III. Comparative effects of different parts of the spectrum on silver salts

In 1881 I communicated to the Royal Society (“Proc. Roy. Soc.,” vol. 33) the results of a research I had made on the comparative effects of different parts of the spectrum on the haloïd salts of silver, and I pointed out that a mixture of iodide and chloride, and iodide and bromide of silver gave rise to a very curious photographic spectrum, a minimum of action taking place at G, the point where the iodide is mostly affected, two maxima consequently occurring. I also gave some theoretical reasons why this should be. About a year afterwards Herr Schumann, of Leipzic, called in question this result, as applied to bromo-iodide of silver, when the two salts were formed simultaneously,i. e ., when mixtures in water of soluble bromides and iodides were precipitated together by silver nitrate.