AN IMPROVED OPTICAL INSTRUMENT, WHICH THE INVENTOR DENOMINATES A TROPESCOPE
Year: 1858

page_text: LETTERS PATENT to William Edward Newton, of the Office for Patents,
66, Chancery Lane, in the County of Middlesex, Civil Engineer, for the
Invention of "AN IMPROVED OPTICAL INSTRUMENT, WHICH THE INVENTOR
DENOMINATES A TROPESCOPE."-A communication from Giovanni Caselli, of
Florence.
Sealed the 27th July 1858, and dated the 18th February 1858.
PROVISIONAL SPECIFICATION left by the said William Edward Newton
at the Office of the Commissioners of Patents, with his Petition, on
the 18th February 1858.
I, WILLIAM EDWARD NEWTON, of the Office for Patents, 66, Chancery Lane,
in the County of Middlesex, Civil Engineer, do hereby declare the nature of
the said Invention for "AN IMPROVED OPTICAL INSTRUMENT, WHICH THE INVENTOR.
DENOMINATES A TROPESCOPE," to be as follows:-
The improved optical instrument forming the subject of this Invention is
simple in its construction, and may be made of any suitable dimensions,.
according to the purpose to which it is intended to be applied. The one con-
structed by the Inventor as a specimen is composed of two prisms enclosed in
a case, consisting of two metal tubes. The larger of these tubes encloses the
larger prism, which constitutes the object glass of the instrument. The other

page_text: prism, which is of smaller dimensions, constitutes the eye-glass, and is enclosed
in the small tube, which may be turned round in the same manner as the eye-
piece of an ordinary telescope. The two circular extremities of the instrument
are closed by plain glasses, which serve to protect the surface of the prisms
from dust being deposited thereon.
The space left between the sides of the prisms and the tubes is filled up by
means of pieces of cork, so that there is left in each tube merely a rectangular
opening for the passage of the rays of light.
If the small tube containing the smaller prism be turned in such a manner
that the inclined faces of the two prisms shall be parallel to each other, no
change will be visible in the position of the objects looked at through the
instrument, as the reversed symmetrical image which would be produced by a
single prism is again reversed by the other prism, which, acting in the con-
trary direction, gives in its turn a symmetrical image of the first. The same
negative result will take place on looking: "through the instrument, after
having turned one of the prisms half round; but on turning the small prism a
quarter of a revolution further; so as to bring its plane of reflection at a right
angle to that of the object prism or larger one, the second reflection will be
the same as the first, and the image of the object being reversed will cease to
be symmetrical. If, whilst looking through the tropescope, an axial motion be
given to it, no alteration will take place in the images, but if the eye-glass
or object-glass only be turned, the same; objects will be seen to turn round
a common centre at a speed double that which is communicated to the prism.
This combination of two prisms may be applied to the construction of
different kinds of optical instruments, such as telescopes or glasses, either for
astronomical or other purposes.
In applying this system to astronomical telescopes the image of the heavens
would be seen in its natural position.
In applying it to telescopes or glasses. for terrestrial purposes, it might with
advantage be employed as a substitute for the, lenses which serve to invert
reversed images, at the same time it would have the advantage of enabling
objects to be seen in every direction.
The simple tropescope, as above described, may be employed for various
purposes. Artists; sculptors, engravers, and other artists may with this instru-
ment observe their work on all sides, and in every direction, instead of
employing as at present simple mirrors, which, by reversing the objects,
somewhat disfigure them, only reproducing the symmetrical image: thereof..
By means of the tropescope several persons seated round the same table

page_text: may at the same time and without moving from their places read a book or
newspaper placed on the table.
Plans, maps, and drawings will also by this means appear to the eyes of the
spectators in the position they may desire from: whatever side they may be
observing.
. Lastly, this prismatic apparatus may serve for various purposes, which it is
not necessary here to enumerate
SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said William Edward Newton in the Great Seal Patent Office
on the 18th. August 1858.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, WILLIAM
EDWARD NEWTON, of the Office for: Patents, 66, Chancery Lane, in the County
of Middlesex, Civil Engineer, send greeting:
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Eighteenth day of February, in the year of our Lord
One thousand eight hundred and fifty-eight, in the twenty-first year of Her
reign, did, for Herself; Her heirs and successors, give and grant unto me, the
said William Edward Newton, Her special license that I, the said William
Edward Newton, my executors, administrators, and assigns, or such others as
I, the said William Edward Newton, 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 "AN
IMPROVED OPTICAL INSTRUMENT, WHICH THE INVENTOR DENOMINATES A TROPE-
SCOPE," being a communication. from Giovania Caselli, of Florence, upon
the condition (amongst others). that I, the said William Edward Newton,
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 William Edward Newton, do hereby
declare the nature of the said Invention, and in what manner the same is
to be performed, to be particularly described and ascertained in and by the

page_text: following statement, reference being had to the Drawing hereunto annexed,
and to the letters and figures marked thereon (that is to say) :-
The improved optical instrument forming the subject of this Invention is
simple in its construction, and may be made of any suitable dimensions,
according to the purpose to which it is intended to be applied.
It is composed of two prisms, denominated by the Inventor "prismes à
réflexion totale," which are enclosed in a case consisting of two telescope tubes,
as shewn at a and b in Fig. 1, which is a side view of the instrument; Fig. 2
is an end view, with the prism in a different position. One of these tubes a
encloses a prism 1, which constitutes the object-glass; the other prism 2, which.
is of smaller dimensions, is the eye-glass, and is enclosed in the smaller tube b,
which forms the eye-piece, and may be turned round and drawn out or pushed
in at pleasure in the same manner as the eye-piece of an ordinary telescope.
The spaces left between the prisms and the sides of the tubes are filled up with
pieces of cork, so that there only remains in the tubes rectangular openings
(a, b, c, d, and e, f, g, h, Fig. 2,) for the passage of light.
The two extremities of the instrument are closed by plain glasses, which
serve to protect the surfaces of the prismis from the deposit thereon of dust.
The instrument as herein described will shew the objects inspected of
their natural size, but if it be desired to magnify the objects it will only be
necessary to substitute lenses for the plain glasses at the extremities of the
instrument.
In Fig. 1 of the accompanying. Drawing the prisms are shewn arranged in
such manner as to present the prism 1 in front view and the prism 2 in side
view. The course of the rays of light in passing through these prisms may be
readily traced by reference to the Diagram, Fig. 3. The lines a, b, a, c, a, d,
represent the direction of the rays by which the eye situate at a sees the object
b, d, which is a large letter B shewn in red, and in an inverted position. The
rays b, c, d, are subjected to a double refraction and reflection in their passage
through each of the two prisms; the direction or course of these rays may be
seen in the prism 1, the base of which is represented by the line m, m. The
same effects are produced in the other prism, but as the base or plane of
reflection of this latter prism is in a vertical position, and the Figure is
geometrically drawn, the angles of the rays (which are necessarily in a straight
line) cannot be seen.
Supposing the instrument to consist simply of the prism 1, the eye placed
at the point a would see the inverted but symmetrical image of the letter B
which would be formed at the point e, f, at the extremity of the prism, but by

page_text: combining the two prisms as seen at Fig. 3, a reversed image of the large B
will be produced at the point g, h, which will be similar in form to that pro-
duced at e, f, but inverted.
The effects above described also take place when the planes of reflection of
the two prisms are placed at right angles to each other, as in Fig. 2; but on
turning the small tube a (Fig. 1) so as to bring the planes of reflection parallel
to each other, there will be no change in the position of the object which is
undergoing inspection, as the image produced by one prism is reversed by the
contrary action of the other. On turning the instrument round without
altering the respective positions of the two prisms, no movement is perceptible
in the images produced, but on turning one of the prisms the images will be
seen to move round a common centre, which is coincident with the prolongation
of the axes of the instrument.
This instrument may be employed for various purposes too numerous to
mention; for instances, painters, sculptors, engravers, and others, may with
this instrument inspect their work on all sides and in any direction (i. e. from
any point of view), instead of employing (as is ordinarily done) simple mirrors,
which reverse and somewhat distort the objects. By means of these improved
instruments several persons seated round the same table may all at the same
time read from the same book or paper placed on the table without moving
from their seats, as the writing or print may be made to appear in any
position required by the spectators wherever they may be placed. The same
effect may of course be produced with maps, plans, and drawings.
I would observe, in conclusion, that the improved optical instrument above
described is complete in itself, but it may also be applied to other optical
instruments, and that in applying this novel arrangement of optical instrument
to astronomical telescopes, the image of any object in the heavens will be seen
in its real position instead of being inverted, as is the case with the ordinary
astronomical telescope, and if adapted to a common telescope for viewing
terrestrial objects, the above described arrangement or combination of prisms
may be substituted for the combination of lenses which serve in those instru-
ments to invert the images of objects, and at the same time the instrument
would possess the advantage of showing objects in any position required.
Having now described the Invention of "An Improved Optical Instrument,
which the Inventor denominates a Tropescope," and having explained the
manner and principle of constructing the same, as communicated to me by my
foreign correspondent, I claim as the Invention secured to me by Letters
Patent as aforesaid, the arrangement or combination of prisms as above

page_text: shewn and described for the purposes of producing theo ptical effects herein
set forth.
In witness whereof, I, the said William Edward Newton, have heréuntó
set my hand and seal, the Seventeenth day of August, in the year
of our Lord One thousand eight hundred and fifty-eight.
Witness,
J. W. MOFFATT,
66, Chancery Lane.
W. E. NEWTON. (L:S.)