Dr Fyfe on Photography. 153 



an engraving, it is necessary to trace them on paper, and, after 

 again tracing them with the transfer ink, to transfer them to 

 the stone. Now, by receiving the impression on paper by the 

 photographic process, all the labom' of the first tracing is 

 avoided. But there is no necessity for using paper, as the 

 impression may at once be communicated to the stone, which 

 easily receives the phosphate, and which may therefore be pre- 

 pared in the same way as the papers, and the impression also 

 taken in the usual manner, after which it is traced over with 

 the transfer ink. By this process not only is a great deal of 

 labour saved, but the representation must be much more exact 

 than when traced ; for though by the latter the outline is cor- 

 rect, yet much is left to be afterwards filled in by the eye, 

 Avhereas, by the photographic process, every, even the most 

 minute filament, is distinctly and accm'ately laid down on the 

 btone.* 



Method of taking Impressions hi tchich the lifjhts and shades are 

 not reversed. 



By the different methods now described for getting photo- 

 graphic impressions, the lights and shades are always reversed, 

 because, as it is by the action of the light that the compound 

 of silver is darkened, wherever it is prevented from pene- 

 trating, the paper retains its original colour. Though the 

 impressions thus procured are accurate as to outlines, yet, 

 in n.any cases the representation is far from being pleasing ; 

 it is therefore a great desideratum to have a method of getting 

 impressions in which there is no reverse ; in fact, to give a 

 true representation of the object, and in this I have succeeded 

 by the use of the iodide of potassium. I have already stated, 

 that, when the darkened phosphate is exposed to the iodide, it 



* For this method of applying the photographic process I am indebted 

 to Mr Nichol, lithographer, by whom lithographic impressions, thus taken, 

 were exliibited to the Society of Arts. As a pi-oof of the value of this 

 process, I may also mention, tliat, on the evening of the 17th of April, wlicn 

 I exhibited a photographic specimen of dried ferns, it was, by Mr Forrester, 

 lithographed, and imjjressions taken from it in the course of two hours ; had 

 this been done in the usual way, it would have required many hours of 

 labour, and, after all, not have given such accurate delineations. 



