_Caution to Photographers._--About six months since, I procured some gun
cotton from a chemist which appeared very good, being quite soluble, and
the collodion produced by it was excellent. That which I did not use I
placed in what I believed to be a clean dry-stopped bottle, and put the
bottle in a dark cupboard. I was much surprised the other day, upon going
to the cupboard, to find the stopper blown out, and the cotton giving out
dense red fumes of nitrous acid. It appears to me to be almost upon the
point of combustion, and I have, accordingly, placed it under a bell-glass
in a porcelain dish to watch the result. I feel satisfied, however, that
there is some risk, and, as it may often be near ether, spirits of wine, or
other inflammable chemicals, that caution is necessary not only in
preserving it at home, but especially in its transmission abroad, which is
now done to some extent.