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



45. Muriate qfStrontia. 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 dai'kened 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 



