204 Mr. Talbot's Account of the 



The result of these experiments was the discovery of a mode 

 of preparation greatly superior in sensibility to what I had 

 originally employed: and by means of this, all those effects 

 which I had before only anticipated as theoretically possible 

 were found to be capable of realization. 



When a sheet of this, which I shall call " SensitixK Paper" 

 is placed in a dark chamber, and the magnified image of some 

 object thrown on it by the solar microscope, after the lapse of 

 perhaps a quarter of an hour, the picture is found to be com- 

 pleted. I have not as yet used high magnifying powers, on 

 account of the consequent enfeeblement of the light. Of course, 

 with a more sensitive paper, greater magnifying power will 

 become desirable. 



On examining one of these pictures, which I made about 

 three years and a half ago, I find, by actual measurement of 

 the picture and the object, that the latter is magnified seven- 

 teen times in linear diameter, and in surface consequently 289 

 times. I have others which I believe are considerably more 

 magnified ; but I have lost the corresponding objects, so that 

 I cannot here state the exact numbers. 



Not only does this process save our time and trouble, but 

 there are many objects, especially microscopic crystallizations, 

 which alter so greatly in the course of three or four days (and 

 it could hardly take any artist less to delineate them in all 

 their details), that they could never be drawn in the usual way. 



I will now describe the degree of sensitiveness which this 

 paper possesses, premising that I am far from supposing that 

 I have reached the limit of which this quality is capable. On 

 the contrary, considering the few experiments which I have 

 made, (few, that is, in comparison with the number which it 

 would be easy to imagine and propose) I think it most likely, 

 that other methods may be found, by which substances may 

 be prepared, perhaps as much transcending in sensitiveness 

 the one which I have employed, as that does the nitrate of 

 silver which I used in my first experiments. 



But to confine myself to what I have actually accomplished, 

 in the preparation of a very sensitive paper. When a sheet 

 of this paper is brought towards a window, not one through 

 which the sun shines, but looking in the opposite direction, it 

 immediately begins to discolour. For this reason, if the paper 

 is prepared by daylight, it must by no means be left uncovered, 

 but as soon as finished be shut up in a drawer or cupboard 

 and there left to dry, or else dried at night by the warmth of 

 a fire. Before using this paper for the delineation of any ob- 

 ject, I generally approach it for a little time towards the light, 

 thus intentionally giving it a slight shade of colour, for the 



