8 
After washing, the Photographic image remains behind as a 
pale greenish precipitate, easily transformed into various 
colours, as the following experiments will show : — 
No. 1. (Blue.) Has been steeped in a weak solution of 
nitrate of iron for about ten minutes, and then washed in 
water. 
No. 2 . (Green.) Same as No. 1, but steeped in a weak 
solution of bi-chromate of potash after the nitrate of iron. 
No. 3. (Reddish Brown.) Has been steeped in a solution 
of nitrate of copper, and then washed. 
No. 4. (Brown.) Has been developed by steeping it in a 
mixture of weak solution of nitrate of iron and nitrate of 
copper. 
No. 5. (Dark Brown.) Has also been treated with nitrate 
of iron and nitrate of copper, but. containing a larger pro- 
portion of the former. 
These few experiments will show that a very large number 
of shades may be obtained by using different salts and mix- 
tures thereof in developing the Photograph. A further series 
of colours may be obtained by destroying the blue with 
caustic soda, which, after washing, will leave behind oxides of 
iron and lead, which may be dyed with vegetable colouring 
matters. 
All the above experiments have been made about four 
years ago, which goes to prove that the colours are perma- 
nent. I hope shortly to be able to resume my experiments, 
and work the process out more perfectly. 
Mr. Dancer remarked that he had some prints (which 
were shown to the meeting) produced by Mr. Mercer in 1856, 
which appeared to be done by a process similar to the one 
just described, prussiate of potash being one of the substances 
used, but he was not acquainted with the details of the pro- 
cess. 
It was considered a useful process for certain purposes, and 
deserved more attention than it had hitherto received. 
