The discovery I have made and which I call Heliography, consists in reproducing spontaneously, by the action of light, with gradations of tints from black to white, the images received in the camera obscura. 

 I used some of the time while here in making a kind of artificial eye, which is nothing but a small box six inches square; the box will be equipped with a tube that can be lengthened and will carry a lenticular glass. This apparatus is necessary in order to properly complete my process. (1814) 

 I must now do three things: (1) give more sharpness to the representation of the subject; (2) transpose the colors; and (3) fix them permanently, which will not be the easiest of the three. (1816)