_Colouring Collodion Pictures_ (Vol. vii., p. 388.).--In your impression
of April 16, there is a typographical error of some importance relative
to lifting the collodion in and out of the bath: "The plate, after being
plunged in, should be allowed to repose quietly from twenty to thirty
_minutes_," &c. This should be _seconds_. The error arose, in all {415}
probability, from my having used the contractions 20" to 30".
It may appear somewhat droll for any one to answer a question on which
he has _not_ had experience; but I beg to offer as a _suggestion_ to
PHOTO, that if he wishes to use collodion pictures for the purpose of
dissolving views, he should first copy them in the camera as transparent
objects so as to _reverse_ the light and shade, then varnish them with
DR. DIAMOND'S solution of amber in chloroform, when they will bear the
application of transparent colours ground in varnish, such as are used
for painting magic-lantern slides.