_Box Sawdust for Collodion._--The following will be of some use to your
photographic readers:
I find that, by treating box sawdust with nitric and sulphuric acid (in the
same manner as cotton), and then dissolving it in ether, it gives a far
more sensitive collodion than either cotton or paper, and the pictures
produced by it are of unequalled brilliancy.
Can you inform me whether portraits can be taken _for sale_, by the
collodion process, without infringing upon the patents?