506 Intelligence and Miscellaneous Articles. 



4. The use of a second bath of nitrate of silver (1-20) after 

 washing the plates with fluoride of potassium used as an accelera- 

 ting agent. The object of this operation is not only to increase still 

 more the sensibility, but especially to transform the excess of fluoride 

 of potassium into fluoride of silver, and thus to prevent its acting 

 upon the glass and causing the separation of the albumen ; it is also 

 useful, but in regard to the first point only, whatever the accelera- 

 ting agent used may be. 



5. Substitution of a strong bath of sulphate of iron at the tempera- 

 ture of 194° F. for the gaUic acid generally used for bringing out the 

 image. This modification produces an enormous increase of sensi- 

 bility ; moreover, the high temperature furnishes images of a very 

 light shade, and this is the essential point upon which the production 

 of proofs upon glass depends ; lastly, the opacity is less than by the 

 other processes ; hence, in regard to the productions upon paper, there 

 results a softness which does not exclude delicacy, and the absence 

 of which has hitherto frequently been urged as an objection to the 

 employment of albuminous films. 



6. Fixing the proofs in four or five minutes by the perfect solution 

 of the iodide of silver, by means of a bath of cyanide of potassium 

 and hyposulphite of soda of proper strength. 



This method of fixing is superior in every respect, both to the 

 bromide of potassium, and the hyposulphite generally employed un- 

 mixed. It gives in a very short time, and without injuring the 

 proofs, not only unexceptionable fixation, but also complete trans- 

 parence in the parts which have not taken the impression, and lastly, 

 considerable increase in the adhesion of the entire coating. It may, 

 moreover, be easily applied to all the known processes of photography 

 upon glass, and even without any doubt to the operations upon 

 paper. 



The proofs obtained by this process consist of opake, yellowish 

 white images, lying in a diaphanous medium, and presenting, there- 

 fore, the positive or negative aspect, according as to whether they 

 are placed upon a darker or lighter ground. 



As negative proofs, they resist changes of temperature better, are 

 more transparent (which allows of their being produced by a feeble 

 light), and lastly, as I have stated, they furnish softer drawings 

 upon paper than those prepared by other processes. 



As positive proofs, and to allow of their being included under this 

 head, the side of the albumen has only to be coated with black 

 paint ; they present a clearness and delicacy comparable to metallic 

 plates, infinitely more beauty of outline, and lastly, a variety of 

 shades, of which many are very artistic. 



In regard to the time requisite for exposure to the light, I may 

 add that I have obtained landscapes by the sun in a second (with 

 a plano-convex objective consisting of a combination of glasses, fur- 

 nished with a diaphragm the aperture in which was 0™03), and por- 

 traits in the shade out-of-doors in 4 or 5 seconds, and in a room in 

 from 8 to 15 seconds (with the same object-glass without the dia- 

 phragm). Moreover, the proofs are naturally erect; and hence, even 



