Development in the Dark Room. Al 
(i do not say it will be corrected, for intensification is an extremely 
hazardous operation and should be rarely practiced) by first wash- 
ing the plate thoroughly so that all traces of hypo are eliminated 
—be particular about this—and then immerse the plate in a satu- 
rated solution of bichloride of mercury which has previously 
been filtered through absorbent cotton or filter paper, so as to pre- 
vent any particles of undissolved mercury from coming in contact 
with the film, for if allowed to remain in contact with the gelatine 
it attacks the film with great energy, producing minute pin-holes 
in it. Always keep the solution moving as you would the devel- 
oper, and watch closely for any particles of undissolved mercury, 
which will sometimes form in the saturated solution even after it has 
been strained. Should any adhere to the film, remove it at once 
with the finger, and keep the solution moving so that it will not 
again have achance to settle in any one spot; in a few moments 
you will observe the edges of the plate assume a grayish color, 
which gradually extends to the center, and continues to grow 
whiter until at length you get a positive effect on the plate. The 
degree to which intensification should be carried, can only be 
determined by the condition of the plate, but it rarely should be 
carried beyond the point where the plate is gray all over—or when 
you have observed a positive effect all over it—remove it at once 
from the bichloride solution and wash thoroughly, then immerse 
it in a weak solution of ammonia (about ten drops to an ounce of 
water); as soon as the grayish color before spoken of has changed 
to dark brown, remove it from the ammonia solution and wash 
thoroughly, and if upon examination by transmitted light there 
does not appear to be sufficient density, it may be again immersed 
in the ammonia solution and kept there until it has become black 
instead of brown; but I have never found any advantage in return- 
ing the plate the second time to the bichloride solution ; others 
may have been more fortunate, but my experience is, that having 
once gone through the ammonia solution, the bichloride solution 
has no further effect on it. Be very careful to pour the bichloride 
solution upon the plate gently, for if dashed upon it the solution 
appears to penetrate the gelatine at the point of impact, and after 
the final washing is complete you will find the negative much 
denser at that point than anywhere else, and you will have to 
resort to local reduction to get an even intensification all over the 
plate. This is an extremely delicate matter to perform, and hardly 
worth describing here. 
