IMPROVEMENTS IN APPARATUS FOR TAKING PHOTOGRAPHIC PICTURES
Year: 1857

page_text: was now yever want the time preser well
by the Act.)
PROVISIONAL SPECIFICATION left by Joseph Purnell at the Office
of the Commissioners of Patents, with his Petition, on the 9th April
1857.
I, JOSEPH PURNELL, of John Street West, Barnsbury, in the County of
Middlesex, Photographer, do hereby declare the nature of the Invention
for "IMPROVEMENTS IN APPARATUS FOR TAKING PHOTOGRAPHIC PICTURES," to be as
follows:-
This Invention has for its object an improved method of arranging those
descriptions of photographic cameras in which the photographic surface is
rendered sensitive within the camera.
For this purpose, a bath for containing the exciting fluid is let into the bottom
of the camera, and over this bath a clamp is suspended by a rod passing
through the top of the camera, very much in the same way as is described in.
the Specification of a Patent granted to Frederick Newton, dated the 2nd day
of October 1852; but the clamp therein described is arranged to press against
the upper part of the front of the plate, and in so doing it injures the sensitive
coating of the plate. Now, in place of arranging the clamp in this way,
arrange it that its two jaws press against the two edges of the plate, and thus
it is held without damaging the sensitive coating. The prepared plate having
been placed in the clamp is lowered by means of the rod passing through the
top of the camera into the exciting bath, and when it has remained there a
I so

page_text: sufficient time it is in the same way raised out of it, and the picture is taken
while it is still held by the clamp; afterwards the hand of the operator is
introduced through a sleeve into the interior of the camera, and the plate is
removed from the clamp and placed in a drawer at the bottom of the camera,
which is then closed by a slide, and the drawer is removed for the developing
operation to be effected.
For this purpose a cover is used, which fits on the top of the drawer; this
cover is furnished with eye-pieces, glazed with yellow glass, so as to enable the
operator to watch the operation without admitting light, injurious to the
picture. The bottom of the drawer is also made of yellow glass.
In the side
of the cover is a pocket, made of a flexible light-proof fabric, and containing a
bottle for the developing solution, which is now poured over the plate. When
the developing of the picture is complete, water is poured over the plate through
a trapped hole in the side of the cover, and it is allowed to run out by a valve
at the bottom of the drawer. The picture is fixed in the ordinary manner.
For taking stereoscopic pictures, I mount the lens of the camera on a slide,
as has heretofore been done for other purposes, and in taking the two pictures
the lens is pushed first to one side and then to the other of the camera, so as
to be opposite different parts of the plate; and to prevent the light falling on
one side of the plate while the picture is being taken on the other side, I
employ a partition, reaching from the front of the camera close up to the sur-
face of the plate, and I make this partition moveable, so that it can be turned
up out of the way by a button on the outside, otherwise it would interfere
with the subsequent removal of the plate. In order that the camera may
be suitably moved, as is necessary before taking the second picture of the
stereoscopic combination, I arrange it to slide parallelly along a board,
which is capable of turning on a centre carried by the tripod or support of the
instrument; but the extent of this motion is governed by stops which can
be adjusted by a screw. Thus the rectilinear motion of the camera is obtained
by sliding it along the board, and the angular motion is obtained by turning
the board on its centre.