29 
Ordinary Meeting, December 26th, 1860. 
Dr. R. Angus Smith, Vice-President, in the Chair. 
Ordinary Meeting, January 8th, 1861. 
E. W. Binney, F. R. S., F. G. S., &c., Vice-President, 
in the Chair. 
Mr. Ransome exhibited and explained the means of obtain- 
ing a photograph, which, although appearing a confused series 
of light and shade, yet, when reflected from a polished cylinder, 
was a beautiful picture. 
Dr. Crace Calvert brought under the notice of the 
Society an interesting communication made to him by Pro- 
fessor Arnaudon, of Turin, to the effect that oxalate of 
ammonia completely modifies the action of yellow prussiate of 
potash when mixed in solution with a salt of peroxide of iron. 
Thus, if oxalate of ammonia be added to this metallic salt, it 
will give no prussian blue when a solution of yellow prussiate 
of potash is added ; but on the addition of an acid, prussian 
blue is immediately produced. The knowledge of this fact 
may be interesting to calico printers, as it will give them the 
means of easily producing prussian blue on their fabrics. To 
attain this desirable end, the printer will simply have to pad 
his fabric through a mixture of persalt of iron and oxalate of 
ammonia, dry, and print an acid where he wishes to produce 
the blue. 
After Dr. Calvert had made a few more remarks on this 
subject, he stated that he had lately examined several varieties 
Proceedings — Lit. & Phil. Society— No. 7.— Session, 1860-61. 
