collodion, was removed directly from the nitrate-of-silver bath to the
camera, so as to be exposed to its image while still wet. It is obvious
that this process is one that can hardly be performed conveniently at a
distance from the artist's place of work. Solutions of nitrate of silver
are not carried about and decanted into baths and back again into bottles
without tracking their path on persons and things. The _photophobia_ of
the "sensitized" plate, of course, requires a dark apartment of some kind:
commonly a folding tent is made to answer the purpose in photographic
excursions. It becomes, therefore, a serious matter to transport all that
is required to make a negative according to the method described. It has
consequently been a great desideratum to find some way of preparing a
sensitive plate which could be dried and laid away, retaining its
sensitive quality for days or weeks until wanted. The artist would then
have to take with him nothing but his camera and his dry sensitive plates.
After exposing these in the camera, they would be kept in dark boxes until
he was ready to develop them at leisure on returning to his _atelier_.

Many "dry methods" have been contrived, of which the _tannin process_ is
in most favor. The plate, after being "sensitized" and washed, is plunged
in a bath containing ten grains of tannin to an ounce of water. It is then
dried, and may be kept for a long time without losing its sensitive
quality. It is placed dry in the camera, and developed by wetting it and
then pouring over it a mixture of pyrogallic acid and the solution of
nitrate of silver. Amateurs find this the best way for taking scenery, and
produce admirable pictures by it, as we shall mention by-and-by.

* * * * *

In our former articles we have spoken principally of stereoscopic
pictures. These are still our chief favorites for scenery, for