An Instrument for Measuring Distances.
Year: 1895

page_text: Date of Application 10th June, 1895
Complete Specification Left, 3rd Mar., 1896-Accepted, 4th Apr., 1896
PROVISIONAL SPECIFICATION.
An Instrument for Measuring Distances.
I, CESARE PAVESE, of No. 2 Rue de la Fortezza, Florence, Italy, Inspector of
Surveys, do hereby declare the nature of this invention to be as follows:-
11
This invention relates to an instrument for measuring distances which is
composed of a reflecting prism contained within a metal case with screens, as
I will describe with reference to the accompanying drawing. The prism is of the
pentagonal form shewn in plan at Fig. 1. Of the five faces the two large ones TR
and TS are made to act as mirrors, and the two smaller ones Rn and Sm through
which the sightings are taken are polished but transparent while the face m n is
left dull. The faces Rn and Sm are partly covered by small prisms am bn,
which serve for varying by a given quantity the direction of the incidental or
reflected rays of light.
The prism is so formed as to give by means of its reflecting faces a rectangular
reflection when looking through that portion of the faces Rn and Sm not covered
by the small prisms, that is to say, on looking for instance through the face Sm
Fig. 3 in the direction Od, an object A will be observed situated on a line AR at
right angles to Od, or the object A will appear in the extension of Od, at A¹.
If on the other hand an observation be taken through one of the small prisms
say bn on the one face Rn, and through the uncovered part of the other face S m,
then the direction of the line from the reflected image will form with the line of.
observation an angle the tangent of which has the value, 20, 50, 100 &c. according
to the nature of the prism bn. Instead of having only one prism bn am on each
face, there may be two on each, of half the width of the single one, each one being
of different form.
The casing of the prism covers the whole of it with the exception of the faces Sm
and Rn, as shewn at Fig. 2.
It consists firstly of an upper and lower metal plate F and E, secondly of two
small lateral plates of which the angular one G covers the two reflecting faces of.
the prism, while the other H Fig. 4 covers the face mn and serves to unite the
other plates together; thirdly there is provided a loop I forming a handle for
holding the instrument, and which is secured by screws to the plates G and H, so
as to turn with a certain amount of friction.
The upper plate is soldered to the back plate H and carries two pivotted
diaphragms or covers L L' which serve to cover half of the faces S m and Rn of
the prism when the other half of the face is being used. The union of the upper
plate with the frout plate G is effected only at the two ends of the latter so as to
leave at the middle part a slit corresponding to a small space above the prism
between it and the plate F, which space and slit serve for sighting. A similar slit
is also formed at the bottom, the prism being however firmly cemented to the
lower plate so as to maintain it in a fixed position relatively to the other. parts of
the casing.
The instrument thus constructed allows observations to be made of objects either
to the right hand or the left hand of the observer, and with plate F either
uppermost or lowermost.
On these plates are engraved arrows for indicating the parts of the prism which
bave to be used together in certain cases. For observing the right angle, the

page_text: .
:
parts indicated by the arrow marked R are uncovered. When angles the tangents
of which are 20, 50, 100 &c. are to be observed, the parts indicated by the other
arrows, marked Nos. 20, 50, 100 &c. are uncovered.
The instrument is used as follows. It is held in the one or the other hand by
passing the first finger through the loop. I as at Fig. 4. In looking into the prism
several images will be seen, but only one will be acromatic, that is to say, without
coloured edges, and it will be seen when looking in the direction of the screws
connecting the loop to the casing. This is the object employed for making
observations. Assuming the observer to be situated at A Fig. 5 and that he
requires to measure the distance of the object C, then in holding the instrument
as described with its upper face in the direction of C, he turns one of the
observing faces to that point, and looks for the image of the object in the prism
through the part of the other face which gives the right angle, the small prisms
being covered by their covers as before described.
Then without losing sight of the image, he also searches through the before
mentioned upper space and slit for an object on the ground in front of him that lies
in the direction of the reflected image of C, and finding such an object at D he
moves slightly forward or backward and manipulates the instrument so as to cause
the image of C to exactly cover D; he then marks a line on the ground with his
foot exactly in front of the latter, giving his position under these circumstances;
he then turns one of the pivotted covers so as to uncover the small prism which is
required to be used, and he then moves backward on the line D A until, on looking
through the part of the prism, which has been uncovered, he again observes the
objects C and D covering each other. He then makes a mark on the ground
- corresponding to his position under these circumstances, say at B, and he measures
the distance between A and B in centimetres. This number of centimeters will
then indicate the corresponding number of meters which the object C is distant if
-the small prism which has been used is marked 100; if, instead, it is marked 50, the
distance will be given by half the above number in metres; if it is marked 200,
the distance will be double the above number, and so on.
Dated this 10th day of June 1895.
ABEL & IMRAY,
Agents for the Applicant.
'
An Instrument for Measuring Distances.
I, CESARE PAVESE, of No. 2 Rue de la Fortezza, Florence, Italy, Inspector of
Surveys, 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 an instrument for measuring distances which is com-
posed of a reflecting prism contained within a metal case with screens, as I will
describe with reference to the drawing accompanying my Provisional Specification.
The prism is of the pentagonal form shewn in plan at Figure 1. Of the five faces
the two large ones TR and TS are made to act as mirrors, and the two smaller
ones Rn and Sm through which the sightings are taken are polished but trans-
parent while the face m n is left dull. The faces Rn and Sm are partly covered
by small prisms am, bm, which serve for varying by a given quantity the direction
of the incidental or reflected rays of light.
The prism is so formed as to give by means of its reflecting faces a rectangular
reflection when looking through that portion of the faces Rn and Sm not covered
by the small prisms, that is to say, on looking for instance through the face Sm
Figure 3 in the direction Od, an object A will be observed situated on a line A R

page_text: at right angles to Od, or the object A will appear in the extension of Od at A¹.
If on the other hand an observation be taken through one of the small prisms
say bn on the one face Rn, and through the uncovered part of the other face Sm,
then the direction of the line from the reflected image will form with the line of
observation an angle the tangent of which has the value 20, 50, 100, &c. according
to the nature of the prism bn. Instead of having only one prism bn am on each
face there may be two on each of half the width of the single one, each one being
of different form.
The casing of the prism covers the whole of it with the exception of the faces Sm
and Rn, as shewn at Figure 2.
It consists firstly of an upper and lower metal plate F and E, secondly of two
small lateral plates of which the angular one G covers the two reflecting faces of
the prism, while the other H Figure 4 covers the face m n and serves to unite the
other plates together; thirdly there is provided a loop I forming a handle_for
holding the instrument and which is secured by screws to the plates G and H so
as to turn with a certain amount of friction.
The upper plate is soldered to the back plate H and carries two pivotted
diaphragms or covers L L' which serve to cover half of the faces Sm and Rn of
the prism when the other half of the face is being used. The union of the upper
plate with the front plate G is effected only at the two ends of the latter so as to
leave at the middle part a slit corresponding to a small space above the prism
between it and the plate F, which space and slit serve for sighting. A similar slit
is also formed at the bottom, the prism being however firmly cemented to the
lower plate so as to maintain it in a fixed position relatively to the other parts of
the casing.
The instrument thus constructed, allows observations to be made of objects
either to the right hand or the left hand of the observer and with plate F either
uppermost or lowermost.
On these plates are engraved arrows for indicating the parts of the prism which
have to be used together in certain cases. For observing the right angle, the
parts indicated by the arrow marked R are uncovered. When angles the tangents
of which are 20, 50, 100 &c. are to be observed, the parts indicated by the other
arrows, marked Nos. 20, 50, 100 &c. are uncovered.
The instrument is used as follows. It is held in the one or the other hand by
passing the first finger through the loop I as at Figure 4. In looking into the
prism several images will be seen, but only one will be achromatic, that is to say
without coloured edges and it will be seen when looking in the direction of the
screws connecting the loop to the casing. This is the object employed for making
observations. Assuming the observer to be situated at A Figure 5 and that he
requires to measure the distance of the object C, then in holding the instrument as
described with its upper face in the direction of C, he turns one of the observing
faces to that point, and looks for the image of the object in the prism through the
part of the other face which gives the right angle, the small prisms being covered
by their covers as before described.
Then without losing sight of the image, he also searches through the before
mentioned upper space and slit for an object on the ground in front of him that
lies in the direction of the reflected image of C, and finding such an object at D he
moves slightly forward or backward and manipulates the instrument so as to cause
the image of C to exactly cover D; he then marks a line on the ground with his
foot exactly in front of the latter, giving his position under the circumstances; he
then turns one of the pivotted covers so as to uncover the small prism which is
required to be used, and he then moves backward on the line D A until on looking
through the part of the prism, which has been uncovered, he again observes the
objects C and D covering each other. He then makes a mark on the ground
corresponding to his position under these circumstances, say at B, and he measures
the distance between A and B in centimetres. This number of centimeters will
then indicate the corresponding number of meters which the object C is distant if

page_text: the small prism which has been used is marked 100, if instead, it is marked 50, the
distance will be given by half the above number in metres; if it is marked 200;
the distance will be double the above number, and so on.
Having now particularly described and ascertained the nature of my said.
invention and in what manner, the same is to be performed I declare that what I
⚫claim is :
1. An instrument for measuring distances consisting mainly of a prism with
double reflection for sighting a right angle and other predetermined angles for
which purpose it is combined with one or more other prisms arranged and operating
substantially as herein described with reference to the drawings.
2. In an instrument for measuring distances such as is referred to in the first.
claim, the combination with the sighting prisms of upper and lower plates such as F
and E, a front and rear plate such as G and H, carried by a loop or ring, and two
pivoted diaphragms such as L and L', arranged and operating substantially as
herein described with reference to the drawings.
Dated this 3rd day of March 1896.
ABEL & IMRAY,
Agents for the Applicant.