AMERICAN INSTITUTE. 687 



which we depend for the black to form the dark parts of the pic- 

 ture; this operation requires great attention, as the black maybe 

 much enfeebled by a prolonged bath. The hyposulphite must be 

 afterwards disengaged by numerous washings in several waters; 

 then suspend it from a corner to dry, and if you have been suc- 

 cessful, the proof cannot be changed by light, because the black 

 gallate remains fixed in the paper. 



When you desire to take a view, be sure and have your per- 

 pendicular lines perfectly true, and do not on any account make 

 the image unnecessarily large, and if you would have a picture 

 free from ftmlt, let the distance from the object you intend to 

 copy be about one quarter of the entire scene. You may take 

 the whole with one lens, if you use half plate size, and I would 

 prefer to be near rather than far from the object, as it requires a 

 shorter period of time in the camera. The image will not be 

 clear and satisfactory if the rays of the sun strike upon the object 

 glass. 



There is a great difference in the lens; many are clear in the 

 centre, but indistinct at the edge, where it is absolutely necessary 

 they should be clear. Frequently the chemical focus does not 

 coincide with the visible focus. 



Double achromatic lenses are necessary when portraits are to be 

 taken; they centralize light, and are rapid in their operation. 

 Those made in France by Messrs. Lerebours are admirable; they 

 are so arranged that a diaphragm may be attached, which makes 

 the object very clear. 



Nine out of ten operators, when taking a portrait, place the 

 shoulders and head in the same position, showing a great want of 

 taste, as one side should always be more illuminated than the 

 other to make an interesting picture. Another fault is, that the 

 hands and knees are rarely in focus with the face; this may be 

 easily obviated by a little calculation. The light should never 

 reflect into the camera at right angles. 



Pictures may be taken in the camera by means of collodion on 

 glass. This preparation is a solution of gun cotton in ether, with 

 a small portion of iodide of silver dissolved in iodide of potassium. 



