SCIOPTICON MANUAL.
G7
and forefinger, without being visible upon the screen,
as is sometimes the case with the square slide. Then
again, it is easier to place in its proper position (right
side up), having only one chance of error instead of
three.
A DRY PLATE PROCESS FOR LANTERN SLIDES.
TA1TNO-GALLIC PRESERVATIVE.*
In considering the dry process, it is hut proper to
say that a large number of different formules have been
published; in fact, scarcely half a dozen photographers
think alike on thi3 subject. It is, therefore, impossible
to give a formula that will give universal satisfaction.
In preparing this paper for publication, it must be dis¬
tinctly understood that nothing new in the way of pre¬
servative or development is claimed; it is simply one of
the many methods for preparing dry plates that has
given reliable results.
The dry-plate photographer must be prepared for
many and great failures, and bo possessed of the greatest
amount of patience and nicety of manipulation, for other¬
wise time is wasted, and the best process voted a failure.
Commence with reliable chemicals, and follow up the
process with a lavish expenditure of water when wash¬
ing is mentioned, not only on the collodion plate, but
thoroughly rinse the various glasses and dishes, and
particularly the fingers, between each operation. Uso
as little light as possible when making or developing
dry plates, and he careful that the light is yellow.
Probably more dry plates are ruined, and the par¬
ticular process used condemned as worthless; by the use
* I am greatly indebted to my triend, Mr. E. Wallace, Jr., for bis kindness
in furnishing me with the formula, and showing, by his own experiments, the
valuable results to be obtainod from this process. J. C. Browne.