90 PHOTO-MICROGRAPHS. 
posure is so brief that it is better to work ona 
cloudy day, or late in the afternoon, when the 
light is already too feeble for making negatives. 
The dry-plate must be introduced into and taken 
from the plate-holder in a room from which all 
actinic light is excluded. If the operating-room 
is sufficiently protected when the sliding-shutter is 
closed, this will answer the purpose; otherwise a 
dark closet will be required. 
A small lantern, dark on three sides, and hav- 
ing the other side closed with ruby glass, will be 
required for manipulations conducted in a dark 
room from which all light is excluded. 
The development of the positive and other 
photographic manipulations is conducted in ex- 
actly the same manner as in the case of a 
negative. 
A very fair positive may be made on glass from 
a silver print — on paper — by the following 
method: If the silver print is mounted on a card, 
detach it by immersion in fot water for a few 
minutes; dry it thoroughly under pressure, so 
that it may be quite smooth; place a piece of 
plane-glass in the plate-holder, next to this the 
silver print, then a dry-plate with the film in 
contact with the printed image upon the paper, 
and finally a piece of black cardboard, as a non- 
reflecting background ; close the plate-holder, and 
expose as directed for positives on glass. 
The result, if the exposure is well timed, will be 
a very fair negative, from which, when finished, 
positives on glass may be printed. 
