80 PHOTO-MICROGRAPHS. 
and when the light has been feeble and the time 
of exposure long, the image often seems to be 
quite superficial. 
The development should be continued until the image 
as seen tn all its details from the back of the plate. 
If it will not develop entirely through the gela- 
tine film, it is because the exposure has been too 
short; and the superficial image seen upon the 
front of the plate, although apparently well timed, 
will be very faint after the plate has come from 
the hyposulphite bath. 
The ferrous-oxalate developer, if not too strong, 
does not injure the plate, even if it be left in the 
solution for fifteen or twenty minutes, and a mak- 
ing photo-nucrographs i ts generally best to give rather a 
short exposure, and then to develop the plate to the fullest 
extent. The developer does not act upon that 
portion of the plate unaffected by light, and the 
effect of this long development is simply to inten- 
sify the image and bring out all the finer details. 
The writer is in the habit of leaving his plate in 
the developing-tray while he attends to the ar- 
rangement and focusing of another object, and 
often several exposures are made, and the plates 
placed in separate developing solutions, before the 
first exposed is considered fully developed. 
For other methods of development the reader 
is referred to manuals of photography. 
