262 Mr. R. Hunt on the Use of Hydriodic Salts 



45. Muriate ofStrontia. — Blue. These are more permanent 

 than any other variety of the hydriodic photographs. Under 

 this influence the shadows are browner than before; the lights 

 scarcely changed. Green. The yellow much increased in 

 depth; the dark parts faded slightly and become very red. 

 Yellow. The lights very little tinged with blue ; the darks 

 without any apparent change. Red. The lights deepened; 

 the shadows a fine black. 



46. Muriate of Baryta. — Blue. The yellow parts are be- 

 come brown ; the dark portions faded and reddened. Green. 

 Lights unchanged ; the dark parts very red. Yellow. Lights 

 unchanged; shadows tinged green, over a very decided black- 

 ening which has taken place. Red. The yellow much height- 

 ened; the dark parts much tinged with green. 



47. Hydrochloric Acid. — Blue. Faded out: lights dark- 

 ened. Green. Faded out; yellow much increased. Yel- 

 low. The lights rendered very yellow; darks unchanged. 

 Red. Yellow become very strong; the shadows are very much 

 blackened. 



48. Hydriodate of Baryta. — Under this head it will only 

 be necessary to name the effects on three kinds of photo- 

 graphs, the others being very similar in all their changes to 

 those just mentioned. 



49. Muriate of Ammonia. — In my paper on the influence 

 of coloured media, vol. xvi. p. 270 of your Journal, I have 

 already mentioned the singular change which ensues upon ex- 

 posing this kind of drawing to light under media such as we 

 are now considering. To that paper I refer you. 



50. Muriate of Baryta. — Blue. Faded in the dark parts, 

 which are become a brick red ; the yellowness of the lights 

 increased. Green. The lights unchanged ; the shadows suf- 

 fused with a pink hue. Yellow. Lights unchanged; sha- 

 dows much darkened and strongly tinged with a light blue. 

 Red. Lights unchanged ; dark parts a deep blue. These sin- 

 gular effects, which, although they are traceable on nearly all 

 those photographs which blacken by after exposure to sun- 

 shine, are much more decided when the salts of baryta in one 

 or other of the processes have been used. I communicated 

 these facts with others to Sir John Herschel, who has paid 

 me a very high compliment by inserting my communication 

 in his valuable memoir " On the Chemical Action of the Solar 

 Spectrum." I the less regret my inability to pursue my obser- 

 vations on the effects of the pure prismatic rays on the hy- 

 driodic preparations, finding that the subject is one which, 

 among others equally curious and important, is engaging the 

 attention of this eminent philosopher. 



51. Muriate of Strontia, — Blue. Lights but very little 



