IMPROVED MEANS AND APPARATUS FOR Mano' Dreman A'ARDS AWAY " FOR MEASURING DISTANCES, ALTITUDES, AND ANGLES
Year: 1872

page_text: LETTERS PATENT to Charles August Constantin Eckhold, of Green
Street, Leicester Square, in the County of Middlesex, Civil
Engineer, for the Invention of "IMPROVED MEANS AND APPARATUS FOR
Mano' Dreman A'ARDS
AWAY"
Scaled the 28th March 1873, and dated the 2nd October 1872.
PROVISIONAL SPECIFICATION left by the said Charles August
Constantin Eckhold at the Office of the Commissioners of Patents,
with his Petition, on the 2nd October 1872.
I, CHARLES AUGUST CONSTANTIN EOKHOLD, of Green Street, Leicester
Square, in the County of Middlesex, Civil Engineer, do hereby declare
the nature of the said Invention for "IMPROVED MEANS AND APPARATUS
"
FOR MEASURING DISTANCES, ALTITUDES, AND ANGLES,” to be as follows :—
The object of this Invention is to enable the distance of an object of
a known length from any point to be determined directly and without
the necessity of moving from the place of observation, and in the case

page_text: when the length of the object is not known to find in the shortest
manner the data required for calculating the distance, and in like
manner to find the altitude of an object when required.
The Invention consists,―
1st. In the use of a prism of a determined angle of refraction or of 5
two simple mirrors, so arranged opposite to one another that they will
reflect an object in front of them to the eye behind them. The prism
or the mirrors is or are attached to a circle or its alhidade, which move
round the sight axis of a telescope to which it or they are fitted, and is
or are so placed before the object glass of the telescope that an object 1
seen through the latter will not only be seen directly, but also refracted
or reflected.
2ndly. In the use of a circle graduated with or without an allidade, or
not graduated, and in this case it would be connected with a scale
moved by a micrometer screw with a graduated disc. This circle is 1
fastened to the telescope and rotates contrically or excentrically around
its sight axis, or when fitted with a rotating alhidade remains
stationary.
3rdly. In the use of a single or double telescope provided with cross
or hair lines at right angles to each other, and capable of being attached 2
to a handle or table. The telescope is so constructed that by the use of
another prism refracting rectangularly an object will be seen which is at
right angles to the line of sight. The telescope is not essential when
short distances have to be determined, as it may be replaced by a rule or
box with sight lines.
4thly. In the use of a level fixed on the circle, or on the telescope, or
in the case, when the telescope is connected with a horizontal circle tho
level may be fixed on the latter.
2
'
The operation of the instrument is as follows:-The telescope will be
so directed towards the distant object that the centre of the cross or 3
hair lines covers one end of the object, while one cross line covers its
whole length. The alhidade or the circle of the prism or mirror is then
moved so as to bring the image of the object refracted from the prism or
reflected from the mirrors into such a position that the end opposite to
the one covered by the centre of the cross lines comes into the plane of 3

page_text: the cross line which is at right angles to the cross line which covers the
object. The circle or the alhidade is then fixed and the reading effected.
This reading shows the value of the angle, which has its centre at the
one end of the object and its two sides in the direction of the two ends
5 of the image of the object, and in the case when a scale is used the value
of the sinus of this angle.
SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said Charles August Constantin Eckhold, in the Great
Seal Patent Office on the 2nd April 1878.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, CHARLES
AUGUST CONSTANTIN ECKHOLD, of Green Street, Leicester Square, in
the County of Middlesex, Civil Engineer, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Second day of October, in the year of our
Lord One thousand eight hundred and seventy-two, in the thirty-sixth
year of Her reign, did, for Herself, Her heirs and successors, give and
grant unto me, the said Charles August Constantin Eckhold, Her special
licence that I, the said Charles August Constantin Eckhold, my executors,
administrators, and assigns, or such others as I, the said Charles August
Constantin Eckhold, my executors, administrators, and assigns, should at
any time agree with, and no others, from time to time and at all times
thereafter during the term therein expressed; should and lawfully might
make, use, exercise, and vend, within the United Kingdom of Great
Britain and Ireland, the Channel Islands, and Isle of Man, an Invention
for "IMPROVED MEANS AND APPARATUS FOR MEASURING DISTANCES, ALTITUDES,
AND ANGLES," upon the condition (amongst others) that I, the said Charles
August Constantin Eckhold, my executors or administrators, by an in-
strument in writing under my, or their, or one of their hands and seals,
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 Charles August Constantin Eckhold,
do hereby declare the nature of my said Invention, and in what manner

page_text: the same is to be performed, to be particularly described and ascertained
in and by the following statement thereof, reference being had to the
Drawings hereunto annexed, that is to say :-
The object of this Invention is to enable the distance of an object of a
known length from any point to be determined directly and without the
necessity of moving from the place of observation, and in the case when
the length of the object is not known, to find in the shortest manner the
data required for calculating the distance, and in like manner to find the
altitude of an object when required.
The Invention consists,―
First. In the use of a prism of a determined angle of refraction, or of
two simple mirrors so arranged opposite to one another that they will
reflect an object in front of them to the eye behind them. The prism or
the mirrors is or are attached to a circle or its alhidade, which moves
round the sight axis of a telescope to which it or they are fitted, and is 1
or are so placed in relation to the object glass of the telescope than an
object seen through the latter will not only be seen directly, but also
refracted or reflected.
Secondly. In the use of a circle graduated or not, with or without aņ
alhidade, or not graduated, and in this case it would be connected with 2
a scale moved by a micrometer screw with a graduated disc. This circle
is fastened to the telescope, and rotates centrically or excentrically
around its sight axis, or when fitted with a rotating alhidade remains
stationary.
The operation of the instrument is as follows:-The telescope will be 2
so dirccted towards the distant object that the centre of the cross
or hair lines covers one end of the object, while one cross line
covers its whole length. The alhidade or the circle of the prism or
mirrors is then moved so as to bring the image of the object refracted
from the prism or reflected from the mirrors into such a position that the 3
end opposite to the one covered by the centre of the cross lines comes
into the plane of the cross line which is at right angles to the cross
line which covers the object. The circle or the alhidade is then fixed,
and the reading effected. This reading shows the value of the angle
which has its centro at the one end of the object, and its two sides in the 3
direction of the two ends of the image of the object, and in the case.
when a scale is used the value of the tangent of this angle.

page_text: The Invention will be well understood by reference to the accompanying
Drawings in which Figure 1 is a transverse section through the telescope
near the circle with its alhidade, and showing both. The circle A with
its hollow axis O is fixed to the telescope tube L at a point between the
› object and eye glasses. The alhidade B is connected to the circle and
revolves round the axis O for about 90°. To this albidade the prism R
situated in the interior of the telescope is connected by means of the
bearer P in such a manner that it revolves with the alhidade, and so
that the object to which the eye is directed when looking through the
telescope V is seen refracted; the prism R can be brought into a
vertical position when the telescope is inclined, or vice versa, by means
of a key S which can be put into the fastening of the prism when
necessary. This key S is connected with a "level" so as to ascertain
the inclination of the telescope and consequently of the prism. The
alhidade B is provided with another and one armed alhidade O, in order
to replace the ordinary vernier when desired. The albidade C is fastened
over the alhidade B in such a manner that by means of the tangential
screw D provided with a divided disc E and a fixed vernier F it can be
moved one division of the circle A, when the other alhidade B is fixed
or clamped to the circle C by means of the screw G. A microscope is
fastened upon the one armed alhidade by means of the bearer M, and
when directed to the divisions marked on the circle enables the motion
of the tangential screw to be accurately and minutely ascertained. The
albidade B is provided with the usual micrometer screw K for producing
its finer motions.
Figure 2 represents the hair lines in the focus of the telescope
magnified; a is the horizontal hair line, and 6 is the vertical one; o is
the object under the horizontal line a, and o' is the image of the object
brought by means of the refraction of the prism just over the horizontal
line a, and a is the angle which has its centre c in the cross point of the
above-mentioned lines, its two sides c, d, and c, e, being in the direction
of the ends of the refracted object. Now supposing the height of the
object o known and the divergence between the sight line and the
refracted line is also known for a certain length (as it is because the
angle of refraction of the prism is ascertained, and the distance of the

page_text: corresponds to the divergence between the object and its refracted image.
It will be therefore understood that the distance can be discovered by a
simple proportion, thus :-As certain divergence is to a certain length so
is the divergence between the object and the refracted image of the object
to 2 (the distance). This example presumes that the distance from the eye i
to the object is in a horizontal plane. If, however, the object be in an
inclined plane from the eye, the distance could be found by knowing
the angle of altitude, as the co-sinus of this angle multiplied by the
height of the object would correspond to the vertical height of the object
in relation to the ascertained angle x.
1
This angle of altitude can be found in two manners:-First, when the
instrument has a vertical circle this angle will be measured directly by the
circle; and secondly, when the instrument is not provided with a vertical
circle the angle of altitude is ascertained in relation to the angle x by
bringing the prism through the action of the keys into the vertical 1
position. The actually inclined object is then seen as an object situated
in a vertical plane, and in its natural size as the angle x is changed
into another angle, say angle z³, by thus bringing the prism into a vertical
plane.
It will be understood that by means of the relation between angle
and angle ¹ that the distance as well as the altitude can be easily
determined. The altitude could also be measured by connecting the
altitude of the circle with a rectangular prism or mirror placed outside
the telescope and beyond the object glass. Horizontal angles are
measured by my instrument by connecting it with a horizontal circle i
as is usually done with theodolites.
Although I have only shown a prism in the Drawings, yet this may
be replaced by other appliances; one method, that of double mirrors, has
already been referred to. Another method consists in substituting for
the prism a small piece of ordinary glass with cross lines marked a
thereon, or what is the same thing, a small frame with hair lines
stretched across it, movable with the alhidade in the same manner as
the prism. The cross point of these lines will represent the refraction
of the prism, and the angle x to the object will be ascertained in the
same manner as by the prism, by bringing the object under the a
horizontal line a (Figure 2), and turning the albidade so as to bring the
cross point of the frame above the opposite end of the object..

page_text: It will be understood that the object is scen on a horizontal line a,
Figure 2, but not in the centre of the telescope.
Figure 3 shows in cross section another arrangement of my apparatus
for the purpose of enabling the value of the angle x, to be ascertained
5 by the means of a microscope M, M³, solidly fixed on the alhidade B,
so that it moves with the latter round the circle A. This microscope M'
has a rectangular prism T in its inside so as to enable its eye piece to be
arranged parallel with the eye piece of the telescope, and thus to read the
scale Z which. is at right angles with the telescope. The microscope
has a rack inside moved by the screw W so as to bring the scale Z' into
the focus of the microscope. The scale Z' is so arranged as to slide"
for the length of one of its divisions on its seat Z by means of the
micrometer screw Y with the divided disc D and fixed vernier V.
N, N, are supports to which the scale is attached if not otherwiso
5 supported by the table of the instrument. The other parts of this
arrangement are exactly similar to the one already described.
The mirror
Figure 4 is a longitudinal section of the end portion of a telescope A,
of which the tube I with the piece I' holding the object glass is drawn
out or in. M is a mirror fixed between two bearers T, T, which are in
▸ connection with the alhidade; m, m, are little plates by which the
mirror M is fastened to a plate G of corresponding shape. The mirror
and plate are free to slightly turn upon the screws K, K.
is so arranged in relation to the bearers that its bearing axis will be out
of the circumference of the object glass, so that when the mirror is not in
› use the sight through the telescope will be as unobstructed as if the
mirror did not exist. This arrangement with the mirror is for the
purpose of measuring altitudes by means of the circle C.
Figure 5 shows how an object is refracted when seen through the
telescope; E is the eye piece; P the prism; and O the object.
And having now described the nature of my said Invention, and in
what manner the same is to be performed, I declare that I claim,―
First. The general construction and arrangement of apparatus for
measuring distances, altitudes, and angles, as described and shown with
reference to the accompanying Drawings.
Secondly. The arrangement of apparatus, as described and shown
with reference to Figure 1 of the accompanying Drawings for the

page_text: . Thirdly. The arrangement of apparatus, as described and shown with
reference to Figure 3 of the accompanying Drawings for the purposes
set forth..
Fourthly. Measuring distances, altitudes, and angles by means of the
combination of a circle with an alhidade, in connection with a prism or
frame, with cross lines situated in the interior of a telescope, substantially
as described and shown.
And fifthly. The arrangement of mirror for measuring altitudes, as
described and shown with reference to Figure 4 of the accompanying
Drawings.
In witness whereof, I, the said Charles August Constantin Eckhold,
have hereunto set my hand and seal, this Second day of April,
One thousand eight hundred and seventy-three.
1