Edinburgh Society of Arts. 463 



Feb. 19. — Read, " Extracts from Letters addressed to Dr. Royle, 

 V.P.R. & F.L.S., Prof. Mat. Med., King's College. By Dr. Fal- 

 coner, Superintendent of the Hon. E. I. C.'s Garden, Saharunpore." 



EDINBURGH SOCIETY OF ARTS. 

 April 17. — Among the communications laid before the Society 

 at this meeting was the following : 



Notice of recent improvements effected by him in Photographic 

 Drawing, &c. whereby the lights and shadows are not reversed. By 

 Andrew Fyfe, M.D., F.R.S.E., Vice-Pres. Soc. Arts.* 



Before proceeding to describe his method of taking impressions 

 without having a reverse. Dr. Fyfe stated that he had received com- 

 munications from several gentlemen, mentioning that they had re- 

 peated his experiments with the phosphate of silver paper, and also 

 with the ammonia, as a preservative. With regard to the latter, it 

 was found by them all to prevent the further action of the light on 

 the specimens, provided it was properly applied. As a test of its pro- 

 per application, he stated, that the best method is to put the paper 

 into a diluted solution of the ammonia, and to leave it for a short 

 time, till all the yellow parts of the impression become white, show- 

 ing that the whole of the yellow phosphate is washed out. An im- 

 pression on paper, taken by Mr. William Forrester, lithographer, 

 was shown. In this the lights and shadows were preserved as in 

 the original, by covering the light parts of the drawing from which it 

 was taken with a dark ground, and leaving the darker parts lighter 

 and lighter, so as to allow the greater transmission of light through 

 what in the original was the darkest. A lithographic stone was 

 likewise shown, on which an impression was taken by Mr. Nichol, 

 lithographer, bj' covering the stone with phosphate of silver, and 

 then, after putting an engraving on it, exposing it to light in the 

 usual way. Dr. Fyfe then proceeded to describe the process by 

 which he had succeeded in getting impressions, in which the lights 

 and shadows are not reversed. For this purpose the phosphate pa- 

 per is first darkened by the action of light ; it is then immersed in a 

 solution of the iodide of potassium, and while still moist, exposed to 

 light, with the object, the impression of which is to be taken, placed 

 on it, and left till the whole of the paper exposed becomes yellow, 

 and when removed it exhibits a distinct representation of the object. 

 In this process there is a tendency of the iodide to convert the dark 

 phos])hate into yellow iodide of silver, which it does instantly when 

 the solution is strong, but very slowly when it is weak, unless it is 

 exposed to light, and then the action goes on rapidly. It was obser- 

 ving this that induced Dr. Fyfe to try the influence of light on phos- 

 phate j)aper besmeared with iodide of potassium, by which he was led 

 to the discovery. Of course, when an object, which allows the light 

 to pass through it diflPerently, is put on the paper, those parts on 



• For otl)cr papers on this subject see our numbers for March and May, 

 p. 196,365, and 368 : also Miscellaneous Articles in the present number. — 

 Edit. 



