454 On Sun Pictures. 
of the operation ; also with the degree of care devoted to the 
preparation of the paper. 
4th Operation—The Development of the Picture. 
The paper upon its removal from the camera rarely exhi- 
bits any trace of a picture. It must still more than ever be 
kept from the daylight. 
Mix 1 part of aceto-nitrate solution with 8 parts of satu- 
rated solution of Gallic acid, as described in the 2nd opera- 
tion. Take a clean brush and lay this on for a quarter of 
an hour, or until the picture is thoroughly developed: when 
the Gallic acid is used the brushes must be frequently 
changed, or soaked in a strong solution of nitric acid. 
5th Operation—The Fixing. 
Mix 1 part of saturated solution of hyposulphite of soda 
with 6 parts of clean water. This should be poured into a ves- 
sel sufficiently large to contain the paper lying flat. When 
the picture is considered to be sufficiently developed, it is to 
be plunged into this solution with the face downwards, and 
kept there until the yellow colour produced by the iodide of 
silver has entirely disappeared, which would be in about an 
hour. The solution will serve for a number of pictures if 
fresh hyposulphite is added occasionally, and the dirt ex- 
iracted, by its being filtered through blotting-paper. 
; 6th Operation—Removal of Hyposulphite. 
I soak the picture for some time in two vessels of water, 
then dry by hanging it up by the corner. ‘his finishes 
the production of the negative picture, the most difficult of 
the two. Ina perfect negative, nature is as it were reversed : 
the sky and bright lights should be quite black, and the 
