y² — yl²)].
-
7. In the division referred to in Claim 6 (b) the arrangement of the scale
corresponding to its first revolution of the cover B on the periphery of the cover
whilst the scale corresponding to its further revolutions is upon a spiral line, as
shewn in Figure 6.
8. The herein described instrument, constructed and operating substantially as
herein described, for measuring distances and other purposes as herein specified.
Dated this 21st day of April 1893.
E. FALLETTI,
By A. M. & Wm. Clark,
53, Chancery Lane, London, Chartered Patent Agents.