270 Mr. Hunt on Light 'which has permeated coloured Media, 



The two papers A and G exhibit much more sensitive- 

 ness to hmiinous influence than any others I have yet tried. 



8. The paper A, when washed with a weak solution of 

 the hydriodate of baryta, gives under the pencil of light a 

 beautiful picture, whether used in the camera or for surface 

 drawings. 



These pictures exhibit the peculiarities mentioned by Mr. 

 Talbot at the British Association*. Sunshine changes " the 

 colour of the object delineated from reddish to black with 

 great rapidity." This gentleman adds, " after which no 

 further change occurs." I much regret I have not been for- 

 tunate enough to succeed thus far in fixing my drawings. 

 The continued influence of light in a few months obliterates 

 the impression. 



A singular change follows the exposures of these pictures 

 to coloured light. 



If placed under vessels containing coloured fluids (4.) and 

 exposed either to sunshine or to diflused light, in a few days 

 the picture becomes a full red under the blue; a rose hue un- 

 der the green; a light blue under the yellow, and a deep blue 

 under the red. These colours after deepening for some time 

 gradually change to diff'erent shades of green under the blue 

 and green fluids, to a j^ink under the yellow, and a red under 

 the red fluid (25.). After this, the colours alter no more, and 

 the picture bears exposure to light much better than at first ; 

 but I doubt if it is rendered perfectly permanent, for the dull 

 light of January and February has spread a downiness, like a 

 mist, over those photographs which have been constantly ex- 

 posed. 



Daguerreotypes. 



9. Exposing a plate, over which some lace was carefully 

 placed, under four coloured glasses (2.) for three minutes to 

 diffused light, I obtained, under the blue glass a beautiful 

 copy ; no trace of a drawing beneath the green ; a tolerable 

 impression beneath the yellow; but the mercury would not 

 attack the space beneath the red. 



10. A plate similarly arranged beneath four bottles of co- 

 loured fluid (4.) exposed to diflused light for fifteen minutes, 

 was found on being acted upon by the mercurial vapour to 

 present the same appearance as above (9.), excepting that a 

 faint design was evident over the space the carmine fluid had 

 covered. 



11. I arranged a dark chamber, to which no other rays 

 could pass but such as had permeated two inches of co- 

 loured fluid. 



* Athengeum, No. 618. 



