, to which
ammonia is added at intervals of about thirty seconds, so as to
produce a slight tendency to fog; the time of development being from
three to four minutes. The numbers are supposed to be read after
fixation, the plate being held against the sky.
Schumann's statement that a gelatino bromide plate is less sensitive
when developed at 30 deg. C. than when developed at 5 deg., is contested; the
more recent investigations of Dr. Eder serving to demonstrate that a
developer at a moderate high temperature acts very much more rapidly
than when the temperature is low; but when a sufficient time is
allowed for each developer to thoroughly penetrate the film, the
difference becomes less apparent. Here are examples:
_A.--Oxalate Developer._
Temperature of developer 4-8 deg. C. 16-17 deg. C. 26-28 deg. C.
Time of development 1 min. 3 deg. W. 8 deg. W. 13 deg. W.
" " 2 min. 91/2 deg. W. 10 deg. W. 15 deg. W.
_B.--Pyrogallic Developer._
Temperature of developer 1-2 deg. C. 26-28 deg. C.
Time of development 1/4 min. 6 deg. W. 10 deg. W.
" " 3 min. 14 deg. W. 15 deg. W.
* * * * *
INTENSIFIER FOR WET PLATES.
By MAJOR WATERHOUSE.
The collodion process is still preferred for reproducing black and
white designs, drawings, engravings, etc., where very dense negatives
are desirable. The fixed and washed plate is put in a bath of bromide
of copper (ten per cent.
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