^22 Professor Draper on the Process of Daguerreotype, 



After the proof is washed, all the defects in the preparation 

 of the plate become apparent. If a film of mercury has ex- 

 isted on it, due to its not having been burnt sufficiently long, 

 there will be found a want of distinctness in the shadows ; or 

 if the plate has not been burnt at all, perhaps the former im- 

 pressions which have been obtained will re-appear. This ac- 

 cident frequently happened in my earlier trials, when care 

 had not been taken to give a due exposure each time to the 

 spirit flame. Spectral appearances of former objects, on dif- 

 ferent parts of it, emerged, — an interior with Paul Pry coming 

 out, when the camera had been pointed at a church. 



There is no difficulty in procuring impressions of the moon 

 by the Daguerreotype, beyond that which arises from her 

 motion. By the aid of a lens and a heliostat, I caused the 

 moonbeams to converge on a plate, the lens being three inches 

 in diameter. In half an hour a very strong impression was 

 obtained. With another arrangement of lenses I obtained a 

 stain nearly an inch in diameter, and of the general figure of 

 the moon, in which the places of the dark spots might be in- 

 distinctly traced. 



An iodized plate, being exposed for fifteen seconds only 

 close to the flame of a gas light, was very distinctly stained ; 

 in one minute there was a very strong impression. 



On receiving the image of a gas light, which was eight feet 

 distant, in the camera, for half an hour, a good representation 

 was obtained. 



The flame of a gas lamp was arranged within a magic 

 lanthorn, and a portion of the image of a grotesque on one of 

 the slides received on a plate ; a very good representation was 

 procured. 



With Drummond's light, and the rays from a lime-pea in 

 the oxy-hydrogen blowpipe, the same results were obtained. 



In the first experiments which I made for obtaining por- 

 traits from the life, the face of the sitter was dusted with a 

 white powder, under an idea that otherwise no impression 

 could be obtained. A very few trials showed the error of this ; 

 for even when the sun was only dimly shining, there was no 

 difficulty in delineating the features. 



When the sun, the sitter, and the camera are situated in 

 the same vertical plane, if a double convex non-achromatic 

 lens of four inches diameter and fourteen inches focus be em- 

 ployed, perfect miniatures can be procured, in the open air, 

 in a period varying with the character of the light, from 20 

 to 90 seconds. The dress also is admirably given, even if it 

 should be black ; the slight differences of illumination are 



