BRINGING OUT THE PICTURE. 



When the paper is taken from the camera or the frame, nothing 

 is visible upon it ; but by attending to the following directions, 

 the latent picture will quickly develop itself. Having mixed 

 together about one drachm of a saturated solution of protosutphate 

 of iron and two or three drachms mucilage of gum arabic, pour a 

 small quantity into a flat dish. Pass the prepared side of the 

 paper taken from the camera rapidly over this mixture, taking 

 care to ensure complete contact in every part. If the paper has 

 been sufficiently impressed, the picture will almost immediately 

 appear, and the further action of the iron must be stopped by the 

 application of a soft sponge and plenty of clean water. Should 

 the image not appear immediately, or be imperfect in its details, 

 the iron solution may be allowed to remain a short time ; but it 

 must be kept disturbed, by rapidly and lightly brushing it up, 

 otherwise numerous black specks will form and destroy the pho- 

 tograph. Great care should be taken that the iron solution does 

 not touch the back of the picture, which it will inevitably stain, 

 and, the picture being a negative one, render useless as a copy. 

 A. slight degree of heat will assist the development of the image 

 where the time of exposure has been too short. 



The picture should be carefully washed to take off any super- 

 ficial blackness, and may then be permanently fixed by being 

 washed with water, to which a small quantity of ammonia, or, 

 better still, hyposulphite of soda has been added. The paper 

 must again be well soaked in clean water, to clear it from the 

 soluble salts, and may then be dried and pressed. 



POSITIVE PICTURES. 



These are procured in the same manner as the copies of the 

 prints, etc. just described ; using the negatives before obtained 

 in place of the objects themselves. Instead, however, of using 

 the iron solution, the paper must be exposed to the light, in the 

 frame, a sufficient time to obtain perfect copies. The progress of 

 the picture may be observed by turning up the corner of the 

 paper, and, if not sufficiently done, replacing it exactly in the 

 same position. They should be fixed with hyposulphite as before 

 directed. It is sometimes better to take negative pictures in the 

 B2 



