Ix- PROVENENTS IN ÅDDARATTS FOR TAKING PHOTOGRAPHIC Picandre
Year: 1871

page_text: LETTERS PATENT to Benjamin Joseph Edwards, of The Grove,
Hackney, in the County of Middlesex, for the Invention of "Ix-
PROVENENTS IN ÅDDARATTS FOR TAKING PHOTOGRAPHIC Picandre”
PROVISIONAL SPECIFICATION left by the said Benjamin Joseph
Edwards at the Office of the Commissioners of Patents, with his
Petition, on the 8th March 1871.
I, BENJAMIN JOSEPH EDWARDS, of The Grove, Hackney, in the
County of Middlesex, do hereby declare the nature of the said Inven-
tion for "IMPROVEMENTS IN APPARATUS FOR TAKING PHOTOGRAPHIC PICTURES,"
to be as follows:-
This Invention relates especially to apparatus used for taking pho-
tographic pictures upon glass plates (which may be either flat or curved
upon their surfaces, the shape of the several parts of the apparatus being
made to correspond) by means of collodion rendered sensitive by means
of solutions of salts of silver and used in a wet state.

page_text: The object of the Invention is to enable the person preparing such
plates and taking such photographic pictures and developing them upon
the glass plates, to do so without the use of any dark chamber or
chamber illuminated by yellow light, and to take photographic pictures
upon plates sensitized by what is commonly known as the "wet"
process with greater convenience and with less weight of apparatins
than has heretofore been possible. In order to effect this object I take
a dark slide of the ordinary kind fitted to a photographic camera in the
usual way, but instead of the hinged back by which the sensitive glass
plate is usually inserted into it, I substitute a shutter sliding in grooves
or guides in a way similar to that in which the shutter in the dark slide
on the other side of the sensitive glass plate works for the purpose of
exposing the latter to light in the camera. And in order to sensitize
the glass plate by covering it with a solution of the proper salts of silver
after it has been coated with collodion in the usual way, I take a flat
dish (which I call a sensitizing dish) of suflicient size and depth and
formed of opaque glass, gutta percha, wood, or other suitable material,
and I place in this dish the plate with that side which has been covered
with collodion uppermost. And I form grooves, flanges, slides, or
fastenings upon the upper edges of this dish, which grooves, flanges,
slides, or fastenings are fitted to corresponding ones upon the back of
the dark slide first described, in such manner that when the dish and
the dark slide are temporarily attached by means of the grooves, flanges,
slides, or fastenings, they may be held firmly together without the
possibility of light passing between them. And at one side or end of
the dish as described I make a longitudinal slit or opening of the full
length or nearly so of such side or end and of sufficient depth to allow
the sensitizing fluid to flow readily through it. And 1 make the lower
edge of the slit or opening level or nearly level with the upper surfaco
of the glass plate which is lying in the dish; and outside the dish at
the end or side in which the slit or opening is made I make a trough or
reservoir, closed at the ends, but partly open at the top, and sufficiently
large to hold the solution of salt of silver necessary to sensitize the
collodion upon the glass plate in the dish, and outside the dish I make
a hanging screen or division slightly removed from the slit or opening
already described, the lower edge of this hanging screen or division being
below the level of the lower edge of the slit or opening, and being fixed
in such a position relative to the latter that when water or other fluid
is poured into the trough or reservoir, such fluid will flow readily under

page_text: the hanging screen and over the lower edge of the slit, and so over the
surface of the plate in the dish, whilst at the same time it is impossible
that any light can pass through the reservoir into the interior of the
dish. And I make the reservoir of such a size and shape (looking at it
in cross section) that there shall be no sharp edges in the bottom of its
interior, but that the water or other fluid shall flow smoothly and
readily in the required direction through the slit, and I make it of such
a capacity that when the dish containing the plate is inclined diagonally
the whole of the fluid shall pass from the interior of the dish through
the slit and into the trough or reservoir without the latter overflowing.
Sometimes I close the upper part of the trough or reservoir entirely
with the exception of one or more small openings through which the
sensitizing solution may be introduced or removed when necessary, or
through which air may be allowed to pass to enable the sensitizing
fluid to pass in or out of the reservoir, and I make suitable stoppers or
fastenings to these small openings.
And when it is wished that the sensitizing fluid shall remain per-
manently in the trough or reservoir, so as to be carried about in it,
instead of being removed or poured away, I leave no opening at the top
of the trough or reservoir, but I make a water-tight moveable partition
between it and the dish. For this purpose I make no hanging screen as
already described (which is unnecessary as no light can penetrate into
the interior of the sensitizing dish from the trough or reservoir which
is now closed) but I make an opening communicating directly between
the dish and reservoir, and I close this opening when requisite by means
of a moveable door of wood or other suitable material, one side of which
is covered with india-rubber. And I force this india-rubber against the
edges of the opening by means of a moveable bar, which fits into grooves
or guides in the sides of the interior of the dish behind the door, covered
with india-rubber when the latter is in its place. And I make a screw
or screws working through the moveable bar and having its point
pressing against the back of the moveable door covered with india-
rubber. In this way the india-rubber covering the moveable door is
forced against the edges of the opening described, when the sensitizing
fluid is in the trough or reservoir which then forms a water-tight cistern,
in which it may be carried about with safety. This arrangement may
be used independently of the other parts of this Invention.
By this
means I make the collodion upon the glass plate sensitive to light by

page_text: means of a solution of a salt of silver or other suitable salts, and when
the collodion is sufficiently sensitivo I return the solution into the
trough or reservoir, or pour it away. It is necessary next to remove
the sensitive plate from the dish to the interior of the dark slide (which
is attached to the upper edges of the dish as already described) without
allowing any light to reach it. In order to do this I form the whole or
part of the bottom of the flat dish of india-rubber or other opaque
flexible substance which is not injuriously acted upon by the solution of
salt of silver or other solution used, or I make a frame or support upon
which the plate rests in the flat dish, such frame or support being
connected with a handle which passes through a water-tight opening in
the bottom of the dish, and when it is desired to transfer the sensitized
plate from the dish to the dark slide, I first withdraw the sliding shutter
already described, which has been substituted for the hinged back
ordinarily used in the dark slide, and I press the sensitized plate into its
position in the dark slide, either by means of the hand of the operator
pressing its back with the intervention of the india-rubber or other
opaque flexible substance described, or by means of the frame or support
acted upon by the handle as described; or sometimes I invert the dark
slido and dish and allow the plate to fall into its place in the dark slide.
And sometimes I make a pneumatic plate holder in which the glass
plate is held upon a disc or piece of india-rubber or other flexible
material, which is partially withdrawn from the glass plate so as to
leave a partial vacuum between it and the glass plate, and I make the
disc or piece of india-rubber form a part of or be attached to the
flexible substance which forms the bottom or part of the bottom of
the sensitizing dish. And when requisite I attach the glass plate to the
disc of the pneumatic plate holder described, which I do by means of a
handle containing a spring or an elastic hollow sphere in the method
which is well known and practised, such handle being outside the
flexible bottom of the sensitizing dish, and I proceed to scusitize the
glass plate in the method already described. And when the glass plate
has been sensitized I introduce it by means of the handle into the dark
slide, and I then remove the handle by re-admitting the air between
the glass plate and the flexible disc of the pneumatic plate holder.
When the sensitized plate has been by any of these means introduced
into the dark slide, I close the sliding shutter behind it (to which I
sometimes attach a spring or support which presses against the back of
the sensitized plate when the shutter is closed) and I then remove the

page_text: dark slide containing the sensitized plate from the flat dish. The dark
slide may then be placed in any suitable photographic camera, and
exposed to light in the usual way, for the purpose of obtaining a
photographic picture upon it. When the plate has been sufficiently
exposed to light in the camera it becomes necessary to develope the
picture which has been formed upon it by pouring over it a proper
developing solution of which I use any suitable kind. In order to do
this I take another flat dish (which I call a developing dish) similar
or nearly similar in shape and size to the one already described, but
having the bottom or a part of the bottom made of glass or other
transparent substance of a colour which will only allow to pass through
it rays of yellow light or of such colored light as will not act injuriously
upon the sensitized plate, upon which the picture has been formed, and
in the upper part of the dish I form grooves, guides, or slides, in which a
plate or a frame carrying a plate of glass or other transparent substance,
similar in colour to that just described, slides or works. Upon the
upper edges of this dish I form grooves, flanges, slides, or fastenings,
similar to those upon the dish first described and corresponding to
those already described upon the back of the dark slide. And I then
temporarily attach the dark slide to the developing dish by means of
these grooves, flanges, slides, or fastenings, and I withdraw the plate or
frame carrying a plate which covers the upper part of the developing
dish as already described, and I then withdraw the shutter sliding in
grooves or guides at the back of the dark slide and allow the sensitized
plate to fall into the developing dish, with its sensitized surface upwards
upon which the picture has been formed, I then replace the plate or
frame carrying a plate of transparent coloured glass or other suitable
transparent substance as already described, which then forms a cover to
the developing dish, and I then detach the dark slide from the grooves,
flanges, slides, or fastenings, which hold it upon the developing dish.
I next proceed to develope the photographic picture by pouring a
suitable developing fluid into a trough or reservoir attached to or
forming part of one side or end of the developing dish and similar to
that already described in the sensitizing dish, but open or partially open
at the top, and by tilting or inclining the developing dish I cause the
developing fluid to pass over the plate as often as required; or I can
remove the developing fluid or add an additional quantity, or add any
other fluid as may be required, and I watch the process of develop-
ment through the two transparent coloured plates which form the bottom

page_text: And when
and the temporary cover respectively of the developing dish.
the picture has been sufficiently developed I pour away the developing
fluid from the trough or reservoir, and I substitute water or suitable
fluid by which I wash the surface of the plate, upon which the picture
is now visible as often as may be requisite. And when the picture has
been sufficiently washed I remove the transparent coloured plate or
frame carrying a plato which forms a temporary cover to the developing
dish as already described, and I remove the plate upon which the picturo
is formed, and I either at once finish and fix the picture in the usual
way, or I place it in any suitable receptacle to be finished and fixed
subsequently.
The accompanying Drawings are in illustration of this Invention.
Figure 1 is a vertical section through the dark slide and sensitizing
dish when they are attached together. A is the dark slide provided in
the usual way with the sliding shulter B for the purpose of exposing the
sensitized glass plate to light in photographic camera; C is a similar
sliding shutter (behind the sensitized plate) instead of the hinged door
ordinarily used; D is a dish or tray as already described, to the upper
edge of which the dark slide A can be temporarily attached by meaus
of grooves, flauges, slides, or fastenings. At the side or end of the
dish A. I make an opening E, Fig. 2, communicating with the trough
or reservoir F which is closed at the ends as shown; G is a hanging
screen or division, the lower edge of which is below the level of the
lower edge of the opening E, so that no light can penetrate from the
trough or reservoir F into the dish D. The internal shape of the trough
or reservoir F is such (as shown in section at Figure 2) that finid
any
poured into it shall flow readily under the hanging screen and through
the opening E into the dish, and it is of such capacity that when the
dish (containing the plate as described) is inclined or tilted diagonally
the whole of the fluid shall pass from the interior of the dish into the
trough F without overflowing it. Sometimes I close the top of the
trough or reservoir with the exception of one or more small openings
as already described and as shewn at H, Fig. 2. The plate coated
with collodion is made sensitive by placing it in this dish with its
collodionized side uppermost, and attaching the dark slide, as shown at
Figure 1, and then pouring a sufficient quantity of solution of a proper
salt of silver into the trough F when it flows over the surface of tho
plate and remains there until the latter is sufficiently sensitized.

page_text: Figure 5. shews the trough or reservoir closed at the top which I use
by filling it with the sensitizing fluid, the dish being inclined or tilted
so that the fluid shall not flow over the glass plate until required.
When it is wished that the fluid shall flow over the glass plate from the
trough or reservoir the dish is brought into a horizontal position. I
sometimes make a support or leg upon each side of the sensitizing dish
turning upon a centre attached to the side of the dish and of such a length
that when they are turned down so as to be in operation, as shown in dotted
lines in Figures 7 and 8, the dish shall be at such an angle that the
whole of the sensitizing fluid shall remain in the trough or reservoir F,
Figure 8, and that when necessary the dish can be turned into a hori-
zontal position upon their centres to allow the sensitizing fluid to flow
over the glass plate, and when necessary I add a third support or leg
to the end of the sensitizing dish to support the dish in a horizontal
position, as shewn at K. in Figure 7.
In Figures 5 and 6 I show the arrangement by which the sensitizing
fluid can be retained permanently in the reservoir F. The opening E
communicates directly between the dish and the reservoir F; this
opening can be closed by a moveable door G having a face of india-
rubber (shewn in plan in Fig. 6); K is a movcable bar which fits
into grooves or guides behind the door G, and carrying screws L, L, by
which the india-rubber face H of the door G can be forced against the
edges of the opening so as to make a water-tight joint..
In order to transfer the plate from the dish to the interior of the dark
slide I make an opening in the bottom of the dish, which opening I fill
up with india-rubber or other suitable opaque flexible material, as shewn
at G, Figures 1 and 2. When the sliding shutter C is withdrawn the
part G is sufficiently flexible to allow the sensitized plate to be forced
by the hand into its place in the dark slide, as shewn in Figure 1, and
the shutter C is returned to its place behind the sensitized plate and the
dark slide A can then be detached from the sensitizing dish D.
Figure 3 shows an arrangement which I sometimes use for transferring
the sensitized plate from the dish to the dark slide. In this case B is a
handle or rod which passes through an aperture C (made water-tight)
in the bottom of the sensitizing dish A. The handle or rod B carries a
frame or support at its upper end, upon which the sensitized plate rests
inside the developing dish, and the plate can be pressed up by it into tho
dark slide when the latter has been temporarily attached to the dish.
j

page_text: Figure 4 shews the arrangement described in which the glass plate is
temporarily attached to the pneumatic plate holder B and is transferred
to the dark slide by the handle of such plate holder.
Figure 7 shows the mothod in which by this Invention I transfer
the plate after a picture has been formed upon it from the dark slide to
a developing dish made according to this Invention. The dark slido
(already shewn in Figure 1) is attached temporarily to a dish B by
means of grooves, flanges, or slides corresponding with those upon the
sensitizing dish D, Figure 1. The upper part of the developing dish B,
Figure 7, can be closed when required by means of a shutter E sliding 1
in grooves or guides and consisting cither of a transparent plate, or of
a frame carrying a transparent plate of yellow or such colour as will
prevent any rays of light which could injure the sensitized plate from
passing through it. The bottom of the developing dish B also is formed
of or fitted with a transparent plate D of a similar colour. When it 1
is required to develope the picture which has been formed upon the
sensitized plate in the dark slide I attach the dark slide to the developing
dish B, and I then withdraw from the latter the transparent plate E;
I next withdraw from the dark slide A (Figure 1) the sliding shutter C
already described, and the sensitized plate then drops from the dark s
slide to the bottom of the developing dish B; I then replace the
transparent coloured shutter E and detach the dark slide from the
developing dish B which is fitted with an opening, hanging screen
or division, and a trough or reservoir F, Figures 7 & 8, similar to those
shown in the scusitizing dish, Fig. 2. By means of this trough or
reservoir F I cover the sensitized plate with a sufficient quantity of a
suitable developing fluid, and when the developement of the picture is
complete I pour away the developing fluid and I wash the picture by
means of water or other suitable fluid, as already described, introduced
from the trough or reservoir F. The transparent coloured plates E
and D above and below the picture allows it to be seen without injury
during the process of developement; I then withdraw the transparent
coloured plate E, and I remove the plato carrying the picture, which
'I either at once finish and fix in the usual way, or I place it in any
suitable receptacle to be finished and fixed subsequently. The dotted
lines K, K, in Figures 7 & 8 show legs or supports which I sometimes
attach, as already described, to the sides of the sensitizing dish, and
which may also be attached if required to the developing dish, as shewn.

page_text: Where the pneumatic holder is used to remove the sensitized glass
plate into the dark slide, as shown in Figures 4 & 5, I empty the
solution from the sensitizing dish by unscrewing the handle of the
pneumatic holder and allowing the solution to escape through the opening
in the centre of the flexible disc.
SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said Benjamin Joseph Edwards in the Great Seal Patent
Office on the 8th September 1871.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, BENJAMIN
JOSEPII EDWARDS, of The Grove, Hackney, in the County of Middlesex,
send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Eighth day of March, in the year of our
Lord One thousand eight hundred and seventy-one, in the thirty-fifth
year of Her reign, did, for Herself, Her heirs and successors, give and
grant unto me, the said Benjamin Joseph Edwards, Her special licence
that I, the said Benjamin Joseph Edwards, my executors, administrators,
and assigns, or such others as I, the said Benjamin Joseph Edwards, 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 "IMPROVEMENTS
IN APPARATUS FOR TAKING PHOTOGRAPHIC PICTURES," upon the condition
(amongst others) that I, the said Benjamin Joseph Edwards, my execu-
tors or administrators, by an instrument in writing under my, or their,
or one of their hands and scals, 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 Scal Patent
Office within six calendar months next and immediately after the date of
the said Letters Patent.
NOW KNOW YE, that I, the said Benjamin Joseph Edwards, do hereby
declare the nature of my said Invention, and in what manner the same
is to be performed, to be particularly described and ascertained in and
by the following statement, and accompanying Drawing.

page_text: My Invention relates especially to apparatus used for taking photo-
graphic pictures upon glass plates (which may be either flat or curved
upon their surfaces, the shape of the several parts of the apparatus being
made to correspond) by means of collodion rendered sensitive to light by
means of solutions of salts of silver, and used in a wet state for the
purpose of obtaining pictures upon it.
The object of my Invention is to enable the person preparing such
plates and taking such photographic pictures and developing them
upon the glass plates to do so without the use of any dark chamber
or chamber illuminated with yellow light only, and to take such photo-
graphic pictures upon plates made sensitive to light by what is well
known as the "wet", process with greater convenienco and with less
weight of apparatus than has heretofore been possible. In order to
carry out this object I take a dark slide of the kind ordinarily used to
hold a sensitized plate and fitted to a photographic camera in the :
usual way, but instead of the hinged back by which the sensitized
glass plate is usually inserted into the dark slide I substitute a back
or shutter sliding in grooves or guides in a similar way to that in
which the shutter in the dark slide on the other side or front of the
sensitive glass plate works, for the purpose of exposing the latter to light ¦
in the camera when necessary. In order to sensitize the glass plate
by coating it or covering it with a solution of the proper salts of silver
after it has been coated with a film of collodion in the usual way
I take a flat dish (which I call a sensitizing dish) of sufficient size
and depth, and formed of opaque or non-actinic glass, gutta percha, i
varnished or other wood, or other suitable material, and I place in this
dish the plate with that side uppermost which has been covered with
collodion, and I form grooves, guides, flanges, slides, or fastenings upon
the upper edge of this dish which are fitted to corresponding ones upon
the back or edges of the dark slido first described in such manner that
when the dish and the dark slide are temporarily attached by means of
the grooves, guides, flanges, slides, or fastenings, they may be held firmly
together without the possibility of light passing between them. And at
one side or end of the dish as described I make a longitudinal slit or
opening of the full length, or nearly so, of such side or end, and of suffi-
cient depth to allow the sensitizing fluid (or solution of salt of silver) to
pass readily through it, and I make the lower edge of this slit or opening
level or nearly level with the upper surface of the glass plate when it
is lying in the dish, and outside the dish, at the end or side in which the

page_text: slit or opening is I make a trough or reservoir closed at the ends, and
sufficiently large to hold the solution of salt of silver necessary to sensitize
the collodion upon the glass plate in the dish. Sometimes I make this
trough or reservoir open or partly open at the top, and I make a hanging
screen or division outside and slightly removed from the slit or opening
already described, the lower edge of this hanging screen or division being
below the level of the lower edge of the slit or opening, and being fixed
in such a position relative to the latter that when water or other fluid is
poured into the trough or reservoir such fluid will flow readily under the
hanging screen and over the lower edge of the slit, and so over the
surface of the plate in the dish, whilst at the same time it is impossiblo
for any light to pass through the reservoir into the interior of the dish.
And sometimes I make two or more hanging screens or divisions (which
may themselves form the upper edge of the slit) the lower edges of which
hang below ridges formed on the bottom of the slit, so that in cross
section the slit is of a notched or serrated form and the light is thus more
perfectly prevented from passing through the slit. And I make the
trough or reservoir of such a size and shape, looking at it in cross section,
that the solution of salt of silver, water, or other fluid, shall flow
smoothly and readily in the required direction through the slit, and I
make it of such capacity that when the dish containing the glass plate
is inclined diagonally the whole of the fluid shall pass from the interior
of the dish through the slit and back into the trough or reservoir without
the latter overflowing. Sometimes I close the upper part of the trough
or reservoir entirely with the exception of one or more small openings
through which the sensitizing solution may be introduced or removed
when necessary, or through which air may be allowed to pass to enable
the sensitizing fluid to pass in or out of the reservoir through the slit
to or from the dish, and I make suitable stoppers or fastenings to
these small openings.
But when it is desired that the sensitizing fluid shall remain in the
trough or reservoir so as to be carried about in it instead of being
removed or poured away, I close the top of the trough or reservoir com-
pletely, and I make a water-tight moveable partition or cover between it
and the dish. For this purpose I do not make hanging screens or
divisions as already described (which are unnecessary, as no light can
indorion of the consitizing dish from the tranch as

page_text: or slit communicating directly without hanging screens or serrated edges:
between the dish and the reservoir, and I close this opening when
requisite by means of a moveable door of wood or other suitable material
one side of which is covered with india-rubber, and I force this india-
rubber against the edges of the opening by means of a moveable bar
which fits into grooves or guides in the sides of the interior of the dish
behind the door covered with india-rubber when the latter is in its place,
and I make a screw or screws which work through the moveable bar,
and the ends or points of which press against the back of the moveable
door covered with india-rubber. In this way the india-rubber covering
the moveable door is forced against the edges of the opening described,
when the sensitizing fluid is in the trough or reservoir, which then forms
a water-tight cistern in which the fluid may be carried about with safety.
This arrangement of sensitizing dish connected with a closed reservoir
having a moveable water-tight cover between it and the dish may be
used for making plates sensitive to light independently of the other parts
of my Invention.
By the apparatus described I make the collodion upon the glass plato
sensitive to light by allowing to flow over it a solution of a salt of silver,
or of other suitable salts, and when the collodion is sufficiently sensitive
I return the solution into the trough or reservoir, or I pour it away. It
is necessary next to remove the sensitive plate, without allowing any
light to reach it, from the dish to the interior of the dark slide (which
has been attached to the upper edges of the dish, as already described,
whilst the glass plate has been sensitized). In order to do this I form
the whole or part of the bottom of the flat dish of india-rubber or other
opaque flexible substance, such as cloth or canvas coated with india-
rubber, which is not injuriously acted upon by the solution of salt of
silver or other solution used; or I make a frame or support upon which
the plate rests in the flat dish, and I connect this frame or support with :
a handle which passes through a water-tight opening in the bottom of
the dish; and when it is desired to transfer the sensitized plate from
the dish to the dark slide I first withdraw the sliding shutter already
described, which I substitute for the hinged back ordinarily used in the
dark slide, and I press the sensitized plate into its position in the dark 3
slide either by means of the hand of the operator pressing its back, with
the intervention of the. india-rubber or other opaque flexible substance,
as described, or by means of the frame or support acted upon by the

page_text: handle, as described; or sometimes I invert the dark slide and dish, and
allow the plate to fall into its place in the dark slide. Sometimes I
make a frame or support, upon which the plate rests, consist of one or
more wires or bars, the ends of which pass through holes in the sides of
the dish sufficiently tight to prevent any light from entering the dish
through the holes, and I crank or bend these wires or bars so that the
cranked part rests upon the bottom of the dish, and the sensitized plate
rests upon it. And I form a handle or knob at one or both ends of
the wire or bar outside the dish, so that by turning the handle or knob
the arm of the crank is elevated, and lifts with it the sensitized plate
into the dark slide. Sometimes I make a pneumatic plate holder in
which the glass plate is held upon a disc or piece of india-rubber, or
other air-tight flexible material, which is then drawn back from the
glass plate so as to leave a partial vacuum between it and the glass
plate; and I make the disc or piece of india-rubber form part of or be
attached to the india-rubber or other flexible substance which forms
the bottom or part of the bottom of the sensitizing dish. And when
requisite I attach the glass plate to the disc of the pneumatic plate
holder already described, which I do by means of a handle containing a
spring and catch, or by nicans of an clastic hollow sphere in the method
which is well known and practised in making pneumatic plate holders,
such handle or hollow sphere being outside the flexible bottom of the
sensitizing dish, and I then proceed to sensitize the glass plate in
the method already described. And when the glass plate is sufficiently
sensitized I introduce it by means of the handle or hollow sphere into
the dark slide, and I then detach the glass plate from the india-rubber
disc by readmitting the air between them. When the sensitized plate
has been by any of these means introduced into the dark slide I close
the sliding shutter behind it (to which I sometimes attach a spring or
support, which presses against the back of the sensitized plate when
the shutter is closed), and I then remove the dark slide containing the
sensitized plate from the flat sensitizing dish. The dark slide may be
placed in any suitable photographic camera, and exposed to light in the
usual way for the purpose of obtaining a photographic picture upon it.
When the plate has been sufficiently exposed to light in the camera
a picture is formed upon it which it becomes necessary to develope by
pouring over it a proper developing solution, of which I use any suitable
kind prepared in any of the usual well-known and practised methods.
In order to do this I take another flat dish (which I call a developing

page_text: dish) similar or nearly similar in shape and size to the sensitizing dish
already described, but having the bottom or part of the bottom made
of glass or other transparent material of a colour which will only allow
to pass through it rays of yellow light, or of such coloured light as
will not act injuriously upon the sensitized plate upon which a photo-
graphic picture has been formed, and in the upper part of this dish I
form grooves, guides, or slides, in which works or slides a plate, or a
frame carrying a plate, of glass or other transparent material of a colour
similar to that just described. Upon the upper edges of this developing
dish I form grooves, guides, flanges, slides, or fastenings similar to those
upon the sensitizing dish already described, and corresponding in the
same way to those upon the dark slide. I then temporarily attach
the dark slide to the developing dish by means of these grooves, guides,
flanges, slides, or fastenings, and I withdraw the transparent yellow
plate, or frame carrying a plate, which covers the upper part of the
developing dish, as already described, and I then withdraw the shutter
which slides in grooves or guides at the back of the dark slide, and
I thus allow the scusitized plate to fall into the developing dish with
the sensitized surface uppermost upon which the picture has been
formed. I then replace the plate, or frame carrying a plate, of trans-
parent yellow glass or other suitable coloured transparent material, as
already described, which thus forms a cover to the developing dish, and
I then detach the dark slide from the fastenings which attach it to the
developing dish. I next proceed to develope the photographic picture
upon the glass plate by pouring a suitable developing fluid into a
trough or reservoir attached to or forming part of one side or end of the
developing dish, and similar to that already described as attached to
the sensitizing dish, but open or partially open at the top; or some-
times I commence to develope the picture before detaching the dark
slide. And in the case of the developing dish I make the slit or opening
which is between the developing dish and the trough or reservoir with
a lianging screen or screens, as already described in the sensitizing dish,
so that the slit or opening may be notched or serrated in form when
seen in cross section, and the light may be completely prevented from
passing through it. By tilting or inclining the developing dish I cause
the developing fluid to pass from the trough or reservoir through the
slit or opening and over the sensitized plate as often as required; or I
can remove the developing fluid or add an additional quantity, or add
any intensifying or other fluid as may be required, and I watch tho

page_text: process of development through the two transparent plates which form
the bottom and the temporary cover respectively of the developing dish,
and between which the sensitized glass plate is lying. And when the
picture has been sufficiently developed I pour away the developing fluid
from the trough or reservoir, and I substitute water or other suitable
fluid, by which I wash the surface of the glass plate, upon which the
photographic picture is now visible, as often as may be requisite; and
when the picture has been sufficiently washed I withdraw the trans-
parent coloured plate, or frame carrying a plate, which forms a temporary
cover to the developing dish, as already described, and I remove the
glass plate upon which the picture is formed, and I either finish and fix
the picture at once in the usual way, or 1 place it in any convenient
receptacle where it remains to be finished and fixed subsequently.
In the accompanying Drawings in illustration of my Invention,-
Figure 1 is a plan, Figure 2 is a longitudinal vertical section, and
Figure 3 a transverse vertical section of the sensitizing dish. The same
letters of reference are used to represent the same parts of the apparatus
in each of these Drawings. A is the tray or dish in which the plate
to be sensitized is placed with the side coated with collodion uppermost.
B in Figure 2 is the dark slide provided in the usual way with the
sliding shutter C for the purpose of exposing the sensitized plate to
light in a photographic camera. D is a similar sliding shutter (behind
the sensitized plate) instead of the hinged door ordinarily used. E, E, E,
are guides or grooves by which the dark slide is temporarily attached
to the top of the dish A which may be kept in its place by a button or
catch not shown in the Drawing. At the side or end of the dish A. I
make a trough or reservoir F which is closed at the ends, and either
closed at the top as shown in Figures 1 and 3, or partly or entirely open
as shown in Figure 4.
In Figure 4 G is a hanging screen or division, the lower edge of
which is below the level of the opening H which communicates between
the sensitizing dish and the trough or reservoir F, so that no light can
penetrate from F into the dish. The internal shape of the reservoir F
in Figure 4 is such that any fluid poured into it shall flow readily
under G and through the opening H into the dish, and it is of such
capacity that when the dish (containing the plate as described) is
inclined or tilted diagonally the whole of the fluid shall pass from the
interior of the dish into the trough F without overflowing the latter.

page_text: The plate coated with collodion is sensitized by placing it in the dish F
with its collodionized side uppermost and attaching the dark slide to the
dish by means of the guides E, and then pouring into the trough Fa
sufficient quantity of solution of a suitable salt of silver which flows
through the opening I over the surface of the plate and remains there
until the latter is sufficiently sensitized. Sometimes I make the
opening H of a notched or serrated form in cross section as shown at G
in Figure 7. When it is desired that the sensitizing solution shall
remain in the trough or reservoir F, I close the top of F completely
as shewn in Figures 1 and 3, and I make a larger opening I com-
municating between it and the dish A, and I close this opening to retain
the sensitizing solution when necessary by the moveable door I which
has a face of india-rubber K. This door is pressed against the edges of
the opening II by means of the moveable cross bar L which fits into
grooves or guides M, M, and carries scrows N, N, by which the door I
is forced into its place. O, O, are wires or guides placed across the
face of the opening II to prevent the sensitized plate from slipping
into the reservoir F. I sometimes make a support or leg P, P, Figures 1
and 3, upon each side of the dish, turning upon centres and of such
a length that when they are turned down so as to be in operation as
shown in dotted lines in Figure 3, the dish shall stand at such an angle
that the whole of the sensitizing fluid shall remain in the trough or
reservoir F, and when necessary I add a third support or leg to the
end of the dish so that the latter may be supported in a horizontal
position.
For transferring the sensitized plate from the dish to the interior of
the dark slide I form the whole or part of the bottom of the interior of
the dish of india-rubber as shewn at R, in Figures 2 and 3, and I make
a hole or opening S, Figures 1, 2, and 3 in the outer bottom of the
dish. Having withdrawn the sliding shutter D, Figure 2, in the dark
slide I press the sensitized plate into its position in the dark slide by
means of the hand of the operator pressing up through the hole S upon
the india-rubber R which is of an extra thickness over the hole S.
In Figure 8 a pneumatic plate holder T is shewn attached to the
india-rubber R so that the sensitive plate can by it be temporarily
attached to the india-rubber R and can be lifted by it into the dark
slide. In Figures 1 and 3 V is a cranked bar or wire (of which I
prefer to use two, though only one is shewn) which I sonictimes use for

page_text: the same purpose. The sensitized plate rests upon the crank, and when
the crank is turned round as shewn in dotted lines in Figure 3 the
plate is lifted up from the dish into the dark slide.
Figure 5 is a plan; Figure 2 a longitudinal vertical section, and
Figure 3 a transverse vertical section of a developing dish constructed
according to this Invention. A is the tray or dish in which the plate
after having been exposed to light is to be developed. B, B, B, are
guides or grooves by which the dark slide containing the plate is
temporarily attached to the dish, and which correspond with those shewn
upon the sensitizing dish in Figures 1, 2, and 3. The upper part of
the developing dish A can be closed when required by the sliding
shutter C in which is the transparent yellow plate D. The bottom of
the developing dish is also formed of a similar transparent yellow plate E.
The dark slide being attached to the developing dish A, the transparent
yellow plate C is withdrawn, and the shutter in the dark slide being
then opened the sensitized plate drops from the dark slide to the bottom
of the developing dish. The transparent yellow shutter C is then replaced
and the dark slide is detached from the developing dish A which is
fitted with a trough or reservoir F and an opening G of a serrated shape
in cross section as shewn in Figure 7, so that no light can pass from the
trough F to the interior of the developing dish A. By means of the
trough or reservoir F the sensitized plate is covered with a sufficient
quantity of a suitable developing fluid, and when the development of
the picture is complete I pour away the developing fluid and wash the
picture by means of water or other suitable fluid introduced through the
trough or reservoir F and the opening G. The transparent coloured
plates E and D between which the plate remains, allow the picture
upon it to be seen without injury during the process of development.
I then withdraw the transparent yellow shutter C and remove the plate,
upon which the picture is visible from the developing dish. Sometimes
I attach one or more thin pieces of glass or other suitable substance to
the transparent yellow bottom E of the developing dish, so that the
sensitized plate may rest upon them without adhering to the bottom,
and so may be more easily removed when finished.
Having now described the nature of my Invention and the manner
in which it is to be performed, I wish it to be understood that I do not
limit myself to the precise forms or proportions of the apparatus
represented in the Drawings which may be varied according to the
13

page_text: circumstances in which the Invention is to be used, nor do I claim the
sensitizing of plates coated with collodion, by means of a tray or dish to
which a trough or reservoir for holding sensitizing solution is attached,
but I claim the construction of such a tray or dish for sensitizing plates
with a closed trough or reservoir for holding a sensitizing solution, in
combination with the water-tight lid or cover as described and shewn,
and also the combination of a sensitizing dish having a reservoir cither
open or closed with grooves or guides for a dark slide having a sliding
shutter as described, and with the flexible bottom or moveable frame
or bars as described for the purpose of introducing the sensitized plate
into the dark slide, and with the water-tight cover arranged as described
for closing the reservoir.
Also the combination of a dish for developing photographic pictures
and having a transparent yellow bottom and transparent yellow sliding
cover, with a reservoir as described and shewn connected to the dish
and having an opening to it of the shape described so that light cannot
pass from the reservoir to the interior of the dish, and with guides or
grooves above the transparent yellow sliding cover to receive the dark
slide in which the sensitized plate is contained.
Also the combination of the sensitizing dish as described, with tho
developing dish as described, so as to form together substantially a
compléte apparatus for the purpose of sensitizing and developing plates
prepared for the purpose of taking photographic pictures.
In witness whereof, I, the said Benjamin Joseph Edwards, have
hereunto set my hand and seal, this Fourth day of September,
in the year of our Lord One thousand eight hundred and seventy-
one.