IMPROVEMENTS IN PHOTOGRAPHY IN COLOURS, AND IN THE APPARATUS FOR THAT PURPOSE
Year: 1876

page_text: LETTERS PATENT to William Morgan-Brown, of the Firm of Brandon and
Morgan-Brown, Engineers and Patent Agents, of 38, Southampton Buildings,
London, and 13, Rue Gaillon, Paris, for the Invention of "IMPROVEMENTS IN
PHOTOGRAPHY IN COLOURS, AND IN THE APPARATUS FOR THAT PURPOSE." A
communication from abroad by Louis Ducos Duhauron, of Agen (Lot and
Garonne), France, Chemist.
aled the 17th November 1876, and dated the 22nd July 1870
COMPLETE SPECIFICATION filed by the said William Morgan-Brown at
the Office of the Commissioners of Patents on the 22nd July 1876.
WILLIAM MORGAN-BROWN, of the Firm of Brandon and Morgan-Brown,
Engineers and Patent Agents, of 38, Southampton Buildings, London, and 13,
Rue Gaillon, Paris. "IMPROVEMENTS IN PHOTOGRAPHY IN COLOURS, AND IN
THE APPARATUS FOR THAT PURPOSE." A communication from abroad by Louis
Ducos Duhauron, of Agen (Lot and Garonne), France, Chemist.
GENERAL DESCRIPTION OF THE SYSTEM.
The problem of photography in colors such as I express it does not consist in
submitting to the luminous action a surface prepared in a manner to appropriate
and preserve at each point the colouration of the rays which strike it. What I
ask is that the sun avails itself judiciously of an invariable palette, to which it is
trusted. It must be that he only charged with the choosing and the mixing of the
colours furnished to him will obtain incomparable copyist the most learned and the
most authentic of the representations of nature. The problem being defined in
these terms, an observation that I have checked by numerous experience has served
for the point of departure to resolve it. That observation is this: In opposition to
the colors of the spectrum, the scale of which is formed of innumerable shades, and
allows of our distinguishing and naming seven principal ones, the coloring substances
which serve to express them are reduced to three; red, blue, yellow. This triplicity
of colors has been of long date experimentally but confusedly recognised; if it had
been verified beyond possibility of doubt it would have long since been an axiom,

page_text: if in place of making the mixtures with the brush, the molecular mixtures of these
three colors (an operation which leads to trouble and disorder in the results) the
painters had been led as I have been to accomplish the optical mixture, the only
one which should be perfect, they would have affirmed that which they announced
timidly, viz., that three pigments, red, blue, yellow, mixed in divers proportions,
produce all the shades. In other terms, if there are applied one upon the other,
and on a white ground, three transparent sheets or pellicles, one red, one blue, one
yellow, on each of which the coloring matter has been spread in variable thick-
nesses, the superposition of these three layers of colors, the intimate and mechanical
adaptation of the one to the other, gives rise to the infinite variety of known tints
comprising all gradations from black to white. This point of departure thus fixed,
I will explain by what reason I have arrived at this system of heliochromy. If it
is true that three colors produce, by the mixture which results from their super-
position, all the colors, it follows, per contra, that any picture, that is to say, a
surface formed of the assembling of all the color, or from the assembling of a
number more or less of colors, may in the mind decompose itself into three pictures,
the one red, the other blue, the third yellow, the superposition and the incorporation
of which reconstitute this same picture. This analysis and this synthesis that the
mind accomplishes so easily, it or is it not in the power of photography to
produce in reality? If it has that power the problem of photography in colors is
solved. Interrogated in this fashion, and forced to explain herself, nature has
replied, Yes; my three pictures, the one red, the other blue, the other yellow, have.
passed from the domain of theoretical speculation into palpable reality. Photo-
graphy has delivered them to me, and I have only had to accomplish by
manipulation the superposition and unification to sce born immediately the copy,
par excellence, the integral polychromatic representation of the model.
To attain these results the difficulty one may imagine did not consist in the
printing in red; in blue, or in yellow the work of light; in one word, to get the
positive images of any one of the three colors (for a long time practically, thanks
to the discovery of M. Poitevin, we have photographs in color by the interposing
clichés monochromes of any shade at the wish of the operators), but to dispose and
manage the things in such a manner that upon each of the three monochromes,
and in the first place, on each of the three clichés (negatives) which should furnish
them, the sun should distribute with the characteristic difference of repartition
which it should have between them the black matter of this one, the colored
preparation of that one; that was the very knot of the question. I have mastered
it by an optical combination, of which the announcement would seem at first
paradoxical; this is the way I proceed -I obtain separately in the camera three
impressions, three negatives of the same subject, furnished by three different lights,
green light, orange light, and violet light; make the red monochrome under the
negative which is given by the green light, the monochrome blue under the negative
from the orange light, the monochrome yellow under the negative from the violet
light. Why these three lights, and why this intermixture, this (chassé croisé)
interchange of the colors? This is the reason, at least a brief explanation, for
there is in this a vast field of enquiry for science-Each of the three inonochromes
being formed by a preparation endowed with transparency, and susceptible of
being fixed by the action of the light, and proportionally to that actions each of
them, by the fact of the interverting of the colors above specified, will necessarily
give either as gradation of lights and shades or as a repartition of the special color
of the objects the desired image. And first, as gradation of the lights and shades,
leaving out the special color of the objects to be represented, each of the three
monochromes will be evidently exact, each of them in effect being furnished by a
negative (note) which gives the blacks of the object by white, and the whites of
the model by black, will give in its turn the blacks of the model by the preparation,
red, blue, or yellow, proper to that monochrome, and this red, or this blue, or this
yellow will be as much more intense as the black of the model is more black, and
reciprocally cach of them will give the whites of the model by the absence of the

page_text: coloring matter, that matter being eliminated under the blacks of the negative.
and as inuch more eliminated as the white of the model will be more white.
Note 1. The employment of negatives is supposed here, which is the most
common case, but positive clichés might be used if they were obtained by the
preparation employed to produce the nonochromes. This takes place notably for
the hygroscopic mixture of sugar and bichromate, the reasoning is alike in both
cases.
In the second place, as reparition of the special color to the objects which it is
required to represent, each of the three monochromes will be not less exact, and
it is this repartition which will engender from one monochrome to the other
the differences they should offer, and which will not arise by simple transfer of
the lights and shades. I take, for example, the monochrome red supplied by the
negative which is due to the green light. As the glass of the green color which
filters that light intercepts the red rays emitted by the model and contrarily lets
pass the rays which range from the green, the blue, and the yellow, it results that.
the negative in question translates the red surfaces of the model by white, and
gives the black for the surfaces green, blue, or yellow, that the red preparation of
the monochrome given by this negative will translate the reds of the model by
red, and by a red as much more intense as the red of the model shall be more
pure; that lastly, this same red preparation will be eliminated under the blacks of
the negative, that is to say, in the parts of the above-mentioned monochrome
which correspond to the surfaces green, blue, and yellow, and that this elimination
will be as much pronounced as these divers colors differ farther from the red.
An analogous reasoning will apply to each of the two other monochromes; they
will contain the one and the other a faithful repetition of the color, whether
simple or mixed, that they are intended to represent
The superposition of the three monochromes adapted mechanically the one to
the other and placed on a white ground produce the composition the polychromatic
image desired.
It happens in effect that on the white ground the transparent colors of the three
monochromes in mixing together two and two in divers proportions give rise to the
binary colors, that is to say, oranges, greens, and violets, and all these, by mixing"
themselves in divers proportions, partially extinguish themselves and give rise to
shades, that is to say, grey deep colors, browns, and black, whilst the white arises
from the simple absence of the coloring matter on each of the three monochromes.
The known processes of photographic printing in color of which I have spoken
as applicable to the three monochromes are no other than the colored bichromated
gelatine, and all methods similar or derived from it, such as the photoglyptic
(Woodbury), the impressions in fatty inks, the photo-lithography, photographic
enamels, &c.; there are also the printed proofs founded on the use of perchloride of
iron in place of bichromates, etc.
The three monochromes may also be obtained chemically; for example, by means
of three sorts of transparent coloring (virage) (toning) laid upon three proofs made
with the salts of silver.
I have employed purposely the expressions green light, orange light, violet light,
substituting them for the designation that I used at first for the three sorts of
colored glass, by the interposition of which I have up to this time produced these
three lights.
In effect the employment of three colored mediums, of three glasses for example,
has nothing absolute, nothing which ought necessarily to enter into the definitions
of the system, and one may imagine that by the effect of certain preparations
exclusively sensible to such or such group of the rays of the spectrum the printed
surface might be able (without the assistance of any middle color intercepting the
other rays) to receive the same impressions that it would receive with the inter-
position either of a green colored glass, or an orange glass, or a violet glass. That
possibility is at present changed into certitude, as I shall establish in the course of
this memoir, for those of the three sensible surfaces which correspond to the violet

page_text: glass, the greater part of the photographic preparations that it allows of gives the
same prints whether we maintain or suppress this glass, the same rays exerting this
action in the two cases to the exclusion of all the other rays.
To sum up chromo-photography such as I have imagined it, and such as I
propose, may be defined the act of transfering separately by three images, the one
red, the other blue, the other yellow, the image of the camera by means of the
decomposition of the light in three lights, of which each offers the complementary
color of that of the image of which it furnishes the imprint, and to blend together
afterwards these three monochrome pictures in one single picture, which is no other
than the complete polychromatic representation of the model. This decomposition,
this sifting of the light, is physical or chemical; physical when it is obtained by
the employment of colored mediums (colored glasses, including the prism, etc.),
chemically if it is produced by means of photographic preparations uniquely
impressionable to the colors of such or such portion of the spectrum to the exclusion
of the other colors.
As to defining for its practical operation the course of the manipulations one may
say that they consist in,-
Firstly. In producing in the camera three clichés (ordinarily three negatives) of
the same subject, one by green light, the second by orange light, the third by
violet light.
Secondly. In obtaining photographically a red positive image by making use of
the first clichés, a positive blue image in making use of the second, and a yellow
positive image in making use of the third.
Thirdly. In superposing the three transparent images, the one on the other, and
in blending them mechanically into one single image.
I affirm that this system is the solution at once scientific, artistic, and industrial
of the problem of photography in colors.
Scientific. For it is certain that if a palette of three colors always the same
reproduces with an equal fidelity all the subjects in color whatever they may be,
one cannot qualify as arbitrary the choice of these three colors, whether this choice
results from the rigourous laws of science or from simple experiment it matters
little in the two cases, it justifies itself by the results, where one ought to see the
brilliant manifestation of an optical law and of a law of the first order.
Artistic. For the simplicity of the palette explains the inimitable harmony,
vigour, and softness, in one word the artistic beauty of the heliochromic pictures
due to the system if they are only a moderate success. The same pencil which is
used so largely for transferring what is called the total effect sharpens itself and
draws out into a point more sharp than the graved to copy scrupulously the par-
ticular shade of the most imperceptible detail. It has in the infinitely little an
exactitude, an incomparable loyalty, which takes nothing of its fulness for the
work of the master.
Industrial. For the celebrated works of M.M. Edmond Becquerel, Niepce de
St. Victor, and Poitevin have proved that a plate prepared with a sub-chloride of
silver is susceptible to the greater part of the colors of the image formed in the
camera, and that it retains that impression but always shaded from the light of day.
Admitting that we could achieve the fixing the heliochromes thus obtained do not
respond sufficiently to the exigencies of our present industries, accustomed to the
prodigies of the press and to the indefinite multiplication of a work of art, they
require in effect as many exposures in the camera as the number of proofs of the
same subject that would be required. Our heliochromes on the contrary are
obtained from moulds or clichés created once for all; that is to say, they lend
themselves to unlimited copies, which is actually the condition of all graphic arts.
As to the necessity of a triple printing for each proof, that is only a small embarras-
ment; in the actual state of the plant it is not three printings which are required
for a chromo-lithographic print richly shaded, but twenty, twenty-five, and even
more.
I have given the general description of the system. I will now describe the

page_text: practical means I have employed, and which are very subsiduary if we compare
them to the system itself, and also admit for the most part of numerous variations.
2. Production of Three Heliochromic Negatives on Glass:-
Operations. At the time when I essayed for the first time to put in practice this
system photography knew but one sort of negatives, those which are obtained with
the white light, and it might have appeared foolhardy and even absurd to found, as
I did it, the photographing of colours on the employment of three negatives, of
which one should be the work of green light and another the work of orange light,
practitioners holding generally for certain that neither one nor the other of these
two lights would be able to give a proof in the camera. The result of this attempt,
hazardous as it might appear, responded to my expectation. I did realize, without
much experiment, the three impressions wished; they were negatives on paper,
with bromide and iodide of silver formed by the light only, that is to say without
recourse to the processes of development, and that I led by intensifying to the in-
tensity wished when the silver salt had been dissolved by the fixing agent. I will
explain further on why at this primitive period of my work I had renounced the
usual method which consists in developing the latent image. The method that I
followed offered amongst other inconveniences that of an excessive duration of the
exposure, and out of all comparison with the exposures known. To get rid of this
inconvenience I imagined a process which consisted in contenting oneself with an
impression on glass, produced, as said, by the light only, and scarcely visible, ob-
tained consequently with an exposure very much diminished, then to draw from
that impression a proof of suitable strength, either by means of a single counter
type, giving by contact the image of a single jet, or by means of a regular succes-
sion of counter types, always by contact and of a progressive intensity. It is thus
that a layer of gelatine on glass, sensitised with perchloride of iron, exposed and
treated notably by gallic acid, gave me at once, placed in contact with a negative-
nearly invisible on coming from the camera, a negative countertype, of which the
energic intensity, according to a law of optics conformable to my suppositions was
just proportional to the thickness of the layer, and thus allowed the regulations of
the strength of this new species of development. As to the successive countertypes,
they were furnished to me by those preparations of gelatine, with salts of silver, of
uranium, etc., which create by light only effects of contrast, of which the
progress is watched in the same manner as we watch the process of ordinary posi-
tives (example-a mixture of albumen and gelatine spread upon glass and treated in
a bath of silver, with acetate of lead added). If I thus enter into several details
upon a process which has cost me years of research, it is that even to-day under
certain circumstances which have become, it is true, exceptional, it might still render
soine assistance for the heliochromic negatives.
The long study which I have made of the countertypes of which I speak did not
prevent me from accomplishing other works in view of a solution less complicated
of this difficulty; they were not barren. I had the satisfaction of proving notably :
First. That a collodionized glass of iodide or bromide of silver, freed by washing of
its excess of nitrate of silver, and exposed dry to antiphotogenic light, gives by de-
velopment, after a tolerable exposure, an intense image, whilst exposed wet it would
not give an image except with white light. Secondly. That by means of an addition
of resin to the collodion the glass exposed even wet to antiphotogenic light gives by
development an intense image after an exposure not very excessive; I, nevertheless,
recognised that these results could only be obtained by observing rigourously the two
following precautions:-1st. If we proceed by the wet method not to rely to keep
the humidity of the glass by adding a hygrometric substance, such as a mixture of
albumen and glycerine, which would render the glass absolutely insensible to anti- .
photogenic light. 2ndly. Only to use distilled water for the washings, even for the
last washing, the least traces of calcareous salt being sufficient to destroy the
sensibility of the glass to green light or to orange light, whilst it is not sufficient to
modify in an appreciable manner its sensibility to white light.
From not knowing at the commencement of my experience the necessity of these
.

page_text: proportion is 2 decigrammes of aurine for 100 centimetres cube of collodion, the
glass after sensitising in the above silver bath is washed in distilled water, then
exposed wet in the camera. I then leave it a few minuites in a bath of alcohol to
free it from the aurine, the presence of which would only be an incumbrance
during the succeeding operations. After the aurine is washed out I immerse the
glass for some minutes in a bath of pure water, and proceed to the development,
the exposure to the sun for this negative, the slowest of the three, will be from 10
to 15 seconds with a double lens and with a landscape lens (triplet aplanatic globe
lens, etc.), it varies from one minute to ten according to the opening of the lens and
of the diaphragm employed.
The washing of the glass after sensitising should be done as I have said with
distilled water, with the use of aurine in the collodion, the least residue of
calcareous salt suffices to destroy the sensibility of the glass to the green light
according to the proofs above stated.
In principle chemically pure water is indispensible; there is nevertheless a way.
of utilizing water for washing even if slightly calcareous; it consists in leaving a
slight excess of nitrate of silver in the sensitive layer in place of completely.
washing it, to expose it to the light in that state and not complete the washing
with the imperfect water at hand till after the glass shall have received the action:
of the light. The development which follows the washing will bring out a suitable
image.
,
The properties of aurine or orange coraline had been pointed out to me by a:
publication of M. Vogel; I will point out in my turn the sandragon amongst the
substances indicated M. Chautard (in his treatise on the spectra of chlorophyle) as.
giving large rays in green part of the spectra. I have notably experimented
with the leaves of the red beetroot, the sensitive plate impregnated with an alcoholic.
solution of the said leaves, according to the method which will be hereafter described
for using chlorophyle, has given me rapid impressions with the green light. This
is only a first point ascertained; should not dare to guarantee complete regularity,
of the results.
Eosine originating from the laboratory of Professor Bayer, of Strasbourg, gives.
apparently to collodion the sensibility of the green rays.
Negative for the Orange Light.-To make thep late which corresponds to this glass
sensitive to the light transmitted by the orange glass I do not use either the.
collodion with aurine but with an alcoholic infusion of chlophyle, the preparation
of which will be described below, and I proceed in the manner following:-I
collodionize and sensitise the plate with the collodion and the silver bath common
to the three negatives. I wash it in distilled water to free it from the excess of
nitrate of silver, then immerse it in a bath of rectified alcohol so as to substitute
this alcohol for the water which the layer has retained, and the better to ensure
the penetration of this layer by the solution of chlorophyle I leave it a few minutes
I drain it a few
in the solution in question, which gives it a light green tint.
I maintain
seconds only and immerse it immediately in a bath of distilled water.
it there long enough for the water to replace the alcohol in the layer of collodion.
The layer will retain the chlorophyle which is in effect insoluble in the water.
The time of this last immersion is reduced to about a minute if care is taken to
agitate the plate by the aid of a hook; once drained the plate is ready for exposure
in the camera.
The exposure will be about a quarter of that which the aurine
plate requires.
I obtain by a very simple means the alcoholic solution of chlorophyle. I fill a flask
with the fresh gathered leaves of the ivy cut into small pieces with scissors. I put
in rectified alcohol 40°, so as to cover the ivy, and leave it to infuse. At the end
of 3 or 4 days the beautiful green shade which the liquid acquires little by little
will have acquired its intensity, and the solution will have arrived at its maximum
photogenic power. It only requires then to be filtered through paper, and kept
shaded from the light. It will keep good during 15 days or a month, according to
the season. At the end of this time it will change to a dirty yellowish green, which

page_text: is the indication that its properties are weakened. A glass thus prepared with
chlorophyle is only good for the negative with the orange light. It is not for the
negative with the green light; it is the red and orange rays which form upon it in
more or less time their impression, notwithstanding the green medium interposed.
Negative of the Violet Light.-The collodion, the silver bath, and the developer,
are the same, as I have already said; as for the other two negatives, the only change
consists in suppressing the aurine and the chlorophyle, and the operations with
respect to them. The aurine would lengthen greatly the exposure.
The exposure
is scarely more with interposed violet glass than if the operation was with white
light.
The three sorts of plates of which I have made known the preparation may the
one and the other be kept in the moist state several hours. It is sufficient to keep
them in the last bath in which each of them is treated; therefore the first thing in
the morning we may prepare the plates required during the day for taking land-
scapes or portraits after nature; it is a notable simplification in the practice of the
wet method. If required for landscapes, they may be kept in grooved boxes for the
place where the operations are required.
If the negatives once treated by the alkaline development and once fixed have
not sufficient vigour, I give it them whilst they are still wet by reintensifying with
pyrogallic acid and nitrate of silver. In the case where they are once dry and they
offer feeble differences of intensity, there is no inconvenience in equalizing them by.
a light supplementary intensification.
To free the chlorophyle negative of a green tint which has been given to it,
after it is dry I immerse it in a bath of ordinary alcohol; if wet at the moment of
being submerged, the layer will not be freed from the chlorophyle except with
difficulty.
Of the three surfaces of which I have spoken there are two of a sensibility excep-
tional to the smallest photogenic rays; hence it is evident that the anti-photogenic
coloured glass which is used for lighting the laboratory should be very deep shaded,
and reduced to as small dimensions as possible; besides, during the time the plates
are in the baths care should be taken to cover the dishes with a board or a sheet of
cardboard.
To ensure during the whole course of the operations the solid adherence of the
layers of collodion to the prepared plates, as described, it is sufficient to roughen the
borders of the plates about a centimetre wide.
Chlorophyle being a reducer of salts of silver explains why I have not introduced
it into the collodion itself as I did with the aurine. The contact of chlorophyle with
the silver bath will give clouded proofs (fogged).
Dry Method. The dry method gives the three negatives without the help of any
accelerating substances, such as resin, rosin, aurine, chlorophyle, absolutely required in
what relates to two of the negatives by the wet method. I have already said in effect
that the dry plates with a precaution relative to their washing are by themselves
sensitive to the green light and the orange light, as also to all the rays of the
slightly refrangible portion of the spectrum. The details into which I have entered
on this matter are sufficient for the employment of this method, more slow, but in
certain cases more convenient, than the wet method. The bromide collodion, the
bath of silver, and the alkaline developer, of which I have previously given the
formulæ, may be used. The time of exposure may be shortened by making use of
collodion prepared with that variety of gun cotton called intense or powdery cotton.
Special Cameras.-We may use, and I have myself used, a camera with 3 lenses
acting simultaneously. The advantage of this apparatus, that is to say, the simul-
taneousness of the three luminous impressions exists only for subjects susceptible of
modifying themselves during an exposure rather prolonged, for example, for land-
scapes in which the effects of the light are changing. It is necessary to realize
exactly that simultaneousness that the three lenses should be opened and shut at
the same time, which is only possible by putting in inequal diaphragms, and
according to the degree of activity of the luminous impressions upon each of the three

page_text: sensible surfaces. The diaphragms which I used were formed of two slits disposed
as a cross, so that I simply weakened the lighting. It is the effect of this kind of
diaphragm, different to the circular diaphragm, which determines an equal lighting
on all parts of the image, leaving on the proof where used the degradation of the
light presented on the borders of the image formed by the lens without diaphragm,
or slightly diaphragmed. The triple-camera of which I have spoken can only be
used properly when the model is placed at a certain distance, or else being nearer it
has no relief. Outside of these two cases, stereoscopic differences are produced from
one proof to the other, and they would prevent the outlines of all the objects coin-
ciding in the ultimate superposition of the monochromes, consequently the three
lenses ought to be in principle as close together as possible, which compels us
generally to be contented with proofs of reduced size.
I will indicate in a supplementary prortion of this memoir the principles upon
which a triplicate camera should be constructed, furnishing at once a simultaneous-
ness of the three exposures, lineal identity of the three proofs, and the power of
giving to them any dimension whatever.
I hasten to say, as much as it is required to seek simultaneousness in the proofs
when two of the negatives require considerable exposure, so much it becomes of
secondary importance in proportion that the negative of the green light and that
of the orange light are obtained more rapidly. What matter if the three negatives
of a heliochromic portrait are taken successively and with a single lens if three
additional operations do not notably exceed the time of an ordinary exposure? That
is the reason, whilst indicating the apparatus as I have done, which allows, if
necessary, the simultaneousness of the three luminous impressions, why I have
adopted and I propose principally the employment of a camera with one lens
provided either with a multiplicating slide, which will give successively the three
proofs or three identical slides, of which each contains one of the three sensitive
plates, and which act simply in substituting one for the other without loss of
time.
4. Mounting of the Coloured Glasses in the Photographic Apparatus.-There are
two ways of fixing the coloured glasses; they may be of the size of the sensitive
plates, and then they must be mounted in special grooves in each of the three
frames, and which should leave between each sensitive plate and the coloured glass.
with which it is assorted a space of about two millimetres, or the coloured glasses,
are reduced to the dimension and the circular form of the lens, and then each of
them must be mounted in a ring of metal which is enclosed freely in the part of
the tube of the lens between the lens and the outward extremity of the tube.
In the first of these two methods of mounting the place occupied by the inter-
posed coloured glass slightly changes the focus; it is therefore necessary that the
same change takes place on the focussing glass used for focussing. With this
object I adapt a frame carrier of the focussing glass, and in contact or nearly in
contact with the focussing glass an uncoloured glass of a thickness equal to that of.
the colored glass, adapted to each of the slides in question, which will occupy the
place of this slide. It need not be said that the coloured glasses should not differ in
thickness. The interval of about two millimetres between the coloured glass and
the sensitive surface is moreover excellent for maintaining the plate humid in
summer without the aid of hydroscopic preservatives, of which I have indicated.
the inconveniences. The advantage is so valuable that if the second mode of.
mounting the coloured glasses by placing them on the exterior end of the tube of
the lens is adopted as I have done I advise the adoption to each of the slides
(always in proximity to the sensitive surface) not a coloured glass, but. an
uncoloured glass, intended only to maintain in hot weather the humidity of the
layer of collodion.
In respect of the second mode of mounting I have only one remark to make at
present; it is this; that the place above indicated for the round coloured glasses is.
the only one suitable; we must be careful to avoid placing them in the part of the.
lens turned towards the sensitive plate; -

page_text: 5. Manufacture of Three Sorts of Glass or Coloured Mediums.-It is almost
impossible in the best stocked warehouses of coloured glass to find my three kinds
of heliochromic glass uniting to the advantage of the exact shade of colour,
exemption from defects, such as bubbles, striæ, etc.; that is why I have been led
to seek and I have found another means to produce the three coloured mediums. I
employ coloured varnish spread on the glass, and which I am able to detach if
required in the form of a pellicle.
The aniline colours dissolved in the white varnish of the house of Sohnée (Paris,
Rue de Filles du Calvaire, 17), designated by the letter A, and a portion of the
coloured varnishes ready prepared and furnished by that house are susceptible of
mixing with each other, and of giving a great variety of shades of perfect trans-
parency. To obtain upon glass a regular layer of one of these varnishes it is good
to cover it first with a layer of normal collodion prepared in this way:- -Heat
moderately, and apply it in the same way as the collodion; the coloured varnish,
if necessary, made fluid as required by the addition of a little alcohol. Once the
excess of liquid has altogether drained off, and before the layer has had time to
cloud, the glass is moved to and fro at a certain height above, over a warmer,
holding it perfectly horizontal, the coloured side upwards; thus dried the layer
becomes completely transparent. If the colour obtained in this way has not the
necessary intensity, or if it is desired to modify the shade by the superposition of
another varnish, one must be careful not to put the second layer direct upon the
first, as this latter would be in part taken off. Once the first layer is well con-
solidated we spread a moderately warm solution of gelatine (10%) like collodion,
pouring off the excess, and letting the plate dry vertically. There remains only an
imperceptible thickness of gelatine, which drys very quickly, and on which may be
poured without accident the second layer of varnish; thus, alternately gelatine and
varnish, as many layers may be superposed as may be desired, taking care to
change the dripping corners of the plates."
In place of the glasses coloured by means of the above process we may reduce the
coloured medium to the state of a simple pellicle. For that purpose we must first
wax the glass, then spread the layer of collodion, then a layer of gelatine; treat this
latter with a bath of alum, then with a bath of rain water, and, lastly, establish the
alternate layers of varnish and gelatine. The whole will separate easily from the
glass in the state of a pellicle when the edges are loosened with a knife.
I have no special explanation to make in the case where the coloured medium
consists in a glass of the dimension of the sensitive surface placed in proximity to
it; but if the system of coloured circular pieces is adopted I ought to give warning
that simple glasses will not be sufficient, the image becomes troubled by the defect
of the plane of the surfaces, glasses only will serve. Besides as the layer of
coloured varnish however carefully applied presents frequently lumps and undula-
tions which might disturb more or less the image, I have conceived the following
arrangement procure two glasses, and if possible two glasses with faces
rigourously parallel, I spread the coloured varnish on one of the faces of one of
them or on one of the faces of both of them as one or two layers are necessary; then
I shape the said glasses into discs; and, lastly, I cement them together, these two
discs, with Canada balsam imprisoning in this cement the layer or the two layers of
coloured varnish. In this way the undulations and the streaks of the varnish are
overcome; the whole is like a disc of crystal perfectly homogeneous; I can thus
utilize the coloured glass of commerce, that is to say, by fixing it with the Canada
balsam between two glasses the whole being cut into rounds or discs.
6. The exact shades of the three glasses or coloured mediums:-.
(1.) Shade of the Green Coloured Glass.-It should be such that the yellow
objects, the green and the blue objects above all the yellow objects, are impressed
strongly upon the negative. If the yellow objects do not give a strong impression,
the red monochrome which corresponds to this negative will contain in the
corresponding parts a quantity of red, which even mediocre will make the yellow
pass to orange in the superposition of the monochromes, whilst a notable quantity

page_text: of red coming from a poor impression from blue objects will not alter the blue in
the superposition in question, in other words it requires less red to alter the yellow
than to alter the blue; a shade of green which responds to the position thus
defined may be obtained by a mixture of varnish called maize yellow and of a little
Metternich green. In place of mixing the two varnishes they may be spread in
two distinct layers, either superposed on the one and the other on the same side of
a glass, or poured upon the two faces of the glass, or, if the discs are used, on the two
faces which are cemented one against the other. Bromide collodion with aurine.
having by itself, that is to say, without interposition of the green medium a
sensibility nearly equal for the yellow, and for the blue, but on the contrary much
less sensibility for the green, it results that the shade of the green medium need
not be very intense, nor very precise to give the desired results, and that even in a
certain number of cases, for example, in a portrait after nature where the green
colour will not be represented, the green medium may be suppressed with impunity,
care must be taken then to increase the quantity of aurine.
(2.) Shade of the Orange Glass.-It should be such that the red objects, the orange
and the yellow, imprint strongly on the negative; the employment of chlorophyle
gives tolerable latitude for the shades in question; it may vary between the red and
the yellow without producing in the impressions proportional changes; the margin
left thus to the operator is necessary because all the red objects or orange or yellow
in nature emit abundantly the rays, which correspond to the characteristic band of
chlorophyle (which band is situated at the limit of the red and the orange), and on
the other part a transparent coloured medium, which varies from red to yellow,
allows passage for that very reason in great abundance, all the rays in question in
such a way that one may say the orange glass in parallel case has no other use than to
intercept the rays the most photogenic, to stop in other words the blue and the
violet objects from making their impressions; I obtain a very suitable orange shade
by means of two layers of varnish, the one maize yellow, the other cochineil rose.
The mixture of these two varnishes does not give as beautiful a color as their
optical superposition.
(3.) Shade of the Violet Glass; Suppression of this Glass.-The shade of the violet
medium should be such that the blue objects and the violet objects print strongly,.
which takes place if we use a blue glass violet shade, or simply violet, the,
impressions in the two cases are the same on the wet bromide of silver, because
these two glasses allow the actinic rays in either case to pass in great abundance.
It will be asked why I have said nothing about printing red objects; should not
their impression be also strongly marked, and should not there made use of a violet
glass drawing on the red? I will reply that that strong impression would be too
much; in effect on one part the impression, little or not pronounced, of red objects
on the violet glass negative has no other result than to produce in the corresponding
parts of the yellow monochrome an abundance of yellow, which by placing itself
under the carmine in the superposition of the monochromes increases it from a
slight violet tint to a veritable red; on the other part, if we use a violet red glass,
not only the red suffers impurity of tone, but the yellows of nature being of a yellow
very compounded, which contains the red, will do evil in respect to the impression
due to the red which they emit, and would be in consequence represented by a
much too bright a yellow on the yellow monochrome, and consequently on the
heliochrome I obtain a violet glass of a suitable shade by a mixture of blue varnish
and rose cochiueil varnish. As the actinic rays, that is to say, the rays which act
alone, or nearly alone, by white light on the wet bromide of silver, are precisely
those which this glass lets pass in very great abundance; it is easy to understand
that for the heliochromic negative in question one may without inconvenience, if it
is prepared in this manner, suppress the violet glass, that is what I have done in
the last, without any appreciable modification being produced in the impressions.
7. Printing and Superposition of the Monochromes.-In the present state of
photography there are numerous ways of producing positive proofs, either red,
yellow, o blue, endowed with transparency; we bave only to utilize the methods

page_text: in question to form, by the intervention of my three heliochromic clichés, the three
monochromes constituting one heliochrome, and to superpose these three mono-
chromes.
Amongst these methods I have already mentioned the gelatine with bichromate,
with perchloride of iron, etc., photoglyptic impressions in fatty inks, printing used
for vitrification, or photographic enamels, etc.
I should evidently exceed the reasonable limits of this paper if I gave in detail
.each of these methods in their application to heliochromy, the more so that they
subdivide into a great number of particular processes, for the great part well known
under the names of their Inventors. I will limit myself then to show, as an
example, how the bichromated, gelatine, or carbon process, may be applied to helio-
chromy.
Swan, Leon, Vidal, etc., put in practice these kind of impressions by means easy
enough it appears to procure prints for the superposition of the three monochromes.
I will describe the equivalent series of operations by which I arrive to get at the
same result.
I obtain my three monochromes by making use of three sorts of paper, one
coloured with carmine, one with Prussian blue, and one with chrome yellow.
Manufacturers will furnish operators the three sorts of paper ready made.
The amateur who wishes to make them himself should proceed thus:-
(1.) Prepared Paper, Carmine.-Dissolve 5 grammes of carmine in 500 grainmes of
liquid ammonia, spread it out in a basin, leave the ammonia to evaporate in the open
air till its odour has nearly entirely disappeared, this requiring a certain number of
hours; add then rain water in sufficient quantity to compensate for evaporation of
the ammonia and to double the quantity originally, which will raise it to 1 litre ;
soak therein cold for about an hour about 150 grammes of gelatine very soluble
(gelatine grenetine for example), dissolve it in a water bath moderately heated, 50
to 60°, filter it through a flannel wetted firstly or in a funnel fitted with a very fine
wet sponge, retain the mixture in a basin kept tepid; throw into a graduated glass
the quantity of this liquid which will be necessary to cover the sheet of paper to
be prepared, say 25 centimetres cube for the dimensions, 18 centimetres by 24, and
lastly, empty the contents of the glass on the said sheet of paper previously applied
on a glass plate.
The application is made thus:- -The plate is kept at a sufficient temperature by
means of rain water heated by a warmer and contained in a deep tin dish; in this
dish the glass is submerged, and above the glass the sheet of paper, a border having
been previously turned up all round it the paper and the glass are lifted out, so
that the paper lays down close on the glass; the excess of water existing between
the paper and the glass is squeezed out by means of a strip of india-rubber, the
coloured mixture is thrown on to it, the plate held in the hands is slightly rocked,
and the layer is regulated by a glass triangle. It is allowed to cool horizontally on
a level plane; when the gelatine is set there only remains to detach the paper from
the glass and to leave it to dry, suspended by means of pins from the two
extremities of the same side, aided by a stove where the temperature would be too
low, that is to say, below 18 or 20° C. (the temperature of the stove ought not to
exceed 25°); if bubbles are produced on the paper when the mixture is poured on
we must conclude that the water in the bath is not hot enough for the mixture, the
bubbles cease directly the glass and paper are raised to a higher temperature. The
paper for this mixture, or for the two other kinds, to be hereafter mentioned, should
be resistant, fine grained, and not too much sized.
(2.) Paper with Prussian Blue.-A supply of blue fixed ink must be provided,
such as is to be found at stationers. In a litre of liquid formed with rain water
and from 100 to 150 centimetres cube of that ink (as it is more or less deep
coloured) soak cold, during about an hour, 150 grammes of the gelatine above
mentioned, then dissolve in the water bath, filter, and proceed exactly as beforesaid
for the red paper.
(3.) Paper mixed with Chrome Yellow.-Soak in a little water (15 to 20 centi- -

page_text: metres cube about), during 24 hours, 25 grammes (light chrome yellow) (water
colour), after having broken it, at the end of that time, make a paste of it in a
mortar, adding water little by little to make up a litre, and soak cold for an hour
about 150 grammes of the same gelatine, dissolve it in the water bath, etc., etc.
The papers, on which are spread the one or the other of these three mixtures,
should be of the same pulp and the same weight, in a word, of the same manufacture,
so that the baths and the dryings which they undergo to form the three mono-
chromes of the same subject shall not produce appreciable inequalities in their
respective dimensions. Up to this time I have sensitised these three papers in a
very concentrated bath of the double bichromate of potash and ammonia. I con-
centrate it more if the clichés are less soft, or if the gelatine of the prepared paper
is more charged with colour; this increased charge of bichromate is not only to
increase the sensibility of the paper, but also to furnish images but slightly
intensified; one will understand that the polychromatic image in question to be
obtained is formed by three superposed proofs; each of them should be much less
vigourous than would suffice for the single proof in itself.
To make the double bichromate of potash and ammonia I dissolve in rain water
the bichromate of potash, and I add to it liquid ammonia very gradually, constantly
agitating the mixture up to a certain moment, when the deep yellow colour of the
liquid passes almost in an instant to a much lighter yellow. According to circum-
stances I vary the strength of this solution of from 12 to 20 %. As the bichromate
of potash uncombined with the ammonia does not dissolve byond 10 ° it is by
progressive quantities, and alternately, that I introduce into the water the pul-
verized bichromate and the ammonia. To be certain that all the bichromate of
potash is combined with the ammonia, I still add a very small quantity of the
latter. The feeble excess is recognized by its slight odour in hot and dry weather.
It would be useful to add to the bath some sugar varying from 20 to 50 grammes
per litre. I float these papers on the sensitive bath for about 5 minutes, the time
of floating varying with the temperature of the place where operated upon, the
gelatine absorbing more liquid in a given time in proportion to the elevation of the
temperature.
When the bichromate bath has been very concentrated its dessication tends to
cause crystallization on the layer of gelatine; this is avoided by heating the stove
to its maximum, that is, 25 to 26° C.; a higher temperature would cause the gelatine
to run.
After drying, and after exposure to light under the cliché, the prepared paper is
immersed with the layer of gelatine downwards in a basin of cold water, in the
bottom of which is previously placed a glass covered with a slight layer of ox gall.
The paper and the glass are lifted out together, the gelatine side of the paper
applied against the face of the glass coated with the gall; they drain for a few
moments, then the glass being placed on a horizontal surface the excess of water is
driven out by the friction of the hand, several sheets of blotting paper being interposed.
5 or 10 minutes after this adaptation, the adherence being complete, the glass and
paper united are immersed in a horizontal dish of moderately hot water; the
paper soon detaches itself, and the image is apparant adhering to the glass.
The layer of ox gall may be obtained by spreading upon the glass like collodion a
filtered solution of 80 parts by volume of alcohol at 40° with 16 parts of ox gall; it
is dried at the fire..
The red, blue, and yellow monochronies being thus obtained on their three
respective glasses, the question is to transport them successively to the same sheet
of paper; this is how I proceed-In a bath of cold water, which is contained in a
horizontal dish, I immerse the glass with the yellow monochrome, then a paper
strongly gelatined, the gelatine downwards. After imbibing a few minutes, and
when the edges of the paper commence to curl, I take out of the water the mono-
chrome on glass, and the paper applied thereto. I maintain in contact by the
pressure of the finger the edge of the paper, and the corresponding edge of the
glass that I have withdrawn first, so that the paper falls of itself on the monochrome

page_text: gradually. As the whole is taken out of the dish, I let it drain; I place it
level; I leave the adherence to establish itself alone. This takes place at the end
of two or three minutes; then I lightly rub it with blotting paper interposed, and
leave it to dry in a temperature, natural or artificial, of 25 to 30°.
.
When the drying is complete the paper separates itself from the glass, taking
with it the yellow monochrome. If this does not occur spontaneously, it may be
produced by loosening the edges of the paper with a knife, or by slightly warming
the glass. To adapt to this yellow monochrome the blue monochrome, I immerse
in the same basin of cold water the glass carrying the blue monochrome, then the
paper carrying the yellow monochrome with the yellow image downwards. After
imbibing for a few minutes, I take them from the liquid applied, the one against the
other, conformably to what I have already said.
To effect the coincidence of the outlines of the objects represented on one and the
other monochrome, I slide the blue on the yellow till the coincidence becomes
perfect, an easy operation for him who takes care to notice the traverse of the light
in interposing the thickness of the glass between him and the double image given
by the glass and the support. (To favour this manipulation, take the precaution to
cut the gelatine paper a little less than the glass.) The superposition thus estab-
lished, the adherence of the two monochromes is soon produced. One can then
with impunity absorb the excess of humidity by blotting paper. It is left to dry
as before, and the double image separates from the glass.
Following the same method the third and last superposition is made, that of the
gelatine paper carrying the double image, the blue and yellow monochrome with
the rod one still on the glass; and, lastly, the complete heliochrome will be separated
from the glass itself.
The indefinite duration of the proofs may be assured by aluming. Besides,
their surface may be varnished with picture varnish, care being taken to dilute the
said varnish with spirit.
The gelatine paper, which supports definitely the monochrome, should be strongly
gelatinized, so that the reliefs of the three superposed images may be well embedded
therein. I employ for that purpose ordinary gelatine called blanc-manger. The
strength of the solution is 100 grammes to a litre of water. I cover the paper
with this liquid at the rate of about 25 centimetres cube for a full size photo-
graphic glass.
There are exceptional cases where ox gall fails to give a perfect adherence of the
monochrome to the glass during the peeling. This want of adherence may manifest
itself by a simple clot, etc. This depends on the nature or degree of the preservation
of the gelatine employed in the prepared papers. When similar accidents happen
the employment of wax in place of gall is a sure remedy, only this application should
be completed by that of collodion, and the operations become more complicated.
The glass must, first, be waxed (the layer of wax obtained by pouring in places
on the glass a solution of wax and ether, which is spread out with a flannel dabber
or pad); 2nd, collodionize the prepared paper after exposure to light (with this
object the paper is put upon a glass, first raising the edges to form a raised border,
and cover it with a layer of normal collodion, 5 decigrammes of cotton for 100
centimetres cube of collodion); 3rd, gradually, as each of three monochromes trans-
ferred on the permanent paper support has dried thereon, immerse the image in a
vertical tin bath containing ether and alcohol, where the collodion having become
an encumbering, substance dissolves, carrying with it all traces of the wax with which
it is covered; these traces would otherwise separate the monochromes, the one from
the other; lastly, in place of ox gall and wax the layer may consist of talc, gum,
damar, etc., many other means may be employed.
The method of printing which has been described applies not only to helio-
chromes on paper, but also to heliochromes on glass (heliochromic windows). It
suffices after having made the heliochrome on paper to immerse the proof in the bath
of cold water, to withdraw it attached to a glass previously covered with albumen
coagulated with alcohol, to let it dry; in that state then to plunge it altogether into

page_text: warm water, which by impregnating through the paper will dissolve the soluble
gelatine cover of the former, and consequently detach the paper, leaving the helio-
chrome adhering to the glass. It need not be said that the proof must not be
alumed, and that if the wax and collodion process is used the layer of collodion,
which covers the third and last monochrome, should have been dissolved like the
two others before applying the heliochrome to the glass.
It will be understood that this system of superposition of monochromes can be
combined with the photoglyptic process (Woodbury process) were it merely by
printing the three monochromes formed in gelatinous inks on three provisional
paper supports coated first with a varnish insoluble in water but soluble in alcohol,
benzine essences, etc.; for example, gum lac, benzoin, gum damar, Canada balsam.
After each adaptation of the monochrome to the permanent support the provisional
paper support is taken away by dissolving the varnish.
8. Applications and Improvements.-As to its applications it would be puerile to
undertake to name them. The solution of the problem of photography in colours
responds to a universal desire. Chromo-photography that I propose is able to
re-produce on paper, on hangings, on glass, on porcelain, etc., pictures, collections of
objects of art and natural history, flowers, landscapes, and lastly, thanks to recent
accelerations, the human face; whilst rendering to science services of the first order
it is serviceable to decorate our dwellings with inappreciable artistic riches, and to
disseminate them on the least object of every day use, even such things as paper
weights.
Notwithstanding the fundamental principle of the triple proofs there may be
circumstances where a fourth negative, a fourth monochrome, would constitute a
real progress. If it be desired to reproduce a landscape where there are moveable
objects in their detail, or objects which glisten with exceptional brilliancy, for
example, running water, a cascade, a sky studded with clouds, it would be advan-
tageous to obtain with a white light a fourth negative, an instantaneous negative,
under which should be formed a fourth monochrome, a black monochrome or of a
shade approaching black, destined to be superposed on the other monochromes. It
will be superposed thereto either entirely or partially by recourse in this last case
to reserves or opaque cuttings to mask the immoveable or relatively dark parts of
the picture. In this way the sensation and the charm of the reality are increased
to a remarkable degree.
9. Principles of Construction of a Triple Camera adapted to the System.-Simul-
taneousness and lineal identity of the proofs; supplementary correcting lens for
flattening the bent field, the curved field of the image, and to give sharpness to the
whole surface of the said proofs.
The
(1.) Camera. The rays coming from the subject to be reproduced are received
upon a glass unsilvered with parallel fases inclined 45°, or thereabouts, in respect
to the model and in respect to a first lens, towards which it reflects a part of the
above-mentioned rays. The greater part of these rays traverse this first glass, and
they are received by a second glass cqually unsilvered and with parallel faces also
inclined 45°, or thereabouts, in relation to the model and in relation to a second
lens towards which it partially reflects the rays which it receives. Lastly, the rays
that this second glass allows to pass are received by a third lens either direct or by:
interposing a silvered or metallized glass which reflects nearly all of them.
distance of this first glass to the first lens is equal or nearly equal (slight:
discrepancies do not appreciably alter the results) to the sum of the distances of the
first glass to the second, and of this latter to the second lens, and it will be equal
also to the sum of the distances of the first glass to the third lens (or if a third glass
is made use of it is equal to the sum of the distances of the first glass to the third-
glass plus that of that third glass to the third lens). In virtue of this arrangement
the three images received by the three lenses are geometrically the same.
their luminous intensities they will be very different, the image received by the
third lens will be much the most brilliant. This third lens is naturally designed:
to furnish the slowest of the proofs, whilst the two other proofs requiring less light
As to

page_text: will be furnished by the two first lenses; of these two other proofs the one A
requiring more light than the other, the proof B; this difference in excess in the
lighting necessary to the proof A will be obtained by an assemblage of two or more
unsilvered glasses superposed without being cemented together. To assure sub-
sidiarily the rigourous unity of the time of exposure of the three proofs simul-
taneously there only remains to diaphragm unequally the lenses. As the two first
lenses at least receive a reflected image, and consequently inverted, the corre-
sponding sensitive plates must be transposed in their frames, and to avoid all errors
of focus and refraction in focussing the focussing glass which will be of analogous
thickness to that of the sensitive plate must be equally transposed. A preferable
means to remedy the inversion of the images consists in the transfer of the three
negatives on to a pellicle of gelatine or collodion leather, the slight thickness of
which allows the printing of the positive proofs in one way or the other. We can
also use the method of countertypes taken in the camera. If it is a question of
reproducing by this described apparatus a very near object, for example, a small
picture, it will be necessary to remedy the imperfections of the outline of the
objects caused by the thickness of the glasses, which can be easily effected by
interposing between the said apparatus and the model a magnifying glass, having
the effect of placing the model further back. It need not be said that the glasses,
the tubes of the lenses, and the front parts of the cameras should be shaded from
diffused light, that the internal walls of this protecting shade should be blackened,
the tubes of the lenses covered with black velvet, etc. To avoid the necessity of
using large glasses, which would be very costly, the three cameras must be combined
together in such a manner that the three lenses are as close to one another as
possible. There are evidently many ways of varying this contsruction without
departing from the essential elements thereof, and which I have specified above.
(2nd.) Correcting Lense. The diaphragms fitted to the lenses of ordinary photo-
graphic apparatus are intended notably to remedy the want of sharpness that the
curving of the field of the lenses gives to the image in all the parts which are far
from the centre. The increase of the time of the exposure, the inevitable con-
sequence of using these diaphragms, is scarcely a grievance in ordinary photography,
the preparations used being so exceedingly sensitive to white light. But when it
is necessary to obtain proofs by green light or orange light the want of definition
arising from very narrow diaphragins would necessitate exposures far too long.
I have therefore been led to seek another means of giving clear definition over the
whole surface of the proofs. This method consists in interposing between the lens
and the sensitive surface, and very near to the latter, a concave glass having the
same dimensions and the same outline as the image. This lens, which produces
neither aberration, sphericity, nor astigmatation, as a lens giving by itself the plane
to the field of the image would do, has the effect if the concavity which it offers is
not exagerated to flatten the field in question, and if that concavity is well
calculated it will give to the field an absolute plane. The concave glass may be
with impunity simple in place of achromatic. As the curvature of the field
diminishes notably in proportion as the lens is brought further from the sensitive
surface it will be advisable if the objects to be reproduced are nearer than a land-
scape to have two or three sizes of these kinds of lenses. Care must be taken in
the preliminary operation of focussing to place the correcting lens to be used, or a
similar lens, before the focussing glass (always retaining the uncoloured glass to
which the coloured glass is to be substituted).
Having now described and particularly set forth the nature of the said Invention,
and the manner of carrying the same into effect, I would have it understood that
what I clain is,―
First. The production in a camera of differently toned monochramic negatives by
causing the rays producing the same, either on passage to the lens or from the lens
to the negative, to pass through different coloured media during the exposure, as
above described.
•
Second. The general arrangement and construction of the cameras described for

page_text: the purpose of producing simultaneously three differently toned monochromes under
the influence of different coloured media interposed, as above described.
Third. The two different methods specified for fixing the interposed coloured media
in the above mentioned or other cameras, as above described.
Fourth. The methods of manufacturing the coloured glasses or media, as above
described for the purposes set forth.
Fifth. The use and application of a correcting lens placed between the lens of the
camera and the negative for the purposes stated, as above described.
Sixth. The methods or processes specified for producing or printing from such
negatives photographic proofs in different monochromic colours, as above described.
Seventh. The methods specified of preparing, colouring, and sensitising papers for
producing the said proofs, as above described.
And, Eighth. The production of heliochromic pictures by the superposition of
monochromic transparent proofs of different colours for the purposes and in the
manner substantially as described.
In witness whereof, I, the said William Morgan-Brown, have hereunto set
my hand and seal, this Twenty-first day of July, in the year of our Lord
One thousand eight hundred and seventy-six.
WILLIAM MORGAN-BROWN. (L.S.)