90 Intelligence and Miscellaneous Articles. 



ercise of skill and judgement. It would hardly be believed how dif- 

 ferent an effect is produced by a longer or shorter exposure to the 

 light, and, also, by mere variations in the fixing process, by means 

 of which almost any tint, cold or warm, may be thrown over the 

 picture, and the effect of bright or gloomy weather may be imitated 

 at pleasure. All this falls within the artist's province to com- 

 bine and to regulate ; and if, in the course of these manipulations, 

 he, nolens volens, becomes a chemist and an optician, I feel confident 

 that such an alliance of science with art will prove conducive to the 

 improvement of both. 



I remain, yours, &c. 

 31, Sackville Street, Feb. 5, 1841. H. F. Talbot. 



Dear Sib, — I will now proceed to give you some further details, for 

 which I had not room in my last letter, respecting the phenomena 

 which occur during the very singular photographic process to which 

 I have given the name of Calotype. And I may as well begin by 

 relating to you the way in which I discovered the process itself. One 

 day, last September, I had been trying pieces of sensitive paper, pre- 

 pared in different ways, in the camera obscura, allowing them to 

 remain there only a very short time, with the view of finding out 

 which was the most sensitive. One of these papers was taken out 

 and examined by candlelight. There was little or nothing to be 

 seen upon it, and I left it lying on a table in a dark room. Return- 

 ing some time after, I took up the paper, and was very much sur- 

 prised to see upon it a distinct picture. I was certain there was 

 nothing of the kind when I had looked at it before ; and, therefore 

 (magic apart), the only conclusion that could be drawn was, that 

 the picture had unexpectedly developed itself by a spontaneous ac- 

 tion. 



Fortunately, I recollected the particular way in which this sheet 

 of paper had been prepared, and was, therefore, enabled immediately 

 to repeat the experiment. The paper, as before, when taken out of 

 the camera, presented hardly anything visible ; but this time, in- 

 stead of leaving it, I continued to observe it by candlelight, and had 

 soon the satisfaction of seeing a picture begin to appear, and all the 

 details of it come out one after the other. 



In this experiment, the paper was used in a moist state ; but since 

 it is much more convenient to use dry paper if possible, I tried it 

 shortly afterwards in a dry state, and the result was still more ex- 

 traordinary. The dry paper appeared to be much less sensitive than 

 the moist ; for when taken out of the camera after a short time, as 

 a minute or two, the sheet of paper was absolutely blank. 



But, nevertheless, I found that the picture existed there, although 

 invisible ; and by a chemical process analogous to the foregoing, it 

 was made to appear in all itsj>erfection. 



After several further experiments, which were requisite in order to 

 come to a right understanding of this unexampled natural process, 

 I found it expedient to abandon the former method of taking views 

 with the camera, in favour of the new one, so far excelling it in ra- 



