SClffiNTmC SUMMABY. 
4UJ 
The later results of Professor Graham’s important discoveries in dialysis, 
which have reference to the differences observed in the passage of various 
liquids through porous membranes, have placed in the hands of practical 
photographers a new and valuable instrument. The dialysis will serve a useful 
purpose in effecting the separation of salts from highly-charged albumen and 
other liquids of a glutinous nature ; it is only necessary to expose these mix- 
tures for a short time to the action of pure water outside the diaphragm, when 
it will be found that the saline constituents have passed through the animal 
membrane, or the so-called vegetable parchment, without any appreciable los$ 
on the part of the albumen. So complete is this 'separating action, that it has 
been suggested to employ such means in the analysis of compound photogra- 
phic preparations. 
Improvements in the construction of photographic apparatus have resulted 
in the manufacture of cheap and efficient rolling presses, by the aid of which 
a very superior surface may be imparted to paper in the form of the finished 
proof, or in any intermediate stage. Messrs. Bury Brothers, of Manchester, 
have succeeded in greatly reducing the cost of these machines, so that they 
are now likely to come into general use, and enable the photographer to 
dispense with the practice of sending away the proofs to be milled. 
The construction of the Camera itself is likely to undergo alteration in 
respect to placing the means of adjustment for focus in front, instead of the 
usual sliding arrangement being worked from the back. Many contrivances 
have been suggested ; among others, that proposed by Mr. Window possesses 
the advantage of rigidity from the circumstance of the dark slide entering that 
portion of the camera-body which is firmly clamped to the tripod stand. 
The ground glass is also permanently attached to the back of the camera. 
Mr. Crookes has reported upon the comparative efficiency of a substitute 
for orange-glass. Muslin or other light textile fabric is coated with glue in 
order to close the interstices, and form a continuous layer of sheet gelatine ; 
this being submitted to the action of a weak solution of nitrate of silver, 
and then exposed to the light, forms a compound which is impervious to all 
but the yellow rays, and being tolerably permanent and insoluble, is suscepti- 
ble of application for laboratory windows and similar purposes. The facts 
which stand opposed to its general introduction is the brittleness, which 
unfits it for rough exposure, and the tendency to air-bubbles in the glue 
giving rise to small pin-holes in the fabric. 
The announcement of a ncio photographic process by Mr. Emerson J. 
Reynolds, of Dublin, has given rise to much discussion, and to the assertion 
of counter claims of priority. Sir John Herschel, Mr. Burnett, Dr. 
Phipson, and others, appear to have employed the oxalate of peroxide of 
iron as a chemical agent, which suffers reduction to a proto-salt on exposure 
to sunlight, and is capable therefore of a photographic application. Mr. 
Reynolds proposes to develop upon paper the result of such exposure by 
treatment afterwards with ammonio-nitrate of silver, when a picture will 
be formed by the dark reduced silver partaking of the general character 
of a photographic negative. Sir John Herschel preferred chloride of gold 
for developing the image ; and Dr. Phipson endeavoured to dispense with 
the use of silver by employing pyrogallic acid in conjunction with the per- 
manganate of potash. 
