198 Mr. Talbot's Accmint of the 



the unshaded parts are slowly copied ; but the lights trans- 

 mitted by the shaded parts are seldom so definite as to form 

 a distinct resemblance of them by producing different inten- 

 sities of colour. 



" The images formed by means of a camera obscura have 

 been found to be too faint to produce, in any moderate time, 

 an effect upon the nitrate of silver. To copy these images was 

 the first object of Mr. Wedgwood, but all his numerous ex- 

 periments proved unsuccessful." 



These are the observations of Sir Humphry Davy. I have 

 been informed by a scientific friend that this unfavourable re- 

 sult of Mr. Wedgwood's and SirHumphryDavy's experiments, 

 was the chief cause which discouraged him from following 

 up with perseverance the idea which he had also entertained 

 of fixing the beautiful images of the camera obscura. And no 

 doubt, when so distinguished an experimenter as Sir Hum- 

 phry Davy announced " that all experiments had proved un- 

 successful," such a statement was calculated materially to dis- 

 courage further inquiry. The circumstance also, announced 

 by Davy, that the paper on which these images were depicted 

 was liable to become entirely dark, and that nothing hitherto 

 tried would prevent it, would perhaps have induced me to 

 consider the attempt as hopeless, if I had not (fortunately) 

 before I read it, already discovered a method of overcoming 

 this difficulty, and ofjixitig the image in such a manner that 

 it is no more liable to injury or destruction. 



In the course of my experiments directed to that end, I have 

 been astonished at the variety of effects which I have found pro- 

 duced by a very limited number of different processes when 

 combined in various ways; and also at the length of time 

 which sometimes elapses before the full effect of these mani- 

 fests itself with certainty. For I have found that images 

 formed in this manner, which have appeared in good preser- 

 vation at the end of twelve months from the time of their 

 formation, have nevertheless somewhat altered during the se- 

 cond year. This circumstance, added to the fact that the 

 first attempts which I made became indistinct in process; of 

 time (the paper growing wholly dark), induced me to watch 

 the progress of the change during some considerable time, as 

 1 thought that perhaps all these images would ultimately be 

 found to fade away. I found, however, to my satisfaction, 

 that this was not the case; and having now kept a number of 

 these drawings during nearly five years without their suffering 

 any deterioration, I think myself authorized to draw conclu- 

 sions from my experiments with more certainty. 



