PHOTO-MICROGRAPHY. 79 
It may be thought that exposures extending over forty minutes 
must be inconvenient, but this is not found so in practice; the 
camera is left to itself, the operator returning to it when the time 
for complete exposure is finished. 
After the sensitive plate has been exposed for the necessary 
length of time, it is ready for development ; it is therefore taken 
into a room from which every trace of actinic light has been ex- 
cluded, and there the picture is brought to view by the use of the 
developing solution. Nearly every photographic manipulator has 
his own way of developing, though the general principles are the 
same, and as I fear that every one will not agree with my method, 
I give that advised by Messrs Wratten & Wainwright for their 
instantaneous dry plates :— 
Stock SOLUTION A.* 
LUTON As LIQUOR, 2/07/20. acs aneses anda tater sete I ounce. 
IB@tASS Dr OmmG est sesceitivecmionses tie aggencmeracasics 60 grains. 
Wifclbery eopsmententenaita Wiisercoaseisatet be wa deincdaieewslelsos eieibee 2 ounces. 
DEVELOPER. 
ByRO CNG PACA 2. c.- 398 «ccckwsbs ler sedersetecessadeaes 6 grains. 
SHOE EMS OMIELOTI AIP cance viese Gece co eve neescmeinieenesee 1o drops. 
DV riestagartees Sona ooo Stara aes ae vache case ewclaseesnas wet 2 ounces. 
Lay the exposed plate in a dish of cold water to soak while the 
pyrogallic acid is mixed. For each } or 5 x 4 plate use six grains 
of pyro., diluted with two ounces of water. First pour off the 
water from the plate and apply the pyro. solution, then add five 
drops of “Stock Solution A*,” and keep this weak developer on 
the plate until the highest lights are pretty well visible; then add 
from fifteen to twenty drops more of “ A*” to finish development. 
By this method more of the film is employed and greater density 
is obtained. Whenever any of solution “A*” is to be added to 
the pyro. solution it should be first dropped into the developing 
cup, and then, if the solution which is in the dish be poured back 
into the cup, a perfect admixture will be the result without the neces- 
sity of stirring. With correct exposure full printing density may 
be easily attained with the alkaline pyro. alone. We supply no 
plate that will not bear one hundred drops of “Stock Solution A*” 
without fog. One thickness of deep ruby glass is uzsafe ; two, at 
least, are necessary. Should any discolouration of the film appear 
after the negative has been fixed and washed, it may be cleared 
away with a weak solution of perchloride of iron and water (about 
the colour of pale sherry), the plate afterwards to be washed 
thoroughly.” 
The image generally makes its appearance after about two 
minutes, and the deposit gradually increases in intensity until the 
development is finished ; it is then to be well washed and fixed in 
the following solution :— 
