150 Dr Fyfe on Photography. 



it in the usual way. It will be found to have all the richness 

 of an oil painting. 



By this process, impressions equally distinct and brilliant 

 may be taken on metal. Perhaps this may be of service in 

 saving engravers the time and trouble of laying down on the 

 metal the figure to be engraved. 



The impressions received by the modes now described are 

 taken by exposure to the solar ray. It is well known that the 

 paper may be darkened by other means, as by the oxihydro- 

 gen blowpipe ; but there is no necessity for having recourse 

 to so intense an artificial light. I haA'e found that, by con- 

 centrating the light of a common fire by metallic mirrors, 

 the paper is darkened, and the same also occiu's with the 

 flame of a gas lamp. Of course, the time required is much 

 longer than when exposed to sunshine. In this way I have 

 succeeded in getting impressions of dried leaves almost as 

 distinct as by solar light ; indeed, we may dispense altogether 

 with the mirror, for, by exposing the paper with the leaf on 

 it, in a frame, to the light of a common fish-tail gas-burner, 

 at the distance of a few inches, I have procured specimens 

 some of which, though on a small scale, have all the richness 

 of those taken by solar light. 



The concentration of the rays by a metallic mirror, so as 

 to get quit of the interference of the lens, would, no doubt, 

 be a great improvement in the camera obscura, provided it 

 coidd be accomplished. May not something of this kind be 

 the method followed by Daguerre in getting his camera re- 

 presentations .'' 



3. Preservation of the Impressions. 



It is evident that, as the impression is produced by the 

 agency of light on the compound of silver, when the paper is 

 again exposed, the hght will begin to act, and ultimately 

 darken the whole, thus effacing the impression ; hence the 

 necessity of a preservative process. Two methods have been 

 recommended by Mr Talbot, as applicable to the chloride, one 

 by the iodide of potassium, the other by sea-salt. When so- 

 lution of iodide of potassium is added to that of lunar caustic, 



